U.S. patent application number 09/170056 was filed with the patent office on 2001-11-29 for image sensing apparatus.
Invention is credited to ONUKI, ICHIRO.
Application Number | 20010045989 09/170056 |
Document ID | / |
Family ID | 26552939 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045989 |
Kind Code |
A1 |
ONUKI, ICHIRO |
November 29, 2001 |
IMAGE SENSING APPARATUS
Abstract
Disclosed is a camera having a focus detection module 130
inserted into or withdrawn from an optical path between an image
sensing optical system (152-155) and a CCD image sensing device
(111). An image pick-up signal from the CCD image sensing device
(111) is used as ordinary image data for recording when the module
(130) is withdrawn from the optical path and as image data for
rangefinding when the module (130) is inserted into the optical
path. The focus detection module (130) is internally provided with
first through fourth mirrors (131, 132, 133, 134), a field lens
(135) provided between the second and third mirrors and secondary
image forming lenses (137) provided between the third and fourth
mirrors, whereby two secondary images are formed on the CCD image
sensing device (111). The two secondary images are used for
rangefinding or focusing.
Inventors: |
ONUKI, ICHIRO;
(KAWASAKI-SHI, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
26552939 |
Appl. No.: |
09/170056 |
Filed: |
October 13, 1998 |
Current U.S.
Class: |
348/345 ;
348/350; 348/E5.045 |
Current CPC
Class: |
G02B 7/28 20130101; H04N
5/232122 20180801; H04N 5/23293 20130101 |
Class at
Publication: |
348/345 ;
348/350 |
International
Class: |
H04N 005/232 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 1997 |
JP |
9-278593 |
Oct 13, 1997 |
JP |
9-278594 |
Claims
What is claimed is:
1. An image sensing apparatus comprising: photoelectric conversion
means for photoelectrically converting an image of an object
obtained through image forming optics; optical path changeover
means provided on an optical path between the image forming optics
and said photoelectric conversion means and movable between first
and second positions for changing over the optical path in such a
manner that a first image of the object is formed on said
photoelectric conversion means when said optical path changeover
means is at the first position and a second image of the object is
formed on said photoelectric conversion means when said optical
path changeover means is at the second position; focus detection
means for detecting state of focus of the image forming optics
using the first image when said optical path changeover means is at
the first position; and image sensing means for picking up the
second image using the photoelectric conversion means when said
optical path changeover means is at the second position.
2. The apparatus according to claim 1, wherein said optical path
changeover means has focus detection optics for forming two
secondary images as the second image of the object from a pair of
light fluxes obtained by passing the image of the object through
different pupil areas; said apparatus further comprising means for
detecting a phase difference between the two secondary images,
which have been formed on said photoelectric conversion means, when
said optical path changeover means is at the first position.
3. The apparatus according to claim 1, wherein said optical path
changeover means includes a first mirror for deflecting an image
forming light flux in a direction different from an image forming
optic axis connecting said image forming optics and said
photoelectric conversion means; and a second mirror for returning
the deflected light flux to the image forming optic axis.
4. The apparatus according to claim 1, wherein said optical path
changeover means includes a beam splitter for splitting an image
forming light flux into light fluxes in first and second directions
at a predetermined ratio of light quantities; said apparatus having
finder means for viewing the image of the object along the second
direction.
5. The apparatus according to claim 1, wherein said optical path
changeover means has lens means for making image forming power of
the image forming optics different at the first and second
positions.
6. The apparatus according to claim 1, further comprising release
operating means, wherein said focus detection means is activated in
response to a first operation of said release operating means, and
said optical path changeover means is switched from the first
position to the second position in response to a second operation
of said release operating means.
7. The apparatus according to claim 1, further comprising display
means for displaying the first image of the object when focus
detection is performed by said focus detection means and the second
image of the object when pick-up is performed by said image sensing
means.
8. The apparatus according to claim 1, further comprising focusing
control means for performing focusing based upon results of focus
detection by said focus detection means.
9. The apparatus according to claim 1, further comprising display
means for selectively displaying the first and second images of the
object; wherein said optical path changeover means has image
magnification changing means for forming the first image on said
photoelectric conversion means at a first magnification at the
first position and forming the second image on said photoelectric
conversion means at a second magnification at the second position,
whereby sizes of the first and second images displayed on said
display means are made substantially the same.
10. The apparatus according to claim 1, wherein said optical path
changeover means forms a plurality of images of the object on said
photoelectric conversion means at the first position and forms a
single image of the object on said photoelectric conversion means
at the second position.
11. The apparatus according to claim 1, said optical path
changeover means forms the first image of the object at a location
displaced from the center of a light-receiving portion of said
photoelectric conversion means at the first position and forms the
second image of the object at the center of the light-receiving
portion of the photoelectric conversion means at the second
position.
12. An image sensing method comprising the steps of:
photoelectrically converting an image of an object, which is
obtained through image forming optics, using photoelectric
conversion means; forming a first image of the object on said
photoelectric conversion means by moving optical path changeover
means, which is movably disposed between the image forming optics
and said photoelectric conversion means, to a first position, and
forming a second image of the object on said photoelectric
conversion means by moving said optical path changeover means to a
second position; detecting state of focus of the image forming
optics using the first image; and picking up the second image.
13. A computer readable storage medium storing a program executable
by a computer, said storage medium storing: program code for a
procedure for converting an image of an object, which is obtained
through image forming optics, using photoelectric conversion means;
program code for a procedure for forming a first image of the
object on said photoelectric conversion means by moving optical
path changeover means, which is movably disposed between the image
forming optics and said photoelectric conversion means, to a first
position, and forming a second image of the object on said
photoelectric conversion means by moving said optical path
changeover means to a second position; program code for a procedure
for detecting state of focus of the image forming optics using the
first image; and program code for a procedure for picking up the
second image.
14. An image sensing apparatus comprising: first optical image
forming means for capturing a light flux from an object and forming
a first image of the object; first photoelectric conversion means
for photoelectrically converting the first image; second optical
image forming means, which is spaced away from said first optical
image forming means by a predetermined baselength, for forming a
second image of the object; second photoelectric conversion means
for photoelectrically converting the second image; and rangefinding
means for sensing distance between said first optical image forming
means and the object based upon outputs from said first and second
photoelectric conversion means.
15. The apparatus according to claim 14, wherein said second
optical image forming means has an image forming power different
from that of said first optical image forming means.
16. The apparatus according to claim 14, further comprising image
signal recording means for recording the output of said first
photoelectric conversion means.
17. The apparatus according to claim 14, wherein said first optical
image forming means includes a zoom lens and said rangefinding
means has image magnification correction means for correcting a
fluctuation in image magnification that accompanies a zooming
operation of said zoom lens.
18. The apparatus according to claim 14, further comprising display
means for displaying the first image.
19. An image sensing apparatus comprising: projection means for
projecting a rangefinding light flux toward an object to form a
rangefinding pattern on the object; optical image forming means,
which is spaced away from said projection means by a predetermined
baselength, for selectively forming the image of the rangefinding
pattern and the image of the object; photoelectric conversion means
for photoelectrically converting the image of the rangefinding
pattern and the image of the object; and rangefinding means for
sensing distance between said optical image forming means and the
object based upon an output from said photoelectric conversion
means when the image of the rangefinding pattern has been received
by said photoelectric conversion means.
20. The apparatus according to claim 19, wherein said optical image
forming means includes a zoom lens and said rangefinding means has
image magnification correction means for correcting a fluctuation
in image magnification that accompanies a zooming operation of said
zoom lens.
21. The apparatus according to claim 19, further comprising image
signal recording means or recording the output of said
photoelectric conversion means when the image of the object has
been received by said photoelectric conversion means.
22. The apparatus according to claim 19, further comprising
wavelength region selecting means, which is interposed between said
optical image forming means and said photoelectric conversion
means, for passing a first wavelength region when the image of the
rangefinding pattern is photoelectrically converted and passing a
second wavelength region when the image of the object is
photoelectrically converted.
23. The apparatus according to claim 14, further comprising:
focusing means for focusing said first optical image forming means
based upon an output of said rangefinding means; focal shift
discrimination means for discriminating state of focus of the image
of the object based upon outputs from said rangefinding means and
said focusing means; image signal combining means for combining
outputs from said first and second photoelectric conversion means;
display means for displaying an output image from said image signal
combining means; and combining control means for changing operation
of said image signal combining means based upon an output from said
focal shift discrimination means.
24. The apparatus according to claim 23, wherein said combining
control means varies relative amount of offset between display
positions, on said display means, of outputs from said first and
second photoelectric conversion means in dependence upon a focal
shift signal output by said focal shift discriminating means.
25. An image sensing apparatus comprising: optical image forming
means for capturing a light flux from an object and forming an
image of the object; photoelectric conversion means for
photoelectrically converting the image of the object; rangefinding
means for sensing distance between said optical image forming means
and the object; focusing means for focusing said image forming
optical means based upon an output from said rangefinding means;
display means for displaying the image of the object from said
photoelectric conversion means; focal shift discrimination means
for discriminating state of focus of the image of the object based
upon outputs from said rangefinding means and said focusing means;
and display control means for varying form of display of the image
of the object on said display means based upon an output from said
focal shift discrimination means.
26. The apparatus according to claim 25, wherein said display means
has first and second display areas, and said display control means
varies position of a displayed image in the second display area
relative to a displayed image in the first display area in
dependence upon a focal shift signal from said focal shift
discrimination means.
27. The apparatus according to claim 25, wherein said focal shift
discrimination means detects amount of focal shift from outputs
from said rangefinding means and said focusing means.
28. An image sensing method comprising the steps of: capturing a
light flux from an object via first optical image forming means and
forming a first image of the object; photoelectrically converting
the first image using first photoelectric conversion means; forming
a second image of the object via second optical image forming
means, which is spaced away from said first optical image forming
means by a predetermined baselength; photoelectrically converting
the second image using second photoelectric conversion means; and
measuring distance between said first optical image forming means
and the object based upon outputs from said first and second
photoelectric conversion means.
29. An image sensing method comprising the steps of: projecting a
rangefinding light flux toward an object using projection means to
form a rangefinding pattern on the object; selectively forming the
image of the rangefinding pattern and the image of the object via
optical image forming means spaced away from said projection means
by a predetermined baselength; photoelectrically converting the
image of the rangefinding pattern and the image of the object using
photoelectric conversion means; and measuring distance between said
optical image forming means and the object based upon an output
from said photoelectric conversion means when the image of the
rangefinding pattern has been received by said photoelectric
conversion means.
30. An image sensing method comprising the steps of: capturing a
light flux from an object via optical image forming means and
forming an image of the object; photoelectrically converting the
image of the object using photoelectric conversion means; measuring
distance between said optical image forming means and the object;
focusing said image forming optical means based upon the distance
measured; displaying the image of the object from said
photoelectric conversion means; discriminating focal shift of the
image of the object based upon an output of measured distance and
an output of focusing; and varying form of the display based upon
the focal shift.
31. A computer readable storage medium storing a program executable
by a computer, said storage medium storing: program code for
capturing a light flux from an object via first optical image
forming means and forming a first image of the object; program code
for photoelectrically converting the first image using first
photoelectric conversion means; program code for forming a second
image of the object via second optical image forming means, which
is spaced away from said first optical image forming means by a
predetermined baselength; program code for photoelectrically
converting the second image using second photoelectric conversion
means; and program code for measuring distance between said first
optical image forming means and the object based upon outputs from
said first and second photoelectric conversion means.
32. A computer readable storage medium storing a program executable
by a computer, said storage medium storing: program code for
projecting a rangefinding light flux toward an object using
projection means to form a rangefinding pattern on the object;
program code for selectively forming the image of the rangefinding
pattern and the image of the object via optical image forming means
spaced away from said projection means by a predetermined
baselength; program code for photoelectrically converting the image
of the rangefinding pattern and the image of the object using
photoelectric conversion means; and program code for measuring
distance between said optical image forming means and the object
based upon an output from said photoelectric conversion means when
the image of the rangefinding pattern has been received by said
photoelectric conversion means.
33. A computer readable storage medium storing a program executable
by a computer, said storage medium storing: program code for
capturing a light flux from an object via optical image forming
means and forming an image of the object; photoelectrically
converting the image of the object using photoelectric conversion
means; program code for measuring distance between said optical
image forming means and the object; program code for focusing said
image forming optical means based upon the distance measured;
program code for displaying the image of the object from said
photoelectric conversion means; program code for discriminating
focal shift of the image of the object based upon an output of
measured distance and an output of focusing; and program code for
varying form of the display based upon the focal shift.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to an image sensing apparatus having
an automatic focusing function for focusing the image of a
subject.
[0002] So-called digital still cameras photoelectrically convert
the image of an object, which has been formed by an image sensing
optical system, as a still image using an image sensing device, and
record the converted image in a memory or the like. Focus detection
devices for automatic focusing used in such digital still cameras
usually rely upon one of the following four methods:
[0003] (1) TTL (Through The Lens) secondary image forming
phase-difference detection: Optical images that have been formed by
passage through different pupil areas of an image sensing optical
system are formed again as a pair of secondary images on a focus
detection lens via a secondary image forming optical system and the
state of focus of the image sensing optical system is detected from
the spacing between the two secondary images.
[0004] (2) Passive triangulation: Two images of an object are
formed on a focus detection sensor by two of optical systems spaced
apart by a predetermined baselength, and absolute distance to the
object is sensed from the spacing between the two images
formed.
[0005] (3) Active triangulation: A rangefinding pattern formed on
an object by a light projection system is received by
light-receiving systems spaced apart by a predetermined baselength,
and absolute distance to the object is sensed based upon outputs
from the light-receiving systems.
[0006] (4) Hill-climbing sharpness detection: Part of an image
sensing optical system, or the image sensing device, is oscillated
minutely along the direction of the optic axis and the state of
focus of the image sensing optical system is detected from the
degree of fluctuation of high-frequency components (which are in
synchronization with the oscillation) of the object image formed on
the image sensing device.
[0007] The following finders are used as monitors for verifying the
photographic area of the above-mentioned digital still cameras:
[0008] (a) an optical TTL finder, which allows the photographer to
view the image of the object formed by the image sensing optical
system;
[0009] (b) an optical rangefinder, which allows the photographer to
view an image formed by a finder optical system that is different
from the image sensing optical system; and
[0010] (c) a photoelectric finder whereby an output obtained by
photoelectrically converting the image of an object is displayed on
a monitor such as an a liquid crystal display.
[0011] The prior art described has a number of shortcomings, which
will now be set forth.
[0012] The secondary image forming phase-difference detection
method and the passive triangulation method require the use of a
photoelectric converting sensor for focus detection in addition to
the image sensing device for acquisition of the photographic image.
This raises the cost of the focus detection mechanism and increases
the size of the image sensing device.
[0013] With the passive triangulation method and active
triangulation method, the focal length and baselength of the
rangefinding optical system cannot be made very large. As a result,
it is required that the dimensional precision of the component
parts be very high in order to assure measurement accuracy.
[0014] The active triangulation method, besides having the drawback
set forth above, requires a special-purpose light receiving device
for receiving projected light. This raises the cost of the focus
detection mechanism.
[0015] With the hill-climbing sharpness detection method, the
in-focus position cannot be detected instantaneously when the
object is greatly out of focus. Though this is not a major obstacle
in a movie camera, it does make a digital still camera difficult to
use and can result in lost photo opportunities.
[0016] The conventional finders have the following drawbacks:
[0017] The optical TTL finder requires a mechanism such as
quick-return mirror or half-mirror for separating and switching
between a photographic light flux and a finder light flux. This
results in an apparatus of large size.
[0018] The optical rangefinder uses a double-image coincidence
mechanism in order to display the state of focusing. The result is
a complex, costly structure.
[0019] The photoelectric finder displays images at a low resolution
and makes it difficult to confirm state of focusing accurately.
SUMMARY OF THE INVENTION
[0020] Accordingly, an object of the present invention is to
provide an image sensing apparatus that is capable of performing
autofocusing highly accurately through a simple structure.
[0021] According to the present invention, the foregoing object is
attained by providing an image sensing apparatus comprising
photoelectric conversion means for photoelectrically converting an
image of an object obtained through image forming optics; optical
path changeover means provided on an optical path between the image
forming optics and the photoelectric conversion means and movable
between first and second positions for changing over the optical
path in such a manner that a first image of the object is formed on
the photoelectric conversion means when the optical path changeover
means is at the first position and a second image of the object is
formed on the photoelectric conversion means when the optical path
changeover means is at the second position; focus detection means
for detecting state of focus of the image forming optics using the
first image when the optical path changeover means is at the first
position; and image sensing means for picking up the second image
using the photoelectric conversion means when the optical path
changeover means is at the second position.
[0022] In accordance with this image sensing apparatus, focus
detection and image pick-up can be performed by a single
photoelectric conversion means. As a result, it is unnecessary to
separately provide costly photoelectric conversion means for focus
detection, thus making it possible to provide a small-size,
inexpensive image sensing apparatus. In addition, a low-resolution
image for focusing and a high-quality image for photography can be
obtained using the same image forming optical system. Specifically,
the apparatus utilizes an image forming optical system for image
pick-up and the photoelectric conversion means thereof effectively
to make possible rangefinding by TTL secondary image
phase-difference detection or passive triangulation. As a result,
it is unnecessary to separately provide costly photoelectric
conversion means for focus detection, thus making it possible to
provide a small-size, inexpensive image sensing apparatus capable
of highly accurate rangefinding through a simple structure.
[0023] According to a preferred aspect of the present invention,
the optical path changeover means of the image sensing apparatus
has focus detection optics for forming two secondary images as the
second image of the object from a pair of light fluxes obtained by
passing the image of the object through different pupil areas; the
apparatus further comprising means for detecting a phase difference
between the two secondary images, which have been formed on the
photoelectric conversion means, when the optical path changeover
means is at the first position.
[0024] As a result, the state of focus of the image forming optical
system is detected by TTL secondary image forming phase-difference
detection. This makes it possible to perform accurate detection of
focusing in a short period of time even in a case where the object
is greatly out of focus.
[0025] According to a preferred aspect of the present invention,
the optical path changeover means of the image sensing apparatus
includes: a first mirror for deflecting an image forming light flux
in a direction different from an image forming optic axis
connecting the image forming optics and the photoelectric
conversion means; and a second mirror for returning the deflected
light flux to the image forming optic axis
[0026] As a result, a focus detection optical system having a
prescribed optical path can be accommodated in a small space, thus
making it possible to reduce the size of the image sensing
apparatus.
[0027] According to a preferred aspect of the present invention,
the optical path changeover means of the image sensing apparatus
includes a beam splitter for splitting an image forming light flux
into light fluxes in first and second directions at a predetermined
ratio of light quantities; the apparatus having finder means for
viewing the image of the object along the second direction.
[0028] The photographic area of the field and the state of focus of
the object can be confirmed visually in accurate fashion by a TTL
optical finder. This makes it possible to prevent failures when
taking pictures.
[0029] According to a preferred aspect of the present invention,
the optical path changeover means of the image sensing apparatus
has lens means for making image forming power of the image forming
optics different at the first and second positions.
[0030] As a result, a focus detection optical system having a
prescribed optical path can be accommodated in a small space, thus
making it possible to reduce the size of the image sensing
apparatus and to obtain a wide range of focus detection.
[0031] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises release operating
means, wherein the focus detection means is activated in response
to a first operation of the release operating means, and the
optical path changeover means is switched from the first position
to the second position in response to a second operation of the
release operating means.
[0032] As a result, the transition from a focus detection operation
to an image pick-up operation can be achieved quickly, thereby
making it possible to perform focusing and image pick-up operations
in a short period of time and to prevent the loss of photo
opportunities.
[0033] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises display means for
displaying the first image of the object when focus detection is
performed by the focus detection means and the second image of the
object when pick-up is performed by the image sensing means.
[0034] As a result, the state of focus of an object undergoing
focus detection and the image of the object at the time of image
pick-up can be confirmed visually in the form of an electronic
image even if there is no optical finder provided. This makes it
possible to prevent failures when taking pictures.
[0035] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises focusing control
means for performing focusing based upon results of focus detection
by the focus detection means.
[0036] As a result, TTL focus detection is performed with a coarse
image projected before image pick-up, and automatic focusing is
carried out highly accurately in a short period based upon the
result, thereby making it possible to focus the image of the
object. A high-definition, focused image can subsequently be
acquired.
[0037] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises display means for
selectively displaying the first and second images of the object;
wherein the optical path changeover means has image magnification
changing means for forming the first image on the photoelectric
conversion means at a first magnification at the first position and
forming the second image on the photoelectric conversion means at a
second magnification at the second position, whereby sizes of the
first and second images displayed on the display means are made
substantially the same.
[0038] In accordance with this arrangement, the normal image of an
object and the reduced image of the object obtained by projection
can be displayed with their sizes equalized in regard to the same
subject imaged at different optical characteristics. This improves
the ability to visually confirm an image of reduced size.
[0039] According to a preferred aspect of the present invention,
the optical path changeover means of the image sensing apparatus
forms a plurality of images of the object on the photoelectric
conversion means at the first position and forms a single image of
the object on the photoelectric conversion means at the second
position.
[0040] In accordance with this arrangement, both an image for focus
detection and an image for photography can be obtained through a
simple structure by a single image sensing means.
[0041] According to a preferred aspect of the present invention,
the optical path changeover means of the image sensing apparatus
forms the first image of the object at a location displaced from
the center of a light-receiving portion of the photoelectric
conversion means at the first position and forms the second image
of the object at the center of the light-receiving portion of the
photoelectric conversion means at the second position.
[0042] In accordance with this arrangement, only a small image
signal that has been formed on part of the light-receiving area of
photoelectric conversion means is read out in a short period of
time to acquire the first image of the object, and the entire image
signal of the light-receiving area of the photoelectric conversion
means is read out to acquire the second image of the subject.
[0043] According to a preferred aspect of the present invention,
the second optical image forming means of the image sensing
apparatus has an image forming power different from that of the
first optical image forming means.
[0044] As a result, rangefinding based upon passive triangulation
can be carried out.
[0045] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises image signal
recording means for recording the output of the first photoelectric
conversion means.
[0046] As a result, an image obtained from an image forming optical
system for photography and an image obtained from the photoelectric
conversion means thereof can be recorded and preserved.
[0047] According to a preferred aspect of the present invention,
the first optical image forming means of the image sensing
apparatus includes a zoom lens and the rangefinding means has image
magnification correction means for correcting a fluctuation in
image magnification that accompanies a zooming operation of the
zoom lens.
[0048] This arrangement is such that when the image forming optical
means for image pick-up is used for rangefinding, a parameter
correction conforming to power fluctuation is carried out to
perform a rangefinding calculation. This makes it possible to
perform accurate rangefinding at all times even when power
fluctuates.
[0049] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises display means for
displaying the first image.
[0050] In accordance with this arrangement, the image of a subject
for image pick-up is displayed for monitoring. As a result, the
state of subject focus can be checked and it is possible to prevent
the taking of a photograph that is out of focus.
[0051] An image sensing apparatus according to a preferred aspect
of the present invention comprises projection means for projecting
rangefinding a light flux toward an object to form a rangefinding
pattern on the object; optical image forming means, which is spaced
away from the projection means by a predetermined baselength, for
selectively forming the image of the rangefinding pattern and the
image of the object; photoelectric conversion means for
photoelectrically converting the image of the rangefinding pattern
and the image of the object; and rangefinding means for sensing
distance between the optical image forming means and the object
based upon an output from the photoelectric conversion means when
the image of the rangefinding pattern has been received by the
photoelectric conversion means.
[0052] In accordance with this arrangement, both a projection
pattern for rangefinding in active triangulation and an image of
the object can be acquired by a single image sensing system, as a
result of which the apparatus can be reduced in size and lowered in
cost.
[0053] According to a preferred aspect of the present invention,
the optical image forming means of the image sensing apparatus
includes a zoom lens and the rangefinding means has image
magnification correction means for correcting a fluctuation in
image magnification that accompanies a zooming operation of the
zoom lens.
[0054] In accordance with this arrangement, when the optical image
forming means for image pick-up is used for rangefinding, a
parameter correction conforming to power fluctuation is carried out
to perform a rangefinding calculation. This makes it possible to
perform accurate rangefinding at all times even when power
fluctuates.
[0055] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises image signal
recording means for recording the output of the photoelectric
conversion means when the image of the subject has been received by
the photoelectric conversion means.
[0056] As a result, an image obtained from an image forming optical
system for image pick-up and an image obtained from the
photoelectric conversion means thereof can be recorded and
preserved.
[0057] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises wavelength region
selecting means, which is interposed between the optical image
forming means and the photoelectric conversion means, for passing a
first wavelength region when the image of the rangefinding pattern
is photoelectrically converted and passing a second wavelength
region when the image of the object is photoelectrically
converted.
[0058] In accordance with this arrangement, a wavelength selection
suited to acquisition of a pattern image for rangefinding is
performed at the time of rangefinding and a wavelength selection
suited to acquisition of the image of the object at the time of
image pick-up. As a result, highly accurate rangefinding can be
performed and it is possible to obtain a highly precise image that
is free of unnecessary light rays.
[0059] According to a preferred aspect of the present invention,
the image sensing apparatus further comprises focusing means for
focusing the first optical image forming means based upon an output
of the rangefinding means; focal shift discrimination means for
discriminating state of focus of the image of the object based upon
outputs from the rangefinding means and the focusing means; image
signal combining means for combining outputs from the first and
second photoelectric conversion means; display means for displaying
an output image from the image signal combining means; and
combining control means for changing operation of the image signal
combining means based upon an output from the focal shift
discrimination means.
[0060] In accordance with this arrangement, the extent to which the
image of an object is out of focus can be checked visually and
clearly by images combined and displayed. This makes it possible to
prevent the taking of a photograph that is out of focus.
[0061] According to a preferred aspect of the present invention,
the combining control means of the image sensing apparatus varies
relative amount of offset between display positions, on the display
means, of outputs from the first and second photoelectric
conversion means in dependence upon a focal shift signal output by
the focal shift discriminating means.
[0062] In accordance with this arrangement, the amount of focal
shift of the image of an object can be checked visually and clearly
from the amount of relative offset between two images displayed in
superposition. This makes it possible to prevent the taking of a
photograph that is out of focus.
[0063] An image sensing apparatus according to a preferred aspect
of the present invention comprises optical image forming means for
capturing a light flux from an object and forming an image of the
object; photoelectric conversion means for photoelectrically
converting the image of the object; rangefinding means for sensing
distance between the optical image forming means and the object;
focusing means for focusing the image forming optical means based
upon an output from the rangefinding means; display means for
displaying the image of the object from the photoelectric
conversion means; focal shift discrimination means for
discriminating state of focus of the image of the object based upon
outputs from the rangefinding means and the focusing means; and
display control means for varying form of display of the image of
the object on the display means based upon an output from the focal
shift discrimination means.
[0064] In accordance with this arrangement, the amount of focal
shift of the image of an object can be checked visually and clearly
based upon images combined and displayed. This makes it possible to
prevent the taking of a photograph that is out of focus.
[0065] According to a preferred aspect of the present invention,
the display means of the image sensing apparatus has first and
second display areas, and the display control means varies position
of a displayed image in the second display area relative to a
displayed image in the first display area in dependence upon a
focal shift signal from the focal shift discrimination means.
[0066] In accordance with this arrangement, the amount of focal
shift of the image of an object can be checked visually and clearly
from the amount of relative offset between two images displayed in
superposition. This makes it possible to prevent the taking of a
photograph that is out of focus.
[0067] According to a preferred aspect of the present invention,
the focal shift discrimination means of the image sensing apparatus
detects amount of focal shift from outputs from the rangefinding
means and the focusing means.
[0068] As a result, a finder display or the like can be presented
using information relating to the amount of focal shift sensed.
This makes it possible to prevent the taking of a photograph that
is out of focus.
[0069] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0070] FIG. 1 is a block diagram illustrating the construction of
an image sensing apparatus according to a first embodiment of the
present invention, this diagram showing the apparatus at the time
of focus detection;
[0071] FIG. 2 is a diagram showing formation of images of an object
when the object is in focus at the time of focus detection
according to the first embodiment;
[0072] FIG. 3 is a diagram showing formation of the images of an
object when the object is not in focus at the time of focus
detection according to the first embodiment;
[0073] FIG. 4 is a diagram showing the image sensing apparatus at
the time of image pick-up according to the first embodiment;
[0074] FIG. 5 is a diagram showing formation of the image of an
object at the time of image pick-up according to the first
embodiment;
[0075] FIG. 6 is a flowchart showing a procedure for controlling a
camera according to the first embodiment;
[0076] FIG. 7 is a flowchart showing a procedure for controlling a
lens according to the first embodiment;
[0077] FIG. 8 is a diagram illustrating part of a focus detection
optical system according to a second embodiment of the present
invention;
[0078] FIG. 9 is a diagram showing formation of the images of an
object when the object is in focus at the time of focus detection
according to the second embodiment;
[0079] FIG. 10 is a diagram illustrating part of a focus detection
optical system according to a third embodiment of the present
invention;
[0080] FIG. 11 is a diagram showing formation of the images of an
object when the object is in focus at the time of focus detection
according to the third embodiment;
[0081] FIG. 12 is a block diagram illustrating the construction of
an image sensing apparatus according to a fourth embodiment of the
present invention, this diagram showing the apparatus at the time
of focus detection;
[0082] FIG. 13 is a diagram showing formation of the images of an
object when the object is in focus at the time of focus detection
according to the fourth embodiment;
[0083] FIG. 14 is a diagram useful in describing the state of a
display on a display unit at the time of focus detection according
to the fourth embodiment;
[0084] FIG. 15 is a diagram showing the image sensing apparatus at
the time of image pick-up according to the fourth embodiment;
[0085] FIG. 16 is a diagram showing formation of the image of an
object at the time of image pick-up according to the fourth
embodiment;
[0086] FIG. 17 is a flowchart showing a procedure for controlling a
camera according to the fourth embodiment;
[0087] FIG. 18 is a block diagram illustrating the construction of
an image sensing apparatus according to a fifth embodiment of the
present invention, this diagram showing the apparatus at the time
of focus detection;
[0088] FIG. 19 is a diagram showing the construction of an image
sensing apparatus at the time of image pick-up according to the
fifth embodiment;
[0089] FIG. 20 is a block diagram illustrating the construction of
an image sensing apparatus according to a sixth embodiment of the
present invention;
[0090] FIGS. 21A, 21B are diagrams useful in describing the state
of image formation when rangefinding is performed according to the
sixth embodiment;
[0091] FIGS. 22A, 22B are diagrams useful in describing the
principle of image magnification correction according to the sixth
embodiment;
[0092] FIG. 23 is a diagram useful in describing the concept of an
image signal when a rangefinding calculation is performed according
to the sixth embodiment;
[0093] FIG. 24 is a flowchart showing a procedure for controlling
an image sensing apparatus according to the sixth embodiment;
[0094] FIG. 25 is a diagram showing the construction of an image
sensing apparatus at the time of rangefinding according to the
seventh embodiment;
[0095] FIG. 26 is a diagram useful in describing the state of
formation of a spot image for rangefinding according to the seventh
embodiment;
[0096] FIG. 27 is a diagram useful in describing the concept of an
image signal when a rangefinding calculation is performed according
to the seventh embodiment;
[0097] FIG. 28 is a diagram showing the construction of an image
sensing apparatus at the time of image pick-up according to the
seventh embodiment;
[0098] FIGS. 29 is a diagram useful in describing the state of
image formation when image pick-up is performed according to the
seventh embodiment;
[0099] FIG. 30 is a diagram useful in describing the state of an
image display after image pick-up according to the seventh
embodiment;
[0100] FIG. 31 is a flowchart showing a procedure for controlling
an image sensing apparatus according to the seventh embodiment;
[0101] FIG. 32 is a block diagram illustrating the construction of
an image sensing apparatus according to an eighth embodiment of the
present invention;
[0102] FIG. 33 is a diagram useful in describing the concept of an
image signal when a rangefinding calculation is performed according
to the eighth embodiment;
[0103] FIG. 34 is a diagram useful in describing the state of an
image display when rangefinding is performed according to the
eighth embodiment;
[0104] FIG. 35 is a flowchart showing a procedure for controlling
an image sensing apparatus according to the eighth embodiment;
[0105] FIG. 36 is a block diagram illustrating the construction of
an image sensing apparatus according to a ninth embodiment of the
present invention;
[0106] FIG. 37 is a diagram useful in describing the state of image
formation when rangefinding is performed according to the ninth
embodiment;
[0107] FIG. 38 is a diagram useful in describing the state of an
image display when rangefinding is performed according to the ninth
embodiment; and
[0108] FIG. 39 is a flowchart showing a procedure for controlling
an image sensing apparatus according to the ninth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0109] Embodiments of the present invention will now be described
with reference to the drawings.
First Embodiment
[0110] FIGS. 1 through 7 are diagrams relating to a first
embodiment of the present invention.
[0111] FIG. 1 is a block diagram showing the construction of an
image sensing apparatus according to a first embodiment. This
embodiment relates to a so-called single-lens reflex camera in
which an interchangeable lens having an image sensing optical
system is capable of being removably mounted on a camera body
having a image sensing device.
[0112] The camera includes a camera body 101 having a mount (not
shown) joining various functional portions for image pick-up and an
interchangeable lens 151, described later. An object is indicated
at OBJ.
[0113] The camera is internally provided with a single-chip
microcomputer 102 having a ROM, a RAM and A/D, D/A conversion
functions. In accordance with a camera sequence program stored in
the ROM, the microcomputer 102 implements a series of camera
operations such as automatic exposure control (AE), autofocus (AF)
and image sensing. The microcomputer 102 controls various circuits
and lens operation by communicating with peripheral circuitry
within the lens body 101 and with the interchangeable lens 151.
According to the present invention, the ROM constitutes a storage
medium and can be a semiconductor memory, an optical disk, a
magneto-optic device or a magnetic medium, etc.
[0114] The mount joining the camera body 101 and the
interchangeable lens 151 is prided with four connection terminals.
A power supply 103 supplies the camera circuits and actuators with
power-supply voltage and supplies the interchangeable lens 151 with
power via a line Vcc.
[0115] A line DCL transmits a signal from the microcomputer 102 to
a microcomputer 161 (described later) inside the lens. A line DLC
transmits a signal from the microcomputer 161 inside the lens to
the microcomputer 102 inside the camera body. The camera body 101
controls the interchangeable lens 151 via these two lines. The
camera body 101 and interchangeable lens 151 are connected to
ground via a line GND.
[0116] The camera body 101 has a display unit 104, such as a liquid
crystal panel, having a display function for displaying
photographic conditions and a monitor function for monitoring a
sensed image.
[0117] A driver 105 drives and controls an image sensing device
111, described later. The driver 105 controls the storage of charge
in the image sensing device 111, charge transfer, CDS (Correlated
Double Sampling), AGC (Automatic Gain Control), A/D conversion,
gamma correction and AWB (Automatic White Balance), etc.
[0118] A memory 106 records and preserves image signal data
representing a sensed image and can be a semiconductor memory,
magnetic disk or optical disk, etc.
[0119] A terminal 107 for outputting a recorded image to external
equipment is connected to a personal computer or printer.
[0120] The image sensing device 111, such as a CCD, is a
two-dimensional photoelectric sensor for photoelectrically
converting the image of the object formed by an image sensing
optical system 152-154.
[0121] The camera body has a main switch 120. When this switch is
turned on (closed), the microcomputer 102 allows the execution of a
prescribed program relating to preparations for photography, namely
exposure metering and focus detection, etc.
[0122] Switches 121 (SW1) and 122 (SW2) are linked to a camera
release button and are turned on (closed) by pressing the release
button through first and second stroke lengths, respectively. More
specifically, the switch 121 is for preparing for image pick-up.
When this switch is turned on, preparatory photographic operations
such as exposure metering, focus detection and focusing are
executed. The switch 122 is a photography switch. When this switch
is turned on, a photographic image that has been formed on the
image sensing device 111 is acquired and recorded in the image
memory 106.
[0123] An AF mode switch 123 is used to select the autofocus mode.
A display switch 124 is used to designate a display for monitoring
a photographic image.
[0124] The image of the object formed by the image sensing optical
system is formed again by a focus detection module 130 using the
various optical elements set forth below. Specifically, the focus
detection module 130 includes a first mirror 131 for fully
reflecting the photographic light flux upward in FIG. 1; a
semi-transparent second mirror 132 for passing about 70% of the
fully reflected light flux and reflecting the remaining 30% of the
light flux rightward in FIG. 1; a third mirror 133 for fully
reflecting the light flux downward in FIG. 1; and a fourth mirror
134 for fully reflecting the fully reflected light flux rightward
in FIG. 1; a field lens 135 placed in a first predetermined focal
plane of the image sensing optical system, with a primary image IM1
of the object OBJ being formed in this predetermined focal plane by
the image sensing optical system; a field mask 136 which decides a
focus detection area; and a pair of secondary image forming lenses
137 for forming the images of the primary image IM1 again.
[0125] The entrance pupil of the pair of secondary image forming
lenses 137 and the exit pupil of a stop 155, described later, are
placed in a projection relationship by the field lens 135.
Consequently, two secondary images IMA and IMB resulting from the
light flux that has passed through different pupil areas (the exit
pupil of the stop 155 and the entrance pupil of the pair of
secondary image forming lenses 137) of the image sensing optical
system are formed on the image sensing device 111.
[0126] A movable mirror unit 138 is capable of moving the first
mirror 131, fourth mirror 134 and secondary image forming lenses
137 in unison to advance and retract the same into and out of the
photographic light flux.
[0127] A quick-return (QR) actuator 139 drives the movable mirror
unit 138 to advance and retract the same.
[0128] A focusing screen 141 is placed in a second predetermined
focal plane that is in a conjugate relationship with the first
predetermined focal plane mentioned above. A secondary primary
image IM2 resulting from light flux reflected by the first mirror
131 and passed by the second mirror 132 is formed on the focusing
screen 141.
[0129] A pentagonal prism 142 and an eyepiece 143 construct an
optical finder that makes it possible for the photographer to view
the secondary primary image IM2.
[0130] The components on the side of the lens will now be
described.
[0131] The interchangeable lens 151 is capable of being removably
mounted on the camera body 101 and includes a focusing lens group
152 for performing focusing by being advanced and retracted along
the direction of the optic axis; a zoom lens group 153 for
performing zooming by being advanced and retracted along the
direction of the optic axis; and a relay lens group 154 for
performing a prescribed image forming operation together with the
lens groups 152 and 153. The lens groups 152, 153 and 154 together
construct the image sensing optical system.
[0132] The stop 155 decides the entrant light flux of the image
sensing optical system, and an actuator 156 drives the stop
155.
[0133] Like the microcomputer 102, the microcomputer 161 inside the
lens is a single-chip microcomputer having a ROM, a RAM and A/D,
D/A conversion functions. In accordance with an instruction sent
from the microcomputer 102 via the signal line DCL, the
microcomputer 161 controls the driving of a focus actuator and zoom
actuator, described later, as well as the driving of the actuator
mentioned above. Various operating states of the lens and
parameters specific to the lens are transmitted to the
microcomputer 102 by the signal line DLC.
[0134] A focus actuator 162 drives the focusing lens group 152 to
advance and retract the same, and a focus encoder 163 senses
position information indicative of the position of the focusing
lens group 152, namely object distance information. A zoom actuator
164 drives the zoom lens group 153 to advance and retract the same,
and a zoom encoder 165 senses position information indicative of
the position of the zoom lens group 153, namely focal length
information.
Principles . . . First Embodiment
[0135] By virtue of the construction described above, the
interchangeable lens 151 forms the image of the object OBJ on the
image sensing device 111 of the camera and performs focusing,
zooming and control of entrant light quantity based upon a control
instruction from the camera.
[0136] The state of image formation of the object OBJ at the time
of focus detection prior to preparations for photography will now
be described.
[0137] A light flux from the object OBJ passes through the lens
groups 152, 153, 154 and stop 155 constructing the image sensing
optical system and is reflected by the first and second mirrors
131, 132, respectively, to form the first primary image IM1 on a
first image forming plane. The light flux is then reflected by the
third mirror 133, after which the light flux impinges upon the two
secondary image forming lenses 137. Each of the lenses 137 function
as pupil. Thus, the lenses 137 form two images by pupil-splitting
or -separating (referred to as simply "splitting", hereinafter). In
other words, two light fluxes are obtained and these are reflected
by the fourth mirror 134, after which the reflected light fluxes
are projected onto the light-receiving surface of the image sensing
device 111 as the two secondary images IMA and IMB.
[0138] FIG. 2 is a diagram showing the state of image formation of
the secondary images IMA, IMB on the image sensing device 111.
[0139] A light-receiving portion 112 of the image sensing device
111 has m.times.n light-receiving pixels and a charge transfer
portion (CCD.sub.V for vertical transfer, not shown) for
transferring electric charge that has accumulated in these pixels.
A horizontal transfer portion (CCD.sub.H) 113 stores electric
charge transferred in the direction of arrow TRV by the vertical
transfer portion CCD.sub.V in the light-receiving portion 112, then
transfers the charge in the direction of arrow TRH and outputs an
image signal from a signal output portion 114 to the image sensor
driver 105.
[0140] Two areas ARA, ARB on the light-receiving portion 112 are
images of the field mask 136 projected by the secondary image
forming lenses 137 of FIG. 1. The secondary images IMA, IMB of the
first primary image IM1 are formed in the areas ARA, ARB,
respectively. Let V.sub.0 represent the spacing between the two
images IMA, IMB when the image sensing optical system is in focus
with respect to the object OBJ.
[0141] FIG. 3 is a diagram showing the state of image formation of
the secondary images on the image sensing device 111 when the image
sensing optical system is not in focus with respect to the object
OBJ. In this case the spacing between the two images IMA and IMB is
V.sub.1 (.noteq.V.sub.0).
[0142] When the switch 121 which prepares the camera body 101 for
photography is closed, stored electric charge in the
light-receiving portion 112 is read out, converted from an analog
to a digital value and transmitted to the microcomputer 102. In
accordance with a well-known correlation algorithm, the spacing
V.sub.1 between the two above-mentioned images is calculated and
the difference between V.sub.1 and the in-focus spacing V.sub.0
i.e.,
.DELTA.v=V.sub.1--V.sub.0
[0143] is obtained, thereby making it possible to detect the extent
to which the object OBJ is out of focus. The amount of such defocus
is transmitted to the interchangeable lens 151 and the focusing
lens group 152 is driven accordingly to perform an autofocus
operation.
[0144] FIG. 4 is a diagram showing the camera when the photography
switch 122 of the camera body 101 is closed upon the completion of
the autofocus operation, thereby establishing the photographic
state.
[0145] When the photography switch 122 is closed, the movable
mirror unit 138 is withdrawn away from the optical path of
photography (i.e., upward in FIG. 4) by the quick-return actuator
139. When this is done, the mirrors are removed from between the
image sensing optical system and image sensing device 111 so that a
primary image IM3 produced by the image sensing optical system is
formed on the image sensing device 111.
[0146] FIG. 5 is a diagram showing formation of the image of the
object on the image sensing device 111 at the time of photography.
Here the primary image IM3 of the object OBJ is projected onto the
light-receiving portion 112. Accordingly, the image signal
prevailing under these conditions is accepted and recorded in the
image memory 106 of the camera body 101, whereby the image is
sensed.
Control Procedure . . . First Embodiment
[0147] FIGS. 6 and 7 are flowcharts illustrating the control flows
of the microcomputers 102, 161 when focus detection, focusing and
photography are performed by the camera body 101 and
interchangeable lens 151 according to the first embodiment of the
present invention.
[0148] The control flow of the microcomputer 102 inside the camera
will be described first in accordance with FIG. 6 while making
reference to FIG. 1.
[0149] When the main switch 120 of the camera body 101 is closed
(turned on), the microcomputer 102 is activated from the sleep
state and control proceeds from step S101 to step S102, at which
the states of the switches 121-124 inside the camera body 101 are
sensed.
[0150] The state of the photography preparation switch 121 (SW1),
which is turned on by pressing the release button through its first
stroke length, is sensed at step S103. Control returns to step S102
when the switch 121 is off (open) and proceeds to step S104 when
the switch 121 is on.
[0151] The fact that preparation for shutter release has been
executed is communicated to the microcomputer 161 inside the
interchangeable lens 151 at step S104. This is followed by step
S105, at which parameters are communicated to the microcomputer
161. The communication of parameters involves transmitting
lens-specific information such as the lens f-number, focal length
and focusing sensitivity to the camera.
[0152] Next, at step S106, the image sensing device 111 is
activated to acquire an image signal.
[0153] Processing of the image signal acquired at step S106 is
executed at step S107. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0154] This is followed by step S108, at which object brightness
information is calculated from the image signal processed at step
S107. Further, in accordance with a predetermined exposure control
program, a control value for narrowing the stop 155 and the
exposure time (charge storage time) of the image sensing device 111
are calculated.
[0155] The setting of the AF mode switch 123 is discriminated at
step S109 to determine if the autofocus (AF) mode is in effect.
Control proceeds to step S112 if the mode is not the AF mode and to
step S110 if the mode is the AF mode.
[0156] The defocus quantity .DELTA.V of the object is calculated
from the spacing between the two secondary images IMA, IMB at step
S110 in the manner illustrated in FIG. 3. Next, at step S111, the
defocus quantity .DELTA.V calculated at step S110 is transmitted to
the microcomputer 161 inside the lens.
[0157] The state of the photography switch (SW2) 122 is
discriminated at step S112. If the switch 122 is off, control
returns to step S102 so that the processing of steps S102-S111 is
executed again. If the photography switch 122 is found to be on at
step S112, it is judged that release has been performed and control
shifts to step S121.
[0158] The transition to the release operation is communicated to
the microcomputer 161 in the lens at step S121. The stop control
value that was calculated at step S106 is transmitted to the
microcomputer 161 at step S122.
[0159] Next, at step S123, the movable mirror unit 138 is withdrawn
from the photographic optical path of FIG. 1 to the attitude shown
in FIG. 4, where the mirror unit 128 is outside the optical
path.
[0160] Control of charge accumulation and charge transfer in the
image sensing device is performed at step S124 for the purpose of
photography. This is followed by step S125, at which processing of
the image signal acquired at step S124 is executed in the same
manner as performed at step S107. More specifically, the image
signal is applied to A/D conversion, white balance adjustment,
gamma correction and compression processing, etc.
[0161] Next, at step S126, the signal processed at step S125 is
recorded and preserved in the image memory 106. The withdrawn
movable mirror unit 138 is driven at step S127 so as to be returned
to the optical path for photography. An instruction for restoring
the stop 155 is transmitted to the microcomputer 161 at step
S128.
[0162] The image recorded at step S126 is displayed on the display
unit 104 at step S129, thereby allowing the photographer to view
the image that is the result of photography.
[0163] Control returns to step S102 when the above-described
photographic operation is completed.
[0164] FIG. 7 is a flowchart illustrating control of the
microcomputer 161 inside the lens.
[0165] Power is supplied to the interchangeable lens by turning on
the main switch 120 on the camera side, whereupon control proceeds
from step S151 to step S152. The microcomputer 161 is in the sleep
state waiting for communication from the camera body. Control stops
at step S152 if there is no communication from the camera body.
[0166] If communication relating to release preparation
corresponding to step S104 in FIG. 6 is received from the
microcomputer 102, control proceeds from step S152 to step
S153.
[0167] This is followed by step S153, at which the microcomputer
161 inside the lens senses the states of the focus encoder 163 and
zoom encoder 165 and judges the current status of the lens.
Communication of parameters corresponding to step S105 in FIG. 6 is
performed at step S154 based upon the lens status sensed at step
S153.
[0168] A signal representing the amount of defocusing corresponding
to step S111 in FIG. 6 is received at step S155.
[0169] The amount of focusing lens drive necessary is calculated at
step S156 based upon the amount of defocusing received at step S155
and the lens status sensed at step S153. Next, at step S157, the
focusing lens is driven to performing focusing based upon the
amount of drive calculated at step S156.
[0170] It is determined at step S158 whether a release interrupt
corresponding to step S121 of FIG. 6 has occurred. If the decision
is "NO", control returns to step S152. If a release interrupt
occurs, however, control proceeds from step S158 to step S171, at
which driving of the focusing lens is halted.
[0171] A stop control value is received from the microcomputer 102
at step S172. Next, at step S173, the stop actuator 156 is driven
in accordance with the stop control value received at step S172.
Photography is performed on the camera side.
[0172] When the photographic operation on the camera side is
completed, a stop restoration instruction is received at step S174.
The stop is restored to the open state at step S175 in accordance
with this instruction.
[0173] When the photographic operation on the lens side is
completed, control returns to step S152.
[0174] The operation of the camera and lens according to the
foregoing flowcharts will now be summarized.
[0175] At the photography preparation stage, the photographic light
flux is split and projected upon the image sensing device 111 via
the focus detection optical system in the manner shown in FIG. 1.
When the main switch 120 and photography preparation switch 121 are
turned on by the photographer, the camera calculates the defocus
quantity .DELTA.V of the object from the spacing between the two
secondary images projected upon the image sensing device 111, as
shown in FIG. 3, and transmits .DELTA.V to the interchangeable lens
151. In response, the interchangeable lens 151 drives the focusing
lens in accordance with the defocus quantity .DELTA.V, thereby
performing focusing. Next, when the photography switch 122 is
turned on, the movable mirror unit 138 is withdrawn from the
photographic light flux, as shown in FIG. 4, so that the in-focus
image of the object is projected upon the image sensing device 111,
as shown in FIG. 5. The camera acquires the image of the object and
records the image in the image memory 106.
Advantages . . . First Embodiment
[0176] (AD1) The focus detection module 130 composed of the four
mirrors (131-134) is placed in the optical path between the optical
lens system and the image sensing device, and the pair of optical
lenses 137 is provided in the optical path of the focus detection
module 130. The optical lens 137 forms two images on the image
sensing device 111 when the object is not in focus and forms one
image on the image sensing device 111 when the object is in focus.
The defocus quantity .DELTA.V can be obtained based upon the
spacing V.sub.1 between the two images. As a result, it is
unnecessary to separately provide photoelectric conversion means
for focus detection, and both focus detection and focusing can be
performed using the light flux that has passed through the
photographic lens. This makes it possible to realize an
inexpensive, small-size camera exhibiting highly accurate automatic
focusing.
[0177] (AD 2) The focus detection module 130 is disposed in back of
the final lens group (the lens group 154 in the example of FIG. 1)
of the image sensing optical system. As a result, the module is
suited to a digital still camera of the single-lens reflex type
having a long back focus.
[0178] (AD 3) Part of the photographic light flux is split by a
beam splitter (the mirror 132) before being introduced to the
optical finder system (the pentagonal prism 142 and eyepiece 143).
This makes it possible to obtain a high-quality optical finder and
to visually confirm the state of focus of an object image in a
highly accurate manner. The optical path of the optical finder
system and part of the optical path of the focus detection module
130 can be made to coincide, thereby making it possible to reduce
the size of the overall camera.
Modifications . . . First Modification
[0179] (M1) If there is no limitation upon the size of the camera
overall, the optical path of the optical finder system and the
optical path of the focus detection module 130 may be separated
completely. In such case a half-mirror (132', not shown in figures)
such as the mirror 132 is provided between the lens 154 and the
mirror 121, and the mirror 132 is made a fully reflective mirror.
The optical finder is disposed above the mirror 132'.
[0180] (M2) The lenses 137 for splitting the optic axis into two
portions should ideally be provided between the mirror 133 and the
mirror 134. Theoretically, however, it is possible to provide the
lenses 137 between the lens 135 and mirror 133 or between the
mirror 132 and lens 135.
Second Embodiment
[0181] According to the first embodiment set forth above, the pair
of secondary image forming lenses 137 are arranged paralely to the
light incident direction onto the photographic screen 111 (that is,
in a right-to-left direction with respect to the FIG. 1
orientation) so that the two secondary images (IMA and IMB) are
disposed one above the other on the photographic screen 111. In the
second embodiment described below, a pair of secondary image
forming lenses are adapted (in a direction vertical to the surface
of FIG. 1 drawing) to be arranged so that two secondary images are
juxtaposed side by side on the photographic screen and are
vertically offset from the optic axis. Specifically, the
construction of the second embodiment is substantially identical to
that of the first embodiment except for the arrangement of
secondary forming lenses.
[0182] FIG. 8 is a perspective view showing a development of part
of the focus detection optical system according to the second
embodiment, and FIG. 9 is a plan view showing the disposition of
the secondary images on the image sensing device 111. The
construction and operation of this embodiment will now be
described.
[0183] Elements other than those shown in FIG. 8 are identical with
those of the first embodiment illustrated in FIG. 1.
[0184] FIG. 8 schematically illustrates an optical path from the
field mask 136 to the image sensing device 111. In FIG. 8, the
third mirror 133 and the fourth mirror 134 are omitted from the
focus detection module 130 in FIG. 1 for the sake of simplified
illustration purpose.
[0185] According to the second embodiment as shown in FIG. 8, the
pair of two secondary image forming lenses 237 are disposed
horizontally, i.e., side by side with respect to the photographic
screen, between the field lens 135 (having the field mask 136) and
the image sensing device 111. The centers connecting the two
secondary image forming lenses 237 are offset by a distance OFS to
a position below the optic axis C. Accordingly, the projected
images of the field mask 136 formed by the secondary image forming
lenses 237 become downwardly offset areas ARC, ARD on the
light-receiving portion 112 of the image sensing device 111.
[0186] FIG. 9 illustrates the disposition of images on the image
sensing device 111 in the arrangement of FIG. 8. The images ARC,
ARD of the field mask 136 are projected as areas on the
light-receiving portion 112, and secondary images IMC, IMD of the
object OBJ are formed in the areas ARC, ARD, respectively. Let
H.sub.0 represent the spacing between the two images when the
object is in focus, and let H.sub.1 represent the spacing between
the two images when the object is not in focus. If H.sub.1 is
measured and H.sub.0 and H.sub.1 can be compared, then a defocus
quantity .DELTA.H (-H.sub.1-H.sub.0) of the object OBJ can be
detected.
[0187] In FIG. 9, the two secondary image projection areas ARC, ARD
are disposed at the lower part the light-receiving portion 112,
namely on the side near the exit in the transfer direction of the
vertical-transfer CCD in the light-receiving portion. As a result,
only the image signal on the lower half of the light-receiving
portion 112 need be read for the purpose of detecting focus. In
other words, if the image signal on the lower half of the
light-receiving portion 112 is used in image processing for focus
detection, then the image signal of the upper half of the
light-receiving portion 112 maybe discarded without being read. In
the first focus detection cycle, therefore, the time needed to read
out the image signal is shortened.
[0188] The flowcharts for controlling the camera and
interchangeable lens in this embodiment are the same as the control
flowcharts of the first embodiment shown in FIGS. 6 and 7 and need
not be described again.
[0189] The second embodiment has the following advantage in
addition to the advantages (AD1)-(AD3) of the first embodiment:
[0190] Since the image-signal readout time for detecting focus is
shortened, it is possible to speed up the focus detection operation
or autofocus operation.
Third Embodiment
[0191] In the first and second embodiments, focus detection is
carried out based upon one pair of secondary images. In the third
embodiment described below, the optical system is so adapted that
focus detection is carried out by forming two pairs of secondary
images.
[0192] FIG. 10 is a perspective view showing a development of part
of the focus detection optical system according to the third
embodiment, and FIG. 11 is a plan view showing the disposition of
the secondary images on the image sensing device 111. The
construction and operation of this embodiment will now be
described.
[0193] In FIG. 10, two pairs of secondary image forming lenses 337
are disposed between the field lens 135 (having the field mask 136)
and the image sensing device 111. The projected images of the field
mask 136 formed by the secondary image forming lenses 337 become
four areas ARA, ARB, ARC and ARD on the light-receiving portion 112
of the image sensing device 111.
[0194] Elements other than those shown in FIG. 10 are identical
with those of the first embodiment illustrated in FIG. 1.
[0195] FIG. 11 illustrates the disposition of images on the image
sensing device 111 in the arrangement of FIG. 10. The images ARA,
ARB, ARC, ARD of the field mask 136 are projected on the
light-receiving portion 112, and secondary images IMA, ImB, IMC,
IMD of the object OBJ are formed in the areas ARA, ARB, ARC, ARD,
respectively. Let V.sub.0 represent the spacing between the two
images IMA, IMB when the object is in focus, and let H.sub.0
represent the spacing between the two images IMC, IMD when the
object is in focus. If the spacings between the images when the
object is not in focus are measured and compared with the spacings
V.sub.0 and H.sub.0, then a defocus quantity of the object OBJ can
be detected.
[0196] Except for the fact that two sets of operations for
detecting the amount of defocusing of the image of the object are
provided in the third embodiment, the flowcharts for controlling
the camera and interchangeable lens in this embodiment are the same
as the control flowcharts of the first embodiment shown in FIGS. 6
and 7 and need not be described again.
[0197] The third embodiment has the following advantage in addition
to the advantages (AD1)-(AD3) of the first embodiment:
[0198] Since focus detection is carried out based upon images of
the object OBJ that are offset vertically and horizontally, focus
detection can be performed with greater accuracy.
Fourth Embodiment
[0199] In the first through third embodiments described above, the
secondary image forming optical system for focus detection uses
mirrors for deflecting the light flux. In the fourth embodiment
described below, use is made of a reducing lens instead of
mirrors.
[0200] FIGS. 12-17 are diagrams relating to the fourth
embodiment.
[0201] FIG. 12 is a diagram showing the construction of an image
sensing apparatus according to the present invention. This shows
the apparatus when detection of focus is carried out. According to
this embodiment, the focus detection module 130 of the first
embodiment shown in FIG. 1 is replaced by a focus detection module
430. Though the optical finder composed of such elements as the
pentagonal prism is eliminated, other elements are the same as
those shown in FIG. 1. The construction and operation of this
embodiment will now be described.
[0202] As shown in FIG. 12, the focus detection module 430 includes
a reducing lens 431, a field mask 436, a field lens 435 and two
secondary image forming lenses 437. The stop 155 of the
interchangeable lens 151 and the entrance pupil of the pair of
secondary image forming lenses 137 are in a projection relationship
owing to the field lens 135. A quick-return (QR) actuator 439 is
provided for advancing and retracting the focus detection module
430 into and out of the projected light flux.
[0203] The image of the object OBJ is formed as a primary image IM4
on the primary image forming surface in the field lens 435 via the
image sensing optical system, which is constructed by the lens
groups 152-154 and stop 155, and the above-mentioned reducing lens
431. It should be noted that the primary image IM4 has a size
different from that of the first primary image IM1 or IM2 of the
first embodiment owing to the intervention of the reducing lens
431.
[0204] The primary image IM4 is split by the two secondary image
forming lenses 437 disposed one above the other, whereby the image
is formed again. These secondary images are projected upon the
image sensing device 111 as IMA and IMB.
[0205] FIG. 13 is a diagram showing formation of the secondary
images on the image sensing device 111. In a manner similar to that
of the first embodiment, this embodiment detects the amount of
defocusing of the object OBJ based upon a change in the difference
between the two images with respect to the reference spacing value
V.sub.0 between the images.
[0206] FIG. 14 illustrates the state of the display presented on a
display unit 404 when focus detection is performed. One of the two
secondary images, e.g., IMB, projected upon the image sensing
device 111 in FIG. 13 is subjected to enlargement processing and
displayed on the display unit 404 as IMBL, thereby making it
possible for the photographer to check the composition of the
photographic area as well as the state of focusing.
[0207] FIG. 15 is a diagram showing the camera when the photography
switch 122 of the camera body 101 is closed upon the completion of
the autofocus operation, thereby establishing the photographic
state.
[0208] When the photography switch 122 is closed, the entire focus
detection module 430 is withdrawn away from the optical path of
photography (i.e., upward in FIG. 15) by the quick-return actuator
439.
[0209] FIG. 16 is a diagram showing formation of the image of the
object on the image sensing device 111 at the time of photography.
Here the primary image IM3 of the object OBJ is projected onto the
light-receiving portion 112 in a manner similar to that of the
first embodiment. Accordingly, the image signal prevailing under
these conditions is accepted and recorded in the image memory 106
of the camera body 401, whereby the image is sensed.
[0210] FIG. 17 is a flowchart illustrating the control flow of a
microcomputer 402 inside the camera body. This flowchart differs
from that of FIG. 6 only in the addition of an operation for
displaying a finder image at the time of focus detection.
[0211] When the main switch 120 of the camera body 401 is turned
on, the microcomputer 402 is activated from the sleep state and
control proceeds from step S401 to steps S402, S403 and S404.
[0212] The fact that preparation for shutter release has been
executed is communicated to the microcomputer 161 inside the
interchangeable lens 151 at step S404. This is followed by step
S405, at which parameters are communicated to the microcomputer
161.
[0213] Next, at step S406, the image sensing device 111 is
activated to acquire an image signal.
[0214] Processing of the image signal acquired at step S406 is
executed at step S4107. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0215] This is followed by step S408, at which the image to be
displayed on the display unit 404, namely the image in the area ARB
of FIG. 13, is enlarged and then rotated by 180.degree. about its
center. In comparison with the image that prevails at the time of
imaging, therefore, the image is turned upside down when focus
detection is performed.
[0216] The image for viewing purposed obtained at step S408 is
displayed on the display unit 404 at step S409.
[0217] This is followed by step S410, at which object brightness
information is calculated from the image signal processed at step
S407. Further, in accordance with a predetermined exposure control
program, a control value for narrowing the stop 155 and the
exposure time (charge storage time) of the image sensing device 111
are calculated.
[0218] The setting of the AF mode switch 123 is discriminated at
step S411 to determine if the autofocus (AF) mode is in effect.
Control proceeds to step S414 if the mode is not the AF mode and to
step S412 if the mode is the AF mode.
[0219] The amount of defocus of the object is calculated from the
spacing between the two secondary images at step S412 in the manner
illustrated in FIG. 13. Next, at step S413, the amount of defocus
calculated at step S412 is transmitted to the microcomputer 161
inside the lens.
[0220] The state of the photography switch 122 is discriminated at
step S414. If the switch 122 is off, control returns to step S402.
If the photography switch 122 is found to be ON, it is judged that
release has been performed and control shifts to step S421.
[0221] The release sequence of steps S421-S429 is the same as the
processing of steps S121-S129 in FIG. 6 and need not be described
again. Further, the flow for controlling the interchangeable lens
151 is the same as that of the first embodiment shown in FIG. 7 and
need not be described again.
[0222] The operation of the camera and lens according to the
foregoing flow will now be summarized.
[0223] At the photography preparation stage, the photographic light
flux is split and projected upon the image sensing device 111 via
the focus detection module 430 in the manner shown in FIG. 12. When
the main switch 120 and photography preparation switch 121 are
turned on by the photographer, the camera enlarges one of the two
secondary images, which are projected upon the image sensing device
111 in the manner shown in FIG. 13, and displays the enlarged image
on the display unit 404, as illustrated in FIG. 14. Next, the
camera calculates the amount of object defocus from the spacing
between the two secondary images and transmits this to the
interchangeable lens 151. In response, the interchangeable lens 151
drives the focusing lens in accordance with the defocus quantity,
thereby performing focusing. Next, when the photography switch 122
is turned on, the focus detection module 430 is withdrawn from the
photographic light flux, as shown in FIG. 15, so that the in-focus
image of the object is projected upon the image sensing device 111,
as shown in FIG. 16. The camera acquires the image of the object
and records the image in the image memory 106.
[0224] The fourth embodiment has the following advantages in
addition to the advantages (AD1), (AD2) of the first
embodiment:
[0225] (AD6) A mirror for deflecting the optical path is not
required in the focus detection module 430, thereby making it
possible to reduce the size of the module and simplify the
same.
[0226] (AD7) Since the image for purposes of focus detection is
displayed on the monitor screen of the display unit, an optical
finder is unnecessary. This makes it possible to reduce the size
and lower the cost of the apparatus.
Fifth Embodiment
[0227] In the fourth embodiment described above, the reducing lens
is used in the optical system for focus detection. In a fifth
embodiment described below, however, a relay lens is inserted into
the optical system for focus detection and the reducing lens is not
employed.
[0228] FIGS. 18 and 19 are diagrams relating to the fifth
embodiment.
[0229] FIG. 18 is a diagram showing the construction of an image
sensing apparatus according to the present invention. This shows
the apparatus when detection of focus is carried out. According to
this embodiment, the focus detection module 430 of FIG. 12 is
replaced by a focus detection module 530, and a relay lens module
540 is additionally provided. A lens 531 is provided at the
rearmost portion of the image forming optical system inside an
interchangeable lens 551. Other components are the same as shown in
FIG. 12.
[0230] As shown in FIG. 18, the focus detection module 530 includes
a field mask 536, a field lens 535 and a pair of secondary image
forming lenses 537. The stop 155 of the interchangeable lens 551
and the entrance pupil of the pair of secondary image forming
lenses 537 are in a projection relationship owing to the field lens
535.
[0231] The relay lens module 540 is provided internally with a
concave relay lens 541. A quick-return actuator (QR) 539 is
provided for moving the focus detection module 530 and relay lens
module 540 into the photographic light flux alternatively.
[0232] The image of the object OBJ is formed as a primary image IM5
on the primary image forming surface in the field lens 535 via the
image sensing optical system, which is constructed by the lens
groups 152-154, stop 155 and lens 531. The arrangement is such that
the primary image IM5 has a size substantially the same as that of
the image IM4 of the fourth embodiment.
[0233] The primary image IM5 is split by the two secondary image
forming lenses 437, whereby the image is formed again. These
secondary images are projected upon the image sensing device 111 as
IMA and IMB. The projected images are the same as those shown in
FIG. 13. In addition, the viewing image displayed on a display unit
504 is similar to that shown in FIG. 14.
[0234] FIG. 19 is a diagram showing the camera when the photography
switch 122 of the camera body 501 is closed upon the completion of
the autofocus operation, thereby establishing the photographic
state.
[0235] When the photography switch 122 is closed, the entire focus
detection module 530 is withdrawn away from the optical path of
photography (i.e., upward in FIG. 19) by the quick-return actuator
539. The relay lens module 540 is inserted into the photographic
optical path in place of the focus detection module 530. When this
is done, the primary image IM3 formed by the image sensing optical
system in the interchangeable lens 551 and the relay lens 541 in
the camera body 501 is formed on the image sensing device 111. The
state of the formed image is the same as that of the primary image
shown in FIG. 16. Accordingly, the image signal prevailing under
these conditions is accepted and recorded in the image memory 106
of the camera body 501, whereby the image is sensed.
[0236] The control flow of this embodiment is the same as that of
the fourth embodiment and need not be described again.
[0237] The fifth embodiment has the following advantages in
addition to the advantages (AD1), (AD2) of the first embodiment and
the advantages (AD6), (AD7) of the fourth embodiment:
[0238] (AD8) Since use is made of the relay lens 541 advanced and
retracted at the time of photography, greater freedom is provided
in terms of optical design and the optical system can be reduced in
size and improved in performance.
[0239] (AD9) The optical structure of the focus detection module
530 is simplified and optical aberration of this module can be
reduced to improve the accuracy of focus detection.
[0240] It should be noted that the focus detection optical system
of the second or third embodiment may be applied to the fourth or
fifth embodiment. Further, a half-mirror may be placed in front of
the focus detection module of the fourth or fifth embodiment to
extract part of the photographic light flux and introduce this flux
to an optical finder. Furthermore, the invention may be applied not
only to an image sensing apparatus of interchangeable lens type but
also to an image sensing apparatus having a fixed lens.
Sixth Embodiment
[0241] FIGS. 20 through 24 are diagrams relating to the sixth
embodiment.
[0242] FIG. 20 is a block diagram showing the construction of an
image sensing apparatus according to a sixth embodiment.
[0243] Numeral 601 denotes a camera body having various functional
components for forming the image of an object OBJ, detecting focus
and sensing the image.
[0244] The camera body includes the focusing lens group 152 for
performing focusing by being advanced and retracted along the
direction of the optic axis; the zoom lens group 153 for performing
zooming by being advanced and retracted along the direction of the
optic axis; and the relay lens group 154 for performing a
prescribed image forming operation together with the lens groups
152 and 153. The stop 155 decides the entrant light flux of the
image sensing optical system.
[0245] An infrared blocking filter 606 blocks infrared light from
the object OBJ and passes only visible light. The lens groups 152,
153, 154, the stop 155 and the infrared blocking filter 606
together construct the image sensing optical system. A first IM1 of
the object OBJ is formed on a main image sensing device 111.
[0246] As in the first and other embodiments, the main image
sensing device 111 is a two-dimensional photoelectric sensor, such
as a CCD, for photoelectrically converting the first image IM1.
[0247] The camera body further includes a rangefinding module 621
having a light-receiving lens 622 for forming the image of the
object OBJ whose range is to be measured, an infrared blocking
filter 623 for blocking infrared light and passing only visible
light of the light flux that has passed through the light-receiving
lens 622, and a subordinate image sensing device 624. The
rangefinding optical system, which includes the light-receiving
lens 622 and the infrared blocking filter 623, has an image forming
power different from that of the above-mentioned image sensing
optical system and forms a second image IM2 of the object OBJ on
the subordinate image sensing device 624, described later.
[0248] The subordinate image sensing device 624, such as a CCD, is
a two-dimensional photoelectric sensor for photoelectrically
converting the second image IM2. The module 621 including these
elements is so disposed that its optic axis is spaced away from the
optic axis of the image sensing optical system by a distance
equivalent to a baselength BL.
[0249] A microcomputer 631 is a single-chip microcomputer having a
ROM, a RAM and A/D, D/A conversion functions. In accordance with a
camera sequence program stored in the ROM (not shown), the
microcomputer 631 implements a series of camera operations such as
automatic exposure control (AE), autofocus (AF) and image sensing.
To this end, the microcomputer 631 controls the operation of
peripheral circuits and actuators inside the camera body 601.
According to the present invention, the ROM constitutes a storage
medium and can be a semiconductor memory, an optical disk, a
magneto-optic disk or a magnetic medium, etc.
[0250] The power supply 103 supplies the camera circuits and
actuators with power.
[0251] The driver 105 drives and controls the main image sensing
device 111. The driver 105 controls the storage of charge in the
image sensing device 111, charge-transfer, CDS (Correlated Double
Sampling), AGC (Automatic Gain Control), A/D conversion, gamma
correction and AWB (Automatic White Balance), etc.
[0252] A driver 634 drives and controls the subordinate image
sensing device 624 and, like the driver 105 of the main image
sensing device, controls the storage of charge in the image sensing
device 111, charge transfer, CDS, AGC, A/D conversion, gamma
correction and AWB, etc.
[0253] The memory 106 records and preserves image signal data
representing an image sensed by the main image sensing device 111
and can be a semiconductor memory, optical disk, magneto-optical
disk or magnetic medium, etc.
[0254] The terminal 107 for outputting a recorded image to external
equipment is connected to a personal computer or printer.
[0255] The camera body has a display unit 104, such as a liquid
crystal panel, having a display function for displaying
photographic conditions and a monitor function for monitoring a
photographic image.
[0256] As in the first embodiment, the camera body has the main
switch 120. When this switch is turned on, the microcomputer 631
allows the execution of a prescribed program relating to
preparations for photography, namely exposure metering and focus
detection, etc.
[0257] The switches 121 and 122 are linked to the camera release
button and are turned on by pressing the release button through
first and second stroke lengths, respectively. More specifically,
the switch 121 is for preparing for picture taking. When this
switch is turned on, preparatory photographic operations such as
exposure metering, focus detection and focusing are executed. The
switch 122 is a photography switch. When this switch is turned on,
a photographic image that has been formed on the image sensing
device 111 is acquired and recorded in the image memory 106.
[0258] The AF mode switch 123 is used to select the autofocus mode.
The display switch 124 is used to designate a display for
monitoring a photographic image.
[0259] The focus actuator 162 drives the focusing lens group 152 to
advance and retract the same, and the focus encoder 163 senses
position information indicative of the position of the focusing
lens group 152, namely object distance information. The zoom
actuator 164 drives the zoom lens group 153 to advance and retract
the same, and the zoom encoder 165 senses position information
indicative of the position of the zoom lens group 153, namely focal
length information.
[0260] The stop actuator 156 controls the stopping down of the stop
155 and restores the stop 155 to the open state.
[0261] By virtue of the construction described above, the camera
body 601 acquires the first image IM1 and second image IM2 of the
object OBJ and performs rangefinding, focusing, and image sensing
through methods described later.
Principles . . . Sixth Embodiment
[0262] The state of image formation of the object OBJ at the time
of focus detection prior to preparations for photography will now
be described.
[0263] A light flux from the object OBJ passes through the image
sensing optical system comprising the lens groups 152, 153, 154 and
is formed on the main image sensing device 111 as the first image
IM1. Further, the second image IM2 is formed on the subordinate
image sensing device 624 inside the rangefinding module 621.
[0264] FIGS. 21A, 21B are diagrams illustrating the two image
sensing devices 111, 624 and the dispositions of two images formed
on these image sensing devices.
[0265] The light-receiving portion 112 of the image sensing device
111 comprises m.sub.1.times.n.sub.1 light-receiving pixels and a
charge transfer portion (vertical transfer CCD) for transferring
electric charge that has accumulated in these pixels. The
horizontal transfer CCD 113 stores electric charge transferred in
the direction of arrow TRV by the vertical transfer CCD in the
light-receiving portion 112, then transfers the charge in the
direction of arrow TRH and outputs an image signal from the signal
output portion 114 to the image sensor driver 105.
[0266] In FIG. 21B, IM1.sub.T represents the image of the object
OBJ when the image sensing optical system has been set to the
maximum telescopic mode, and IM1.sub.W represents the image of the
object OBJ when the image sensing optical system has been set to
the maximum wide-angle mode. Thus, the size of the first image IM1
of the object varies depending upon the state of the image sensing
optical system.
[0267] A light-receiving portion 625 of the subordinate image
sensing device 624 comprises m.sub.2.times.n.sub.2 light-receiving
pixels and a charge transfer portion (vertical transfer CCD) for
transferring electric charge that has accumulated in these pixels.
A horizontal transfer CCD 626 stores electric charge transferred in
the direction of arrow TRV by the vertical transfer CCD in the
light-receiving portion 625, then transfers the charge in the
direction of arrow TRH and outputs an image signal from the signal
output portion 627 to the image sensor driver 634.
[0268] In FIG. 21A, IM2.sub.INF represents the image obtained when
the object OBJ is at infinity, and IM2.sub.DEF represents the image
obtained when the object OBJ is at a finite distance. Thus, the
position of the second image IM2 of the object varies depending
upon the distance of the object OBJ.
[0269] FIGS. 22A, 22B are diagrams useful in describing the
principle of image magnification correction for detecting object
distance from the first and second images IM1 and IM2,
respectively, of the object.
[0270] According to the principle of rangefinding by triangulation,
a disparity in regard to the object is detected from the relative
positions of two images formed by two image forming systems spaced
apart by a predetermined baselength, and the object distance is
found from this disparity. In this case, it is required that the
sizes of the two images be equalized. However, as described above
in connection with FIGS. 21A, 21B, the first image IM1 varies in
size depending upon the zoom setting of the image sensing optical
system. Even if the two images have the same optical size, the
number of pixels (or pixel size) of the light-receiving portion 112
of image sensing device 111 and the number of pixels (or pixel
size) of the light-receiving portion 625 of image sensing device
624 differ. Consequently, if the image signal is processed
digitally, it is necessary to subject the image to a magnitude
correction based upon the difference in the numbers of pixels.
[0271] In this embodiment, the image forming characteristics of the
image sensing optical system are recognized from the results of
detection from the focus encoder 163 and zoom encoder 165 inside
the camera body 601, and the size of the first image IM1 is made
equal to the size of the second image IM2 based upon the results of
recognition.
[0272] FIGS. 22A, 22B are diagrams illustrating the respective
images after application of the above-described size correction.
FIGS. 21A, 21B illustrate the sizes of the optical images on the
image sensing devices 624, 111, while FIGS. 22A, 22B conceptually
illustrate the image signals in image computation memories (not
shown in FIG. 20) within the microcomputer 631. In FIG. 22A,
IM2.sub.DEF represents the image signal read out of the subordinate
image sensing device 624 and stored in a second computation memory
RAM2, and IM1.sub.0 represents the image signal read out of the
main image sensing device 111 and stored in a first computation
memory RAM1. The signal IM1.sub.0is an image signal that has
undergone the size correction described above. As the result of the
size correction, the image IM2.sub.DEF regarding the second image
IM2 of the object and the image IM1.sub.0 regarding the first image
IM1 of the object are the same in size but and differ only in terms
of their relative positions, as illustrated in FIG. 23.
[0273] FIG. 23 is a schematic view showing spacing V.sub.DEF of
image signals stored in the two computation memories RAM1, RAM2
mentioned above.
[0274] In accordance with a well-known correlation algorithm, the
distance V.sub.DEF of the image IM2.sub.DEF relative from the image
IM1.sub.0 is obtained and distance DST to the object OBJ can be
calculated from the following equation using a reference spacing
V.sub.0, focal length f of the light-receiving lens 622 and
baselength BL of the rangefinding module 621: 1 DST = f BL V
(EQ.1)
[0275] where the following holds:
.DELTA.V=V.sub.DEF-V.sub.0 (EQ.2)
[0276] Ideally, the reference spacing V.sub.0 should be zero when
the object is at infinity. In general, however, the optical systems
and image sensing elements develop positional offsets in the camera
manufacturing process. According to this embodiment, therefore,
information representing the reference spacing V.sub.0 conforming
to the positions of the focusing lens group 152 and zoom lens group
153 is stored in the ROM (not shown) of the microcomputer 631.
[0277] FIG. 24 is a flowchart showing the control flow of the
microcomputer 631 when focus detection, focusing and photography
are performed in the camera body 601 according to the sixth
embodiment.
Control Procedure . . . Sixth Embodiment
[0278] The control flow of FIG. 24 will be described while making
reference to FIGS. 20 through 23.
[0279] When the main switch 120 of the camera body 101 is turned
on, the microcomputer 631 is activated from the sleep state and
control proceeds from step S501 to step S502, at which the states
of the switches 121-124 inside the camera body 601 are sensed.
[0280] The state of the photography preparation switch 121 (SW1),
which is turned on by pressing the release button through its first
stroke length, is sensed at step S503. Control returns to step S502
when the switch 121 is off and proceeds to step S504 when the
switch 121 is on.
[0281] Next, at step S504, the main image sensing device 111 is
activated to acquire an image signal.
[0282] Processing of the image signal acquired at step S504 is
executed at step S505. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0283] This is followed by step S506, at which object brightness
information is calculated from the image signal processed at step
S505. Further, in accordance with a predetermined exposure control
program, a control value for stopping down the stop 155 and the
exposure time (charge storage time) of the image sensing device 111
are calculated.
[0284] The image signal produced by the image sensing device 111 at
steps S504 and S505, namely the image signal 1M1.sub.W or 1M1.sub.T
in FIG. 21B, is displayed on the display unit 104 at step S507.
[0285] Next, the setting of the AF mode switch 123 is discriminated
at step S508 to determine if the autofocus (AF) mode is in effect.
Control jumps to step S520 if the mode is not the AF mode and
proceeds to step S511 if the mode is the AF mode. The autofocus
operation, described below, is then executed.
[0286] The microcomputer 631 senses the state of the focus encoder
163 at step S511 and senses the state of the zoom encoder 165 at
step S512 to judge the current optical status of the lens.
[0287] A coefficient for making the size of the first image IM1 of
the object equal to that the second image of the object, namely an
image magnification correction coefficient, is read out of the ROM
(not shown) of microcomputer 631 at step S513 in the manner
described above in connection with FIGS. 22A, 22B. Coefficients are
stored in the ROM as matrix data corresponding to the states of the
focus encoder 163 and zoom encoder 165.
[0288] Next, a position offset correction quantity V.sub.0 is read
out of ROM at step S514 in the same manner as the image
magnification correction coefficient.
[0289] The subordinate image sensing device 624 is activated at
step S515 to obtain an image signal.
[0290] Processing of the image signal acquired at step S515 is
executed at step S516. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0291] This is followed by step S517, at which image size is
corrected by multiplying the image signal of the first image IM1
acquired at step S505 by the image magnification correction
coefficient read out at step S513.
[0292] Next, at step S518, the distance to the object is calculated
in accordance with Equations (EQ.1), (EQ.2) using the first image
IM1 whose size has been corrected at step S517, the second image
IM2 obtained at step S516 and the position offset correction
quantity V.sub.0 obtained at step S514.
[0293] The focusing lens group 152 is driven at step S519 based
upon the result of the above-described calculation to bring the
first image IM1, which is for image sensing purposes, into
focus.
[0294] The state of the photography switch 122 (SW2) is
discriminated at step S520. If the switch 122 is off, control
returns to step S502 so that the processing of steps S502-S519 is
executed again. If the photography switch 122 is found to be on at
step S520, it is judged that release has been performed and control
shifts to step S521.
[0295] The stop actuator 166 is driven at step S521 in accordance
with the stop control value calculated at step S506.
[0296] Charge accumulation and charge transfer of the main image
sensing device 111 for photography are controlled at step S522.
This is followed by step S523, at which processing of the image
signal acquired at step S522 is executed in the same manner as
performed at step S505. More specifically, the image signal is
applied to A/D conversion, white balance adjustment, gamma
correction and compression processing, etc.
[0297] Next, at step S524, the signal processed at step S523 is
recorded and preserved in the image memory 106. The image recorded
at step S524 is displayed on the display unit 104 at step S525,
thereby allowing the photographer to check the image that is the
result of photography.
[0298] The stop actuator 166 is restored to open the stop 155 at
step S526.
[0299] Control returns to step S502 when the above-described
photographic operation is completed.
[0300] The operation of the camera according to the foregoing
flowchart will now be summarized.
[0301] At the photography preparation stage, the first image IM1 of
the object is formed on the image sensing device 111 via the image
sensing optical system and the second image IM2 of the object is
formed on the subordinate image sensing device 624 via the
light-receiving lens 622, as illustrated in FIG. 20 and FIGS. 21A,
21B.
[0302] When the main switch 120 and photography preparation switch
121 are turned on by the photographer, the camera obtains the two
above-mentioned images, performs the image magnification
correction, as shown in FIGS. 22A, 22B, and calculates the distance
to the object OBJ by calculating the spacing between the two images
in the manner shown in FIG. 23. The focusing lens group 152 is
driven based upon the calculated value, whereby focusing is
achieved. Continuous focusing is performed by executing this
operation repeatedly. Meanwhile, the first image IM1 of the object
is displayed on the display unit 104 to inform the photographer of
the composition of the picture taken and of the state of
focusing.
[0303] When the photography switch 122 is turned on, the image of
the object projected upon the image sensing device 111 is recorded
in the image memory 106 and image of the picture taken is displayed
on the display unit 104.
Advantages . . . Sixth Embodiment
[0304] The sixth embodiment provides the following advantages:
[0305] (AD10) The rangefinding module can be simplified to make
possible an autofocus camera that is compact and low in price.
[0306] (AD11) The image sensing optical system serves also as the
rangefinding optical system. As a result, when telescopic
photography requiring more accurate rangefinding is performed, the
image of the object for rangefinding purposes is also projected in
enlarged size. This makes it possible to achieve a rangefinding
accuracy that conforms to the state of the image sensing optical
system.
[0307] (AD12) Parameter correction, e.g., correction of image
magnification, at the time of rangefinding computation is carried
out using a rangefinding parameter that conforms to the state of
the image sensing optical system. Even if the state of the image
sensing optical system changes, therefore, accurate detection of
object distance is possible at all times.
[0308] (AD13) The autofocus operation is executed repeatedly at the
photography preparation stage. This makes it possible to shorten
release time lag from issuance of a photography start instruction
to implementation of image sensing.
[0309] (AD14) Since the automatically focused image of the object
is displayed on the display unit 104 such as a liquid crystal
monitor, the state of focus of the image of the object can be
verified visually and accurately in real-time.
Seventh Embodiment
[0310] The sixth embodiment concerns a passive-triangulation-type
rangefinding device composed of a single image sensing system and a
single rangefinding module. A seventh embodiment described below
provides an active-triangulation-type rangefinding device (i.e., a
device in which infrared light is projected upon an object and
rangefinding is performed based upon the reflected light)
comprising a single image sensing system and a single projection
system.
Seventh Embodiment
[0311] FIGS. 25 through 31 are diagrams for describing the
construction and operation of the seventh embodiment. FIG. 25
illustrates the disposition of the image sensing apparatus when
rangefinding is performed according to the seventh embodiment.
Components in FIGS. 25 through 31 that perform actions identical
with those of the sixth embodiment are designated by like reference
characters and need not be described again in detail.
[0312] Numeral 701 denotes a camera body having various functional
components for forming the image of an object OBJ, detecting focus
and sensing the image. The image sensing optical system is composed
of the elements 152-155 of the sixth embodiment.
[0313] An infrared blocking filter 706 blocks infrared light from
the object OBJ and passes only visible light. Since the filter 706
is used for ordinary image sensing, it is withdrawn from the light
flux of the sensed image at the time of rangefinding (shown in FIG.
25).
[0314] An infrared passing filter 707 blocks visible light and
passes only infrared light from the object OBJ. Since the filter
707 is used for rangefinding, the filter is inserted into the light
flux of the sensed image only at the time of rangefinding. The lens
groups 152, 153, 154, stop 155 and filters 706, 707 together
construct the image sensing optical system.
[0315] Numeral 711 denotes an image sensing device such as a CCD.
This is a two-dimensional photoelectric sensor for
photoelectrically converting the object image, which is for image
sensing purposes, or the image of an infrared spot which is for
rangefinding, described later. The image sensing device 711 is
sensitive to light from the visible to infrared wavelengths.
[0316] A projection module 721 includes a light-emitting element
724 which emits infrared light from a light-emitting portion 723,
and a projecting lens 722 for projecting the emitted infrared light
onto the object OBJ. The projection module 721 having these
elements is spaced away from the optic axis of the image sensing
optical system by the baselength BL. As a result, a rangefinding
pattern that corresponds to the projected image of the
light-emitting portion 723, namely an infrared spot SPT, is formed
on the object OBJ. The infrared spot SPT is formed, via the image
sensing optical system, as an infrared spot image SPT.sub.1 on the
main image sensing device 711 at a position spaced a predetermined
distance away from the center thereof. Since the infrared passing
filter 707 has been inserted into the light flux of the sensed
image, the light flux of the object OBJ per se does not pass
through the filter; only the light flux from the infrared spot SPT
arrives at the main image sensing device 711.
[0317] A driver 734 drives the light-emitting element 724 so that
the latter emits rangefinding infrared light at the time of a
rangefinding operation in accordance with an instruction from a
microcomputer 731.
[0318] The microcomputer 731 is a single-chip microcomputer having
a ROM, a RAM and A/D, D/A conversion functions. In accordance with
a camera sequence program stored in the ROM serving as a storage
medium, the microcomputer 731 implements a series of camera
operations such as automatic exposure control (AE), autofocus (AF)
and image sensing in a manner similar to that of the sixth
embodiment. To this end, the microcomputer 731 controls the
operation of peripheral circuits and actuators inside the camera
body 701.
[0319] The power supply 103, driver 105, memory 106, terminal 107,
display unit 104 and switches 120-124, 162-166 are similar to those
of the sixth embodiment.
[0320] An optical finder 761 is composed of a lens group 762, a
zoom lens 762, an erecting prism 764 such as a Porro lens, a field
mask 765 and an eyepiece 766. A zoom linkage member 767
mechanically connects the zoom lens 153 with the zoom lens 763. The
magnification of the optical finder 761 is automatically adjusted
by the zoom linkage member 767 in operative association with the
zooming operation of the image sensing optical system. An exposure
metering element 768 is disposed in the vicinity of the optical
finder 761. The exposure metering element 768 splits the light flux
within the optical finder 761 by a beam splitter (not shown) and
measures the brightness of the object before a picture is
taken.
Principles . . . Seventh Embodiment
[0321] An erect real image IM2 of the object OBJ is projected into
the field mask 765 by the optical finder 761 so that the
photographer can verify the zone of photography by viewing the
finder image IM2 through the eyepiece 766.
[0322] The state of image formation of the infrared spot image
SPT.sub.1 at the time of rangefinding, which is a preparation for
photography, will now be described.
[0323] FIG. 26 is a diagram illustrating the disposition of the
infrared spot image SPT.sub.1 formed on the main image sensing
device at the time of rangefinding.
[0324] A light-receiving portion 212 of the main image sensing
device 711 comprises m.sub.1.times.n.sub.1 light-receiving pixels
and a charge transfer portion (vertical transfer CCD) for
transferring electric charge that has accumulated in these pixels.
A horizontal transfer CCD 213 stores electric charge transferred in
the direction of arrow TRV by the vertical transfer CCD in the
light-receiving portion 212, then transfers the charge in the
direction of arrow TRH and outputs an image signal from a signal
output portion 214 to the image sensor driver 105.
[0325] Further, SPT1.sub.T represents the image of the infrared
spot SPT when the image sensing optical system has been set to the
maximum telescopic mode, and SPT1.sub.W represents the image of the
infrared spot when the image sensing optical system has been set to
the maximum wide-angle mode. Thus, the size and projected position
of the image vary depending upon the state of the image sensing
optical system.
[0326] FIG. 27 illustrates the result of subjecting the image
SPT1.sub.T or SPT1.sub.W to processing similar to that of the sixth
embodiment and normalizing size and position. The normalized image
signal is indicated at SPT1.sub.0. Spacing V.sub.DEF between the
position of the center of gravity of the signal SPT1.sub.0 and a
predetermined reference position C is obtained. Distance DST to the
object OBJ can be detected in accordance with Equations (EQ.1) and
(EQ.2), in a manner similar to that of the sixth embodiment, using
the reference spacing V.sub.0, normalized focal length f.sub.0 of
the image sensing optical system and baselength BL of the optical
finder 761. As in the sixth embodiment, information relating to the
reference spacing V.sub.0 conforming to the positions of the
focusing lens group 152 and zoom lens group 153 is stored in the
ROM of the microcomputer 731. Further, f.sub.0 represents the focal
length of the image sensing optical system normalized by
normalization of the size and position of the spot image. This is
an imaginary focal length for obtaining the normalized image signal
SPT1.sub.0 of FIG. 27 at all times even if there is a changed in
the zoom state.
[0327] The object OBJ is brought into focus automatically if the
focusing lens group 152 is driven based upon the distance DST to
the object OBJ calculated in accordance with Equations (EQ.1),
(EQ.2).
[0328] FIG. 28 is a diagram showing the camera when the photography
switch 122 of the camera body 701 is closed upon the completion of
the autofocus operation, thereby establishing the image sensing
state.
[0329] When the photography switch 122 is turned on, the
light-emitting element 724 stops emitting infrared light. The
filter actuator 708 is then actuated to withdraw the infrared
passing filter 707 from the photographic light flux and insert the
infrared blocking filter 706 into the light flux. When this is
done, the image IM1 of the object OBJ is formed on the main image
sensing device 711 via the image sensing optical system. If FIGS.
25 and 28 are compared, it will be seen that the positions of the
infrared blocking filter 706 and infrared passing filter 707 are
reversed.
[0330] FIG. 29 is a diagram showing formation of the image of the
object on the main image sensing device 711 at the time of
photography. The primary image IM1 of the object OBJ is projected
upon the image-receiving portion 212. Accordingly, the image signal
is acquired under these conditions and recorded in the image memory
106 of the camera body 701, whereby the image is sensed.
[0331] FIG. 30 is a diagram showing the state of the display on the
display unit 104 after image sensing. The image IM1 acquired in
FIG. 29 is displayed on the display screen of the display unit 104
as an image IM1.sub.L resulting from photography. This allows the
photographer to determine whether photography has been performed
correctly.
[0332] FIG. 31 is a flowchart showing the control flow of the
microcomputer 731 when focus detection, focusing and photography
are performed in the camera body 701 according to the seventh
embodiment. The control flowchart of FIG. 31 will be described with
reference to FIGS. 25 through 30.
[0333] When the main switch 120 of the camera body 701 is turned
on, the microcomputer 731 is activated from the sleep state and
control proceeds from step S601 to step S602, at which the states
of the switches 121-124 inside the camera body 701 are sensed.
[0334] The state of the photography preparation switch 121 (SW1),
which is turned on by pressing the release button through its first
stroke length, is sensed at step S603. Control returns to step S602
when the switch 121 is off and proceeds to step S604 when the
switch 121 is on.
[0335] This is followed by step S604, at which the output of the
exposure metering element 768 is read out, object brightness
information is calculated and, in accordance with a predetermined
exposure control program, a control value for narrowing the stop
155 and the exposure time (charge storage time) of the image
sensing device 711 are calculated.
[0336] Next, the setting of the AF mode switch 123 is discriminated
at step S605 to determine if the autofocus (AF) mode is in effect.
Control jumps to step S619 if the mode is not the AF mode and
proceeds to step S611 if the mode is the AF mode.
[0337] The microcomputer 731 senses the state of the zoom encoder
165 at step S611 to judge the current optical status of the lens.
It should be noted that when rangefinding is performed according to
this embodiment, the focusing lens 152 is always at an initial
position that corresponds to infinity. The state of the focus
encoder 163, therefore, is not sensed.
[0338] A coefficient for making the size of the infrared spot image
SPT1 conform to the reference value, namely an image magnification
correction coefficient, is read out of the ROM (not shown) of
microcomputer 731 at step S612 in the manner described above in
connection with FIG. 27. Coefficients are stored in the ROM as
matrix data corresponding to the state of the zoom encoder 165.
[0339] Next, the image position offset correction quantity V.sub.0
is read out of ROM at step S613 in the same manner as the image
magnification correction coefficient.
[0340] The light-emitting element 724 is activated at step S614 to
project rangefinding infrared light toward the object OBJ.
[0341] The main image sensing device 711 is activated at step S615
to obtain the signal representing the infrared spot image
SPT.sub.1.
[0342] Processing of the image signal acquired at step S615 is
executed at step S616. More specifically, the image signal is
converted from an analog to a digital quantity.
[0343] This is followed by step S617, at which image size is
corrected by multiplying the image signal of the infrared spot
image SPT.sub.1 acquired at step S616 by the image magnification
correction coefficient read out at step S612. The resulting signal
is converted to the signal SPT10 normalized in the manner shown in
FIG. 27.
[0344] Next, at step S618, the distance DEF to the object is
calculated upon calculating V.sub.DEF in accordance with Equations
(EQ.1), (EQ.2) using the normalized signal SPT10 obtained at step
S617 and the positional offset correction quantity V.sub.0 obtained
at step S613.
[0345] The state of the photography switch 122 (SW2) is
discriminated at step S619. If the switch 122 is off, control
returns to step S602 so that the processing of steps S602-S618,
namely the rangefinding operation, is executed again. If the
photography switch 122 is found to be on at step S619, it is judged
that release has been performed and control shifts to step
S621.
[0346] The focusing lens 152 is driven at step S621 based upon the
result of the calculation at step S618 to bring the image IM1 into
focus.
[0347] The filter actuator 708 is driven at step S622 to withdraw
the infrared passing filter 707 from the photographic light flux
and insert the infrared blocking filter 706 into the photographic
light flux instead.
[0348] The stop actuator 166 is driven at step S623 in accordance
with the stop control value calculated at step S604.
[0349] Charge accumulation and charge transfer of the main image
sensing device for photography are controlled at step S624. This is
followed by step S625, at which processing of the image signal
acquired at the above-mentioned steps is executed. More
specifically, the image signal is applied to A/D conversion, white
balance adjustment, gamma correction and compression processing,
etc.
[0350] Next, at step S626, the signal processed at step S625 is
recorded and preserved in the image memory 106. The image recorded
at step S626 is displayed on the display unit 104 at step S627,
thereby allowing the photographer to check the image that is the
result of photography.
[0351] The stop actuator 166 is restored to open the stop 155 at
step S628. The infrared blocking filter 706 and infrared passing
filter 707 are interchanged, i.e., restored to the positions that
prevail at the time of the rangefinding operation, at step S629.
The focusing lens group 152 is restored to its initial position at
step S630.
[0352] Control returns to step S502 when the above-described
photographic operation is completed.
[0353] The operation of the camera according to the foregoing
flowchart will now be summarized.
[0354] When a switch operation in preparation for photography is
performed by the photographer, infrared light is projected toward
the object OBJ from the projection module 721 to form the infrared
spot SPT on the object, as shown in FIG. 25. As a result, the image
sensing optical system forms the image of the infrared spot SPT on
the main image sensing device 711 via the infrared passing filter
707, and the distance to the object OBJ is detected based upon the
amount of shift of the spot image from the reference position.
[0355] Next, when a picture is taken, the projection of infrared
light is halted and the focusing lens is driven based upon the
results of rangefinding. Next, photography is performed upon
changing over the filter in front of the main image sensing device
711 to the infrared blocking filter 706, namely to the filter that
passes visible light, the image acquired is stored and preserved in
the image memory 106 and the image of the picture taken is
displayed on the display unit 104.
[0356] In accordance with the seventh embodiment, the following
advantages are obtained in addition to the advantages (AD10)-(AD14)
of the sixth embodiment:
[0357] (AD15) An active-triangulation-type rangefinding device that
projects infrared light can be provided. This makes it possible to
sense distance accurately even in a dark field.
[0358] (AD16) Since an infrared spot image is obtained by an image
sensing optical system having a large aperture, it is possible to
measure distance even to a distant object.
[0359] (AD17) Since a changeover is made between an infrared
passing filter used for rangefinding and an infrared blocking
filter used for imaging, rangefinding can be performed without the
influence of external light even when the field is bright. In
addition, degradation of the photographic image by infrared light
can be prevented at the time of imaging, making it possible to
obtain a high-quality image.
[0360] (AD18) Since the camera has an optical finder, it is
unnecessary to present an image display by a liquid crystal monitor
or the like at the time of photographic preparations such as
rangefinding. This makes it possible to conserve power.
Eighth Embodiment
[0361] In the sixth embodiment described above, the image from the
main image sensing device 111 is displayed on the display unit 104,
such as a liquid crystal monitor, as is when rangefinding is
performed. However, a liquid crystal monitor provides a display of
low resolution and, though it makes it possible to roughly
ascertain the focused state, accurate verification of focusing is
difficult. In an eighth embodiment described below, a second image
of an object is displayed superimposed on a first image of the
object after being shifted by an amount proportional to the amount
of defocusing. In other words, the eighth embodiment provides a
finder of double-image coincidence type.
[0362] FIGS. 32 through 35 are diagrams relating to the eighth
embodiment.
[0363] FIG. 32 is a block diagram showing the structure of a camera
body 801 used in the eighth embodiment. The components are the same
as those of the sixth embodiment, the only difference being the
manner of control at the time of rangefinding and the manner in
which an image is displayed. In the camera body 801 of FIG. 32, the
reference numerals 831 and 804 of the microcomputer and display
unit, respectively, are different from those of the sixth
embodiment. All other components are the same as those of the sixth
embodiment and operate in the same fashion and need not be
described again.
[0364] FIG. 33 corresponds to FIG. 23 of the sixth embodiment and
illustrates a first object image IM31.sub.0 for imaging formed in
the computation memory and a second object image IM32DEF within the
rangefinding module 621. In the sixth embodiment, computation is
performed to make the size of the first image IM1 of the object
conform to the size of the second image of the object. According to
the eighth embodiment, however, these images are used in presenting
a display. The second image, therefore, is made to conform to the
first image, which is for image picture-taking purposes, and it is
so arranged that the sizes and limits of the images displayed on
the display unit 804 will coincide with the imaging area.
[0365] FIG. 34 is a diagram illustrating the state of a display on
the display unit 804 displaying the image signals of FIG. 33.
[0366] An image IM31L from the main image sensing device 111 is
displayed over the entire display area. A rectangular area AR
centered on the display area is a twin-image display area in which
an image IM32L, which is obtained by extracting part of the image
from the subordinate image sensing device 624, is displayed in
superposition on the image IM31L. The images IM31L and IM32L are
displayed in a form offset from each other by an amount DELTA
calculated in accordance with the following equation:
DELTA=K.multidot.(V.sub.DEF-D.sub.FOCUS) (EQ.3)
[0367] where V.sub.DEF represents a quantity relating to the
distance to the object OBJ, D.sub.FOCUS a quantity relating to the
amount of feed of the focusing lens 152 and K a coefficient for
improving visibility by enlarging the display offset quantity.
[0368] For example, if we assume that the distance to the object
OBJ is infinity and that the amount of feed of the focusing lens
152 for focusing the object is zero, then we have
DELTA=K.multidot.(V.sub.DEF-D.sub.FOCUS)=K.multidot.(0-0)=0
(EQ4)
[0369] If the distance to the object is finite, then values of
V.sub.DEF and D.sub.FOCUS conforming thereto are used. However, if
the object is in focus owing to feed of the focusing lens 152, then
DELTA=0 holds at this time as well.
[0370] In other words, if the offset quantity DELTA corresponds to
the amount of focal shift of the image sensing system with respect
to the object OBJ and the image IM1 of the object is in focus, then
DELTA will always be equal to zero. Accordingly, a coincidence
finder can be implemented by the arrangement described above.
[0371] FIG. 35 is a flowchart illustrating the flow of control by
the microcomputer 831 in a case where focus detection, focusing and
photography are carried out in the camera body 801 of the eighth
embodiment.
[0372] The control flow of FIG. 35 will be described while making
reference to FIGS. 32 and 34.
[0373] When the main switch 120 of the camera body 801 is turned
on, the microcomputer 831 is activated from the sleep state and
control proceeds from step S701 to step S702, at which the states
of the switches 121-124 inside the camera body 801 are sensed.
[0374] The state of the photography preparation switch 121 (SW1),
which is turned on by pressing the release button through its first
stroke length, is sensed at step S703. Control returns to step S702
when the switch 121 is off and proceeds to step S704 when the
switch 121 is on.
[0375] Next, at step S704, the main image sensing device 111 is
activated to acquire an image signal.
[0376] Processing of the image signal acquired at step S704 is
executed at step S705. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0377] This is followed by step S706, at which object brightness
information is calculated from the image signal processed at step
S705. Further, in accordance with a predetermined exposure control
program, a control value for stopping down the stop 155 and the
exposure time (charge storage time) of the image sensing device 111
are calculated.
[0378] Next, the setting of the AF mode switch 123 is discriminated
at step S707 to determine if the autofocus (AF) mode is in effect.
Control jumps to step S722 if the mode is not the AF mode and
proceeds to step S711 if the mode is the AF mode.
[0379] The microcomputer 831 senses the state of the focus encoder
163 at step S711 and senses the state of the zoom encoder 165 at
step S712 to judge the current optical status of the lens.
[0380] A coefficient for making the size of the first image IM1 of
the object equal to that the second image of the object, namely an
image magnification correction coefficient, is read out of the ROM
of microcomputer 831 at step S713 in the manner described above in
connection with FIGS. 22A, 22B. Coefficients are stored in the ROM
as matrix data corresponding to the states of the focus encoder 163
and zoom encoder 165.
[0381] Next, a position offset correction quantity V.sub.0 is read
out of the ROM at step S714 in the same manner as the image
magnification correction coefficient.
[0382] The subordinate image sensing device 624 is activated at
step S715 to obtain an image signal.
[0383] Processing of the image signal acquired at step S715 is
executed at step S716. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0384] This is followed by step S717, at which image size is
corrected by multiplying the image signal of the second image IM2
acquired at step S715 by the reciprocal of the image magnification
correction coefficient read out at step S713.
[0385] Next, at step S718, the distance to the object is calculated
in accordance with Equations (EQ.1), (EQ.2) using the second image
IM2 that was subjected to the image magnification correction at
step S717, the first image IM1 obtained at step S705 and the
position offset correction quantity V.sub.0 obtained at step
S714.
[0386] The focusing lens group 152 is driven at step S719 based
upon the result of the above-described calculation to bring the
first image IM1 into focus.
[0387] This is followed by step S720, at which the offset DELTA
between the two images for display shown in FIG. 34 is calculated
in accordance with Equation (EQ.3) and processing for superposing
the two images is executed.
[0388] Next, at step S721, the image signal obtained at step S720,
namely the split-image coincidence image signal, is displayed on
the display unit 804.
[0389] The state of the photography switch 122 (SW2) is
discriminated at step S722. If the switch 122 is off, control
returns to step S702 so that the processing of steps S702-S721 is
executed again. If the photography switch 122 is found to be on at
step S722, it is judged that release has been performed and control
shifts to step S731.
[0390] Steps S731-S736 are for an image sensing operation identical
with that of steps S521-S526 of FIG. 24 according to the sixth
embodiment. When the processing of step S736 is completed, control
returns to step S702.
[0391] The operation of the camera according to the foregoing
flowchart will now be summarized.
[0392] When the main switch 120 and photography preparation switch
121 are turned on by the photographer, the camera performs the
rangefinding calculation and carries out autofocusing by driving
the focusing lens in a manner similar to that of the sixth
embodiment. On the basis of the results of rangefinding calculation
and the results of driving the focusing lens, the state of focusing
of the object is displayed as the amount of shift between two
images on the double-image coincidence display device. Continuous
focusing is performed by repeatedly executing this operation and
the photographer is notified of the results of focusing in the form
of the amount of offset between the twin images. Next, when the
photography switch 122 is turned on, the image of the object
projected upon the main image sensing device is recorded in the
image memory and image of the picture taken is displayed on the
display unit 804.
[0393] The eighth embodiment provides the following advantage in
addition to the advantages (AD10)-(AD14) according to the sixth
embodiment.
[0394] (AD19) The state of focusing is displayed as a coincidence
finder image on an electronic finder such as a liquid crystal
monitor. As a result, the status of focus of the image of the
object is made much more discernible.
Ninth Embodiment
[0395] According to the eighth embodiment, a photoelectric
coincidence finder is realized using the rangefinding device of the
sixth embodiment. A ninth embodiment described below illustrates a
case where the photoelectric coincidence finder is realized using
the conventional passive- or active-type rangefinding device.
[0396] FIGS. 36 through 39 are diagrams relating to the ninth
embodiment.
[0397] FIG. 36 is a diagram showing the construction of a camera
body 901 according to the ninth embodiment. Components other than
those described below operate in the same manner as set forth in
connection with the sixth embodiment of FIG. 20. Only the
components that differ will be described.
[0398] The camera body 901 has various functional components for
forming the image of an object OBJ, detecting focus and sensing the
image.
[0399] A rangefinding module 921 has two light-receiving lenses 922
of the same power spaced apart by a predetermined baselength BL for
forming images IM2, IM3 of the object OBJ whose distance is to be
measured, an infrared blocking filter 923 for blocking infrared
light and passing only visible light of the light flux that has
passed through the light-receiving lens 922, and a subordinate
image sensing device 924. The rangefinding optical system, which
includes the light-receiving lenses 922 and the infrared blocking
filter 923, forms a second image IM2 of the object OBJ and a third
image IM3 of the object OBJ on the subordinate image sensing device
924, described later.
[0400] The subordinate image sensing device 924, such as a CCD, is
a two-dimensional photoelectric sensor for photoelectrically
converting the second and third images IM2, IM3 of the object. The
distance to the object OBJ can be detected from the spacing between
images IM2, IM3 and the baselength BL using a prescribed
calculation formula.
[0401] A microcomputer 431 performs rangefinding and presents a
display on a coincidence finder in accordance with a flowchart
described below.
[0402] FIG. 37 is a diagram showing the subordinate image sensing
device 924 and the disposition of two images formed on the image
sensing device.
[0403] A light-receiving portion 925 of the subordinate image
sensing device 924 comprises m.sub.2.times.n.sub.2 light-receiving
pixels and a charge transfer portion (vertical transfer CCD) for
transferring electric charge that has accumulated in these pixels.
A horizontal transfer CCD 926 stores electric charge transferred in
the direction of arrow TRV by the vertical transfer CCD in the
light-receiving portion 925, then transfers the charge in the
direction of arrow TRH and outputs an image signal from an signal
output portion 927 to the image sensor driver 134.
[0404] The second and third images of the object described in
connection with FIG. 36 are shown at IM2 and IM3, respectively, and
the spacing VDEF between the two images varies depending upon the
object to the distance OBJ.
[0405] In accordance with a well-known correlation algorithm, the
distance V.sub.DEF of the image IM3 relative from the image IM1 is
obtained and distance DST to the object OBJ can be detected based
upon the following equation using the focal length f of the
light-receiving lens 922 and baselength BL: 2 DST = f BL ( V DEF -
BL ) (EQ.5)
[0406] FIG. 38 is a diagram illustrating the form of the display
presented on a display unit 904. An image IM1L.sub.0 from the main
image sensing device 111 is displayed over the entire display area.
A rectangular area AR centered on the display area is a twin-image
display area. An image IM1L.sub.DEF, which is obtained by
extracting the central portion of an image which is the copy of the
image IM1L.sub.0 obtained by the image sensing device 111, is
displayed in the area AR in superposition on the image IM1L.sub.0.
The images IM1L.sub.0 and IM1L.sub.DEF are displayed in a form
offset from each other by an amount DELTA calculated in accordance
with the following equation:
DELTA=K.times.(V.sub.DEF-D.sub.FOCUS) (EQ. 6)
[0407] where V.sub.DEF represents a quantity relating to the
distance to the object OBJ, D.sub.FOCUS a quantity relating to the
amount of feed of the focusing lens 152 and K a coefficient for
improving visibility by enlarging the display offset quantity.
[0408] For example, if we assume that the distance to the object
OBJ is infinity and that the amount of feed of the focusing lens
152 for focusing the object is zero, then the display image offset
quantity DELTA will be represented by the following equation, which
is similar to Equation (EQ.4) of the eighth embodiment:
DELTA=K.times.(V.sub.DEF-D.sub.FOCUS)=K.times.X(0-0)=0 (EQ.7)
[0409] If the distance to the object is finite, then values Of
V.sub.DEF and D.sub.FOCUS conforming there to are used. However, if
the object is in focus owing to feed of the focusing lens 152, then
DELTA=0 holds at this time as well.
[0410] In other words, according to the ninth embodiment, the
construction of the rangefinding module 921 and the images
superposed on each other in the twin-image display area of the
display unit 904 differ from those of the eighth embodiment.
However, as in the eighth embodiment, the offset quantity DELTA
corresponds to the amount of focal shift of the image sensing
system with respect to the object OBJ, and a finder of twin-image
coincidence type similar to that of the eighth embodiment can be
implemented.
[0411] FIG. 39 is a flowchart illustrating the flow of control by
the microcomputer 931 in a case where focus detection, focusing and
photography are carried out in the camera body 901 of the ninth
embodiment.
[0412] The control flow of FIG. 39 will be described while making
reference to FIGS. 36 through 38.
[0413] When the main switch 120 of the camera body 901 is turned
on, the microcomputer 931 is activated from the sleep state and
control proceeds from step S801 to step S802, at which the states
of the switches 121-124 inside the camera body 901 are sensed.
[0414] The state of the photography preparation switch 121 (SW1),
which is turned on by pressing the release button through its first
stroke length, is sensed at step S803. Control returns to step S802
when the switch 121 is off and proceeds to step S804 when the
switch 121 is on.
[0415] Next, at step S804, the main image sensing device 111 is
activated to acquire an image signal.
[0416] Processing of the image signal acquired at step S804 is
executed at step S805. More specifically, processing such as A/D
conversion of the image signal, white balance adjustment and gamma
correction is executed.
[0417] This is followed by step S806, at which object brightness
information is calculated from the image signal processed at step
S805. Further, in accordance with a predetermined exposure control
program, a control value for stopping down the stop 155 and the
exposure time (charge storage time) of the image sensing device 111
are calculated.
[0418] Next, the setting of the AF mode switch 123 is discriminated
at step S807 to determine if the autofocus (AF) mode is in effect.
Control jumps to step S820 if the mode is not the AF mode and
proceeds to step S811 if the mode is the AF mode.
[0419] The microcomputer 931 senses the state of the focus encoder
163 at step S811 and senses the state of the zoom encoder 165 at
step S812 to judge the current optical status of the lens.
[0420] The subordinate image sensing device 924 is activated at
step S813 to obtain image signals for rangefinding purposes.
[0421] Next, the image signals acquired at step S813 are subjected
to processing such as A/D conversion at step S814.
[0422] Next, at step S815, the position offset quantity between the
digital image signals of the images IM2 and IM3 obtained at step
S814 is calculated and so is the distance to the object.
[0423] The focusing lens group 152 is driven at step S816 based
upon the result of the above-described calculation to bring the
first image IM1 into focus.
[0424] The offset quantity DELTA between the two images for display
purposes shown in FIG. 38 is calculated in accordance with Equation
(EQ.6) at step S817.
[0425] This is followed by step S818, at which processing for
superposing the two images in the manner shown in FIG. 38 is
executed.
[0426] Next, at step S819, the image signal obtained at step S818,
namely the split-image coincidence image signal, is displayed on
the display unit 904.
[0427] The state of the photography switch 122 (SW2) is
discriminated at step S820. If the switch 122 is off, control
returns to step S802 so that the processing of steps S802-S819,
namely automatic focusing and display of images on the display
unit, is executed again. If the photography switch 122 is found to
be on at step S820, it is judged that release has been performed
and control shifts to step S831.
[0428] Steps S831-S836 are for an image sensing operation identical
with that of steps S731-S736 of FIG. 35 according to the eighth
embodiment. When the processing of step S836 is completed, control
returns to step S702.
[0429] The operation of the camera according to the foregoing
flowchart will now be summarized.
[0430] When the main switch 120 and photography preparation switch
121 are turned on by the photographer, the camera performs the
rangefinding calculation using the image signals obtained from the
rangefinding module 921 and carries out automatic focusing by
driving the focusing lens 152 based upon the results of
rangefinding calculation. On the basis of the results of
rangefinding calculation and the results of driving the focusing
lens, the state of focal shift of the image on the image sensing
device 111 is calculated. The image of the object obtained from the
image sensing device 111 and an image obtained by extracting the
central portion of an image which is a copy of the first-mentioned
image are superposed and displayed on the display unit 904 with an
offset between them that depends upon the amount of focal shift.
Continuous focusing is performed by repeatedly executing this
operation and the photographer is notified of the results of
focusing in the form of the amount of offset between the twin
images. Next, when the photography switch 122 is turned on, the
image of the object projected upon the main image sensing device is
recorded in the image memory and image of the picture taken is
displayed on the display unit 904.
[0431] The ninth embodiment provides the following advantage in
addition to the advantages (AD10)-(AD14) according to the sixth
embodiment.
[0432] (AD20) The state of focusing is displayed as a coincidence
finder image even in an image sensing apparatus having the
conventional rangefinding device and an electronic finder such as a
liquid crystal monitor. As a result, the status of focus of the
image of the object is made much more discernible through a simple,
inexpensive arrangement.
[0433] The rangefinding device in the ninth embodiment uses a
passive triangulation rangefinder according to the prior art.
However, it is possible to use a conventional active triangulation
rangefinding device or a so-called sonar-type rangefinding device,
which measures distance based upon the length of time required to
receive reflected ultrasonic waves projected toward an object.
[0434] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
* * * * *