U.S. patent application number 14/112799 was filed with the patent office on 2014-02-27 for imaging device.
The applicant listed for this patent is PANASONIC CORPORATION. Invention is credited to Takamasa Ando, Norihiro Imamura, Tsuguhiro Korenaga, Michihiro Yamagata.
Application Number | 20140055664 14/112799 |
Document ID | / |
Family ID | 48904932 |
Filed Date | 2014-02-27 |
United States Patent
Application |
20140055664 |
Kind Code |
A1 |
Yamagata; Michihiro ; et
al. |
February 27, 2014 |
IMAGING DEVICE
Abstract
An image capture device according to the present disclosure
includes: a lens optical system L; an image sensor N on which light
that has passed through the lens optical system L is incident and
which includes at least a plurality of first pixels and a plurality
of second pixels; and an array of optical elements K which is
arranged between the lens optical system and the image sensor. The
lens optical system has a first optical region D1 which transmits
mostly light vibrating in the direction of a first polarization
axis and a second optical region D2 which transmits mostly light
vibrating in the direction of a second polarization axis that is
different from the direction of the first polarization axis. The
array of optical elements makes the light that has passed through
the first optical region D1 incident on the plurality of first
pixels and also makes the light that has passed through the second
optical region D2 incident on the plurality of second pixels.
Inventors: |
Yamagata; Michihiro; (Osaka,
JP) ; Korenaga; Tsuguhiro; (Osaka, JP) ;
Imamura; Norihiro; (Osaka, JP) ; Ando; Takamasa;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PANASONIC CORPORATION |
Osaka |
|
JP |
|
|
Family ID: |
48904932 |
Appl. No.: |
14/112799 |
Filed: |
February 1, 2013 |
PCT Filed: |
February 1, 2013 |
PCT NO: |
PCT/JP2013/000563 |
371 Date: |
October 18, 2013 |
Current U.S.
Class: |
348/360 |
Current CPC
Class: |
H04N 9/04557 20180801;
G03B 11/00 20130101; H04N 9/045 20130101; G02B 5/3025 20130101;
G02B 3/0006 20130101; G01J 1/0411 20130101; G01J 1/4228 20130101;
G01J 4/04 20130101; H04N 5/23293 20130101; G01J 1/0429 20130101;
H04N 5/2254 20130101; G02B 13/22 20130101 |
Class at
Publication: |
348/360 |
International
Class: |
G02B 13/22 20060101
G02B013/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2012 |
JP |
2012-011026 |
Claims
1. An image capture device comprising: a lens optical system; an
image sensor on which light that has passed through the lens
optical system is incident and which includes at least a plurality
of first pixels and a plurality of second pixels; and an array of
optical elements which is arranged between the lens optical system
and the image sensor and which includes a plurality of optical
elements, each having a lens surface, wherein the lens optical
system has a first optical region which transmits mostly light
vibrating in the direction of a first polarization axis and a
second optical region which transmits mostly light vibrating in the
direction of a second polarization axis that is different from the
direction of the first polarization axis, and each of the optical
elements that form the array of optical elements makes the light
that has passed through the first optical region incident on the
plurality of first pixels and also makes the light that has passed
through the second optical region incident on the plurality of
second pixels.
2. The image capture device of claim 1, wherein the image sensor is
a monochrome image sensor.
3. The image capture device of claim 1, wherein the lens optical
system is an image-space telecentric optical system.
4. The image capture device of claim 1, wherein the lens optical
system includes a split polarizer having first and second
polarizing portions which are located in the first and second
regions, respectively.
5. The image capture device of claim 1, wherein the optical
elements that form the array of optical elements are a lenticular
lens.
6. The image capture device of claim 5, wherein in the image
sensor, a number of the first pixels and a number of the second
pixels are arranged in a first direction and the first pixels
arranged in the first direction and the second pixels arranged in
the first direction alternate with each other in a second direction
that intersects with the first direction at right angles, thus
forming an image capturing plane.
7. The image capture device of claim 4, wherein the lens optical
system further has a third optical region which transmits mostly
light vibrating in the direction of a third polarization axis and a
fourth optical region which transmits mostly light vibrating in the
direction of a fourth polarization axis, and the split polarizer
further has third and fourth polarizing portions which are located
in the third and fourth regions, respectively.
8. The image capture device of claim 7, wherein the optical
elements that form the array of optical elements are a micro lens
array.
9. The image capture device of claim 1, further comprising a
polarization direction changing section which changes the direction
of at least one of the first and second polarization axes of the
first and second optical regions.
10. The image capture device of claim 1, wherein the lens optical
system includes a split polarizer with at least three polarizing
portions, two adjacent ones of which have polarization axes in
mutually different directions, and the image capture device further
includes a drive mechanism which drives the split polarizer so that
any two adjacent ones of the at least three polarizing portions of
the split polarizer are located in the first and second
regions.
11. The image capture device of claim 10, wherein the split
polarizer includes a common transparent electrode, two divided
transparent electrodes which are located in the first and second
optical regions, respectively, a liquid crystal layer which is
interposed between the common transparent electrode and the two
divided transparent electrodes, and a control section which applies
mutually different voltages to the two divided transparent
electrodes.
12. (canceled)
13. The image capture device of claim 1, wherein the plurality of
first pixels includes a number of 1A pixels with filters having a
first spectral transmittance characteristic, a number of 2A pixels
with filters having a second spectral transmittance characteristic,
a number of 3A pixels with filters having a third spectral
transmittance characteristic, and a number of 4A pixels with
filters having a fourth spectral transmittance characteristic, the
plurality of second pixels includes a number of 1B pixels with
filters having the first spectral transmittance characteristic, a
number of 2B pixels with filters having the second spectral
transmittance characteristic, a number of 3B pixels with filters
having the third spectral transmittance characteristic, and a
number of 4B pixels with filters having the fourth spectral
transmittance characteristic, and the array of optical elements
includes: a plurality of first optical elements which makes light
that has passed through the first optical region incident on the 1A
and 3A pixels and which also makes light that has passed through
the second region incident on the 2B and 4B pixels; and a plurality
of second optical elements which makes light that has passed
through the first region incident on the 2A and 4A pixels and which
also makes light that has passed through the second region incident
on the 1B and 3B pixels.
14. The image capture device of claim 13, wherein on the image
capturing plane of the image sensor, the 1A, 2B, 3A and 4B pixels
that form a single set are adjacent to each other and are arranged
at the four vertices of a quadrangle, wherein the filters having
the first spectral transmittance characteristic and the filters
having the second spectral transmittance characteristic transmit
light falling within the wavelength range of the color green, the
filters having the third spectral transmittance characteristic
transmit light falling within the wavelength range of the color
red, the filters having the fourth spectral transmittance
characteristic transmit light falling within the wavelength range
of the color blue, and the 1A, 2B, 3A and 4B pixels that form a
single set are arranged in a Bayer arrangement pattern.
15. (canceled)
16. The image capture device of claim 13, wherein the plurality of
first optical elements and the plurality of second optical elements
form a lenticular lens.
17. The image capture device of claim 1, wherein the lens optical
system further includes a stop, and the first and second optical
regions are located in the vicinity of the stop.
18. An image capture device comprising: a lens optical system; an
image sensor which includes a plurality of first pixels with
filters having a first spectral transmittance characteristic, a
plurality of second pixels with filters having a second spectral
transmittance characteristic, a plurality of third pixels with
filters having a third spectral transmittance characteristic, and a
plurality of fourth pixels with filters having a fourth spectral
transmittance characteristic and in which a first row where the
first and second pixels are arranged alternately in a first
direction and a second row where the third and fourth pixels are
arranged alternately in the first direction alternate in a second
direction, thereby forming an image capturing plane, wherein light
that has passed through the lens optical system is incident on the
first, second, third and fourth pixels; and an array of optical
elements which is arranged between the lens optical system and the
image sensor, wherein the lens optical system has a first optical
region which transmits mostly light vibrating in the direction of a
first polarization axis and a second optical region which transmits
mostly light vibrating in the direction of a second polarization
axis that is different from the direction of the first polarization
axis, the first and second optical regions being arranged in the
second direction, on the image capturing plane, the array of
optical elements includes a plurality of optical elements, each of
which makes the light that has been transmitted through the lens
optical system incident on every four pixels, which are the first,
second, third and fourth pixels that are arranged adjacent to each
other in the first and second directions, and the plurality of
optical elements forms a number of columns, each of which is
arranged linearly in the second direction, wherein on two columns
that are adjacent to each other in the first direction, each
optical element on one of the two columns is shifted from an
associated optical element on the other column in the second
direction by a length corresponding to a half of one arrangement
period of the optical elements.
19. A biometric image capturing system comprising: the image
capture device of claim 7; and a light source which irradiates an
object with polarized light.
20. The biometric image capturing system of claim 19, wherein the
lens optical system of the image capture device includes split
color filters to be arranged in the first to fourth optical
regions, the split color filters transmit light falling within the
same wavelength range in two of those first through fourth optical
regions, and in the two optical regions, the polarization axes of
the split polarizer are in mutually different directions.
21. (canceled)
22. The biometric image capturing system of claim 19, further
comprising a control section which controls the light source and
the image capture device, wherein the control section controls the
image capture device so that the image capture device captures
multiple images synchronously with flickering of the light source,
and the image capture device performs arithmetic processing between
the multiple images to generate another image.
23. The biometric image capturing system of claim 19, further
comprising a display section which displays an image that has been
shot by the image capture device, wherein the image capture device
further includes a signal processing section, and the signal
processing section generates an image signal by inverting
horizontally the image shot and outputs the image signal to the
display section.
Description
TECHNICAL FIELD
[0001] The present application relates to an image capture device
such as a camera and more particularly relates to an image capture
device which captures an image using polarized light.
BACKGROUND ART
[0002] When light is reflected from the surface of an object, the
polarization property of the light changes. That is why the light
reflected from the object has its polarization property determined
by various pieces of information including the surface roughness,
reflectance, and birefringence of the object and the orientation of
the reflective surface. Thus, if light with a polarization property
is separated, detected and converted into an electrical signal,
those pieces of information can be obtained.
[0003] A shooting system of that type is generally used as means
for imaging separately light that has been reflected from the
surface of a tissue and light that has been reflected from inside
of the tissue in a camera for medical and beauty treatment purposes
such as an endoscope and a skin checker.
[0004] In order to detect light with a polarization property,
according to a conventional method, a polarizer is arranged in
front of the lens of a image capturing camera and a shooting
session is carried out with the polarizer rotated according to the
shooting condition. According to such a method, however, shooting
sessions need to be performed a number of times with the polarizer
rotated, thus taking a long time to get an image.
[0005] Thus, to overcome such a problem, some people proposed a
method for getting an image using light with a different
polarization property by arranging a polarizer having an axis of
polarization in a predetermined direction in advance on the surface
of an image sensor. For example, a Patent Document No. 1 discloses
a device in which polarization filters are provided for some of the
pixels of a solid-state image sensor. By making light with a
polarization property incident on some pixels and by performing
image processing on an image obtained from those pixels on which
the light with a polarization property has been incident and an
image obtained from other pixels, an image, from which the
influence of reflection from the surface of the subject has been
reduced, can be obtained.
[0006] Meanwhile, Patent Document No. 2 discloses an image capture
device in which an optical system is formed by an array of two
lenses and an image is shot through each of those lenses using
light with a different polarization direction, thereby detecting
the state of a dry or wet road surface.
CITATION LIST
Patent Literature
[0007] Patent Document No. 1: Japanese Laid-Open Patent Publication
No. 2006-254331 [0008] Patent Document No. 2: Japanese Laid-Open
Patent Publication No. 2010-25915
SUMMARY OF INVENTION
Technical Problem
[0009] However, there is a growing demand for an image capture
device which can obtain a plurality of images based on multiple
light beams in mutually different polarization states using a more
simplified or more general configuration than the conventional
ones.
[0010] A non-limiting exemplary embodiment of the present
application provides an image capture device which can obtain a
plurality of images based on multiple light beams in mutually
different polarization states using a simplified or general
configuration.
Solution to Problem
[0011] An image capture device according to an aspect of the
present invention includes: a lens optical system; an image sensor
on which light that has passed through the lens optical system is
incident and which includes at least a plurality of first pixels
and a plurality of second pixels; and an array of optical elements
which is arranged between the lens optical system and the image
sensor and which includes a plurality of optical elements, each
having a lens surface. The lens optical system has a first optical
region which transmits mostly light vibrating in the direction of a
first polarization axis and a second optical region which transmits
mostly light vibrating in the direction of a second polarization
axis that is different from the direction of the first polarization
axis. Each of the optical elements that form the array of optical
elements makes the light that has passed through the first optical
region incident on the plurality of first pixels and also makes the
light that has passed through the second optical region incident on
the plurality of second pixels.
Advantageous Effects of Invention
[0012] An image capture device according to an aspect of the
present invention can capture multiple images based on light beams
in mutually different polarization states while using a single lens
optical system.
[0013] In addition, by adopting the image capture device of the
present invention, a biometric image capture device, which may be
used effectively to check the skin state, for example, is
realized.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 Illustrates a configuration for a first embodiment of
an image capture device according to the present invention.
[0015] FIG. 2 A front view of a split polarizer according to the
first embodiment.
[0016] FIG. 3 A perspective view of an array of optical elements
according to the first embodiment.
[0017] FIG. 4 A schematic enlarged cross-sectional view
illustrating the array of optical elements and an image sensor
according to the first embodiment and their surrounding.
[0018] FIG. 5 A front view of a split polarizer according to a
second embodiment.
[0019] FIG. 6 A schematic perspective view illustrating an array of
optical elements and an image sensor according to the second
embodiment and their surrounding.
[0020] FIG. 7 Illustrates light rays to be incident on the image
capturing plane according to the second embodiment.
[0021] FIG. 8 Illustrates a configuration according to a third
embodiment.
[0022] FIG. 9 (a) is a front view of a split polarizer according to
the third embodiment and (b) is a front view illustrating another
example of the split polarizer.
[0023] FIG. 10 Illustrates a configuration according to a fourth
embodiment.
[0024] FIGS. 11 (a) and (b) are respectively a cross-sectional view
and a front view of a liquid crystal element according to the
fourth embodiment.
[0025] FIG. 12 A perspective view of an array of optical elements
according to a fifth embodiment.
[0026] FIGS. 13 (a) and (b) illustrate how light rays are incident
on an image sensor according to the fifth embodiment.
[0027] FIG. 14 Illustrates a general configuration for a skin
checker according to a sixth embodiment of the present
invention.
[0028] FIG. 15 (a) is a side view of an optical element Sa to be
arranged in the vicinity of the stop of a lens optical system
according to the sixth embodiment, (b-1) is a front view of split
color filters Sc, and (b-2) is a front view of a split polarizer
Sp.
DESCRIPTION OF EMBODIMENTS
[0029] The present inventors checked out the image capture devices
disclosed in Patent Documents Nos. 1 and 2. As a result, we reached
the following conclusion. Specifically, the device disclosed in
Patent Document No. 1 needs to use a dedicated image sensor with a
polarization filter. However, since such an image sensor is not
retailed, it must be manufactured as a dedicated product.
Particularly if such dedicated products are manufactured in small
quantities, the manufacturing cost is expensive. On top of that, in
that case, the arrangement of the polarizer cannot be changed
appropriately according to the shooting situation.
[0030] On the other hand, in the device disclosed in Patent
Document No. 2, an optical system is implemented as a lens array on
the image sensor. According to such an arrangement, the effective
diameter of a single optical system needs to be less than a half of
the size of the image capturing area, thus limiting the degree of
freedom of the optical design. That is why it is difficult to form
an optical system, of which the resolution is high enough to obtain
an image.
[0031] In order to overcome these problems, the present inventors
invented a novel image capture device which can obtain an image by
using light with a polarization property. An aspect of the present
invention can be outlined as follows.
[0032] An image capture device according to an aspect of the
present invention includes: a lens optical system; an image sensor
on which light that has passed through the lens optical system is
incident and which includes at least a plurality of first pixels
and a plurality of second pixels; and an array of optical elements
which is arranged between the lens optical system and the image
sensor and which includes a plurality of optical elements, each
having a lens surface. The lens optical system has a first optical
region which transmits mostly light vibrating in the direction of a
first polarization axis and a second optical region which transmits
mostly light vibrating in the direction of a second polarization
axis that is different from the direction of the first polarization
axis. Each of the optical elements that form the array of optical
elements makes the light that has passed through the first optical
region incident on the plurality of first pixels and also makes the
light that has passed through the second optical region incident on
the plurality of second pixels.
[0033] The image sensor may be a monochrome image sensor.
[0034] The lens optical system may be an image-space telecentric
optical system.
[0035] The lens optical system may include a split polarizer having
first and second polarizing portions which are located in the first
and second regions, respectively.
[0036] The optical elements that form the array of optical elements
may be a lenticular lens.
[0037] In the image sensor, a number of the first pixels and a
number of the second pixels may be arranged in a first direction
and the first pixels arranged in the first direction and the second
pixels arranged in the first direction may alternate with each
other in a second direction that intersects with the first
direction at right angles, thus forming an image capturing
plane.
[0038] The lens optical system may further have a third optical
region which transmits mostly light vibrating in the direction of a
third polarization axis and a fourth optical region which transmits
mostly light vibrating in the direction of a fourth polarization
axis. The split polarizer may further have third and fourth
polarizing portions which are located in the third and fourth
regions, respectively.
[0039] The optical elements that form the array of optical elements
may be a micro lens array.
[0040] The image capture device may further include a polarization
direction changing section which changes the direction of at least
one of the first and second polarization axes of the first and
second optical regions.
[0041] The lens optical system may include a split polarizer with
at least three polarizing portions, two adjacent ones of which have
polarization axes in mutually different directions. The image
capture device may further include a drive mechanism which drives
the split polarizer so that any two adjacent ones of the at least
three polarizing portions of the split optical element are located
in the first and second regions.
[0042] The split polarizer may include a common transparent
electrode, two divided transparent electrodes which are located in
the first and second optical regions, respectively, a liquid
crystal layer which is interposed between the common transparent
electrode and the two divided transparent electrodes, and a control
section which applies mutually different voltages to the two
divided transparent electrodes.
[0043] The image capture device may perform shooting sessions
multiple times with the voltage changed.
[0044] The plurality of first pixels may include a number of 1A
pixels with filters having a first spectral transmittance
characteristic, a number of 2A pixels with filters having a second
spectral transmittance characteristic, a number of 3A pixels with
filters having a third spectral transmittance characteristic, and a
number of 4A pixels with filters having a fourth spectral
transmittance characteristic. The plurality of second pixels may
include a number of 1B pixels with filters having the first
spectral transmittance characteristic, a number of 2B pixels with
filters having the second spectral transmittance characteristic, a
number of 3B pixels with filters having the third spectral
transmittance characteristic, and a number of 4B pixels with
filters having the fourth spectral transmittance characteristic.
The array of optical elements may include: a plurality of first
optical elements which makes light that has passed through the
first optical region incident on the 1A and 3A pixels and which
also makes light that has passed through the second region incident
on the 2B and 4B pixels; and a plurality of second optical elements
which makes light that has passed through the first region incident
on the 2A and 4A pixels and which also makes light that has passed
through the second region incident on the 1B and 3B pixels.
[0045] On the image capturing plane of the image sensor, the 1A,
2B, 3A and 4B pixels that form a single set may be adjacent to each
other and may be arranged at the four vertices of a quadrangle.
[0046] The filters having the first spectral transmittance
characteristic and the filters having the second spectral
transmittance characteristic may transmit light falling within the
wavelength range of the color green. The filters having the third
spectral transmittance characteristic may transmit light falling
within the wavelength range of the color red. The filters having
the fourth spectral transmittance characteristic may transmit light
falling within the wavelength range of the color blue. And 1A, 2B,
3A and 4B pixels that form a single set may be arranged in a Bayer
arrangement pattern.
[0047] The plurality of first optical elements and the plurality of
second optical elements may form a lenticular lens.
[0048] The lens optical system may further include a stop, and the
first and second optical regions may be located in the vicinity of
the stop.
[0049] An image capture device according to another aspect of the
present invention includes: a lens optical system; an image sensor
which includes a plurality of first pixels with filters having a
first spectral transmittance characteristic, a plurality of second
pixels with filters having a second spectral transmittance
characteristic, a plurality of third pixels with filters having a
third spectral transmittance characteristic, and a plurality of
fourth pixels with filters having a fourth spectral transmittance
characteristic and in which a first row where the first and second
pixels are arranged alternately in a first direction and a second
row where the third and fourth pixels are arranged alternately in
the first direction alternate in a second direction, thereby
forming an image capturing plane, wherein light that has passed
through the lens optical system is incident on the first, second,
third and fourth pixels; and an array of optical elements which is
arranged between the lens optical system and the image sensor. The
lens optical system has a first optical region which transmits
mostly light vibrating in the direction of a first polarization
axis and a second optical region which transmits mostly light
vibrating in the direction of a second polarization axis that is
different from the direction of the first polarization axis. The
first and second optical regions are arranged in the second
direction. On the image capturing plane, the array of optical
elements includes a plurality of optical elements, each of which
makes the light that has been transmitted through the lens optical
system incident on every four pixels, which are the first, second,
third and fourth pixels that are arranged adjacent to each other in
the first and second directions. The plurality of optical elements
forms a number of columns, each of which is arranged linearly in
the second direction. On two columns that are adjacent to each
other in the first direction, each optical element on one of the
two columns is shifted from an associated optical element on the
other column in the second direction by a length corresponding to a
half of one arrangement period of the optical elements.
[0050] A biometric image capturing system according to an aspect of
the present invention includes: an image capture device according
to any of the embodiments described above; and a light source which
irradiates an object with polarized light.
[0051] The lens optical system of the image capture device may
include split color filters to be arranged in the first to fourth
optical regions. The split color filters may transmit light falling
within the same wavelength range in two of those first through
fourth optical regions. And in the two optical regions, the
polarization axes of the split polarizer may be in mutually
different directions.
[0052] In the two optical regions, the directions of the
polarization axes of the split polarizer may intersect with each
other at substantially right angles.
[0053] The biometric image capturing system may further include a
control section which controls the light source and the image
capture device. The control section may control the image capture
device so that the image capture device captures multiple images
synchronously with flickering of the light source. And the image
capture device may perform arithmetic processing between the
multiple images to generate another image.
[0054] The biometric image capturing system may further include a
display section which displays an image that has been shot by the
image capture device. The image capture device may further include
a signal processing section. The signal processing section may
generate an image signal by inverting horizontally the image shot
and may output the image signal to the display section.
[0055] Hereinafter, embodiments of an image capture device
according to the present invention will be described with reference
to the accompanying drawings.
Embodiment 1
[0056] FIG. 1 is a schematic representation illustrating a first
embodiment of an image capture device according to the present
invention. The image capture device A of this embodiment includes a
lens optical system L, of which the optical axis is identified by
V0, an array of optical elements K which is arranged in the
vicinity of the focal point of the lens optical system L, an image
sensor N, and a signal processing section C.
[0057] In this embodiment, the lens optical system L includes a
stop S and an objective lens L1 which images light that has passed
through the stop S onto the image sensor. The lens optical system L
has a first optical region D1 and a second optical region D2. The
first and second optical regions D1 and D2 are located in the
vicinity of the stop S. The region obtained by combining these
first and second optical receives D1 and D2 together has a circular
shape corresponding to the aperture of the stop S on a cross
section which intersects with the optical axis V0 at right angles.
The boundary between the first and second optical regions D1 and D2
includes the optical axis V0 and is located on a plane which is
parallel to the horizontal direction.
[0058] The first optical region D1 of the lens optical system L is
configured to transmit mostly light vibrating in the direction of a
first polarization axis, and the second optical region D2 is
configured to transmit mostly light vibrating in the direction of a
second polarization axis that is different from the direction of
the first polarization axis.
[0059] In this embodiment, the lens optical system L includes a
split polarizer Sp which is located in the first and second optical
regions D1 and D2. FIG. 2 is a front view of the split polarizer
Sp. The split polarizer Sp divides the aperture of the stop S into
two regions by a line that includes the optical axis V0 of the lens
optical system L and that is parallel to the horizontal direction
of the image capture device, and includes a first polarizing
portion Sp1 located in the first optical region D1 and a second
polarizing portion Sp2 located in the second optical region. The
first and second polarizing regions Sp1 and Sp2 are implemented as
respective polarizers. As each of those polarizers, a so-called
"PVA iodine stretched film" which is made by dyeing polyvinyl
alcohol with iodine and stretching it into a film may be used.
[0060] The first and second polarizing sections Sp1 and Sp2 have
first and second polarization axes, respectively, and the
directions of the first and second polarization axes are different
from each other. For example, the direction of the first
polarization axis may be the vertical direction of the image
capture device, and the second polarization direction may be the
horizontal direction of the image capture device.
[0061] As shown in FIG. 1, of the light entering the stop S, the
light beam B1 enters the first polarizing portion Sp1 of the split
polarizer Sp and the light beam B2 enters the second polarizing
portion Sp2 of the split polarizer Sp. If the light entering the
stop S includes linearly polarized light rays which are polarized
in an arbitrary direction, then only linearly polarized light rays
vibrating in the direction of the first polarization axis are
transmitted through the first polarizing portion Sp1 and only
linearly polarized light rays vibrating in the direction of the
second polarization axis are transmitted through the second
polarizing portion Sp2. The light beams B1 and B2 are converged by
the objective lens L1 and incident on the array of optical elements
K.
[0062] FIG. 3 is a perspective view of the array of optical
elements K, which includes a plurality of optical elements M, each
having a lens face. In this embodiment, the lens face of each
optical element M is a cylindrical face. In this array of optical
elements K, the optical elements M are arranged vertically so that
their cylindrical faces run in the horizontal direction. In this
manner, these optical elements M form a lenticular lens.
[0063] FIG. 4 is an enlarged view of the array of optical elements
K and image sensor N shown in FIG. 1. The array of optical elements
K, implemented as a lenticular lens, is arranged so that its side
with the optical elements M faces the image sensor N. As shown in
FIG. 1, the array of optical elements K is arranged in the vicinity
of the focal point of the lens optical system L and is located at a
predetermined distance from the image sensor N. The image sensor N
includes a plurality of first pixels P1 and a plurality of second
pixels P2, which are arranged on the image capturing plane Ni. A
number of those first pixels P1 are arranged in the horizontal
direction (i.e., the first direction), so are a number of those
second pixels P2. As shown in FIG. 4, those first pixels P1 and
second pixels P2 are arranged alternately in the vertical direction
(i.e., the second direction).
[0064] In this embodiment, each and every one of the first pixels
P1 and second pixels P2 has the same shape on the image capturing
plane Ni. For example, each of the first pixels P1 and second
pixels P2 may have the same rectangular shape and may have the same
area, too.
[0065] The image sensor N may include a plurality of micro lenses
Ms, which are arranged on the image capturing plane Ni so as to
cover the surface of the respective pixels. The position at which
the array of optical elements K is arranged may be determined by
reference to the focal point of the objective lens L1, for example.
One period in the vertical direction of the cylindrical faces of
the array of optical elements K corresponds to two of the pixels
arranged on the image capturing plane Ni.
[0066] As shown in FIG. 4, the boundary between two adjacent
cylindrical faces of the array of optical elements K is level in
the horizontal direction with the boundary between two adjacent
micro lenses Ms of the image sensor N. That is to say, the array of
optical elements K and the image sensor N are arranged so that each
single optical element M of the array of optical elements K
corresponds to two rows of pixels on the image capturing plane Ni.
Each optical element M has the function of selectively determining
the outgoing direction of an incoming light ray according to its
angle of incidence. Specifically, the optical elements M makes most
of the light beam B1 that has been transmitted through the first
optical region D1 incident onto the first pixels P1 on the image
capturing plane Ni and also makes most of the light beam B2 that
has been transmitted through the second optical region D2 incident
onto the second pixels P2 on the image capturing plane Ni. This can
be done by adjusting the refractive index of the lenticular lens
used as the array of optical elements K, the radius of curvature of
the optical elements M, and the distance from the image capturing
plane Ni.
[0067] The image sensor N photoelectrically converts the incident
light and transmits an image signal Q0 to the signal processing
section C. Based on the image signal Q0, the signal processing
section C generates image signals Q1 and Q2 corresponding to the
first pixels P1 and the second pixels P2, respectively.
[0068] The image signal Q1 represents an image that has been
produced by the light beam transmitted through the first optical
region D1, while the second image signal Q2 represents an image
that has been produced by the light beam transmitted through the
second optical region D2. Since the first and second optical
regions D1 and D2 transmit light beams vibrating in the directions
of the first and second polarization axes, respectively, two images
represented by two linearly polarized light components with
mutually different polarization directions can be obtained.
[0069] These two images obtained in this manner have been shot at a
time through the single lens optical system. That is why since the
same object has been shot substantially at the same time from the
same angle, there is no significant difference between the two
images except that those two images are represented by light beams
in mutually different polarization states. However, as a light beam
coming from the object has a polarization property which is
determined by various kinds of information about the surface
roughness, reflectance and birefringence of an object and the
orientation of the reflective surface, those pieces of information
about the surface roughness, reflectance and birefringence of an
object and the orientation of the reflective surface are more
enhanced in one of the two images than in the other. As a result,
an image representing a scene under the water clearly can be
obtained with the reflection from the surface of water suppressed,
or an image representing even a center line on a wet road surface
clearly can also be obtained. On top of that, by processing the two
image signals by various known image processing techniques, images
including those pieces of information about the surface roughness,
reflectance and birefringence of an object and the orientation of
the reflective surface can be obtained.
[0070] As can be seen, the image sensor of this embodiment can
obtain two images represented by light beams with mutually
different polarization properties at a time by using a general
purpose image sensor. Since such images can be obtained by the
split polarizer which is arranged in the vicinity of the stop, a
practical resolution can be maintained without increasing the size
of the image capture device too much.
[0071] Optionally, the lens optical system L of this embodiment may
be an image-space telecentric optical system. In that case,
principal rays of light beams entering at different angles of view
can also be incident on the array of optical elements at an angle
of incidence of nearly zero degrees. As a result, crosstalk (i.e.,
incidence of light rays that should have been incident on the first
pixels P1 on the second pixels P2 or incidence of light rays that
should have been incident on the second pixels P2 on the first
pixels P1) can be reduced over the entire image sensor.
[0072] The stop S is a region through which a bundle of rays with
every angle of view passes. That is why by inserting a plane, of
which the optical property controls the polarization property, to
the vicinity of the stop S, the polarization property of a bundle
of rays with any angle of view can be controlled in the same way.
Specifically, in this embodiment, the split polarizer Sp may be
arranged in the vicinity of the stop S. By arranging the split
polarizer Sp in the optical regions D1 and D2 that are located in
the vicinity of the stop, a polarization property corresponding to
the number of the divided regions can be given to the bundle of
rays.
[0073] In FIG. 1, the split polarizer Sp is arranged at such a
position that the light that has passed through the stop S can
enter the split polarizer Sp directly (i.e., without passing
through any other optical member). Optionally, the split polarizer
Sp may be arranged closer to the object than the stop S is. In that
case, the light that has passed through the split polarizer Sp may
enter the stop S directly (i.e., without passing through any other
optical member). In the case of an image-space telecentric optical
system, the angle of incidence of a light ray at the focal point of
the optical system is determined unequivocally by the position of
the light ray that passed through the stop S. Also, the array of
optical elements K has the function of selectively determining the
outgoing direction of an incoming light ray according to its angle
of incidence. That is why the bundle of rays can be distributed
onto pixels on the image capturing plane Ni so as to correspond to
the optical regions D1 and D2 which are divided in the vicinity of
the stop S.
[0074] On the other hand, in the case of an image-space
non-telecentric optical system, the angle of incidence of a light
ray at the focal point of the optical system is determined
unequivocally by the position of the light ray that passed through
the stop S and the angle of view.
Embodiment 2
[0075] A second embodiment of an image capture device according to
the present invention will be described. In the image capture
device of this embodiment, the lens optical system has first
through fourth optical regions and micro lenses are arranged as an
array of optical elements, unlike the image capture device of the
first embodiment. Thus, the following description of this
embodiment will be focused on these differences from the first
embodiment.
[0076] In this embodiment, the lens optical system L has a first
optical region which transmits mostly light vibrating in the
direction of a first polarization axis, a second optical region
which transmits mostly light vibrating in the direction of a second
polarization axis that is different from the direction of the first
polarization axis, a third optical region which transmits mostly
light vibrating in the direction of a third polarization axis, and
a fourth optical region which transmits mostly light vibrating in
the direction of a fourth polarization axis. FIG. 5 illustrates an
example of a split polarizer Sp to be arranged in these four
optical regions. The split polarizer Sp shown in FIG. 5 is viewed
from the object side. The split polarizer Sp has first, second,
third and fourth polarizing portions Sp1, Sp2, Sp3 and Sp4 which
are located in the first, second third and fourth optical regions
D1, D2, D3 and D4, respectively.
[0077] The boundary between the first and second optical regions D1
and D2 and the boundary between the third and fourth optical
regions D3 and D4 are located on a plane which includes the optical
axis V0 of the lens optical system L and which is parallel to the
horizontal direction of the image capture device. On the other
hand, the boundary between the first and fourth optical regions D1
and D4 and the boundary between the second and fourth optical
regions D2 and D4 are located on a plane which includes the optical
axis V0 of the lens optical system L and which is parallel to the
vertical direction of the image capture device.
[0078] The direction of the third polarization axis may be either
different from the directions of the first and second polarization
axes or the same as the direction of the first or second
polarization axis. Likewise, the direction of the fourth
polarization axis may be either different from, or the same as, the
directions of the first and second polarization axes. That is to
say, any two of the first, second, third and fourth polarizing
portions Sp1, Sp2, Sp3 and Sp4 need to have mutually different
polarization directions. Also, if the directions of the first
through fourth polarization axes are different from each other,
then the directions of the first through fourth polarization axes
may be three directions that define angles of 45, 90 and 135
degrees with respect to one direction, for example.
[0079] FIG. 6 is a partially cutaway perspective view of the array
of optical elements K and image sensor N. In this embodiment, the
optical elements M of the array of optical elements K are micro
lenses, and the lens surface is a spherical one. The optical
elements M are arranged periodically in vertical and horizontal
directions, thereby forming a micro lens array. The image sensor N
is arranged so as to face the array of optical elements K. Each of
the pixels on the image capturing plane Ni of the image sensor N is
provided with a micro lens Ms. One period of the optical elements M
of the array of optical elements K is set to be twice as long as
one period of the micro lenses Ms of the image capture device N
both horizontally and vertically. That is why a single optical
element M of the array of micro lenses that form the array of
optical elements K is associated with four pixels on the image
capturing plane Ni.
[0080] FIG. 7 illustrates relations between pixels arranged on the
image capturing plane of the image sensor N and light rays that
have been transmitted through the four optical regions of the lens
optical system L. The image sensor N includes a plurality of first
pixels P1, a plurality of second pixels P2, a plurality of third
pixels P3 and a plurality of fourth pixels P4, all of which are
arranged on the image capturing plane Ni. As shown in FIG. 7, on
the image capturing plane Ni, the second and third pixels P2 and P3
are arranged horizontally alternately, and the first and fourth
pixels P1 and P4 are arranged horizontally alternately. The rows on
which the second and third pixels P2 and P3 are arranged and the
rows on which the first and fourth pixels P1 and P4 are arranged
alternate so that the first and second pixels P1 and P2 are
vertically adjacent to each other. Thus, the first, second third
and fourth pixels P1, P2, P3 and P4 are arranged so as to be
adjacent to each other in the row and column directions, and each
set of those four pixels corresponds to a single optical element M
of the micro lens array.
[0081] A light ray that has been transmitted through the first
polarizing portion Sp1 in the first optical region D1 is converged
by the lens optical system L and then incident on the first pixel
P1 through an optical element M of the array of optical elements K.
In the same way, light rays that have been transmitted through the
second, third and fourth polarizing portions Sp2, Sp3 and Sp4 in
the second, third and fourth optical regions D2, D3 and D4 are
incident on the second, third and fourth pixels P2, P3 and P4,
respectively. That is to say, light rays that have been transmitted
through each optical region are incident on the same kind of pixels
which are located every other row in the horizontal direction and
every other column in the vertical direction on the image capturing
plane Ni.
[0082] The image sensor N photoelectrically converts the incident
light on a pixel-by-pixel basis and outputs a signal thus obtained
to the signal processing section C, which processes the signals
obtained from the first, second, third and fourth pixels P1, P2, P3
and P4 on each kind of pixels basis, thereby generating image
signals. Specifically, by processing the signals obtained from a
number of first pixels P1, the signal processing section C
generates an image signal Q1. In the same way, by processing
signals obtained from a number of second pixels P2, signals
obtained from a number of third pixels P3, and signals obtained
from a number of fourth pixels P4, the signal processing section C
generates image signals Q2, Q3 and Q4, respectively.
[0083] The image signals Q1, Q2, Q3 and Q4 thus obtained represent
Images #1, #2, #3 and #4 of the same scene which have been shot at
the same time through a single lens system. However, these Images
#1, #2, #3 and #4 have been generated based on light beams in
mutually different polarization states. That is why these Images
#1, #2, #3 and #4 include various pieces of information about the
surface roughness, reflectance and birefringence of an object and
the orientation of the reflective surface due to their difference
in polarization property. In this manner, according to this
embodiment, images in four different polarization states can be
shot by performing a shooting session only once.
Embodiment 3
[0084] A third embodiment of an image capture device according to
the present invention will be described. FIG. 8 is a schematic
representation illustrating an image capture device according to
this third embodiment. The image capture device of this embodiment
further includes a polarization direction changing section which
changes the direction of at least one of the first and second
polarization axes of the first and second optical regions, which is
a major difference from the image capture device of the first
embodiment. More specifically, in this embodiment, the split
polarizer Sp is a switching type split polarizer Sp which can
change the directions of the first and second polarization axes of
the first and second optical regions, and includes, as the
polarization direction changing section, a drive mechanism U to
change the direction of the polarization axes and a control section
V which controls the operation of the drive mechanism U. Thus, the
following description of this third embodiment will be focused on
these differences from the first embodiment.
[0085] The switching type split polarizer Sp of this embodiment has
least three polarizing portions, two adjacent ones of which have
polarization axes in mutually different directions. FIG. 9(a)
illustrates an example of such a split polarizer Sp. The split
polarizer Sp shown in FIG. 9 has first through eighth polarizing
portions Sp1 through Sp8, which all have a fan shape and which are
arranged around the center of rotation S0. The polarization axes of
the first through eighth polarizing portions Sp1 through Sp8 are
defined so that the polarization axes are different from each other
at least between adjacent polarizing portions with respect to the
boundary between them, for example.
[0086] In accordance with a signal supplied from the control
section V, the drive mechanism U rotates the split polarizer Sp on
the center of rotation S and stops rotating the split polarizer Sp
at a position where the boundary between adjacent polarizing
portions overlaps with the optical axis V0 of the lens optical
system L. In this manner, two polarizing portions with mutually
different polarization axis directions can be arranged in the first
and second optical regions D1 and D2. In addition, since the
polarizing portions to be arranged in the first and second optical
regions D1 and D2 can be selected from the first through eighth
polarizing portions Sp1 through Sp8, the polarization axis
directions in the first and second optical regions D1 and D2 can be
selected arbitrarily from a predetermined combination.
[0087] According to such a configuration, by selecting arbitrary
polarizing portions according to the condition on which the object
needs to be shot, the polarization axis directions in the first and
second optical regions D1 and D2 can be switched. As a result,
polarized images can be shot adaptively to an even broader range of
shooting environments.
[0088] The switching type split polarizer does not have to have the
configuration shown in FIG. 9(a) but may also be modified in
various manners. For example, first through seventh polarizing
portions Sp1 through Sp7 may be arranged linearly as shown in FIG.
9(b) and the drive mechanism U may move the polarizing portions in
the direction in which they are arranged. Also, although the drive
mechanism U and the control section V can change the polarization
axis directions of the first and second optical regions D1 and D2
according to this embodiment, one of these two polarization axis
directions does not have to be changed. Specifically, even though
the polarizing portions to be arranged in the first and second
optical regions D1 and D2 are switched by the drive mechanism in
this embodiment, the polarizing portion arranged in one of the
first and second optical regions D1 and D2 may be fixed and only
the polarizing portion to be arranged in the other by the drive
mechanism may be switched.
Embodiment 4
[0089] A fourth embodiment of an image capture device according to
the present invention will be described. The image capture device
of this embodiment can also change the directions of the first and
second polarization axes of the first and second optical regions,
which is a major difference from the image capture device of the
first embodiment. More specifically, in this embodiment, the split
polarizer is comprised of a liquid crystal element and a control
section which functions as the polarization direction changing
section. Thus, the following description of this fourth embodiment
will be focused on these differences from the first embodiment.
[0090] FIG. 10 illustrates a configuration for an image capture
device according to this embodiment. The image capture device shown
in FIG. 10 includes a liquid crystal element W and a control
section V as a split polarizer.
[0091] FIG. 11(a) is a cross-sectional view generally illustrating
the structure of the liquid crystal element W and FIG. 11(b) is a
front view thereof. The liquid crystal element W includes a common
transparent electrode EC, a liquid crystal layer LC, divided
transparent electrodes ED1, ED2 and a polarizing plate PL.
[0092] The common transparent electrode EC is arranged on a glass
substrate H1 with an alignment film T1, thus forming a substrate
SB1. On the other hand, the divided transparent electrodes ED1 and
ED2 are arranged on a glass substrate H2 with an alignment film T2.
On the other side of the substrate SB2 with no divided transparent
electrodes ED1, ED2, arranged is the polarizing plate PL, which has
a polarization axis and which transmits light vibrating in the
direction of the polarization axis. The alignment direction of the
alignment film T2 agrees with the polarization axis of the
polarizing plate PL. The liquid crystal layer LC is interposed
between the two substrates SB1 and SB2 that are bonded together
with a seal member J.
[0093] As shown in FIG. 11(b), the divided transparent electrodes
ED1 and ED2 are arranged so that their boundary agrees with the
horizontal direction that passes through the optical axis V0 of the
lens optical system L. In this manner, the divided transparent
electrodes ED1 and ED2 are arranged in the first and second optical
regions D1 and D2, respectively. The control section V applies a
voltage to between the common transparent electrode EC and the
divided transparent electrodes ED1, ED2.
[0094] The liquid crystal layer LC has an optical rotatory
characteristic and comes to have an angle of optical rotation
according to the voltage applied between the common transparent
electrode EC and the divided transparent electrodes ED1, ED2. For
example, the liquid crystal layer LC may have an angle of optical
rotation of 90 or 180 degrees according to the voltage applied.
That is why if the voltages applied to the divided transparent
electrodes ED1 and ED2 are different, then the liquid crystal layer
LC interposed between the common transparent electrode EC and the
divided transparent electrode ED1 and the liquid crystal layer LC
interposed between the common transparent electrode EC and the
divided transparent electrode ED2 come to have different angles of
rotation of light.
[0095] The light beam that has entered this liquid crystal element
W has its polarization direction rotated due to the optical
rotatory characteristic of the liquid crystal layer LC and then is
incident on the polarizing plate PL. In this case, the angle of
optical rotation, i.e., the angle of rotation of the polarization
axis, varies according to the voltage applied by the control
section V to the divided transparent electrodes ED1 and ED2, as
described above. The polarizing plate PL transmits only a component
of the light transmitted through the liquid crystal layer LC if the
component is a linearly polarized light ray that is parallel to the
polarization axis of the polarizing plate PL. As a result, only a
linearly polarized light ray that has rotated to the angle of
optical rotation to be determined by the voltages applied to the
divided transparent electrodes ED1 and ED2 and that vibrates in the
same direction as the polarization axis of the polarizing plate PL
is transmitted through the liquid crystal element W and detected at
the image sensor N. That is why the polarization direction of the
light ray going out of the liquid crystal element W is the same, no
matter whether the light ray has been transmitted through the
divided transparent electrode ED1 or the divided transparent
electrode ED2. However, since those light rays have rotated to
different angles of optical rotation through the liquid crystal
layer LC, the polarization directions of the light rays going out
of the liquid crystal element W and incident on the lens optical
system L are different between the divided transparent electrodes
ED1 and ED2, i.e., between the first and second optical regions D1
and D2. That is to say, by making the linearly polarized light rays
to be transmitted through the divided transparent electrodes ED1
and ED2 have mutually different polarization axis directions and by
regulating the voltage applied, their polarization directions can
be changed substantially.
[0096] As can be seen, according to this embodiment, two images
represented by light beams in mutually different polarization
states can be obtained at a time. In addition, since the angle of
optical rotation of the liquid crystal layer LC can be adjusted by
regulating the applied voltage, the polarization condition of the
light representing the image can be changed according to the
shooting environment. Consequently, the image capture device of
this embodiment can cope with an even broader range of shooting
environments.
[0097] In addition, since the polarization axis of the split
polarizer can be switched without using any mechanical driving
section, the switching operation can get done at high speeds.
Therefore, it is possible to perform a shooting session under a
predetermined polarization condition and then perform another
shooting session for a short time under a different polarization
condition. For example, if an organism needs to be shot in three or
more different polarization states, the number of images obtained
can be twice as large as the number of times of shooting sessions
by performing the shooting sessions a number of times at short
intervals.
[0098] Although the liquid crystal element includes two divided
transparent electrodes in the embodiment described above, the
liquid crystal element may also include four divided transparent
electrodes to be arranged in four optical regions as in the second
embodiment described above. In that case, micro lenses may be used
as the array of optical elements as in the second embodiment
described above. Then, four images represented by light beams in
four different polarization states can be obtained.
Embodiment 5
[0099] A fifth embodiment of an image capture device according to
the present invention will be described. In the image capture
device of this embodiment, the image sensor is a color image sensor
with an arrangement of pixels on which color filters are arranged
in a Bayer arrangement, and the array of optical elements K is a
lenticular lens with a different shape from its counterpart of the
first embodiment, which are major differences from the image
capture device of the first embodiment. Thus, the following
description of this fifth embodiment will be focused on these
differences from the first embodiment.
[0100] In a color image sensor with a Bayer arrangement, pixels are
arranged to form a tetragonal lattice, and pixels with green color
filters (having first and second spectral transmittance
characteristics), among those pixels, are arranged so as to be
diagonally adjacent to each other and have a density that is
approximately a half as high as that of all pixels. On the other
hand, pixels with red and blue color filters (having third and
fourth spectral transmittance characteristics) are arranged evenly
as a density that is a half as high as that of the green pixels.
More specifically, although there are green pixels on each row and
each column (i.e., both on odd- and even-numbered columns and on
odd- and even-numbered rows), red and blue pixels are present on
either odd- or even-numbered columns and on either odd- or
even-numbered rows. That is why if the array of optical elements K
has the same structure as the counterpart of the first embodiment
(i.e., implemented as a lenticular lens), information about the
color blue is missing from one of the two images represented by
light beams that have been transmitted through the first and second
optical regions D1 and D2 and information about the color red is
missing from the other image.
[0101] Thus, to achieve the same effect as in the first embodiment
even when such a color image sensor with a Bayer arrangement is
used, the shape of the array of optical elements K is modified
according to this embodiment. FIG. 12 is a perspective view
illustrating the array of optical elements K according to this
embodiment as viewed from the image side. This array of optical
elements K includes a plurality of optical elements M1 and M2. In
each set of optical elements M1, M2, a number of cylindrical
lenses, each running horizontally (i.e., in the first direction),
are arranged vertically (i.e., in the second direction) linearly.
Each set of those optical elements M1, M2 forms a column running
vertically, and columns of the optical elements M1 and columns of
the optical elements M2 are alternately arranged horizontally. In a
column of optical elements M1 and a column of optical elements M2
which are horizontally adjacent to each other, each optical element
on one column is vertically shifted from an associated optical
element on the other column by a length corresponding to a half of
one vertical arrangement period.
[0102] Each of these optical elements M1 and M2 is associated with
four pixels with red, blue and green filters, which are arranged in
a Bayer arrangement pattern to form the image capturing plane of
the image sensor, and makes the light that has been transmitted
through the lens optical system L incident on four pixels that face
the optical element. That is to say, the cylindrical surface that
is the lens surface of each optical element M1, M2 has one period
corresponding to two pixels of the image sensor N both vertically
and horizontally. That is why in two horizontally adjacent columns
of optical elements M1 and M2, each optical element on one column
is vertically shifted by one pixel from an associated optical
element on the other column.
[0103] As in the first embodiment, thanks to the action of the
lenticular lens consisting of these optical elements M1 and M2,
light rays that have been transmitted through the first and second
optical regions D1 and D2 are incident on mutually different
pixels. An optical element on one column of optical elements M1 is
vertically shifted by a half period from an associated optical
element on an adjacent column of optical elements M2. That is why
the light rays coming from the first and second optical regions D1
and D2 are incident on the pixels of the image sensor with odd- and
even-numbered rows changed every two pixels.
[0104] FIGS. 13(a) and 13(b) are schematic representations
illustrating light rays incident on the image capturing plane Ni of
the image sensor N of this embodiment. In FIGS. 13(a) and 13(b),
pixels to which the light rays transmitted through the first
optical region D1 are led are shown in FIG. 13(a) and pixels to
which the light rays transmitted through the second optical region
D2 are led are shown in FIG. 13(b) for the sake of simplicity.
[0105] As shown in these drawings, on each column of optical
elements M1, the optical elements M1 lead the light rays coming
from the first optical region D1 onto green (G1) pixels P1A and red
(R) pixels P3A and also leas the light rays coming from the second
optical region D2 onto green (G2) pixels P2B and blue (B) pixels
P4B. On the other hand, on each column of optical elements M2, the
optical elements M2 lead the light rays coming from the first
optical region D1 onto green (G2) pixels P2A and blue (B) pixels
P4A and also leas the light rays coming from the second optical
region D2 onto green (G1) pixels P1B and red (R) pixels P3B.
[0106] The signal processing section C receives signals from the
pixels of the image sensor N on which the light rays coming from
the first optical region D1 have been incident (as shown in FIG.
13(a)) and signals from the pixels on which the light rays coming
from the second optical region D2 have been incident (as shown in
FIG. 13(b)) and processes those two groups of signals separately
from each other, thereby generating two images. The signals
received from the pixels on which the light rays coming from the
first optical region D1 have been incident (as shown in FIG. 13(a))
and the signals received from the pixels on which the light rays
coming from the second optical region D2 have been incident (as
shown in FIG. 13(b)) each include signals received from the red,
blue and green pixels. As a result, color images generated by light
rays in mutually different polarization states can be obtained.
[0107] As can be seen from FIGS. 13(a) and 13(b), the light rays
led by the columns of optical elements M1 are not incident on the
green (G2) pixels P2A and blue (B) pixels P4A among the pixels on
which the light rays coming from the first optical region D1 are
incident (see FIG. 13(a)). In the same way, the light rays led by
the columns of optical elements M2 are not incident on the green
(G1) pixels P1A and red (R) pixels P3A. That is why when the signal
processing section C processes the signals received from the pixels
on which the light rays coming from the first optical region D1
have been incident as shown in FIG. 13(a), signals of two missing
ones of the four pixels associated with each column of optical
elements M1 may be interpolated with signals of two pixels
associated with an adjacent column of optical elements M2. In the
same way, when the signal processing section C processes the
signals received from the pixels on which the light rays coming
from the second optical region D2 have been incident as shown in
FIG. 13(b), signals of two missing ones of the four pixels
associated with each column of optical elements M1 may be
interpolated with signals of two pixels associated with an adjacent
column of optical elements M2.
[0108] Even though the image sensor is supposed to be a color image
sensor with a Bayer arrangement in the embodiment described above,
pixels with green filters may be vertically adjacent to each other
in each set of four pixels. Also, although the image sensor is
supposed to include pixels with red, blue and green filters in the
embodiment described above, the image sensor may also include
pixels with filters in the complementary colors of these colors.
For example, in the image sensor, red, blue, green and white
filters, red, blue, green and yellow filters, or any other
appropriate combination of filters may be provided for each set of
four pixels.
Embodiment 6
[0109] An embodiment of a skin checker will be described as an
exemplary biometric image capturing system that uses an image
capture device according to the present invention. FIG. 14
illustrates a general configuration for a skin checker as a sixth
embodiment of the present invention. The skin checker of this
embodiment includes a light source Ls to illuminate an object Ob,
an image capture device A, a display section Y to display an image
shot, and a control section which controls all of these.
[0110] In the image capture device A, the lens optical system
includes an optical element Sa including a split polarizer and
split color filters, which is a difference from the image capture
device of the second embodiment. FIG. 15 illustrates a
configuration for the optical element Sa to be arranged in the
vicinity of the stop of the lens optical system. FIG. 15(a) is a
side view. The optical element Sa includes the split polarizer Sp
that has already been described for the second embodiment and split
color filters Sc adjacent to the split polarizer Sp. FIG. 15(b-1)
is a front view of the split color filters Sc. There are four
optical regions D1 to D4 which are arranged around the optical axis
V0. A filter which mainly transmits light falling within the color
red wavelength range is arranged in the optical region D1. A filter
which mainly transmits light falling within the color green
wavelength range is arranged in the optical region D2. And a filter
which mainly transmits light falling within the color blue
wavelength range is arranged in the optical regions D3 and D4. FIG.
15(b-2) is a front view of the split polarizer Sp. There are four
optical regions D1 to D4 which are arranged around the optical axis
V0. The polarized light transmission characteristics of these
regions can be adjusted independently of each other by control
means (not shown). For example, the split polarizer Sp may be
configured so that polarizers with different polarized light
transmission characteristics (such as the directions of their
polarization axes) are readily attachable and removable to/from
these optical regions D1 to D4.
[0111] A polarizer is arranged at the light source Ls to make the
light source Ls emit mainly light with a predetermined polarization
direction.
[0112] The light reflected from skin is a mixture of components of
the light that has been reflected from the surface of the skin and
components of the light that has been reflected from inside of the
skin and that is affected by scattering. Of these two kinds of
light, the light reflected from the surface of the skin comes back
while keeping the polarization direction of the light source. On
the other hand, the light that has been reflected from inside of
the skin and affected by scattering no longer keeps the
polarization direction of the light source.
[0113] In observing skin, if the surface wrinkles or texture of the
skin needs to be checked, then the skin observation may be carried
out with the polarization directions of the illumination source and
the shooting optical system matched to each other by taking
advantage of such a characteristic. On the other hand, if spots
under the skin surface need to be checked, then the shooting
session may be carried out with the polarization directions of the
illumination source and the shooting optical system left different
from each other.
[0114] In this case, when spots are going to be observed, the
shorter the wavelength range, the better. That is why it is
recommended that the spots be observed with light falling within
the color blue wavelength range. Likewise, wrinkles and surface
texture can also be observed better with light falling within the
color blue wavelength range. That is why the object Ob is suitably
shot with light falling within the color blue wavelength range and
having two different pieces of polarization information. Thus, in
the split polarizer Sp shown in FIG. 15, the optical region D3 of
the split polarizer Sp corresponding to the optical region D3 of
the split color filters Sc which mainly transmits light falling
within the color blue wavelength range has such a polarization
property as to mainly transmit polarized light, of which the
polarization axis is substantially parallel to that of polarized
light mainly emitted from the light source Ls. Likewise, the
optical region D4 of the split polarizer Sp corresponding to the
optical region D4 which mainly transmits light falling within the
color blue wavelength range has such a polarization property as to
mainly transmit polarized light, of which the polarization axis
intersects at substantially right angles with that of polarized
light mainly emitted from the light source Ls. On the other hand,
the optical regions D1 and D2 of the split polarizer Sp
corresponding to the optical regions D1 and D2 of the split color
filters Sc that mainly transmit light falling within the colors
green and red wavelength ranges, respectively, have such a
polarization property as to mainly transmit polarized light, of
which the polarization axis defines a tilt angle of 45 degrees with
respect to the polarization axis of the polarized light mainly
emitted from the light source Ls.
[0115] Consequently, an image which allows the viewer to observe
the skin wrinkles and texture easily can be obtained based on the
light that has been transmitted through the optical region D3 of
the split polarizer Sp. On the other hand, an image which allows
the viewer to observe the skin spots more easily can be obtained
based on the light that has been transmitted through the optical
region D4 of the split polarizer Sp.
[0116] Furthermore, components of light reflected from the surface
of the skin and components of light reflected from inside of the
skin and affected by scattering can be both obtained based on the
light that has been transmitted through the optical regions D1 and
D2 of the split polarizer Sp.
[0117] It should be noted that the polarization axis of the optical
regions D1 and D2 does not have to define a tilt angle of 45
degrees with respect to the polarization axis of the light emitted
from the light source Ls. Rather the direction of the polarization
axis of the optical regions D1 and D2 may be adjusted appropriately
depending on how the region of interest is irradiated with the
light. For example, in a general shooting situation, there should
be not only the light source of the skin checker but also other
kinds of environmental light such as a room light and sunlight.
That is why if the direct reflection of such environmental light is
reduced by appropriately adjusting the polarization axis direction
of the shooting optical system, the shooting condition can be
further improved.
[0118] By synthesizing together the images produced by the light
beams that have been transmitted through the optical regions D1 and
D2 and that fall within the colors green and red wavelength ranges
and the image produced by the light beams that have been
transmitted through the optical regions D3 and D4 and that fall
within the color blue wavelength range, a color observed image
representing the skin can be obtained. These images are synthesized
together by the signal processing section C of the image capture
device A (see FIG. 1).
[0119] The image that has been shot by the image capture device A
is subjected to appropriate image processing by the signal
processing section C and then presented on the display section Y.
In this case, if the signal processing section C performs
horizontally inverting processing on the image, a mirror image of
the object Ob is presented on the display section Y with its right
and left portions inverted. By displaying such an inverted image
when a person who is the object is observing his or her own skin,
the display section can function as a mirror. As a result, the skin
checker of this embodiment can be used as a sort of electronic
mirror that can display spots, wrinkles and so on effectively. The
skin checker suitably performs such a display operation just like a
mirror does, because he or she can recognize his or her spots or
wrinkles intuitively in that case while doing a makeup or
skincare.
[0120] As described above, by adopting the configuration of this
embodiment, a skin checker which allows the user to observe his or
her own skin spots, wrinkles and texture efficiently and which can
obtain a color skin image at the same time is realized.
[0121] The image capture device of this embodiment can
appropriately adjust the directions of the polarization axes of the
respective optical regions D1 through D4 of the split polarizer Sp,
and therefore, can arrange the light source Ls appropriately with
the influence of environmental light taken into account and set the
polarization directions of the split polarizer Sp according to the
position of the light source before actually starting to carry out
shooting. As a result, an image can be shot with the influence of
environmental light further reduced.
[0122] Also, under a shooting environment to be seriously affected
by environmental light, the influence of the environmental light
can be reduced by carrying out shooting synchronously with
flickering of the light source Ls. For example, in that case, the
difference between an image captured with the light source Ls
turned ON and an image captured with the light source Ls turned OFF
may be calculated and spots or wrinkles may be checked using the
differential image.
[0123] In the embodiment described above, of the four optical
regions D1 to D4 of the split polarizer Sc, the optical regions D3
and D4 are supposed to transmit a light beam falling within the
color blue wavelength range. However, the wavelength range of the
light beam to be transmitted through the two optical regions does
not have to be the color blue wavelength range. For example, two
optical regions may transmit a light beam falling within the color
green wavelength range and the other two optical regions may
transmit a light beam falling within the color blue wavelength
range and a light beam falling within the color red wavelength
range, respectively. Such a configuration may be adopted if
considering the spectrum distribution of the light source Ls and
the spectral sensitivity of the photodiode, it is more advantageous
to use a light beam falling within the color green wavelength range
rather than a light beam falling within the color blue wavelength
range in order to observe skin spots, wrinkles or texture.
Other Embodiments
[0124] In the embodiments described above, the lens optical system
L is supposed to be a single lens. However, the lens optical system
may include a compound lens which is a combination of multiple
lenses. By using such a compound lens, the optical system can be
designed with an increased degree of freedom, and an image with a
high resolution can be obtained, which is beneficial.
[0125] Optionally, to allow the array of optical elements to split
incoming light into multiple light rays as intended, the lens
optical system may have image-space telecentricity. However, even
if the lens optical system does not have image-space
telecentricity, the incoming light can also be split into multiple
light rays just as intended by appropriately adjusting one period
of the array of optical elements (such as a lenticular lens or a
micro lens array) arranged in front of the image sensor according
to the angle of emittance of an off-axis principal ray of the lens
optical system.
[0126] In the embodiment described above, the image capture device
is supposed to include a signal processing section C. However, an
image capture device according to the present invention does not
have to include the signal processing section C. In that case, the
output signal of the image sensor may be transmitted to an external
device such as a personal computer so that the arithmetic
processing that should have been done by the signal processing
section C is carried out by the external device instead. That is to
say, the present invention may be implemented as a system including
the image capture device with the lens optical system L, the array
of optical elements K and the image sensor N and an external signal
processor.
INDUSTRIAL APPLICABILITY
[0127] An image capture device according to the present disclosure
can be used effectively as an industrial camera such as a product
inspecting camera, a surveillance camera, and an image input camera
for information terminals or robots. In addition, the image capture
device of the present disclosure may also be used in a digital
still camera or a digital camcorder as well.
REFERENCE SIGNS LIST
[0128] A image capture device [0129] L lens optical system [0130]
L1 objective lens [0131] Ls light source [0132] V0 optical axis of
lens optical system L [0133] D1, D2, D3, D4 optical region [0134] S
stop [0135] Sp split polarizer [0136] K array of optical elements
[0137] M, M1, M2 optical element [0138] N image sensor [0139] Ni
image capturing plane [0140] Ms micro lens [0141] Ob object [0142]
P1 to P4 pixel [0143] C signal processing section [0144] V control
section [0145] U drive mechanism [0146] W liquid crystal element
[0147] EC common transparent electrode [0148] ED1, ED2 divided
transparent electrode [0149] LC liquid crystal layer [0150] PL
polarizer [0151] SB1, SB2 substrate [0152] H1, H2 glass substrate
[0153] J seal member [0154] T1, T2 alignment film [0155] P1A to P4A
pixel [0156] P1B to P4AB pixel [0157] Y display section
* * * * *