U.S. patent application number 12/538310 was filed with the patent office on 2014-06-05 for system and method for binary focus in night vision devices.
This patent application is currently assigned to ITT MANUFACTURING ENTERPRISES, INC.. The applicant listed for this patent is BLAIR REUBEN DOBBIE. Invention is credited to BLAIR REUBEN DOBBIE.
Application Number | 20140153085 12/538310 |
Document ID | / |
Family ID | 43824228 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140153085 |
Kind Code |
A1 |
DOBBIE; BLAIR REUBEN |
June 5, 2014 |
SYSTEM AND METHOD FOR BINARY FOCUS IN NIGHT VISION DEVICES
Abstract
Focusing devices and methods for controlling a focal position of
an objective lens assembly in a night vision optical device are
provided. The focusing device includes an objective lens assembly
positioned at a first or second focus position from an imaging
device and a binary focus controller, coupled to the objective lens
assembly, configured to translate the objective lens assembly
relative to the imaging device to either the first or second focus
position. The objective lens assembly is translated to either the
first or second focus position in response to an orientation of the
night vision optical device.
Inventors: |
DOBBIE; BLAIR REUBEN;
(ROANOKE, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOBBIE; BLAIR REUBEN |
ROANOKE |
VA |
US |
|
|
Assignee: |
ITT MANUFACTURING ENTERPRISES,
INC.
WILMINGTON
DE
|
Family ID: |
43824228 |
Appl. No.: |
12/538310 |
Filed: |
August 10, 2009 |
Current U.S.
Class: |
359/356 |
Current CPC
Class: |
G02B 7/287 20130101;
G02B 23/125 20130101; G02B 7/09 20130101; G02B 23/00 20130101; G02B
7/28 20130101; G02B 7/08 20130101 |
Class at
Publication: |
359/356 |
International
Class: |
G02B 7/09 20060101
G02B007/09 |
Claims
1. A focusing device for use with a night vision optical device,
the focusing device comprising: an objective lens assembly
positioned at a first or second focus position from an imaging
device; and a binary focus controller, coupled to the objective
lens assembly, configured to translate the objective lens assembly
relative to the imaging device to either the first or second focus
position, wherein the objective lens assembly is translated to
either the first or second focus position in response to an
orientation of the night vision optical device, the binary focus
controller includes a line of sight (LOS) sensor coupled to the
night vision optical device, the LOS sensor configured to determine
a tilt angle of the night vision optical device relative to a
horizontal LOS, the tilt angle corresponding to the orientation of
the night vision optical device, the LOS sensor includes a pendulum
mass coupled to the night vision optical device via a pendulum arm,
the pendulum arm rotating responsive to the orientation of the
night vision optical device, wherein the tilt angle is determined
based on a rotation of the pendulum arm, and a tilt angle detector
including: a potentiometer having first and second terminals
coupled to a voltage source, a wiper of the potentiometer coupled
to the pendulum arm and an output terminal, wherein an output
voltage at the output terminal is varied due to rotation of the
wiper coupled to the pendulum arm, and the tilt angle is determined
based on the output voltage.
2. A focusing device according to claim 1, wherein the first focus
position is associated with an object positioned far from the
objective lens assembly and the second focus position is associated
with the object positioned substantially closer to the objective
lens assembly.
3-7. (canceled)
8. A focusing device according to claim 1, wherein the LOS sensor
includes an accelerometer coupled to the night vision optical
device.
9-11. (canceled)
12. A night vision optical device comprising: an objective lens
assembly positioned at a first or second focus position from an
imaging device; and a binary focus controller, coupled to the
objective lens assembly including: a line of sight (LOS) sensor
coupled to the night vision optical device, configured to detect an
orientation of the night vision optical device relative to a
horizontal LOS, and a focus selector for selecting either the first
or second focus position in response to the detected orientation of
the night vision optical device, wherein the binary focus
controller is configured to translate the objective lens assembly
relative to the imaging device to either the first or second focus
position responsive to the focus selector, the LOS sensor includes
a pendulum mass coupled to the night vision optical device via a
pendulum arm, the pendulum arm rotating with the pendulum mass
responsive to the orientation of the night vision optical device,
and the LOS sensor includes a linkage coupled to the pendulum arm
and the focus selector includes: a first piston coupled to the
linkage and positioned in a first pneumatic system at a first or
second position based on a rotation of the pendulum mass, and the
first or second position of the first piston, respectively,
corresponds to the first or second focus position.
13. A night vision device according to claim 12, wherein the
imaging device includes an image intensifier or an imaging
array.
14. A night vision device according to claim 12, wherein the first
focus position is associated with an object positioned far from the
objective lens assembly and the second focus position is associated
with the object positioned substantially closer to the objective
lens assembly.
15. A night vision device according to claim 12, wherein the binary
focus controller includes a lens positioner coupled to the
objective lens assembly for translating the objective lens assembly
responsive to the selected focus position.
16. A night vision device according to claim 12, wherein the LOS
sensor includes an accelerometer.
17-18. (canceled)
19. A night vision device according to claim 12, further comprising
a lens positioner including: a second pneumatic system coupled to
the first pneumatic system, the second pneumatic system including a
second piston configured to be at a first or second further
position responsive to the corresponding first or second position
of the first piston; and a second linkage coupled to the objective
lens assembly and to the second piston, configured to translate the
objective lens assembly to either the first or second focus
position responsive to the first or second further position of the
second piston.
20. A method for controlling a focal position of an objective lens
assembly positioned from an imaging device in a night vision
optical device, the method comprising: detecting an orientation of
the night vision optical device relative to a horizontal line of
sight (LOS); selecting either a first or second focus position in
response to the detected orientation of the night vision optical
device; and translating the objective lens assembly relative to the
imaging device to the selected focus position; wherein selecting
the second focus position includes: determining a tilt angle of the
night vision optical device in response to the detected
orientation; selecting the first focus position when the tilt angle
is less than or equal to a first predetermined threshold; selecting
the second focus position when the tilt angle is greater than or
equal to a second predetermined threshold, the second predetermined
threshold larger than the first predetermined threshold; and
maintaining a previously selected focus position when the tilt
angle is greater than the first predetermined threshold and less
than the second predetermined threshold.
21-22. (canceled)
23. The method according to claim 20, wherein selecting the first
focus position corresponds to focusing the objective lens to an
object positioned far from the objective lens assembly, and
selecting the second focus position corresponds to focusing the
objective lens to the object positioned substantially closer to the
objective lens assembly.
Description
FIELD OF INVENTION
[0001] The present invention relates to a binary focus mechanism
for use with an optical device, particularly suited for night
vision goggle applications.
BACKGROUND OF THE INVENTION
[0002] Night vision systems are used in a wide variety of military,
industrial and residential applications to enable sight in a dark
environment. For example, night vision systems are utilized by
military aviators during nighttime flights or military soldiers
patrolling the ground. As another example, security cameras use
night vision systems to monitor dark areas.
[0003] Conventional image intensified night vision equipment
utilize an image intensifier (I.sup.2) to amplify a low light level
(LL) scene. The image intensifier collects tiny amounts of light in
a dark environment, including the lower portion of the infrared
light spectrum, that are present in the environment but may be
imperceptible to the human eye. The image intensifier amplifies the
light so that the human eye can perceive the image. The light
output from the image intensifier can either be supplied to a
camera or directly to the eyes of the viewer. Image intensifier
devices are commonly used in night vision goggles, i.e., a
monocular or binocular, that are worn on a user's head for
transmission of light output directly to the viewer.
[0004] Night vision systems typically do not include an autofocus
device. Conventional autofocus devices include an objective lens,
an electronic imaging device (such as a charge coupled device (CCD)
or complementary metal oxide semiconductor (CMOS) circuit), an
electro-mechanical driver for positioning the objective lens
relative to the imaging device and an electronic processor that
performs real-time image analysis. In operation, the electronic
processor determines a suitable focus adjustment based on the
real-time image analysis. The electronic processor sends focus
commands to the electro-mechanical driver to position the objective
lens for optimal focusing of the image.
[0005] Because the processor is continually analyzing the image,
and may adjust the objective lens over a wide range of focus
positions, continuous electrical power is generally used by the
autofocus components. In a conventional application, the power
provided to the autofocus components may represent a significant
percentage of the available power. For applications that are
carried by an individual and are battery operated, the total
operating time from a single battery charge may be strongly
influenced by the power consumption by the autofocus device. In
addition, the weight of existing autofocus devices, in particular,
the weight of the electro-mechanical driver and battery components,
tends to reduce the mobility of the observer.
SUMMARY OF THE INVENTION
[0006] The present invention relates to a focusing device for use
with a night vision optical device. The focusing device includes an
objective lens assembly positioned at a first or second focus
position from an imaging device and a binary focus controller,
coupled to the objective lens assembly, configured to translate the
objective lens assembly relative to the imaging device to either
the first or second focus position. The objective lens assembly is
translated to either the first or second focus position in response
to an orientation of the night vision optical device.
[0007] The present invention also relates to a night vision optical
device. The night vision optical device includes an objective lens
assembly positioned at a first or second focus position from an
imaging device and a binary focus controller, coupled to the
objective lens assembly. The binary focus controller includes a
line of sight (LOS) sensor coupled to the night vision optical
device, configured to detect an orientation of the night vision
optical device relative to a horizontal LOS and a focus selector
for selecting either the first or second focus position in response
to the detected orientation of the night vision optical device. The
binary focus controller is configured to translate the objective
lens assembly relative to the imaging device to either the first or
second focus position responsive to the focus selector.
[0008] The present invention also relates to a method for
controlling a focal position of an objective lens assembly
positioned from an imaging device in a night vision optical device.
The method includes detecting an orientation of the night vision
optical device relative to a horizontal line of sight (LOS),
selecting either a first or second focus position in response to
the detected orientation of the night vision optical device and
translating the objective lens assembly relative to the imaging
device to the selected focus position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention may be understood from the following detailed
description when read in connection with the accompanying drawing.
Included in the drawing are the following figures:
[0010] FIG. 1 is a block diagram illustrating a position of a focal
plane relative to an objective lens for objects at different
distances from the objective lens;
[0011] FIG. 2 is a cross-section diagram of a focusing device
according to an exemplary embodiment of the present invention;
[0012] FIGS. 3A and 3B are cross-section diagrams of the focusing
device shown in FIG. 2 as part of a night vision optical device,
illustrating binary positioning of the objective lens assembly for
distant and near objects, respectively, according to exemplary
embodiments of the present invention;
[0013] FIG. 4 is a block diagram of a binary focus controller
included in the focusing device shown in FIG. 2, according to an
exemplary embodiment of the present invention;
[0014] FIGS. 5A and 5B are flow charts illustrating exemplary
methods of binary positioning of an objective lens assembly,
according to embodiments of the present invention;
[0015] FIG. 6A is a block diagram of a night vision optical device,
according to an exemplary embodiment of the present invention;
[0016] FIG. 6B is a block diagram of a night vision optical device,
according to another exemplary embodiment of the present
invention;
[0017] FIG. 7A is a cross-section diagram of a line of sight (LOS)
sensor included in the binary focus controller shown in FIG. 4,
according to an exemplary embodiment of the present invention;
[0018] FIGS. 7B and 7C are side view diagrams of the LOS sensor
shown in FIG. 7A, illustrating examples of sensor orientation
relative to an orientation of a night vision optical device for far
and near focus positions, respectively, according to exemplary
embodiments of the present invention;
[0019] FIG. 8A is a circuit diagram of a tilt angle detector
included in the LOS sensor shown in FIG. 7A, according to an
exemplary embodiment of the present invention;
[0020] FIG. 8B is a perspective diagram of a tilt angle detector in
the LOS sensor shown in FIG. 7A, according to another exemplary
embodiment of the present invention;
[0021] FIG. 9A is a perspective diagram of a line of sight (LOS)
sensor included in the binary focus controller shown in FIG. 4,
according to another exemplary embodiment of the present
invention;
[0022] FIGS. 9B and 9C are side view diagrams of the LOS sensor
shown in FIG. 9A coupled to a night vision optical device,
illustrating examples of sensor orientation relative to an
orientation of a night vision optical device for far and near focus
positions, respectively, according to exemplary embodiments of the
present invention;
[0023] FIGS. 10A and 10B are circuit diagrams of a lens positioner
included in the binary focus controller shown in FIG. 4, according
to exemplary embodiments of the present invention; and
[0024] FIGS. 11A and 11B are cross-sectional diagrams of the binary
focus controller shown in FIG. 4, according to another exemplary
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The invention will next be illustrated with reference to the
figures. Such figures are intended to be illustrative rather than
limiting and are included herewith to facilitate explanation of the
present invention. The figures are not to scale, and are not
intended to serve as engineering drawings.
[0026] Referring to FIG. 1, a block diagram illustrating a position
of a focal plane (FP) FP.sub.1 (or FP.sub.2) relative to objective
lens 102 for object 104 (or object 104') at different distances
from the objective lens. Objective lens 102 represents a general
objective lens, and may include one or more optical lens elements.
In general, objective lens 102 passes light rays 106 (or light rays
108) from object 104 (or object 104') and produces light rays 106'
(or light rays 108') that converge onto FP.sub.1. (or FP.sub.2).
The focal plane represents the position of the focused image of an
object. Typically, the focal plane represents the position of an
imaging device (not shown), such as a CCD detector, a CMOS
detector, or an image intensifier.
[0027] In FIG. 1 two different conditions for focusing are
illustrated. A first condition corresponds to object 104 located
far from objective lens 102. Object 104 is illustrated as being
located far enough away from objective lens 102 to be considered to
be at optical infinity. Light rays 106 from object 104 are
generally parallel light rays as they reach objective lens 102.
Light rays 106 pass through objective lens 102 to form light rays
106' that converge at FP.sub.1. The FP.sub.1 is located at a back
focus distance (BFD) of BFD.sub.1.
[0028] A second condition corresponds to object 104' located near
objective lens 102. Object 104' is illustrated as being relatively
close to objective lens 102 (i.e., not at infinity) to produce
light rays 108 that diverge as they reach objective lens 102. Light
rays 108 pass through objective lens 102 to form light rays 108'
that converge at FP.sub.2. The FP.sub.2 is located at BFD.sub.2. It
may be appreciated that the first focal plane FP.sub.1 is closer to
objective lens 102 as compared with the second focal plane FP.sub.2
and that objects 104, 104' are brought to focus at different back
focus distances BFD.sub.1, BFD.sub.2 in the image space of
objective lens 102.
[0029] Referring next to FIG. 2, there is shown a focusing device
for providing binary focusing, generally designated as 200.
Focusing device 200 may be used in a night vision optical device,
such as night vision optical device 300 (shown in FIG. 3A).
Focusing device 200 includes objective lens assembly 202, imaging
device 204, and binary focus controller 206. Imaging device 204 is
coupled to housing 208. Objective lens assembly 202 is mounted to
lens translation mechanism 210 that is also coupled to the housing.
Thus, the objective lens assembly 202 translates along translation
direction T relative to imaging device 204 via lens translation
mechanism 210.
[0030] In operation, binary focus controller 206 determines an
orientation of a night vision optical device (such as night vision
optical device 300 (FIG. 3A)) and translates objective lens
assembly 202 relative to imaging device 204 to one of two discrete
focus positions.
[0031] In general, objective lens assembly 202 may include one or
several optical power elements, such as lens elements and/or
mirrors, that are at fixed positions relative to each other within
the overall objective lens assembly. Thus, lens translation
mechanism 210 is illustrated as translating the entire objective
lens assembly 202 relative to imaging device 204. According to
another exemplary embodiment, objective lens assembly 202 may
include one or more optical power elements that move relative to
other optical power elements, in order to adjust the back focal
distance to imaging device 204. In this embodiment, lens
translation mechanism 210 may translate one or several optical
power elements relative to other optical power elements within
objective lens assembly 202, in order to provide the binary
focusing described further below.
[0032] Imaging device 204 may include any suitable device for
obtaining an image of an object, such as a CCD detector, a CMOS
detector or an image intensifier. Lens translation mechanism 210
may be any suitable mechanism, such as a carriage to translate
objective lens assembly 202 relative to imaging device 204. Binary
focus controller 206 is described further below with respect to
FIG. 4.
[0033] Referring next to FIGS. 3A and 3B, cross-section diagrams of
focusing device 200 are shown as being a section A of night vision
optical device 300. In particular, FIG. 3A shows the positioning of
objective lens assembly 202 for distant object 302 (at back focal
distance D.sub.1); and FIG. 3B illustrates positioning of objective
lens assembly 202 for near object 304 (at back focal distance
D.sub.2).
[0034] In FIG. 3A, night vision optical device 306 is directed
toward distant object 302 with a line of sight (LOS) that is
substantially parallel to a horizontal direction 306 (i.e., night
vision optical device 300 has a horizontal LOS). In this case,
objective lens assembly 202 is positioned at distance D.sub.1
relative to imaging device 204. The distance D.sub.1 represents the
first focus position (i.e. a far focus position) for objective lens
assembly 202.
[0035] In FIG. 3B, night vision optical device 300 is oriented at
LOS 308' that is directed to near object 304. The LOS 308', thus,
orients night vision optical device 300 at a tilt angle .theta.
relative to horizontal plane 306. In this case, objective lens
assembly 202 is positioned at distance D.sub.2 relative to imaging
device 204. The distance D.sub.2 represents a second focus position
(i.e. a near focus position) of objective lens assembly 202. In
this case, it is assumed that the tilt angle .theta. is greater
than a threshold angle (described further below), such that
objective lens assembly is positioned at the near focus
position.
[0036] According to the present invention, the first and second
focus positions are automatically determined by binary focus
controller 206, based on the orientation of night vision optical
device 300. Accordingly, the first focus position may be selected
by binary focus controller 206 when the tilt angle .theta. is
detected to be less than or equal to the predetermined threshold.
The second focus position may be selected by binary focus
controller 206 when the tilt angle .theta. is greater than the
predetermined threshold. Thus, the present invention has a line of
sight sensor that automatically drives objective lens assembly 202
to a near focus position when the LOS is above a predetermined
threshold.
[0037] In a typical scenario, the user/viewer may want an infinity
focus when looking along a horizontal LOS at far objects. The
infinity focus position of conventional autofocus devices typically
allows for clear viewing of far targets and scenes and supports a
general mobility task. If the soldier needs to observe a near
obstacle, (such as a log or a ditch during movement), however, it
is not convenient or feasible to repeatedly manually adjust the
focus of the conventional focusing device between a near and far
position. In those cases, the soldier typically leaves the focus of
conventional focus devices in the far focus position and gets a
highly defocused image of the near obstacle when the night vision
optical device is momentarily aimed down at the area in front of
his feet. In general, a near focus of about five feet (about 1.524
m) (object distance) is typically used in order to support
maneuvering around and through obstacles.
[0038] The present invention provides two automatically determined,
pre-set objective lens focus positions for a soldier. The present
invention automatically selects the first or second focus position,
without requiring the soldier to remove his hands from a weapon to
adjust the focus. The binary focusing of the present invention may
be useful for a dismounted soldier for both viewing of far targets
and scenes and for maneuvering around near obstacles.
[0039] Referring to FIG. 4, an exemplary binary focus controller
206 is shown. Binary focus controller 206 includes LOS sensor 402,
focus selector 404 and lens positioner 406. In general LOS sensor
402 uses the Earth's gravity vector to determine the orientation of
night vision optical device 300 (FIG. 3A). Different example
embodiments of LOS sensor 402 are described further below with
respect to FIGS. 7-9. As described with respect to FIGS. 7-9, LOS
sensor 402 may include electrical and/or mechanical components.
[0040] Focus selector 404 receives tilt angle information from LOS
sensor 402, determines the tilt angle .theta. from the tilt angle
information. Focus selector 404 selects either the first or second
focus positions based on the instantaneous tilt angle .theta.. It
is understood that focus selector 404 may include an electronic
processor and/or mechanical components. An example focus selector
404 that includes pneumatic components is described further below
with respect to FIGS. 11A and 11B. Focus selector 404 provides the
selected focus position setting to lens positioner 406 (for
example, as a focus command).
[0041] Lens positioner 406 receives the focus position setting (for
example, a focus command) from focus selector 404 and provides a
force to control translation of objective lens, via lens
translation mechanism 210 (FIG. 2). An example of lens positioner
406 is described further below with respect to FIGS. 10A and 10B.
Another exemplary embodiment of binary focus controller 206 is
described further below with respect to FIGS. 11A and 11B. It is
understood that lens positioner 406 may include electrical and/or
mechanical components to translate objective lens assembly 202
(FIG. 2).
[0042] Referring next to FIGS. 5A and 5B, exemplary methods for
translating the objective lens assembly 202 (FIG. 2) relative to
imaging device 204 to discrete binary focus positions are shown. In
particular, FIG. 5A represents an exemplary embodiment for
selecting a focus position based on a single threshold; and FIG. 5B
represents another exemplary embodiment for selecting a focus
position based on two thresholds (threshold.sub.A,
threshold.sub.B), thus implementing a hysteresis function.
[0043] Referring to FIG. 5A, at Step 500, a tilt angle .theta. is
determined, for example, by focus selector 404 (FIG. 4) based on
tilt angle information received from LOS sensor 402. At Step 502,
it is determined whether the tilt angle .theta. is less than or
equal to a threshold. Although in an exemplary embodiment, the
threshold is 40.degree. below horizontal plane 306 (FIG. 3B), it is
understood that the threshold may be any suitable threshold for
separating near and far focusing conditions for the user.
[0044] If the tilt angle .theta. is less than or equal to the
threshold, Step 502 proceeds to Step 504. At Step 504, the focus is
set to the first focus position (i.e., the far position shown in
FIG. 3A), for example by focus selector 404 (FIG. 4). For example,
a focus command may be generated by focus selector 404 (FIG. 4)
indicating the first focus position. At Step 506, objective lens
assembly 202 (FIG. 3A) is translated to the first focus position
(at distance D.sub.1), for example, responsive to the focus
command, by lens positioner 406 in conjunction with lens
translation mechanism 210 (FIG. 2). Step 506 proceeds to Step
500.
[0045] If the tilt angle .theta. is greater than the threshold,
Step 502 proceeds to Step 508. At Step 508, the focus is set to the
second focus position (i.e., the near focus position shown in FIG.
3B), for example, by focus selector 404 (FIG. 4). For example, a
focus command may be generated by focus selector 404 (FIG. 4)
indicating the second focus position. At Step 510, objective lens
assembly 202 is translated to the second focus position (at
distance D.sub.2 shown in FIG. 3B), for example, responsive to the
focus command, by lens positioner 406 (FIG. 4) in conjunction with
lens translation mechanism 210 (FIG. 2). Step 510 proceeds to Step
500. The process of Steps 500-510 may be continued for updated tilt
angle information.
[0046] Referring to FIG. 5B, at Step 512, the tilt angle .theta. is
determined, for example, by focus selector 404 (FIG. 4) using the
tilt angle information received from LOS sensor 402. At Step 514,
it is determined whether the tilt angle .theta. is less than or
equal to a first threshold threshold.sub.A. Although in an
exemplary embodiment, the threshold.sub.A is 40.degree. below
horizontal plane 306 (FIG. 3B), it is understood that the first
threshold may be any suitable threshold for separating near and far
focusing conditions for the user.
[0047] If it is determined that the tilt angle .theta. is less or
equal to threshold.sub.A, Step 514 proceeds to Step 516. At Step
516, the focus is set to the first focus position (i.e., the far
position shown in FIG. 3A), for example, by focus selector 404
(FIG. 4). At Step 518, objective lens assembly 202 (FIG. 3A) is
translated to the first focus position (at distance D.sub.1), for
example by lens positioner 406 (FIG. 4) in conjunction with lens
translation mechanism 210 (FIG. 2). Step 518 proceeds to Step
512.
[0048] If it is determined that the tilt angle .theta. is greater
than threshold.sub.a, Step 514 proceeds to Step 520. At Step 520,
it is determined whether the tilt angle .theta. is greater than or
equal to a second threshold, threshold.sub.B. An exemplary
embodiment, threshold.sub.b represents 45.degree. below horizontal
plane 306 (FIG. 3B). Although in an exemplary embodiment, the
threshold.sub.B is 45.degree. below horizontal plane 306 (FIG. 3B),
it is understood that the second threshold may be any suitable
threshold for providing a borderline region separating near and far
focusing conditions for the user.
[0049] If the tilt angle .theta. is greater than or equal to
threshold.sub.B, Step 520 proceeds to Step 526. At Step 526, the
focus is set to the second focus position (i.e., the near position
shown in FIG. 3B), for example, by focus selector 404 (FIG. 4). At
Step 528, objective lens assembly 202 (FIG. 3B) is translated to
second focus position (at distance D.sub.2), for example, by lens
positioner 406 (FIG. 4) in conjunction with lens translation
mechanism 210 (FIG. 2). Step 528 proceeds to Step 512.
[0050] If it is determined, at Step 514, that the tilt angle
.theta. is less than threshold.sub.B (and greater than
threshold.sub.A, Step 514) Step 520 proceeds to Step 522. At Step
522, the focus setting is maintained at its current focus position,
for example, by focus selector 404 (FIG. 4). At Step 524, the
objective lens assembly 202 is maintained at its current position
(either at the first focus position or the second focus position).
Step 524 proceeds to Step 512.
[0051] Steps 520-524 represents a hysteresis function that uses the
previously determined focus position for conditions where the tilt
angle .theta. is between threshold.sub.A and threshold.sub.B. In
this embodiment, the use of two thresholds, threshold.sub.A,
threshold.sub.B may prevent repeated switching between the near and
far lens positions when the LOS 308' (FIG. 3B) is in a borderline
orientation between threshold.sub.A and threshold.sub.B.
[0052] Steps 512-528 may be repeated for each detected tilt angle,
for example, indefinitely.
[0053] Referring next to FIG. 6A, a block diagram of an exemplary
night vision optical device 300 is shown. Night vision optical
device 300 includes objective lens assembly 202, binary focus
controller 206, image intensifier 602 and eyepiece lens 604. Night
vision optical device 300 may include other components, such as a
high voltage power supply (HVPS).
[0054] Objective lens assembly 202 is positioned by binary focus
controller 206 to receives light rays 608 from object 606 for a
first or second focus position. Objective lens assembly 202
provides a focused image of a low light level scene to image
intensifier 602, which may be powered by a HVPS. Image intensifier
602 amplifies the faint image at its input and reproduces a
brighter version of this image on its output surface. This image is
coherently transmitted to eyepiece lens 604 for display of the
produced image. In FIG. 6A, imaging device 204 is represented by
image intensifier 602.
[0055] Referring next to FIG. 6B, a block diagram of another
exemplary night vision optical device 300' is shown. Night vision
optical device 300' includes objective lens assembly 202, binary
focus controller 206, imaging array 610, video electronics module
612 and video display 614. Night vision optical device 300' is
similar to or functionally equivalent to night vision optical
device 300, except that device 300' includes imaging array 610 for
generating an image of object 606. In addition, device 300'
includes video electronics module 612 and video display 614 for
producing a real time video image of object 606.
[0056] Objective lens assembly 202 is positioned by binary focus
controller 206 to receives light rays 608 from object 606 for a
first or second focus position. Objective lens assembly 202
provides a focused image of a low light level scene to imaging
array 610 for video applications. In FIG. 6B, imaging device 204 is
represented by imaging array 610. Imaging array 610, which may be,
for example, of a CMOS or CCD type, senses the focused image and
creates real time video data that contains a rendition of the
image. The video data is provided to video electronics module 612
for converting the video data from imaging array 610 into digital
video data. Video display 614 receives that digital video data and
displays the real time digital video image.
[0057] Referring next to FIGS. 7A-7C, an exemplary LOS sensor 402
is shown. In particular, FIG. 7A is a cross-section diagram of LOS
sensor 402 coupled to a body 702 of night vision optical device 300
(FIG. 3A); FIG. 7B is a side view diagram of LOS sensor 402 for a
far focus condition; and FIG. 7C is a side view diagram of LOS
sensor 402 for a near focus condition.
[0058] In FIGS. 7A-7C, LOS sensor 402 includes a pendulum mass 704
rigidly coupled to pendulum arm 706. Pendulum arm 706 is also
coupled to tilt angle detector 708. In addition, tilt angle
detector 708 is coupled to body 702 of night vision optical device
300 (FIG. 3A). Pendulum mass 704 is coupled to body 702 such that
pendulum mass 704 is maintained in a position corresponding to the
gravity vector g.
[0059] As can be seen in FIGS. 7B and 7C, during movement of body
702 relative to the horizontal plane (i.e. the plane of X and Y),
the position of pendulum mass 704 is maintained in a direction of
gravity vector g. At the same time, the movement of body 702 causes
rotation of pendulum arm 706 in rotation direction R relative to
the Y axis. Tilt angle detector 708 detects the rotation of
pendulum arm 706 and provides tilt angle information. The tilt
angle information may be provided to focus selector 404 (FIG. 4).
Thus, the pendulum arm 706 rotation provides the tilt angle
information.
[0060] Referring next to FIGS. 8A and 8B, exemplary tilt angle
detectors 708, 708' for use with LOS sensor 402 (FIG. 7A) are
shown. In particular, FIG. 8A is a circuit diagram of a tilt angle
detector 708; and FIG. 8B is a perspective diagram of another tilt
angle detector 708'.
[0061] In FIG. 8A, tilt angle detector 708 includes a potentiometer
804, voltage supply 802 and output terminal 808 coupled to
potentiometer 804. Pendulum arm 706 is coupled to a wiper 806 of
potentiometer 804. Thus, rotation of pendulum arm 706 varies the
wiper position and the resulting voltage produced at output
terminal 808. The voltage signal at output terminal 808 may be
provided to focus selector 404 (FIG. 4). Focus selector 404 may
convert the voltage signal to a tilt angle, for example, by a
digital look-up table. It is understood that focus selector 404 may
be implemented using any suitable digital and/or analog
electronics.
[0062] Referring to FIG. 8B, tilt angle detector 708' may include a
magnetic rotational sensor including magnet 810 and magnetic rotary
position encoding circuit 812. Pendulum arm 706 may be coupled to
magnet 810. Rotation R of pendulum arm 706 may produce a pendulum
position signal via encoding circuit 812. The pendulum position
signal may be provided to focus selector 404, which may convert the
position signal to a tilt angle, for example via a look-up table.
Potentiometers and encoding circuits are known in the art and may
be understood by the skilled person. It is understood that tilt
angle detectors 708, 708' represent two exemplary embodiments for
detecting an orientation of night vision optical device 300 (FIG.
6) relative to the horizontal plane 306 (FIG. 3A) and that other
suitable tilt angle detectors may be used.
[0063] Referring now to FIGS. 9A-9C, another exemplary LOS sensor
402' is shown. In particular, FIG. 9A is a perspective diagram of a
three-axis accelerometer 900 that is used as LOS sensor 402'. FIGS.
9B and 9C are examples illustrating the orientation of
accelerometer 900 with respect to gravity vector g at far and near
focus conditions, respectively.
[0064] Accelerometer 900 may be any suitable
Micro-Electro-Mechanical system (MEMS) that may collect data along
three axes X', Y' and Z' to detect gravity vector g. As shown in
FIGS. 9B and 9C, accelerometer 900 is coupled to body 702 of night
vision optical system 300 (FIG. 3A). Although not shown,
accelerometer 900 may include other components, such as a
preamplifier and/or filters having suitable filter coefficients to
detect the gravity vector g. Accelerometer 900 provides a position
signal (including X', Y' and Z' axis data) to focus selector 404
(FIG. 4), which represents the tilt angle information.
[0065] For example, as shown in FIG. 9B, body 702 is oriented to
the far focus position (i.e., having a horizontal LOS). When body
702 is moved to the far focus position, only the Z' axis data may
contribute to the position signal. Accordingly, accelerometer 900
may produce: X' axis data of 0 m/s.sup.2, Y' axis data of 0
m/s.sup.2 and a Z' axis data of 9.8 m/s.sup.2.
[0066] Referring to FIG. 9C, when body 702 is moved from the far
focus condition (FIG. 9B) to the near focus condition, acceleration
data from the Z' axis, as well the acceleration data from the X'
axis and/or Y' axis may contribute to the position signal. For
example, accelerometer 900 may produce: X' axis data of 6.93
m/s.sup.2, Z' axis data of 6.93 m/s.sup.2and Y' axis of 0
m/s.sup.2. The acceleration data produced by the X', Y' and Z' axes
may be used to determine the tilt angle.
[0067] Referring next to FIGS. 10A and 10B, circuit diagrams of
exemplary lens positioner 406 for translating objective lens
assembly 202 (FIG. 2) based on electrostatic charge is shown. In
particular, FIG. 10A illustrates the circuit diagram to produce the
far focus position translation; and FIG. 10B illustrates the
circuit diagram to produce near focus position translation.
[0068] Lens positioner 406 includes electrically charged plates
1002-1 and 1002-2 that are respectively coupled to lens translation
mechanism 210 (FIG. 2) and housing 208. Plates 1002 are provided
with the same or opposite charges in order to produce a force
F.sub.1 or F.sub.2 to translate objective lens assembly 202 (FIGS.
3A, 3B) to respective back focus distances D.sub.1, D.sub.2. In
order to apply the appropriate charge to plates 1002, lens
positioner 406 includes HVPS 1006 and switch 1004. The position of
switch 1004 may be set based on focus selector 404 (FIG. 4). It is
understood that an appropriate force F.sub.1, F.sub.2 may be
determined to translate objective lens assembly 202 (FIGS. 3A, 3B)
based on the desired back focal distances D.sub.1, D.sub.2.
[0069] As shown in FIG. 10A, switch 1004 is set to a first
position, causing plates 1002-1 and 1002-2 to be oppositely
charged. Because plates 1002 are oppositely charged, they are
attracted to each other, causing an attraction force F.sub.1. The
attraction force F.sub.1 causes objective lens assembly 202 (FIG.
3A) to move to distance D.sub.1.
[0070] As shown in FIG. 10B, switch 1004 is set to a second
position, causing plates 1002-1 and 1002-2 to have a same charge
(e.g., a negative charge). Because plates 1002 have a same charge,
they are repelled from each other, causing an repelling force
F.sub.2. The repelling force F.sub.2 causes objective lens assembly
202 (FIG. 3B) to move to distance D.sub.2.
[0071] In an exemplary embodiment, HVPS 1006 may receive an input
voltage of 3 V DC (with 10-15 mA) and produce an output voltage of
4-5 kV (with 10-15 nA). It is understood that any suitable power
supply may be used to generate the appropriate force F to translate
objective lens assembly 202 (FIGS. 3A, 3B) to the appropriate first
and second focus positions (i.e., to back focal distances D.sub.1,
D.sub.2).
[0072] Referring next to FIGS. 11A and 11B, a pneumatically based
binary focus controller 206' is shown. In particular, FIG. 11A is a
cross-section diagram of binary focus controller 206' for providing
the near focus position (i.e., back focus distance D.sub.2 shown in
FIG. 3B); and FIG. 11B is a cross-section diagram of binary focus
controller 206' for providing the far focus position (i.e., back
focus distance D.sub.1 shown in FIG. 3A).
[0073] Binary focus controller 206' includes pendulum mass 704 that
is coupled to a pendulum arm at pivot point 1102. Because pendulum
mass 704 is also coupled to linkage 1106 at pivot point 1104,
pendulum mass 704 provides translation of linkage 1106 in the
T.sub.1 direction in response to movement of a night vision optical
device 300 (FIG. 3A). Linkage 1106 is coupled to first piston 1108
positioned in first cylinder 1110 (i.e. a first pneumatic system).
A second linkage 1118 is coupled to second piston 1116 that is
positioned in a second cylinder 1112 (i.e. a second pneumatic
system). First cylinder 1110 and second cylinder 1112 are
pneumatically coupled to each other (i.e., second cylinder 1112 is
slave to first cylinder 1110). Linkage 1118 is also coupled to lens
translation mechanism 210.
[0074] Binary focus controller 206' also includes plenum chamber
1114 which receives and stores lightly pressurized air, for
example, from a wearable pump (not shown) and which is coupled to
first air cylinder 1110. Air cylinder 1110 includes ports open to
ambient pressure (P).
[0075] Linkage 1106 represents a tilt angle detector (such as tilt
angle detector 708 (FIG. 7A)). Linkage 1118, piston 1116 and second
air cylinder 1112 represents a lens positioner (such as lens
positioner 406 (FIG. 6)). First piston 1108 and first air cylinder
1110 represent a focus selector (such as focus selector 404 (FIG.
4)).
[0076] In operation, the rotation of pendulum mass 704 drives first
piston 1108 to one of two positions in response to the tilt angle
.theta.. When first piston 1108 changes position, pressurized air
from plenum chamber 1114 flows to one side of second piston 1116,
thus driving second piston 1116 to an opposite end of second
cylinder 1112. First piston 1108 allows air from a decreasing
volume side of second cylinder 1112 to reach equilibrium with the
local ambient pressure, which provides a pressure differential to
move second piston 1116. Thus, movement of pendulum mass 704 causes
linear translation T.sub.1 of linkage 1106 and also causes
translation T.sub.2 of linkage 1118. The translation T.sub.2 of
linkage 1118, in turn, translates objective lens assembly 202 to
the near focus position (FIG. 11A) or to the far focus position
(FIG. 11B).
[0077] Although the invention is illustrated and described herein
with reference to specific embodiments, the invention is not
intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope and range
of equivalents of the claims and without departing from the
invention.
* * * * *