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Digital Camera Patent Abstract
A test apparatus and method for testing the zoom of a miniature
digital camera module is presented. A combination of focus targets
are illuminated by different colors of light and simultaneously
viewed by the digital camera module. The focus targets range from
a far target to a close target and are positioned in the apparatus
accordingly. The zoom capability of the camera can be either electrical
or manual, and the test apparatus can be adapted to either zoom
configurations allowing the zoom of the camera lens to be controlled
by a tester. The brightness of the image of the focus targets captured
by the digital camera is monitored to determine whether the focus
of the camera is maintained over the range of zoom.
Digital Camera Patent Claims
1. An optics system for testing a zoom capability of a miniature
digital camera module, comprising: a) a light source, b) a plurality
of focus targets, c) a field lens d) a magnifier lens, e) a digital
camera module (MUT) containing a zoom lens, f) said light source
illuminates said focus targets producing a target image focused
onto said MUT by said field lens and said magnifier lens.
2. The optics system of claim 1, wherein said light source produces
a red light.
3. The optics system of claim 1, wherein said light source produces
a blue light.
4. The optics system of claim 1, wherein said light source produces
a green light.
5. The optics system of claim 1, wherein the light source produces
an infrared light.
6. The optics system of claim 1, wherein said plurality of focus
targets further comprise: a) a far focus target located in a target
holder furthest from said MUT, b) a first intermediate focus target
located in said target holder closer to said MUT than said far focus
target, c) a second intermediate focus target located in said target
holder closer to said MUT than said first intermediate focus target,
d) a close focus target located in said target holder closer to
said MUT than said second intermediate focus target.
7. The optics system of claim 6, wherein said far focus target,
said first intermediate focus target, said second intermediate focus
target and said close focus target are simultaneously positioned
between the light source and the MUT to produce a composite image
that is focused onto said zoom lens.
8. The optics system of claim 6, wherein said far focus target,
said first intermediate focus target, said second intermediate focus
target and said close focus target are combined into a single composite
focus target, which is positioned between said light source and
said MUT to provide a composite image that is focuses onto said
zoom lens.
9. The optics system of claim 8, wherein said composite focus target
is positioned in said target holder at an angle to an optical centerline
between said light source and said MUT.
10. The optics system of claim 9, wherein said far focus target
portion of said composite target is positioned furthest from said
MUT and said close focus target portion of said composite target
is positioned closest to said MUT.
11. The optics system of claim 1, wherein said magnifier lens is
moved along an optical centerline between said MUT and said filed
lens to change a magnification of said target image as viewed by
said MUT.
12. The optics system of claim 1, wherein said zoom lens is electrically
adjustable.
13. The optics system of claim 12, wherein said zoom lens expands
or contracts said target image onto a light sensitive device within
said MUT in response to electrical signals applied to said MUT.
14. The optics system of claim 1, wherein said zoom lens is mechanically
adjustable.
15. The optics system of claim 14, wherein said zoom lens expands
or contracts said target image onto a light sensitive device within
said MUT in response to a stepper motor driven mechanical device
in contact with a lens cap of said MUT.
16. A method of testing a zoom lens of a miniature digital camera
module, comprising: a) positioning a focus target in a target wheel
over an optical centerline of an optics system for testing a digital
camera module (MUT) containing a zoom lens, b) setting a distance
of said target wheel from said MUT, c) setting said distance of
a field lens that focuses an image of said focus target onto said
zoom lens of said MUT, d) selecting a color of light to illuminate
said focus target, e) varying a setting of said zoom lens and checking
a focus of said image captured by a light sensitive device within
said MUT, f) positioning a magnifier lens over said optical center
line at a distance from said MUT, g) varying said setting of said
zoom lens and checking a focus of said image captured by a light
sensitive device within said MUT, h) reposition said magnifier lens
and varying said setting of said zoom lens and checking a focus
of said image captured by a light sensitive device within said MUT
until all magnifier lens positions have been used, i) selecting
a next color of light and repeating steps e) through h), k) ending
when zoom testing with all colors of light has been completed.
17. The method of claim 16, wherein said focus target is a plurality
of targets oriented simultaneously in a plurality of target wheels
and creating a composite image as viewed by said MUT of said plurality
of targets.
18. The method of claim 17, wherein said plurality of focus targets
further comprise: a) a far target containing large holes to allow
said light illuminating the far target to pass through to the MUT,
b) a first intermediate target containing holes smaller than said
far target to allow said light illuminating the first intermediate
target to pass through to the MUT, c) a second intermediate target
containing holes smaller than said first intermediate target to
allow said light illuminating the second intermediate target to
pass through to the MUT, d) a close target containing holes smaller
than said second intermediate target to allow said light illuminating
the close target to pass through to the MUT.
19. The method of claim 18, wherein said far target is located
in said target wheel furthest from the MUT, the first intermediate
target is located in said target wheel closer to said MUT than the
far target, the second intermediate target is located in said target
wheel closer to said MUT than the first intermediate target, and
the close target is located in said target wheel closest to said
MUT.
20. The method of claim 18, wherein said plurality of focus targets
are combined into a single composite target containing a first pattern
of said holes representing said far target, a second pattern of
holes representing said first intermediate target, a third pattern
of holes representing said second intermediate target and a fourth
pattern of holes representing said close target.
21. The method of claim 20, wherein said single composite target
is mounted in the target wheel orthogonal to the optical centerline.
22. The method of claim 20, wherein said single composite target
is mounted in said target wheel at a angle less than ninety degrees
to the optical centerline.
23. The method of claim 22, wherein said single composite target
is mounted in said target wheel to position said first pattern of
holes furthest from said MUT and said fourth pattern of holes closest
to said MUT.
24. The method of claim 16, wherein varying said setting of the
zoom lens is by an electrical signal from a tester.
25. The method of claim 16, wherein varying said setting of the
zoom lens is by a zoom stepper mechanism that physically contacts
a lens cap of said MUT to adjust the setting of the zoom.
26. The method of claim 16, wherein checking said focus of the
image captured by said light sensitive device is by monitoring a
brightness of said image as the zoom is varied.
27. The method of claim 16, wherein positioning said magnifier
lens changes the magnification of the image captured by said light
sensitive device.
28. The method of claim 16, wherein said zoom lens further comprises
multiple elements.
29. The Method of claim 28, wherein selecting said color of light
comprises a light of a blue color to check said focus of the zoom
lens containing said multiple elements.
30. The Method of claim 16, wherein selecting said color of light
comprises a light of a red color to check said focus of the zoom
lens containing said multiple elements.
Digital Camera Patent Description
RELATED PATENT APPLICATION
[0001] This application is related to US patent application docket
number DS 04-022, Ser. No. ______, filed on ______, and assigned
to the same assignee as the present invention.
[0002] This application is related to US patent application docket
number DS 04-023, Ser. No. ______, filed on ______, and assigned
to the same assignee as the present invention.
[0003] This application is related to US patent application docket
number DS 04-024, Ser. No. ______, filed on ______, and assigned
to the same assignee as the present invention.
[0004] This application is related to US patent application docket
number DS 04-025, Ser. No. ______, filed on ______, and assigned
to the same assignee as the present invention.
[0005] This application is related to US patent application docket
number DS 04-026, Ser. No. ______, filed on ______, and assigned
to the same assignee as the present invention.
BACKGROUND OF THE INVENTION
[0006] 1. Field of Invention
[0007] The present invention relates to the testing of miniature
digital camera modules and in particular to digital camera modules
with electrical and/or optical zoom capability.
[0008] 2. Description of Related Art
[0009] The digital camera is becoming a ubiquitous device. Not
only are digital cameras replacing the traditional film camera,
digital camera devices are being used in many other applications,
such as small electronic devices, such as PDA (personal data assistant)
and cellular phones. With the explosion of cellular phones, the
ability to take a picture and then send that picture to another
individual using a second cellular phone comes the need to produce
inexpensive digital camera modules and efficiently test these modules
in large quantities. This is further complicated by the many different
module configurations that are emerging as a result of the many
different application requirements, including fixed focus, manual
focus and automatic focus as well as physical size. Some of these
modules are very small and others have signal leads in the form
of a flex filmstrip. The testing time for digital camera module,
which can have mega-pixel capability, has traditionally been a relatively
long process (approximately sixty seconds for a module with 0.3
mega pixels) to insure the integrity and picture quality of the
camera. Quality testing at a low cost has become the utmost of importance.
This necessitates a testing capability that is fast and insures
the integrity and specification of the digital camera module while
testing a large quantity of modules.
[0010] A patent application, Ser. No. 10/417,316 dated Apr. 16,
2003, is related to miniature cameras and their manufacturing methods
that are used as built-in modules in hand held consumer electronics
devices such as mobile phones and PDA's. In a second patent application,
Ser. No. 10/434,743 dated May 18, 2003, a test system is described
for digital camera modules used as built-in modules for consumer
electronics, which performs electrical tests, adjustment of focus
and sealing of the lens barrel with glue.
[0011] In addition there are a number of other prior art patents
that are directed to testing of digital cameras: US 20040032496A1
(Eberstein et al.) is directed to a method of camera calibration
and quality testing; EP 1389878A1 (Bednarz et al.) is directed to
a method of camera calibration and testing camera quality; US 20040027456A1
(pierce) directed to the use of calibration targets; EP 1382194A1
(Baer) is directed to dark current subtraction; JP 2003259126 (Keisuke)
is directed to removing noise of an image; US 20030146976A1 (Liu)
is directed to a digital camera system enabling remote monitoring;
JP 2003219436 (Fuminori) is directed to adjustment of a pixel shift
camera; US 2003142374 (Silverstein) is directed to calibrating output
of an image output device; JP 2003179949 (Hidetoshi) is directed
to a luminance level inspection apparatus; JP 2003157425 (Vehvilainen)
is directed to improving image quality produced in a mobile imaging
phone; JP 2003101823 (Kenichi) is directed to specifying a picture
data area; EP 1286553 A2 (Baer) is directed to a method and apparatus
for improving image quality; US 20030030648 (Baer) is directed to
a method and apparatus for improving image quality in digital cameras;
U.S. Pat. No. 6,512,587 (Dilella et al.) is directed to measurement
method and apparatus of an imager assembly; US 20030002749 (Vehvilainen)
is directed to a method and apparatus for improving image quality;
US 20020191973 A1 (Hofer et al.) is directed to a method and apparatus
for focus error reduction; WO 2002102060 A1 (Baer) is directed to
a method and apparatus for smear in digital images using a frame
transfer sensor; JP 2002290994 (Hidetoshi) is directed to a method
and apparatus to detect foreign matter on the surface of a lens;
JP 200223918 (Yanshinao) is directed to an image inspection device
and method for a camera module; JP 2002077955 (Keisuke) is directed
to a method and apparatus for evaluating camera characteristics;
JP 2001292461 (Keisuke) is directed to a system and method for evaluating
a camera; U.S. Pat. No. 6,219,443 B1 (Lawrence) is directed to a
method and apparatus for inspecting a display using a low resolution
camera; U.S. Pat. No. 6,201,600B1 (Sites et al.) is directed to
a method and apparatus for inspection of optically transmissive
objects having a lens; U.S. Pat. No. 5,649,258 (Bergstresser et
al.) is directed to an apparatus and testing of a camera; EP 0679932
B1 (Kobayashi et al.) is directed to testing an electronically controlled
camera; U.S. Pat. No. 5,179,437 (Katsumi et al.) is directed to
an apparatus for color correction of image signals of a color television
camera; JP 03099376 (Hiroshi) is directed to the quality of a display
screen; U.S. Pat. No. 4,612,666 (King) is directed to a pattern
recognition apparatus; and U.S. Pat. No. 4,298,944 Stoub et al.)
is directed to a method and apparatus for distortion correction
for scintillation cameras
SUMMARY OF THE INVENTION
[0012] It is an objective of the present invention to test a zoom
capability for a miniature digital camera module that has an electrical
zoom capability.
[0013] It is also an objective of the present invention to test
a zoom capability for a miniature digital camera module that has
a mechanical zoom capability.
[0014] It is further an objective of the present invention to position
a plurality of focus targets simultaneously at varying distances
from a digital camera module to permit a zoom test to evaluate a
full range of focus during the zoom test.
[0015] It is further another objective of the present invention
to combine the plurality of focus targets into a single composite
target.
[0016] It is still further an objective of the present invention
to position the single composite target to provide optical depth
for the zoom test.
[0017] In the present invention a miniature digital camera module
with a zoom capability is tested for the ability of the zoom to
maintain far and near focus over the range of the zoom. An optical
system, comprising a light source, focus targets, a field lens,
and an image magnifier is used to provide an image to a digital
camera module under test (MUT) that can be changed to provide a
view to the MUT that is optically closer or farther away from the
lens of the MUT. The MUT has either an electrical controlled zoom
or a mechanical zoom, the adjustment of which is controlled by a
tester.
[0018] The tester controls the optical system contained within
a test station to vary the image viewed by the MUT. A test fixture
within the test station positions the MUT under the optics centerline
and provides electrical contact between the MUT and the tester.
The zoom adjustment of the MUT is varied over a complete zoom range
and the image of the focus targets is measured for maintaining focus
as the zoom is changed. When a MUT has an electrically controlled
zoom, the tester controls the zoom through electrical signals to
the MUT. When the MUT has a mechanically adjustable zoom, a zoom
stepper mechanism physically contacts the zoom adjustment of the
lens of the MUT, and the tester controls a stepper motor to vary
the zoom of the MUT.
[0019] The focus targets used to test the zoom capability of the
MUT form a composite image that is focused onto the lens of the
MUT by the field lens. The composite image comprises a far, an intermediate
and a close target that have been positioned simultaneously within
the optical view of the MUT. The composite image allows the focus
test of the zoom using one setup of the optics system and one set
of test images captured by the MUT, which reduces the test time
that would have been required for individual targets resulting in
multiple setup and test.
[0020] A single composite target can also be used to provide the
composite image to the MUT for testing the zoom capability. The
composite target comprises a far, intermediate and close targets
constructed within a single focus target. The composite target is
held by a target holder within the view of the MUT and is either
orthogonal to the axis of the optical system or at an angle less
than ninety degrees with respect to the axis to provide a depth
of field.
[0021] The focus targets comprise light and dark area, where the
light areas are holes in the targets that permit light through.
The preferred shape of the holes is round; however, other shapes,
i.e. oval, rectangular, hexagonal, and octagonal, can be used. A
far target uses large holes and a close target uses small holes
with the intermediate targets having a hole size that is in between.
Monitoring the brightness of the image viewed by the MUT provides
the test of the focus of the targets over the zoom range. If the
brightness remains within an acceptable predetermined range, the
zoom capability of the MUT is tested as good.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] This invention will be described with reference to the accompanying
drawings, wherein:
[0023] FIG. 1 is a diagram of the optical system of the present
invention,
[0024] FIG. 2A is a diagram showing a plurality of focus targets
mounted in the optical system of the present invention,
[0025] FIG. 2B is a diagram of the image of the plurality of focus
targets seen by the MUT,
[0026] FIG. 3A is a diagram showing a composite focus target mounted
in the optical system orthogonal to an optical centerline of the
present invention,
[0027] FIG. 3B is a diagram of the image of the orthogonal mounted
composite of focus target seen by the MUT,
[0028] FIG. 4A is a diagram showing the composite focus target
mounted at a non-orthogonal angle to the optical centerline of the
present invention,
[0029] FIG. 4B is a diagram of the image of the non-orthogonal
mounted composite of focus target seen by the MUT, and
[0030] FIG. 5 is a method of testing the zoom capability of a MUT.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] In FIG. 1 a miniature digital camera module under test (MUT)
30 with a lens cap 31, which has an adjustable zoom, is mounted
on a test fixture 32 containing positioning clamps 33. When the
MUT 30 is place onto the test fixture 32, the MUT is clamped into
place by the positioning clamps 33 and contact is made to the electrical
I/O of the MUT (not shown). The test fixture 32 positions the MUT
30 under an optical centerline 46 of an optical system 20. A tester
22 provides control data 23 to the optical system 20 and the MUT
30, and receives test data 23 back from the MUT 30.
[0032] The optical system contains a light source 45 and a light
diffuser 69 to provide illumination 70 to the optical system 39.
The light source 45 comprises a plurality of serially connected
strings of light emitting diode devices (LED). Each string of LED
devices contains LED devices of a same color. There are strings
of LED devices that produce colors comprising red, green, blue and
infrared. Additional colors are also possible depending upon the
test requirements. The tester 22 connected to the optical system
controls the selection of a color of light and the intensity of
the light. Any source of light that produces the colors required
and can be switched on and off rapidly can be used. The LED devices,
for example, produce a stable light that has a very fast on and
off switching time and provides the colors that are required.
[0033] The optical system 20 contains two target wheels 40 and
41. Within each target wheel are target holders 42 that can contain
focus targets in a position 72 more distant from the MUT 30 and
in a position 73 that is closer to the MUT. Each target wheel 40
and 41 contains six target holders 42. The target holders 42 within
a target wheel 40 and 41 are rotated into position over the optical
axis 46 by stepper motors 75 and 76 controlled by the tester 22.
Since there are six target holders in each target wheel, the stepper
motors 75 and 76 rotate the target wheels in sixty-degree increments.
Target wheels with a fewer or a greater number of target holders
than six and a corresponding stepper increment are within the scope
of the present invention Continuing to refer to FIG. 1, the positioning
the target wheels 40 and 41 with respect to each other and the MUT
30 are critical in providing a focus image to the MUT. The positioning
of the target wheels 40 and 41 along the optical axis 46 is done
with stepper motors 77 and 78 under the control of the tester 22.
A field lens 43 is used to focus the image of targets contained
within the target holders 42 onto the lens of the MUT 30, and tester
22 controls a stepper motor 79 to position of the field lens 43
along the optical axis 46. A magnifier lens 71 is used in the test
of the zoom capability of the MUT 30 and is positioned over the
optical centerline 46 with a stepper motor 81 under the control
of the tester 22. The magnifier lens 71 is positioned along the
optical axis 46 by a stepper motor 80 under the control of the tester
22. The magnifier lens 71 can also be placed above the field lens
43, and the field lens can be exchanged with another field lens
so that the optical distance of the targets contained within the
target wheels 40 and 41 can be modified with respect to MUT 30 in
order to perform the zoom test.
[0034] The MUT 30 can have either an electrically controlled zoom
or a manually controlled zoom. The zoom capability of the MUT expands
or contracts an image incident on the zoom lens to a light sensitive
device contained within the MUT. If the zoom is electrically controlled,
the tester 22 provides a control signal to adjust the zoom contained
within the lens cap 31 of the MUT 30. If the zoom is adjusted manually,
the tester 22 controls a zoom stepper 82 in contact with the lens
cap 31 to vary the zoom of the MUT 30. The zoom stepper 82 is in
addition to and similar to a focus stepper that is needed to focus
the lens of the MUT 30
[0035] In FIG. 2 is a diagram of the optics system 20 of the present
invention in which four focus targets 105, 106, 107 and 108 are
positioned in the target holders 42 of the target wheels 40 and
41. Each target holder 42 has a target position 72 that is furthest
from the MUT and a target position 73 that is closest to the MUT.
The target holders 42 containing the four focus targets 105, 106,
107 and 108 are positioned over the optical centerline 46, and the
focus targets 105, 106, 107 and 108 are positioned within the target
holders 42 such that an image of all for focus targets can be viewed
simultaneously by the MUT. A far focus target 105 is located in
the target position 72 of a target holder 42 in the target wheel
40 furthest from the MUT 30. A first intermediate focus target 106,
which is closer to the MUT 30 than the far focus target 105, is
located in target position 73 of the target holder 42 of target
wheel 40. A second intermediate focus target 107, which is closer
to the MUT 30 than the first intermediate target 106, is located
in target position 72 of a target holder 42 in target wheel 41.
A close focus target 108, which is closest to the MUT, is located
in target position 73 of the target holder 42 in target wheel 41.
[0036] The four focus targets are arranged in the target holders
42 such that all four focus targets 105, 106, 107 and 108 can be
viewed by the MUT 30 at the same time. The target holders are round
in shape and each focus target occupies approximately one fourth,
or ninety degrees, of the target holder. Other shapes of target
holder 42 are within the scope of the present invention depending
upon the requirements of the optics system 20. The tester 22 sets
the distance of the target wheels 40 and 41 from the MUT to values
predetermined in a focus test setup by adjusting the stepper motors
77 and 78, and the tester adjusts the field lens to focus a composite
image of the focus targets (shown in FIG. 2B) onto the lens of the
MUT by controlling the stepper motor 79. A magnifier lens 71 is
moved over the optical centerline 46 by a stepper motor 81 under
the control of the tester 22. The tester controls a stepper motor
80 to vary the distance of the magnifier lens 71 from the MUT to
provide different image sizes to the MUT 30 of the composite image
shown in FIG. 2B. The zoom of the MUT 30 is varied under control
of the tester 22 for each setting of the magnifier lens 71, and
image data from the MUT 30 is coupled to the tester 22 to determine
if the composite image maintains focus as the zoom of the MUT is
changed. The tester 22 monitors the brightness of the composite
image, shown in FIG. 2B, to determine that the focus remains within
acceptable focus limits as the zoom is varied.
[0037] Continuing to refer to FIG. 2A, the tester 22 selects different
colors of light from the light source 45 and the zoom test is repeated
for each color to check the capability of the multiple element lens
system of the MUT 30. The MUT can have either an electrical controlled
zoom or mechanical zoom. If the MUT 30 has an electrically controlled
zoom, the tester 22 provides signals to control the zoom. If the
MUT 30 has a manually adjustable zoom, a zoom stepper mechanism
82 (FIG. 1) in contact with the lens cap 31 rotates the lens cap
zoom adjustment under the control of the tester 22 to vary the zoom
of the MUT 30.
[0038] In FIG. 2B is shown the arrangement of the focus targets
105, 106, 107 and 108 as viewed by the MUT 30. Each of the targets
105, 106, 107 and 108 comprise dark 84 and light areas 83, 86, 91
and 96. The light areas are holes through the material forming the
dark areas 84 that allow light to pass through from the light source
45. The holes are preferably round; however, the holes can have
other physical shape, i.e. oval, rectangular, hexagonal and octagonal.
The arrangement and shape of the holes 83, 86, 91 and 96 are for
illustrative purposes only and are not intended to explicitly define
the focus targets 105, 106, 107 and 108. In the far focus target
105 the light areas 83 are formed by large holes. In the first intermediate
focus target 106 the light areas 86 are formed by holes that are
smaller than the light areas 83 in the far target 105. In the second
intermediate target 107 the light areas 91 are formed by holes that
are smaller than the light areas 86 of the first intermediate focus
target 106, and in the close focus target 108 the light areas 96
are formed by holes that are smaller than the light areas 91 in
the second intermediate focus target 107.
[0039] In FIG. 3A is shown is a diagram of the optics system 20
of the present invention in which a composite focus target 110 is
located in the close target position 73 of a target holder 42 in
the target wheel 41. The composite focus target 110 comprises a
combination into a single focus target of the far, the first intermediate,
the second intermediate and the close focus targets shown in FIGS.
2A and 2B. The location of the composite focus target 110 is for
illustrative purposes, and the composite target can be located in
either target location 72 or 73 in target holders 42 in either target
wheel 40 and 41 depending upon the initial test setup. The determination
of the location of the composite target is made during initial focus
setup when the settings of the optics system 20 are made. During
the initial setup the distance settings of the stepper motors 77,
78 and 79 are made to provide the best focus test of the zoom capability
of the MUT 30. The tester 22 stores the initial setup distances
setting of the stepper motors to be used in the zoom test of product.
[0040] During zoom testing of the MUT 30, the magnifier lens 71
is positioned over the optical centerline 46 by the stepper motor
81 under control of the tester 22. The magnifier lens 71 is moved
during zoom test by the stepper motor 80 under control of the tester
22. At a position closest to the lens cap 31 of the MUT 30 the image
of the composite target 110 has the smallest magnification, and
at a position furthest from the lens cap 31 the image of the composite
target 110 is at a largest magnification. At the different distance
locations of the magnifier lens 71 from the lens cap 31, the zoom
of the MUT 31 is varied under the control of the tester 22, and
the tester 22 monitors image data from the MUT. The brightness of
the image data is used to determine that the focus of the MUT is
maintained during the zoom testing.
[0041] Continuing to refer to FIG. 3A, the tester 22 selects different
colors of light from the light source 45 and the zoom test is repeated
for each color to check the capability of the multiple element lens
system of the MUT 30. The MUT can have either an electrical controlled
zoom or mechanical zoom. If the MUT 30 has an electrically controlled
zoom, the tester 22 provides signals to control the zoom. If the
MUT 30 has a manually adjustable zoom, a zoom stepper mechanism
82 (FIG. 1) in contact with the lens cap 31 rotates the lens cap
zoom adjustment under the control of the tester 22 to vary the zoom
of the MUT 30.
[0042] In FIG. 3B is shown the composite focus target 110 as viewed
by the MUT 30. The composite focus target is constructed of light
areas 83, 86, 91 and 96 and dark areas 84. The light areas 83, 86,
91 and 96 are holes through the material forming the dark areas
84 that allow light from the light source 45 to pass through to
the MUT 30, and the holes can have other physical shape, i.e. oval,
rectangular, hexagonal and octagonal. The holes are of different
size and represent the different distance targets 105, 106, 107
and 108 shown in FIGS. 2A and 2B. The arrangement and shape of the
holes 83, 86, 91 and 91 are for illustrative purposes only and are
not intended to explicitly define the composite target. The larger
target holes 83 represent the far target 105, the target holes 86
represent the first intermediate target 106, the target holes 91
represent the second intermediate target and the smallest target
holes 96 represent the close target, similar to that shown in FIGS.
2A and 2B.
[0043] In FIG. 4A is shown the composite focus target 111 positioned
in a target holder 42 at a skewed angle to the optical centerline
46 of the optics system 20. The skewed angle provides a depth of
field to the view of the MUT 30 during zoom testing where the larger
holes 83 are positioned "U" furthest from the MUT and
the smallest holes 96 are positioned "D" closest to the
MUT. The location of the skewed composite focus target 111 is for
illustrative purposes, and the composite target can be located in
a target holder 42 in either target wheel 40 and 41. The determination
of the location of the composite target is made during initial focus
setup when the settings of the optics system 20 are made. During
the initial setup the distance settings of the stepper motors 77,
78 and 79 are determined to provide the best focus test of the zoom
capability of the MUT 30. The tester 22 stores the initial setup
distance settings of the stepper motors to be used in the zoom test
of product.
[0044] During zoom testing of the MUT 30, the magnifier lens 71
is positioned over the optical centerline 46 by the stepper motor
81 under control of the tester 22, and the magnifier lens 71 is
moved during zoom test by the stepper motor 80 under control of
the tester 22. The magnifier lens 71 positioned closest to the lens
cap 31 of the MUT 30 causes the image of the composite target 111
to have the smallest magnification, and at a position furthest from
the lens cap 31 the image of the composite target 111 is at a largest
magnification. At the different distance locations of the magnifier
lens 71 from the lens cap 31, the zoom of the MUT 31 is varied under
the control of the tester 22, and the tester 22 monitors image data
from the MUT. The brightness of the image data is used to determine
that the focus of the MUT is maintained during the zoom testing.
[0045] Continuing to refer to FIG. 4A, the tester 22 selects different
colors of light from the light source 45 and the zoom test is repeated
for each selected color to check the capability of the multiple
element lens system of the MUT 30. The MUT can have either an electrical
controlled zoom or mechanical zoom. If the MUT 30 has an electrically
controlled zoom, the tester 22 provides signals to control the zoom.
If the MUT 30 has a manually adjustable zoom, a zoom stepper mechanism
82 (FIG. 1) in contact with the lens cap 31 rotates the lens cap
zoom adjustment under the control of the tester 22 to vary the zoom
of the MUT 30.
[0046] In FIG. 4B is shown the composite focus target 111 as viewed
by the MUT 30. The composite focus target is constructed of light
areas 83, 86, 91 and 96 and dark areas 84. The light areas are holes
through the material forming the dark areas 84 that allow light
from the light source 45 to pass through to the MUT 30, and the
holes are preferably round but can have other physical shapes, i.e.
oval, rectangular, hexagonal and octagonal. The holes are of different
size and represent the different distance targets 105, 106, 107
and 108 shown in FIGS. 2A and 2B. The arrangement, shapes and sizes
of the holes 83, 86, 91 and 91, in FIG. 4B, are for illustrative
purposes only and are not intended to explicitly define the composite
target 111. The larger target holes 83 represent the far target
105, the target holes 86 represent the first intermediate target
106, the target holes 91 represent the second intermediate target
and the target holes 96 represent the close target shown in FIGS.
2A and 2B. For illustrative purposes, the hole arrangement in target
111 is shown to be different than that of the target 110 (FIGS.
3A and 3B) as a result of the skew of the target in the target holder
42 and the requirement for the hole size to be in descending size
from the hole 83 furthest from the MUT to the hole 96 closest to
the MUT. The letter "U" identifies the edge of the composite
focus target that is furthest from the MUT and the letter "D"
identifies the edge that is positioned closest to the MUT.
[0047] In FIG. 5 is a flow diagram of the method of the present
invention to test the zoom capability of a miniature digital camera
module under test (MUT). Focus targets are placed into target wheels,
which are controlled by a tester to position the targets over the
optical centerline of an optical system of a test station 200. There
can be one focus target with the composite image, shown in FIGS.
3A and 4A, or there may be as many as four targets positioned simultaneously
over the optical centerline as shown in FIG. 2A. The distance of
the target wheel from the MUT is set 201 by stepper motors controlled
by the tester to cause the target wheels to be at distances from
the MUT predetermined during an initial setup of the zoom test.
The field lens distance from the MUT is set by the tester 202 using
a value predetermined in the initial setup of the zoom test. A light
color is selected 203 and the zoom of the MUT is varied to check
that the focus of the MUT is maintained over the range of the zoom
204. If the zoom of the MUT is electrically adjusted, a signal coupled
from the tester to the MUT changes the zoom setting. If the zoom
of the MUT is manually adjusted, a zoom stepper mechanism in contact
with the lens cap of the MUT is controlled by the tester to turn
the lens cap and adjust the zoom of the MUT.
[0048] Continuing to refer to FIG. 5, a magnifier lens is inserted
between the field lens and the MUT within the optical centerline
of the optics system. The magnifier lens is then positioned along
the optical centerline 205 and the zoom of the MUT is varied to
check that the focus of the target image is maintained over the
range of zoom of the MUT 206. If an additional position of the magnifier
lens is required 207, the magnifier lens is repositioned 205 and
the zoom of the MUT is again varied to check the focus is maintained
over the range of the zoom 206. If an additional position of the
magnifier lens is not required 208 and a next light color is required
209, a next light color is selected 203 and steps 204 through 208
are repeated. Changing the color of light checks the multiple element
zoom lens for focus problems related to a particular color. If the
zoom testing has been tested with all of the light colors 210, the
zoom testing is ended.
[0049] While the invention has been particularly shown and described
with reference to preferred embodiments thereof, it will be understood
by those skilled in the art that various changes in form and details
may be made without departing from the spirit and scope of the invention. |