U.S. patent application number 15/788006 was filed with the patent office on 2019-01-03 for methods and apparatus for focus control in an imaging system.
This patent application is currently assigned to SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. The applicant listed for this patent is SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. Invention is credited to Yoshihisa TABUCHI.
Application Number | 20190004276 15/788006 |
Document ID | / |
Family ID | 64692171 |
Filed Date | 2019-01-03 |
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United States Patent
Application |
20190004276 |
Kind Code |
A1 |
TABUCHI; Yoshihisa |
January 3, 2019 |
METHODS AND APPARATUS FOR FOCUS CONTROL IN AN IMAGING SYSTEM
Abstract
Various embodiments of the present technology may comprise
methods and apparatus for focus control in an imaging system. The
methods and apparatus may comprise various circuits and/or systems
configured to measure the ambient temperature of the lens module
and compute a corrected target position based on known thermal
characteristics of the lens and/or the lens barrel. Factors used to
obtain the corrected target position may comprise the material the
of the lens barrel, the thermal time constant of the lens barrel,
the linear expansion coefficient of the lens barrel, the effective
focal length (EFL) of the lens, the thermal response of the lens,
and/or the temperature characteristic coefficient of the EFL.
Inventors: |
TABUCHI; Yoshihisa;
(Gifu-city, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC |
Phoenix |
AZ |
US |
|
|
Assignee: |
SEMICONDUCTOR COMPONENTS
INDUSTRIES, LLC
Phoenix
AZ
|
Family ID: |
64692171 |
Appl. No.: |
15/788006 |
Filed: |
October 19, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62527540 |
Jun 30, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 5/23212 20130101;
G02B 7/028 20130101; G02B 7/09 20130101; G02B 7/28 20130101; G02B
7/08 20130101 |
International
Class: |
G02B 7/02 20060101
G02B007/02; G02B 7/09 20060101 G02B007/09; G02B 7/28 20060101
G02B007/28; H04N 5/232 20060101 H04N005/232 |
Claims
1. An autofocus apparatus, comprising: a temperature-sensitive
component; a temperature sensor adjacent to the
temperature-sensitive component and configured to: measure an
ambient temperature around the temperature-sensitive component; and
generate temperature data; and a correction circuit coupled to the
temperature sensor and configured to: receive the temperature data;
model a degree of focus of the temperature-sensitive component; and
compute a corrected target position.
2. The autofocus apparatus according to claim 1, wherein the
temperature-sensitive component comprises at least one of: a lens,
a lens barrel, a driving magnet, a spring, a substrate, a sensing
magnet, a position sensor, and an image sensor.
3. The autofocus apparatus according to claim 1, wherein the
correction circuit is further configured to compute a relative
temperature according to a base temperature and the ambient
temperature.
4. The autofocus apparatus according to claim 3, wherein the
correction circuit is further configured to compute a thermal
response of the temperature-sensitive component according to the
relative temperature and a thermal time constant of the
temperature-sensitive component.
5. The autofocus apparatus according to claim 4, wherein the
correction circuit is further configured to compute a position
shift value according to the thermal response of the
temperature-sensitive component.
6. The autofocus apparatus according to claim 5, wherein the
correction circuit utilizes the position shift value and a target
position to compute the corrected target position.
7. The autofocus apparatus according to claim 1, wherein the
temperature-sensitive component comprises a lens module comprising:
a lens and a lens barrel.
8. The autofocus apparatus according to claim 7, wherein the
correction circuit: computes a change in the effective focal length
of the lens according to a thermal response of the lens; and
computes a change in length of the lens barrel according to a
thermal response of the lens barrel.
9. The autofocus apparatus according to claim 7, further comprising
a position sensor configured to detect an actual position of the
lens module, wherein the correction circuit further utilizes the
actual position to compute the corrected target position.
10. A method of operating an autofocus apparatus having a
temperature-sensitive component, comprising: measuring an ambient
temperature of the temperature-sensitive component; computing a
relative temperature according to a base temperature and the
measured ambient temperature; computing a thermal response of the
temperature-sensitive component according to the relative
temperature; and computing a corrected target position according to
the computed thermal response.
11. The method according to claim 10, wherein the
temperature-sensitive component comprises at least one of: a lens,
a lens barrel, a driving magnet, a spring, a substrate, a sensing
magnet, a position sensor, and an image sensor.
12. The method according to claim 11, wherein computing the thermal
response comprises: computing a first thermal response of the lens
according to the relative temperature; and computing a second
thermal response of the lens barrel according to the relative
temperature.
13. The method according to claim 12, further comprising,
computing: a target position of the lens; a position shift value
based on the first and second thermal responses; and a corrected
target position based on the computed position shift value and
computed the target position.
14. The method according to claim 11, further comprising: computing
the change in the effective focal length of the lens according to a
thermal response of the lens; and computing the change in length of
the lens barrel according to a thermal response of the lens
barrel.
15. An imaging system, comprising: an image signal processor
configured to generate a target position signal; and a camera
module coupled to the image signal processor, comprising: an image
sensor; a lens module positioned adjacent to the image sensor,
comprising: a lens coupled to a lens barrel; and a control circuit
responsive to the image signal processor and configured to generate
a drive signal for moving the lens module, comprising: a
temperature sensor positioned adjacent to the lens module and
configured to: measure an ambient temperature of the lens module;
and generate temperature data; and a correction circuit coupled to
the temperature sensor and configured to: receive the generated
temperature data; and compute a corrected target position
utilizing: the generated temperature data; the target position
signal; a thermal response of the lens; and a thermal response of
the lens barrel.
16. The imaging system according to claim 15, wherein the
correction circuit is further configured to compute a relative
temperature according to a base temperature and the ambient
temperature.
17. The imaging system according to claim 15, wherein the
correction circuit is further configured to: compute a change in an
effective focal length of the lens; compute a thermal expansion of
the lens barrel; and compute a position shift value according to
the change in the effective focal length of the lens and the
thermal expansion of the lens barrel.
18. The imaging system according to claim 17, wherein: the change
in effective focal length of the lens is based on a temperature
characteristic coefficient; and the change in length of the lens
barrel is based on a linear expansion coefficient.
19. The imaging system according to claim 18, wherein the
correction circuit utilizes the position shift value and the target
position signal to compute the corrected target position.
20. The imaging system according to claim 15, wherein: the thermal
response of the lens is based on the ambient temperature and a
thermal time constant of the lens; and the thermal response of the
lens barrel is based on the ambient temperature and a thermal time
constant of the lens barrel.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 62/527,540, filed on Jun. 30, 2017, and
incorporates the disclosure of the application in its entirety by
reference.
BACKGROUND OF THE TECHNOLOGY
[0002] Electronic devices, such as cellular telephones, cameras,
and computers, commonly use a lens module, comprising a lens and a
lens barrel, in conjunction with an image sensor to capture images.
Many imaging systems employ autofocus methods and various signal
processing techniques to improve image quality by adjusting the
position of the lens relative to the image sensor.
[0003] Autofocus systems generally employ an actuator to move the
lens module to an optimal position to increase the image quality.
In operation, heat generated by the image sensor and/or the control
circuit, as well as heat from an external source, may increase the
ambient temperature of the lens module. Changes in the ambient
temperature may cause components, such as the lens barrel and the
lens, to contract or expand. This may cause the position of the
lens, relative to the image sensor, to deviate from the optimal
position resulting in an out-of-focus image.
SUMMARY OF THE INVENTION
[0004] Various embodiments of the present technology may comprise
methods and apparatus for focus control in an imaging system. The
methods and apparatus may comprise various circuits and/or systems
configured to measure the ambient temperature of the lens module
and compute a corrected target position based on known thermal
characteristics of the lens and/or the lens barrel. Factors used to
obtain the corrected target position may comprise the material the
of the lens barrel, the thermal time constant of the lens barrel,
the linear expansion coefficient of the lens barrel, the effective
focal length (EFL) of the lens, the thermal response of the lens,
and the temperature characteristic coefficient of the EFL.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A more complete understanding of the present technology may
be derived by referring to the detailed description when considered
in connection with the following illustrative figures. In the
following figures, like reference numbers refer to similar elements
and steps throughout the figures.
[0006] FIG. 1 is a block diagram of an autofocus system in
accordance with an exemplary embodiment of the present
technology;
[0007] FIG. 2 is a block diagram of a portion of a closed-loop
autofocus system in accordance with an exemplary embodiment of the
present technology;
[0008] FIG. 3 is a block diagram of a portion of an open-loop
autofocus system in accordance with an exemplary embodiment of the
present technology;
[0009] FIG. 4 is a block diagram of a correction circuit in
accordance with an exemplary embodiment of the present
technology;
[0010] FIGS. 5A-B are cross-sectional views of an imaging system
and representatively illustrates the effect of heat on various
components of the autofocus system in accordance with an exemplary
embodiment of the present technology;
[0011] FIG. 6 is a graph of the ambient temperature versus time in
accordance with an exemplary embodiment the present technology;
[0012] FIG. 7 is a graph of an actual degree of focus of an
autofocus system versus time in accordance with an exemplary
embodiment of the present technology;
[0013] FIG. 8 is a flowchart for adjusting the actuator according
to individual component calculations in accordance with an
exemplary embodiment of the present technology;
[0014] FIG. 9 is a graph of a predicted degree of focus of an
autofocus system versus time in accordance with an exemplary
embodiment of the present technology; and
[0015] FIG. 10 is a graph of an actual degree of focus versus time
after a position shift value has been applied in accordance with an
exemplary embodiment of the present technology.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0016] The present technology may be described in terms of
functional block components and various processing steps. Such
functional blocks may be realized by any number of components
configured to perform the specified functions and achieve the
various results. For example, the present technology may employ
various types of actuators, image sensors, position sensors,
temperature sensors, and the like, which may carry out a variety of
functions. In addition, the present technology may be practiced in
conjunction with any number of applications, and the apparatus
described is merely one exemplary application for the technology.
Further, the present technology may employ any number of
conventional techniques for performing various computations,
processing image data, and the like.
[0017] The present technology may be used in conjunction with any
suitable electronic device or system, such as a digital camera,
smartphone, laptop, portable device, and the like. Referring now to
FIG. 1, in an exemplary embodiment of the present technology, an
imaging system 100 is capable of performing automatic focus
(autofocus). According to an exemplary embodiment, and to improve
the autofocus function, the imaging system 100 is configured to
predict the individual thermal response of various components
according to an ambient temperature T and compute a position shift
value P.sub.SFT and a corrected target position
P.sub.TARGET.sub._.sub.COR according to the thermal responses of
various components. The imaging system 100 may comprise any
suitable device and/or system configured to focus an image on a
sensing surface and capture image data. For example, in an
exemplary embodiment, the imaging system 100 may comprise a camera
module 105 and an image signal processor (ISP) 125.
[0018] The camera module 105 may capture image data and perform
various operating functions, such as autofocus and/or optical image
stabilization. The camera module 105 may comprise a lens assembly
110, an image sensor 120 to capture image data, an actuator 140
configured to move the lens assembly 110, and a control circuit
115. According to various embodiments, the camera module 105
further comprises a housing (not shown) that either partially or
entirely encases the lens assembly 110, the image sensor 120, and
the control circuit 115. According to various embodiments, the
camera module 105 may further comprise one or more springs (not
shown) connecting the lens assembly 110 to the housing.
[0019] The image sensor 120 may be suitably configured to capture
image data. For example, the image sensor 120 may comprise a pixel
array (not shown) to detect light and convey information that
constitutes an image by converting the variable attenuation of
light waves (as they pass through or reflect off the object) into
electrical signals. The pixel array may comprise a plurality of
pixels arranged in rows and columns, and the pixel array may
contain any number of rows and columns, for example, hundreds or
thousands of rows and columns. Each pixel may comprise any suitable
photosensor, such as a photogate, a photodiode, and the like, to
detect light and convert the detected light into a charge. The
image sensor 120 may be implemented in conjunction with any
appropriate technology, such as active pixel sensors in
complementary metal-oxide-semiconductors (CMOS) and charge-coupled
devices. In various embodiments, the image sensor 120 may be
mounted on a printed circuit board (PCB) 500 (FIG. 5).
[0020] The actuator 140 may be configured to move the lens assembly
110 along various axes (e.g., along an x-, y-, and/or z-axis) to
improve image quality. The actuator 140 may comprise any suitable
device or system capable of moving and/or repositioning the lens
assembly 110 in response to a signal. The actuator 140 may be
configured to move the lens assembly 110 for the purpose of
performing autofocus functions, counteracting involuntary
movements, such as hand jitter or shaking, and the like. For
example, in one embodiment, the actuator 140 may comprise a voice
coil motor, comprising a driving magnet (not shown) and a sensing
magnet (not shown), that is responsive to a control signal from the
control circuit 115. The actuator 140 may be limited in the amount
of movement it can perform, whether self-limiting or due to the
design of the system. For example, the camera module 105 may
comprise a housing (not shown), with sidewalls, to house the lens
assembly 110, the actuator 140, and the image sensor 120. As such,
a maximum range of movement the actuator 140 may impart to the lens
assembly 110 may be limited by the interior dimensions of the
camera module housing.
[0021] According to various embodiments, portions of the actuator
140, such as the sensing magnet, may be physically coupled to the
lens barrel 135. In other embodiments, however, the actuator 140
may be positioned within or adjacent to the lens assembly 110. The
particular arrangement may be based on the type of actuator 140
used, the size and shape of the lens assembly 110, design choices,
and the like.
[0022] The lens assembly 110 may be configured to focus light on a
sensing surface of the image sensor 120. For example, according to
various embodiments, the lens assembly 110 is positioned adjacent
to the image sensor 120. The lens assembly 110 may comprise a lens
to focus an image on the image sensor 120 and a lens barrel 135 to
hold the lens. The lens assembly 110, the actuator 140, and the
control circuit 115 may operate in conjunction with each other to
provide an autofocus function. For example, the actuator 140
responds to the control circuit 115 to move the lens assembly 110
either closer to or away from the image sensor 120 to focus the
image on the image sensor 120.
[0023] The lens 130 may comprise any lens or lens system suitable
for focusing light on the image sensor 120 and may be positioned
adjacent to a sensing surface of the image sensor 120. The lens 130
may be adjustable or fixed relative to the image sensor 120. For
example, in an exemplary embodiment, the lens 130 may be coupled to
the actuator 140 and configured to move along a plane that is
perpendicular to the sensing surface of the image sensor 120 (i.e.,
movement closer to or away from the surface of the image sensor, in
a z-direction). The lens 130 may further be configured to move
along a plane that is parallel to the sensing surface of the image
sensor 120 (i.e., in an x-direction and in a y-direction). In
various embodiments, the lens 130 may comprise a plurality of lens
elements arranged adjacent to each other. The lens 130 may be
formed using any suitable material, such as glass, quartz glass,
fluorite, germanium, meteoritic glass, polycarbonate, plastic,
high-index plastic, and the like, or any combination thereof.
[0024] The lens barrel 135 comprises a structure configured to hold
the lens 130. For example, various mounting techniques may be
employed to mount the lens 130 to the lens barrel 135, such as hard
mounting, drop-in mounting, elastomeric mounting, and the like. The
lens barrel 135 may further comprise various elements to maintain
proper air spacing and/or alignment of the lens 130 (or lens
elements), such as retainer rings, snap rings, spun rims, and the
like.
[0025] The lens barrel 135 may be formed using metals, such as
aluminum, stainless steel, beryllium, titanium, and metal alloys,
and/or nonmetals, such as glass, carbon fiber composites, or
plastic, wherein each material may be described according to a
coefficient of thermal expansion. As such, the lens barrel 135 may
expand and contract based the type of material used to form the
lens barrel 135. For example, a lens barrel 135 comprising metal
may have a larger coefficient of thermal expansion than a lens
barrel 135 comprising glass. In various embodiments, the material
used to form the lens barrel 135 may differ from that used to form
the lens 130.
[0026] In various embodiments, the camera module 105 may further
configured to measure the position of the lens relative to the
image sensor 120 and to measure a temperature of the camera module
105. For example, according to an exemplary embodiment, the camera
module 105 comprises a position sensor 145 and a temperature sensor
150.
[0027] The position sensor 145 detects movement and a position of
the lens 130. The position sensor 145 may comprise any suitable
circuit for determining the position of the lens 130, such as a
hall sensor. In such a case, the position sensor 145 may determine
the position of the lens 130 by varying an output voltage in
response to a magnetic field. The output voltage may correspond to
a magnitude and direction the lens 130 relative to a reference
point. According to various embodiments, the position sensor 145
may be formed on the same chip as the control circuit 115. In
alternative embodiments, the position sensor 145 may be formed on a
companion chip.
[0028] The temperature sensor 150 may be suitably configured to
monitor and report the ambient temperature T inside and/or outside
of the imaging system 100. The temperature sensor 150 may comprise
any suitable device for monitoring and reporting temperature, such
as a thermistor. The temperature sensor 150 may be configured to
transmit a signal corresponding to the measured ambient temperature
T of the imaging system 100 to the temperature register 225.
According to various embodiments, the temperature sensor 150 may be
formed on the same chip as the control circuit 115. In alternative
embodiments, the temperature sensor 150 may be formed on a
companion chip.
[0029] In various embodiments, the ISP 125 may perform various
digital signal processing functions, such as color interpolation,
color correction, facilitate autofocus, exposure adjustment, noise
reduction, white balance adjustment, compression, and the like, to
produce an output image. In an exemplary embodiment, the ISP 125
may be configured to receive and process image data to determine a
degree of focus of an image (i.e., the amount that the image is
in-focus/out-of-focus). The degree of focus may be represented by a
numerical value. The ISP 125 may utilize the numerical value to
further determine an initial target position
P.sub.TARGET.sub._.sub.0 for the lens 130 (and lens barrel 135),
wherein the initial target position P.sub.TARGET.sub._.sub.0
represents a required position of the lens 130 to focus the image.
In general, the ISP 125 does not utilize information related to
physical changes of the lens 130 and/or lens barrel 135 to
determine the initial target position P.sub.TARGET.sub._.sub.0.
[0030] The ISP 125 may comprise any number of devices and/or
systems for performing calculations, transmitting and receiving
image pixel data, measuring the degree of focus, and a storage unit
for storing pixel data, such as random-access memory, non-volatile
memory or any other memory device suitable for the particular
application. Further, the ISP 125 may utilize any suitable
techniques and/or methods for determining and/or calculating the
degree of focus of the image. In various embodiments, the ISP 125
may be implemented with a programmable logic device, such as a
field programmable gate array (FPGA) or any other device with
reconfigurable digital circuits. In other embodiments, the ISP 125
may be implemented in hardware using non-programmable devices. The
ISP 125 may be formed partially or entirely within an integrated
circuit in silicon using any suitable CMOS techniques or
fabrication processes, in an ASIC (application-specific integrated
circuit), using a processor and memory system, or using another
suitable implementation.
[0031] The ISP 125 may transmit the output image to an output
device, such as a display screen or a memory component, for storing
and/or viewing the image data. The output device may receive
digital image data, such as video data, image data, frame data,
and/or gain information from the ISP 125. In various embodiments,
the output device may comprise an external device, such as a
computer display, memory card, or some other external unit.
[0032] Referring to FIGS. 1-3, the control circuit 115 controls and
supplies power to various devices within the system. For example,
the control circuit 115 may control and supply power to the
actuator 140 to move the lens module 110 to a desired position.
According to various embodiments, the control circuit 115 may
supply a current, having a magnitude and direction, to the actuator
140. In general, the actuator 140 responds to the current by moving
the lens module 110 an amount that is proportional to the amount of
power supplied by the control circuit 115.
[0033] The control circuit 115 may comprise any suitable device
and/or system capable of providing energy to the actuator 140. For
example, the control circuit 115 may comprise a driver circuit 205
to provide a current to the actuator 140, wherein the actuator 140
responds to the magnitude and sign of the current by moving the
lens module 110.
[0034] The driver circuit 205 facilitates movement of the lens
module 110 to a desired position. The driver circuit 205 may
comprise any suitable circuit for varying a voltage across the
circuit in order to maintain a constant electrical current output
in response to a control signal. For example, the driver circuit
205 may receive and respond to the corrected target position
P.sub.TARGET.sub._.sub.COR from an operation unit 200 by generating
a drive signal S.sub.DR. The driver circuit 205 may apply the drive
signal S.sub.DR to the actuator 140, wherein the drive signal
S.sub.DR may correspond to the corrected target position
P.sub.TARGET.sub._.sub.COR. Alternatively or additionally, the
driver circuit 205 may facilitate movement of the lens 130 and/or
lens barrel 135 to achieve a desired position by controlling the
current to the actuator 140, which in turn controls the magnitude
and direction of movement of the lens module 110. For example, the
driver circuit 205 may generate the current in either a first
direction or an opposite second direction. The direction of the
current may be computed according to the desired target
position.
[0035] According to various embodiments, the control circuit 115
may operate in conjunction with and receive various signals from
the ISP 125, the image sensor 120, and other sensor circuits, such
as the position sensor 145 and the temperature sensor 150, to
determine an appropriate amount of power to supply to the actuator
140 and/or an appropriate position for the lens module 110. For
example, in an exemplary embodiment, the control circuit 115 may be
coupled to and configured to receive the initial target position
P.sub.TARGET.sub._.sub.0 from the ISP 125. In various embodiments,
the control circuit 115 may further receive a feedback signal from
the actuator 140.
[0036] According to various embodiments, the control circuit 115
may further refine the initial target position
P.sub.TARGET.sub._.sub.0. For example, the control circuit 115 may
be configured to compute the corrected target position
P.sub.TARGET.sub._.sub.COR. The corrected target position
P.sub.TARGET.sub._.sub.COR may be the position of the lens 130
and/or lens barrel 135 that provides optimal image quality and/or a
focused image. The control circuit 115 may comprise any device
and/or system suitable for storing various data, performing logic
functions, modulate a control signal, and/or performing various
computations. For example, the control circuit 115 may comprise the
operation unit 200 configured to store data and perform various
computations. The operation unit 200 may be coupled to the driver
circuit 205 and provide the driver circuit 205 with position
information.
[0037] According to one embodiment, the position sensor 145 and the
operation unit 200 may be formed on the same chip. In an
alternative embodiment, the position sensor 145 may be formed on a
companion chip. Similarly, the temperature sensor 150 may be formed
on the same chip as the operation unit 200 or on a companion
chip.
[0038] According to various embodiments, the operation unit 200 may
comprise a target adjustment circuit 245. The target adjustment
circuit 245(A/B) may be configured to further revise, refine,
and/or adjust the initial target position P.sub.target.sub._.sub.0.
For example, the target adjustment circuit 245(A/B) may utilize the
initial target position P.sub.TARGET.sub._.sub.0 and adjust the
initial target position P.sub.TARGET.sub._.sub.0 according to
various methods and techniques. In one embodiment, and referring to
FIG. 2, the target adjustment circuit 245(A) may be configured to
operate according to the methods and techniques disclosed in U.S.
Pat. No. 9,520,823. In an alternative embodiment, and referring to
FIG. 3, the target adjustment circuit 245(B) may be configured to
operate according to the methods and techniques disclosed in U.S.
patent application Ser. No. 15/450,640, filed Mar. 6, 2017. The
target adjustment circuit 245 may be further configured to transmit
the intermediate target position to an adder circuit 240. For
example, an output terminal of the target adjustment circuit
245(A/B) may be coupled to an input terminal of the adder circuit
240.
[0039] According to various embodiments, the operation unit 200 may
comprise one or more adder circuits 240, wherein each adder circuit
240 is configured to sum (i.e., add) one or more input values. The
adder circuit 240 may comprise any device and/or system suitable
for summing.
[0040] According to an exemplary embodiment, and referring to FIG.
2, the operation unit 200 may comprise a first adder circuit 240(1)
configured to receive and sum data from the target adjustment
circuit 245(A) with an actual position P.sub.ACTUAL of the lens
module 110 to generate the target position P.sub.TARGET. In the
present case, the operation unit 200 further comprises a second
adder circuit 240(2) configured to receive and sum the target
position P.sub.TARGET and the position shift value P.sub.SFT to
generate the corrected target position P.sub.TARGET.sub._.sub.COR.
In the present case, the second adder circuit 240(2) may be coupled
to and configured to transmit the corrected target position
P.sub.TARGET.sub._.sub.COR to an equalizer circuit 235 for further
processing and/or modulation prior to being transmitted to the
driver circuit 205.
[0041] In various embodiments, such as in a closed-loop system, the
control circuit 115 and/or operation unit 200 may comprise the
equalizer circuit 235. The equalizer circuit 235 may be configured
to calculate an error value and apply a correction based on
proportional, integral and derivative terms, and operate to
minimize the error over time by adjusting a selected control
variable. For example, the equalizer circuit 235 may comprise a
conventional PID controller circuit (not shown) comprising a P
controller to account for present values of the error, an I
controller to account for past values of the error, and a D
controller to account for possible future trends of the error,
based on a current rate of change. In various embodiments, the
equalizer circuit 235 may further comprise a filter (not shown)
coupled to the PID controller to remove noise from various PID
process signals.
[0042] According to an alternative embodiment, and referring to
FIG. 3, the operation unit 200 comprises the second adder circuit
240(2) configured to receive and sum the target position
P.sub.TARGET and the position shift value P.sub.SFT, and generate
the corrected target position P.sub.TARGET.sub._.sub.COR. In the
present case, however, the target adjustment circuit 245(B)
generates the target position P.sub.TARGET and the second adder
circuit 240(2) may be coupled to and configured to transmit the
corrected target position P.sub.TARGET.sub._.sub.COR directly to
the driver circuit 205.
[0043] According to various embodiments, the operation unit 200 may
be configured to store temperature data and other relevant data.
For example, the operation unit 200 may comprise a temperature
register 225 to store temperature data from the temperature sensor
150. The operation unit 200 may further comprise other registers to
store other data, such as the target position P.sub.TARGET.
[0044] The temperature register 225 may be configured to store
relevant data and communicate with the temperature sensor 150
and/or the correction circuit 230. For example, the register 235
may receive and store various temperature data (e.g., the ambient
temperature T) from the temperature sensor 150, and transmit the
temperature data to the correction circuit 230 or allow the
correction circuit 230 to access the temperature data to perform
various calculations. The register 235 may comprise any suitable
memory or storage device capable of storing data.
[0045] Referring to FIGS. 1 and 4, according to various
embodiments, the correction circuit 230 individually models the
degree of focus shift due to ambient temperature changes of one or
more temperature-sensitive components in the imaging system 100,
such as: the lens 130, the lens barrel 135, the image sensor 120,
the position sensor 145, the driving magnet (not shown), the
sensing magnet (not shown), the spring (not shown), the PCB (not
shown), and the like, and utilizes the model information to correct
defocusing. In various embodiments, the correction circuit 230 may
utilize known thermal characteristics of various
temperature-sensitive components to determine the degree of focus
shift and/or the corrected target position
P.sub.TARGET.sub._.sub.COR. In various embodiments, the correction
circuit 230 may comprise any suitable number of computation
circuits, storage devices, and the like.
[0046] For example, in an exemplary embodiment, the correction
circuit 230 is configured to compute a thermal response
.DELTA.T.sub.L and a change in an effective focal length (EFL)
.DELTA.EFL of the lens 130, and a thermal response .DELTA.T.sub.B
and a change in length .DELTA.L (i.e., thermal expansion) of the
lens barrel 135 to correct. In addition, the correction circuit 230
may be further configured to compute the position shift value
P.sub.SFT according to the thermal response and the effective focal
length. The correction circuit 230 may be coupled to and configured
to transmit the position shift value PSFT to the second adder
circuit 240(2).
[0047] According to an exemplary embodiment, the correction circuit
230 may comprise a base temperature register 400 to store a
predetermined base temperature T.sub.BASE, for example 25 degrees
Celsius. The correction circuit 230 may further comprise a
plurality of computation circuits 405, 410, 415, 420 wherein each
computation circuit 405, 410, 415, 420 is configured to employ a
predetermined formula to compute a desired variable.
[0048] The correction circuit 230 may further comprise other
circuitry suitable for performing computations, such as addition,
subtraction, and the like, to compute the position shift value
P.sub.SFT. For example, according to an exemplary embodiment, the
correction circuit 230 may comprise a third adder circuit 240(3)
configured to compute the relative temperature .DELTA.T, given
by:
.DELTA.T=T-T.sub.BASE (Formula 1)
where T is the ambient temperature and T.sub.BASE is the base
temperature.
[0049] The first computation circuit 405 may be configured to
compute a change in the temperature .DELTA.T.sub.L (i.e., thermal
response) of the lens 130, given by:
.DELTA. T L = 1 1 + R LT C LT .times. s .times. .DELTA. T , (
Formula 2 ) ##EQU00001##
where R.sub.LTC.sub.LT is the thermal time constant of the lens,
.DELTA.T is the change in ambient temperature, and s is time in
seconds.
[0050] The second computation circuit 410 may be configured to
compute a change in the effective focal length .DELTA.EFL of the
lens 130, given by:
.DELTA.EFL=.DELTA.T.sub.L.times.C.sub.EFL (Formula 3),
where .DELTA.TL is the thermal response of the lens as computed in
Formula 1 and C.sub.EFL is the temperature characteristic
coefficient of the EFL.
[0051] The third computation circuit 415 may be configured to
compute a change in the temperature .DELTA.T.sub.B (i.e., thermal
response) of the lens barrel 135, given by:
.DELTA. T B = 1 1 + R BT C BT .times. s .times. .DELTA. T , (
Formula 4 ) ##EQU00002##
where R.sub.BTC.sub.BT is the thermal time constant of the lens
barrel 135 and .DELTA.T is the change in ambient temperature.
[0052] The fourth computation circuit 420 may be configured to
compute a change in the length .DELTA.L of the lens barrel 135,
given by:
.DELTA.L=L.sub.BASE.times..alpha..times..DELTA.T.sub.B (Formula
5),
where L.sub.BASE is the base length of the lens barrel 135, a is
the linear expansion coefficient of the lens barrel 135, and
.DELTA.T.sub.B is the change in temperature of the lens barrel 135
as computed in Formula 4.
[0053] The correction circuit 230 may further comprise a fourth
adder circuit 240(4) to compute the position shift value P.sub.SFT,
given by:
P.sub.SFT=.DELTA.EFL+.DELTA.L (Formula 6),
where .DELTA.EFL is the change in effective focal length of the
lens as calculated in Formula 3 and .DELTA.L is the change in the
length of the lens barrel 135 as calculated in Formula 5. The
fourth adder circuit 240(4) may be coupled to the second adder
circuit 240(2), wherein the second adder circuit 240(2) may be
configured to compute the corrected target position
P.sub.TARGET.sub._.sub.COR, given by:
P.sub.TARGET.sub._.sub.COR=P.sub.TARGET-P.sub.FT (Formula 7),
where P.sub.TARGET is the target position provided by the ISP 125
and P.sub.SFT is the position shift value according to Formula
6.
[0054] According to alternative embodiments where the correction
circuit 230 models the degree of focus according to different
temperature-sensitive components, such as the springs, the driving
magnet, and/or the sensing magnet, the thermal response and effects
of the thermal response may be determined for each component in the
same or similar manner as above.
[0055] In operation, the imaging system 100 utilizes various
equations to individually model the thermal response of multiple
components of the imaging system 100 to adjust the target position
of the lens module 110. According to various embodiments, the
imaging system 100 may adjust the target position according to an
ambient temperature of the imaging system 100 and utilize the
ambient temperature to compute a thermal response and a change in
the thermal expansion of the lens barrel 135, and a thermal
response and a change in the effective focal length of the lens
130. According to various embodiments, the imaging system 100
utilizes these variables to further compute the position shift
value, which is used to adjust the target position of the lens
module 110 to determine the corrected target position.
[0056] In an exemplary operation, and referring to FIGS. 1, 3, 4,
5A-B, and 8, the imaging system 100 may be configured to detect the
ambient temperature T (805). For example, the imaging system 100
may utilize the temperature sensor 150 to measure and/or detect the
ambient temperature T of the camera module 105. The imaging system
100 may further store and/or update the ambient temperature T
(810). For example, the temperature register 225 may store a
current ambient temperature T. The temperature sensor 150 and the
temperature register 225 may operate in conjunction to detect and
store a measured ambient temperature T at predetermined time
intervals.
[0057] The imaging system 100 may further calculate the relative
temperature .DELTA.T (815). For example, the correction circuit 230
may utilize the base temperature T.sub.BASE stored in the base
temperature register 400 and the ambient temperature T stored in
the temperature register 225 to compute the relative temperature
.DELTA.T according to Formula 1. According to an exemplary
embodiment, the adder circuit 240(4) may be utilized to compute
Formula 1.
[0058] The imaging system 100 may then utilize the relative
temperature .DELTA.T to model the position shift of the lens 130
(820). For example, the correction circuit 230 may employ the first
computation circuit 405 to compute the thermal response of the lens
according to Formula 2 (825). The correction circuit 230 may then
employ the second computation circuit 410 to compute the change in
effective focal length of the lens 130 according to Formula 3
(830).
[0059] The imaging system 100 may further utilize the relative
temperature .DELTA.T to model the thermal expansion of the lens
barrel 135 (835). For example, the correction circuit 230 may
employ the third computation circuit 415 to compute the thermal
response .DELTA.T.sub.B of the lens barrel 135 according to Formula
4 (840). The correction circuit 230 may then employ the fourth
computation circuit 420 to compute the change in length .DELTA.L of
the lens barrel 135 according to Formula 5 (845).
[0060] The imaging system 100 may then utilize the change in length
.DELTA.L of the lens barrel 135 and the change in effective focal
length .DELTA.EFL of the lens 130 to calculate the position shift
value P.sub.SFT (850). For example, the correction circuit 230 may
employ the adder circuit 240(5) to compute the position shift value
P.sub.SFT according to Formula 6.
[0061] The imaging system 100 may then utilize the position shift
value P.sub.SFT and the target position P.sub.TARGET to compute the
corrected target position P.sub.TARGET.sub._.sub.COR. For example,
the operation unit 200 may employ the second adder circuit 240(2)
to compute the corrected target position P.sub.TARGET.sub._.sub.COR
according to Formula 7. The imaging system 100 may continue to
adjust the target position by continuously measuring the ambient
temperature T, updating the temperature data in the temperature
register 225, re-computing the thermal response (e.g.,
.DELTA.T.sub.L, .DELTA.T.sub.B) and other relevant variables (e.g.,
.DELTA.L, .DELTA.EFL) relating to the lens 130 and lens barrel 135,
and recalculating the position shift value P.sub.SFT and corrected
target position P.sub.TARGET.sub._.sub.COR (860). For example, the
imaging system 100 may perform the operation according to a
predetermined time interval, such as every 5 seconds after an
initial start-up (800).
[0062] In operation and over some period of time, it is observed
that the imaging system 100 is able to substantially predict (i.e.,
model) the thermal response of the lens 130 and lens barrel 135 and
resulting deviation of the lens 130 from the target position as a
result of changes in the ambient temperature, for example as
illustrated in FIG. 9 and FIG. 6, respectively, and described
according to the degree of focus. FIG. 7 illustrates the degree of
focus that would normally occur as a result of temperature changes
and the effect on the lens 130 and the lens barrel 135. When the
correction circuit 230 subtracts the position shift value P.sub.SFT
from the target position P.sub.TARGET, the degree of focus that
would normally occur as a result of temperature changes is
effectively cancelled out, for example as illustrated in FIG. 10.
Accordingly, the degree of focus is improved (e.g., deviation of
the lens 130 from the target position is decreased, resulting in an
improved (i.e., focused) image.
[0063] In the foregoing description, the technology has been
described with reference to specific exemplary embodiments. The
particular implementations shown and described are illustrative of
the technology and its best mode and are not intended to otherwise
limit the scope of the present technology in any way. Indeed, for
the sake of brevity, conventional manufacturing, connection,
preparation, and other functional aspects of the method and system
may not be described in detail. Furthermore, the connecting lines
shown in the various figures are intended to represent exemplary
functional relationships and/or steps between the various elements.
Many alternative or additional functional relationships or physical
connections may be present in a practical system.
[0064] The technology has been described with reference to specific
exemplary embodiments. Various modifications and changes, however,
may be made without departing from the scope of the present
technology. The description and figures are to be regarded in an
illustrative manner, rather than a restrictive one and all such
modifications are intended to be included within the scope of the
present technology. Accordingly, the scope of the technology should
be determined by the generic embodiments described and their legal
equivalents rather than by merely the specific examples described
above. For example, the steps recited in any method or process
embodiment may be executed in any order, unless otherwise expressly
specified, and are not limited to the explicit order presented in
the specific examples. Additionally, the components and/or elements
recited in any apparatus embodiment may be assembled or otherwise
operationally configured in a variety of permutations to produce
substantially the same result as the present technology and are
accordingly not limited to the specific configuration recited in
the specific examples.
[0065] Benefits, other advantages and solutions to problems have
been described above with regard to particular embodiments. Any
benefit, advantage, solution to problems or any element that may
cause any particular benefit, advantage or solution to occur or to
become more pronounced, however, is not to be construed as a
critical, required or essential feature or component.
[0066] The terms "comprises", "comprising", or any variation
thereof, are intended to reference a non-exclusive inclusion, such
that a process, method, article, composition or apparatus that
comprises a list of elements does not include only those elements
recited, but may also include other elements not expressly listed
or inherent to such process, method, article, composition or
apparatus. Other combinations and/or modifications of the
above-described structures, arrangements, applications,
proportions, elements, materials or components used in the practice
of the present technology, in addition to those not specifically
recited, may be varied or otherwise particularly adapted to
specific environments, manufacturing specifications, design
parameters or other operating requirements without departing from
the general principles of the same.
[0067] The present technology has been described above with
reference to an exemplary embodiment. However, changes and
modifications may be made to the exemplary embodiment without
departing from the scope of the present technology. These and other
changes or modifications are intended to be included within the
scope of the present technology, as expressed in the following
claims.
* * * * *