# US 10,123,003 B2 · Method for calibrating an image capture device

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- Number: US 10,123,003 B2
- Document ID: US10123003B2
- Status: Granted
- Kind: B2
- Application number: 15/323,411
- Filed: 2015-05-28
- Published: 2017-06-01
- Granted: 2018-11-06
- Earliest claimed: 2014-07-01
- Assignees: FotoNation Limited
- Applicants: FotoNation Limited
- Inventors: Alexandru Malaescu; Florin Nanu; Petronel Bigioi; Peter Corcoran
- Web page: https://patentgrep.com/patent/US10123003B2

## CPC

- H04N 17/002: {for television cameras}
- G02B 7/08: adapted to co-operate with a remote control mechanism
- G02B 7/102: {controlled by a microcomputer (cameras with interchangeable lenses G03B17/14)}
- G02B 7/28: Systems for automatic generation of focusing signals
- G02B 7/36: using image sharpness techniques {, e.g. image processing techniques for generating autofocus signals (image data processing per se G06T; in cameras having a solid state image sensor H04N23/67)}
- H04N 23/673: {based on contrast or high frequency components of image signals, e.g. hill climbing method}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A method for calibrating an image capture device comprises mounting at least one sample device from a batch for movement through a plurality of orientations relative to a horizontal plane. For a given orientation, the sample device is focused at a sequence of positions, each position being at a respective focus distance from the device. A lens actuator setting is recorded for the sample device at each position. This is repeated at a plurality of distinct orientations of the sample device. Respective relationships are determined between lens actuator settings at any given position for distinct orientations from the plurality of distinct orientations and actuator settings at a selected orientation of the plurality of distinct orientations. Lens actuator settings for the image capture device to be calibrated are recorded at least at two points of interest (POI), each a specified focus distance from the device with the image capture device positioned at the selected orientation. The image capture device is calibrated for the plurality of distinct orientations based on the determined relationships and the recorded lens actuator settings.

## Claims

### Claim 1

A method for calibrating an image capture device comprising:
a) mounting at least one sample device from a batch for movement through a plurality of orientations relative to a horizontal plane,
b) for a given orientation, focusing said sample device at a sequence of positions, each position being at a respective focus distance from said device;
c) recording a lens actuator setting for said sample device at each position;
d) repeating steps b) and c) at a plurality of distinct orientations of said sample device;
e) repeating steps a) to d) for a number of sample devices from the batch;
f) determining respective relationships between lens actuator settings at any given position for distinct orientations from said plurality of distinct orientations and actuator settings at a selected orientation of said plurality of distinct orientations, and statistically analyzing the recorded lens actuator settings for said sample devices to determine said relationships;
g) recording lens actuator settings for said image capture device to be calibrated at least at two points of interest (POI), each a specified focus distance from said device with said image capture device positioned at said selected orientation; and
h) calibrating said image capture device for said plurality of distinct orientations based on said determined relationships and said recorded lens actuator settings.

### Claim 2 (depends on 1)

A method according to claim 1 comprising positioning a test pattern at each specified focus distance from said device to enable said device to focus at said specified focus distance.

### Claim 3 (depends on 1)

A method according to claim 1 wherein step f) comprises recording said lens actuator settings at each of a camera macro and infinity setting and interpolating lens actuator settings for each POI between said macro and infinity settings at said selected orientation according to a modelled relationship between lens actuator setting and focus distance.

### Claim 4 (depends on 3)

A method according to claim 3 wherein said image capture device includes a camera module including a MEMS actuated lens and wherein said modelled relationship is of the form Capacitance=A*exp(B*lens actuator setting+C) where A, B and C are scalar values.

### Claim 5 (depends on 3)

A method according to claim 3 wherein said image capture device includes a camera module including a VCM actuated lens and wherein said modelled relationship is linear.

### Claim 6 (depends on 1)

A method according to claim 1 wherein step f) comprises recording said lens actuator settings at each POI between said device macro and infinity settings at said selected orientation.

### Claim 7 (depends on 1)

A method according to claim 1 wherein said selected orientation is horizontal and said plurality of distinct orientations include −90, −30, 30 and 90 degrees relative to horizontal.

### Claim 8 (depends on 1)

A method according to claim 1 wherein said lens actuator settings comprise DAC codes for positioning said lens at each POI.

### Claim 9 (depends on 8)

A method according to claim 8 wherein said image capture device includes a camera module including a MEMS actuated lens.

### Claim 10 (depends on 9)

A method according to claim 9 wherein step c) comprises:
iteratively sweeping through DAC codes for a sample device;
recording a lens actuator capacitance for each DAC code.

### Claim 11 (depends on 9)

A method according to claim 9 wherein step f) comprises:
recording a lens actuator capacitance at macro and infinity settings; and
recording a DAC code at said at least two POI.

### Claim 12 (depends on 1)

A method according to claim 1 wherein said image capture device includes a camera module including a VCM actuated lens.

### Claim 13 (depends on 1)

A method according to claim 1 wherein said step g) comprises recording said determined relationships and said recorded lens actuator settings in device memory.

### Claim 14 (depends on 1)

A method according to claim 1 wherein said step g) comprises combining said recorded lens actuator settings with said determined relationships to provide a table comprising lens actuator settings for each orientation and each POI and recording said table in device memory.

### Claim 15 (depends on 1)

A method according to claim 1 comprising repeating steps f) and g) for each of a number of operating temperatures.

### Claim 16 (depends on 15)

A method according to claim 15 wherein said operating temperatures correspond to a temperature sensor reading for one of: a camera lens or the image capture device.

### Claim 17 (depends on 1)

A method according to claim 1 wherein said calibrating said image capture device comprises storing device specific calibration information in one time programmable memory (OTP) within said image capture device.