# US 8,542,313 B2 · Depth from defocus calibration

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- Number: US 8,542,313 B2
- Document ID: US8542313B2
- Status: Granted
- Kind: B2
- Application number: 12/857,343
- Filed: 2010-08-16
- Published: 2011-07-28
- Granted: 2013-09-24
- Earliest claimed: 2010-01-27
- Assignees: CSR Technology Inc.
- Applicants: Guy Rapaport; Meir Tzur; Artemy Baxansky
- Inventors: Guy Rapaport; Meir Tzur; Artemy Baxansky
- Web page: https://patentgrep.com/patent/US8542313B2

## CPC

- H04N 23/959: by adjusting depth of field during image capture, e.g. maximising or setting range based on scene characteristics
- H04N 23/676: {Bracketing for image capture at varying focusing conditions}
- H04N 23/743: Bracketing, i.e. taking a series of images with varying exposure conditions
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A device and methods are provided for calculating depth estimation for a digital imaging device are disclosed and claimed. In one embodiment, a method includes detecting a first image associated with a first focus parameter, detecting a second image associated with a second focus parameter, calculating a statistical representation of a region of interest in the first and second images, and determining a ratio for the region of interest based on the statistical representation. The method may further include determining one or more focus characteristics using a memory table based on the determined ratio for the region of interest, and calculating a focus depth for capture of image data based on the determined one or more focus characteristics associated with the memory table.

## Claims

### Claim 1

A method for calculating depth estimation for a digital imaging device, the method comprising the acts of:
detecting a first image, by the digital imaging device, associated with a first focus parameter;
detecting a second image, by the digital imaging device, associated with a second focus parameter;
calculating a statistical representation of a region of interest in the first and second images, wherein the statistical representation is based at least on convoluting at least one filter with the image data for the first and second images;
determining a ratio for the region of interest based on the statistical representation;
determining one or more focus characteristics using a memory table based on the determined ratio for the region of interest; and
calculating a focus depth, by the digital imaging device, for capture of image data based on the determined one or more focus characteristics associated with the memory table.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first and second images are associated with different focus positions and are detected to determine one or more automatic focus parameters for the imaging device.

### Claim 3 (depends on 1)

The method of claim 1, wherein the statistical representation for the region of interest indicates a relation between object depth and a blur ratio for the regions of interest.

### Claim 4 (depends on 1)

The method of claim 1, wherein the ratio relates to one or more of a blur ratio and a generalized ratio for a region of interest.

### Claim 5 (depends on 1)

The method of claim 1, wherein the memory table relates to a predetermined look-up-table (LUT) for a plurality of focus positions in a scene.

### Claim 6 (depends on 1)

The method of claim 1, wherein focus depth relates to a depth estimation providing a focus depth for focusing the imaging device to capture a scene, and wherein the memory table represents object distance as a function of the ratio.

### Claim 7 (depends on 1)

The method of claim 1, wherein a plurality of focus depths are determined for capturing image data for the scene.

### Claim 8 (depends on 7)

The method of claim 7, further comprising determining a confidence level for each focus depth, and selecting a focus depth for automatic focus of the imaging device.

### Claim 9 (depends on 8)

The method of claim 8, further comprising calculating calibration values for a confidence table based on the confidence levels and an estimated depth probability distribution for the confidence levels.

### Claim 10 (depends on 1)

The method of claim 1, further comprising calculating calibration values for the memory table based on the focus parameters and a generalized ratio probability distribution for the focus parameters.

### Claim 11 (depends on 1)

The method of claim 1, further comprising determining an alignment parameter for the first image relative to the second image, wherein the alignment parameter relates to an alignment transformation applied to image data associated with the region of interest.

### Claim 12 (depends on 1)

The method of claim 1, further comprising adjusting an image sensor based on the calculated focus depth for capture of image data.

### Claim 13

A device configured to estimate focus depth for a scene, the device comprising:
an image sensor configured to capture image data of the scene; and
a processor coupled to the image sensor, the processor configured to receive a first image from the image sensor associated with a first focus parameter;
receive a second image the image sensor associated with a second focus parameter;
calculate a statistical representation of a region of interest in the first and second images, wherein the statistical representation is based at least on convoluting at least one filter with the image data for the first and second images;
determine a ratio for the region of interest based on the statistical representation;
determine one or more focus characteristics using a memory table based on the determined ratio for the region of interest; and
calculate a focus depth for capture of image data based on the determined one or more focus characteristics associated with the memory table.

### Claim 14 (depends on 13)

The device of claim 13, wherein the first and second images are associated with different focus positions and are detected to determine one or more automatic focus parameters for the imaging device.

### Claim 15 (depends on 13)

The device of claim 13, Wherein the statistical representation for the region of interest indicates a relation between object depth and a blur ratio for the regions of interest.

### Claim 16 (depends on 13)

The device of claim 13, wherein the ratio relates to one or more of a blur ratio and a generalized ratio for a region of interest.

### Claim 17 (depends on 13)

The device of claim 13, wherein the memory table relates to a predetermined look-up-table (LUT) for a plurality of focus positions in a scene.

### Claim 18 (depends on 13)

The device of claim 13, wherein focus depth relates to a depth estimation providing a focus depth for focusing the imaging device to capture a scene, and wherein the memory table represents object distance as a function of the ratio.

### Claim 19 (depends on 13)

The device of claim 13, wherein a plurality of focus depths are determined for capturing image data for the scene.

### Claim 20 (depends on 19)

The device of claim 19, wherein the processor is configured to determine a confidence level for each focus depth, and select a focus depth for automatic focus of the imaging device.

### Claim 21 (depends on 20)

The device of claim 20, wherein the processor is configured to calculate calibration values for a confidence table based on the confidence levels and an estimated depth probability distribution for the confidence levels.

### Claim 22 (depends on 13)

The device of claim 13, wherein the processor is configured to calculate calibration values for the memory table based on the focus parameters and a generalized ratio probability distribution for the focus parameters.

### Claim 23 (depends on 13)

The device of claim 13, wherein the processor is further configured to determine an alignment parameter for the first image relative to the second image, wherein the alignment parameter relates to an alignment transformation applied to image data associated with the region of interest.

### Claim 24 (depends on 13)

The device of claim 13, wherein the processor is configured to adjust the image sensor based on the calculated focus depth for capture of image data.