Portable electronic device with auto-exposure control adaptive to environment brightness and image capturing method using the same

• US 8,982,237 B2
• Filed: 12/09/2011
• Issued: 03/17/2015
• Est. Priority Date: 12/09/2011
• Status: Active Grant

• Current Assignee: HTC Corporation
• Original Assignee: HTC Corporation
• Inventors: Chen, Wan-Yi
• Primary Examiner(s): Henn, Timothy J
• Assistant Examiner(s): PHAM, QUAN L
• Application Number:
  US13/316,120
• Publication Number:
  US 20130147986A1
• Time in Patent Office: 1,194 Days
• Field of Search: 348/222.1, 348/229.1, 348362-368
• US Class Current: 348/229.1
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/05 Combinations of cameras with electronic flash units
• CPC Class Codes: G03B 29/00 Combinations of cameras, projectors or photographic printing apparatus with non-photographic non-optical apparatus, e.g. clocks or weapons; Cameras having the shape of other objects combinations with flash apparatus G03B15/03
• CPC Class Codes: G03B 7/08 Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
• CPC Class Codes: G03B 7/097 for control of both exposure time and aperture
• CPC Class Codes: G03B 7/14 setting of both shutter and diaphragm aperture being effected so as to give the optimum compromise between depth of field and shortness of exposure
• CPC Class Codes: G03B 7/17 Selection of modes in flash units by exposure control arrangements
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 23/76 by influencing the image signals

Abstract

A portable electronic device with camera function and an image capture method with auto exposure control. The disclosed method comprises the following steps: obtaining a pre-view frame from a camera module; dividing the pre-view frame into a plurality of blocks and calculating representative brightness values of the blocks; assigning weight values to the blocks according to the representative brightness values; obtaining a weighted brightness value by performing a weighted operation on the representative brightness values based on the weight values of the blocks; setting an auto exposure parameter of the camera module based on the weighted brightness value; and controlling the camera module for capturing images based on the auto exposure parameter.

Claims

1. A portable electronic device with camera function,comprising:

a camera module; and

a processor for executing software, the software comprising;

a pre-view unit, configured to obtain a pre-view frame from the camera module;

an auto exposure control unit, comprising;

a block brightness calculation module, configured to divide the pre-view frame into a plurality of blocks and calculate representative brightness values of the plurality of blocks, wherein a representative brightness value of a block is represented by an average of luminance values of all pixels of the block;

a brightness weight assignment module, configured to assign weight values to the plurality of blocks according to the representative brightness values, the weight values comprising a first weight value, a second weight value and a third weight value, the first weight value being larger than the second weight value, and the second weight value being larger than the third weight value, so as to emphasize the blocks of higher representative brightness values;

a weighted brightness calculation module, configured to obtain a weighted brightness value by performing a weighted calculation on the representative brightness values of the blocks according to the weight values of the blocks; and

an exposure parameter setting module, configured to set at least one auto exposure parameter of the camera module based on the weighted brightness value; and

an image capture unit, configured to control the camera module for capturing images based on the at least one auto exposure parameter, wherein the brightness weight assignment module is configured to;

set a plurality of brightness threshold values according to a statistical analysis on the representative brightness values of the blocks, and set a plurality of weight values according to the brightness threshold values;

compare the representative brightness values of the plurality of blocks with the brightness threshold values and assign corresponding weight values to the plurality of blocks.

2. The portable electronic device with camera function as claimed in claim 1, further comprising:

a flash module; and

the software further comprising;

a flash actuation unit,

wherein the flash actuation unit actuates the flash module to perform a pre-flash operation for the camera module to obtain the pre-view frame, and actuates the flash module to perform a normal flash operation for the camera module to capture images, and the pre-flash operation generates a lower intensity flash than the normal flash operation.

3. The portable electronic device with camera function as claimed in claim 2, wherein the exposure parameter setting module further sets the at least one auto exposure parameter of the camera module based on a driving current ratio between the pre-flash operation and normal flash operation.

4. The portable electronic device with camera function as claimed in claim 1, wherein the at least one auto exposure parameter comprises analog gain or/and exposure time.

5. The portable electronic device with camera function as claimed in claim 1, wherein the brightness weight assignment module is further configured to:

calculate block numbers with respect to different representative brightness values; and

set the plurality of brightness threshold values according to the calculation result about the block numbers with respect to the different representative brightness values.

6. An image capture method with auto exposure control, comprising:

obtaining a pre-view frame from a camera module;

dividing the pre-view frame into a plurality of blocks and calculating representative brightness values of the blocks, wherein a representative brightness value of a block is represented by an average of luminance values of all pixels of the block;

assigning weight values to the blocks according to the representative brightness values, the weight values comprising a first weight value, a second weight value and a third weight value, the first weight value being larger than the second weight value, and the second weight value being larger than the third weight value, so as to emphasize the blocks of higher representative brightness values;

obtaining a weighted brightness value by performing a weighted calculation on the representative brightness values based on the weight values of the blocks;

setting at least one auto exposure parameter of the camera module based on the weighted brightness value; and

controlling the camera module to capture images according to the at least one auto exposure parameter,

wherein the step of assigning weight values to the blocks according to the representative brightness values comprises;

setting a plurality of brightness threshold values according to a statistical analysis result of the representative brightness values of the blocks and setting a plurality of weight values according the brightness threshold values; and

comparing the representative brightness values of the blocks with the brightness threshold values and assigning corresponding weight values to the blocks according to the comparison result.

7. The image capture method with auto exposure control as claimed in claim 6, further comprising:

performing a pre-flash operation by a flash module for obtaining the pre-view frame from the camera module; and

performing a normal flash operation for capturing images by the camera module, wherein intensity of flash is larger in the normal flash operation than in the pre-flash operation.

8. The image capture method with auto exposure control as claimed in claim 7, further comprising:

setting the at least one auto exposure parameter of the camera module according to a ratio of driving current between the normal flash operation and the pre-flash operation.

9. The image capture method with auto exposure control as claimed in claim 6, wherein the at least one auto exposure parameter comprises analog gain or/and exposure time.

10. The image capture method with auto exposure control as claimed in claim 6, wherein the step of assigning weight values to the blocks according to the representative brightness values further comprises:

performing a statistical analysis on the representative brightness values of the blocks to calculate block numbers with respect to different representative brightness values; and

setting the plurality of brightness threshold values according to the statistical analysis result and setting a plurality of weight values according the brightness threshold values.

11. An image capture method with auto exposure control, comprising:

obtaining a pre-view frame from a camera module, wherein the pre-view frame contains a plurality of blocks;

analyzing the pre-view frame and thereby assigning a plurality of weight values according to representative brightness values of the blocks and setting at least one auto exposure parameter of the camera module according to the representative brightness values and the weight values, wherein a representative brightness value of a block is represented by an average of luminance values of all pixels of the block, the weight values comprises a first weight value, a second weight value and a third weight value, the first weight value is larger than the second weight value, and the second weight value is larger than the third weight value, so as to emphasize the blocks of higher representative brightness values; and

controlling the camera module for capturing images based on the at least one auto exposure control parameter,

wherein the blocks with higher representative brightness values are assigned with higher weight values, and

wherein the step of assigning weight values to the blocks according to the representative brightness values comprises;

setting a plurality of brightness threshold values according to a statistical analysis result of the representative brightness values of the blocks and setting a plurality of weight values according the brightness threshold values; and

comparing the representative brightness values of the blocks with the brightness threshold values and assigning corresponding weight values to the blocks according to the comparison result.

12. The image capture method with auto exposure control as claimed in claim 11, further comprising:

performing a pre-flash operation by a flash module for obtaining the pre-view frame; and

performing a normal flash operation by the flash module for capturing images;

wherein intensity of flash is higher in the normal flash operation than in pre-flash operation.

13. The image capture method with auto exposure control as claimed in claim 12, further comprising:

setting the at least one auto exposure parameter according to a driving current ratio between the normal flash operation and the pre-flash operation.

14. The image capture method with auto exposure control as claimed in claim 11, wherein the at least one auto exposure parameter comprises an analog gain or/and exposure time.