Digital imaging device with enhanced dynamic range and operating method thereof

1. A digital imaging device, comprising:

a sensor array comprising a plurality of black pixels and a plurality of normal pixels, wherein the black pixels are configured to output black pixel data and the normal pixels are configured to output normal pixel data;

a sample hold circuit configured to temporarily hold the black pixel data and the normal pixel data;

an amplifier configured to amplify the black pixel data and the normal pixel data with a gain;

a subtractor configured to subtract a calibration value from the amplified black pixel data and the amplified normal pixel data, and output amplified and calibrated black pixel data and amplified and calibrated normal pixel data;

an analog to digital converter configured to convert the amplified and calibrated black pixel data and the amplified and calibrated normal pixel data to digital black pixel data and digital normal pixel data; and

a digital back end configured to

calculate a data offset according to the digital black pixel data,

determine a dynamic adjustment scale and amplify the digital normal pixel data with the dynamic adjustment scale,

calculate the calibration value according to the gain, the data offset and the dynamic adjustment scale, and

adjust the gain according to the dynamic adjustment scale.

2. The digital imaging device as claimed in claim 1 , wherein the digital back end is configured to

calculate a maximum calibration value and a minimum calibration value according to the gain, the data offset and the dynamic adjustment scale, and

calculate an average value of the maximum calibration value and the minimum calibration value to be configured as the calibration value.

3. The digital imaging device as claimed in claim 1 , wherein the digital back end is configured to calculate a difference value between an average value of the digital black pixel data and a reference value to be configured as the data offset.

4. The digital imaging device as claimed in claim 1 , wherein the digital back end is configured to compare the gain and the data offset with a look-up table to determine the dynamic adjustment scale.

5. The digital imaging device as claimed in claim 1 , wherein the digital back end is configured to

calculate a maximum calibration value and a minimum calibration value according to the gain, the data offset and the dynamic adjustment scale,

increase the dynamic adjustment scale and recalculate a new maximum calibration value and a new minimum calibration value when the maximum calibration value is larger than the minimum calibration value, and

continuously increase the dynamic adjustment scale until the new maximum calibration value is smaller than or equal to the new minimum calibration value.

6. The digital imaging device as claimed in claim 1 , wherein the amplifier comprises a single stage amplification unit, and the subtractor is coupled to an output terminal of the single stage amplification unit.

7. The digital imaging device as claimed in claim 1 , wherein the amplifier comprises multistage amplification units, and the subtractor is coupled between the amplification units or coupled to an output terminal of a final stage amplification unit among the amplification units.

8. The digital imaging device as claimed in claim 1 , wherein the dynamic adjustment scale is between 1.5-1.9.

9. An operating method of a digital imaging device, the digital imaging device comprising a sensor array, an analog front end and a digital back end, wherein the sensor array is for outputting black pixel data and normal pixel data, the analog front end is for amplifying and calibrating the black pixel data and the normal pixel data, and the digital back end is for processing digital pixel data, the operating method comprising:

amplifying the black pixel data and the normal pixel data with a gain;

calibrating data ranges of the amplified black pixel data and the amplified normal pixel data with a calibration value;

digitizing the amplified and calibrated black pixel data and digitizing the amplified and calibrated normal pixel data to respectively generate digital black pixel data and digital normal pixel data;

calculating a data offset according to the digital black pixel data;

determining a dynamic adjustment scale for amplifying the digital normal pixel data;

calculating the calibration value according to the gain, the data offset and the dynamic adjustment scale; and

adjusting the gain according to the dynamic adjustment scale.

10. The operating method as claimed in claim 9 , wherein the calculating the calibration value comprises:

calculating a maximum calibration value and a minimum calibration value according to the gain, the data offset and the dynamic adjustment scale; and

calculating an average value of the maximum calibration value and the minimum calibration value as the calibration value.

11. The operating method as claimed in claim 9 , wherein the determining comprises:

comparing the gain and the data offset with a look-up table to determine the dynamic adjustment scale.

12. The operating method as claimed in claim 9 , wherein the determining comprises:

calculating a maximum calibration value and a minimum calibration value according to the gain, the data offset and the dynamic adjustment scale;

increasing the dynamic adjustment scale and recalculating a new maximum calibration value and a new minimum calibration value when the maximum calibration value is larger than the minimum calibration value; and

continuously increasing the dynamic adjustment scale until the new maximum calibration value is smaller than or equal to the new minimum calibration value.

13. The operating method as claimed in claim 9 , wherein the adjusting comprises:

multiplying the gain by a multiple, wherein the multiple is a quotient of the dynamic adjustment scale divided by the gain.

14. The operating method as claimed in claim 9 , wherein the calculating the data offset comprises:

calculating a difference value between an average value of the digital black pixel data and a reference value as the data offset.

15. A digital imaging device comprising:

a sensor array comprising a plurality of black pixels and a plurality of normal pixels, wherein the black pixels are configured to output black pixel data and the normal pixels are configured to output normal pixel data;

an analog front end configured to

amplify the black pixel data and the normal pixel data with a gain, and

calibrate data ranges of the amplified black pixel data and the amplified normal pixel data with a calibration value; and

a digital back end configured to

digitize the amplified and calibrated black pixel data,

calculate a data offset according to digital black pixel data,

determine a dynamic adjustment scale,

calculate a maximum calibration value and a minimum calibration value according to the gain, the data offset and the dynamic adjustment scale,

calculate an average value of the maximum calibration value and the minimum calibration value to be configured as the calibration value, and

adjust the gain according to the dynamic adjustment scale.

16. The digital imaging device as claimed in claim 15 , wherein

the amplified and calibrated black pixel data is digitized based on a dynamic range,

the maximum calibration value is obtained by subtracting a product of the gain and the data offset from a half of the dynamic range, and

the minimum calibration value is obtained by subtracting the half of the dynamic range from a summation of a product of the half of the dynamic range and the dynamic adjustment scale and a product of the gain and the data offset.

17. The digital imaging device as claimed in claim 15 , wherein the digital back end is configured to determine the dynamic adjustment scale according to an iteration algorithm.

18. The digital imaging device as claimed in claim 15 , wherein the digital back end is configured to determine the dynamic adjustment scale according to a look-up table, and the look-up table is configured to pre-store a relationship of a plurality of data offset and a plurality of gains with respect to a plurality of dynamic adjustment scales.

19. The digital imaging device as claimed in claim 15 , wherein the digital back end is configured to multiply the gain by a multiple to adjust the gain, and the multiple is a quotient of the dynamic adjustment scale divided by the gain.

20. The digital imaging device as claimed in claim 15 , wherein the digital back end is configured to calculate a difference value between an average value of the digital black pixel data and a reference value to be configured as the data offset.