Device and method for controlling brightness of image signal

• US 6,700,628 B1
• Filed: 05/08/2000
• Issued: 03/02/2004
• Est. Priority Date: 05/08/1999
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Kim, Sang Yeon
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): NATNAEL, PAULOS M
• Application Number:
  US09/567,103
• Time in Patent Office: 1,394 Days
• Field of Search: 348/687, 348/688, 348/672, 348/671, 348/678, 382/168, 382/169, 382/171, 382/172, 382/274, 382/254, 358/522, 358/455, 358/447
• US Class Current: 348/687
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response

Abstract

A device and method for controlling a brightness of an image signal in a moving picture transmission/reception system is disclosed. The present invention includes a control point detecting unit for receiving an image, calculating a Cumulative Density Function from two most significant bits of the image, dividing an axis into a required number of portions, and detecting a required number of control points. The present invention also includes an image signal brightness controlling unit for calculating and dividing six least significant bits of the image and a signal from the control point detecting unit for controlling a next frame of the image.

Claims

1. A device for controlling a brightness of an image comprising:

a control point detecting unit which receives an image and obtains a cumulative density function (CDF) of a frame of the image, divides an abscissa of the CDF into a required number of portions, and detects control points resulting from the division; and

an image signal brightness controlling unit which calculates a change in a brightness of a next frame of the image based upon the CDF and the control points,

wherein the change in the brightness of the next frame of the image is selectively adjusted based on latch values selected between default latch values and calculated latch values, and

wherein the image signal brightness controlling unit comprises;

a signal selection logic unit which performs a selection logic in response to a comparison signal from a comparing unit and forwards a selection logical signal;

a signal selector which selects at least one latch value signal in response to the selection logic signal;

a first multiplier which multiplies a plurality of LSBs (least significant bits) of the image with a first signal from the signal selector;

an operator which subtracts the plurality of LSBs of the image from a preset value;

a second multiplier which multiplies a second signal from the signal selector with a signal from the operator;

an adder which adds the signals from the first and second multipliers; and

a shifter which shifts a signal from the adder.

2. A device of claim 1, further comprising a frame buffer which stores an input frame while the control point detecting unit obtains the CDF and control points of the input frame;

and

wherein the image signal brightness controlling unit calculates a change in a brightness of the input frame from the frame buffer based upon the CDF and control points of the input frame.

3. A device of claim 1, wherein the control point detecting unit obtains a CDF and control points of an nth frame of the image;

and

the image signal brightness controlling unit calculates a change in a brightness of the nth frame of the image based upon a CDF and control points of an (n−

1)th frame of the image.

4. A device for controlling a brightness of an image signal comprising:

a control point detecting unit which obtains a cumulative density function (CDF) of a frame of an input image, divides the CDF into a required number of portions, and detects control points resulting from the division to output a plurality of comparison signals and to set latch values; and

an image signal brightness controlling unit which calculates a change in a brightness of the frame of the input image based upon the plurality of comparison signals from the control point detecting unit and based upon latch values set using a CDF of a previous frame of the input image,

wherein the latch values are selected between default latch values and calculated latch values, and

wherein the control point detecting unit comprises;

a comparing unit which compares a plurality of MSBs (most significant bits) of the input image to a plurality of preset values and thereby outputs the plurality of comparison signals;

a first counting unit which counts a number of pixels in the frame of the input image;

a second counting unit which counts each of the plurality of comparison signals from the comparing unit according to a clock signal;

a normalizing unit which selects each one of the count values from the second counting unit in response to a count control signal and multiplies a selected count value with a quotient from a maximum range of brightness divided by the number of pixels in the frame of the input image to output corresponding normalized count value;

a latching unit which latches a plurality of stored latch value signals; and

a latch value setting unit which sets a plurality of latch values based upon the normalized count values.

5. A device of claim 4, wherein the CDF is divided into four portions resulting in three control points, and wherein the comparing unit compares two MSBs of the input image to three preset values to output three comparison signals based upon the comparisons.

6. A device of claim 5, wherein the three control points are 64, 128, and 192, if the input image is in 8 bits.

7. A device of claim 4, wherein the latch value setting unit comprises:

a signal selector which selects one of the plurality of preset values in response to the count control signal;

a first adder which adds a selected preset value to a normalized count value from the normalizing unit;

a multiplier which multiplies a scaling signal with a first sum from the first adder; and

a second adder which adds the selected preset value to a signal from the multiplier and outputs a second sum as a latch value.

8. A device of claim 7, wherein the latch value setting unit further comprises a second signal selecting unit which selects one of either the latch value from the second adder or a preset latch value, in response to a user selecting signal, and which stores the selected latch value in the latching unit.

9. A device of claim 4, wherein the image signal brightness controlling unit comprises:

a signal selection logic unit which performs a selection logic in response to a comparison signal from the comparing unit and forwards a selection logical signal;

a signal selector which selects at least one latch value signal in response to the selection logic signal;

a first multiplier which multiplies a plurality of LSBs (least significant bits) of the image with a first signal from the signal selector;

an operator which subtracts the plurality of LSBs of the image from a preset value;

a second multiplier which multiplies a second signal from the signal selector with a signal from the operator;

an adder which adds the signals from the first and second multipliers; and

a shifter which shifts a signal from the adder.

10. A method of controlling a brightness of an image comprising:

(a) obtaining a cumulative density function (CDF) of a frame of the input image, dividing an abscissa of the CDF into a required number of portions, and detecting control points resulting from the division; and

(b) calculating a change in a brightness of a next frame of the image based upon the CDF and the control points,

wherein the change in the brightness of the next frame of the image is selectively adjusted based on latch values selected between default latch values and calculated latch values, and

wherein the (b) comprises;

(b1) performing a selection logic in response to a comparison signal from the (a) and forwarding a selection logic signal;

(b2) selecting at least one latch value signal in response to the selection logic signal;

(b3) multiplying a plurality of LSBs (least significant bits) of the input image with a first signal from the (b2);

(b4) subtracting the plurality of LSBs of the image from a preset value;

(b5) multiplying a second signal from the (b2) with a signal from the (b4);

(b6) adding the signals from the (b3) and the (b5); and

(b7) shifting a signal from the (b6).

11. A method of claim 10, further comprising storing an input frame while obtaining the CDF and control points of the input frame in the (a);

and

wherein the (b) includes calculating a change in a brightness of the stored input frame based upon the CDF and control points of the input frame.

12. A method of claim 10, wherein the (a) includes obtaining a CDF and control points of an (n−

1)th frame of the image, and calculating a change in a brightness of an nth frame of the image based upon the CDF and control points of the (n−

1)th frame of the image.

13. A method for controlling a brightness of an image signal comprising:

(a1) obtaining a cumulative density function (CDF) of a frame of an input image, dividing the CDF into a required number of portions, and detecting control points resulting from the division to output a plurality of comparison signals and to set latch values; and

(b1) calculating a change in a brightness of the frame of the input image based upon the plurality of comparison signals and based upon latch values set using a CDF of a previous frame of the input image,

wherein the latch values are selected between default latch values and calculated latch values, and

wherein the (a1) comprises;

(a2) comparing a plurality of MSBs (most significant bits) of the input image to a plurality of preset values and outputting the plurality of comparison signals;

(b2) counting a number of pixels in the frame of the input image;

(c2) counting each of the plurality of comparison signals from the

(b2) according to a clock signal;

(d2) normalizing the count values from the (c2) by selecting each one of the count values in response to a count control signal and multiplying a selected count value with a quotient from a maximum range of brightness divided by the number of pixels in the frame of the input image to output corresponding normalized count values;

(e2) setting a plurality of latch values based upon the normalized count values; and

(f2) latch a plurality of stored latch value signals.

14. A method of claim 13, wherein the (a1) includes dividing the CDF into four portions resulting in three control points, and the (a2) includes comparing two MSBs of the input image to three preset value points to output three comparison signals based upon the comparison.

15. A method of claim 14, wherein the three control points are 64, 128, and 192, if the input image is in 8 bits.

16. A method of claim 13, where the (e2) comprises:

(a3) selecting one of the plurality of preset values in response to the count control signal;

(b3) adding a selected preset value to a normalized count value from the (d2) and outputting a first sum;

(c3) multiplying a scaling signal with the first sum; and

(d3) adding the selected preset value to a product value from the (c3) and outputting a second sum as a latch value.

17. A method of claim 16, wherein the (e2) further comprises selecting one of either the latch value from the (d3) or a preset latch value, in response to a user selecting signal, and storing the selected latch value.

18. A device of claim 13, wherein the (b1) comprises:

(a2) performing a selection logic in response to a comparison signal from the (a1) and forwarding a selection logic signal;

(b2) selecting at least one latch value signal in response to the selection logic signal;

(c2) multiplying a plurality of LSBs (least significant bits) of the input image with a first signal from the (b2);

(d2) subtracting the plurality of LSBs of the image from a preset value;

(e2) multiplying a second signal from the (b2) with a signal from the (d2);

(f2) adding the signals from the (c2) and the (e2); and

(g2) shifting a signal from the (f2).