Methods and systems for generating and applying image tone scale adjustments

• US 7,982,707 B2
• Filed: 07/28/2006
• Issued: 07/19/2011
• Est. Priority Date: 12/02/2004
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kerofsky, Louis Joseph
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): Tryder; Gregory J
• Application Number:
  US11/460,907
• Publication Number:
  US 20060267923A1
• Time in Patent Office: 1,817 Days
• Field of Search: 345/102, 345/89, 345/207, 345/690, 345/589, 345/214
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

Embodiments of the present invention comprise systems and methods for generating and applying image tone scale adjustments.

Claims

1. A method for adjusting input image code values for display with a reduced source light power level, said method comprising:

a) determining a source light power level, P;

b) determining a display black level corresponding to said source light power level, B;

c) determining a maximum display output corresponding to said source light power level, W;

d) determining a display gamma value, γ

;

e) determining a maximum input code value, cvMax;

f) determining a minimum input code value, cvMin;

g) calculating a boost slope, α

;

h) calculating a boost intercept, β

;

i) calculating a least fidelity point, LFP;

j) calculating a maximum fidelity point, MFP;

k) defining a tone scale adjustment curve using a hardware device, wherein said tone scale adjustment curve comprises;

i) a first region defined by image code values between a minimum input image code value, ImageMinCV, and said LFP, wherein said tone scale adjustment curve in said first region comprises a first function relating image code values to display code values;

ii) a second region defined by image code values between said LFP and said MFP, wherein said tone scale adjustment curve in said second region comprises a second function relating image code values to display code values;

iii) a third region defined by image code values between said MFP and a maximum input image code value, ImageMaxCV, wherein said tone scale adjustment curve in said third region comprises a third function relating image code values to display code values;

l) receiving an input image comprising input image code values representing a, tangible object; and

m) applying said tone scale adjustment curve to said input image code values.

2. A method as described in claim 1 wherein said first function is a quadratic function.

3. A method as described in claim 1 wherein said first function is

A·

(x−

LFP)²+B·

(x−

LFP)+C,

wherein

4. A method as described in claim 1 wherein said second function is a linear function.

5. A method as described in claim 1 wherein said second function is

α

·

x+β

, wherein

6. A method as described in claim 1 wherein said third function is a quadratic function.

7. A method as described in claim 1 wherein said third function is

D·

(x−

MFP)²+E·

(x−

MFP)+F,

wherein

8. A method as described in claim 1 wherein said tone scale adjustment curve further comprises a lower region defined by image code values between cvMin and ImageMinCV, wherein said tone scale adjustment curve in said lower region assigns all image code values to the value of cvMin.

9. A method as described in claim 1 wherein said tone scale adjustment curve further comprises a higher region defined by image code values between cvMax and ImageMaxCV, wherein said tone scale adjustment curve in said higher region assigns all image code values to the value of cvMax.

10. A method as described in claim 1 wherein said calculating an MFP comprises:

a) calculating a candidate MFP value according to MFP=2·

cvMax·

(P)1/γ

−

ImageMaxCV; and

b) adjusting said candidate MFP according to MFP=2·

cvMax·

(P)1/γ

−

ImageMaxCV when said candidate MFP is less than 2·

cvMax·

(P)1/γ

−

ImageMaxCV.

11. A method as described in claim 1 wherein said calculating an LFP comprises:

a) calculating a candidate LFP value according to LFP=2·

cvMin·

(P)1/γ

−

ImageMinCV; and

b) adjusting said candidate LFP according to LFP=2·

cvMin·

(P)1/γ

−

ImageMinCV when said candidate LFP is greater than 2·

cvMin·

(P)1/γ

−

ImageMinCV.

19. A method as described in claim 12 A method as described in claim 1 wherein said second function is α

·

x+β

, wherein

12. A method for adjusting image code values for display with a reduced source light power level, said method comprising:

a) defining a least fidelity point, LFP;

b) defining a maximum fidelity point, MFP;

c) applying a tone scale adjustment curve to image code values representing picture of a tangible object, wherein said applying is performed using a hardware device, wherein said tone scale adjustment curve comprises;

i) a linear region defined by image code values between said LFP and said MFP, wherein said tone scale adjustment curve in said linear region comprises a linear function relating image code values to display code values;

ii) a lower transition region defined by image code values less than said LFP, wherein said tone scale adjustment curve in said lower transition region comprises a lower transition function relating image code values to display code values, wherein said lower transition function transitions from said linear function to a minimum code value point with a function that decreases in slope from said linear function to said minimum code value point; and

iii) an upper transition region defined by image code values greater than said MFP, wherein said tone scale adjustment curve in said upper transition region comprises an upper transition function relating image code values to display code values, wherein said upper transition function transitions from said linear function to a maximum code value point with a function that decreases in slope from said linear function to said maximum code value point.

13. A method as described in claim 12 wherein said lower transition function is a quadratic function.

14. A method as described in claim 12 wherein said upper transition function is a quadratic function.

15. A method as described in claim 12 wherein said lower transition function meets said linear function at a substantially similar slope and meets said minimum code value point at a near-zero slope.

16. A method as described in claim 12 wherein said upper transition function meets said linear function at a substantially similar slope and meets said maximum code value point at a near-zero slope.

17. A method as described in claim 12 wherein said calculating an MFP comprises:

a) calculating a candidate MFP value according to MFP=2·

cvMax·

(P)1/γ

−

ImageMaxCV; and

b) adjusting said candidate MFP according to MFP=2·

cvMax·

(P)1/γ

−

ImageMaxCV when said candidate MFP is less than 2·

cvMax·

(P)1/γ

−

ImageMaxCV

c) wherein said P is a source light power level, said cvMax is maximum display code value, said ImageMaxCV is an image maximum code value and said γ

is a display characteristic value.

18. A method as described in claim 12 wherein said calculating an LFP comprises:

a) calculating a candidate LFP value according to LFP=2·

cvMin·

(P)1/γ

−

ImageMinCV; and

b) adjusting said candidate LFP according to LFP=2·

cvMin·

(P)1/γ

−

ImageMinCV when said candidate LFP is greater than 2·

cvMin·

(P)1/γ

−

ImageMinCV;

c) wherein said P is a source light power level, said cvMin is minimum display code value, said ImageMinCV is an image minimum code value and said γ

is a display characteristic value.

20. A system for adjusting image code values for display with a reduced source light power level, said system comprising:

a) an LFP processor for determining a least fidelity point, LFP;

b) an MFP processor for determining a maximum fidelity point, MFP;

c) an adjustment processor, comprising a hardware processor and memory, for applying a tone scale adjustment curve to image code values representing picture of a tangible object, wherein said tone scale adjustment curve comprises;

i) a linear region defined by image code values between said LFP and said MFP, wherein said tone scale adjustment curve in said linear region comprises a linear function relating image code values to display code values;

ii) a lower transition region defined by image code values less than said LFP, wherein said tone scale adjustment curve in said lower transition region comprises a transition function relating image code values to display code values, wherein said transition function transitions from said linear function to a minimum code value point with a function that decreases in slope from said linear function to said minimum code value point; and

iii) an upper transition region defined by image code values greater than said MFP, wherein said tone scale adjustment curve in said upper transition region comprises a transition function relating image code values to display code values, wherein said transition function transitions from said linear function to a maximum code value point with a function that decreases in slope from said linear function to said maximum code value point.