Image displaying method, image displaying device, and contrast adjusting circuit for use therewith

• US 20040036703A1
• Filed: 04/10/2003
• Published: 02/26/2004
• Est. Priority Date: 08/22/2002
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Aoki, Hiroshi, Hasegawa, Ryo
• Granted Patent: US 7,227,559 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

A system provides an image displaying technique that provides stable high contrast even in an area having high brightness. Based on information about an average brightness level of a digital luminance signal, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side, and increase processing which increases a contrast gain within a dynamic range, are performed for an analog luminance signal or a digital luminance signal, enabling improvement in contrast even where brightness is intense.

Claims

1. A method of converting an analog video signal into a digital video signal to display an image, the method comprising:

detecting information about an average brightness level of a digital luminance signal that has been subjected to analog-to-digital conversion;

determining the quantity of correction in response to the average brightness level; and

based on the quantity of correction, by which black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is performed for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, and in association with the brightness level decreased by black-correction processing, a contrast gain is increased within a dynamic range;

whereby contrast is adjusted before displaying an image.

2. An image displaying method according to claim 1, further comprising a step by which within a range of an average brightness level greater than or equal to a given value, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is performed for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, and in association with the brightness level decreased by the black-correction processing, a contrast gain is increased within a dynamic range, whereby contrast is adjusted before displaying an image.

3. An image displaying method according to claim 1, further comprising a step by which for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, a brightness level in black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is expected, and a contrast gain is increased in association therewith, whereby contrast is adjusted before displaying an image.

4. An image displaying method according to claim 1, further comprising a step by which for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is performed, and in association with the brightness level decreased by the black-correction processing, a contrast gain is increased within a dynamic range, and color correction is performed by changing a gain of an analog color signal before the A/D conversion or a gain of a digital color signal after the A/D conversion,

whereby contrast is adjusted before displaying an image.

5. An image displaying method according to claim 1, further comprising a step by which the step for changing the brightness level is controlled so that based on the quantity of correction, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is performed for the analog luminance signal or the digital luminance signal within a range of an average brightness level greater than or equal to the given value, and the step for changing the contrast gain is controlled so that in association with the black-correction level, a contrast gain is increased within a dynamic range, whereby contrast is adjusted before displaying an image.

6. An image displaying method according to claim 1, further comprising:

detecting an average brightness level and a maximum brightness level of the digital luminance signal which has been subjected to analog-to-digital conversion, the step being capable of identifying a brightness area corresponding to the average brightness level, and a brightness area corresponding to the maximum brightness level;

determining the predetermined quantity of correction in response to the average brightness level and the maximum brightness level; and

a step by which the step for changing the contrast gain within a range smaller than or equal to the maximum brightness level or within a range less than the maximum brightness level is controlled so that in association with the brightness level in black-correction processing a contrast gain is increased within a dynamic range,

whereby contrast is adjusted before displaying an image.

7. An image displaying device that converts an analog video signal into a digital video signal to display an image, the device comprising:

a circuit for detecting information about an average brightness level of a digital luminance signal, which has been subjected to analog-to-digital conversion, to determine the predetermined quantity of correction in response to the average brightness level;

a circuit in which based on the quantity of correction, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is performed for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, and in association with the brightness level decreased by the black-correction processing, a contrast gain is increased within a dynamic range;

a color matrix circuit that generates and outputs digital video signals of red, green, and blue on the basis of a digital color signal and digital luminance signal; and

a display unit for displaying an image by a digital video signal output from the color matrix circuit.

8. An image displaying device according to claim 7 further comprising a circuit for performing color correction by changing a gain of an analog color signal before the A/D conversion or a gain of a digital color signal after the A/D conversion based on information about the average brightness level.

9. An image displaying device according to claim 7, further comprising:

a circuit for detecting an average brightness level of the analog-to-digital converted digital luminance signal during a given period to identify a brightness area corresponding to the average brightness level.

10. An image displaying device according to claim 7, further comprising:

a circuit in which the circuit for changing the brightness level is controlled so that based on the quantity of correction, black-correction processing which decreases a brightness level by offsetting it to the minus side is performed for the analog luminance signal or the digital luminance signal within a range of an average brightness level greater than or equal to the given value, and the circuit for changing the contrast gain is controlled so that in association with the black-correction level, a contrast gain is increased within a dynamic range.

11. An image displaying device according to claim 7, further comprising:

a circuit for detecting an average brightness level and the maximum brightness level of the digital luminance signal which has been subjected to analog-to-digital conversion, the circuit being capable of identifying a brightness area corresponding to the average brightness level, and a brightness area corresponding to the maximum brightness level;

a circuit for determining the predetermined quantity of correction in response to the average brightness level and the maximum brightness level; and

a circuit in which the circuit for changing the contrast gain within a range smaller than or equal to the maximum brightness level or within a range less than the maximum brightness level is controlled so that in association with the brightness level in the black-correction processing, a contrast gain is increased within a dynamic range.

12. An image displaying device according to claim 7, further comprising:

a circuit in which for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, a brightness level in the black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is expected, and thereby a contrast gain is increased in association therewith.

13. A contrast-adjusting circuit used for an image displaying device that converts an analog video signal into a digital video signal to display an image, the circuit comprising:

means by which based on information about an average brightness level of an analog-to-digital converted digital luminance signal, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side according to the predetermined quantity of correction is performed for an analog luminance signal before the A/D conversion or a digital luminance signal after the A/D conversion, and processing which increases a contrast gain in association with the brightness level decreased by the black-correction processing is performed, thereby adjusting video contrast.

14. A contrast-adjusting circuit according to claim 13, further comprising:

a circuit for performing color correction by changing a gain of an analog color signal before the A/D conversion or a gain of a digital color signal after the A/D conversion on the basis of the information about the average brightness level.

15. A contrast-adjusting circuit according to claim 13, further comprising:

a circuit for detecting an average brightness level of the analog-to-digital converted digital luminance signal during a given period to identify a brightness area corresponding to the average brightness level.

16. A contrast-adjusting circuit according to claim 13 further comprising a circuit in which the circuit for changing the brightness level is controlled so that on the basis of the quantity of correction, black-correction processing which decreases a brightness level by offsetting the brightness level to the minus side is performed for the analog luminance signal or the digital luminance signal within a range of an average brightness level greater than or equal to the given value, and the circuit for changing the contrast gain is controlled so that in association with the black-correction level, a contrast gain is increased within a dynamic range.

17. A contrast-adjusting circuit according to claim 13, further comprising:

a circuit for detecting an average brightness level and the maximum brightness level of the digital luminance signal which has been subjected to analog-to-digital conversion, the circuit being capable of identifying a brightness area corresponding to the average brightness level, and a brightness area corresponding to the maximum brightness level;

a circuit for determining the predetermined quantity of correction in response to the average rightness level and the maximum brightness level; and

a circuit in which the circuit for changing the contrast gain within a range smaller than or equal to the maximum brightness level or within a range less than the maximum brightness level is controlled so that in association with the brightness level in the black-correction processing, a contrast gain is increased within a dynamic range.

18. A contrast-adjusting circuit according to claim 13 further comprising a circuit in which for an analog luminance signal before the A/D conversion or the digital luminance signal after the A/D conversion, a brightness level in the black-correction processing which decreases the brightness level by offsetting the brightness level to the minus side is expected, and thereby a contrast gain is increased in association therewith.