# US 7,612,831 B2 · Gamma correction device, image conversion apparatus using the same, and display device

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- Number: US 7,612,831 B2
- Document ID: US7612831B2
- Status: Granted
- Kind: B2
- Application number: 11/378,478
- Filed: 2006-03-20
- Published: 2006-09-28
- Granted: 2009-11-03
- Earliest claimed: 2005-03-25
- Assignees: NEC Corporation
- Inventors: Daigo Miyasaka
- Web page: https://patentgrep.com/patent/US7612831B2

## CPC

- H04N 5/202: Gamma control (circuits for controlling camera response irrespective of the scene brightness H04N23/82)
- H04N 9/69: for modifying the colour signals by gamma correction (controlling camera response for colour signals H04N23/83)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

There are provided a gamma correction device enabling correct gamma correction while reducing the capacity of a lookup table, an image conversion apparatus and a display device using the same. A gamma correction device for outputting, as an m-bit signal, a digital input signal having been inputted as an n-bit signal, m being a given number, the gamma correction device including a high-order LUT, a low-order LUT, a difference LUT, a data connecting section 2, and an adder 3, wherein each of the lookup tables has input bits fewer than n and output bits fewer than m, the high-order LUT has x-bit input and m1-bit output, the low-order LUT has (n−t)-bit input and m2-bit output, the difference LUT has (n−t)-bit input and k-bit output, m≦m1+m2, x<n−t and m≧m1+k are established, the data connecting section 2 outputs connection data obtained by connecting output bits of the high-order LUT on the high-order bit side and output bits of the difference LUT on the low-order bit side with m−m1−k bits of “0” being interposed between the output bits, and the adder 3 adds the connection data and the output value of the low-order LUT and outputs the added data.

## Claims

### Claim 1

A gamma correction device for outputting, as an m-bit signal, a digital input signal having been inputted as an n-bit signal, m being a given number,
the gamma correction device comprising a first lookup table, a second lookup table, a third lookup table, a connector and an adder,
wherein each of the lookup tables has input bits fewer than n and output bits fewer than m,
the first lookup table has x-bit input and m1-bit output, the second lookup table has (n−t)-bit input and m2-bit output, the third lookup table has (n−t)-bit input and k-bit output,
m≦m1+m2, x<n−t and m≧m1+k are established,
the connector outputs connection data obtained by connecting output bits of the first lookup table on a high-order bit side and output bits of the third lookup table on a low-order bit side with m−m1−k bits of “0s” being interposed between the output bits, and
the adder adds the connection data and an output value of the second lookup table and outputs the added data.

### Claim 2 (depends on 1)

The gamma correction device according to claim 1, wherein the device comprises the plurality of third lookup tables.

### Claim 3 (depends on 2)

The gamma correction device according to claim 2, wherein the third lookup table has k output bits and k is determined based on a correction value γ of gamma correction.

### Claim 4 (depends on 2)

The gamma correction device according to claim 2, wherein the third lookup table has k output bits and k is set based on a maximum difference between adjacent gray scales in brightness/contrast correction.

### Claim 5 (depends on 2)

A floating-point gamma correction device for outputting an m-bit input signal made up of an exponent and a significand,
the device comprising as integer gamma correction units the plurality of gamma correction devices according to claim 2,
wherein the integer gamma correction unit has, as input, high-order n bits of the exponent, and
gamma correction with n-bit input and m-bit output is performed by selecting one of outputs of the integer gamma correction units based on a value of the significand, the selected output being determined based on a value of the exponent.

### Claim 6 (depends on 2)

An image conversion apparatus, comprising the gamma correction device according to claim 2.

### Claim 7 (depends on 2)

A display device, comprising the gamma correction device according to claim 2.

### Claim 8 (depends on 1)

The gamma correction device according to claim 1, wherein when a relationship between n-bit input and m-bit output is set in gamma correction as a base input/output table,
an input/output table in the first lookup table sets, as an output value (as a reference value signal) for x-bit input value of IN1, high-order m1 bits of an output value corresponding to an input value having high-order x bits of IN1 and low-order n−x bits of 0 on the base input/output table,
an input/output table in the second lookup table sets, as an output value for an (n−t) bit input value of IN2, a difference between an output value corresponding to an input value having high-order n−t bits of IN2 and low-order t bits of 0 on the base input/output table and a value obtained by adding an output value corresponding to an input value having high-order x bits of IN2 and low-order bits of m−m1 “0s” on the first lookup table, and
an input/output table in the third lookup table sets, as an output value for an (n−t)-bit input value of IN3, a difference between an output value corresponding to an input value having high-order (n−t) bits of IN3 and low-order t bits other than 0 on the base input/input output table and an output value corresponding to an input value having high-order n−t bits of IN3 and low-order t bits of 0 on the base input/output table.

### Claim 9 (depends on 8)

The gamma correction device according to claim 8, wherein the third lookup table has k output bits and k is determined based on a correction value γ of gamma correction.

### Claim 10 (depends on 8)

The gamma correction device according to claim 8, wherein the third lookup table has k output bits and k is set based on a maximum difference between adjacent gray scales in brightness/contrast correction.

### Claim 11 (depends on 8)

A floating-point gamma correction device for outputting an m-bit input signal made up of an exponent and a significand,
the device comprising as integer gamma correction units the plurality of gamma correction devices according to claim 8,
wherein the integer gamma correction unit has, as input, high-order n bits of the exponent, and
gamma correction with n-bit input and m-bit output is performed by selecting one of outputs of the integer gamma correction units based on a value of the significand, the selected output being determined based on a value of the exponent.

### Claim 12 (depends on 8)

An image conversion apparatus, comprising the gamma correction device according to claim 8.

### Claim 13 (depends on 8)

A display device, comprising the gamma correction device according to claim 8.

### Claim 14 (depends on 1)

The gamma correction device according to claim 1, wherein the third lookup table has k output bits and k is determined based on a correction value γ of gamma correction.

### Claim 15 (depends on 14)

A floating-point gamma correction device for outputting an m-bit input signal made up of an exponent and a significand,
the device comprising as integer gamma correction units the plurality of gamma correction devices according to claim 14,
wherein the integer gamma correction unit has, as input, high-order n bits of the exponent, and
gamma correction with n-bit input and m-bit output is performed by selecting one of outputs of the integer gamma correction units based on a value of the significand, the selected output being determined based on a value of the exponent.

### Claim 16 (depends on 14)

An image conversion apparatus, comprising the gamma correction device according to claim 14.

### Claim 17 (depends on 14)

A display device, comprising the gamma correction device according to claim 14.

### Claim 18 (depends on 1)

The gamma correction device according to claim 1, wherein the third lookup table has k output bits and k is set based on a maximum difference between adjacent gray scales in brightness/contrast correction.

### Claim 19 (depends on 18)

A floating-point gamma correction device for outputting an m-bit input signal made up of an exponent and a significand,
the device comprising as integer gamma correction units the plurality of gamma correction devices according to claim 18,
wherein the integer gamma correction unit has, as input, high-order n bits of the exponent, and
gamma correction with n-bit input and m-bit output is performed by selecting one of outputs of the integer gamma correction units based on a value of the significand, the selected output being determined based on a value of the exponent.

### Claim 20 (depends on 18)

An image conversion apparatus, comprising the gamma correction device according to claim 18.

### Claim 21 (depends on 18)

A display device, comprising the gamma correction device according to claim 18.

### Claim 22 (depends on 1)

A floating-point gamma correction device for outputting an m-bit input signal made up of an exponent and a significand,
the device comprising as integer gamma correction units the plurality of gamma correction devices according to claim 1,
wherein the integer gamma correction unit has, as input, high-order n bits of the exponent, and
gamma correction with n-bit input and m-bit output is performed by selecting one of outputs of the integer gamma correction units based on a value of the significand, the selected output being determined based on a value of the exponent.

### Claim 23 (depends on 22)

An image conversion apparatus, comprising the floating-point gamma correction device according to claim 22.

### Claim 24 (depends on 22)

A display device, comprising the floating-point gamma correction device according to claim 22.

### Claim 25 (depends on 1)

An image conversion apparatus, comprising the gamma correction device according to claim 1.

### Claim 26 (depends on 1)

A display device, comprising the gamma correction device according to claim 1.