Image memory device and method of operating same

• US 5,589,889 A
• Filed: 04/29/1994
• Issued: 12/31/1996
• Est. Priority Date: 04/16/1991
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Kawaoka, Yoshiki
• Primary Examiner(s): Harvey, David E.
• Application Number:
  US08/235,221
• Time in Patent Office: 977 Days
• Field of Search: 358/164, 358/32, 348/671, 348/672, 348/674, 348/675, 348/254
• US Class Current: 348/674
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82

Abstract

An image memory device is so adapted as to make it possible to use an image pick-up device having any characteristic and a display unit having any characteristic. The image memory device includes an input look-up table and an output look-up table. Data for performing a reverse gamma-correction is set in the input look-up table in advance in dependence upon the image pick-up device used. By virtue of the reverse gamma-correction, the image data is provided with linear characteristics. The reverse gamma-corrected data is stored in the memory. Data for performing a gamma correction is set in the output look-up table in advance in dependence upon the display unit used.

Claims

1. An image memory device comprising:

A/D converting means for converting an analog video signal from a video camera, into digital video image data;

input reverse-gamma correcting means having a rewritable input look-up table with data stored therein for applying a reverse gamma-correction to the digital video image data, which is provided by said A/D converting means, in order to convert, into linear characteristics, non-linear incident-light luminance vs. output-signal characteristics of said video camera, a reverse gamma correction being applied to the digital video image data using the data of said input look-up table with said reverse gamma correction being bound to the characteristics of said video camera;

memory means for storing the digital video image data corrected by said input reverse-gamma correcting means to always possess linearity;

output gamma correcting means having a rewritable output look-up table with data stored therein for applying a gamma correction to the digital video image data, which is read out of said memory means, in order to make the linear characteristics conform to non-linear input signal vs. output-light luminance characteristics of a display device, the gamma correction being applied to the digital video image data, which is read out of said memory means, using the data of said output look-up table with said gamma correction being related only to the characteristics of said display device; and

D/A converting means for converting the digital video image data, which has been corrected by said output gamma correcting means, into an analog video signal in order to be applied to said display device.

2. The device according to claim 1, further comprising processing means for creating reverse gamma-correction data, which is to be set in said input look-up table, in dependence upon said video camera used, and gamma-correction data, which is to be set in said output look-up table, in dependence upon the display device used.

3. A method of operating an image memory device comprising the steps of:

creating, in dependence upon a video camera used, and storing beforehand in an input look-up table, reverse gamma-correction data for converting, into linear characteristics, non-linear incident-light luminance vs. output-signal characteristics of said video camera with said reverse gamma correction data being bound to the characteristics of said video camera;

creating, in dependence upon a display device used, and storing beforehand in an output look-up table, gamma-correction data for making the linear characteristics conform to non-linear input signal vs. output-light luminance characteristics of said display device with the characteristics of said gamma-correction data being related only to the characteristics of said display device;

converting an analog video signal from said video camera, into digital video image data;

applying a reverse gamma-correction to the digital video image data using the created reverse gamma-correction data of said input look-up table; and

storing the corrected digital video image data, which always possesses linearity, in memory.

4. The method according to claim 3, further comprising the steps of:

reading digital video image data out of said memory means;

applying a gamma correction to the digital video image data read out of said memory using the gamma-correction data of said output look-up table;

converting the corrected digital video image data into an analog video; and

applying the analog video signal to said display device.