Driving apparatus for solid-state image pickup element and driving method therefor

Abstract

According to one embodiment, a driving apparatus for a solid-state image pickup element includes a generating unit configured to generate a drive voltage having an amplitude to obtain a predetermined multiplication gain to an electron-multiplying solid-state image pickup element, a calculating unit configured to calculate a change amount obtained when the multiplication gain of the solid-state image pickup element changes depending on elapsed time and conditions in actual use, and a correcting unit configured to correct an amplitude of the drive voltage output from the generating unit to obtain a predetermined multiplication gain on the basis of the change amount calculated by the calculating unit.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.

FIG. 1 shows an embodiment of the invention and is a diagram for explaining a schematic configuration of a monitoring camera;

FIG. 2 is a block diagram shown to explain a signal processing system of a color camera used in the monitoring camera in the embodiment;

FIG. 3 is a graph shown to explain a variation in gain occurring with elapsed time of an electron-multiplying CCD used in a color camera in the embodiment;

FIG. 4 is a graph shown to explain a variation in gain with a multiplication gain of the electron-multiplying CCD used in the color camera in the embodiment;

FIG. 5 is a graph shown to explain a variation in gain with a saturation area of the electron-multiplying CCD used in the color camera in the embodiment; and

FIG. 6 is a flow chart shown to explain a correcting operation of a variation in gain by a control unit used in the color camera in the embodiment.

Claims

1. A driving apparatus for a solid-state image pickup element, comprising: a generating unit configured to generate a drive voltage having an amplitude to obtain a predetermined multiplication gain to an electron-multiplying solid-state image pickup element;a calculating unit configured to calculate a change amount obtained when the multiplication gain of the solid-state image pickup element changes depending on elapsed time and conditions in actual use; anda correcting unit configured to correct an amplitude of the drive voltage output from the generating unit to obtain a predetermined multiplication gain on the basis of the change amount calculated by the calculating unit.

2. A driving apparatus for a solid-state image pickup element according to claim 1, wherein the calculating unit is configured to calculate a change amount of a multiplication gain on the basis of use time of the solid-state image pickup element, a level of a multiplication gain at which the solid-state image pickup element is driven, and the number of saturation pixels of the solid-state image pickup element.

3. A driving apparatus for a solid-state image pickup element according to claim 1, wherein the calculating unit is configured to calculate a change amount of the multiplication gain on the basis of total use time for which the solid-state image pickup element is driven in electron multiplication, weighting coefficient set to show damage to the solid-state image pickup element depending on a level of a multiplication gain at which the solid-state image pickup element is driven, and a ratio of the number of saturation pixels occupied in the total number of pixels of the solid-state image pickup element.

4. A driving apparatus for a solid-state image pickup element according to claim 1, wherein the calculating unit is configured to calculate a change amount of a multiplication gain by performing an arithmetic operation given by DF×SA×logT on the basis of total use time T for which the solid-state image pickup element is driven in electron multiplication, a weighting coefficient DF set to show damage to the solid-state image pickup element depending on a level of the multiplication gain at which the solid-state image pickup element is driven, and a ratio SA of the number of saturation pixels occupied in the total number of pixels of the solid-state image pickup element.

5. A driving apparatus for a solid-state image pickup element according to claim 1, wherein the correcting unit is configured to correct an amplitude of a drive voltage output from the generating unit when the change amount calculated by the calculating unit exceeds a predetermined threshold value set in advance.

6. A color camera device having an electron-multiplying solid-state image pickup element, comprising: a generating unit configured to generate a drive voltage having an amplitude to obtain a predetermined multiplication gain to the solid-state image pickup element;a processing unit configured to perform predetermined signal processing to an output signal from the solid-state image pickup element driven on the basis of the drive voltage output from the generating unit and to output the signal to the outside;a calculating unit configured to calculate a change amount obtained when the multiplication gain of the solid-state image pickup element changes depending on elapsed time and conditions in actual use; anda correcting unit configured to correct an amplitude of the drive voltage output from the generating unit to obtain a predetermined multiplication gain on the basis of the change amount calculated by the calculating unit.

7. A driving method for an solid-state image pickup element comprising: a first block of generating a drive voltage having an amplitude to obtain a predetermined multiplication gain to an electron-multiplying solid-state image pickup element;a second block of calculating a change amount obtained when the multiplication gain of the solid-state image pickup element changes depending on elapsed time and conditions in actual use; anda third block of correcting an amplitude of the drive voltage output in the first block to obtain a predetermined multiplication gain on the basis of the change amount calculated in the second block.

8. A driving method for a solid-state image pickup element according to claim 7, wherein in the second block, a change amount of a multiplication gain is calculated on the basis of use time of the solid-state image pickup element, a level of a multiplication gain at which the solid-state image pickup element is driven, and the number of saturation pixels of the solid-state image pickup element.

9. A driving method for a solid-state image pickup element according to claim 7, wherein in the second block, a change amount of the multiplication gain is calculated on the basis of total use time for which the solid-state image pickup element is driven in electron multiplication, a weighting coefficient set to show damage to the solid-state image pickup element depending on a level of a multiplication gain at which the solid-state image pickup element is driven, and a ratio of the number of saturation pixels occupied in the total number of pixels of the solid-state image pickup element.

10. A driving method for a solid-state image pickup element according to claim 7, wherein the second block includes:a first calculating block of calculating total use time T for which the solid-state image pickup element is driven in electron multiplication;a second calculating block of calculating a weighting coefficient DF set to show damage to the solid-state image pickup element depending on a level of the multiplication gain at which the solid-state image pickup element is driven,a third calculating block of calculating a ratio SA of the number of saturation pixels occupied in the total number of pixels of the solid-state image pickup element; anda fourth calculating block of performing an arithmetic operation given by DF x SA x logT depending on respective values calculated in the first to third blocks to calculate a change amount of the multiplication gain.

11. A driving method for a solid-state image pickup element according to claim 7, wherein in the third block, an amplitude of a drive voltage output in the first block is corrected when the change amount calculated in the second block exceeds the predetermined threshold value set in advance.