JPH069265U - CCD imager - Google Patents

Abstract

(57) [Abstract] [Purpose] The CCD can be switched from resolution priority to sensitivity priority as necessary, without degrading S / N.
Satisfy both high resolution and high sensitivity requirements. [Structure] A horizontal reset pulse supplied to the output unit 16 of the CCD 1 is thinned by a command for sensitivity increase correction, and the CCD 1
Of the horizontal reset control unit 2 for synthesizing and outputting a plurality of accumulated charges of each pixel in the horizontal direction, and sampling pulses are thinned out by a command for sensitivity increase correction, and the output unit 16
And a sampling section 7 for forming a video signal by each combined electric charge.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a CCD image pickup device such as a television camera using a CCD as an image pickup element.

[0002]

[Prior art]

 Conventionally, this type of CCD image pickup device such as a television camera reads the stored charge pixel by pixel from the CCD to form one pixel in the horizontal direction of the video signal, regardless of the transfer method.

[0003]

[Issues to be solved by the device]

 In the conventional CCD image pickup device, the resolution is increased by increasing the number of pixels in the horizontal direction of the CCD, but on the other hand, the area per pixel is reduced and the sensitivity of the CCD is lowered. That is, the high resolution and high sensitivity of CCD are contradictory requirements, and it is very difficult to satisfy both requirements.

[0006] High sensitivity is required especially in low illuminance. Conventionally, instead of increasing sensitivity of CCD, circuit gain is increased to cope with low illuminance. In this case, S of video signal is reduced. There is a problem that / N deteriorates as the circuit gain increases. An object of the present invention is to make it possible to switch the CCD from resolution priority to sensitivity priority as needed, and to satisfy both high resolution and high sensitivity without degrading S / N.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, in the CCD image pickup device of the present invention, the horizontal reset pulse supplied to the output part of the CCD is decimated by the command for the sensitivity increase correction, and the accumulated charge of each pixel in the horizontal direction of CCD is reduced. It is equipped with a horizontal reset control unit that synthesizes and outputs multiple pixels, and a sampling unit that thins out sampling pulses in response to a sensitivity increase correction command and forms a video signal with each combined charge in the output unit.

[0006]

[Action]

 In the case of the CCD image pickup device of the present invention configured as described above, if there is no command for sensitivity increase correction, the horizontal reset pulse is normally supplied to the CCD from the horizontal reset control unit, and the accumulated charge of each pixel in the horizontal direction is stored. Are read from the output section of the CCD pixel by pixel.

Further, if there is no command for the sensitivity increase correction, the sampling pulse of the sampling unit is also generated normally, and the accumulated charge of each pixel read from the output unit is sampled one pixel at a time, and each pixel of the video signal is sampled. Pixels are formed. On the other hand, when a command for sensitivity increase correction is issued, the horizontal reset pulse is thinned out by this command, and the accumulated charges in the horizontal direction are combined for each pixel and read from the output section of the CCD.

Further, the sampling pulse is also thinned out by the command for the sensitivity increase correction, and each pixel of the video signal is formed by each composite charge read from the output section and sampled. Therefore, when the sensitivity increase correction command is issued, the charge accumulated in the CCD is combined for each plurality of pixels to increase the sensitivity.

Therefore, the resolution of the CCD is lowered by the sensitivity increase command at the time of low-illuminance shooting, but the sensitivity is increased, and the resolution priority is switched to the sensitivity priority, so that the S / N is not deteriorated and the high resolution is obtained. It can meet both the requirements of high sensitivity.

[0010]

【Example】

 One embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 shows a configuration in which a sensitivity increase correction is automatically instructed according to the illuminance of photographing. In FIG. 1, 1 is a two-phase driving CCD as a photographing element, and 2 is a horizontal reset for horizontal transfer to CCD 1. It is a horizontal reset control unit that supplies a pulse, and includes a horizontal reset pulse generator 3, selectors 4 and 5, and a frequency divider 6.

Reference numeral 7 is a sampling unit to which the accumulated charges read from the CCD 1 are supplied, and is formed by a double correlation sampling circuit (CDS circuit). A sampling control unit 8 supplies a sampling pulse to the sampling unit 7, and includes a sampling pulse generator 9, selectors 10 and 11, and a frequency divider 12.

A light amount detector 13 is provided in the vicinity of the image pickup surface of the CCD 1, and is composed of an optical sensor such as cds. A command output unit 14 is connected to the detector 13, and outputs a command to increase the sensitivity to the selectors 4, 5, 10 and 11 at the time of photographing with low illuminance. The CCD 1 is provided with a horizontal transfer unit 15 having a floating diffusion configuration shown in FIG.

The horizontal transfer section 15 is provided with electrodes for transfer gates G1 and G2 for each pixel (for each channel), and an output section 16 is provided with electrodes for a reset gate RG and an output gate OG. ing.

Further, the output section 16 has an output (gate connected to a reset drain RD, a reset (discharge) MOS transistor Qa having a floating diffusion FD, and a floating diffusion FD ( A detection) MOS transistor Qb is provided, and this transistor Qb is connected to the source follower, and the output terminal OUT of the CCD 1 is connected to the source. In FIG. 2A, V _DD is a bias power supply terminal, and Rs is a source resistance of the transistor Qb.

A clock generator (not shown) supplies the transfer gates G1 and G2 with two-phase clock pulses φH1 and φH2 shown in (a) and (b) of FIG. Alternatively, the accumulated charge of each pixel of one horizontal scanning read out from each channel of the accumulation section to the horizontal transfer section 15 is sequentially transferred from the right to the left in FIG. On the other hand, the detector 13 monitors the photographing illuminance of the CCD 1, and the detector 13 supplies a detection output proportional to the photographing illuminance to the command output unit 14.

Further, the command output unit 14 compares the detection output with a reference value as a threshold level, and the output is held at a high level during bright normal shooting when the detection output is equal to or higher than the reference value, and the sensitivity is increased. Do not output the correction command.

During normal shooting when this command is not output, the selectors 4 and 5 of the control unit 2 and the selectors 10 and 11 of the sampling unit 8 are both held at the normal contact α, and the control unit 2 The reset pulse φR of the generator 3 is directly supplied to the CCD 1. The reset pulse .phi.R is generated every charge transfer of each pixel in synchronization with the clock pulse .phi.H1 as shown in FIG. 3C, and is applied to the reset gate RG of the horizontal transfer section 15.

At this time, the reset charge is injected from the reset drain RD connected to the bias power source or the like into the floating diffusion FD through the reset gate RG, and as shown in FIG. -John FD is reset to the potential V _{RD of} drain RD.

When the reset pulse φR disappears, the charge accumulated in each pixel in the horizontal direction is transferred to the left side by the clock pulses φH1 and φH2, and the potential of each part of the horizontal transfer unit 15 is changed to (c) in FIG. ) State. 2 (b) and 2 (c) show the potential (potential) of FIG. 2 (a), and the hatched line shows the existence of electric charges.

Further, due to the transfer movement of the charges, the accumulated charges for one pixel at the leftmost end are transferred to the transistor Qb via the floating diffusion FD, and the sampling unit 7 is output from the transistor Qb via the output terminal OUT. Read to. Then, the transfer and the reading based on the reset pulse φR and the clock pulses φH1 and φH2 are periodically repeated, and the electric charge of each pixel in the horizontal direction is sequentially read to the output terminal OUT.

At this time, the potential V _OUT of the output terminal OUT changes according to the read charge of each pixel as shown in (d) of FIG. Further, during normal photographing, the selectors 10 and 11 are held at the normal contact α, so that the control unit 8 supplies the two-phase output pulses of the generator 9 to the sampling unit 7 as sampling pulses SH1 and SH2.

The two pulses SH1 and SH2 are generated immediately after the resetting of the floating diffusion FD and immediately after the charge injection, as shown in (e) and (f) of FIG.

Then, the sampling section 7 samples the precharge level and the signal level by the sampling pulses SH1 and SH2, and by the so-called double synchronous sampling method, the CCD in accordance with the periodic resetting of the floating diffusion FD. The main noise is reduced and removed to form a video signal (image signal), which is supplied to the signal processing circuit in the subsequent stage. Therefore, during normal shooting, the CCD 1 operates with priority on resolution, and high-resolution shooting based on the original resolution of the CCD 1 is performed.

Next, at the time of low illuminance imaging in which the detection output of the detector 13 becomes smaller than the reference value, the output of the command output unit 14 is inverted to the low level and the sensitivity increase correction is instructed, and the selectors 4, 5, Both 10 and 11 are switched to the sensitized contact β.

At this time, the reset pulse φR of the generator 3 is, for example, divided by 1/2 by the frequency divider 6 and thinned out, and as shown in FIG. 4C, (a) and (b) in FIG. The reset pulse .phi.R 'having a period twice that of the clock pulses .phi.H1 and .phi.H2 in (1) is supplied from the control unit 2 to the CCD 1.

Then, the reset pulse φR ′ resets the floating diffusion FD of the CCD 1 at every charge transfer of two pixels, and the potential V _OUT of the output terminal _OUT is as shown in (d) of FIG. For example, immediately before the reset pulse φR ′ corresponding to the timing of (d) of FIG. 3, the accumulated electric charges of the two pixels are added and synthesized to have a positive potential.

That is, since the reset period of the floating diffusion FD extends twice as long as that during normal photographing, the accumulated charges of each pixel in the horizontal direction are added and combined by two pixels and read from the CCD 1 in a two-pixel cycle. To be done.

The two-phase output pulse of the generator 9 is also divided by 1/2 by the frequency divider 12 to be thinned out, and as shown in (e) and (f) of FIG. Sampling pulses SH1 and SH2 having a 2-pixel cycle without the eye pulse are supplied from the control unit 8 to the sampling unit 7.

Then, in response to the sampling pulses SH1 and SH2, the sampling unit 7 extracts only the added and combined charge of each two pixels output from CC D1, and two pixels are formed with the same charge, but the level is 2 A video signal that has been double-corrected is formed.

Therefore, during low-illuminance shooting, the charge accumulated in each two pixels in the horizontal direction of the CCD 1 is combined to form a charge for one pixel of the video signal, and the CCD 1 has a horizontal resolution higher than that in normal shooting. Although it is reduced to half, it can be switched to double the sensitivity, and shooting can be performed with priority on sensitivity.

Since the sensitivity of the CCD 1 is increased to deal with low illuminance instead of increasing the circuit gain, the S / N ratio of the video signal does not deteriorate. Moreover, since the number of resets of the floating diffusion FD due to the reset pulse φR 'is smaller than that during normal photographing, the noise of the CCD 1 due to the resetting of the diffusion FD is reduced, and the S / N due to this noise is reduced. Does not deteriorate.

Further, in the above embodiment, the reset pulse φR and the sampling pulses SH1 and SH2 are divided into 1/2 when the illuminance is low, but they may be divided at a division ratio different from that of the embodiment. Further, instead of being automatically switched by the detection output of the detector 13, it may be manually switched by button operation or the like. And, of course, it can be applied to various driving type and charge transfer type CCD image pickup devices.

[0033]

[Effect of device]

 Since the present invention is configured as described above, it has the following effects. When a sensitivity increase correction command is issued, the horizontal reset pulse of the CCD 1 is decimated by the horizontal reset control unit 2, and the charges accumulated in the horizontal direction of the CCD 1 are added and combined pixel by pixel and read out from the CCD 1 to the sampling unit 7, and this sampling unit is also used. Since the sampling signal of 7 was thinned out to form the video signal by each added and combined charge, the sensitivity of CCD 1 can be improved without deteriorating the S / N at the time of low illuminance shooting by a simple method of thinning out the horizontal reset pulse and sampling pulse. It is possible to perform high-resolution shooting with priority on resolution during normal shooting, and high-sensitivity shooting with priority on sensitivity during low-light shooting, which satisfies both high-resolution and high-sensitivity requirements. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a CCD image pickup device of the present invention.

2 (a), (b), and (c) are a configuration explanatory view of a horizontal transfer unit of the CCD of FIG. 1, a potential explanatory diagram in a certain state, and a potential explanatory diagram in another state.

3 (a) to 3 (f) are timing charts during normal shooting in FIG.

4A to 4F are timing charts at the time of low-illuminance shooting in FIG.

[Explanation of symbols]

 1 CCD 2 horizontal reset control unit 7 sampling unit 15 horizontal transfer unit 16 output unit

Claims (1)

[Scope of utility model registration request] 1. A horizontal reset pulse supplied to an output section of a CCD is thinned by a command for sensitivity increase correction,
, A horizontal reset control unit for synthesizing and outputting a plurality of pixels of the accumulated charge of each pixel in the horizontal direction, and sampling pulses are thinned by the command of the sensitivity increase correction, and a video signal is generated by each of the synthesized charges of the output unit. A CCD image pickup device including a sampling unit to be formed.