JPH0473833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an imaging device that can realize a relatively short storage time.

<Summary of the Disclosure> This specification and the drawings describe an imaging device in which the accumulation time can be controlled, in which the charges accumulated in the light receiving section of the imaging means are once removed, and during the subsequent period substantial accumulation is carried out and the charges are eliminated. By providing a control means that intermittently erases unnecessary charges during the charge accumulation period and continuously erases unnecessary charges during the actual charge accumulation period, the object can be imaged in a short accumulation time. The present invention also discloses a technology that makes it difficult for blooming to occur.

<Prior art> When a solid-state image sensor, such as a CCD (charge-coupled device), is used in a television camera, by changing the driving method of the solid-state image sensor, the field (or frame) time of the television signal can be Conventionally, it has been proposed that the accumulation time of .

For example, in a solid-state image sensor called a frame transfer type, the charge in the light receiving part that performs photoelectric conversion and charge accumulation is forcibly removed by vertical transfer once in the middle of the vertical time, and then the charge is removed during the remaining vertical time. For example, Japanese Patent Application No. 58-61098 proposes a driving method that operates as a substantial accumulation time.

According to the above-mentioned method, for example, an NTSC TV camera normally has an accumulation time of 1/60 seconds, but this can be changed to 1/120 seconds, 1/500 seconds, etc., which allows for a large amount of light. There is no need to make a small aperture during incidence. Therefore, a blurring effect can be obtained.
Further, effects such as the image of a high-speed moving object being prevented from blurring are produced.

<Problems to be Solved by the Invention> However, if the actual storage time is shortened, the aperture must be lower than the normal case in order to obtain the same video signal level as with the normal storage time (1/60 seconds). opens, allowing a large amount of light to enter. the result,
Charge is more likely to be generated in the CCD light receiving area, and blooming is more likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to propose an imaging device that can eliminate the drawbacks of the above-mentioned conventional example and at the same time improve the anti-blooming ability when the substantial storage time is set short.

<Means for solving the problems> FIG. 1 is a diagram showing an outline of the present invention, and shows 10
0 includes a light receiving section for receiving a subject image inside an imaging means such as a CCD, MOS, or image pickup tube.

Reference numeral 200 denotes a control means for controlling the imaging means, and controls discharge, accumulation, erasure, etc. of charges within the imaging means.

An image signal formed and read out by the imaging means is guided to an output terminal 300.

<Function> After the control means once discharges the charge in the imaging means, the image is substantially accumulated until the next readout.

This accumulated charge is read out to the output terminal 300 in conjunction with the next discharge operation or at a timing different from this discharge operation.

The control means further causes unnecessary charges to be erased in the light receiving section in the imaging means continuously while substantial accumulation is being performed, and erases unnecessary charges in the light receiving section within the imaging means during the accumulation of charges formed before subsequent discharge. Do this intermittently.

This makes it possible to effectively prevent blooming even if strong light is incident when the actual storage time is shortened.

Further, while reading out the charges accumulated during the substantial accumulation time, the noise accompanying erasing of the unnecessary charges is reduced.

<Examples> Examples of the present invention will be described below with reference to the drawings.

An embodiment of the present invention will be described using a frame transfer type CCD as an example of imaging means.

To explain with reference to FIG. 2, the figure shows an example of a frame transfer type CCD. In the figure, 1 indicates a frame transfer type CCD, and 2 indicates an electrical signal in response to incident light , an imaging section (light receiving section) that generates and accumulates charges, and 3 a storage section (accumulation section) that takes in the charges generated and accumulated in the imaging section 2 and temporarily stores them. ), 4 is a horizontal register section for sequentially reading out the charges stored in the storage section 3 one line at a time, and 5 is an output amplifier provided on the output side of the horizontal register section 4 for converting the charges into voltage. Department.

As is well known, the imaging unit 2 has a two-dimensional array of imaging cells along a predetermined number of rows and columns, and the storage unit 3 has an equivalent number of imaging cells along the same rows and columns. The horizontal register section 4 has a one-dimensional array of charge transfer cells along the rows, the number of which is at least equal to the number of memory cell arrays in the memory section 3. The imaging unit 2 is shielded from light except for a predetermined area.

When such a frame transfer type CCD 1 is driven at the television cycle, charges generated and accumulated in the imaging section 2 are vertically transferred from the imaging section 2 to the storage section 3 during the vertical blanking period of the television. Further, the charges stored in the storage section 3 are step-transferred to the horizontal register section 4 one line at a time during the horizontal blanking period.

Also, within the period of one horizontal line, the horizontal register section 4
The charges within are horizontally transferred to the output amplifier section 5.

A single-phase drive anti-blooming gate type CCD will be described below.

FIG. 3 is a diagram showing the configuration of main electrodes near the boundary between the imaging section 2 and the storage section 3.

CS is a channel stop that separates horizontal pixels, φI is a drive electrode for the light receiving section, φABG is an anti-blooming gate electrode, φS is a storage section drive electrode,
CB is the drive barrier area, CW is the drive well area,
VB is a virtual barrier area, and VW is a virtual well area.

FIG. 4 is a cross-sectional view taken along line A-A' in FIG.
A virtual phase potential is formed in VB and VW by implanting P ions, and furthermore, from the viewpoint of electrons, CB>CW,
N ions are implanted to form a potential distribution of VB>VW. 21 is this CCD
indicates the direction of transfer. FIG. 5 is a potential distribution diagram of this CCD, in which VB and VW are fixed to virtual phases, and the potentials of the CB, CW, and ABG sections change as shown in FIG. 5 depending on the driving voltage. 6th
The figure shows the drive voltage waveform of this CCD in the first mode, where 1V indicates the vertical period.

A transfer pulse is added to φI at the beginning of the vertical period, and it takes an intermediate value IM during other charge accumulation periods. At this time, the potentials of CW and VW are almost the same, so charges are accumulated in both CW and VW. or,
Each charge accumulated in CW and VW during transfer is automatically added pair by pair. In this embodiment, by shifting the pairs of charges to be added for each field, the position of the center of gravity of sensitivity is shifted, and an interlacing operation is performed.

A transfer pulse is applied to the electrode φS at the same time as the transfer pulse of φI, and the charge is transferred from the light receiving part to the storage part. After that, one pulse of shift pulse is applied in the horizontal period 1H to transfer the charge from the storage part to the horizontal register. .

During vertical transfer, φABG is fixed at a predetermined intermediate potential ABM between the virtual potentials of regions VB and VW so as not to disturb vertical transfer, and at the same time, during other periods, intermittent pulses of about 500KHz to 2MHz are applied horizontally every 1H. In addition to the blanking period, unnecessary charges above a predetermined level are removed by charge recombination.

A method for removing unnecessary charges by charge recombination is disclosed in Tokuhan Sho.
58-75838, etc., by driving φABG, a part of the accumulated charge is pushed up to the potential of the recombination center, and by recombining with holes, unnecessary charges are periodically removed. It is something.

FIG. 7 shows a driving voltage waveform in a second mode for performing a so-called electronic shutter operation in which vertical charge transfer is performed during the storage to reduce the actual storage time.

Compared with FIG. 6, φI and φS are such that a vertical transfer pulse is added at the beginning of the vertical blanking period (V, BLK). Therefore, the charges accumulated during the T ₂ period are removed by this vertical transfer pulse, and T ₁ becomes the actual accumulation time. Further, the V level of φABG is temporarily set to an intermediate value even during the intermediate vertical transfer time.

FIG. 8 shows details of the driving voltage waveform of φABG in this electronic shutter operation, that is, in the second mode.

T ₂ is an accumulation period for charges to be removed as described above, and T ₁ is a substantial accumulation period. _T2
If the amount of charge accumulated in the image is large, even if transfer is performed in the middle, it will not be completely removed and will remain on the output screen. Therefore, continuous pulses are intermittently applied to the φABG electrode every 1H during the horizontal blanking period (H, BLK) to reduce the amount of charge accumulated in _T2 . Furthermore, during the actual storage period _T1 , which is the actual image, continuous pulses are applied to the φABG electrode to enhance the anti-blooming ability.

Here, if continuous pulses are applied to the φABG electrode during the long _T2 , noise will be superimposed on the output amplifier 5 and will appear on the screen. It is also disadvantageous in terms of power consumption of the drive IC and image sensor. Therefore, at _T2 , intermittent pulses are applied every 1H within the horizontal blanking period.

FIG. 9 is a diagram showing an embodiment of the configuration of an imaging device according to the present invention. 101 is a reference oscillator, 102 is a frequency divider, and 103 and 104 are first and second drive pulse generation circuits, and the first drive pulse generation circuit generates pulses φT and φR shown in the second diagram. Further, the second drive pulse generation circuit outputs pulses φI, φS, and φABG. 105 is a drive circuit, 106 is a power source that generates various drive voltages, and 1 is an image sensor.
When the CCD 107 is connected to the mode setting switch, the time setting circuit 108 becomes the first mode, and when it is connected, the time setting circuit 108 becomes the second mode. 109 is AB
A pulse control signal generation circuit, 110 is a smoothing circuit for smoothing the output of the sensor 1, and 111 is an exposure control member such as an aperture or shutter for controlling the amount of exposure of the sensor.

The oscillation output of the reference oscillator 101 is frequency-divided into necessary signals by a frequency divider 102 and sent to a drive pulse generation circuit 103. Alternatively, a pulse necessary for driving the CCD is generated by 104, level-shifted and power amplified by 105 to a voltage supplied from a power supply 106, and the CCD 1 is driven. On the other hand, the vertical retrace pulse V,
When BLK is input to the time setting circuit 107 and the switch 108 is connected to the (second mode) side, a trigger pulse PT is generated which determines the actual accumulation time _T1 . Furthermore, in the AB pulse control circuit 109, φABG is determined by PT, V, and BLK.
control signal for controlling continuous or intermittent pulses of
CABG is generated.

Also, when the switch 108 is connected to the (first mode) side, PT is not output, so
CABG is also always at a low level.

Therefore, at this time, the driving pulse generating circuit 102 outputs pulses φI, φS, φABG as shown in FIG. 6, and an accumulation time of about one field period is obtained.

Further, the output of the sensor 1 is smoothed, and the exposure control member controls the amount of incident light in accordance with this smoothed output.

FIG. 10 is a timing chart of the imaging device shown in FIG. PT to determine the actual accumulation time T ₁
In the _T1 period, CABG is “H” due to V and BLK.
CABG becomes "L" in the _T2 period, and correspondingly, φABG becomes a continuous pulse in the _T1 period and an intermittent pulse in the _T2 period. However, as mentioned above, φABG is φI, φS
During vertical transfer, it is at an intermediate level.

In the above embodiment, a single-phase drive type frame transfer type CCD with an excess charge discharge structure by recombination has been described, but other types can also be used to improve the pixel density by changing the number of drive pulses. If the amount of charge stored in can be varied,
The present invention can be applied.

In addition, in this embodiment, since anti-blooming gate electrodes are provided in the virtual regions VB and VW by charge recombination, if the potential level seen from the electrons in the drive region CBCW is increased with respect to VBVW during the period _T2 , Can enhance anti-blooming ability for _T2 period.

<Effects of the Invention> As described above, according to the present invention, even when the storage time of the imaging means is shortened, the anti-blooming ability can be improved and good images can be obtained. Furthermore, blooming can be effectively prevented without significantly increasing power consumption.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the present invention, FIG. 2 is a configuration diagram of a frame transfer type CCD according to the present invention, and FIG. 3 is a diagram showing an example of the main electrode configuration of the configuration shown in the first diagram.
Figure 4 is a schematic cross-sectional view of the configuration shown in Figure 3, and Figure 5 is a schematic cross-sectional view of the configuration shown in Figure 4.
Potential status diagram in the illustrated configuration; FIG. 6 is a timing chart in a movie imaging mode with an accumulation time of one field; FIG. 7 is a timing chart in an imaging mode with an accumulation time of one field or less; FIG. 8 is a T ₁ period as well as
A diagram showing continuous or intermittent φABG pulses during the T ₂ period, FIG. 9 is a diagram showing an example of the configuration of the imaging apparatus of the present invention, and FIG. 10 is a timing chart of the configuration shown in FIG. 100...imaging means, 200...controlling means, 3
00...Output terminal.

Claims (1)

[Scope of Claims] 1. Imaging means having a plurality of light-receiving sections for converting an optical image into charge information and reading out the charge information at a television cycle; and at least a portion of the charge information in each of the light-receiving sections. signal supply means for supplying a periodic signal to each electrode in the light receiving section for repeatedly recombining the charge with charges of other polarities; and a signal supply means for supplying a periodic signal to each electrode in the light receiving section; 1 time and this 1st
an accumulation time setting means for selectively setting a second time that is shorter than the period of time and approximately corresponds to the vertical blanking period; and controlling the signal supply means in conjunction with the operation of the accumulation time setting means. control means, the control means intermittently outputs the periodic signal of a predetermined frequency when the charge accumulation time is set to a first time; , the periodic signal of the predetermined frequency is continuously output within the second time period, and the periodic signal of the predetermined frequency is output continuously within the second time period within the television cycle. An imaging device characterized in that a periodic signal is output intermittently in correspondence with a horizontal blanking period of the television cycle.