JPH0642722B2 - Imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image pickup apparatus using a photoelectric conversion element having a photocharge storage region whose potential is controlled via a capacitor.

The image pickup apparatus according to the present invention is, for example, an image input apparatus, a workstation, a digital copying machine, a word processor,
It is also applicable to a barcode reader, a photoelectric conversion subject detection device for autofocus such as a camera, a video camera, and an 8 mm camera.

[Prior art]

2. Description of the Related Art In recent years, research on photoelectric conversion devices, particularly solid-state imaging devices, has been conducted mainly on two systems, CCD type and MOS type.

The CCD type image pickup device forms a potential well under a MOS type capacitor electrode and accumulates electric charges generated by light incidence in this well. At the time of reading, these potential wells are sequentially moved by a pulse applied to the electrode and accumulated. The principle of transferring the stored electric charge to the output amplifier and reading it is used. Therefore, the structure is relatively simple, the noise generated in the CCD itself is small, and low-illuminance shooting is possible.

On the other hand, the MOS type image pickup device accumulates the electric charge generated by the incidence of light in each of the pn junction photodiodes which constitute the light receiving section, and turns on the MOS switching transistors connected to the respective photodiodes at the time of reading. The principle is that the accumulated charge is read out to the output amplifier. Therefore, CCD
Although the structure is more complicated than the mold, the storage capacity can be increased and the dynamic range can be widened.

However, these conventional type image pickup devices have the following drawbacks, and thus have been a major obstacle in promoting higher resolution in the future.

In the CCD type image pickup device, 1) the MOS type amplifier is turned on as an output amplifier, so that 1 / f noise, which is easily noticeable on an image, is generated from the interface between silicon and a silicon oxide film. 2) If the number of cells is increased to increase the density in order to achieve higher resolution, the maximum amount of charge that can be stored in one potential well decreases, and the dynamic range cannot be obtained. 3) Since the structure is such that accumulated charges are transferred, if there is even one defect in the cell, the charge transfer is stopped there and the manufacturing yield deteriorates.

In the MOS type image pickup device, 1) a large signal voltage drop is generated because a wiring capacitance is connected to each photodiode at the time of signal reading. 2) Large wiring capacitance
This causes a large amount of random noise. 3) M for scanning
Fixed pattern noise is mixed due to variations in the parasitic capacitance of the OS switching transistors. For this reason, low-illuminance imaging becomes difficult, and if each cell is reduced in order to achieve higher resolution, the accumulated charge is reduced, but the S / N ratio becomes smaller because the wiring capacitance does not become so small.

As described above, the CCD-type and MOS-type image pickup devices have an essential problem in achieving higher resolution. For these image pickup devices, a new type of semiconductor image pickup device has been proposed (Japanese Patent Laid-Open Nos. 56-150878 and 56-56).
157073, JP-A-56-165473). In the method proposed here, charges generated by light incidence are transferred to a control electrode (for example, a base of a bipolar transistor, a static induction transistor SIT or MO).
It is stored in the gate of the S-transistor, and the stored charge is read by performing charge amplification using the amplification function of each cell. With this method, high output, wide dynamic range, low noise and nondestructive readout are possible, and there is a possibility of high resolution.

[Problems to be solved by the invention]

However, when the photoelectric conversion signal is read a plurality of times in the nondestructive read mode, the read signal amplitude decreases. This is because the electric charge accumulated in the base of the photoelectric conversion element is discharged by the base current when the signal current of the photoelectric conversion element is read. Such charge attenuation can be represented by the following approximate expression based on the current amplification factor hFE of the photoelectric conversion element, the equivalent base capacitance CB, and the emitter load capacitance CV.

For example, hFE = 2000, CB = 0.1PF, CV = 4P
If it is F, the charge will be reduced by 2% by one read. Therefore, if the nondestructive reading is repeated a plurality of times, the output signal of the image pickup device will decrease according to the number of times of reading. Therefore, by using the above-mentioned nondestructive read mode, for example, by changing the combination of the horizontal lines of the image pickup device, the first read signal is used as the first field signal and the second read signal is used as the second field signal. If you make a recording and play it back on the display, the difference in signal level between fields will be flickering, and the screen will be very difficult to see.

In addition, when a moving subject is recorded as a moving image using a conventional image recording device and viewed as a still image of a frame during playback, the still image is blurred because the recording time is shifted by 1/60 seconds at each field. There was a drawback that became.
Therefore, in order to obtain a complete still image, it is necessary to form signals for two fields at the same time by using a means similar to a shutter and read them sequentially, which requires a large number of pixels. Further, when recording a moving image, there was a problem that flickers and signal level fluctuations had to be prevented as much as possible.

An object of the present invention is to provide an image pickup device that solves the above problems.

Another object is to provide an image pickup apparatus capable of forming a high quality image with a simple structure.

[Means for solving problems]

In order to achieve the above-mentioned object, in the present invention, an image pickup device composed of the number of photoelectric conversion cells which can be read nondestructively, a driving means for nondestructively reading an information signal photoelectrically converted from the image pickup device a plurality of times, and a reading operation. The image pickup apparatus has a gain control unit that changes the gain of the information signal according to the number of times.

[Action]

With this configuration, it is possible to correct the deterioration of the read output and suppress the flickering phenomenon.

〔Example〕

An embodiment of the photoelectric conversion device of the present invention will be described with reference to the drawings.

FIG. 2 shows a circuit configuration diagram of a photoelectric conversion device in which the nondestructive readable optical sensor cell structure as described above is two-dimensionally arranged. The structure of the sensor cell is described in, for example, JP-A-60-1.
The one shown in Japanese Patent No. 2764 may be used.

A basic photosensor cell 30 surrounded by a dotted line (the collector of the bipolar transistor is connected to the semiconductor substrate and the semiconductor substrate electrode. Horizontal lines 31, 31 ', 31 "for applying the read pulse and the refresh pulse.
...... Vertical shift register 32 interlace circuit IL for generating read pulse, interlace circuit IL
And the horizontal lines 31, 31 ', 31 "... Between the buffer MOS transistors 33, 33', 33" ... The buffer MOS transistors 33, 33 ', 33 ". , A buffer MOS transistor for applying a refresh pulse .... 3
5, 35 ', 35 ", a terminal 36 for applying a pulse to its gate, a vertical shift register 52 for applying a refresh pulse, a vertical line 38 for reading an accumulated voltage from the basic photosensor cell 30, 38 ', 38 "
... and 51, 51 ', 51 "... a horizontal shift register 39 for generating a pulse for selecting each vertical line,
MOS transistors 40, 40 ', 40 "for gates, 49, 49', 49" for opening and closing each vertical run.
... Output line 41 for reading the accumulated voltage to the amplifier section,
After reading 59, MOS transistors 42, 53, and MOS transistors for refreshing the charge accumulated in the output line.
Terminals 43 and 54 for applying a refresh pulse to the transistors 42 and 53, transistors 44 and 55 such as a bipolar, MOS-FET and J-FET for amplifying an output signal, load resistors 45 and 56 and a transistor 4
Terminals 46 and 57 for connecting 4, 55 to a power source, output terminals 47 and 58 of the transistors, and MOS transistors 48 and 48 for refreshing charges accumulated on the vertical lines 51, 51 'and 51 "in the read operation. ′,
This photoelectric conversion device is constituted by 48 "... 50, 50 ', 50" and terminals 49 for applying a pulse to the gates of the MOS transistors 48, 48', 48 "... 50, 50 ', 50". ing.

Further, in the image pickup device of the present invention, each portion 32 of the photoelectric conversion device,
Clock driver CK for supplying drive pulses to 34, 36, 39, 43, 49, 52, IL, 54
D, and a clock generator CKG for supplying a timing pulse to this clock driver. Further, the clock driver CKD and the clock generator CKG constitute a control means.

Next, FIG. 3 is a diagram showing a driving method of the image pickup apparatus by the control means, where n1, n2 ... Are row information consisting of each sensor cell, and in an odd field, as shown in the figure, n1 and n2 are O1 lines, n3 and so on. The information of the O2 line is formed from n4, and in the even field, the combination of the row information is changed from that of the odd field to change the line information from n2 and n3 to the e1 line and from n4 and n5 to e2.
Form line information.

Therefore, the interlace circuit IL simultaneously reads out two horizontal line information in a combination of two lines as shown in FIG. 3 for each field, and outputs this information to the output terminals of 47 and 58, respectively. Further, in this embodiment, since the control is performed in the nondestructive read mode, the refresh of the row information is not performed until the reading of the even field is completed. Therefore, the same information is read as the first time in the odd field and is read as the second time in the even field.

Next, FIG. 1 is a signal processing block diagram for realizing the nondestructive reading method described in FIG.

In the figure, 90 is a shutter, 100 is a sensor, CK
D is a driver, CKG is a clock generator, and SYS is a system controller. Further, 200 and 300 are gain adjusters for adjusting the signal gain in the even field in the nondestructive read mode, SW1 is odd, the signal switching switch 500 in the even field is a brightness processing circuit for forming a brightness signal, and 600 is A color processing circuit for forming a color signal,
A luminance signal Y and a color difference signal R 700 are obtained by obtaining luminance and color signals and performing processing such as gamma correction and AGC white balance.
It is a process circuit that forms -Y and BY signals.

Next, reference numeral 800 denotes a magnetic recording circuit including a color difference line-sequential signal forming device for line-sequencing the RY and BY color-difference simultaneous signals, an FM modulator for FM-modulating luminance and color difference line-sequential color signals, and a recording amplifier. Become. A recording head 900 records an FM signal for video floppy (not shown). Next 1
000 is an encoder that forms an NTSC signal and
This NTS and a signal are supplied to R and the like.

The NTSC signal is input to the EVF 1100 and monitored. MSW is a mode switching switch RL for switching between still image recording (still) mode and moving image recording (movie) mode, and RL is a trigger release switch for instructing shooting and recording.

Next, the operation of the still mode indicated by the fourth solid line in the figure will be described. M
When the still mode is selected by SW, after the release switch 4RL is turned on (t ₁ ), the shutter is once exposed for a predetermined time (t _{3 to} t ₄ ), and then the shutter is closed as shown in FIG. Read control is t ₅ to t ₈
It will be done over 2 field periods. At this time, the signals read from the output terminals 47 and 58 of the sensor 100 are switch SW1 by the syscon SYS at an odd field.
In, the PSW is at the low level during the period from t _{5 to} t ₇ as indicated by the solid line in the fourth figure, so that the terminals a and c are connected. Therefore, the output of the sensor is not level-adjusted by the circuits 200 and 300, and the brightness processing circuit 500 and the color processing circuit 60
0, the magnetic recording circuit 800, and the magnetic head 900 are used to record to the nth track of the video floppy. And the magnetic head 900 records even field signals,
It is sent to the (n + 1) th track.

Since the sensor 100 is read in the non-destructive mode in the even field, the output signal from the sensor 100 is reduced by several percent. Therefore, the signal gain adjusters 200, 30
At 0, level up adjustment is performed so as to compensate for the above loss of several percent. That switch SW1 as the fourth illustrated solid line control pulse PSW from the system controller SYS is terminal b and the terminal c is connected by a between a high level of _t 7 ~t _8. Therefore, an even field signal having substantially the same amplitude as the odd field is connected to the luminance processing circuit and the color processing circuit in the subsequent stage and recorded in the (n + 1) th track.

Then, the magnetic head is sent to the next (n + 2) th track, recording of one frame is completed, the next photographing standby state is set, and then the release switch is turned on.

As described above, since the signal levels of the odd field and the even field are controlled to be almost the same, it is possible to obtain a high-quality image without flickering.

Next, an example of the movie mode will be described using the dotted line in the fourth diagram. RL and φF are the same as in the still mode.

That is, during movie shooting, release switch RL is turned on (t ₁
~t ₆₎ by Shiyatsuta is still image storage therebetween open state, when being read immediately after reading which become destructive read mode, performs Rifuretsushu of the line. At this time, switch SW1 is connected to syscon SY so that ac is always connected.
The pulse PSW is controlled to a low level by S. The black poke drivers and circuit 800 operates only during the _t 2 ~t _6.

Next, FIG. 5 shows the clock driver CK of the first embodiment shown in FIG.
FIG. 7 is a schematic timing diagram of control pulses supplied from D to the sensor 100.

Other pulses will be described with reference to the horizontal blacking pulse HBLK shown in FIG. In the figure, (B) (φH-RF) and (C) (φU-RF) are refresh pulses supplied to the shift register 52 and the terminal 149, respectively, and these pulses are supplied during the horizontal blanking period and the sensor The electric charges accumulated in the base of the and the vertical lines are transferred one by one to the transistors …… 48,48 ′, 48 ″ ……, ……
Reflect to ground via 50, 50 ', 50 ".

Next, the pulse (D) (φHS) is applied to the horizontal shift register 39.
Further, (F) (φVS) is a shift pulse of the vertical shift register 32. Further, (E) (φHS-RF) is a bit refresh pulse supplied to the terminals 43 and 54.

Of the above-mentioned pulses, the refresh pulse (B) (C) is related to the selection of each mode for reading the sensor information in a destructive or non-destructive manner. That is, if the refresh pulse is stopped, the nondestructive read mode is set.

Therefore, in the system controller SYS, the clock generator CKG
Also, by controlling the driver CKD, it is possible to freely select moving image recording or still image recording. At the time of destructive reading, pulses φH-RF and φV are generated every horizontal blanking period as shown in FIG.
-Reflect the information in the row immediately after the reading by RF, and φH-RF, φV-R for nondestructive reading.
By not supplying F, it is possible to read the same row signal twice in succession with an odd field and an even field.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7.

FIG. 6 is an explanatory diagram when the row information of the sensor 100 is read out simultaneously for three lines. Since the structure of the sensor 100 is only changed from the 2-line reading in FIG. 2 to the 3-line reading, the details are omitted. In the odd field, line information n1, n2, n3 forms O1 line and n3, n4, n5 forms O2 line. In this case, when shooting a movie, the information in the odd-numbered rows is read nondestructively.

Next, in the even field, the combination of reading row information is changed. That is, from n2, n3, n4 to e1 line, n4, n
An e2 line is formed from 5, n6.

At this time, in the movie mode, the information of even rows is read nondestructively. In the still mode, all row information is read nondestructively.

Therefore, in the odd field of the movie mode and the still mode, of the three lines of information forming each line 01, 02, 03 ..
Only the output is reduced.

Similarly, for the even field in the movie mode, only the first row (even-numbered row information) of the three pieces of row information forming each of the lines e1, e2, e3, ... Output decreases.

On the other hand, in the even mode field in the still mode, the upper two pieces of row information among the three pieces of row information forming each line e1, e2, e3 ... It can be seen that the lower one row information is read for the second time and the rate of output decrease is small.

Next, FIG. 7 is a signal processing block diagram of the sixth embodiment shown in FIG. In this embodiment, the following processing circuit is added to the first illustrated embodiment.

First, 101 is a multiplexer. This multiplexer works as follows.

That is, in the output lines of each row of n1 to n7 ... In FIG. 6, for example, n1, n4, n7 ... Are structurally connected to the first output terminal x1, and n2, n5, n8. 2 is connected to the output terminal x2, and n3, n6, n9 ...
Is connected to the output terminal x3 of.

On the other hand, in the multiplexer 101, x1, x2, and x3 are respectively set to x when controlling the reading of the sensor 100 in order to form the horizontal line output 01 having an odd field.
4, x5, x6, and when forming 02, x
3, x1, x2 are connected to x4, x5, x6 respectively, and 03
To form x2, x3, x1 respectively x4, x
5x6. Similarly for each horizontal line x
The connection relationship between 1 to x3 and x4 to x5 is switched.

When forming an even field e1, the multiplexer 101 converts x2, x3, x1 into x4, x5, x, respectively.
When connecting to 6 to form e2, x1, x2, x3
To x4, x5, x6 respectively, and when forming e3, x3, x1, x2 are respectively connected to x4, x5, x6.

Also, as described above, when each horizontal line is formed in both the movie and still modes, only one output of the three-line output always has a different level from the other two outputs.
Signal gain adjuster 20 for adjusting the signal level at that time
0,300 are provided. That is, in the movie mode, even with an odd field as described above, the highest output of the three outputs of FIG. 6, that is, the output of the output line x4 in FIG. 7, decreases, so the signal gain adjustment for gain up is performed. Bowl 2
At 00, the output of x4 is adjusted to the output levels of x5 and x6.

On the other hand, in the still mode, the output level of the lowest x6 is higher than the outputs of x4 and x5 as described above, and therefore the signal gain adjuster 300 for gain reduction changes the output of x6 to x.
Do it according to the output of 4, x5.

Therefore, the system controller SYS controls the switch 400 so as to connect ac in the movie mode and bc in the still mode.

Next, the signal gain adjusters 210, 220 and 230 are for gain-up adjusting the deterioration of the signal level in the even field of the still mode. That is, as shown in FIG. 6, in the even field in the still mode, the third or second read is performed, so that the signal level is greatly reduced, and the flickers are very noticeable. With the gain adjuster 300 described above, the output of x6 is the output of x4, x5, ie
In the still mode, the output difference between the odd-numbered field and the even-numbered field is large because it is adjusted to the read level of the first time. However, the flickering component due to this is the signal gain adjuster 2
Since it is removed at 10, 220 and 230, a high quality image is obtained. The switch 450 is a selection switch to which ef is connected during movie shooting and df is connected during still shooting.

As described above, the flickering problem, which is a problem in adopting the 3-line output system, can be solved, and the horizontal / vertical resolution of the 3-line output system can be improved and the false color signal can be further reduced.

Next, a third embodiment of the present invention will be described. FIG. 8 is an embodiment diagram in which the signal gain adjusters 210, 220, 230 are simplified. That is, the flicker is most noticeable because the luminance signal Y is formed, the luminance signal Y is formed by combining the three-line outputs x4 'to x6' or by dot-sequencing the three-line outputs, and then the signal level is adjusted by the signal gain adjuster 210. I did it in ‘ SW3 is connected to e in the movie mode and d in the still mode like the switch 450. As another method of forming the luminance signal, in the case of double-line output, one of the signals is configured to be an output corresponding to the green filter, and this output may be used as the low-frequency luminance signal, In that case, the signal gain adjuster may be inserted only in the signal line forming the low-frequency luminance signal.

Next, FIG. 9 shows a fourth embodiment in which the signal level is adjusted after processing the sensor output signal. The level of the luminance signal Y is adjusted by the signal gain adjuster 210 ″ before the magnetic recording circuit 800.

Further, in order to reduce the number of signal gain adjusters, the color difference signals are level-adjusted by the signal gain adjuster 300 'after the color difference signals are line-sequentialized by the color difference line-sequential signal forming circuit 800'. SW
4, SW5 side in still mode, b in movie mode
It is a snatch that connects to the side. By this processing, it is possible to remove the flickering component of the luminance signal due to the nondestructive reading, the color signal shift, the white balance shift, and the color flickering.

As described above, when non-destructive reading is performed a plurality of times, the signal level is adjusted according to the number of times of reading, so that the luminance component flickers and the color component shifts, the white balance shifts, and the color flickers can be removed. We were able to maximize the features of the non-destructive sensor.

In addition, the non-destructive read mode and the destructive read mode can be switched, so it is possible to select moving images and still images according to the shooting purpose. In addition, it is now possible to take a shooting check before recording a still image without flickering.

〔effect〕

According to the present invention, when the sensor output is read nondestructively a plurality of times, the gain is adjusted according to the number of times of reading, so flickers are eliminated and the image quality is greatly improved.

[Brief description of drawings]

1 is a diagram showing a configuration example of an image pickup device, FIG. 2 is a diagram showing a method of driving the image pickup device by a control means, FIG. 3 is an embodiment diagram of a photoelectric conversion element suitable for the image pickup device of FIG. 1, and FIG. FIG. 5 is a timing diagram of movie and still mode, FIG. 5 is an example diagram of sensor driving timing of FIG. 4 embodiment, and FIG. 6 is a second diagram of the present invention.
FIG. 7 is a diagram showing a driving method of the embodiment of the present invention, FIG. 7 is a structural example diagram of an image pickup apparatus according to the embodiment of FIG. 6, and FIGS. 8 and 9 are third and fourth embodiments of the present invention. . 100 is a sensor, 200, 300, 210, 220,
230 is a signal gain adjuster, SW1, SW3, SW4, S
W5, 400 and 450 are switching switches, SYS is a system controller, CKG is a clock generator, and CKD is a clock driver.

Claims (1)

[Claims] 1. An image pickup device comprising a nondestructive read-out number of photoelectric conversion cells, a driving means for nondestructively reading an information signal photoelectrically converted from the image pickup device a plurality of times, and an information signal according to the number of read times. Apparatus having a gain control means for changing the gain of the image pickup device.