JPS6331377A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent may picture elements from being required especially for the still mode and make it difficult that inter-field flicker occurs in the movie mode, by switching the mode between destructive read and non-destructive mode. CONSTITUTION:Refresh pulses phiH-RF and phiU-RF are supplied to a shift register 51 and a terminal 149 of a sensor respectively in a horizontal blanking period to refresh the stored electric charge to the earth through transistors TRs 48-48'' and 50-50'' line by line. A clock generator CKG and a driver CKD are controlled by a system controller to freely select moving picture recording and still picture recording. Information of the like just after read is refreshed with pulses phiH-RF and phiV-RF in case of destructive read, and pulses phiH-RF and phiV-RF are not supplied in case of non-destructive read, thereby reading out the same line signal twice continuously in an odd field and an even field.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an imaging device using a photoelectric conversion element having a photoelectric charge accumulation region whose potential is controlled via a capacitor.

The imaging device according to the present invention includes, for example, an image input bag, a workstation, a digital copying machine, a word processor,
It is also applicable to barcode leagues, photoelectric conversion object detection devices for autofocus of cameras, video cameras, 8mm cameras, etc.

[Prior art]

In recent years, research on photoelectric conversion devices, particularly solid-state imaging devices, has been conducted mainly on two types: CCD type and MOS type.

A CCD type imaging device forms a potential well under an MO3 type capacitor electrode, stores charges generated by incident light in this well, and during readout, these potential wells are sequentially moved by a pulse applied to the electrode to accumulate the charges. It uses the principle that the generated charge is transferred to the output amplifier and read out. Therefore, the structure is relatively simple, the noise generated by the CCD itself is small, and low-light photography is possible.

On the other hand, a MOS type imaging device accumulates charges generated by incident light in each of the photodiodes made of pn junctions that constitute the light receiving section, and turns on the MOS switching transistors connected to each photodiode sequentially during readout. The principle is that the accumulated charge is read out to the output amplifier. Therefore, C.C.D.
Although it is structurally more complex than the conventional type, the storage tank capacity can be increased and the dynamic range can be widened.

However, these conventional imaging devices have the following drawbacks, which have been a major hindrance in the pursuit of higher resolution in the future.

In a CCD type imaging device, 1) since a MOS type amplifier is installed on-chip as an output amplifier, noticeable l/f noise is generated on an image from the interface between silicon and silicon oxide film. 2) When increasing the number of cells to achieve higher density in order to achieve higher resolution, the maximum amount of charge that can be stored in one potential well decreases, making it impossible to maintain a dynamic range. 3) Since the structure is such that accumulated charges are transferred, if there is even one defect in a cell, charge transfer will stop there, resulting in poor manufacturing yield.

In the MO5 type imaging device, (1) a large signal voltage drop occurs during signal readout because a wiring capacitor is connected to each photodiode.

2) The wiring capacitance is high, which causes a large amount of random noise, and 3) Fixed pattern noise is mixed in due to variations in the parasitic capacitance of the scanning MOS switching transistor. This makes low-light imaging difficult, and when each cell is reduced to achieve higher resolution, the accumulated charge decreases, but the wiring capacitance does not become much smaller.
The S/N ratio becomes smaller.

As described above, CCD type and MO3 type imaging devices have essential problems in achieving high resolution. A new type of semiconductor imaging device has been proposed for these imaging devices (Japanese Patent Laid-Open No. 150878/1983, Japanese Patent Laid-Open No. 56-150878).
157073, Japanese Unexamined Patent Publication No. 165473/1983), the method proposed here transfers charges generated by incident light to a control electrode (for example, the base of a bipolar transistor, a static induction transistor SIT or a MOS).
The accumulated charge is amplified using the amplification function of each cell and read out. This method allows high output, wide dynamic range, low noise, and nondestructive readout, and has the potential for high resolution.

[Problem that the invention seeks to solve]

However, when the photoelectric conversion signal is read out multiple times in the non-destructive readout mode, the readout signal amplitude decreases. This is a photoelectric transformation! l! This is because the charge accumulated in the base of the photoelectric conversion element is discharged by the base current when reading the signal current of the element.

This kind of charge attenuation means the current amplification factor h of the photoelectric transducer.
F E, equivalent base capacitance CB and emitter load capacitance Cv
It can be expressed by the following approximate formula.

For example, hFE=2000. CB,=O,lPF,CV=
If 4PF is used, the charge will decrease by 2% in one readout. Therefore, if nondestructive readout is repeated multiple times, the output signal of the imaging device will decrease in accordance with the number of times of readout. Therefore, by using the above-mentioned non-destructive readout mode, for example, by changing the combination of each horizontal line of the imaging device,
When a still image is recorded using the first readout signal as the first field signal and the second readout signal as the second field signal, and this is reproduced on a display, the difference in signal level for each field causes flicker.

The screen becomes extremely difficult to view.

In addition, when a moving subject is recorded as a video using a conventional imaging recording device and viewed as a frame still image when played back, the recording time of each field is shifted by 1/60 seconds, resulting in blurred still images. There was a drawback that it became.

Therefore, in order to obtain a complete still image, it is necessary to simultaneously form signals for two fields using a means similar to a shutter and read them out sequentially, which requires a large number of pixels. Another problem is that when recording a moving image, it is necessary to prevent flicker and signal level fluctuations as much as possible.

[Means for solving problems]

In order to achieve the above object, the present invention provides an image sensor made of the photoelectric conversion cell that can be read out non-destructively, and a signal formed by the image sensor that is read out in a destructive read mode and a non-destructive read mode. The image capturing apparatus includes a read mode switching means for switching modes.

[For production]

With this configuration, for example, optimal readout is possible in movie mode and still mode, and in the case of stills, high-resolution images can be easily obtained without increasing the number of images, and in the case of movies, it is possible to easily obtain high-resolution images in the field. Since there is little variation in signal level between the two, reflicker and the like are less likely to occur.

〔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 a non-destructively readable optical sensor cell structure as described above is arranged two-dimensionally.
The one shown in Japanese Patent No. 764 may be used.

A basic photosensor cell 30 (the collector of the bipolar transistor is connected to a semiconductor substrate and a semiconductor substrate electrode) is surrounded by a dotted line.Horizontal lines 31, 31', and 31 for applying read pulses and refresh pulses are shown.
31'' ---Vertical shift register 32 for generating readout pulses Interlace circuit IL, buffer MO between interlace circuit IL and horizontal lines 31, 31', 31'''5) Transistors 33, 33
' , 33 ``Φ・φ eight-fa MO5I-transistor 33, 33'.

Terminal 3 for applying a pulse to the gate of 33″...
4. /Sofa MO for applying refresh pulse
S transistor -35,35'.

35″, terminal 3 for applying a pulse to its gate
6. Vertical shift register 52 for applying refresh pulses, vertical lines 38° 38', 38'', .
1.51', 51"φ...Horizontal shift register that generates a pulse to select each vertical line 39. Gate MOS transistor 40°40', 40# for opening and closing each vertical line... 49.49', 49''...Output line 41.59 for reading out the accumulated voltage to the amplifier section
After reading, MOS transistor stars 42, 53 . M.O.S.
Transistors 42゜53 Helical terminals 43, 54 for applying refresh pulses, bipolar, MOS-FET, J-FET'4 (1) for amplifying the output signal
Terminal 4 for connecting the load resistor 45.56 and transistor 44.55 to the power supply.
6°57, transistor output terminal 47.58. Vertical lines 51, 51', 51'' in read operation
MOS transistor Φ・-48, 48', 48"...050.50' to refresh the charge accumulated in
, 50" and MOS) transistor 4/11 8.48'
, 48"...fist 50.50'.

This photoelectric conversion device is constituted by a terminal 49 and the like for applying a pulse to the gate of 50''.

Further, in the imaging device of the present invention, each part 32 of the photoelectric conversion device,
34, 36, 39, 43, 49, 52° Clock driver CK for supplying drive pulses to IL, 54
D, and a clock generator CKG for supplying timing pulses 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 the driving method of the imaging device by the control means, where nl and n2 row information is row information consisting of each sensor cell, and in the odd field, 01 from nl and n2 as shown in the figure.
Lines, n3 and n4 form 02 line information, and even fields and odd fields change the combination of line information, e1 line from n2 and n3, e1 line from n4 and n5.
2-line information is formed.

For this purpose, the interlacing circuit IL simultaneously reads out two horizontal line information for each field in a combination of two lines as shown in FIG. 3, and outputs this information to output terminals at 47.degree. and 58, respectively. Further, in this embodiment, since control is performed in a non-destructive read mode, row information is not refreshed until the reading of the even-numbered field is completed.

Therefore, the same information is read out the first time in the odd field, and the same information is read out the second time in the even field 1.

Next, FIG. 1 is a signal processing block diagram for realizing the nondestructive readout method described in FIG. 3.

In the figure, 90 is the shutter, 100 is the sensor, CK
D is a driver, CKG is a clock generator, and SYS is a system controller. Further, 200 and 300 are gain adjusters that adjust to increase the signal gain in even fields in the non-destructive read mode, SWI is an odd and even field signal changeover switch 500 is a brightness processing circuit that forms a brightness signal, and 600 is a brightness processing circuit that forms a brightness signal. a color processing circuit that forms color signals;
700 obtains luminance and color signals, performs processing such as gamma correction and AGC white balance, and outputs luminance signal Y and color difference signal R.
This is a process circuit that forms -Y and BY signals.

Next, 800 is a magnetic recording circuit, which includes a color difference line sequential signal generator that converts the R-Y and B-Y color difference simultaneous signals into line sequential, an FM modulator that performs FM modulation of the luminance and color difference line sequential color signals, a recording amplifier, etc. Become. 900 is a recording head that records an FM signal on a video floppy (not shown).
000 is an encoder that forms a PTSC signal and VT
This NTS and signals are supplied to R, etc.

The NTSC signal is input to EvFllOO and monitored. Note that MSW is a mode changeover switch for switching between a still image recording (still) mode and a moving image recording (movie) mode, and RL is a trigger release switch for instructing photography and recording.

Next, the operation in the still mode shown by the solid line in FIG. 4 will be explained. M
When the still mode is selected with the SW, after the release switch 4RL is turned ON (t1), the shutter performs exposure for a predetermined time (t3 to 1+), and then, with the shutter open, readout control is performed as shown in Figure 3. is from t5
It takes place over two fields of seventy-eighths. At this time, the signals read from the output terminals 47 and 58 of the sensor 100 are switched by the system controller SYS in the odd field.
At W1, as shown by the solid line in the fourth figure, PSW is applied between ts and t7.
is at a low level, so the C terminal and the C terminal are connected.

Therefore, the output of the sensor is not level-adjusted by the circuits 200 and 300, but is output by the brightness processing circuit 500 and the color processing circuit 6.
00. Magnetic recording circuit 800. It is recorded on the nth track of the video floppy via the magnetic head 900. The magnetic head 900 is then sent to the (n+1)th rack in order to record even field signals.

In even fields, the sensor 100 is read in a non-destructive mode, so the output signal from the sensor 100 is several percent smaller. Therefore, signal gain: A rectifier 200.3
At 00, the level up to compensate for the loss of the above several percent: A adjustment is performed. That is, as shown by the solid line in the fourth diagram, the b terminal and the C terminal of the switch SWI are connected when the control pulse PSW from the system controller SYS becomes high level between t7 and t8.

Therefore, the even field signal having almost the same amplitude as the odd field is connected to the subsequent luminance processing circuit and color processing circuit and recorded on the (n+1)th track.

Then, the magnetic head is sent to the next (n+2)th) rack, and recording for one frame is completed, and the magnetic head enters the next shooting standby state, waiting for the release switch to be turned on.

As mentioned above, since the signal levels of the odd and even fields were controlled to be almost the same, it was possible to obtain a flicker-free, high-quality image.

Next, an embodiment of the movie mode will be explained using dotted lines in the fourth figure. Note that RL and φF are the same as in still mode.

In other words, when shooting a movie, turn on the release switch RL (t
, ~ts), the shutter remains open during this time and accumulates images, and when reading out, the row is refreshed immediately after reading out so that the destructive readout mode is activated.At this time, the switch SWI is set so that a-C are always connected. Then, the pulse PSW is controlled to low level by the system controller SYS.

Also, the clock driver and circuit 800 only operate between t2 and t6.

Next, FIG. 5 shows the clock driver 〇K of the first illustrated embodiment.
FIG. 3 is a schematic timing diagram of each control pulse supplied to the sensor 100 from D.

Other pulses will be explained with reference to the horizontal blacking pulse HBLK shown in (A). (B) (φH-RF) and (C) (φU-RF) are supplied to the shift register 52 and the terminal 149, respectively. With refresh pulses, these pulses are supplied during the homo-blanking period and transfer the charge stored in the base of the sensor and each vertical line to the transistors line by line.
The 0th order pulse (D) (φHS) refreshed to ground via 50, 50', 50'' is the shift pulse of the horizontal shift register 39, and (F) (φVS) is the shift pulse of the vertical shift register 32. (E) (φHS-
RF) is a bit refresh pulse supplied to terminals 43.54.

Among the above pulses, the refresh pulses (B) and (C) are related to the selection of each mode for reading sensor information in a destructive or non-destructive manner.In other words, if the refresh pulse is stopped, the non-destructive readout mode becomes.

Therefore, in the system system SYS, the clock generator CKG
and driver CKD, and can freely select video recording or still image recording. During destructive readout, pulses φI (-RF, φV) are generated every horizontal blanking period as shown in FIG.
-RF refreshes the information in the row immediately after reading is completed, and during non-destructive reading, φH-RF, φV-RF
By not supplying the same row signal, it is possible to read out the same row signal twice in 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 line information is read out from the sensor 100 between three lines.

Since the structure of the sensor 100 is simply changed from the two-line readout shown in FIG. 2 to the three-line readout, the details will be omitted. In odd fields, line information nl, n2 . n3 to 01 line, n
3. n4. Line 02 is formed from n5. In this case, when shooting a movie, the information on odd-numbered lines is read out non-destructively.

Next, for even fields, the combination of row information reading is changed. That is, n2. n3. n4 to e1 line, n4. n5
．． An e2 line is formed from n6.

At this time, in the movie mode, information on even-numbered lines is read out non-destructively, and in the still mode, information on all lines is read out non-destructively.

Therefore, in the odd field in movie mode and still mode, only the topmost line (odd line information) in Figure 6 is output out of the three line information that makes up each line 01, 02, 03, @fist. descend.

Similarly, for the even field in the movie mode, the topmost line (even line information) of the three line information forming each line el, e2, e3, etc. in FIG.
only the output decreases.

On the other hand, in still mode, each line el, e2 . Of the 3-tree row information that makes up e3..., the top two row information will be read for the third time and the output will drop, while the bottom one row information will be read for the second time and the output will decrease. It can be seen that the rate of decline is small.

Next, FIG. 7 is a signal processing block diagram of the sixth embodiment shown in FIG. 7. This embodiment is obtained by adding the following processing circuit to the first embodiment shown in FIG.

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

That is, the output lines of each row of n1 to n7 shown in FIG. 6 are, for example, nl, n4. n7... is the first output terminal x1
are structurally connected to n2゜n5. n8... are connected to the second output terminal X2, and n3, n6
, n9s-kai are connected to the third output terminal X3.

On the other hand, when the multiplexer 101 controls the readout of the sensor 100 to form the horizontal line output 01 of an odd field, xl is used.

Connect x2 and x3 to X4, X5 and X6 respectively, and
2 when forming x3. xi, x2 respectively x4,
When connecting x5 and x6 to form 03, x2.
x3. xi respectively x4. Connect to x5 and x6. Thereafter, the connections between x1-X3 and x4-x5 are switched for each horizontal line in the same way.

Also, when forming an even field el, the multiplexer 101 converts x2, x3, xl into x4, respectively.
, x5 and x6, and when forming e2, x
i, x2. x3 respectively x4. x5, connect to x6, e
When forming 3 x3. xi.

x2 respectively x4. x5. Connect to x6.

Also, as mentioned above, when forming each horizontal line in both movie and still modes, only one of the three line outputs will always have a different level from the other two outputs.
Signal gain adjuster 20 for adjusting the signal level at that time
0.300 is set. That is, in the case of movie mode, as mentioned above, even in an odd field, the output of the first output of the three outputs in FIG. 6, that is, the output of output line x4 in FIG. Gain adjuster 2
00, the output of x4 is adjusted to the output level of x5 and x6.

On the other hand, in still mode, compared to the outputs of x4 and x5, the output level of the lowest x6 output is higher than that of x4 and x5, so the signal gain adjuster 300 for gain down is used to reduce the output of x6 to x4. I will match it with the output of x5.

For this purpose, the system controller SYS controls the switch 400 to connect a to C in the movie mode and connect b to c in the still mode.

Next, signal gain adjusters 210, 220, and 230 are used to increase the gain and adjust the deterioration of the signal level in the even field in the still mode. That is, as shown in FIG. 6, in the even field of the still mode, the third or second readout is performed, so the signal level decreases greatly, and therefore the flicker is very noticeable. Since the output of x4 and x5 is adjusted to the third readout level, there is a large output difference between odd and even fields in still mode. Since it is removed, the resulting image is of high quality. The switch 450 is a selection switch to which e-f is connected when shooting a movie, and d-f is connected when shooting stills. As described above, we were able to solve the flicker problem that is a problem when adopting a 3-wire output system, and further demonstrate the effect of improving the horizontal Φ vertical resolution and reducing false color signals of the 3-wire output system.

Next, a third embodiment of the present invention will be described below.

FIG. 8 is a simplified embodiment diagram of the signal gain adjusters 210, 220, and 230. In other words, the flicker is good [j Since it is the luminance signal Y that stands, after forming the luminance signal Y by combining the outputs x4' to x6' of 311a or dot-sequentializing the 3-wire output,
The signal level is adjusted by a signal gain adjuster 210'. Like the switch 450, SW3 is connected to e in the movie mode and connected to d in the still mode. Another method for forming a luminance signal is that in the case of double-wire output, one of the two signals may be configured to be an output corresponding to a green filter, and this output may be used as a low-band luminance signal. In this case, it is sufficient to insert a signal gain adjuster only in the signal line that forms the low-band luminance signal.

Next, FIG. 9 shows a fourth embodiment in which the signal level is adjusted after processing the sensor output signal. The r4 degree signal Y is sent to the signal gain adjuster 210'' before the magnetic recording circuit 800.
Level adjustment is performed by.

Further, in order to reduce the number of signal gain adjusters, the color difference signals are line-sequentialized in a color difference line sequential signal forming circuit 800' and then level-adjusted by a signal gain adjuster 300'.
4. SW5 is on the a side in still mode, and on the b side in movie mode.
It is a switch that leads to the side. Through this processing, it is possible to remove the flicker component of the luminance signal caused by non-destructive readout, as well as color signal deviation, white balance deviation, and color flicker.

When non-destructive readout is performed multiple times as described above, the signal level is adjusted according to the number of readouts, so a book that eliminates luminance component flicker, color component shift, white balance shift, and color flicker is created. We were able to take full advantage of the features of the non-destructive sensor.

Also, since it is possible to switch between non-destructive readout mode and destructive readout mode, it is possible to select between moving images and still images depending on the shooting purpose. Furthermore, it is now possible to check the stillness and shooting before recording images without flickering.

〔effect〕

According to the present invention, it is possible to switch between destructive readout and non-destructive readout in movie mode and still mode, for example, so there is no need for a particularly large number of pixels for still mode. Can be used differently to prevent flickering. Furthermore, when the subject is moving still above, the destructive readout mode can be used, and in that case flicker between fields is also less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a side view of the configuration of the imaging device, FIG. 2 is a diagram showing a method of driving the imaging device by a control means, FIG. 3 is an example diagram of a photoelectric conversion element suitable for the imaging device of FIG. 1, and FIG. 5 is a timing diagram of the movie and still modes, FIG. 5 is a sensor drive timing diagram of the embodiment of FIG. 4, and FIG. 6 is a diagram of the third and fourth embodiments of the second embodiment of the present invention. 100 is a sensor, 200, 300, 210° 220.
230 is a signal gain adjuster, SWl, SW3, SW4
, SW5.400.450 is the changeover switch, SYS is the system controller, CKG is the clock generator, CK
D is a clock driver. Odd even Tora 4 solid moohi aσs + 3 moopi υoM
even (24+i, 1TS
mouth η wq country

Claims (2)

[Claims] (1) It has an image sensor composed of a plurality of photoelectric conversion cells that can be read out non-destructively, and a read-out mode switching means that switches the read-out mode between a destructive read-out mode and a non-destructive read-out mode when reading out signals formed by the image sensor. Imaging device. (2) The imaging apparatus according to claim (1), wherein the readout mode switching means switches the readout mode to a destructive readout mode during movie shooting and to a nondestructive readout mode during still shooting.