JPS58219873A - Solid-state television camera device - Google Patents

Abstract

PURPOSE:To operate a camera only in a range where vertical smear compensation is sufficiently performed and video signals of the high quality are obtained, by providing the titled device with a means to display an alarm when a vertical smear component exceeds a prescribed value. CONSTITUTION:A video signal read out from a solid-state image pickup element 1 is supplied to a vertical smear compensating circuit 9. An adder/substractor 3 adds or subtracts a compensated signal from the smear compensating circuit 9 to/from the video signal and impresses the calculated results to an output terminal 11 and a view finder 10 through a video processing circuit 4. The smear compensating circuit 9 is provided with an AD converter 6, a digital memory 7, a DA converter 8, and a level detecting circuit 12. The level detecting circuit 12 supervises the vertical smear component, and when the component exceeds the prescribed value, actuates an alarm display device 13 in the view finder 10. Consequently, the camera can be operated only in the range where the smear is sufficiently compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid state television camera with vertical smear correction.

Solid-state imaging devices use an electron beam to scan the charge conversion portion corresponding to each pixel and read out image signals using a switching element. Moreover, since it produces less deflection distortion, it has come to be widely used in television cameras and the like as semiconductor technology has progressed.

An example of such a solid-state imaging device is shown in FIG. 16.

In the figure, H8 is a horizontal shift register, VS is a vertical shift register, S, 1. S2. S3. S4...
... is a horizontal MOS switch, 811. S1'2
......, S21,822...

831.832... is a vertical MOS switch,
PTII.

PT12..., PT21. PT22...
・, PT31. PrB6... is a photodiode,
Hl, H2, H3, H4... are horizontal signal readout lines,
VGI, VO2, VO2, VO2, . . . are vertical gate lines, and OUT is a video signal output line. In addition.

C1l, CI2. ..., C21, C22...
..., C31, C32... are the parasitic capacitance of the vertical MOS switch, CHI, CH2゜CH3, CH4...
... is the parasitic capacitance of the horizontal signal readout line.

Next, the operation will be explained.

The horizontal shift register H8 uses a horizontal synchronizing pulse as a start signal, and is clocked at a frequency such that a number of pulses equal to the number of pixels in the horizontal direction (same as the number of horizontal signal readout lines H1) appear within the horizontal period. works, horizontal M
OS switch s1...Sequentially turn on songs.

On the other hand, the vertical shift register vs operates using the vertical drive pulse as a start signal and the horizontal synchronizing pulse as a clock, and sequentially generates gate signals on the vertical gate lines VG1... for each vertical gate line. vertical MOS
Sui7fS11. S21. S31...,SI
2°S22. S32・, S13. S23,833-・
. . - are turned on sequentially every horizontal scanning period.

Therefore, now, from the vertical shift register Vs to the vertical game)
Assume that a signal appears at 111RVGI.

Then, the vertical MOS switches Sll, S21 . S31...
... turns on, and each photodiode PTI
I.

PT21. The pixel signals stored in PT31... are transferred to the corresponding horizontal signal readout lines H1, H2, n3...
... is read out.

The respective parasitic capacitances CH1, cH2, CH3... are transferred to the song and accumulated there.

Subsequently, the horizontal MOS switches Sl, S2, S2, 83... songs are turned on sequentially by signals from the horizontal shift register H8, so the horizontal signal readout lines H1, H2, H3...
Parasitic capacitance CHI, CH2, CH3・'・・・・
Each pixel signal accumulated in
Taken out by T.

Hereafter, this operation is sequentially performed as a vertical game) Line VG 2. V.O.
2... is repeated, and a video signal is obtained on the signal output line OUT.

By the way, in such a well-known solid-state image sensor,
There is a phenomenon called vertical smear that generates a false signal and deteriorates the image quality. That is, in such a solid-state image sensor, an inter-switch parasitic capacitance C1l exists unavoidably in each vertical MOS switch 811, . Vertical MQs switches other than the same horizontal signal readout line 2, for example, vertical MOS switches connected to the old one, for example 812.
Parasitic capacitance c12°C10... of S13...
12. Photodiode PT via... PT13
... leaks to the water signal readout line H, 1, and is mixed into the pixel signal read out from the photodiode p'rii. Further, such a solid-state image sensor is usually manufactured from a single St substrate using semiconductor technology, and for this reason, the horizontal signal readout line H1...
・It may also generate spurious signals by sensing light.
These causes vertical smear.

As a result 1, for example, when an image of a subject as shown in Figure 2 (a) is captured, an image as shown in Figure 2 (b) is reproduced, and the bright part A of the subject appears to be leaking in the vertical direction. This results in a portion C. That is.

The dark part in the same figure (a) is the same figure (b) in the reproduced image.
The image is divided into a dark part B and a brighter part C.

In order to correct this vertical smear, a solid-state television camera equipped with a vertical smear correction circuit as shown in FIG. 3 has heretofore been known.

In FIG. 3, 1 is a solid-state image sensor, 2 is a preamplifier, 3 is an addition/subtraction circuit, 4 is a video signal processing circuit, 5 is an amplifier, 6 is an A/D (analog-to-digital converter), and 7
8 is a digital memory, 8 is a D/A (digital/analog converter), 9 is a vertical smear correction circuit, IOA viewfinder, and 11 is an output terminal.

The solid-state image sensor 1 is the same as the image sensor shown in FIG. 1, and generates a video signal by photoelectrically converting a subject image formed by an optical system such as a lens.

The preamplifier 2 functions to amplify the video signal from the solid-state image sensor 1 to a predetermined level while maintaining a predetermined S/N ratio.

The addition/subtraction circuit 3 functions to add or subtract the correction signal from the vertical smear correction circuit 9 to the video signal from the preamplifier 2.

The video signal processing circuit 4 performs necessary processing such as setting vertical and horizontal blanking periods and setting a clamp level, and supplies the video signal to the output terminal 11.

The vertical smear correction circuit 9 operates during one horizontal scanning period when only the horizontal MOS switch S1 is turned off during the vertical retrace period when all of the vertical MOS switches Sll of the solid-state image sensor 1 are turned off. The function is to store the signals that are successively output when the signals are turned on sequentially over the period of time, read them out for each horizontal scanning period, and supply them to the addition/subtraction circuit 3 as vertical smear correction signals. A/D
6, predetermined sampling is performed during one horizontal scanning period mentioned above, the signals are digitized, and the signals for one horizontal scanning period are sequentially stored in predetermined addresses of the memory 7. The stored signal is read out repeatedly in each subsequent horizontal scanning period, converted into an analog signal by the D/A 8, and supplied to the addition/subtraction circuit 3.

Therefore, in this solid-state television camera, even if a video signal containing a vertical smear component is read out from the solid-state image sensor l and appears at the output of the preamplifier 2, the correction signal corresponding to the vertical smear component is The correction circuit 9 supplies the signal to the adder/subtracter 3, and the preamplifier 2 also subtracts (or adds) the video signal containing the vertical smear component to the adder/subtracter 3. A video signal from which the smear component is compensated and removed is obtained, and a video signal that does not include vertical smear can be supplied to the output terminal 11.

The video signal supplied from the video processing circuit 4 to the output terminal 11 is also supplied to the viewfinder 10,
It is possible to monitor the video signal of the object being imaged without vertical smear as an image.

Incidentally, the amount of vertical smear in such a solid-state image sensor increases as the amount of incident light increases, as shown in FIG. In addition, in this Fig. 4.

The vertical duty is the ratio of the bright part and the dark part in the vertical direction of the subject image incident on the solid-state image sensor 1, and has a coefficient of 1. All coefficients 2 are unique to solid-state imaging devices.

Therefore, in the camera shown in Fig. 3, sufficient vertical smear correction cannot be performed unless the signal of the vertical smear component of a large level corresponding to Jl is processed as the amount of incident light 111 increases. 〇On the other hand, the A/D 6 of the vertical smear correction circuit 9 is limited in its dynamic range due to the quantization accuracy and the circuit scale that can be implemented as a camera device, and is limited to the maximum amount of incident light expected in practical use. It is almost impossible to use a follow-up A/D due to cost and other reasons.

For this reason, in the above-mentioned conventional solid-state television camera, when the amount of incident light increases, the level of the vertical smear component tends to exceed the dynamic range of the A/D, and as a result, the A/D overflows and the vertical smear correction circuit 9
The vertical smear that exceeds the dynamic range remains in the video signal without being corrected, resulting in a significant drop in image quality.

An object of the present invention is to eliminate the drawbacks of the prior art described above and to obtain a video signal free of vertical smear by not performing imaging operations in areas where vertical smear correction becomes insufficient due to an increase in the amount of incident light. The purpose of the present invention is to provide a solid-state television camera device that can be used in a variety of ways.

In order to achieve this object, the present invention monitors the level of the vertical smear component read out from the solid-state image sensor, and when it reaches a predetermined level, which is the upper limit of the vertical smear correction possible level, the viewfinder field of view is adjusted. The feature is that an alarm is displayed inside the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two embodiments of a solid-state television camera device according to the present invention will be described below with reference to the drawings.

FIG. 5 shows an embodiment of the present invention, and in FIG. 2, 12 is a level detection circuit, and 13 is an alarm display device.

The rest is the same as the conventional example shown in FIG.

The level detection circuit 12 checks the level of a predetermined bit of the upper digit of the A/D 6, and determines that the level of the vertical smear component input thereto has reached a predetermined level before overflowing beyond the dynamic range of the A/D 6. It functions to detect and generate an alarm signal al.

The alarm display device 13 is composed of, for example, a red light emitting diode, and is configured so that its lighting state can be seen together with the monitor image of the image signal within the field of view of the viewfinder 11, and is displayed only when the alarm signal a1 is supplied. It is set to light up.

Therefore, according to this embodiment, the level of the vertical smear component read from the solid-state image sensor 1 is
alarm display device 13 until the detection level is reached.
The light emitting diode does not light up, and during this time, the vertical smear correction circuit 9 supplies a correction signal that accurately corresponds to the vertical smear component from the solid-state image sensor 1 to the addition/subtraction circuit 3, so that the output terminal r-11 can obtain a video signal with excellent image quality that does not include vertical smear.

During imaging operation by this solid-state television camera device, when the level of the vertical smear component from the solid-state image sensor 1 reaches the detection level of the level detection circuit 12 due to an increase in the amount of incident light from the subject, an alarm signal is sent. a1
is this level\from the detection circuit 12 to the alarm display device 13
As a result, an illuminated display appears within the field of view of the viewfinder 10.

Therefore, the operator of this television camera equipment should
By performing operations such as narrowing down the iris of the imaging optical system in accordance with the alarm displayed by the alarm display device 13, it is possible to prevent vertical smear from reaching a level that cannot be corrected. This is effective in preventing inferior video signals from being output.

At this time, the detection level by the level detection circuit 12 is set to a level lower by a predetermined value than the value until the vertical smear component reaches the upper limit of the dynamic range of the A/D 6, as described above.

Even after the alarm is displayed, operations can be carried out with plenty of time, and there is no risk that a video signal with insufficient vertical smear correction will be output during that time.

Note that, of course, this detection level may be set arbitrarily as necessary.

Therefore, according to this embodiment, unless an alarm display is displayed within the field of view of the viewfinder 10, a video signal with vertical smear sufficiently compensated for can be obtained, and even when an alarm display appears, the corresponding operation can be performed. By simply doing this, you can always obtain a high-quality video signal with sufficient vertical smear correction.

In one or more embodiments, the alarm display device 13° performs a lighting display operation using a light emitting diode within the field of view of the viewfinder 10, but instead of this, or in combination with this, an intermittent electronic An acoustic alarm means such as a sound (pronounced as bing, beep, beep, etc.) may also be used.

In addition, the detection level of the vertical smear component by the level detection circuit 12 is set to multiple levels, for example, three levels, and the green light emitting diode lights up as long as there is sufficient margin in the dynamic range of the A/D 6. An orange light emitting diode may be turned on when the object approaches, and a red light emitting diode may be turned on in the overflow area.

As explained above, according to the present invention, it is possible to know in advance, with a simple configuration, that the vertical smear correction operation is approaching the limit at which it cannot be performed satisfactorily. It is possible to provide a low-cost solid-state television camera device in which the camera can be operated only within a range where a video signal with excellent image quality can be obtained through sufficient operation.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a solid-state image sensor, Figures 2 (a) and (b) are illustrations of vertical smear, and Figure 3 is a conventional example of a solid-state television camera with a vertical smear correction circuit. FIG. 4 is a characteristic curve diagram showing the relationship between vertical smear and the amount of incident light, and FIG. 5 is a block diagram showing an embodiment of the solid-state television camera device according to the present invention. ■=solid-state image sensor, 2: preamplifier, 3: addition/subtraction circuit,
4: Video processing circuit, 5: Amplifier. 6: A/D (analog-digital converter). 7: Digital memory, 8: D/A (digital/analog converter), 10: Viewfinder. 12: Two-level detection circuit; 13: Alarm display device.

Claims (1)

[Scope of Claims] A solid-state television camera device equipped with a vertical smear correction function that stores vertical smear components read from a solid-state image sensor in each vertical blanking period and adds or subtracts them to a video signal in each horizontal scanning period. In. Means for monitoring the level of the vertical smear component read from the solid-state image sensor and means for displaying an alarm are provided, and the alarm is displayed when the vertical smear component reaches a predetermined level or higher. A solid-state television camera device.