JPS5824289A - Color television camera device using solid-state image pickup device - Google Patents

Abstract

PURPOSE:To read the charges out of horizontal photodiodes simultaneously, and to increase the sensitivity of a solid-state color TV camera, by generating plural clock pulses for driving vertical shift registers during horizontal blanking periods of a video signal. CONSTITUTION:An MOS type image pickup device uses numbers of arrays of photodiodes 1 in a matrix state, and a horizontal shift register 2, a vertical shift register 3, and horizontal and vertical changeover switches 41-4n, and 51-5m are used to read signals stored in the diodes 1 in precise order. At this time, start pulses syncyronizing with a vertical synchronizing pulses are applied to the register 3 and transferred successively by two-phase vertical driving pulses which synchronize with a horizontal synchronizing signal. By the output of the register 3, the switches 51-5m select horizontal lines in precise order and the output of the register 2 driven by driving pulses which synchronize with the horizontal synchronizing signal opens and close the switches 41-4n successively to read charges out of the diodes 1 simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television camera device using a semiconductor photodetector.

In recent years, solid-state imaging devices, that is, two-dimensional semiconductor photodetecting devices, have been actively developed.

Solid-state imaging devices include those that have MO8 field effect transistors as components, and CCD (Charge Coupled) devices.
Device ) or BBD (BuckatBr
In some devices, the photodetector section is composed of a PN junction photodiode, an MO8O8 type diode, etc.

Here, a solid-state imaging device using a photodiode and an MO8 field effect transistor will be explained as an example.

FIG. 1 is a diagram showing the operating principle of the MO8 type imaging device. That is, a large number of photodiodes 1, which are photosensitive elements, are arranged in a matrix, and a horizontal shift register 2, a vertical shift register 3, and horizontal changeover switches 41 and 42 are used to sequentially read out signals accumulated in the photodiodes.
．． ...4ne vertical changeover switch 51.52. ...5
m is provided.

As is well known, the horizontal shift register 2 is synchronized with a horizontal synchronizing signal, is driven by a start pulse, a horizontal clock pulse, and switches 41, 42, . . . 4n are sequentially opened and opened so that all switches are operated within one horizontal scanning time. On the other hand, the vertical shift register 3 uses a start pulse synchronized with the vertical synchronization signal and a clock pulse synchronized with the horizontal synchronization signal! The switches 51, 52°, . . . , 5m are sequentially opened and opened, and all switches are operated within one vertical scanning time. By operating these two switches, the charge stored in the photodiode is sequentially supplied to a load circuit composed of a resistor 6 and a power source 7, and is taken out as a voltage signal.

FIG. 2 shows a conventional example of configuring a color camera using the above solid-state imaging device.

This includes a reflector 11 that reflects only a certain light that has passed through a lens 8 for adjusting the weight of the subject and a field lens 9 for correcting the focal length, various color correction filters 12, a relay lens 13, etc. A three-color light separation optical system 10 consisting of red (R), green (G), and blue (B)
Separates into colored light and captures each color using three solid-state imaging devices 14TL
, 14G, and 14B to convert it into an electrical signal, and amplify it using amplifiers tsFL115() and 15B. Furthermore, these signals are waveform-shaped by a process amplifier 16R116G116B and converted into an NTSC color television signal by an NTSC encoder.

Solid-state imaging devices make color camera devices more compact and lightweight, and enable image reproduction without screen distortion, burn-in, or afterimages. However, the photodiode, which is the light detection part of a solid-state imaging device, has a sensitivity to each wavelength of light, that is, a spectral sensitivity of 3
The characteristics are shown at longer wavelengths as shown in the figure. Therefore, the sensitivity to R is low, but the sensitivity to B is low. Moreover, the characteristics of the output current with respect to the amount of incident light of the photodiode are
As shown in the figure, it has a saturated region.

Therefore, if the color television camera shown in FIG. 2 is constructed using the solid-state inertia device described above, the following drawbacks will occur.

In other words, when light with equal energy distribution in the visible light region is incident on the color television camera device shown in Fig. 2, the three output currents obtained from the solid-state imaging device corresponding to R, G, and B are the third output currents.
It is proportional to the area surrounded by curves 18R, 118G, and 18B shown in FIG. 6, which is the product of the spectral sensitivity shown in the figure and the spectral characteristics of the NTSC three-color separation optical filter shown in FIG. 5 by one. As a result, a difference occurs in the three output current values, FL,
The signal output decreases in the order of G and H. Normally, in color TV cameras, these three
The two outputs are each amplified by linear amplifiers with different amplification factors, and the levels of R() and B are adjusted to be the same.

However, as the amount of light incident on the color TV camera is gradually increased, the effect of the saturation characteristic of the output current shown in Figure 4 becomes R.
, G, and B will appear in that order. For example, if only R is affected by the above saturation characteristic, a nonlinear circuit is inserted only in the R signal, and the color balance of R, G, and B is lost.

In order to eliminate the above-mentioned drawbacks, it is sufficient to make the output current characteristics of the three solid-state imaging devices consistent with respect to changes in the amount of light incident on the camera device, and as shown in Figure 7, all-color light attenuation filters are installed in the R and B optical paths. 19R and 19B may be inserted to uniformly attenuate R and B light.

However, this method does nothing but reduce the sensitivity of the camera, and does not fundamentally solve the problem.

As is well known, the human eye has high resolution in the G system and low resolution in the B system. For this reason, even in the NTSC color television system, the B-system signal only transmits 500 KL (Z video band).

Therefore, even in a color television camera using a solid-state image pickup plate, the resolution of B is R-? Even if the resolution is about half that of G, the image quality will not deteriorate at all.

By changing the driving method of the B imaging device of a color TV Chiron camera using a solid-state imaging device, the present invention reads out the charges accumulated in the photodiodes of multiple horizontal lines at the same time, and converts the output of the B signal into a and provides a way to increase the sensitivity of solid-state color television cameras.

The gist of the present invention will be explained in detail below using Examples.

The normal driving method for the solid-state imaging device shown in Fig. 1 is as shown in Fig. 8.
is applied to the vertical shift register, and sequentially transmitted with two-phase vertical drive pulses (b) synchronized with the horizontal synchronizing signal, and the output pulse P of the shift register is applied to the switch 51.5.
2. ... By opening and opening 5m, the horizontal lines are selected in an orderly manner, and the switches 41 and 42 are activated by the output of the horizontal shift register driven by the start pulse synchronized with the horizontal synchronization signal and the horizontal opening and output pulses. ．．・・・
・The vertical line is selected by sequentially closing and opening 4n.

At this time, the phase of the vertical drive pulse (b) is set so that it is inserted into the horizontal blanking period of the video signal.
This prevents the horizontal line switching nozzle from appearing on the screen.

In contrast, the present invention is characterized in that the drive pulse for the vertical shift register of the B camera plate is generated multiple times within the horizontal planking period of the video signal.

Here, as shown in FIG. 8(E), a case will be described using an example in which the drive pulse for the vertical shift register is generated twice.

When such a driving method is implemented, the output pulses shown in FIG. 8 can be obtained from the vertical shift register.As a result,
The horizontal line of the solid-state imaging device is switched twice during horizontal blanking of the video signal every two horizontal scans. That is, the horizontal line switches 51 and 52 of the imaging device in FIG.
are closed and opened sequentially during a certain horizontal blanking period, then switches 53 and 54 are turned on during the horizontal blanking period after two horizontal scanning periods, and switch 5 is turned on after two horizontal scanning periods.
5 and 56 will be closed and opened in sequence.

On the other hand, it is known that the equivalent circuit of the signal reading system of the photosensitive plate shown in FIG. The signal is read out to the outside by closing the horizontal line switch 21 (Sl) and the vertical line switch 22 (S2). However, there is a parasitic capacitance 23 (C2) in the vertical line and a parasitic capacitance 24 (C2) in the horizontal readout line, and the on-resistance 24 (C2) exists in each switch MOS transistor.
5 (R1) and 26 (R2) exist.

When reading a signal, S is first closed by the output of the vertical shift register, and the charge stored in C1 is transferred to 02. Normally, in a two-dimensional solid-state imaging device, C3< is C2, and the charge Q3 of C2 when S is closed is expressed by the first equation, so almost all the charge of C1 is accumulated in C1, Q, :C1. Let's move on to the amount of charge. After that, 82 is closed by the output of the horizontal shift register and the signal stored in C2 is pulled out to the outside.As described above, the driving method of the present invention is to change the line switch twice during horizontal blanking every two horizontal scanning periods. When used, C2 in FIG. 9 accumulates the charges of two vertically aligned photodiodes. Accordingly, as shown in FIG. 10(b), the video signal to be read out is twice as large as that obtained by the conventional readout method (FIG. 10(a)) in one horizontal scan. When this signal is reproduced by repeating the same signal twice in a circuit consisting of a horizontal scanning time delay line 28 and an adder circuit 29 as shown in FIG. output signal can be obtained.

In the above description, a method of simultaneously reading out signals on two horizontal lines was used as an example, but it goes without saying that signals on a plurality of horizontal lines may be read out in a similar manner.

As described above, the color television of the present invention is constructed by changing the driving method of the vertical shift register of the solid-state imaging device 14B of B in the color television camera device of FIG. The adventure camera device is
The blue output signal can be doubled without improving the solid-state imaging device, and the signal-to-noise ratio of the solid-state color camera can be increased, so the effect is great.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of a solid-state imaging device, Figure 2 is a diagram showing a color camera using three imaging devices, Figure 3 is a diagram showing an example of the spectral sensitivity of a solid-state imaging device, and Figure 4 is a diagram of a photodiode. A diagram showing the output current characteristics. Figure 5 is a diagram showing an example of the ideal three-color separation characteristics of the NTSC system. Figure 6 is a diagram showing the three colors of a solid-state photographic device when using the three primary color filters of the NTSC system. FIG. 7 is a diagram showing an example of a method for correcting the sensitivity of three photographic devices; FIG. 8 is a diagram showing driving waveforms of the solid-state photographic device; FIG. 9 is a diagram showing an example of the decomposition characteristics. FIG. 10 is a circuit diagram of a signal readout system of a solid-state imaging device, FIG. 10 is a waveform diagram of a video signal obtained from the solid-state imaging device, and FIG. 11 is a diagram showing a demodulation circuit for a green signal. No. 212 No. 4 Amount of light incident on the box LJ jυυ 6υυ V No. 93 Continuation of page 1 of Figure 1O ' 0 Author Takamitsu Kamiyama 1-280 Higashi Koigakubo, Kokubunji City Hitachi, Ltd. Inside the manufacturing center laboratory

Claims (1)

[Claims] t. In a solid-state imaging plate equipped with a vertical shift register driven by a plurality of clock pulses, the plurality of clock pulses for driving the vertical shift register are generated within a horizontal blanking period of a video signal. A color television camera device using a solid-state imaging device characterized by: