JPS5827618B2 - Image tube face plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a face plate of an image pickup tube having electrodes separated for each color, and a dark current correction method for the face plate of the image pickup tube.

FIG. 1 shows the basic configuration of a face plate portion of a well-known three-electrode separated color image pickup tube and a color television camera connected thereto.

Striped color filters IR and IG that transmit red, green, and blue light, respectively.

1B and corresponding transparent signal electrodes 2R, 2G, 2B separated into stripes, for example, 200 to 300
There are many sets.

The signal electrodes 2R, 2G, and 2B are bus bars 3R for each color.

Wired with 3G and 3B.

Further, a photoconductor layer 4 is arranged in contact with the signal electrode.

An image pickup tube having such a face plate is designated as 5.

Buspers 3R, 3G, and 3B of the image pickup tube 5 have preamplifiers 6R and 6G.

6B is connected to amplify the signal current obtained from each signal electrode.

Furthermore, these signals are processed by process amplifiers 7R, 7G, and 7B.
and converted into an NTSC color television signal by an NTSC encoder 8.

When an image of, for example, a white object is captured using the color image pickup tube, the three output currents IR, I(), and IB corresponding to red, green, and blue obtained from the image pickup tube are expressed by the first equation, the second equation, and the third equation. It can be shown by the formula.

However, id is a current component that is not involved in optical information at all, and will hereinafter be referred to as dark current.

Furthermore, lR1jg+jB is a signal component corresponding to red, green, and blue light.

in general! R, t iot j B show different values even when the signal electrode voltages (hereinafter referred to as target voltages) of each channel are equal.

This is caused by the spectral characteristics of the photoconductor and lens, the color temperature of the illumination, the characteristics of the color separation filter, etc.

In a color television camera, it is necessary to maintain white balance, and I Rr I Q r I B shown in equations (1), (2), and (3) are each amplified by an amplifier with an amplification factor. , the levels of the three signals must be the same.

Therefore, equations (1), (2), and (3) can be expressed as the fourth, fifth, and sixth equations when white balance is taken.

When the above-mentioned image pickup tube is operated under illumination by an incandescent bulb,
In general, IB has a much smaller value than 1G and 1R.

Therefore, among Id, ld, and ldan in the second term on the right side of equations (4), (5), and (6), 4 and 4 are the other 2I R,
IQ: 113 1 This is a larger value than that of Person B.

Usually 1d, ld, ld are the well-known times IRJG shown in Figure 2.
After fixing the level of the horizontal synchronization part of the video signal in the IB circuit, that is, the pedestal level insertion circuit consisting of the DC level clamp circuit 9, the blanking pulse insertion circuit 10, and the DC clip circuit 11, and inserting the blanking pulse, the excess When aligning the blanking pulses, they are absorbed by the DC component δ, as shown in FIG.

FIG. 3 shows an example of a video waveform after passing through the circuit of FIG.

In the figure, α indicates the dark current component after white balance,
β is a constant that can be given an arbitrary value by selecting the clamp level and clip level.

However, the dark current ld has a large variation with respect to temperature, and its value increases as the temperature rises.

Therefore, the balance of the three dark currents after white balance is taken is lost.

In particular, the DC level of the blue channel, which actually has the most dark current components, rises higher than other signals as the temperature rises.
This disturbs the color balance of the reproduced image.

As a means to solve the problem described in L, as shown in FIG. 4, a light shielding part shown by diagonal lines is provided in a part of the image forming part 12 of the image pickup tube face plate, so that the light does not enter the photoconductor layer corresponding to the light shielding part. There are ways to block the light.

When this method is used, a black level b is inserted into the output video signal obtained by electron beam scanning after a blanking period a during which the beam does not flow, as shown in FIG.

Since this black level indicates the dark current value itself, by fixing this level with a DC clamp circuit and cutting off components below black I/bell, it is possible to obtain a video signal that is not affected by dark current.

One of the means for setting the above-mentioned black l/bell is the method shown in FIG.

That is, the striped color separation filter 1R is arranged in contact with the glass substrate 14.

A light shielding part 17 is provided adjacent to the IG and IB on the same plane, and a photoconductor layer 16 is arranged in contact with the striped transparent electrodes 2R, 2G, 2B with a glass layer 15 laminated therebetween. .

On the other hand, in the electrode separated type imaging face plate shown in FIG.
Signal crosstalk occurs due to the capacitance that exists between each electrode.

This crosstalk can be reduced by reducing the interelectrode capacitance and by reducing the number of electrodes divided into stripes.

However, since the resolving power of the image pickup tube is proportional to the number of striped electrodes, it is better not to reduce it as much as possible.

Therefore, it may be possible to reduce the number of stripes in the portion that does not affect the resolution, that is, the light shielding portion, to reduce the interelectrode capacitance, and this is also the first objective of the present invention.

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

FIG. 7 shows a part of a sectional view of the image pickup tube face plate of the present invention.

A color separation filter consisting of stripe-shaped color separation filters IR, IG, and IB arranged adjacent to the glass substrate 14 and a light shielding part 17 provided on the same plane is arranged via a zigzag laminated glass layer 15. Striped transparent signal electrodes 2R, 202B and signal electrodes 2R, 2G, 2B
Black level detection electrodes 18R, 18 with wider stripe width
G.

18B1 and a photoconductor 16 placed in contact with these electrodes.

In the image pickup tube face plate of the present invention shown in FIG. 7, by reducing the number of black level detection electrodes, the stripe width of each black level detection electrode is made wider than the width of the signal detection electrode.
, 18G, and 18B, black level detection can be performed without substantially increasing the capacitance between each signal electrode.

The embodiment shown in FIG. 7 is a case where the light shielding part is arranged on the same plane as the striped color separation filter, but the light shielding part 17 may be arranged on the glass substrate 14 as shown in FIG. , as shown in FIG. 9, striped color filters IR, IG, and IB arranged in contact with the substrate glass 14, a light blocking layer 17, and striped transparent electrodes 2R, 2G, and 2B.
And another glass substrate 19 having black level detection electrodes 18R, 18G, and 18B arranged on both sides thereof may be bonded together using, for example, an epoxy adhesive 20 or the like.

Further, as shown in FIG. 10, a glass substrate 14 and striped color separation filters IR and IG.

1B, a laminated glass layer 15, striped transparent electrodes 2R, 2G, 2B, and a black level detection electrode 18R.
, 18G, 18B, and the photoconductor layer 16, the black level detection electrodes 18R, 18G, and 18B of the image pickup tube face plate may be formed of an opaque material such as metallic chromium, for example, to achieve the object of the present invention.

A second object of the present invention is to provide a method for reducing only the dark current component of an output signal from an image pickup tube equipped with a black level detection electrode having a wider stripe width than a striped signal electrode.

As described above, in the image pickup tube face plate of the present invention, the width of the black level detection current is wider than the stripe width of the signal electrodes, and the density of the black level detection electrodes per unit area is greater than the density of the signal electrodes.

Therefore, as shown in FIG. 11, a difference occurs between the dark current C taken from the black level detection electrode and the dark current d taken from the signal electrode, and the absolute value of this difference increases with temperature.

Therefore, color balance cannot be corrected simply by fixing the black level and cutting out components below the black level.

Now, if the density of the black level detection electrode and the density of the u11B detection electrode are V, then the ratio of the dark current obtained from both electrodes is -
It is indicated by.

Therefore, the dark current obtained from the black level electrode can be multiplied by one and used to eliminate the dark current obtained from the signal electrode.

FIG. 12 shows one embodiment of the present invention.

A horizontal synchronization clamp circuit 21 fixes the level of the video signal during the horizontal synchronization period.

A part of the signal is sent to the black level detection and sample hold circuit 23, where it is sampled and held by the output pulse of the circuit 22 which delays the horizontal synchronizing signal and shapes the waveform, and generates a DC black level signal corresponding to the dark current of the light shielding part. Detect.

This DC level is multiplied by a voltage divider circuit 24, a difference with the signal whose DC level is fixed by a DC clamp circuit 21 is created by a differential amplifier 25, a signal below a certain level is deleted by a clip circuit 26, Obtains a signal without dark current component.

The above embodiment is a method of obtaining a difference signal between the detected DC level intervening signal of the light shielding part and a signal with a fixed DC level. It goes without saying that other circuit systems may be used as long as the dark current component contained in the video signal is removed.

As described above, there is a method for removing the dark current component contained in the video signal using the image pickup tube face plate of the present invention and the video signal obtained from the image pickup tube equipped with the face plate of the present invention, without substantially increasing the interelectrode capacitance. , the effect is great because it can correct the shift in color balance due to temperature rise.

[Brief explanation of drawings]

Figure 1 shows the basic configuration of the face plate of a conventional color image pickup tube and a color television camera connected to it, Figure 2 shows the pedestal level insertion circuit, Figure 3 shows the pedestal level insertion waveform, and Figure 4 shows the light shielding. 5 shows a black level insertion waveform, FIG. 6 shows an image pickup surface plate equipped with a conventional black level detection section, and FIGS. 7, 8, and 9
10 shows the image pickup tube face plate of the present invention, FIG. 11 shows the dark current waveforms of the light shielding section and the light detecting section, and FIG. 12 shows the dark current eliminating circuit of the present invention. IR, IG, IB varnish drive-like color filter, 2R, 2
G, 2B varnish drive-like signal electrode, 3R. 3G, 3B: Buspar 4: Photoconductive layer, 5: Image pickup tube, 6
R, 6G, 6B: Preamplifier, 7R, 7G. 7 B: 7' process amplifier, 8: Enloader, 9:
DC clamp circuit, 10 blanking pulse insertion circuit, 11: Clip circuit, 12: Object imaging section, 13:
Light shielding part, 14, 15 Ni glass, 16: Photoconductor, 17
: Light blocking filter, 18R918G, 18B: Black level detection electrode, 19 Ni glass, 20: Adhesive, 21: Clamp circuit, 22: Delay circuit, 23: Black level detection and sample hold circuit, 24: Voltage division circuit, 25: Differential amplifier, 26: clip circuit.

Claims (1)

[Scope of Claims] 1. A large number of striped signal electrodes that output signal currents corresponding to colored lights, and a striped color filter that is provided corresponding to at least a part of the striped signal electrodes and that passes different colored lights. , an image pickup tube face plate comprising a busper for extracting signal current from the striped signal electrodes for each color light, comprising a light shielding part for shielding the colored lights of the plurality of striped signal electrodes, the light shielding part having a An imaging tube face plate characterized in that the stripe widths of the plurality of corresponding stripe-shaped signal electrodes are configured to be wider than the stripe widths of other stripe-shaped signal electrodes. 2. In the image pickup tube face plate according to claim 1,
An image pickup tube face plate, wherein the light shielding portion is obtained by forming a plurality of the striped signal electrodes with an opaque material. 3. A large number of striped signal electrodes that output signal currents according to colored lights, striped color filters that are provided corresponding to at least a part of the striped signal electrodes and that pass different colored lights, and An image pickup tube face plate including a buzz bar for extracting the beam current from the signal electrode for each color light; and a light shielding part for shielding the colored light of the plurality of striped signal electrodes, the light shielding part The stripe width of the plurality of striped signal electrodes corresponding to the above is configured to be wider than the stripe width of the other striped signal electrodes, and the density (U) of the plurality of striped signal electrodes corresponding to the light shielding portion is The signal current is controlled by a signal obtained by multiplying the dark current obtained from the plurality of striped signal electrodes corresponding to the light shielding part by the ratio (U/V) of the density (V) of the other striped signal electrodes. An image pickup tube face plate comprising a correction circuit.