JPS59158693A - Image pickup device - Google Patents

Abstract

PURPOSE:To drive an image pickup device with less amount of noise superimposition by driving at least two horizontal shift registers among plural horizontal shift registers in opposite phase in an image pickup equipment having the image pickup device. CONSTITUTION:Output signals S1-S3 outputted from an image pickup device CCD10 are formed into signal waveforms S1'-S3' having a width of period close to nearly 100% of the driving pulse period at a sample-and-hold circuit 40, the phase difference among the signals S1', S2' and S3' is maintained as it is, 180 deg., and a point sequential signal S0 is formed at a switch circuit 50. Since at least two register output signals among plural register output signals S1'-S3' are in opposite phase to each other, a luminance signal with broad band is formed without noise invaded to the signal components.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an imaging device υ that drives an imaging device having a plurality of horizontal shift registers in a modified manner.

[Prior art]

Conventionally, this color imaging device uses an imaging device (such as a COD) that includes a plurality of color separation filters having different spectral characteristics in the form of a stripe, for example.

For example, as shown in the first diagram, a red light (R) transmission filter, a green light (G) transmission filter, and a blue light (B) transmission filter (hereinafter simply referred to as an R filter and a G filter).

Let us consider a case where filters (referred to as B filters) are sequentially arranged on the surface of an imaging device. The light that enters the imaging device through such a filter and optical system is spatially sampled by the color stripe filter and imaging device described above, but in this case, the number of picture elements of the imaging device or the pitch of the color stripe filter is sampled spatially. The spatial I'd wavenumber component of the incident light that corresponds to % or more of the spatial sampling frequency determined by is a cause of aliasing distortion. This will be explained using FIG. In each of the diagrams (A), CB), and (C), the horizontal axis represents frequency and the vertical axis represents signal level.

The incident light sampled on the imaging device is read out from the imaging device as an imaging signal by optical conversion, etc., but here, only R (or G) of the imaging signal is read out from the imaging device.
(B only, B only), its repetition frequency becomes the station of the readout frequency. If this iJ i frequency is fc, the baseband component and sideband component of the incident light due to sampling will be as shown in the figure (A), and the shaded part in the figure is called the aliasing distortion component. When this signal is passed through a low-pass filter that has the L characteristics shown in the diagram (B), the new water component mixed with the baseband component remains as 2J<, and this component is displayed on the display. Non'); causes total deterioration of image quality. As a method for reducing such aliasing distortion, a method is described in Japanese Patent Application Laid-Open No. 120281/1981.4 In other words, as shown in FIG. If the color separation filter is designed so that the level of the point 11μ order signal output from the device is 1:1:1, the sideband components cancel each other out and aliasing distortion can be reduced.

According to this method, at least an achromatic screen (';A
Then ii can be reduced from Pr.

Of course, this kind of effect cannot be obtained on screens with high color saturation, but the visual sensitivity for one person is low on the halo side when it comes to colors, but it can be ignored.

[However, in the above case, if the color temperature of the photographing light source differs depending on the purpose of photographing or the scene, the signal level becomes unbalanced one by one, eventually resulting in aliasing distortion. Figure 6 shows a color temperature of, for example, 52,000 (S, 0
The spectral energy at 000K is shown, and FIG. 4 is a diagram showing a drawback when a color separation filter is designed so that the first-order output signal level becomes constant at 5200'K, for example. If the filter is set so that R2O, i-1 is 1:i:1 at a color temperature level of 32
That is, since the R side is weak and the B side is strong, the sideband vector is biased toward the cyan (Cy) side as shown in FIG. 4, and a sweet aliasing distortion occurs.

Historically, imaging devices have generally been highly sensitive to infrared light, which can deviate from the visual sensitivity. However, unevenness in the thickness that occurs during the manufacturing process of this infrared cant filter may cause variations in the spectral sensitivity characteristics of this filter, resulting in fluctuations in the R signal level.

The following method is known as a method for removing the Di defect.

That is, this is a method in which a mechanical color temperature correction filter is used as the first method. This method usually involves preparing color temperature correction filters for daylight, fluorochrome, and tungsten, for example, and
The above-mentioned correction filter is switched depending on the shooting location. The disadvantage of this method is that the correction filter (i
The problem is that aliasing distortion cannot be completely prevented because ``J m M'' is required and the level adjustment of the point-sequential signal is rough.

Also, with conventional imaging devices, the noise is large and the image S, /'M
The problem was that it was bad. For example, Tokuko Sho 55-513
In the television camera using a six-pole image pickup tube described in Japanese Patent No. 95, a high-frequency luminance signal is obtained by adding R, G, and B signals. In other words, the output signals R, (), and B of 3'' drowsiness become as shown in Figure 5, G, and B by scanning the ゛≦child beam, and when each color signal is combined, a luminance signal Y is obtained.In this case, The noise generated in the image pickup tube is generated uniformly in both the signal component region and the invalid component region, so the noise in the synthesized luminance signal becomes approximately V'8- times, or decreases by that amount. In addition, even in an imaging apparatus using a solid-state device as shown in FIG. 6, which will be described later, the following noise problem occurs. For example, Figure 5(B) shows the output signals of each horizontal shift register when six horizontal shift registers are driven by pulses that are in phase with the spatial sampling of the color separation filter. There is peace of mind in holding samples. But the signals si, s2. In s3, the noise of each drive pulse is generated in the part indicated by the arrows (A, B, C) due to the 8-way coupling between each horizontal shift register output amplifier and the drive electrode, and when this noise part is sampled and held, the noise is changed. There is a possibility that noise may occur, so the timing of sample and hold must avoid the above-mentioned noise, and for this purpose very accurate timing is required.

However, when considering the operating temperature of the imaging device and changes over time,
[Purpose] The purpose of the present invention is to eliminate the above-mentioned drawbacks and provide an imaging device R that can drive an imaging device with less noise. It is also true.

〔Example〕

An embodiment of the present invention will be explained by taking as an example an imaging device using a CCD type imaging device shown in FIG.

The image sensor shown in Figure 6 is a frame transfer type COD. Information charges photoelectrically converted by the imaging unit 1 corresponding to each color filter of the stripe filter are driven by a driving pulse φpx.
and φP8, the data is transferred to the memory part 2 at high speed within the vertical retrace period of TV synchronization. In addition, the information charges accumulated in the memory part 2 are divided into horizontal shift registers SR1, 8R2, and SR3 for color information corresponding to each stripe filter for vertical transfer of one horizontal line shown in FIG. It is configured so that Therefore registers SR1, S
R2 and Sl form separation means for separating color signals. 9. FIG. 8 is a block diagram of a signal processing circuit for signals read out from the COD. A Q color filter shown in the first diagram is attached to the surface of the imaging device 10 driven by a driver 20 that generates a pulse based on the clock pulse of the clock pulse 030, and its output signal corresponds to a color separation filter. Each R, G, and B color signal is obtained separately.

In this case, the driving pulse φS of the horizontal shift register SR1
1 and the drive pulse φ82.1 for the horizontal shift registers SR2, SR3. Since the pulse phase is different from φs3 by 180°, the color signal becomes 81, 82°S6 shown in FIG. In the figure, the shaded area indicates the effective signal component. These color signals are sent to the next stage
In the /code circuit 40, a signal waveform has a cycle width close to about 100% of the drive pulse cycle.

stomach. No. 01 is Ir! due to the tumble hold pulse P1 [, and signals S2 and 83 are respectively Ir! due to the sample hold pulse P2. Since I decorate, sample and hold circuit・10
The phase difference between the output of -1 81' and s2' and ss' is maintained at 180 degrees. From these signals, the switch circuit 50 outputs the control bus PV/1,
A point So is formed every month by PW2 and PV/3, but the color signals R, G, and H included in this signal So are
The phase of the color separation filter must match the same sampling phase of the color separation filter. Therefore, switching pulse PW 1
, FW2, PW3 are as shown, namely pulse 1
) Wi is the pulse PV/Wi between approximately the middle WJ of the signal S11
2 and PW3 are placed 1d within the signal period of 821 and 83' every month.
The timing can be determined as you like. Sample hold timing like this.

By controlling the switching timing.

The output So of switch 50, which becomes a luminance signal, is shown in Figure 9. Since each color signal is sequentially converted into eight sufficient spatial frequency components as shown in ()e, high resolution can be obtained.

Since only the part necessary as the distorted luminance signal is removed and re-switched, there is no S/11 deterioration as in the conventional example. Also, as shown above, the plurality of register output signals 81'.

Since the tutee of 821, s61 is 50% and the phases are in a positive or negative phase relationship, noise does not enter the signal component.

Furthermore, since at least two of the plurality of register output signals are in opposite phases to each other, when a luminance signal is generated by dot-sequentializing these register outputs, a wide-band luminance signal that follows all sampling phases can be easily formed. I can do things.

That is, if the outputs of the plurality of registers were all in phase, it would be impossible to form a luminance signal having the spatial sampling phase as described above without a delay means; however, according to the present invention, there is no need to use such a delay means. Furthermore, a wideband signal can be obtained using the switching pulses pw1 to PW3.

Of course, this method can be applied not only to cases where six horizontal shift registers are provided, but also to cases where only two or four or more horizontal shift registers are provided.1. The output signals S4', S2', and 85' of the sample-and-hold circuit 40 are limited by fi+lJ to the necessary signal band components of about I MHz as color signals by the next-stage low-pass filter 60.

Incidentally, the spatial sampling phases (center of the sense lf) of the signals f: t1', 82', and S3' are as shown in FIG. In the figure, solid arrows indicate each phase relationship at the time of output from the sample-and-hold circuit 40, and dashed arrows correspond to spatial sampling of the color separation filter. It shows the ideal phase.

Therefore, signals S1' and 83' are respectively TD
It is necessary to adjust the delay time of L+ and TDL2.

The delay circuit 70 shown in FIG. 8 is for this purpose. Luminance signal Y, color signal R, (), B obtained in this way
includes gamma correction, white clip, black level adjustment circuit,
Process encoder circuit 90 consisting of a chroma modulator etc.
and becomes an NTSC signal.

In the embodiment described above, the output signal of the sample and hold circuit 40 is directly led to the switch circuit 50, but each signal level is controlled at the stage before the switch circuit. By inserting a compensating level matching circuit, the aliasing distortion of the luminance signal can be considerably reduced.

If the driving frequency of the horizontal shift register is high, the delay circuit 70 can be omitted. That is, if the spatial sampling of the color separation filter is, for example, about 141 yiHz, the sampling of each color signal corresponds to about 4.8 iHz, and in the case of the above embodiment, TDL + = =: 35 ns.
, TDL2 == 70 ns, and the color resolution of the color signal is approximately 500 KHz ~ i Mn2. can be almost ignored. Further, instead of providing the delay circuit 70, the cutoff characteristic of the low-pass filter 60 may be slightly modified to obtain the delay characteristic isometrically.

It goes without saying that the delay circuit 70 may be provided in the signal path before the low-pass filter 60.

〔effect〕

As explained above, the following effect can be obtained by driving at least two horizontal shift registers out of a plurality of horizontal shift registers in opposite phases.

First, noise leakage between the horizontal shift register output signals due to the valley ml' coupling of the driving noise is reduced.
There is no modulation noise due to this noise.

Second, by sequentially switching and outputting the outputs of each register, it is possible to perform point sequentialization according to spatial sampling without using a delay circuit when forming a point j-order luminance signal, which simplifies the configuration. Sixthly, the timing of the sample and hold pulse can be set to 4'++ degrees, which is the same as that of a normal pulse.

Also, since the color signal can be generated from a duty of approximately 100% of the driving pulse frequency, it is possible to eliminate low-frequency noise. Furthermore, by creating the S4 degree signal by switching the effective components of each color signal, the yl5hip is improved.

In this example, a pure color tarp color separation filter is used.
Obviously, a complementary color type color separation filter may be used, or it may be constructed using other types of solid-state devices.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a color separation filter, Figure 2 is an illustration of aliasing distortion, Figure 5 is a spectral energy diagram due to differences in imaging light sources, and Figure 4 is an explanation of aliasing distortion due to unbalanced point-sequential signal levels. FIG. 7 is a diagram illustrating transfer of each color signal to a horizontal shift register, and FIG. 8 is a diagram showing an embodiment of the imaging apparatus of the present invention. FIG. 9 is an explanatory diagram of the luminance signal synthesis method in FIG. 8, and FIG. 10 is an explanatory diagram of the sampling phase of the color signal in the embodiment of FIG. 10...Imaging device 40...Sample and hold circuit 50...Switch circuit 60...Low pass filter 70...Delay circuit Special applicant Canon Co., Ltd. Agent Gi Marushima Knee: 'i'! ? i: Mi'-", '21 Sieve 3 Akebono High 4 View'th q ■ P,? 5゜R1G'z B:l G(, 65F3b
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〉P1)〉Ri-a phase

Claims (1)

[Claims] an imaging means combined with a plurality of color separation filters having different color spectral characteristics; a plurality of horizontal shift register means for outputting color signals corresponding to the color separation filters; and at least two horizontal shift registers of the horizontal shift registers. An imaging device comprising: drive means for driving a shift register with pulses of opposite phase.