JPS59104880A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain picture quality with excellent color reproducibility and high sensitivity by matching repetitive pattern of a color filter with a sharing period of a horizontal line signal to both shift registers so as to simplify a processing circuit for an output of image pickup element. CONSTITUTION:In driving both registers 31, 32 by same phase, outputs S1, S2 of the registers are amplified by amplifiers 5, 6. The phase of the output of the amplifier 5 is delayed by a prescribed amount of a delay circuit 7. After the outputs of the circuit 7 and the amplifier 6 are clamped by a clamp circuit, the output is applied to an R(red) component sampling circuit 90, a G(green) component sampling circuit 91, and a B(blue) component sampling circuit 92. The outpus are sampled and held respectively by sampling pulses RSW, GSW and BSW like these. A point sequential signal is made simultaneous by the circuits 90-92, and after the level of the outputs of the circuits 90, 92 are adjusted to a G signal by gain control circuits 93, 94, the output is processed again for point sequence at a switch circuit 95 so as to synthesize a luminace signal Y.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a solid-state imaging device using a solid-state imaging element.

(Prior art) Conventionally, this type of device uses an X-Y address solid-state image sensor called a MOS type, or an interline type C
OD, frame transfer type COD, etc. are often used.

Among them, the frame transfer type OCD is structurally very simple (1) compared to the MOS type and interline type because it does not require a vertical transfer register in the imaging section. Therefore, it is possible to integrate a large number of horizontal pixels corresponding to the horizontal direction of a TV screen. FIG. 1 is a diagram showing such a conventional frame transfer type COD, which includes an imaging section 1 that performs photoelectric conversion, a memory section 2 that temporarily stores charges from the imaging section, and a further section that stores charges from the memory section. It consists of a horizontal shift register 3 that transfers charges in accordance with TV synchronization, and an output amplifier 4 that reads out the charges as a voltage signal. On such COD,
The color separation filters necessary to create color signals are glued or on-chip. FIG. 2 is a diagram showing an example of the filter. Here, a conventional frame transfer type COD using the F, G, and B stripe method, which is said to have excellent color reproducibility, will be described.

If the number of horizontal pixels in the stripe method is approximately 580 elements, the horizontal transfer frequency is equivalent to 10.7 MHz, but
When using OOD with this number of elements.

Normally, the luminance signal is obtained from the output signal of the COD as it is (2) or passed through a high-band low-pass filter (approximately 3MH2), and the color signal is obtained from the R, G, and B signals at a repetition frequency of 3.
, 58 MHz are often separated into color signals using sample-and-hold circuits.

In this case, the color signal is 500KH in NTSO.
However, in this embodiment, the sampling frequency is 3.58 MHz, and the signal band can be reproduced up to the Nyquist frequency.

No problem. However, regarding the luminance signal, there is no problem when the subject image is close to achromatic, but for subject images with high color saturation, the sampling frequency is 3.58 M) (z
(Nyquist 1.8M)Iz), so a considerable amount of aliasing distortion occurred.

This will significantly reduce image quality. In order to solve this drawback, the number of horizontal pixels needs to be approximately 770, that is, it is necessary to drive at 14 MHz. With a COD that supports 14 MHz, the sampling frequency is approximately 4.77 MHz (Nyquist 2, 4
MHz), making it possible to significantly reduce aliasing distortion, which poses no problem at all in general television receivers (6).

However, in a COD compatible with 14 MHB, the following problems occur in the horizontal shift register, output amplifier, clock IC, and color separation sample and hold circuit.

First, in order to separate the color signals R0G and B from the output signal of the COD, the period of the portion corresponding to the effective signal component of the 14 MH2 signal must be long to some extent. However, when using a drive pulse with a duty ratio of 50%, the signal component is calculated to be (2×11°, 1□□) 35 ns, but in reality, the total rise and fall times due to the component elements of the drive circuit are approximately 10 ns. Then, the remaining portion becomes approximately 25n8. Furthermore, the rise of Rip Tsuku.

If the fall is too steep, dark current increases due to heat generation in the shift register, and the effective signal portion becomes even shorter.

Also, if the frequency characteristics of the output amplifier are taken into account, the effective signal period will become shorter than ever before. Like this 14 MH2
In the corresponding COD, the period of the signal component is considerably shortened (4), and fluctuations in the sample pulse due to element fluctuations or temperature fluctuations in the clock generating section are also added, making it difficult to separate the signals.
↓9 again. Currently, there is a drawback that it is quite difficult to integrate a 770-element CCD as a horizontal shift register of a urine-sized image sensor, for example. The first objective is to provide an imaging device capable of

A second object of the present invention is to provide an image pickup device and an image pickup device that can simplify or omit the sample and hold circuit configuration for color separation.

A third object of the present invention is to provide an imaging device that can accurately perform color separation of an image sensor having a large number of elements in the horizontal direction.

(Example) The present invention will be explained below based on Examples.

(5) This embodiment aims to eliminate the above-mentioned drawbacks.

Instead of the conventional COD having one horizontal shift register, a COD having two horizontal shift registers as read transfer paths as shown in FIG. 3(a) is used, and the horizontal transfer frequency is set to H to solve the above problem. The points are basically resolved. That is, the pixel charge in the horizontal direction is transferred to two horizontal shift registers at a period of one pixel by the clock circuit 46 shown in FIG. 3(0), thereby making the horizontal transfer frequency %.

In this case, although a frame transfer type CCD is explained in the embodiment, it is of course applicable to an interline transfer type OQD in exactly the same way. When the COD shown in FIG. 3(a) is laminated with the color filter shown in FIG. 2 and driven by a four-wheel circuit 46 shown in FIG.

1st. Outputs S1 and 8 of the second shift register 51.32
As shown in FIG. 3(1)), outputs with R, G, and B signals having mutually different phases are obtained from 2. The clock circuit 46 drives the COD and functions as a control means for controlling the distribution of charges to the (6) first and second registers.

Figure 3 (C) shows this first example. 2nd register output 81°82
This is a signal processing circuit for forming Y (R-Y) and (B-Y) signals. Considering the case where registers 31 and 32 are each driven in the same phase, the register output 81.8
After being amplified by 6, the output of the amplifier 5 is returned to the spatial sampling order by delaying the phase by a predetermined amount by a delay circuit 7.

Here, the delay amount of the delay circuit 7 is selected to be H of the clock cycle of the register 31.62.

The output of delay circuit 7 and amplifier 6 is clamp circuit fVC
Well-recrambled Kana R (red) component sampling circuit 90. G (green) component sampling circuit 91. B (blue)
The signal is input to the component sampling circuit 92. Then, the sampling pulse as shown in Fig. 3(C), nSw,G
sw, Bsw K rotation are each sampled and held.

Okay, here's the sampling pulse, ESW, and G8W.

(7) ESW is output from the clock circuit 46.

The sample and hold circuits 90 to 92 perform point-sequential synchronization of the color signals, and the outputs of the circuits 90 and 92 are level-adjusted to the level of the G signal in gain control circuits 93 and 94, respectively, and then sent to a switch circuit. In step 95, the Y signal is synthesized by performing point sequential processing again. This is Y
This is to obtain the high-frequency components of the signal without damaging them.

Further, the level-adjusted R, G, and B signals are input to a process circuit together with the Y signal, and are subjected to appropriate correction. By configuring as follows, it is possible to obtain the effect that the horizontal transfer frequency in the horizontal shift register becomes H.

4 is a diagram illustrating the configuration of essential parts of an example of the image sensor shown in FIG. 3(1). The shaded area is the channel stop, A, Bi
tVirtual electrode portion, O and D indicate the portion under the transfer electrode. 17 stores the line information of part of the memory in two registers 3.
It is a separation part for sequentially separating into 1.32 parts, and the separation may be performed by a gate electrode. 2E is a transfer electrode of the memory part (8) 2. 1 is the transfer electrode of the separation part, 51
B and 321 are transfer electrodes of registers 31 and 32, respectively.

OL is the clear gate section, and CD is the clear drain.

1Although one-phase drive is used in this embodiment, a drive method using two or more phases may be used. Also, the potential P (mu) of parts A and D
~P(D) is always P(D) > P(A) when a high-level voltage is applied to each transfer electrode, and P(B) > IF( when an o-level voltage is applied). 0). 1. In this embodiment, one out of every three pixels in the horizontal direction of the imaging section is configured to be used for purposes such as distance measurement. Further, one cell of the horizontal shift register 31 and 62 may be made to correspond to two vertical transfer paths in a part of the memory.

Next, FIGS. 5 to 9 are diagrams showing a second embodiment of the present invention. In this embodiment, in order to avoid the complexity of the signal processing circuit, the color pattern of the filter has a 09 (9) color pattern, thereby simplifying one circuit, and furthermore, providing a luminance signal with good image quality and a color signal with good one-color reproducibility. Fig. 5 is a color filter configuration diagram, Fig. 6 is an explanatory diagram of charge transfer to a shift register, Fig. 7 is a signal processing block diagram of the embodiment shown in Fig. 6, and Fig. 8 ( a) to (C) are diagrams showing other examples of color filter arrangement.

The color filter OF is placed between the one color filter configuration diagram.
A, 070 is repeatedly arranged.

Therefore, the charge in the horizontal line is reduced to 1 by the clock circuit 46.
By allocating each bit to both registers, the charge corresponding to the color filter OFB is transferred to the first shift register, and the charge corresponding to CIFB is transferred to the second shift register, as described later. A high-quality signal can be obtained using a signal processing circuit.

The present invention will be explained in more detail with reference to FIGS. 6 and 7.

(10) Figure 6 shows the color filters A and UFB in Figure 5.

R, G, and B transparent color filters are applied to cyc, respectively.

First, the charges (R, B) for each pixel column are transferred to the second shift register via the first shift register.

The charge corresponding to G is then transferred to the second shift register. The above transfer is performed by the clock circuit 46 during the TV horizontal blanking period. After that, the first. The charge in the second shift register is also read out by the clock circuit 46 as one horizontal scanning signal 81.82.

FIG. 7(a) shows the signal 81.8 read out as described above.
FIG. 2 is a block diagram of a signal processing circuit that generates an NTS signal or the like from NTSC. First, the operation of the circuit shown in FIG. 7(a) will be explained. Since the signal S1 is only the G signal.

The signal is directly guided to the high-pass filter 10 to become a high-frequency luminance signal YH, and is also guided to the process circuit 20 where gamma processing and the like are performed. On the other hand, the signal S2 is the color signal R1
B is sequentially read out as a signal, so in the sample and hold circuit 30.

(11) The signals are color-separated as simultaneous R and B signals and then led to the process circuit 20. In the process circuit 20, the above-mentioned R, G,
One color difference signal R-YL and B-YL and a low-range luminance signal YL are output from the B signal. The low-band luminance signal YL is then combined with the high-band luminance signal YH in an adder 40 to form an NTSO luminance signal Y having a full band. These luminance signal Y and color difference signals R-YL and B-YL are guided to an encoder (not shown) to become an NTSC signal.

By connecting this NTSO signal to a display, a high quality image with good color reproducibility can be obtained.

Next, FIG. 7(1)) is a block diagram showing a configuration for making the luminance signal band wider than the embodiment shown in FIG. 7(a).

That is, the phases of the signals S1 and 82 are returned to the original spatial sampling phase by the delay circuit 45, and each is added, and this added signal is used as a pseudo luminance signal. Sl and 8
2 signal level is approximately 1:1 when shooting an achromatic subject image.
If the system is adjusted so that the luminance signal band becomes extremely high.

(12) FIGS. 8(a) to 8(C) show an embodiment in which the color filter of this embodiment is constructed by a combination of a pure color type and a complementary color type, or a combination of a complementary color type. By including a correction type color filter in this manner, it is possible to easily improve the sensitivity and expand the luminance signal band.

FIG. 8(a) shows the color filters R0G and B of the embodiment in FIG.
In this example, G is changed to W, which transmits all colors. This Ro
The B and W methods have the effect that the luminance signal perfectly reproduces the subject image. The color filters shown in (1)) and (C) of the same figure undergo signal processing by the circuit shown in FIG. Although such a color filter requires a color separation circuit 55, it is possible to obtain a signal with high sensitivity and high resolution. In the circuit shown in FIG. 9, the spatial sampling phases of the outputs 81 and 82 are aligned by the delay circuit 45, and then added to obtain the Y signal. ), Cy
By calculating each color signal of (cyan) and the signal of G (green) or W (transparent) in the color separation circuit (13) 35, each signal of R and B can be obtained. In the embodiment described above, the horizontal shift registers 31 and 32 distribute the signals of one horizontal line in units of 11) it, but they may also be distributed in units of 21) it, for example, as long as they are distributed at a predetermined period.

(Effects) As explained above, according to the present invention, (1) The configuration of the sample and hold circuit for color separation can be simplified.

(2) S/ due to high-speed readout of horizontal shift register
A decrease in H can be prevented, and inaccuracies in separating the color signal from the dot-sequential signal can be reduced.

(5) The driving frequency of the horizontal shift register can be substantially lowered.

(4) Since only two horizontal shift registers are used, the configuration is simpler than when a horizontal register is provided for each color. (5) The repeating pattern of color filters and the horizontal shift register (14
) By matching the frequency of the input signal to both shift registers, the processing circuit configuration of the image sensor output is simplified, and furthermore, excellent color reproducibility and image quality with high resolution and high sensitivity can be obtained.

It has many effects such as

[Brief explanation of drawings]

Figure 1 is a configuration diagram of frame transfer type 00D, Figure 2 is l'
? , G, B is a diagram showing an example of a repeating color filter, FIG.
a) is a configuration diagram of an image sensor suitable for the present invention, FIG. 3(b)
is a diagram explaining how to distribute horizontal line signals, Figure 3 (
0) is a signal processing circuit diagram of the first embodiment of the present invention, and FIG.
a) is the timing diagram of the clock signal, and Fig. 4 is the timing diagram of Fig. 5 (
FIG. 5 is a schematic diagram of an example of the structure of the element in a), and FIG.
FIG. 6 is an explanatory diagram of a method for allocating to registers in the second embodiment; FIG. 7A is a block diagram of a signal processing circuit in the second embodiment; FIG. FIG. 7(b) is a diagram showing an example of another signal processing block, FIGS. 8(a) to (C) are diagrams each showing other embodiments of the color filter, and FIG. ) or (15) It is a diagram showing a signal processing circuit block of the color filter of (0). 31 and 32 are respectively the 1st. second horizontal shift register, 1
0 is a high-pass filter, and 20 is a process circuit. Patent applicant: Canon Co., Ltd. (16) - Okejo PJ Procedural Amendment (self-motivated) Director of the Patent Office Kazuo Wakasugi (1988) Patent Application No. 214412 2, Name of the invention Imaging device 3, Relationship with the amended person case Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (100
) Canon Co., Ltd. Representative Ryu Kaku Sanbe 4, Agent 146 Address 3-50-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. (Telephone: 758-2111) (1) 5. Specification subject to amendment 6. Contents of amendment Purification of the specification 1-0 We will submit and issue a retyped specification as shown in the attached sheet (no changes to the contents). Catalog type specification of Z attached documents 1 copy (?) 460

Claims (1)

[Claims] an image sensor that converts an optical image into electrical information; two readout transfer paths for dividing and reading out one horizontal line of information of the sensor; and predetermined information for one horizontal line for each transfer path. An imaging device having a control means for distributing the data at a period of .