JPS59231981A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To improve twice the horizontal image resolution without changing the vertical image resolution by giving a pulse oscillating waveform taking two- frame period as one period to a substrate of a solid-state image pickup element chip. CONSTITUTION:The solid-state image element chip 10 is fixed on a vibrating base 11 and the image of a light input is formed on the chip 10 through an image pickup lens 12. An oscillating pulse is applied to the vibrating plate 11 from an oscillating pulse generating circuit 13 by an amplitude corresponding to PH/2. This oscillating pulse is a pulse taking the 2-frame period as one period. A timing generating circuit 14 generates required synchronizing pulses such as a timing signal of a PH/2 delay circuit 15 to give a delay of PH/2 to the timing of a horizontal read register in matching with the period of the oscillating pulse and a timing signal of a vertical read register or the like. Then an output signal obtained from the chip driven by a clock driver 16 is outputted through a signal processing circuit 18.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to solid-state imaging that obtains high-resolution images using a solid-state imaging device having a limited number of pixels and having photosensitive parts arranged two-dimensionally on a semiconductor substrate. Regarding equipment.

[Technical background of the invention and its problems] Solid-state imaging devices such as C and CD have the characteristics of being smaller, lighter, and more reliable than conventional image carrier tubes. It has many advantages such as small size and no burn-in. Therefore, its applications are wide-ranging, including industrial television cameras, home video cameras, and electronic cameras that do not use silver halide film, and are expected to expand further in the future.

FIG. 1 shows a schematic configuration of a typical interline transfer type COD. prj (j=1.2...

M,j=1.2. ..., N) are two-dimensionally arranged photosensitive parts, Ci is a vertical readout COD register, and H is a horizontal readout COD register. When applying such a solid-state image sensor to a wide range of applications as described above, a major problem is how to achieve high resolution with a limited number of pixels.

Therefore, the inventors of the present invention previously proposed in Japanese Patent Application No. 56-209381 an apparatus in which high resolution was achieved by using a solid-state image sensor with a limited number of pixels.

The principle of this device is shown in Figure 2.
The chip substrate 1 of the body image sensor (only a part of the -horizontal row is shown) is arranged at a horizontal pixel pitch Pl+ in the horizontal direction (X direction).
is vibrated relative to the incident optical image with an amplitude of PH/2, which is equivalent to 1/2 of PH/2. Here, as shown in the figure, the temporal change of the vibration is trapezoidal in synchronization with the imaging operation in which the first (A) field and the second (B) field of the solid-state imaging device are one frame period. As a result, the aperture of the pixel shown in the figure is at the position indicated by the solid line 2 in the A field, and at the position indicated by the broken line 3 in the B field. And A,
By turning on the field shift pulse at the time of switching between B field or B, A field, A, B
At the time of field switching, the optical signal accumulated charge at the position of the aperture 2 is read out. Then, at the time of switching between the B and A fields, the optical signal accumulated charge at the position of the aperture 3 is read.
put out. Then, the readout signal accumulated charge is shifted by the driving timing or by signal processing so that it becomes an image corresponding to the position of the spatial sampling point of the A and B fields, and the A and B fields are added on the reproduced image. By doing so, the number of horizontal spatial sampling points that the solid-state image carrier itself has is doubled, and the horizontal resolution can be doubled. Furthermore, since the invalid portion of the solid-state imaging device with respect to the incident optical image is reduced, the moiré inherent in the solid-state image device is improved. FIG. 3 is a diagram showing spatial sampling points 4 on the reproduced image. 1 H in A field
This becomes the spatial sampling point 4a in the scanning lines A, 2HA, 3HA, . . . And in the B field, 1HB
, 2H1 . . . is the spatial sampling point 4b in the scanning line. As a result, the phase of the spatial sampling point in the A field and the spatial sampling point in the B field becomes 1/2 tcp, which is equivalent to 1/2 of the horizontal readout frequency fcp.

Therefore, the number of spatial sampling points in the horizontal direction on the reproduced image is doubled.

However, doubling the spatial sampling points with this device is A
This is performed at a scanning line in the field, for example, IHA, and a scanning line in the B field, for example, IH8, which is adjacent to the scanning line. Therefore, the spatial sampling points on the same scanning line are not doubled, and errors occur because the spatial sampling points extend over the A and B fields for a fine incident optical image. This error causes a zigzag pattern at the black-and-white boundary line on the reproduced image, resulting in a problem of deterioration of image quality. In addition, since the spatial sampling points in the vertical direction are not on the same vertical line between fields A and B, errors occur as described above, resulting in zigzag-like image quality deterioration at the black-and-white boundary line in the vertical direction on the reproduced image. There was a problem.

[Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to provide a high-resolution solid-state imaging device in which the vibration mode is improved so as to double the spatial sampling points on one scanning line. do.

[Summary of the Invention] The present invention is an interline transfer type COD as shown in FIG. The solid-state image sensing device deep substrate has an imaging operation of reading out the image during the effective period, and the A field and B field are one frame period, and the solid-state image sensor deep substrate has an operation that leads to the second frame period. The vibration center is set at one end of the vertical blanking period, and is moved by the equivalent of 1/2 horizontal pixel bit relative to the incident optical image in a certain invalid period, and left as it is in the next invalid period. Then, in the next invalid period, a pulse-like vibration is applied to the solid-state image sensor chip substrate, which moves the solid-state image sensor chip substrate in the opposite direction by the equivalent of 1/2 horizontal pixel pitch relative to the incident optical image, with one cycle being two frame periods. By doing so, higher resolution was achieved.

[Effects of the Invention] The solid-state imaging device according to the present invention can essentially achieve higher resolution than conventional solid-state imaging devices. Further, by increasing the density of the chip substrate itself, it is possible to obtain images with better characteristics, such as dynamic range and generation of false signals, than a solid-state imaging device with the same number of pixels as the present invention. The production of drive circuits for operating these devices is also easier than in high-density solid-state image carriers.

Furthermore, the zigzag-like image quality deterioration at the black and white boundary line on the reproduced image, which was seen in the above-mentioned Japanese Patent Application No. 56-209381, does not appear in the present invention, and a good high-resolution image can be obtained.

[Embodiment of the Invention] FIG. 4 is a diagram for explaining an embodiment of the present invention. This figure shows the relationship between the solid-state image sensor, the time relationship in which the solid-state image sensor is vibrated, and the timing relationship of the field shift pulse that reads signal charges from the photosensitive portion of the solid-state image sensor.

The interline transfer type CCD chip substrate 1 shown in FIG. let The time change of this vibration is determined by the interlace operation in which the A and B fields are one frame period in the imaging operation of the interline transfer type COD in the field time accumulation mode, with two frame periods as one cycle.
A.

It is shaped into a trapezoid so that the center of vibration is within the invalid period between B fields. The amount of vibration from x1 to x2 is set to P1□7/2, which is equivalent to 1/2 of the horizontal pixel pitch P1□.

Next, specific operations will be explained. First, in ti of field A1 of the first frame, the center of the opening 2 of the CCD deep substrate 1 is placed at the x1 position to perform optical signal accumulation. Then, at t2 of the 81 field of the next first frame, the CCD chip substrate 1 is relatively vibrated to the right in the figure, and the opening center of the opening 2 is moved to the position 3 so that it is at the position x2. come. Then, optical signals are accumulated at this position. The amount of vibration at this time is 1 of the horizontal pixel pitch PH.
PH/2, which is equivalent to /2. Then, in field 13 of A2 of the next second frame, the optical signal is accumulated at the x2 position with the aperture center position unchanged. Then, at t4 of the 82nd field of the next second frame, the CCD chip substrate 1 is vibrated to the left in the figure and brought from the x2 position to the x1 position. Then, optical signals are accumulated at this position.

The amount of vibration at this time is set to PH/2 as described above. From now on, the third
frame, fourth frame...The nth frame repeats the same operations as the first and second frames.

In the above operation, the center of opening 2 moves from the position of ×1 to ×
If the period during which it moves to position 2 and the period during which it moves from position x2 to position x1 are sufficiently short, A1. Bi,
In each field A2 and B2, the center of the aperture is X
It can be considered that it is equivalent to standing still at the position 1, X2. As a result, the number of spatial sampling points in the horizontal pixel array direction is 2.
Double.

Then, by shifting the drive timing so that the image corresponds to the position of the spatial sampling point of each field on the reproduced image and adding each field for display, the horizontal resolution of the solid-state image sensor itself is doubled. can.

FIG. 5 is a diagram showing the movement of spatial sampling points with respect to the incident optical image when the interline type COD chip substrate of FIG. 1 is vibrated in the vibration mode shown in FIG. 4. (a) is the A1 field, (b) is the B2 field, (c) is the A2 field, (d) is the spatial sampling point in the B2 field, and the solid lines indicate 1HA, 2HA, 3HA,... IHAno, 2H
A113HAノ, . . . indicate the scanning line position in the A field in the imaging operation of the interline transfer type COD in the field time accumulation mode, and I HB', 2 H
nl, '3 HB/, I HB/, 2H,, 3HB
, . . . indicate the scanning line position in the B field. The arrow displayed at each spatial sampling point indicates the direction of movement of the spatial sampling point when passing over the next field.

The spatial sampling point in field 1 is the next B!
In the field, the combination of interlaced imaging and PH/2 vibration in the horizontal pixel arrangement direction moves diagonally downward and to the right in the figure. Then, in the next A2 field, no vibration is performed and only interlaced imaging is performed, so the spatial sampling point moves upward in the figure. Furthermore, in the B2 field, the spatial sampling point moves toward the lower left in the figure due to the combination of the interlaced carrier image and vibration.

As a result of the above operations, the spatial sampling points will be at the positions shown in FIG. Shown in FIG. 6(a).

The spatial sampling points of (, b >, (c), (d) are (a >, (b), (0
), ((1) It corresponds to Varnish 1. As a result, when displayed according to the actual sampling point on the reproduced image, A,
The sampling point in the horizontal direction on the scanning line of the B field is twice the horizontal pixel pitch PH. The sampling points in the vertical direction become the vertical pixel pitch Pv in interlaced imaging of the A and B fields. Here, since the time width of the horizontal pixel pitch PH is determined by the reciprocal of the driving frequency tcp of the horizontal read register, the pitch of the spatial sampling points in the horizontal direction is 1. /2fcρ. Therefore, the horizontal limit resolution can be improved to twice the limit value determined by the driving frequency of the horizontal reading register.

Furthermore, the zigzag-like image quality deterioration at the black and white boundary line on the reproduced image, which was a problem in the conventional operation described in FIG. 3, is significantly improved in this embodiment.

Furthermore, in this embodiment, the spatial sampling points in the vertical interlaced imaging of the A and B fields have an inverted phase relationship, so that moiré flicker can be improved.

Further, in this embodiment, the vibration period is 1/2 that of the conventional example shown in FIG. This becomes effective when a bimorph piezoelectric element using ceramic, for example, is used as the vibration mechanism. When a bimorph piezoelectric element is used as a vibration mechanism, it is vibrated at a frequency lower than the resonance frequency of the element itself. As a result, ringing is likely to occur when the vibration pulse changes.

This is because if the vibration period is reduced, the amount of ringing can also be reduced.

FIG. 7 is a configuration diagram of this embodiment, and FIG. 8 is an operating waveform diagram thereof. The solid-state image sensor chip 10 is fixed on a vibration table 11, and input light passes through an imaging lens 12 and is imaged onto the solid-state image sensor chip 10. A vibration pulse shown in FIG. 8 is applied to the vibration table 11 from the vibration pulse generation circuit 13 at an amplitude equivalent to P,./2. This vibration pulse is synchronized with the field shift pulse operating within the vertical blanking period, as shown in FIG. It is a pulse whose period is two frame periods. The timing generation circuit 14 generates the timing signal of the PH/2N delay circuit 15 for delaying the timing of the horizontal readout register by P/2 in accordance with the period of the vibration pulse, and other necessary synchronization pulses such as the timing signal of the direct readout register. Occur. The output signal obtained from the solid-state image sensor chip 10 driven by the clock driver 6 is outputted through the preamplifier 17 and the signal processing circuit 18. That is, in this example, in order to shift the output signal in accordance with the spatial sampling point caused by the vibration of the solid-state image sensor chip 10, the timing of the horizontal clock pulse is changed by 1/2 clock (1/2 clock) in accordance with the vibration period as shown in FIG. 2tcp), thereby obtaining an output signal that matches the actual spatial sampling point. And As , Bt , A
By adding the first frame and the second frame, which are each composed of 2.82 fields, on the reproduced image, the resolution in the horizontal direction can be doubled.

As explained above, this embodiment has an imaging operation in which the signal charge accumulated in the photosensitive section for each field is simultaneously transferred to the vertical readout register, which is the readout section, during the vertical blanking period, like an interline transfer type COD. By vibrating the solid-state image sensor chip substrate with a period of 2 frames (4 fields) in the horizontal pixel arrangement direction so that the center of vibration is located during the blanking period, the spatial sampling points of the solid-state image sensor itself are By doubling the resolution, it is possible to obtain a reproduced image in which the horizontal resolution is doubled without deterioration in the vertical resolution.

Even if a device with double the number of pixels in the horizontal direction is realized by high-density technology, the solid-state imaging device according to this embodiment has the following characteristics advantages compared to this device.

(1) In a high-density device, the horizontal pixel pitch becomes 1/2, so the saturation signal level decreases and the dynamic range becomes smaller, but in this embodiment, it is equivalent to a device that does not vibrate.

Therefore, if the same manufacturing technology is used, it is essentially possible to obtain a wider dynamic range than a high-density device.

(2) In high-density devices, the clock frequency of the horizontal read register is doubled, which increases the power consumption of the drive circuit and signal processing circuit, and increases the difficulty of circuit fabrication; however, in the device of this embodiment, this is not the case. do not have.

(3) In a high-density device, the ratio of the aperture area of the photosensitive section may decrease but never increase, so even if the density is increased, the invalid area for optical information in the entire photosensitive area will not decrease. On the other hand, in this embodiment, since optical information is obtained even from a conventionally ineffective area, the effective area for collecting input optical information is essentially wide.

Next, another embodiment of the present invention will be described. FIG. 9 shows the case of vibration pulses applied to the solid-state imaging chip substrate, which is different from the above embodiment. In this case, AI(tl), Bt (
t2) During the first frame period consisting of a field, the opening 2 of the solid-state imaging chip substrate 1 is placed at the position XI. And A2 (13).

In the second frame period consisting of field B2 (t4), the aperture is moved by P n /2 to a position of x2, which is indicated by the broken line 3. That is, the center of vibration is brought to the dead period between frames. This allows the fifth
The location of the spatial sampling point explained in the example of the figure is the fifth
In the figure, the field order is AI-+Bl→A2→B2 (
The spatial sample point positions are a) → (b) → (C) → (d), and in Figure 9 the field order is the same as in Figure 5, (a) → (d) → (C) → (1 )) The spatial sampling points move in the order of As a result, twice as many sampling points are obtained on the reproduced image in the horizontal pixel arrangement direction as in the case described with reference to FIG. 6, and a high-resolution image with reduced moire similar to the previous embodiment is obtained.

In the example described above, the present invention was applied to a video camera that is applied to a television standard system, but the present invention can be applied to, for example, an electronic camera that does not use a silver halide film, an OCR system, or the like. FIG. 10 is a diagram showing the operation when the present invention is applied to an electronic camera. In this case,
As with a normal optical camera, it is necessary to synchronize the opening/closing timing of the optical shutter with the operation of the positive image element.

A1. The first frame consisting of Bt field and A2, B
In the @image operation of the second frame consisting of two fields, a field shift pulse is applied at the switching point of each field, and the signal charge accumulated in each field is read out. The vibration pulse has a waveform similar to that shown in FIG. 4, in which the first and second frames are one cycle. In the shutter pulse I, the shutter is ON during the first and second frames, and the spatial sampling points of the incident optical image are doubled during this period.

Further, in the case of shutter pulse (2), the ON period of the shutter is shortened. Further, in the case of the shutter pulse (3), the shutter is turned off during the period of change of the vibration pulse, thereby providing a more reliable operation in which the spatial sampling points are doubled.

Furthermore, various modifications and applications of the present invention are possible as listed below.

a The image sensor is not limited to the interline transfer type CCoi image element, but for example, a frame transfer type (1?) element may also be used.What these image sensors have in common is that the signal charge accumulated in the pixel area is This means that the reading operations are performed simultaneously during the blanking period. Therefore, the present invention can be applied to any sensor that performs similar operations.

1) The aperture shape of the pixel of the image sensor is not limited to a rectangle,
Its size is also not particularly limited.

The pixel arrangement of the CR image element is not limited to being arranged in a line in the vertical direction, but may be arranged in a zigzag manner, which is more advantageous for reducing moiré and improving resolution.

d The image sensor is a normal CCD1lf as a photoelectric conversion unit.
It is possible to use a so-called two-story sensor structure in which a photoelectric conversion film such as amorphous silicon is layered on the i (I element).

e In the case of a two-story sensor using a photoelectric conversion film, it is also possible to obtain an ultraviolet image or an infrared image depending on the properties of the photoconductor. In addition, a phosphor film is used instead of a photoconductor film to perform XPA
The present invention can also be applied to obtaining @. Furthermore, it can be used as a device to superimpose visible and invisible images and observe them on the reproduced image by arranging a normal visible conversion film and an invisible conversion film such as infrared, ultraviolet, and X-ray for every other pixel in a two-story sensor. The present invention can be applied. In this case, by setting the vibration pulse constant to the horizontal pixel pitch, both visible and invisible images can be reproduced without deterioration in horizontal resolution.

f In the present invention, the image sensor chip is vibrated relative to the optical image, but the same concept can be applied to an electron beam impact type solid-state image sensor.

That is, by using the ability to deflect the electron beam image,
1. A similar effect can be obtained by changing each field of Bt, A2, and B2 in a predetermined direction.

q The present invention can also be applied to color cameras that perform color 11ii (i) using one, two, or three image sensors.The present invention and the pixel shifting method can be used in common with two-panel and three-chip color cameras. In addition, in a two-chip color camera that uses primary colors, the image sensor that obtains the G signal is vibrated by half the horizontal pixel pitch, and the image sensor i that obtains the R and B signals is vibrated. The resolution can be further improved by vibrating the horizontal pixel pitch.

h The means of vibration in the present invention is not limited to the vibration of the solid-state image sensor itself as explained in FIG. 7. For example, an optical deflection plate may be provided on the light incident side of the solid-state image sensor, and the deflection plate may be periodically vibrated, or the incident light may be deflected by an optical mirror. In short, it is sufficient to vibrate the solid-state image sensor relative to the incident light image.

i The vibration pulse of the present invention has been explained using a trapezoidal wave, but this shape does not have to be trapezoidal, but can also be rectangular or triangular, since the number of sampling points within a unit pixel will still increase.
The present invention is applicable.

j Most of the description of the present invention has been made using the TVIi image format based on the NTSC standard format, but the present invention is not limited to this format. That is, the present invention is applicable to any system that performs interlaced imaging. For example S E 'CA
It can be applied to M system, PAL system, low speed imaging system, high speed imaging system, etc.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a schematic configuration of an interline transfer type CCD image sensor, Fig. 2 is an explanatory diagram of the principle of the solid-state image pickup device previously proposed by the present inventors, and Fig. 3 is the operation of Fig. 2. FIG. 4 is a diagram showing the state of vibration of the image sensor in an embodiment of the present invention, and FIG. 5 is a diagram showing each field of the spatial sampling points in the same embodiment. 6 is a diagram showing the spatial sampling points of FIG. 5 added on the reproduced image, FIG. 7 is a diagram showing the overall configuration of the device of the same embodiment, and FIG. 8 is an explanation of its operation. FIG. 9 is a diagram showing the state of vibration in another embodiment of the present invention, and FIG. 10 is a diagram for explaining the operation when the present invention is applied to an electronic camera. DESCRIPTION OF SYMBOLS 1... Solid-state image sensor chip board, 2... Pixel aperture, 10... Solid-state image sensor chip, 11... Vibration table, 12... Imaging lens, 13... Vibration pulse generation circuit , 14...timing generation circuit, 15...PM/
2 delay circuit, 16... clock driver, 17...
Preamplifier, 18...signal processing circuit. Figure 2 Figure 4 Sukin Pulse Figure 9 Figure 10

Claims (3)

[Claims] (1) A method that uses a solid-state image sensor that has photosensitive parts arranged two-dimensionally on a semiconductor substrate to continuously obtain frame images through interlaced imaging in which the first and second fields constitute one frame. , the signal charges photoelectrically converted and accumulated in each of the photosensitive sections are simultaneously transferred to the readout section, and while the signal charges of the readout section are sequentially moved to the output section and read out, each of the photosensitive sections receives the signal of the next field. A solid-state imaging device that performs an operation of accumulating charge includes means for vibrating the solid-state imaging element chip substrate in a horizontal pixel arrangement direction relative to an incident optical image, and the vibration waveform is as follows:
It is pulse-like with one period consisting of two consecutive frames, the amount of vibration is 1/2 of the horizontal pixel pitch or its vicinity, and the center of vibration is within the period during which the signal charge is transferred from the photosensitive section to the readout section. What is claimed is: 1. A solid-state imaging device, characterized in that a process is performed to correct, on a reproduced image, a shift in a spatial sampling point of an incident optical image caused by the vibration. (2) The vibration center of the vibration waveform is the 1st point of the 0th frame.
The solid-state imaging device according to claim 1, wherein the solid-state imaging device is located between the first field and the second field and between the first field and the second field of the (n+1> frame). (3) The vibration center of the vibration waveform is the nth frame and the (
n + 1 > claim 1 between frames
The solid-state imaging device described in .