JP2000228775A - Four-plate ccd-type fast image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the reverse phenomenon of a pixel centroid position by driving in interling manner each CCD image pickup element for red and blue light, compressing the time base of a signal obtained by two-stage vertical transfer to half for each scanning line period, and adding a twice-continuing signal and a signal delayed by the number of pixels in horizontal direction to the compressed signal, to execute the scanning line interpolation of red/blue optical signals. SOLUTION: An image pickup output signal (a) supplied to an input terminal 601 is speed-converted by a speed conversion circuit 602 formed of a line FIFO where a reading clock has twice as long period as a writing clock and continues it twice to make a signal (b). This signal (b) is split into two parts, one of them is supplied to an adding path 602 through a line memory 603 and the other is supplied to the path 604 directly to output a signal (c) delayed by the portion of pixels in a horizontal direction by a line memory 603. The signal (c) added by the adder 604 is supplied to a 1/2 multiplier 605 formed of a circuit executing the shift operation of one bit to send a signal (d) to an output terminal 606.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of outputting a television signal having a frame number twice as large as that of a normal (for example, 60 frames / sec in the NTSC standard system or the Hi-Vision system) without increasing the driving speed of an image pickup device. CCD that can
TECHNICAL FIELD The present invention relates to a high-speed imaging device of a four-plate type.

[0002]

2. Description of the Related Art In order to increase the number of frames per time of an image pickup apparatus, it is necessary to increase the driving speed of an image pickup device. However, driving the image sensor at high speed requires
Problems such as heat generation and increase in power consumption occur, and it is difficult to maintain image quality of a CCD image pickup device that is currently widely used due to a decrease in transfer efficiency. These problems are remarkable especially in a high-definition imaging device.

As a method of increasing the number of frames per time of an image pickup device without increasing the driving speed of an image pickup device, Sugawara, "Hi-Vision Slow-Motion Camera", Japan Broadcasting Corporation, Broadcasting Technology Research Institute, Giken Public Lecture, 1998 As described in the Research Proceedings, May 29, 1998, 4
There is an imaging method that combines a plate disassembling optical system and a pixel shifting technique.

[0004] The four-plate resolution optical system is designed so that green light, which is sensitive to human vision and occupies a large part of the luminance signal, has more (double) sample points than other color lights. As shown in FIG. 1, incident light is separated into blue light (B) at a first reflection surface and red light (R) at a second reflection surface. In addition, the green light that has traveled straight is
(G1 and G2).

In a high-speed imaging apparatus using a four-plate resolution optical system, a red light signal and a blue light signal having the same number of frames per time as a green light signal whose number of frames per time is doubled are obtained. Therefore, it is necessary to change the driving and signal processing methods of the red and blue light imaging devices. Therefore, in the method described in the above proceedings, the same IT (Interline Transfer) type or F type for red and blue light as for green light is used.
In a four-chip high-speed image pickup device using an IT (Frame Interline Transfer) type CCD image pickup device, charge transfer from the vertical transfer path to the horizontal transfer path is performed only when the red and blue light image pickup devices are driven. The frame frequency is doubled without increasing the driving speed of the horizontal transfer path by performing two steps continuously, and the normal number of scanning lines is secured and output by scanning line interpolation.

[0006]

In order to understand the problems of the conventional four-chip type high-speed imaging apparatus, it is necessary to use an IT type or F-type imaging apparatus.
An understanding of the configuration of the IT-type CCD image sensor is a prerequisite. FIG.
Shows the configuration of an IT-type CCD imaging device. In FIG. 2, light incident on the photodiode 201 during the vertical effective period is converted into an electric charge and accumulated. The charge is transferred to the vertical transfer path 202 within a vertical blanking period. At this time, the upper and lower two pixels are added by changing the combination for each field in order to perform the interlaced operation. The charges on the vertical transfer path 202 are driven by the vertical transfer pulse supplied to the vertical transfer pulse supply terminal 203 during the horizontal retrace period in the vertical effective period, and are transferred from the vertical transfer path 202 to the horizontal transfer path 204. . The electric charge transferred to the horizontal transfer path 204 is driven by a horizontal transfer pulse supplied to a horizontal transfer pulse supply terminal 205, and
6 and becomes a video signal of a predetermined level to output terminal 20
7 is taken out as an imaging output signal.

In the method described in the above-mentioned lecture / research presentation draft, charge transfer from the vertical transfer path 202 to the horizontal transfer path 204 (see FIG. 2) is performed in two stages within one horizontal retrace period. However, in this case, although the frame frequency is doubled, the number of scanning lines of the image sensor output constituting one frame is halved. In order to secure the normal number of scanning lines, it is necessary to interpolate and output the number of scanning lines. No. At that time, when the scanning line interpolation by simple repetition is performed, the center of gravity of the pixel at the time of imaging is changed due to the interlace driving and the two-stage vertical transfer performed within the one horizontal retrace period. Reverse after interpolation. This situation is shown in FIG.

Referring to FIG. 3, it will be described in detail that the center of gravity of the pixel is reversed at the time of imaging in the conventional CCD type four-chip high-speed imaging apparatus. In FIG. 3, in interlaced driving, there is a difference in processing depending on fields (even and odd fields). Therefore, even field processing is shown on the left and odd field processing is shown on the right. In FIG. 3, reference numeral 301 represents one column of the photodiodes 201 arranged in the vertical direction which constitute the IT type CCD image pickup device shown in FIG.

Photodiodes 301 arranged vertically
The upper and lower pixels are added in the vertical transfer path by the interlaced driving to form 302 and 306 (even and odd fields, respectively). Further, the scanning lines are added by the above-mentioned driving (the charge transfer is performed in two stages within one horizontal period). Therefore, signals 303 and 307 (even and odd fields, respectively) obtained by adding a total of four pixels are usually used. Imaging output signal having a frame frequency twice as high as that of the television signal of
Output from the CCD image sensor.

On the other hand, since this imaging output signal has only half the number of scanning lines as a normal television signal,
It is necessary to compress the time axis to 2 and then perform the scanning line interpolation to obtain the normal number of scanning lines. However, in order to obtain the normal number of scanning lines, the number of scanning lines is calculated by multiplying the imaging output signals indicated by reference numerals 303 and 307 by a coefficient 1 for scanning line interpolation indicated by reference numerals 304 and 308 (even and odd fields, respectively). (For the even and odd fields, reference numerals 305 and 3 respectively)
09) and the sample 309-1 corresponding to the imaging output signal 307 as well as the sample 305-2 in which the number of scanning lines corresponding to the imaging output signal 303 is doubled. Inversion of the position of the center of gravity of the pixel occurs between them. That is, the sample 305-2 generated from the imaging output signal 303 that should be located at the top of the screen is
It is located below the sample 309-1 generated from the imaging output signal 307 on the screen. The same applies to sample 305-4 and sample 309-3. This appears as a result of deterioration of the vertical resolution on the screen, sawtoothed oblique straight lines, and the like.

SUMMARY OF THE INVENTION An object of the present invention is to realize a CCD type four-chip high-speed image pickup apparatus in which a pixel centroid position (sample) of an image pickup output signal from a CCD image pickup device does not reverse after scanning line interpolation. An object of the present invention is to provide a plate-type high-speed imaging device.

Another object of the present invention is to provide a CCD type four-chip high-speed type in which the reversal phenomenon of the pixel center of gravity cannot occur in principle by devising a method of supplying a driving pulse to the horizontal transfer path of the CCD image sensor. It is to implement an imaging device.

[0013]

In order to achieve the above object, a CCD type four-chip high-speed imaging apparatus according to the present invention provides two systems of green light output for one input light, and red and blue light output. And a color separation system for generating one system each, and four CCD image sensors for converting each light output into an electric signal, two of the four CCD image sensors for green light The CCD type 4 is constructed such that each CCD image pickup device is driven with its phase shifted from each other on the time axis, and the time axis is compressed to 各, and then the respective compressed signals are synthesized to obtain a double speed green light signal. In the plate-type high-speed imaging device, each of the CCD imaging devices for red light and blue light is interlaced, and after two-stage vertical transfer within one horizontal retrace period,
The time axis of the signal obtained by the vertical vertical transfer is compressed to 1/2 for each scanning line period, and the signal in which the compressed signal is repeated twice in the one scanning line period and the signal are horizontally shifted. A signal delayed by the number of pixels is added, and the level of the signal obtained by the addition is reduced to 、, or the level of each signal is reduced to 前 before the addition and then added to 2 Signal processing means for performing scanning line interpolation of double-speed red light and blue light signals is provided.

A CCD type four-chip high-speed imaging apparatus according to the present invention is a color separation system for generating two green light outputs and one red and blue light output for one input light. Four CCs that convert each optical output to an electrical signal
D image sensor, and two CCD image sensors for green light among the four CCD image sensors have respective CCs.
A CCD type four-chip high-speed imaging device configured to drive the D image sensor with a phase shift relative to each other on the time axis and compress the time axis to 後 に, and then combine the respective compressed signals to obtain a double speed green light signal. In the device, each CCD for red light and blue light
After the pixel signals adjacent to each other are added and horizontally transferred in a horizontal transfer path for horizontally transferring the output signals from the respective CCD image pickup devices, the number of pixels obtained by the horizontal transfer is reduced to に つ い て. And a signal processing means for performing pixel interpolation between the respective pixel signals to obtain double speed red light and blue light signals.

In addition, in the CCD type four-chip high-speed imaging apparatus of the present invention, when adding the pixel signals adjacent to each other, the addition is performed by offsetting the output signals from the CCD imaging elements for red light and blue light. In addition, the offset is inverted every one scanning line period and / or one field period.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments of the present invention with reference to the accompanying drawings. First,
The first invention will be described. FIG. 4 and FIG.
1 shows an embodiment of signal processing in a CCD type four-chip high-speed imaging apparatus according to the invention of the present invention. Note that this example is a scanning line interpolation in the case of a CCD type four-chip high-speed imaging device for high-vision signals. FIG. 4 shows the first field and the second field, and FIG. 9 illustrates scanning line interpolation.

Here, the first field and the second field shown in FIG.
Field scan line interpolation is shown in FIG.
As is clear from the comparison with FIG. 3, the process is the same as that of the conventional example shown in FIG. 3 until the image pickup output signals 403 and 407 (first and second fields, respectively) of each field are obtained. In performing the scanning line interpolation on the obtained image pickup output signal, in the present embodiment, the following is performed.

That is, as shown by reference numerals 404 and 408 (first and second fields, respectively) in FIG. 4, the case where the image pickup output signals 403 and 407 are used as they are and the case where each half of the upper and lower image pickup output signals are used. Interpolation is performed so that the addition and the addition appear alternately. As a result, it is possible to prevent the center of gravity of the pixel from being inverted at the time of imaging and after interpolation, which occurs in the conventional scanning interpolation. The third and fourth fields shown in FIG. 5 are the same as those in FIG. 4 except that the combination of the two-stage transfer in the horizontal flyback period is changed, and thus the detailed description is omitted. At this time, the imaging output signal 503,
507 is an imaging output signal 4 in the first and second fields
Together with 03,407, the space is equally sampled.

FIG. 6 shows an example of the configuration of a scanning line interpolation circuit for performing the scanning line interpolation shown in FIGS. 4 and 5, and FIG. 7 shows signals of various parts in the scanning line interpolation circuit (FIG. 6). I have. FIG.
In FIG. 5, an imaging output signal (indicated by reference numerals 403 and 407 in FIG. 4 and reference numerals 503 and 507 in FIG. 5) is input to an input terminal 601.
) Are supplied. This signal is also shown in FIG.
(A). Note that the signal shown in FIG. 7 is represented by a time axis at equal intervals from A to F at the top because the time length and the temporal position are important.

The imaging output signal (a) supplied to the input terminal 601 is speed-converted by a speed conversion circuit 602 composed of a line FIFO whose read clock has a cycle twice as long as the write clock, and is continuously converted twice. And output as a signal shown in FIG. This signal is branched into two, one of which is supplied to the adder 604 via the line memory 603 and the other directly. The signal delayed by the number of pixels in the horizontal direction by the line memory 603 is shown in FIG. The signal added by the adder 604 is supplied to a 乗 算 multiplier 605 composed of a circuit that performs a 1-bit shift operation, and the signal shown in FIG. . This output signal is indicated by reference numeral 40 in FIG.
5 and 409, and signals (samples) of scanning lines indicated by reference numerals 505 and 509 in FIG. In the above, the 上 記 multiplication may be performed before the addition.

In the above-described embodiment, referring to FIG. 4, among the signals interpolated by the scanning lines, for example, 405-3 of the first field has one of the imaging output signals obtained from the four pixels preceding it. / 2 is included. Therefore, if the photodiodes 401 are provided in excess of four upper and lower portions for the target image format, complete scanning line interpolation according to the present embodiment can be performed.

Next, a second invention in which the inversion phenomenon of the pixel barycentric position cannot be generated in principle will be described based on an embodiment. According to a second aspect of the present invention, in a CCD imaging device, charges are transferred from a vertical transfer path to a horizontal transfer path (FIG. 2).
), The horizontal drive frequency is halved and CC
This makes it easier to realize a D-type four-plate high-speed imaging device.

First, in the transfer of electric charges from the vertical transfer path to the horizontal transfer path, as shown in FIG. 8, a horizontal transfer path that is driven in two phases with respect to one column of vertical transfer paths is conventionally arranged. .
Here, reference numeral 801 indicates a vertical transfer path, and 802 and 803 indicate horizontal transfer electrodes. Then, the horizontal transfer electrode 80
2803, horizontal drive pulses H1 and H2 having different phases.
Are respectively applied.

On the other hand, in the embodiment according to the second invention, as shown in FIG.
, The driving frequency is reduced to １ ／, and the horizontal transfer path is driven in four phases. Thus, the frame frequency can be doubled without increasing the horizontal drive speed of the image sensor. That is, the horizontal transfer electrodes 902,
Horizontal drive pulses H ₁ , H ₂ , H
₃ and H ₄ are applied, respectively, and the waveforms of the drive pulses and the application timing are shown in FIG.

Thus, the four-phase driving pulses H ₁ , H ₂ , H
_3, by the H ₄ applied in the horizontal blanking period 1001, may be added to the pixel (two pixels) adjacent to each other in the horizontal direction. In the horizontal video period 1002, a signal can be transferred to the left in units of two horizontal pixels by applying the driving voltage shown in FIG. It should be noted that the voltages applied within 1001 are H ₁ , H ₂
The combination of pixel addition can be changed by exchanging H ₃ and H ₄ . By performing this between the red signal and the blue signal, the horizontal resolution of the luminance signal can be improved.

The display screen thus obtained is, for example, as shown in the upper left or lower left of FIG. FIG.
In the display screen shown in Fig. 5, the combination of pixel addition on the same line is changed between the two fields, such as the upper left screen is an even field and the lower left screen is an odd field. The horizontal resolution of each color signal can be further improved by changing the combination of additions, that is, by performing pixel addition with offsets between them.

Also, as shown in FIG. 11, pixels are added with an offset between the red signal and the blue signal, and red- and blue-light in a dot-sequential manner is output with the same number of pixels as the green light. Pixel interpolation is necessary, but even if pixel interpolation by simple repetition is performed, the horizontal pixel centroid position at the time of imaging between adjacent scanning lines or between adjacent fields does not reverse after interpolation, so the pixel interpolation method Does not matter. Also, in the above processing, the leftmost and rightmost pixels cannot obtain the left or right signal to be added, respectively, but if there is one extra photodiode on the left and right for the target image format, Good.

[0028]

According to the first aspect of the present invention, the number of frames (frame frequency) can be doubled without increasing the horizontal drive speed of the red light and blue light imaging elements in the CCD type four-chip high-speed imaging device. It is possible to prevent the vertical resolution from being degraded due to the reversal of the barycentric position of the pixel at the time of imaging and at the time of reproduction when interpolating the scanning line of the signal and the blue signal.

According to the first aspect of the present invention, the spatial sampling points (samples) of the image are equally divided between the fields by performing the scanning line interpolation of the red signal and the blue signal in the above-described configuration. But the vertical resolution is improved.

According to the second aspect of the present invention, in which horizontally adjacent pixels are added, the number of frames (frame frequency) is doubled without increasing the horizontal drive speed of the red light and blue light imaging elements. In this case, it is possible to realize a CCD-type four-plate high-speed imaging device in which the reversal phenomenon of the pixel center of gravity cannot occur in principle. The horizontal resolution can be improved by interpolating the adjacent pixels with an offset between the red signal and the blue signal.

It is needless to say that if the driving frequency of the CCD image pickup device is increased, for example, by 1.5 times after applying the present invention, three times as high speed image pickup can be performed.

[Brief description of the drawings]

FIG. 1 shows a configuration of a four-plate resolution optical system.

FIG. 2 shows a configuration of an IT-type CCD imaging device.

FIG. 3 shows signal processing in a conventional four-chip high-speed imaging apparatus.

FIG. 4 shows signal processing in the CCD type four-plate high-speed imaging apparatus according to the first invention.

FIG. 5 also shows signal processing in the CCD type four-chip high-speed imaging apparatus according to the first invention.

FIG. 6 illustrates a configuration example of a scanning line interpolation circuit.

FIG. 7 shows signals of various parts in the scanning line interpolation circuit.

FIG. 8 shows a conventional configuration for transferring charges from a vertical transfer path to a horizontal transfer path in a CCD image sensor.

FIG. 9 shows a configuration for transferring charges from a vertical transfer path to a horizontal transfer path according to an embodiment of the second invention.

FIG. 10 shows waveforms of drive pulses for charge transfer and application timings.

FIG. 11 shows a display screen obtained by the embodiment according to the second invention, and a configuration in which pixels are added by offsetting between a red signal and a blue signal.

[Explanation of symbols]

201 photodiode 202 vertical transfer path 203 vertical transfer pulse supply terminal 204 horizontal transfer path 205 horizontal transfer pulse supply terminal 206 horizontal readout amplifier 207 output terminal 301, 401, 501 photodiode 302, 306, 402, 406, 502, 506 vertical transfer Scan lines 303, 307, 403, 407, 503, and 507 imaging output signals 304, 308, 404, 408, 504, 508 coefficients for scan line interpolation 305, 305-1, 305-2, 305-3, 305
-4,309,309-1,309-2,309-3,
309-4,405,405-1,405-2,405
-3,405-5,409,409-1,409-2,
409-3, 409-4, 505, 509 Signal (sample) after scanning line interpolation 601 Input terminal 602 Speed conversion circuit 603 Line memory 604 Adder 605 1/2 multiplier 606 Output terminal 801 901 Vertical transfer path 802 803, 902, 903, 904, 905 Horizontal transfer electrode 1001 Horizontal blanking period 1002 Horizontal video period

Continuation of the front page (72) Inventor Yoshihiro Fujita 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center F-term (reference) 5C065 AA01 BB38 CC01 DD02 DD07 DD26 EE01 GG13 GG21 GG23 GG30

Claims (3)

[Claims] 1. A green light output for one input light is 2
A color separation system for generating each of the red and blue light outputs one by one, and four CCD image pickup devices for converting the respective light outputs into electric signals; The two CCD image sensors for light are driven with their phases shifted from each other on the time axis, and the time axis is compressed to 後 に. CCD configured to obtain
In the four-plate type high-speed imaging device, the CCD image sensors for red light and blue light are interlaced and each stage is vertically transferred within one horizontal retrace period. The time axis of the signal obtained by
2, a signal in which the compressed signal is repeated twice in the one scanning line period and a signal obtained by delaying the signal by the number of pixels in the horizontal direction are added, and the level of the signal obtained by the addition is added. Or a signal processing means for performing the scanning line interpolation of the double speed red light and blue light signals by adding the levels of the respective signals to 1/2 before the addition and then adding the signals. A CCD type four-plate high-speed imaging device characterized by the following. 2. A green light output for one input light is 2
A color separation system for generating each of the red and blue light outputs one by one, and four CCD image pickup devices for converting the respective light outputs into electric signals; The two CCD image sensors for light are driven with their phases shifted from each other on the time axis, and the time axis is compressed to 後 に. CCD configured to obtain
In a four-chip type high-speed imaging device, pixel signals adjacent to each other are horizontally transferred in a horizontal transfer path for horizontally transferring output signals from the respective CCD image pickup devices for each of the red and blue light CCD image pickup devices. And a signal processing unit for performing pixel interpolation between the pixel signals of which the number of pixels obtained by the horizontal transfer is halved to obtain double speed red light and blue light signals. CCD type 4-plate high-speed imaging device. 3. The four-chip high-speed imaging apparatus according to claim 2, wherein, when adding the pixel signals adjacent to each other, an offset is applied between output signals from respective CCD image pickup devices for red light and blue light. A CCD, wherein the offset is inverted every one scanning line period and / or one field period.
Four-panel high-speed imaging device.