JPS6056031B2 - Color solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color solid-state imaging device that obtains color image signals using a solid-state imaging plate.

Image pickup tubes such as Brambicon and Vidacon are generally used to convert a subject image into a television signal, but recently solid-state image pickup plates have been attracting attention. Solid-state imaging plates include a combination of a charge transfer device combined with a photosensitive element such as a photodiode, a structure in which the light receiving part also serves as a charge transfer element, or a structure in which a large number of photosensitive elements are arranged in a lattice pattern and these are sequentially arranged. There are things like photodiode arrays that can be read to obtain continuous video signals.

As the principle of a charge transfer device is explained as a charge coupled device (hereinafter referred to as CCD) in Japanese Unexamined Patent Publication No. 46-1211, etc., a charge transfer device is a two-phase, three-phase, or An electrode wired in a four-phase configuration is provided, and if the semiconductor substrate is an N-type semiconductor, a negative potential is applied to this electrode to create a depletion layer in the semiconductor, and the potential of this electrode is By sequentially moving the depletion layer, the depletion layer is moved.

By injecting charges into this depletion layer, the charges can be sequentially moved along with the movement of the depletion layer. An example of a solid-state imaging plate using this principle is shown in FIG.

In Figure 1, 1-1, 1-2, 1-3, 1-4,...
...1-N are vertical CCDs that each transfer charges in the direction of the vertical arrow. The transfer pulse for vertical transfer is synchronized with the horizontal synchronizing pulse of the television signal. A photosensitive element 2, such as a photodiode, is provided along the vertical CCD, and charges are accumulated in accordance with the intensity of light.

Then, after a certain period of time has elapsed, this accumulated charge is simultaneously injected into the vertical CCD. The injected charges are sequentially transferred in the direction of the vertical arrow with pulses synchronized with the horizontal synchronizing signal. 3 is a horizontal CCD that horizontally transfers charges transferred to corresponding positions from a plurality of vertical CCDs.

Then, a horizontal transfer pulse having such a frequency that the charges are completely transferred in the direction of the arrow within the horizontal period is used to obtain a signal for one line from the output terminal 4. After repeating this process and reading out all the charges in the vertical CCD 1 from the output terminal 4, the charges accumulated in the photosensitive element 2 are again injected into the vertical CCD, and the same readout is repeated to obtain a continuous television signal. In this case, the transfer pulse frequency FH of the horizontal CCD 3 is expressed as FH=FvXN.

Fv: vertical CCD transfer pulse frequency=horizontal synchronization frequency N: number of vertical CCD columns 5 is a horizontal transfer pulse generator, 6 is a vertical transfer pulse generator, which may be 2-phase, 3-phase, or 4-phase.

When obtaining a color television signal, three such imaging plates are generally used, and each imaging plate receives light separated by a dichroic mirror to obtain a signal of each color. This corresponds to the imaging system of a three-tube color television camera that uses three image pickup tubes.

However, unlike the three-tube type using three image pickup tubes, very fine precision is required for positioning each image pickup plate.
As is well known, image pickup tubes generally deflect electron beams using a magnetic field, and after aligning the optical axes, direct current is passed through the deflection coils to superimpose each fine image. This allows you to move the position of the entire image. On the other hand, an image pickup plate cannot be aligned in the same way as an image pickup tube, and its amplitude cannot be adjusted. Therefore, there is no choice but to do all of this mechanically. In order to reduce or omit the number of adjustment points, a two-imaging plate system or a single-imaging plate system can be considered. FIGS. 2 and 3 show an example of a single-plate color solid-state imaging device that generates color signals using a single imaging plate, which has already been proposed.

Figure 2 shows a striped color filter.
, 8 and 9 are color filter elements that pass red, blue and green component lights, respectively. By placing this color filter on the solid-state imaging plate shown in FIG. 1, an output signal containing red, blue, and green component signals point-sequentially can be obtained as an output signal. By sampling and separating this output signal as shown in FIG. 3, the three primary colors can be extracted. In FIG. 3, numeral 11 denotes a solid-state imaging plate provided with a stripe filter as shown in FIG. 2, and is operated by each transfer pulse from a clock pulse generator 13.

A point-sequential output signal obtained from the solid-state imaging plate 11 is applied to a sampling circuit 15 via an amplifier 12. On the other hand, the horizontal transfer pulse from the clock pulse generator 13 is
The waveform is shaped into the phase and width of each color component signal through a waveform shaping circuit 14, and is applied to a sampling circuit 15, where it is used to separate each color component signal from the output signal. The separated color component signals are applied to a color encoder 16,
A standard color signal 17 is extracted. In addition, without sampling separation, the output signal obtained from the solid-state image pickup plate is passed through a bandpass filter whose center frequency is the red, blue, and green repetition frequency of the stripe filter, and then the horizontal transfer pulse or the like is generated. It is also possible to obtain a color difference signal by performing synchronous detection using a reference signal obtained by processing horizontal drive pulses. however,
According to these color signal separation methods, stripe filters of three colors must be used and corresponding photosensitive elements must be provided, so in order to obtain the same resolution as a monochrome image pickup plate, it is necessary to use three color stripe filters.
Requires double the number of elements. This means that three times the imaging area is required for colorization, but the imaging area.
An increase in the area is accompanied by great difficulties in manufacturing, and a color system that requires as small an area as possible is required. Therefore, an object of the present invention is to generate a color video signal by using one or two solid-state imaging plates, and to reduce the area of the necessary imaging section. The objective is to propose a color solid-state imaging device that can The present invention basically comprises a first array of photosensitive elements arranged along a horizontal line alternating with photosensitive elements each substantially sensitive to a first and a second color component;
and second photosensitive element rows in which photosensitive elements substantially sensitive to third and fourth color components are arranged alternately, respectively, are arranged vertically, and two different color differences are represented in successive horizontal scans. signals as output signals alternately,
Two color difference signals are simultaneously obtained from this output signal and a signal obtained by delaying it.

The color difference signal can be generated at two independent times by separating the signal of a single color light component from the signal obtained by each horizontal scan, for example by a sampling pulse synchronized with a clock pulse driving a horizontal scanning circuit. A series signal is obtained, and by taking the difference between two independent time series signals using a subtraction circuit and a low-pass filter, it is extracted as a baseband color difference signal.To generate a standard color television signal, After that, it is converted to a carrier color signal, and at that time, signal processing such as color temperature correction and white balance correction can be easily performed.Also, for the luminance signal, the output signal from the color image pickup plate is processed by a low-pass filter. A separate solid-state imaging plate may be used to generate the luminance signal.

The present invention will be explained below using examples. 4 to 6 are diagrams showing one embodiment of a color solid-state imaging device according to the present invention. FIG. This shows the imaging unit installed.

In the figure, the photosensitive element group and the vertical transfer stage are omitted to simplify the drawing. 21 transmits red R, 22
are color filter elements that transmit cyan C, respectively, and filter elements 21 and 22 are sequentially and alternately arranged along the direction of a horizontal line 25 shown by a dotted line. 23 is a color filter element that transmits blue B, and 24 is a color filter element that transmits yellow Ye. The elements 23 and 24 are sequentially and alternately arranged along the direction of a horizontal line 26 shown by a dotted line.

As is clear from FIG. 4, the color filter has a configuration in which rows of color filter elements arranged along horizontal lines 25 and 26 are alternately and repeatedly arranged in the vertical readout direction. Here, the area under each color filter is 1
In the case of bit or interlaced scanning, two bits worth of photosensitive elements are provided corresponding to each color filter element. The amount of signal charge corresponding to the intensity of light that has passed through each color filter element accumulated in the photosensitive element group is generated at a fixed period (one frame or one field).
The data is transferred to the corresponding position of each vertical transfer stage.

This signal charge is transferred line by line in the vertical read direction shown by arrow 27 by a vertical transfer pulse generated during the horizontal blanking period, and read into the corresponding position of horizontal transfer stage 281. Furthermore, the signal charge is transferred in the horizontal readout direction shown by an arrow 282 by a horizontal transfer pulse generated during the horizontal scanning period, passes through the signal charge detection section 283, and becomes the output signal 2.
Get 9. FIG. 5 shows one horizontal scanning signal obtained when equal white light is projected onto all the color filters arranged as described above.

4A shows an output signal obtained by one horizontal scan corresponding to the position of, for example, the horizontal line 25 shown in FIG. 4, as E1(t) with respect to the time axis t.

Now, when the horizontal transfer pulse applied to the horizontal transfer stage is of a two-phase type, the horizontal transfer pulse frequency FH is twice the fundamental frequency of E1(t).

FIG. 2b shows the output signal E2(t) obtained by the horizontal scanning subsequent to the horizontal scanning which provides the above output signal E1(t), for example, the output signal E2(t) obtained by one horizontal scanning corresponding to the position of the horizontal line 26 in FIG.
t).

Since cyan C is a color obtained by adding green G and blue B, and yellow Ye is a color obtained by adding green G and red R, a signal having an amplitude value as shown in FIG. 3 is obtained. When the horizontal repetition angular frequency of the color filter is ω, E1 in Fig. 5
If the output signals obtained by each horizontal scan of (t) and E2(t) are subjected to Fourier expansion, they are expressed as follows.

Doyu(' ▼▼-breath 11VlLiE 1(t) and E2(t) are obtained alternately for each successive horizontal scan.

A block showing an example of a configuration for generating color signals from these output signals is a block φHrIS dark 2↓ beat color image pickup plate, which is driven by vertical and horizontal transfer locks φV and φ8 from the clock pulse generation circuit 62. be done. 6
Reference numeral 3 denotes a sampling separation circuit which separates R (or B) and B+G (or G+R) components, which are repeated point-sequentially, using the horizontal clock φH.

Here, it is assumed that the transmission characteristics of the filter are designed so that the R (or B) component and the B+G (or G+R) component have the same amplitude with respect to the white signal. The time-series signals corresponding to the separated two colored lights are subtracted by a subtraction circuit 64, and a low-pass filter 65 in the next stage alternately converts the R-Y signal and the B-Y signal for each successive horizontal scan. I get a signal. On the other hand, the luminance signal is extracted by passing the output signal of the color image pickup plate 61 through a low-pass filter 66. 67 indicates a color encoder suitable for this embodiment, and 68
A carrier wave from a fixed oscillator 69 with a frequency of 3.58 MHz is modulated by a color difference signal, and a modulated color difference signal is obtained by passing it through a 900 phase shifter 70 and switching a switch circuit 71 every horizontal scan. .

This switching of the switch circuit 71 is performed in synchronization with the vertical transfer lock. The output signal of modulator 68 is
The signal passed through the H delay line 72 and the adder 73 are added to obtain two simultaneous color difference signals. These color difference signals and luminance signals are added in an adder 74 to obtain a color standard signal. FIG. 7 does not show another embodiment using different color filters, and the configuration for obtaining color difference signals other than the filters is the same as in FIGS. 4 and 6.

Here, 51 is a red filter element, 52 is a blue filter element, and 53 is a signal output from the corresponding photosensitive element that is almost equal to the signal output of the light receiving element corresponding to the red and blue filter positions when capturing an image of a white subject. This is a transparent filter element whose transmittance is controlled by a neutral density filter or the like, or a filter element for producing an output signal that approximates an NTSC luminance signal. In this case, as in FIG. 4, the RY signal can be obtained by horizontal scanning along the horizontal line 25, and the BY signal can be obtained by horizontal scanning along the horizontal line 26.

Note that the luminance signal can be obtained by sampling a signal corresponding to the portion of the filter element 53 from the output signal and passing it through a low-pass filter. This method has the advantage that only three filter colors are used compared to the method of the embodiment shown in FIGS. 4 to 6.

In the apparatus shown in FIG. 6, the color difference signal obtained from the low-pass filter 65 for each horizontal scan is made into a carrier color signal by a modulator 68, and then made into a simultaneous signal by using a 1H delay line 72 and an adder 73. However, it is also conceivable to adopt a configuration in which simultaneous signals are obtained at the previous stage.

The above embodiment describes a method using one image pickup plate, but a method using two image pickup plates, for example, the luminance signal Y from one image pickup plate and the method described in the example from the other. It can also be applied to a so-called two-plate color solid-state imaging device that obtains two color difference signals. As is clear from the above embodiments, according to the color solid-state imaging device according to the present invention, there is no need to use three solid-state imaging plates, and the imaging area is substantially smaller than that of the conventional device shown in FIGS. 2 and 3. It has the advantage of being able to reduce In addition, in conventional imaging devices using image pickup tubes, the beam scanning position became a problem and it was not possible to extract different color difference signals in consecutive horizontal scans as in the present invention, but in a solid-state imaging device, A horizontal scan can be performed on a fixed line. The present invention focuses on this point and proposes a novel solid-state imaging device.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional solid-state imaging plate that combines a photosensitive element and a charge transfer element, Figure 2 is a diagram showing a three-color striped filter, and Figure 3 is a striped filter shown in Figure 2. FIG. 1 is a block diagram of a conventional color solid-state imaging device that obtains a color signal by superimposing the image sensor on a solid-state imaging board, and FIG. 4 is a block diagram of a color imaging board in an embodiment of the color solid-state imaging device according to the present invention. Figure 5A, b
are diagrams showing the output signals of the image pickup plate in FIG. 4, FIG. 6 is a block diagram of a signal processing circuit for generating color signals in the same embodiment, and FIG. 7 is a diagram showing the output signal of the color image pickup plate in another embodiment. FIG. 21, 22, 23, 24... Color filter element, 61... Color imaging plate, 62...
...Transfer lock generation circuit, 63...Sampling separation circuit, 64...Subtraction circuit, 65...
...Low pass filter.

Claims (1)

[Claims] 1. A color filter and a photosensitive element are combined to form a photosensitive unit, and the difference in output between the first photosensitive unit and the second photosensitive unit is positive with respect to the primary color light red, and the primary color light is blue or green. The difference between the outputs of the first photosensitive unit row in which the first and second photosensitive units are arranged alternately in the horizontal direction, the third photosensitive unit, and the fourth photosensitive unit, which is negative, is the primary color light blue. A second photosensitive unit row in which the third and fourth photosensitive units, which are positive with respect to the primary color light and negative with respect to the primary color light red or green, are repeatedly arranged in the horizontal direction is alternately arranged in the vertical readout direction, The photosensitive unit is such that the sum of the outputs of the first and second photosensitive units is equal to the sum of the outputs of the third and fourth photosensitive units, and in continuous horizontal scanning, the sum of the outputs of the third and fourth photosensitive units is equal. means for alternately reading out a first signal and a second signal from the second row of photosensitive units in line sequence; and having the first signal or the second signal as an input;
sampling separation means for separating a signal from the first photosensitive unit and a signal from the second photosensitive unit or a signal from the third photosensitive unit and a signal from the fourth photosensitive unit; a subtraction circuit; and a low-pass filter. A first color difference signal is obtained from the signal from the separated first photosensitive unit and the signal from the second photosensitive unit, which are the outputs of the sampling separation means, and a signal from the third photosensitive unit. A color solid-state imaging device comprising: means for obtaining a second color difference signal from a signal from a fourth photosensitive unit. 2. A photosensitive unit is formed by combining a color filter and a photosensitive element, and the difference between the outputs of the first photosensitive unit and the second photosensitive unit is positive for the primary color light red and negative for the primary color light blue or green. The difference between the outputs of the first photosensitive unit row in which the first and second photosensitive units are alternately arranged horizontally, the third photosensitive unit, and the fourth photosensitive unit is positive with respect to the primary color light blue, and the primary color is A second photosensitive unit row in which the third and fourth photosensitive units that are negative with respect to light red or green are arranged repeatedly in the horizontal direction is alternately arranged in the vertical reading direction, and the first photosensitive unit and the second photosensitive unit are arranged alternately in the vertical readout direction. one of the photosensitive units has a characteristic that produces a signal representing brightness, and one of the third photosensitive unit and the fourth photosensitive unit has a characteristic such that it generates a signal representing brightness. means for alternately reading out a first signal from the first photosensitive unit column and a second signal from the second photosensitive unit column line sequentially in continuous horizontal scanning; Sampling separation that takes a signal or a second signal as input and separates the signal from the first photosensitive unit and the signal from the second photosensitive unit, or the signal from the third photosensitive unit and the signal from the fourth photosensitive unit. obtaining a first color difference signal from the separated signal from the first photosensitive unit and the signal from the second photosensitive unit, which are the outputs of the sampling and separation means, having a subtracting circuit and a low-pass filter; A color solid-state imaging device further comprising means for obtaining a second color difference signal from a signal from the third photosensitive unit and a signal from the fourth photosensitive unit.