JPS5838991B2 - 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 uses a solid-state imaging plate to extract color image signals.

Image pickup tubes such as planpicon and videcon 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 element coupled to a photosensitive element such as a photodiode, a structure in which the light receiving section also serves as a charge transfer element, or a structure in which a large number of photosensitive elements are arranged in a lattice pattern. There are devices such as photodiode play that sequentially read the images to obtain a continuous video signal.

Regarding charge transfer devices, as explained in Japanese Patent Application Laid-Open No. 46-1211 and elsewhere as a charge-coupled device (hereinafter referred to as CCD), two-phase, three-phase, three-phase, Alternatively, an electrode wired in a four-phase configuration is provided, and if the semiconductor substrate is an N-type semiconductor, a depletion layer is created in the semiconductor by applying a negative potential to this electrode, and the potential of this electrode is sequentially increased. By moving, the depletion layer is also moved.

If charges are injected into this depletion layer, the charges can be sequentially moved as the depletion layer moves.

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.

2 is a photosensitive element such as a photodiode, and vertical C
It is provided along the CD, and charges are accumulated depending on the intensity of light.

Then, after a certain period of time, this accumulated charge is simultaneously injected into the vertical CCD.

The injected charges are sequentially transferred in the direction of the horizontal arrow by pulses synchronized with the horizontal synchronization signal.

3 is a horizontal CCD that horizontally transfers charges transferred from a plurality of vertical CCDs to reaction positions.

Then, the charge is transferred using a horizontal transfer pulse having a frequency such that the charge is completely transferred in the direction of the arrow within the horizontal period, and a signal for one line is obtained 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 injected again, 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 fH=
It is expressed as fVXN.

However, f■: transfer pulse frequency of vertical CCD 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 receives light separated by a gicroic 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 the optical axes are approximately aligned, each fine image is superimposed by passing a direct current through the deflection coil to adjust the position of the entire image. can be moved.

On the other hand, an image pickup plate cannot be aligned like an image pickup tube, and the amplitude cannot be adjusted.

Therefore, there is no other choice but to do all of this mechanically.

In order to reduce or eliminate the number of adjustment points, a two-imaging root system or a single imaging system can be considered.

FIGS. 2 and 3 show an example of a single-plate color solid-state imaging device that uses one imaging plate to generate color signals, which has already been proposed.

FIG. 2 shows a striped color filter, in which reference numerals 7, 8 and 9 are color filter elements that pass red, blue and green component light, respectively.

By placing this color fill 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. As shown in FIG. 3, the three primary colors can be extracted by sampling and separating the frames.

In FIG. 3, reference 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 φH2φV 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 signal generator 13 is waveform-shaped through a waveform shaping circuit 14 into the phase and width of each color component signal, and is applied to a sampling circuit 15, where it is used to separate each color component signal from the output signal. It will be done.

The separated color component signals are applied to an encoder 16 and 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 repetition frequency of red, blue, and green of the stripe filter, and then converted into a horizontal transfer pulse or a horizontal transfer pulse to generate it. It is also possible to perform synchronous detection using a reference signal obtained by processing the drive pulse to obtain a color difference signal.

However, according to these color signal separation methods,
Since stripe filters of three colors are used and corresponding photosensitive elements must be provided, three times the number of elements is required to obtain the same resolution as a monochrome image pickup plate.

This means that three times the imaging area is required for colorization, but increasing the imaging area is accompanied by great difficulties in manufacturing, and a colorization method that requires as small an area as possible is required.

SUMMARY OF THE INVENTION An object of the present invention is to propose a color solid-state imaging device that can generate color video signals using frames using one or two solid-state imaging plates and can reduce the area of the required imaging section.

The invention basically consists of a set of photosensitive elements (for example a photosensitive element itself having spectral sensitivity characteristics or a combination of a color filter and a photosensitive element) that are sensitive to substantially two mutually different colors along a horizontal line. A first row of photosensitive elements in which a set of photosensitive elements is repeatedly provided and a second row of photosensitive elements in which sets of photosensitive elements that are substantially sensitive to two mutually different colors are repeatedly provided along a horizontal line are alternately arranged in the direction of vertical readout. At the same time, in continuous horizontal scanning, a first color signal is transmitted from the first photosensitive element column, and a second color signal is transmitted from the second photosensitive element column.
The color signals are read out alternately as output signals, and a part of the output signals is delayed for one horizontal period, and the color signals that are generated alternately for each horizontal scan are pre-determined by a circuit having two modes that are switched for each horizontal scan. By performing predetermined processing, two different color difference signals can be obtained at the same time.

Although the luminance signal can be extracted using another solid-state image pickup plate, it can also be obtained from the low-frequency component of the output signal.

Therefore, for example, it can be used as a single-plate color solid-state imaging device using only one solid-state imaging plate as shown in FIG. This makes it possible to make the device even smaller than the previous device.

The present invention will be described below using Examples.

4 to 6 are diagrams showing one embodiment of a color solid-state imaging device according to the present invention. In FIG. 4, a mosaic-like color filter as shown is superimposed on the solid-state imaging plate shown in FIG. 1. This figure shows the imaging unit placed at the top of the screen.

In the figure, the photosensitive element group and the vertical transfer stage are omitted to simplify the drawing.

In the figure, 21 is a color filter element that passes each color component light of red (R) and 22 is a color filter element that passes each color component light of cyan (Ci).
They are arranged alternately and repeatedly along the line 5.

Further, 23 is a color filter element that passes blue (B) and yellow (Ye) color light, and these elements are similarly arranged alternately along a horizontal line 26 shown by a dotted line.

As is clear from Figure 4, the color filter is horizontal line 2.
The rows of color filter elements along lines 5 and 26 are
They have a configuration in which they are alternately and repeatedly arranged in the vertical reading direction.

In the area under each color filter, photosensitive elements for 1 bit or 2 bits in the case of interlace scanning are provided corresponding to each color filter element.

The amount of signal charge corresponding to the strength of the light that has passed through each color filament element accumulated in the photosensitive element group is transferred to the corresponding position of each vertical transfer stage every fixed period (one frame or l field). .

This signal charge is transferred line by line in the vertical read direction shown by the arrow 27 by a vertical transfer pulse generated during the horizontal blanking period, and read into the corresponding position of the 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, and an output signal 29 is obtained via a signal charge detection section 283.

FIG. 5 shows one horizontal scanning signal obtained when equal white light is projected onto all the color filters arranged as described above.

Figure A shows the output signal obtained by one horizontal scan corresponding to, for example, position 25 shown in Figure 4, as El(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 El(t).

Further, the opening in the same figure is the output signal E2 (t) obtained by one horizontal scan obtained corresponding to position 26 in FIG.
).

Since cyan Ci 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. 5 is obtained.

When the repetition angular frequency of the color filter in the horizontal direction is ω, El (t>) is shown in Figure 5, A2.

If the output signal obtained by each horizontal scan of E2(t) is subjected to Fourier expansion, it can be expressed as follows.

E,(t) and E2(t) are obtained alternately for each successive horizontal scan.

An example of a configuration for generating color signals from these output signals is shown in FIG.

In the figure, numeral 31 is a color solid-state image pickup plate provided with the color filter array as described above, which corresponds to the one shown in FIG.

Reference numeral 32 denotes a transfer lock generation circuit that generates a vertical transfer lock pulse φ■ and a horizontal transfer lock pulse φH for driving the color image pickup plate 31.

33 is a sampling separation circuit which repeats R (or B) and C1, that is, B+G (or Y
e, ie, G+R) component.

Here, the transmission characteristic of the color filter is R for the white signal.
It is assumed that the design is such that the amplitudes of the (or B) component and the Ci (or Ye) component are approximately equal.

A color difference signal is obtained from the separated two signals by a subtraction circuit 34, which is demodulated by a single low-pass filter 35 to obtain a color difference sequential signal in which the R-Ci signal and the B-Ye signal are repeated for each continuous horizontal scan. It will be done.

On the other hand, the luminance signal is extracted by passing the output signal of the color image pickup plate 31 through a low-pass filter 36.

Reference numeral 37 indicates a color encoder suitable for this embodiment, and 38 is a modulator that modulates a color difference signal with a carrier wave from a fixed oscillator 39 of 3.58 MHz, which performs one horizontal scan in synchronization with the vertical transfer lock pulse φV. 90° phase shifter every 4
A modulated color difference signal is obtained by switching between the signal through which 0 is passed and the switch circuit 41.

The output signal of the modulator 38 is transmitted to the IH delay line 4.
2 and the adder 43 to obtain two color difference signals at the same time.

These color difference signals and luminance signals are added together in an adder 44 to obtain a color standard signal.

In the case of this embodiment, R-Ci taken out for each horizontal scan
The phase of the carrier wave that modulates the signal or the B-Ye signal is switched every horizontal scan in correspondence with each color difference signal by the switch circuit 41, and color difference sequential modulation is performed with carriers whose phase differs by 900 times per horizontal scan. A signal is obtained and converted into a simultaneous signal by an IH delay line 42 and an adder 43, thereby obtaining a carrier color signal that is substantially orthogonally modulated.

In this embodiment, a sampling separation circuit is used for signal separation, but it goes without saying that a synchronous detection circuit can also be used.

In this case, a reference pulse having a frequency of 1/2 of the horizontal transfer pulse φ□ is created, and the color image pickup plate 3
The output is passed through a bandpass filter and synchronously detected using a reference pulse.

If the detection output is passed through a low-pass filter, a color-difference sequential demodulated signal corresponding to the output of the low-pass filter 35 (FIG. 6, 77) is obtained.

As is clear from the above embodiments, the color solid-state imaging device according to the present invention includes a first photosensitive element row in which a set of photosensitive elements sensitive to two mutually different colored lights is repeatedly provided;
This system uses an imaging means in which a second photosensitive element column and a second photosensitive element column different from the first photosensitive element column are provided alternately in the vertical direction, and different color signals are generated line-by-line by continuous horizontal scanning. A color solid-state imaging device using a small single imaging plate can be realized.

Furthermore, a means for converting line sequential signals read out from the imaging means into simultaneous signals is provided at a stage subsequent to the color signal demodulation stage, so that the signals as sequential signals are processed by one circuit up to the color signal demodulation stage. Because it is
This method has the advantage that different color signals can be processed up to color demodulation using a single circuit, and there is no need to consider variations in demodulation circuits, unlike when converting line sequential signals to simultaneous signals before demodulation.

Therefore, it is possible to obtain good simultaneous color signals without distortion due to variations.

[Brief explanation of the drawing]

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 color filter, and Figure 3 is a diagram showing the color filter shown in Figure 2. FIG. 1 is a block diagram of a conventional color solid-state imaging device that obtains color signals by overlapping it on a solid-state imaging plate; FIG. 4 is a block diagram showing a color imaging plate in an embodiment of the color solid-state imaging device according to the present invention; Figure 5 a. The mouths are a diagram showing the output signal of the image pickup plate in Figure 4 and Figure 6, respectively.
The figure is a block diagram of a signal processing circuit for generating color signals in the same embodiment. 21-24...--Color filter element,
31...--Color image pickup plate, 32...--Transfer lock generation circuit, 33...--Sampling separation circuit, 34---Subtraction circuit, 35...-- ...Low pass filter, 38... ...-modulator, 42---IH delay line,
43・-. - Addition circuit.

Claims (1)

[Claims] 1. A first photosensitive element row in which a set of photosensitive elements sensitive to substantially two mutually different colored lights is repeatedly provided along a horizontal line; The first
an imaging means formed by alternately and repeatedly arranging photosensitive element rows and different second photosensitive element rows in a vertical readout direction; means for generating a readout line sequential signal by alternately outputting second color signals from the second photosensitive element array; and a single means for demodulating the line sequential signal alternately containing the first and second color signals. A color solid-state imaging device comprising demodulation means, delay means for one horizontal scanning period provided after the demodulation means, and means for generating simultaneous signals from the input and output of the delay means.