JPS62217763A - Color solid image sensor - Google Patents

Abstract

PURPOSE:To reduce the color shade of fine high frequency components on an original and the color noise of information, to miniaturize a device and to cut down its cost by alternately arranging plural color filters on photoelectronic conversion elements comprising one unit line sensor among plural said sensors. CONSTITUTION:Due to a scan in a direction Y the 1st unit line sensor 2a photoelectrically converts an optical image from the original, and after a slight delay the 2nd unit line sensor 2b photoelectrically converts an image in a similar way, thereby outputting picture signals. The filters G1-Gn being the 1st color filter are continuously arranged on the photoelectronic conversion elements 3 in the sensor 2a at a pitch of one picture element. The 2nd color filters R1-Rn and the 3rd color filters B1-Bn are alternately arranged on the elements 3 of the sensor 2b in a main scan direction at every two elements. Thus all the picture elements can alternately obtain light transmitting the 1st filters G1-Gn, light transmitting the 2nd filter and light transmitting the 3rd filter at every two picture elements, whereby the color noise and color shade can be suppressed without dropping the resolution of a luminance signal, and simultaneously the device can be miniaturized at an inexpensive cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a color solid-state image sensor, and particularly to a color solid-state image sensor using a line image sensor as a unit sensor.

(Prior Art) Conventionally, as a color solid-state image sensor used in a two-dimensional color original M reading device, a dot-sequential array in which color separation color filters (hereinafter referred to as color filters) are arranged dot-sequentially on one line sensor is used. What is called a sensor (Japanese Patent Application Laid-Open No. 5
8-178659) is known. However, in dot-sequential array sensors, color filters of three colors RGB are arranged dot-sequentially on one pixel. When there is a change, there is a problem in that the output balance of the three color filters changes and color noise occurs.

Therefore, three line sensors are arranged in parallel at predetermined intervals in the sub-scanning direction, and each color is separated by these three line sensors. According to this method, an image at an arbitrary position in the main scanning direction can always be separated by three color filters, so that the above-mentioned color noise can be prevented from occurring.

However, when arranging three line sensors in parallel in this way, it is not possible to increase the packaging density due to the wiring and peripheral circuits of the line sensor placed in the center.
The distance between the three line sensors has to be increased.

Therefore, there is a drawback that a large amount of correction line memory is required to correct the reading deviation in the 1i311 scanning direction.

In addition to this, there is a method in which, for example, three primary color light sources are switched and images separated by these light sources are formed on one monochrome line sensor, but this method is difficult to control the light sources, and Furthermore, there are problems such as color unevenness due to instability in the rise of the light source.

(Problems to be Solved by the Invention) As described above, conventional color solid-state image sensors have problems such as color noise and color unevenness, and the inability to reduce size and cost.

Based on these points, the present invention reduces color noise and color unevenness in minute high-frequency components and information of a document, and is compact and compact.
The purpose of the present invention is to provide a color solid-state image sensor that can be inexpensive.

[Structure of the Invention] (Means for Solving the Problems) In this invention, first and second unit line sensors are arranged in parallel, and the first to second unit line sensors are placed on the photoelectric conversion elements of these two unit line sensors. The 3 color filters are arranged as follows. That is, the first color filter is always disposed on the photoelectric conversion element of either the first or second unit line sensor, regardless of the position in the main scanning direction. Further, the second and third color filters are alternately arranged every other pixel in the main scanning direction on the photoelectric conversion element where the first color filter is not arranged.

(Function) In general, the spatial frequency characteristic (MTF) at the human visual angle is
It has already been shown that chromatic colors are inferior to achromatic colors (for example, Haruo Sakata, Institute of Electronics and Communication Engineers Image Study Group Material IE75-92.P37.1976
). The present invention utilizes such human visual angle characteristics.

That is, in the present invention, signals transmitted through the first color filter are obtained for all pixels in the main scanning direction. Further, signals transmitted through the second and third color filters are obtained every other pixel in the main scanning direction. Therefore, if the transmitted light of the seventh color filter is mainly used to generate the luminance signal, and the transmitted light of the first to third color filters is used to generate the color difference signal, the horizontal resolution of the luminance signal can be changed to the color difference signal. It is possible to double the resolution of , and with an efficient sensor configuration, it is possible to secure a level of resolution that poses no practical problem from the perspective of human viewing angle characteristics.

On the other hand, from one pixel position in the main scanning direction, either the first and second color filters or the first and third color filters ensure that a color difference signal without color noise is obtained. Therefore, a color difference signal with suppressed color noise can be obtained. In this case, the resolution of the color difference signal is 1/2 of the resolution of the luminance signal, which can practically satisfy the viewing angle characteristics of humans, as described above.

(Example) FIG. 1 shows an example of the present invention. In the figure, a first unit line sensor 2a and a second unit line sensor 2b are arranged in parallel on a semiconductor substrate 1 at a distance of OR in the sub-scanning direction (Y direction). These two unit line sensors 2a.

2b is formed by linearly arranging n photoelectric conversion elements 3 made of, for example, PN junction photodiodes at a predetermined element pitch p in the main scanning direction (X direction).

On each photoelectric conversion element 3 of the first unit line sensor 2a, a G (green) filter G1. G2, G3, . . . , Gn are successively arranged at a one-element pitch. Further, on each photoelectric conversion element 3 of the second unit line sensor 2b, R (red) filters Rt, R2, -, which are second color filters are provided.
RIM (however, m-n/2), and a B (blue) filter S1. which is a third color filter. B2...
3n+ are arranged alternately at every other pixel. The spectral transmission characteristics of these R, G, and B filters are shown in FIG. The G filter shows high transmittance in a wide wavelength range.

On the other hand, each unit line sensor 2a is mounted on the semiconductor substrate 1.
, 2b1. :il, the vertical charge transfer section 4a,
4b, and a charge transfer type shift register 5a.

5b are arranged. Vertical charge transfer section 4a.

4b transfers the charge generated in each photoelectric conversion element 3 of each unit line sensor 2a, 2b to charge transfer type shift register 5a, 5.
b. Further, the charge transfer type shift registers 5a and 5b transfer the charge of each pixel transferred in parallel via the vertical charge transfer sections 4a and 4b to the output sections 6a and 6.
This is for serially outputting an image signal via a predetermined clock signal.

By the way, both unit line sensors 2a, 2bl! H distance 1
It is generally desirable that 1DR be an integral multiple of the reading pitch in the Y direction. The smaller this coefficient is, the smaller the capacity of the line memory for correction is required. In the present invention, the element pitch p of the photoelectric conversion elements 3 corresponds to the pixel pitch in the X direction.
Both unit line sensors 2a and 2b can be brought close to each other to the extent that the values are equal to each other, and one line of line memory for correction is sufficient.

Next, the operation of the color solid-state image sensor according to this embodiment configured as described above will be explained.

An optical image from a document (not shown) is first photoelectrically converted by the first unit line sensor 2a as it is scanned in the Y direction.
It is serially outputted from the output section 6a via the vertical charge transfer section 4a and the I-charge transfer type shift register 5a. This image signal is stored in a line memory (not shown) for correction. On the other hand, a little later, the second unit line sensor 2b also photoelectrically converts the optical image of the same portion. Then, an image distortion signal is outputted via the vertical charge transfer section 4b and the charge transfer side shift register 5b.

Next, distribution and rearrangement of the signals of each pixel is performed using these two signals. That is, as shown in FIG. 2, the signal obtained by the first unit line sensor 2a is transmitted through the filter G1. G2
, G3, . . . , Qn, and the signal 1q transmitted by the second unit line sensor 2b is filtered by filters R1, Sl, R2, and 82.

... is a transmitted signal. Therefore, two pixel signals having the same X-direction position of the first and second unit line sensors 2a and 2b, and a shift of one element pitch p to the right with respect to the above-mentioned X-direction position of the second unit line sensor 2b. The RGB signal of one pixel is obtained from the pixel signal at the position. Then, using these RGB signals, (R+G+8)
The brightness signal is obtained by the calculation /3 (R-G).

Two color difference signals can be obtained by the calculation (B-G).

By the way, noise in color difference signals, which is a problem in conventional dot sequential array sensors, is a problem caused by not color-separating the same pixels. According to this embodiment, since for the same pixel, either the R signal or the B signal is always color-separated from the G signal, color difference noise can be reduced more than before.

On the other hand, brightness signals require high resolution due to the characteristics of human viewing angles, but in the present invention, since the transmitted light of the G filter, which has the highest sensitivity, is obtained for all pixels, it is possible to increase the resolution of brightness signals. can.

At this time, if the ratio of the light transmitted through the G filter to the R+G+B signal is increased, a read signal of even higher quality can be obtained.

Furthermore, since only two unit line sensors are used, the number of photoelectric conversion elements can be reduced to 2/3 compared to the conventional dot sequential method or 3 line method, thereby improving the overall yield. Moreover, even when wiring and peripheral circuits are taken into account,
Since the two line sensors can be placed close to each other, the number of line memories for correction can be reduced. Furthermore, in this embodiment, since the G filter is formed continuously on the first unit line sensor 2a, it is easier to form the filter than when other colors are arranged dot-sequentially. There are great process benefits. As a result, the device can be made smaller and less expensive.

Note that the present invention is not limited to the embodiments described above. For example, in the above embodiment, the G filter is formed continuously on the first unit line sensor 2a, but the G filter is formed continuously on the first unit line sensor 2a.
As shown in the figure, G filters are alternately arranged in a staggered manner every pixel (or every several pixels) on the first and second line sensors 2a and 2b, and the other photoelectric conversion elements 3 An R filter and an 8-filter may be arranged on every other pixel. Even with this arrangement, transmission signals of the G filter can be obtained for all pixels in the main scanning direction. An example of the distribution rearrangement at this time is shown in FIG.

Furthermore, as shown in FIG. 5, for example, the first unit line sensor 2a may be arranged offset from the second unit line sensor 2b by 1/2 of the element pitch p of the photoelectric conversion elements 3. good. In this case, the transmitted signals of the B filter and R filter are 1 with respect to the transmitted signal of the G filter.
/2 pixels overlap, so by rearranging the distribution as shown in FIG. 6, the G signal, which is the center of the color difference signal, is physically located at the center, so the color difference noise can be dispersed in a well-balanced manner. And the effect of reduction is not impaired.

Note that in each of the above embodiments, the G filter, R filter, and B filter are used as examples, but other color filters can also be used as the filters. For example, as shown in FIG. 8, a Y (yellow) filter may be used instead of the R filter, and a C (cyan) filter may be used instead of the B filter. Furthermore, G
It is also possible to use a W (white) filter instead of the filter.

In addition, the present invention provides a COD line sensor, a BBD line sensor, a photodiode, an M
Needless to say, the present invention can be applied to various things such as OS transistors. It goes without saying that the present invention can also be applied to a contact type sensor in which the color solid-state image sensor described above is used as one unit and a plurality of these units are arranged in a staggered manner.

[Effects of the Invention] As described above, according to the present invention, transmission signals of the first color filter are obtained for all pixels, and transmission signals of the second and third filters are obtained alternately for every other pixel. Therefore, it is possible to suppress the occurrence of color noise and color unevenness without reducing the resolution of the luminance signal.

Also, since only two unit line sensors are used,
The overall number of elements can be reduced, yields can be improved, and restrictions on wiring and peripheral circuits can be eliminated, so packaging density can be increased. Therefore, only a small amount of line memory for correction is required, and the device can be made smaller and less expensive.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the configuration of a color solid-state image sensor according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing an example of distribution and rearrangement of signals read by the image sensor, and FIG. A plan view showing the configuration of a color solid-state image sensor according to another embodiment of the invention, FIG. 4 is a schematic diagram showing an example of distribution and rearrangement of signals read by the image sensor, and FIG. FIG. 6 is a schematic diagram showing an example of distribution and rearrangement of signals read by the image sensor, and FIG. 7 is a plan view showing the configuration of a color solid-state image sensor according to an embodiment of the present invention. FIG. 8 is a characteristic diagram showing the spectral transmission characteristics of an RGB filter, and FIG. 8 is a characteristic diagram showing the spectral transmission characteristics of a YGC filter, which can be considered as another example. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2a... 1st unit line sensor, 2b... 2nd unit line sensor, 3... Photoelectric conversion element, 4a, 4b... Vertical charge transfer part, 5...・・・
Charge transfer type shift register, 6a, 6b...output section. Applicant's representative Patent attorney Takehiko Suzue - Figure 2 Figure 4

Claims (8)

[Claims] (1) First and second unit line sensors each consisting of a plurality of photoelectric conversion elements arranged in a straight line that generate electrical signals in response to light are arranged in parallel, Also, a first color filter is arranged on the photoelectric conversion element of either one of the first and second line sensors, and a second color filter is arranged on the photoelectric conversion element on which the first color filter is not arranged. A color solid-state image sensor characterized in that a filter and a third color filter are alternately arranged every other element in the main scanning direction. (2) The first color filter is a green filter, the second
2. The color solid-state image sensor according to claim 1, wherein the color filter is a red filter, and the third color filter is a blue filter. (3) The first color filter is a green filter, the second
2. The color solid-state image sensor according to claim 1, wherein the color filter is a yellow filter, and the third color filter is a cyan filter. (4) The first color filter is arranged continuously in the main scanning direction on the photoelectric conversion element of the first unit line sensor, and the second and third color filters are arranged on the photoelectric conversion element of the first unit line sensor. The color solid-state image sensor according to claim 1, wherein the color solid-state image sensor is arranged alternately at every other pixel on the photoelectric conversion element. (5) Claims characterized in that the first unit line sensor and the second unit line sensor are arranged such that their corresponding photoelectric conversion elements are at the same position in the main scanning direction. The color solid-state image sensor according to item 1. (6) The first unit line sensor and the second unit line sensor are characterized in that their corresponding photoelectric conversion elements are arranged such that they are shifted from each other by 1/2 element pitch in the main scanning direction. A color solid-state image sensor according to claim 1. (7) The first unit line sensor and the second unit line sensor are arranged at a distance that is an integral multiple of the reading pitch in the sub-scanning direction.
Color solid-state image sensor as described in section. (8) A color solid-state image sensor according to claim 1, wherein the first unit line sensor and the second unit line sensor are arranged adjacent to each other on the same semiconductor substrate.