JPH0626410B2 - Color image sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image sensor for reading a color image, and more particularly to a color image sensor suitable for use as a scanner of a color printer.

[Conventional technology]

In recent color printers, color original images (color negative,
There is a scanner for scanning (color positive etc.), in order to create a print photograph with good density and color balance, the three color densities of each point of the original color image are measured, and the three colors of each point are measured. The density is used to control the red exposure amount, the green exposure amount, and the blue exposure amount for exposing the color paper during printing. A color image sensor, which is a solid-state imaging device, is used for the scanner. This scanner has a three-plate type with a color image sensor for red, a color image sensor for green, and a color image sensor for blue, and a red transmission area, a green transmission area, and a blue transmission area alternately for each color light to be measured. There is a single plate type in which the mosaic filter or the stripe filter formed in 1 is arranged on the light receiving surface of one image sensor.

The former three-plate type requires three drivers and optical systems in addition to the three color image sensors, which makes the structure complicated and costly. Therefore, the single plate type is advantageous in terms of cost and installation space.
This single plate type has one vertical scanning shift register,
Since each photoelectric conversion unit is sequentially scanned by one horizontal scanning shift register, signals of respective colors are taken out in a mixed form.

[Problems to be solved by the invention]

When measuring the three color densities of a color original image using the single-plate color image sensor described above, each photoelectric conversion unit measures different points, which essentially causes color registration. Can not be measured correctly. This poses a problem when controlling the three-color exposure amount in color printing in consideration of the tint of the pixel.

In general, color negatives taken by amateurs include not only frames that are properly exposed but also frames that are extremely over or underexposed, so to measure the density of images recorded on color negatives A dynamic range of about 10,000 steps is required. However, since the dynamic range of the color image sensor is narrow, if it is necessary to cover 10000 steps, it is necessary to reduce the change in signal level with respect to the change in the amount of incident light, which makes it impossible to perform highly accurate measurement. By the way, looking at only one frame recorded on a color negative, the signal level differs depending on the color, but about 100 steps for each color is sufficient. Therefore, if the charge accumulation time is changed for each color and the measurement is performed, the dynamic range is widened and a signal with less noise can be obtained. However, in the conventional color image sensor, the charge storage time cannot be set for each color.

An object of the present invention is to provide a color image sensor in which the charge accumulation time is set for each color in order to perform highly accurate measurement, and the occurrence of color registration is reduced.

[Means for solving problems]

To achieve the above-mentioned object, the color image sensor of the present invention comprises a plurality of blue vertical MOS transistors connected in series with each first photoelectric conversion unit, for example, a blue photoelectric conversion unit.
A switch, a plurality of green vertical MOS switches connected in series with each second photoelectric conversion unit, for example, a green photoelectric conversion unit, and each connected in series with each third photoelectric conversion unit, for example, a red photoelectric conversion unit. A plurality of third vertical MOS switches, a blue horizontal MOS switch provided for each N (integer of 3 or more) columns, and connected in series with the plurality of blue vertical MOS switches in the N column; A horizontal horizontal MOS switch for green, which is provided for each column and is connected in series with a plurality of vertical MOS switches for green in the N column, and a plurality of reds provided in the N column and provided for each N column. For vertical M
A red horizontal MOS switch connected in series with the OS switch, and a blue vertical scan switch for sequentially turning on the blue vertical MOS switches by M rows (M is an integer of 3 or more), and a green vertical MOS switch. Vertical scanning shift register for green which sequentially turns on every M rows, a vertical scanning shift register for red which sequentially turns on vertical MOS switches for red every M rows, and a horizontal MO of three colors in the same column.
It is composed of one horizontal scanning shift register that simultaneously turns on the S switch.

In order to eliminate color registration, the photoelectric conversion units arranged in the matrix are grouped into M × N units (M and N are integers of 3 or more), and this group constitutes one pixel measurement unit. The 1-pixel measuring unit includes n (M × N least common divisor and an integer of 3 or more) photoelectric conversion units for each color, and the signal charges accumulated in the n photoelectric conversion units are It is added and read. In order to add the signal charges in the one-pixel measuring unit, the vertical MOS switches connected to the n photoelectric conversion units are simultaneously turned on, and at the same time, one vertical MOS switch connected to the vertical MOS switches is also connected. The horizontal MOS switch is turned on, and the color signal is taken out from the output line connected to the drain of the horizontal MOS switch. This horizontal MOS switch is provided for every N columns for each color, and one horizontal scanning shift register simultaneously turns on the horizontal MOS switches for each color in the same column. Further, the vertical scanning shift register provided for each color is independently operated within a non-overlapping range to set the charge accumulation time (photoelectric conversion time) for each color. That is, in these vertical scanning shift registers, the vertical MOS switches are turned on at different timings for each color to read out the signal charges for each color.

Examples of the colored light include a combination of blue, green, and red, a combination of cyan, magenta, and yellow, and the present invention can be used for any of these combinations. Various colors such as skin color may be added.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

〔Example〕

In FIG. 2 showing an example of an array of photoelectric conversion units of a color image sensor, a color image sensor 2 photoelectrically converts red light and accumulates the obtained signal charges. A green photoelectric conversion unit 4 for accumulating signal charges obtained by conversion and a blue photoelectric conversion unit 5 for accumulating signal charges obtained by photoelectric conversion of blue light are alternately arranged regularly. The red photoelectric conversion unit 3,
As is widely known in this field, the photoelectric conversion unit 4 for green and the photoelectric conversion unit 5 for blue are composed of equivalently represented photodiodes and a color filter for selectively transmitting specific color light. ing. In this embodiment, a red filter, a green filter, and a blue filter are used as the color filters. The red photoelectric conversion unit 3 is composed of a red filter and a photodiode, and the green photoelectric conversion unit 4 is composed of a green filter and a photodiode. Also,
The blue photoelectric conversion unit 5 is composed of a blue filter and a photodiode.

When the one-pixel measuring unit is composed of one photoelectric conversion unit for each color, the photoelectric conversion units for each color measure different points on the color original image, and thus the influence of color registration becomes large. In order to eliminate this color registration, photoelectric conversion units are grouped into M rows and N columns (M and N are integers of 3 or more), and one pixel measurement unit is configured by M × N photoelectric conversion units.
If the signal charges of the photoelectric conversion units of the same color are added and read in the one-pixel measurement unit, it is possible to perform three-color separation photometry that does not substantially affect the exposure control of the color printer. In this embodiment, groups are made every 3 rows and 3 columns, and 3
Red photoelectric conversion unit 3 and three green photoelectric conversion units 4
The three photoelectric conversion units 5 for blue constitute a one-pixel measuring unit 2a. In the drawing, one photoelectric conversion unit 3 to 5 is surrounded by a dotted line, and one pixel measurement unit 2a is surrounded by a solid line.

FIG. 1 shows a circuit of the color image sensor of the present invention. In an actual color image sensor, each electronic element is integrated on a semiconductor chip, but they are shown equivalently in the drawings. Photodiodes 11 to 15, 21 to 25, 31 to 35, 41 to 44 for photoelectrically converting the light transmitted through the color filter described above are arranged in a matrix, and the signal charges obtained by this photoelectric conversion are floated. Store in the capacitor. Here, the photodiodes 11, 14, 23, 32, 35,
41 and 44 are for red, and the photodiodes 12 and 1 are
5, 21, 24, 33 and 42 are for green, and the photodiodes 13, 22, 25, 31, 34 and 43 are for blue. Vertical MOS switches 51 to 55, 61 to 65, 71 to 75, 81 to 84 are connected in series to the respective photodiodes in order to read out the signal charges accumulated in these photodiodes.

A blue vertical scanning shift register 91a, a green vertical scanning shift register 91b, and a red vertical scanning shift register 91c are provided in order to set the charge accumulation time for each color. Further, if the charge accumulation time is set so that the reading of color signals does not overlap for each color, one horizontal scanning shift register 92 can be used in common, which is advantageous in simplifying the structure. Is. The shift registers 91a to 91c, 92 are controlled by a controller 93. Reference numeral 94 is a pulse generator for supplying a pulse to the controller 93.

Turn on the vertical MOS switches 51 to 55 in the first row for each color
In order to make the horizontal line 101a for blue and 101 for green
b, a red color 101c is provided. The gate of the blue vertical MOS switch 53 is connected to the blue horizontal line 101a, and the gates of the green vertical MOS switches 52 and 55 are connected to the green horizontal line 101b. Further, the gates of the red vertical MOS switches 51 and 54 are connected to the red horizontal line 101c.

Further, in order to turn on the vertical MOS switches 61 to 65 in the second row for each color, three horizontal lines 102a to 102c are used.
Is wired. Since the same applies to the third and subsequent lines, only the reference numeral is given and the description thereof is omitted.

Three vertical lines are provided for each column of the photodiode matrix in order to extract the color signals in a separated form for each color. That is, the blue vertical line 111a, the green vertical line 111b, and the red vertical line 11 are provided in the first column.
1c is wired. The drain of the blue vertical MOS switch 71 is connected to the blue vertical line 111a, and the green vertical MOS switch 71 is connected to the green vertical line 111b.
The drain of the switch 61 is connected. The red vertical lines 111c are connected to the red vertical MOS switches 51, 81.
The drain of is connected. It should be noted that the vertical lines in the second and subsequent columns are given only the reference numerals and the description thereof will be omitted.

Since the 1-pixel measuring unit 2a is configured by 3 rows and 3 columns, the three blue horizontal lines 101 in the 1st to 3rd rows are arranged.
a, 102a, and 103a are connected and connected to the first-stage output terminal D1 of the blue vertical scanning shift register 91a. Although not shown in the figure,
Three lines are connected from the top and are connected to the corresponding output terminals of the blue vertical scanning shift register 91a. Similarly, the green horizontal lines 101b, 102b, 103b are connected and connected to the output terminal D1 of the first stage of the green vertical scanning shift register 91b. The red horizontal lines 101c, 102c, and 103c are connected to each other, and the first-stage output terminal D of the red vertical scanning shift register 91c is connected.
Connected to 1.

Since the one-pixel measuring unit 2a is composed of three columns, the blue vertical lines 111a, 112a, 113a are connected,
The horizontal MOS switch 121a for blue is connected to this in series. Similarly, the green vertical lines 111b and 112
b and 113b are connected to each other, and a green horizontal MOS switch 121b is connected in series thereto. Vertical line for red 1
11c, 112c, 113c are connected to each other, and a red horizontal MOS switch 121c is connected in series to this.
The gates of these horizontal MOS switches 121a to 121c are connected to the first output terminal F1 of the horizontal scanning shift register 92.

Similarly, for the 1-pixel measuring unit in the second column, in order to add and take out the signal charges for each color in the same 1-pixel measuring unit, the blue horizontal MOS switch 122a and the green horizontal M switch are also used.
OS switch 122b, red horizontal MOS switch 12
2c is provided. These horizontal MOS switches 1
Gates 22a to 122c are connected to the second output terminal F2 of the horizontal scanning shift register 92.

The drains of the blue horizontal MOS switches 121a and 122a are connected to the blue output line 125a, respectively. Similarly, green horizontal MOS switches 121b, 1b
The drains of 22b are connected to the green output line 125b, respectively. Red horizontal MOS switch 121c,
The drains of 122c are connected to the red output lines 125c, respectively.

Next, the operation of the above embodiment will be described with reference to FIG. First, the controller 93
Specify the green charge accumulation time and blue charge accumulation time respectively. The charge storage time is measured by pre-scanning each color light, and the charge storage time (photoelectric conversion time) is set so that the maximum value is close to the saturation value of the output value of the photoelectric conversion unit.
Is to determine. When the reading start signal for the main scan is input to the controller 93, the vertical scanning shift registers 91a to 91c provided for each color are simultaneously activated, and together with this, one horizontal scanning shift register 92 is activated. The accumulated signal charges of each color are simultaneously read out and reset at time t0. Since this signal is unnecessary, it is drained as it is without being taken into the computer.

After time t0, each photodiode photoelectrically converts incident light and accumulates the generated signal charge. Time t
When it reaches 1, the charge accumulation of red color is completed. Therefore, the controller 93 causes the vertical scanning shift register 91c for red color.
Then, a clock pulse is sent to the horizontal scanning shift register 92 to start reading the red signal. The red vertical scanning shift register 91c is a horizontal scanning shift register 92.
Each time the scanning is completed once, the vertical scanning pulse is shifted by one stage.

The red vertical scanning shift register 91c is first
The output terminal D1 of the stage is set to "H". At the same time, since the first output terminal F1 of the horizontal scanning shift register 92 becomes "H", the red horizontal lines 101a, 102a,
Red vertical MOS switch 51 connected to 103a,
63, 72 and the horizontal MOS switch 121c are turned on. As a result, the signal charges accumulated in the red photodiodes 11, 23, and 32 belonging to the one-pixel measurement unit in the first row, first column flow into the drain of the horizontal MOS switch 121c, so that each signal charge is added. Then, it is taken out from the red output line 125c.

The red signal extracted from the red output line 125c is sent from an A / D converter (not shown) and converted into a digital signal. This digital signal is sent to a logarithmic conversion table (not shown) where it is logarithmically converted. During this logarithmic conversion, the page corresponding to the charge accumulation time is selected,
The density value is converted into a correct density value in consideration of the charge accumulation time, and the obtained density value is loaded into the computer.

When the red signal is read from the 1-pixel measuring unit in the 1st row and 1st column, the horizontal scanning shift register 92 sets the second output terminal F2 to "H", so that the 1st row and 2nd column Of 1
A red signal is read from the pixel measuring unit. Thereafter, similarly, the red signal is sequentially read from the one-pixel measuring unit belonging to the first row.

When the reading of the red photodiodes in the first to third rows is completed, the red vertical scanning shift register 91c outputs a vertical scanning pulse from the second output terminal D2.
In this state, the horizontal scanning shift register 92 scans once as described above, and the signal charges accumulated in the photodiodes in the fourth to sixth rows are read out in the state of being added in the pixel. Thereafter, in the same manner, the red signal is sequentially read from the one-pixel measuring units on the third and subsequent rows. The reading of the red signal is performed during the time t1 to t2.

When the time t3 is reached, the green charge accumulation ends, so
The controller 93 is a vertical scanning shift register 91 for green.
Clock pulses are sent to the horizontal scanning shift register 92 and the horizontal scanning shift register 92, and the signal charges accumulated in the green photodiode are added and read in the one-pixel measuring unit. This green signal passes through the green output line 125b and is sent to the signal processing circuit described above. This green signal is taken out at time t
It is performed between 3 and t4.

When the time t5 is reached, the blue charge accumulation ends, so
The blue vertical output shift register 91a and the horizontal scan shift register 92 sequentially scan each pixel measuring unit, and the blue output line in a state where the signal charges accumulated in each blue photodiode are added in the pixel. It is sequentially taken out from 125a. This blue signal is read at time t
It is performed between 5 and t6.

In the above embodiment, the one connected to the horizontal line is called a vertical scan shift register, and the one connected to the vertical line is called a horizontal scan shift register. It is a point.

〔The invention's effect〕

As described above in detail, in the present invention, the photoelectric conversion units are grouped into M × N units, and the signal charges are added and taken out in this group, so that the occurrence of color registration is eliminated. You can Further, in the present invention, since the vertical scanning shift register is provided for each color in order to turn on the vertical MOS switch for each color, the charge accumulation time can be set for each color, thereby expanding the dynamic range. Highly accurate measurement can be performed. Furthermore, the present invention can simplify the structure because one horizontal scanning shift register is provided and commonly used for each color.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of a color image sensor of the present invention. FIG. 2 shows an arrangement example of photoelectric conversion units of the color image sensor of the present invention, in which one pixel measurement unit is composed of 3 × 3 photoelectric conversion units. FIG. 3 is a chart showing the timing of charge accumulation and signal reading in the embodiment shown in FIG. 2 ... Color image sensor 2a ... 1 pixel measuring unit 3 ... Red photoelectric conversion unit 4 ... Green photoelectric conversion unit 5 ... Blue photoelectric conversion unit 11 to 15, 21 to 25, 31 to 35, 41 ~ 44 ……
Photodiodes 51-55, 61-65, 71-75, 81-84 ...
Vertical scan MOS switch 101a, 102a, 103a, 104a ... Horizontal line for blue 101b, 102b, 103b, 104b ... Horizontal line for green 101c, 102c, 103c, 104c ... Horizontal line for red 111a, 112a, 113a, 114a ... Blue Vertical lines 111b, 112b, 113b, 114b ... Green vertical lines 111c, 112c, 113c, 114c ... Red vertical lines 121a, 122a ... Blue horizontal MOS switches 121b, 122b ... Green horizontal MOS switch 121c , 122c ... Red horizontal MOS switch.

Claims (4)

[Claims] 1. A first photoelectric conversion part for accumulating signal charges obtained by photoelectrically converting light in a first wavelength range, and a signal charge obtained by photoelectrically converting light in a second wavelength range. In the color image sensor, a second photoelectric conversion unit that stores the light and a third photoelectric conversion unit that stores the signal charge obtained by photoelectrically converting the light in the third wavelength region are arranged in a matrix. A plurality of first vertical MOS switches respectively connected in series with a first photoelectric conversion unit, a plurality of second vertical MOS switches respectively connected in series with each of the second photoelectric conversion units, and each of the third photoelectric conversions A plurality of third vertical MOS switches respectively connected in series with the section, and provided for each N (integer of 3 or more) columns, and connected in series with the plurality of first vertical MOS switches in the N columns. A first horizontal MOS switch, every N columns Provided, the second plurality within N columns
Second horizontal MOS connected in series with vertical MOS switch
A switch and a plurality of third switches provided in each of the N columns and arranged in the N column.
Third horizontal MOS connected in series with vertical MOS switch
A switch, a first vertical scanning shift register that sequentially turns on the first vertical MOS switch by M rows (M is an integer of 3 or more), and a second vertical MOS switch that sequentially turns on the second vertical MOS switch by M rows. Two vertical scanning shift registers, a third vertical scanning shift register for turning on the third vertical MOS switches in order of M rows in sequence, and one for simultaneously turning on the first to third horizontal MOS switches in the same column And a horizontal scanning shift register for the color image sensor. 2. The light in the first wavelength range is blue light,
The color image sensor according to claim 1, wherein the light in the wavelength range is green light and the light in the third wavelength range is red light. 3. Each of the photoelectric conversion units includes a filter that selectively transmits light in a specific wavelength range, and a photodiode that accumulates signal charges obtained by photoelectrically converting the color light that has passed through the filter. The color image sensor according to claim 2, wherein 4. The color image sensor according to claim 3, wherein each of the integers M and N is 3.