JPH01204587A - Solid-state image pickup element for color - Google Patents

Abstract

PURPOSE:To obtain an output signal with white balance arranged by providing a charge storage time of a pixel corresponding to each color different from a color temperature. CONSTITUTION:A vertical transfer path 12 of a photodetection section 10 consists of plural transfer electrodes 13, 14 of 2-layer polysilicon structure prolonged along the horizontal direction and the two transfer electrodes 13, 14 are provided corresponding to one pixel. Moreover, a transfer gate TG provided between a photodiode 11 and the vertical transfer path 12 is used in common by the transfer electrodes 13, 14 and a different transfer electrode is assigned from each color in one horizontal row. That is, the electric charge corresponding to the pixel or color B or R is read by the transfer gate made of the 1st transfer electrode 13, and the charge of the color G is read by the transfer gate made of the 2nd transfer electrode 14. Thus, an output with white balance arrangement is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color solid-state image sensor, and more specifically, the charge accumulation time of a pixel corresponding to each color of a color filter can be changed according to the color temperature. FIT, which improves the apparent color balance and expands the dynamic range.
This invention relates to solid-state image sensing devices.

[Prior Art] Conventionally, electronic photographic devices such as electronic still cameras and video cameras perform white balance adjustment by signal processing of the output from an image sensor such as a solid-state image sensor.
Recording image signals.

As shown in FIG. 8, a color solid-state imaging device in which a micro color filter is arranged on each pixel
Since the saturation level of each color signal to be photoelectrically converted differs depending on the color temperature, the light range that can be used as a color sensor from the viewpoint of color balance is the color with the lowest saturation level, for example color R.
It is adjusted to

[Problems to be Solved by the Invention] For this reason, color solid-state image sensors cannot use the entire dynamic range when compared to monochrome sensors that do not have color filters. This made photographing the subject extremely difficult.

As a result of extensive research, the inventor of the present invention found that if the charge accumulation time of pixels corresponding to each color of a color filter can be controlled according to color temperature, a color-balanced output can be obtained and the dynamic range can be expanded. The present invention has been achieved by paying attention to the above.

That is, an object of the present invention was made in view of the above circumstances, and is to provide a color solid-state image pickup device that outputs a white-balanced signal, simplifies the signal processing circuit, and expands the dynamic range. There is a particular thing.

Furthermore, it is an object of the present invention to provide a color solid-state imaging device that causes less smearing and can also provide output for a video camera by implementing the present invention with a device having an FIT (frame interline) configuration.

[Means for Solving the Problems] The above object of the present invention is to provide a light receiving section having a vertical transfer path attached to each vertical column of photoelectric conversion elements arranged in a matrix; T! 14j storage section and a horizontal transfer path,
In the FIT-type color solid-state imaging device in which a micro color filter is arranged on the photoelectric conversion element, horizontal pixels corresponding to color filters of the same color are respectively connected to a vertical transfer control unit via a common transfer gate. The light-receiving section is formed by a color solid-state image sensor that is repeatedly scanned by driving signals having different phase differences depending on the color temperature, and the pixels accumulate charges for a predetermined charge accumulation time for each color. achieved.

[Operation] By connecting pixels of the same color to a common transfer gate and reading out the charge accumulation time of each color by changing it according to the color temperature,
Output with good white balance can be obtained. Also, FI
Since the T-type device allows high-speed vertical charge transfer, the occurrence of smear can be reduced.

[Example] Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing an FIT type color solid-state image sensor based on one embodiment of the present invention.

In the figure, this color solid-state image sensor 100 includes a light receiving section 10 shown as one block, a charge storage section 20 that temporarily stores signal charges formed in the light receiving section 10, and an output of the charge storage section 20. a horizontal transfer path 30 disposed along the horizontal direction at the end; and a discharge drain 4 disposed at the end of the light receiving section 10 to face the horizontal transfer path 30.
0, and two vertical shift registers 50 . G.

It is equipped with

The light receiving section 10 is composed of photodiodes 11 arranged in a matrix and vertical transfer paths 12 arranged in parallel for each vertical column of the photodiodes 11, and is different from a conventional interline transfer structure device and path. It is provided between.

In the figure, two vertical rows of photodiodes 11 are shown.
Only the vertical transfer path 12 attached thereto is shown in a simplified manner.

The charge storage section 20 consists of a transfer channel 21 connected to the light receiving section 10, and is provided in the same manner as a conventional frame transfer structure device.

FIG. 2 shows the light receiving section 10 in an enlarged manner.

On the photodiode 11 corresponding to each pixel, micro color filters of three primary colors indicated by symbols R, G, and B are arranged as shown in the figure.

The vertical transfer path 12 in the light receiving section IO includes a plurality of transfer electrodes 13 having a two-layer polysilicon structure and extending in the horizontal direction.
．． 14, and 2 pixels correspond to 1 pixel.
Book transfer electrodes 13.14 are arranged.

Further, a transfer gate T is provided between the photodiode 11 and the vertical transfer path 12 . are used for Ak by the transfer electrodes 13 and 14, and different transfer electrodes are assigned to each color in one horizontal row. That is, in this embodiment, charges corresponding to pixels of color B and R are read out by a transfer gate formed by the first transfer electrode 13, and charges of color G are read out by a transfer gate formed by the second transfer electrode 14. be done.

The transfer electrodes 13 and 14 are connected to the vertical transfer control section 50°6.
0 and are driven in four phases, with four vertically adjacent wires forming a set.

Note that the vertical transfer path 12 has a channel sensor 15.
separated from adjacent channels by

Next, an example of a readout operation when the color solid-state image sensing device of the present invention configured as described above is applied to a video camera will be described with reference to FIGS. 3 and 4.

Note that this example describes the case where the color temperature is high, and the charge accumulation time corresponding to each color is TR>TG>T.
The respective shutter times are set so as to have the relationship B.

In FIG. 3, the light receiving section 10 has a row of color filters arranged horizontally in the order of CBCB..., GRGR, etc.
It consists of a so-called G stripe R/B line sequence in which columns arranged in the order of . . . are arranged alternately in the vertical direction.

The image signal readout operation is carried out by one vertical shift register 5.
The transfer electrodes 13 and 14 are driven by control from zero. That is, the signal charge formed by each photodiode 11 is transferred to a predetermined transfer electrode (transfer gate) T to which a voltage V11 higher than that during vertical transfer is applied. ) to the vertical transfer path, and then the transfer electrode 13.1
Transfer voltage V applied to 4. After being transferred in parallel to the storage section 20, the storage section is read out in the scanning order. At that time, from the light receiving unit IO to the storage unit 20
Vertical transfer of signal charges to is performed, for example, twice at high speed during one exposure period. As a result, signal charges of two fields are read out and a field image is formed.

On the other hand, prior to the above read operation, a reset operation is performed on each pixel of the light receiving section. This reset operation is based on the above-mentioned relationship, T
This is done so that R>TG>TB, and the light receiving section 10 is scanned by the drive signal from the other vertical shift register 60. At this time, unnecessary charges are transferred in the counter-reading direction and are swept away to the discharge drain 40. Further, at this time, the light receiving section 10 scans from the row farthest from the discharge drain toward the discharge drain side.

The signal charges produced one after another as described above can form an optical image signal by changing the accumulation time, that is, the shutter time, so that the output signal ratio remains constant even if the color temperature changes.

5 and 6 show another embodiment of the present invention having a color filter array for a digital camera.

Note that this example describes the case where the color temperature is low, and the charge accumulation time corresponding to each color is T R < T c
The respective shutter times are set so as to satisfy the relationship <T o.

In FIG. 5, the light receiving section 110 has color filters arranged as shown. First, the pixels corresponding to colors B and R are scanned after a predetermined shutter time has elapsed, and each charge is vertically transferred to the storage section 120.

Thereafter, each signal charge read out via the horizontal transfer path 130 is A/D converted and temporarily stored in the frame memo 70. After the signal charges of color B and color R are read out, the color G
The corresponding pixels are scanned in the same way, and after a predetermined shutter time has elapsed, they are vertically transferred and read out from the horizontal transfer path 130. This color G signal and the color B and color R signals in the frame memory are combined to form an image signal.

Note that FIG. 6 shows drive pulses when signal charges are read out for each color, and FIG. 7 shows drive signals when color B and color R are read out simultaneously.

Further, in this embodiment as well, unnecessary charges are read out via the discharge drain 140 provided in the same manner as in the previous embodiment, but unnecessary charges are swept out along each vertical transfer path, for example. It is also possible to provide a horizontal overflow drain so that the overflow drain is sucked into the substrate through the drain.

[Effects of the Invention] As described above, according to the color solid-state imaging element of the present invention, the charge accumulation time of the pixel corresponding to each color is set to be different depending on the color temperature, so that the white balance can be adjusted. Therefore, a balanced output signal can be obtained, and the external signal processing circuit can be simplified. Further, since it is possible to set the accumulation time for each color and select the amount of light up to the saturation level of each color, the dynamics can be substantially improved. Furthermore, by implementing the present invention in a device with an FIT configuration, smearing is prevented and an output signal for a video camera is obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a color solid-state image sensor according to an embodiment of the present invention, FIG. 2 is an enlarged view of the light receiving section of the device shown in FIG. 1, and FIG. 3 shows a readout operation with filters arranged. FIG. 4 is a diagram showing the drive signal, FIG. 5 is a block diagram showing another embodiment, FIG. 6 and FIG. 7 are diagrams showing the drive signal, and FIG. 8 is a diagram showing the conventional It is a light amount-signal characteristic diagram in the element. 10, 110... Light receiving section 11... Photodiode 12... Vertical transfer paths 13, 14... Transfer electrodes 20, 120... Electric (='4 Accumulation section 30, 130
...Horizontal transfer path 40, 140...Ejection drain 50, 00...Vertical shift register 170...Frame memory QL,',: l 111)/-,,/

Claims (1)

[Claims] A light receiving section having a vertical transfer path attached to each vertical column of photoelectric conversion elements arranged in a matrix, a charge storage section and a horizontal transfer path, and a micro color filter arranged on the photoelectric conversion element. In a FIT-type color solid-state image sensor, horizontal pixels corresponding to color filters of the same color are respectively connected to a vertical transfer control section via a common transfer gate, and the light receiving section is controlled according to the color temperature. 1. A color solid-state image pickup device, characterized in that pixels are repeatedly scanned using drive signals having different phase differences to accumulate charge for a predetermined charge accumulation time for each color.