JP2592272B2 - Color solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid-state color image pickup device suitable for application to an electronic still camera. More specifically, the present invention relates to a color filter corresponding to each color according to a color temperature. The present invention relates to an interline CCD solid-state imaging device in which the accumulation time of a pixel can be changed, thereby achieving an apparent color balance and expanding a dynamic range.

(Prior art) Conventionally, electronic photographing devices such as an electronic still camera and a video camera perform white balance adjustment by signal processing of an output from an image sensor such as a solid-state image sensor.
The signal is being recorded.

In the color solid-state imaging device in which a micro color film is arranged on each pixel, as shown in FIG. 6, the saturation level of each photoelectrically converted signal differs depending on the color temperature. The color of the lowest saturation level that can be used as a color sensor from above,
For example, it is matched with the color R.

(Problems to be Solved by the Invention) For this reason, the color solid-state imaging device cannot use the entire dynamic range when used as a monochrome sensor without a color filter, and the dynamic range is narrowed to reduce the luminance difference. It made it very difficult to shoot large scenes.

The present inventors have conducted intensive studies and as a result, if the accumulation time of pixels corresponding to each color of the color filter can be limited according to the color temperature, it is possible to obtain a color balanced output and expand the dynamic range. Attention was paid to the achievement of the present invention.

That is, an object of the present invention is to provide a color solid-state imaging device for an electronic still camera in which the output is a signal with a white balance, the signal processing circuit can be simplified, and the dynamic range is expanded. Is to provide.

(Means and Actions for Solving the Problems) It is an object of the present invention to provide a liquid crystal display device in which horizontal signals of photoelectric conversion elements arranged in a matrix start at a predetermined time interval from a vertical transfer control unit. 1st and 2nd
Are sequentially selected and transferred in the vertical direction by the drive signal of
In the color solid-state imaging device provided so that the first drive signal is discharged to the discharge drain and the second drive signal is read out to the horizontal transfer path, one horizontal line of the micro color filter disposed on the photoelectric conversion element is provided. Pixels corresponding to two colors arranged on the line are connected to first and second polysilicon electrodes for performing four-phase driving for each color, and the polysilicon electrodes are controlled by a gate pulse control unit, and The transfer control unit includes a vertical CCD shift register and a switch unit including a plurality of MOSFETs, and a hue difference between the first and second drive signals is output to the plurality of MOSFETs according to a color temperature, and is output to the gates of the plurality of MOSFETs. This is achieved by a color solid-state imaging device characterized in that the time is provided differently for each color.

To limit the charge accumulation time in each pixel,
The present inventors have already proposed an interline transfer (IT) type CCD solid-state imaging device having little smear and an electronic shutter function (Japanese Patent Application No. 62-248136).

This solid-state imaging device sequentially selects and scans horizontal rows of photodiodes by two drive signals having phases shifted from each other by a predetermined time, sweeps out unnecessary charges by a first drive signal, and removes unnecessary charges by a second drive signal. It is provided to read out the stored charges. As a result, each horizontal line in the light receiving region operates so as to accumulate electric charges for a predetermined limited period, and a solid-state imaging device having a function equivalent to a so-called focal plane shutter is obtained.

According to the present invention, a white-balanced output can be obtained by connecting pixels of the same color to a common transfer gate electrode and reading the charge while changing the charge accumulation time of each color in accordance with the color temperature.

The present invention can be applied not only to three primary color filters but also to complementary color filters.

According to the present invention, a color sensor for an electronic still camera having a high dynamic range can be obtained.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a color solid-state imaging device suitable for being applied to an electronic still camera according to the present invention.

In the figure, a color solid-state imaging device 100 includes a photosensitive section 10 shown as one block, a horizontal transfer path 3 and a buffer arranged at the output end of the photosensitive section 10 via a storage gate 2 along the horizontal direction. An amplifier 4, a discharge drain 5 provided to face the horizontal transfer path 3 with the photosensitive section 10 interposed therebetween, a vertical transfer control section 6 for controlling the transfer of accumulated charges in the photosensitive section, and a gate pulse control section 7 And it consists of

The photosensitive section 10 includes photodiodes 11 arranged in a matrix, and vertical transfer paths 12 arranged side by side in columns of the photodiodes 11.

In the drawing, only one row of photodiodes 11 and a vertical transfer path 12 attached thereto are schematically shown.

FIG. 2 is an enlarged view of a main part of a color solid-state imaging device for an electronic still camera according to the present invention.

On the photodiode 11 corresponding to each pixel, micro color filters of three primary colors indicated by symbols R, G and B are arranged. In this embodiment, a column in which only G is arranged in the vertical direction and a column in which R and B are alternately arranged are arranged in a so-called G stripe R / B line sequence in which the columns are alternately arranged in the horizontal direction.

The vertical transfer path 12 of the photosensitive section 10 is provided by a plurality of transfer electrodes 21 and 22 of a two-layer polysilicon structure extending in the horizontal direction, and two transfer electrodes 21 and 22 corresponding to one pixel.
Is arranged. Further, the charge of the color G is read out to the vertical transfer path 12 by the first polysilicon electrode 21, and the charge of the color R or color B is read by the second polysilicon electrode 22.
To be read out to The transfer electrodes are 21, 22
Are connected to the vertical transfer control unit 6 and the gate pulse control unit 7, and are driven in four phases as a set of four vertically adjacent ones.

The vertical transfer path 12 is separated from an adjacent channel by a channel stopper 13.

The vertical transfer control section 6 is provided with a switch section 6a and a CCD shift register 6b. The switch section 6a includes two or three switch elements 61, 62, 63 having a common drain for each transfer electrode. It consists of connected switches. That is, switch elements 61 and 62 are connected to the first polysilicon transfer electrode 21, and switch elements 61, 62 and 63 are connected to the second polysilicon transfer electrode 22.
Each switch element is controlled by the vertical CCD shift register 6b or the gate pulse control unit 7.

That is, for example, the two MOSFETs forming the switch elements 61 and 62 connected to the k-th transfer electrode 21 are such that the gate of one FET is a vertical CCD shift register 6b and the gate of the other FET is a gate pulse control unit 7 And are connected respectively.

Each source is provided such that a drive pulse voltage V1 and a transfer gate pulse PG larger than the drive pulse voltage are applied. Therefore, the k-th transfer electrode 21 is controlled by the vertical CCD shift register 6b and the gate pulse control unit 7 by switching the conduction state of the switch elements 61 and 62, and transfers the color G field shift transfer gate. And acts as a vertical transfer electrode.

Next, three switch elements 61, 62 and 63 are connected to the (k-1) th transfer electrode 22 with a common drain, and the gates of the switch elements 61 and 62 are connected to the vertical shift register.
6b and the gate of the switch element 63 are the gate pulse controller 7
And are connected respectively. Each source is provided such that drive pulse voltages V2 and V4 and a transfer gate pulse PG higher than the drive pulse voltage are applied. Therefore, the (k-1) th transfer electrode 22 is switched by switching the conduction state of the switch elements 61, 62, 63,
Under the control of the vertical shift register 6b and the gate pulse control unit 7, they act as a field shift transfer gate and a vertical transfer electrode for the color R. Hereinafter, the same connection is performed, and the (k-2) th is used as the transfer gate and the transfer electrode for the field shift of the color G similarly to the kth, and
The third is used as a transfer gate and a transfer electrode for the field shift of color B.

Next, the operation of the color solid-state imaging device for an electronic still camera according to the present invention configured as described above will be described.

When the jitter mode is selected in the electronic photographing device to which the element of the present invention is applied, the photosensitive unit 10 is scanned by the first drive signal emitted from the vertical shift register 6b, and unnecessary charges accumulated in the photodiode 11 are removed. Drain 5
Swept away. At this time, the scanning of the photosensitive section 10 is performed from a row far from the discharge drain 5 toward the discharge drain. In this embodiment, when the gate pulse controller 7 scans the n-th polysilicon electrode 22 corresponding to the bottom row shown in FIG. The charge of the pixel corresponding to the color R among the photodiodes in the lower row is first transferred to the vertical transfer path 12.
Field-shifted. When the charge of the pixel corresponding to the color R is vertically transferred, the (n-1) -th polysilicon electrode 21 also corresponding to the bottom row of the photodiode is scanned by the gate pulse control unit 7, and similarly transferred. A higher gate pulse voltage PG is applied. As a result, the electric charge of the pixel corresponding to the color G among the photodiodes in the lowermost row is field-shifted, and then similarly vertically transferred by the first drive pulse to be discharged.
Is flushed out. Thereafter, similarly, the charge of the color B corresponding to the (n-2) th color is swept out, and the charges of the photodiodes in each row are sequentially swept upward to the discharge drain.

On the other hand, when a second drive signal having a phase delayed from the first drive signal by a predetermined period, that is, a phase corresponding to the shutter time, is issued from the vertical shift register 6b, the second drive signal becomes the first drive signal. The photosensitive section 10 is scanned upward from below so as to follow the row scanned by the drive signal. However, unlike the case of the first drive signal, the signal charge of each photodiode scanned by the second drive signal is transferred downward after being field-shifted to the vertical transfer path, and is transferred through the storage gate 2. It is sent to the horizontal transfer path 3. Further, each polysilicon electrode scanned by the second drive signal is driven so that the phase difference from the first drive signal, that is, the shutter time is different according to the color temperature.

That is, when the color temperature is high, the shutter has the characteristics as shown in FIG. 3A, so that the shutter time tr of the color R becomes longer than that of the colors B and G as shown in FIG. The transfer gate pulse PG is applied so that the accumulated charge is field-shifted. On the other hand, when the color temperature is low, the characteristics as shown in FIG. 4A are exhibited, so that as shown in FIG. B is set to be long, and the accumulated charges are field-shifted. Thereafter, the accumulated charges sent to the horizontal transfer path 3 are read out from the buffer amplifier 4 during the horizontal readout period, as in the normal readout method.

In the above embodiment, the signal of the photodiode of the same color corresponding to each row is described as being sequentially field-shifted and vertically transferred, but it may be provided that a plurality of rows and a plurality of colors are simultaneously transferred vertically.

As described above, by changing the accumulation time of each color in accordance with the color temperature, as shown in FIG. 5, an output in which the apparent color balance is maintained and the dynamic range is expanded can be obtained.

The color temperature at the time of photographing can be measured by performing normal photographing using the color solid-state image pickup device for an electronic still camera according to the present invention, and then back-outputting the output, or by using an external circuit.

(Effects of the Invention) As described above, according to the solid-state imaging device for color suitable for the electronic still camera of the present invention, the charge accumulation time of each color is provided to be different depending on the color temperature.
A white-balanced output signal is obtained, and the external signal processing circuit is simplified. Further, since the accumulation time can be set for each color and the light amount up to the saturation level of each color can be selected, the dynamic range can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color solid-state imaging device according to an embodiment of the present invention, FIG. 2 is an enlarged view of a main part of FIG.
4 (A) and 4 (A) are set corresponding to the color temperature characteristics, and FIGS. 3 (B) and 4 (B) are set corresponding to FIGS. 3 (A) and 4 (A). FIG. 5 is a light intensity-signal characteristic diagram obtained by the device of the present invention, and FIG. 6 is a light intensity-signal characteristic diagram of the conventional device. 2 ... accumulation gate, 3 ... horizontal transfer path, 4 ... buffer amplifier, 5 ... drain drain, 6 ... vertical transfer control section, 6a ... switch section, 6b ... CCD shift register, 7 ... gate Pulse control unit, 10: photosensitive unit, 11: photodiode, 12: vertical transfer path.

Claims (1)

(57) [Claims] 1. A horizontal line signal of photoelectric conversion elements arranged in a matrix is sequentially selected in a vertical direction by first and second drive signals generated from a vertical transfer control unit and started at a time difference of a predetermined interval from each other. In the color solid-state imaging device provided so that the first drive signal is drained to the discharge drain and the second drive signal is read out to the horizontal transfer path, the micro color signal arranged on the photoelectric conversion element is transferred. Pixels corresponding to two colors arranged on one horizontal line of the filter are connected to first and second polysilicon electrodes performing four-phase driving for each color, and the polysilicon electrodes are controlled by a gate pulse control unit. The vertical transfer control unit includes a vertical CCD shift register and a switch unit including a plurality of MOSFETs, and a hue difference between the first and second drive signals is determined according to a color temperature. Color for a solid-state imaging device, wherein the charge accumulation time is output to the gate MOSFET numbers are provided to be different for each color.