JPH0691660B2 - Solid-state image sensor for color - Google Patents

Description

The present invention relates to a CCD type solid-state image pickup device and a color solid-state image pickup device comprising a micro color filter arranged corresponding to pixels on the CCD type solid-state image pickup device. For example, the present invention relates to a solid-state imaging device which is excellent in blue sensitivity, has good color balance, and can improve overall sensitivity in a frame transfer type charge transfer system.

(Prior Art) In the frame transfer type solid-state imaging device, the photoelectric conversion element itself has a charge transfer function, and
Since a transparent electrode made of polysilicon for transferring charges is arranged, light is absorbed here and the sensitivity is lowered. In particular, when a frame transfer type solid-state image pickup device is applied for color, absorption of light on the short wavelength side is larger than that on the long wavelength side. In this case, since the sensitivity of the image pickup system should be close to the luminosity, in the conventional example, for example, a cyan filter is applied to the entire surface of the element to substantially reduce the light on the long wavelength side, thereby achieving the entire color balance. It was

(Problems to be Solved by the Invention) However, the method of reducing the light on the long wavelength side as described above in order to achieve color balance is not preferable because it leads to a reduction in the overall sensitivity. In order to achieve color balance, if the sensitivity on the short wavelength side can be relatively increased according to the long wavelength side, good color balance can be obtained without lowering the overall sensitivity.

Therefore, the object of the present invention is to improve the blue sensitivity and improve the overall color balance by relatively improving the short wavelength side sensitivity corresponding to the long wavelength side sensitivity of the light incident through the color filter. Another object of the present invention is to provide a color solid-state imaging device that can be used.

(Means for Solving Problems) In order to achieve the above object, the color solid-state imaging device according to the present invention is configured as follows. That is, a vertical charge transfer section, a photoelectric conversion section arranged in parallel on both left and right sides of the vertical charge transfer section via transfer gates, and a first horizontal charge transfer section arranged on the output side of the vertical charge transfer section are provided. In addition to the above, a switching circuit, a charge storage unit corresponding to the vertical charge transfer unit, and second and third horizontal charge transfer units attached to the charge storage unit are provided. In the storage unit, two columns of storage lines are assigned corresponding to one column of the vertical charge transfer unit, and the horizontal widths of the storage lines are one column of the vertical charge transfer unit and two columns of the photoelectric conversion unit. Is 1/2 of the horizontal width of the pair, and the vertical charge transfer unit can not only transfer the signal charge formed by the photoelectric conversion unit but also perform photoelectric conversion by itself, and 3 A signal charge of the first color of the primary colors is formed, and the photoelectric conversion unit is 3 The signal charges of the remaining second and third colors of the colors are formed, and the signal charges output from the vertical charge transfer unit are transferred to the storage line via the first horizontal charge transfer unit or the switching circuit. It is selectively distributed to one side and read from the second or third horizontal charge transfer section.

(Operation) In the solid-state color image pickup device according to the present invention, the photoelectric conversion unit is an interline transfer type photoelectric conversion device,
The vertical charge transfer section is composed of a frame transfer type photoelectric conversion element. Further, the micro color filter, for example, R, G, B stripe filter is used,
Colors G and B are arranged on the photoelectric conversion part where the polysilicon transfer electrode is not arranged, and a color R having good light transmittance is arranged on the vertical charge transfer part where the polysilicon transfer electrode is present without being absorbed by polysilicon. Has been done. Then, first, the signal charge of the color R formed in the vertical charge transfer section is distributed by the switching circuit and transferred to the color R channel of the charge storage section during the signal transfer cycle. During this period, colors G and B
Signal charges remain in the respective photoelectric conversion units. Color R
When all the signal charges of B are transferred to the charge storage unit, the signal charge of one of the colors B and G, for example, the signal charge of B is provided between the photoelectric conversion unit that formed this signal charge and the vertical charge transfer unit. The color R is field-shifted to the vertical charge transfer unit that previously transferred the color R via the transfer gate. That is,
The vertical charge transfer unit operates as an element that performs photoelectric conversion and transfer of the color R and transfer of the color B and the color G described later. When color B is field-shifted, the switching circuit then switches to transfer color B to the other channel of the charge storage,
That is, it is transferred to the channel for color B. When all the color B signal charges are transferred to the charge storage unit, finally, the color G signal charges are transferred via the transfer gate provided between the photoelectric conversion unit storing the signal charges and the vertical charge transfer unit. The field is shifted to the vertical charge transfer section. At this time, the signal charges of the colors R and B are already prepared in the respective channels of the charge storage section, and the signal charges of the color G are also prepared in the vertical charge transfer section. All of these signal charges are then simultaneously read out via a predetermined horizontal charge transfer section, that is, a horizontal CCD.

It is needless to say that at least the vertical charge transfer portion must be shielded by some light shielding means, for example, a mechanical shutter, during the charge transfer.

As described above, in the color solid-state image sensor according to the present invention,
A set of a vertical charge transfer unit of a book and two rows of photoelectric conversion units provided along the vertical direction so as to sandwich the transfer unit is set as one set, and a plurality of sets are arranged side by side in the horizontal direction to form an imaging unit. Filters for short and medium wavelengths, such as light absorption by polysilicon, are placed on the photoelectric conversion unit that operates as an interline transfer type, while filters for colors corresponding to long wavelength light are set on the frame transfer. The charge of each color is formed by arranging it on the vertical charge transfer portion that operates as a shape. Further, two colors among the formed charges are transferred to one charge storage section divided into two, the remaining one color is transferred to the vertical charge transfer section, and thereafter, simultaneous reading is performed from three horizontal CCDs.

Further, since the signal charges of the two photoelectric conversion units are sequentially read by using one vertical charge transfer unit, the threshold voltages of the respective transfer gates are set to different values.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an outline of a solid-state color image pickup device according to an embodiment of the present invention. The image pickup device includes an image pickup unit 1
, The first horizontal CCD 2, the switching circuit 3, and the charge storage unit 4
And the second and third horizontal CCDs 5 and 6 attached to the charge storage section as main constituent elements.

The image pickup unit 1 includes a plurality of horizontal charge transfer units 1a each having a photoelectric conversion function and two photoelectric conversion units 1b arranged on the left and right sides of the vertical charge transfer units 1a in the horizontal direction. They are arranged and formed. A micro color filter is arranged on the image pickup unit 1. The micro color filter includes photoelectric conversion units 1b and vertical charge transfer units.
It has three colors R, G, B corresponding to 1a. The micro color filter used in the present invention comprises a stripe array in which the same color is arranged in the vertical direction. Diagonal lines in the figure and R, G,
This sequence is shown schematically by B. A filter R is arranged on the vertical charge transfer portion 1a, and filters G and B are arranged on the photoelectric conversion portion 1b.

FIG. 2 is an enlarged view of the image pickup unit 1.

The vertical charge transfer portion 1a under the filter R is provided with a plurality of polysilicon transfer electrodes 7 extending in the horizontal direction, and the charges are sequentially transferred to the output side by four-phase driving (φV1 to φV4). To do. On the other hand, the photoelectric conversion units below the filters G and B
1b, that is, the surface of the photodiode is opened and the transfer electrode 7 is not provided. Instead, a transfer gate 8 is provided for each photodiode between each photoelectric conversion section 1b and the vertical charge transfer section 1a. The transfer gate 8a for controlling the discharge of the charge of the color B and the transfer gate 8b for controlling the discharge of the charge of the color G have different threshold voltages. In the present embodiment, the color B (Vth) <the color G (Vth). It is provided in.

In the figure, the portion indicated by the alternate long and short dash line is the channel stopper 13 formed on the silicon substrate, and the photoelectric conversion portion 1b and the vertical charge transfer portion are provided in the portion surrounded by the channel stopper.
1a, that is, a self-scanning type CCD shift register is formed.

Returning to FIG. 1, a first horizontal CCD 2 and a switching circuit 3 are formed on the output side of the image pickup unit 1 via the first transfer gate TG1, and the output side of the switching circuit 3 is further provided. Charge storage unit 4
Is provided.

FIG. 3 is a configuration diagram for further explaining the above-mentioned portion.

The first transfer gate TG1 is turned on and off by the control signal S _1, and summer to control the transfer of signal charges from the imaging section 1. The first horizontal CCD 2 is composed of a CCD shift register, and the transfer electrodes 21 and 22 arranged in parallel in the horizontal direction are arranged.
Thus, the signal charges transferred from the image pickup unit 1 are sequentially output to the attached buffer amplifier 9.

The switching circuit 3 is composed of second and third transfer gates TG2, TG3 and gates G2, G3. The gates G2 and G3 have a substantially comb shape, and are arranged in a staggered manner and provided in an antiphase relationship.

In the charge storage unit 4, when one set of columns consisting of R, G, and B in the image pickup unit 1 is defined as one pitch W, one channel is formed with a channel width W / 2 obtained by dividing the same pitch into two, and the storage line 4
A storage line 4b is provided. The charge storage section 4 is configured so that the switching circuit 3 distributes and supplies the charge to either one of the storage lines 4a and 4b. Then, the charges of the distributed storage lines 4a, 4b are transferred to the output end by the transfer electrode 10 provided similarly to the image pickup unit 1.

Next, the state of the transfer of the signal charges will be described. The first transfer gate TG1 is held in the open state during the transfer of the charges.
Therefore, when the gate G2 of the switching circuit 3 is set to the L level and the gate G3 of the switching circuit 3 is set to the H level, the charge of the color R is applied to the vertical charge transfer unit.
It is supplied from 1a to the storage line 4a. Next, the charge of the color B is supplied to the storage line 4b by switching the gate G2 of the switching circuit 3 to the H level and the gate G3 of the switching circuit 3 to the L level after the transfer gate 8a is opened and field-shifted to the vertical charge transfer section 1a. It Finally, the color G is field-shifted to the vertical charge transfer unit 1a by applying the threshold voltage Vth higher than that of the previous transfer gate 8a and opening the transfer gate 8b. At this time, the switching circuit 3 sets both the gates G2 and G3 at the L level to prevent the transfer of the charges to the accumulating portion, so that the preparation for transferring all the charges is completed only in the vertical charge transferring portion. Then the color R of the storage line 4a is changed to the second horizontal CC
From the R buffer amplifier 11 via D5, the color B of the storage line 4b from the B buffer amplifier 12 via the third horizontal CCD6, and the color G of the vertical charge transfer unit 1a via the first horizontal CCD2 to G color. It is read from the buffer amplifier 9 at the same time.

The signal charge is read from each of the horizontal CCDs 9, 11 and 12 in a conventional manner.

(Effects of the Invention) As described above, according to the solid-state color image pickup device of the present invention, the filters of the colors of the short wavelength side and the medium wavelength side are arranged on the photoelectric conversion section having no polysilicon electrode, and the long wavelength side is arranged. By arranging the color filter on the side above the vertical charge transfer section, the sensitivity on the short wavelength side and the medium wavelength side can be relatively increased without lowering the sensitivity of the light on the long wavelength side, and a good color balance can be obtained. It can be obtained and the overall sensitivity can be improved.
Further, by using the storage part divided into two parts, it can be manufactured without increasing the chip area.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is an enlarged block diagram showing the image pickup section thereof, and FIG. 3 is a diagram explaining the switching circuit and operation thereof. 1 ... Image pickup unit, 1a ... Vertical charge transfer unit, 1b ... Photoelectric conversion unit, 2 ... First horizontal CCD, 3 ... Switching circuit, 4 ... Charge storage unit, 5 ... Second horizontal CCD, 6 ... Third horizontal CCD, 7,10 ... Transfer electrode, 8 ... Transfer gate, 9,11,12 ... Buffer amplifier, 13 ... Channel stop

Claims (3)

[Claims] 1. A color solid-state image pickup device comprising a CCD type solid-state image pickup device and a micro color filter arranged thereon corresponding to pixels, in which a vertical charge transfer section and left and right sides of the vertical charge transfer section are transferred. A photoelectric conversion unit arranged side by side via a gate and a first horizontal charge transfer unit arranged on the output side of the vertical charge transfer unit are provided, and in addition, a switching circuit and the vertical charge transfer unit are provided. Corresponding charge storage units and second and third horizontal charge transfer units attached to the charge storage units are provided, and the charge storage units are arranged in two columns corresponding to one column of the vertical charge transfer units. Storage lines are allocated, and the horizontal width of the storage lines is 1/2 of the horizontal width of a set of one column of the vertical charge transfer units and two columns of the photoelectric conversion units. The charge transfer unit is a signal transfer unit formed by the photoelectric conversion unit. Of the three primary colors, and the photoelectric conversion unit forms the signal charge of the first color among the three primary colors. The signal charge that forms a color signal charge and is output from the vertical charge transfer unit is selectively distributed to one of the storage lines via the first horizontal charge transfer unit or the switching circuit, and the second Alternatively, the color solid-state image pickup device is read out from the third horizontal charge transfer unit. 2. The threshold voltages of the transfer gates, which control the photoelectric conversion units of the two columns provided on both sides of the vertical charge transfer unit, are set to different values. The device according to claim 1. 3. Filters for colors G and B of the same color are arranged vertically on the two rows of photoelectric conversion units, and filters for color R are arranged on the vertical charge transfer unit. The element according to claim 1.