JPH0771234B2 - Solid-state image sensor and driving method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid-state imaging device such as a CCD (charge-coupled device) and a driving method thereof, and particularly to improve the dynamic range and aperture ratio of the solid-state imaging device. The sensitivity is variable.

(Prior Art) Conventionally, a solid-state image sensor such as a CCD has been used as a photoelectric conversion element in various television cameras, electronic still cameras, and the like. The signal charges obtained in this manner are sequentially transferred and read by two-phase to four-phase clock pulses and read out to output a video signal corresponding to the imaging light.

For example, as shown in FIG. 6, the interline CCD is composed of an imager section 3 including a photoelectric conversion section 1 and vertical transfer sections 2 alternately arranged, and a horizontal transfer section 4,
The signal charges obtained by the photoelectric conversion unit 1 are swept out through the vertical transfer unit 2 and the horizontal transfer unit 4 by the clock pulse CP supplied from the drive circuit 5.

(Problems to be Solved by the Invention) By the way, in the interline CCD as described above,
The dynamic range of the CCD is limited by the transfer charge amount of the vertical transfer unit 2.

Further, the dynamic range can be increased by increasing the transfer charge amount of the vertical transfer unit 2, but in that case, the area occupied by the vertical transfer unit 2 in the imager unit 3 becomes large and the aperture ratio decreases. Therefore, the sensitivity becomes poor.

(Means for Solving Problems) The present invention has been made in view of the above-mentioned actual circumstances,
It is an object of the present invention to provide a solid-state image pickup device capable of satisfying the contradictory conditions of widening the dynamic range and widening the aperture ratio and varying the sensitivity, and a driving method thereof.

In order to achieve this object, the present invention, as shown in FIG. 1, includes a photoelectric conversion unit 10 that photoelectrically converts image pickup light corresponding to each pixel, and a vertical transfer unit that transfers charges from these photoelectric conversion units 10. An imager unit 12 having an image pickup unit 11, an integrator 13 for temporarily accumulating electric charges from each photoelectric conversion unit 10 transferred from the imager unit 12, and an electric charge swept out from the integrator 13 for outputting as a video signal. The vertical register 15 and the horizontal transfer unit 14 are provided, the area occupied by the vertical transfer unit 11 in the imager unit 12 is formed sufficiently smaller than the area occupied by the photoelectric conversion unit 10, and the accumulation of each integrator 13 is performed. The capacitance is made larger than the charge amount obtained in each photoelectric conversion unit 10 by one exposure, and the charge obtained in each photoelectric conversion unit 10 is divided into a plurality of times to be swept to the vertical transfer unit 11 and the horizontal transfer Sweep from transfer unit 14 A solid-state image pickup device characterized in that the vertical transfer unit 11 transfers the image pickup light to each integrator 13 at high speed in time, and a photoelectric conversion unit 10 that photoelectrically converts image pickup light corresponding to each pixel, An imager unit 12 having a vertical transfer unit 11 for transferring the charges from the photoelectric conversion units 10, an integrator 13 for temporarily accumulating the charges from the photoelectric conversion units 10 transferred from the imager unit 12, and an integration unit 13 A vertical register 15 and a horizontal transfer unit 14 for outputting the electric charge swept from the device 13 as a video signal are provided, and the area occupied by the vertical transfer unit 11 in the imager unit 12 is compared with the area occupied by the photoelectric conversion unit 10. And the storage capacity of each of the integrators 13 is made larger than the charge amount obtained in each photoelectric conversion unit 10 by one exposure, and the charge obtained in each photoelectric conversion unit 10 is made plural. Vertical transfer divided into times A method of driving a solid-state image sensor, which is configured to perform high-speed transfer from the vertical transfer unit 11 to each integrator 13 in time for the sweeping out from the horizontal transfer unit 14 while sweeping out to the unit 11. A method for driving a solid-state image pickup device, which is characterized in that sensitivity can be varied by arbitrarily thinning out electric charges swept from 10 in multiple times.

(Operation) In the solid-state imaging device having the above-described configuration, the area occupied by the vertical transfer unit 11 in the imager unit 12 can be reduced to increase the aperture ratio of this type of solid-state imaging device and improve the sensitivity. it can.

Further, by providing an integrator 13 and transferring the charges obtained by the photoelectric conversion unit 10 from the vertical transfer unit 11 to this integrator 13 at high speed, the transfer charge amount per unit time of the vertical transfer unit 11 can be calculated. Can be greatly increased.

As a result, the charges obtained by the photoelectric conversion unit 10 are swept into the vertical transfer unit 11 in a plurality of times, and the swept charges are transferred at a high speed, thereby significantly increasing the dynamic range of this type of solid-state imaging device. Can be expanded.

Further, the sensitivity of this kind of solid-state image pickup device can be varied by appropriately thinning out the electric charge swept from the photoelectric conversion unit 10 as shown in FIG. 2B or 2C.

(Example) Hereinafter, a first preferred example of the solid-state imaging device according to the present invention will be described.
This will be described in detail with reference to FIGS.

FIG. 1 is a diagram in which the present invention is applied to a frame interline type CCD, and this CCD has an imager unit 12 and an integrator unit 1.
6 and a vertical register 15 and a storage unit 17 and a horizontal transfer unit 14
And is configured.

The imager unit 12 is configured to include a plurality of photoelectric conversion units 10 arranged in the vertical direction corresponding to each pixel, and a vertical transfer unit 11 provided between the photoelectric conversion units 10, The charges obtained in each photoelectric conversion section 10 are swept and transferred to the vertical transfer section 11 in a plurality of times by a two-phase clock pulse φ _A as shown in FIG. 2 (A).

Further, the horizontal width dimension of the vertical transfer unit 11 is formed to be narrower than the width dimension of the photoelectric conversion unit 10, so that the area occupied by the vertical transfer unit 11 in the imager unit 12 is occupied by the photoelectric conversion unit 10. It is much smaller than the area.

Therefore, the aperture ratio of this CCD is much larger than that of the conventional one.

The integrator 16 is configured to include a plurality of integrators 13 corresponding to each of the photoelectric conversion units 10, and these integrators 13 once accumulate the electric charges transferred from each of the vertical transfer units 11. It is designed to be swept out at high speed by 4-phase clock pulse φ _B.

In addition, the transfer or sweep of the charge to each integrator 13
Transfer gate 1 controlled by clock pulse φ _T
It is controlled by 8.

Then, the charges swept from each integrator 13 of the integrator unit 16 are converted into a video signal via the vertical register 15 and the horizontal transfer unit 14 which are respectively driven by the four-phase clock pulses φ _C and φ _H. It is designed to be output from the output terminal 18.

In the CCD having the above-described structure, the charges obtained by photoelectrically converting the imaged light in each photoelectric conversion unit 10 are divided into a plurality of times by the predetermined sweeping method as shown in FIG. Swept out to the transfer unit 11.

Note that this sweeping method is not limited to the method of sweeping after mixing the upper and lower pixels, but it is also possible to sweep all pixels as described later, and interlace sweeping is also possible by changing the combination of the upper and lower pixels. is there.

Further, the vertical transfer unit 11 is about 1000 times (60 kHz) when the sweep speed from the horizontal transfer unit 14 is 1/60 seconds.
Transfer at high speed.

As a result, even if the area of the vertical transfer unit 11 is smaller than the area of the photoelectric conversion unit 10, the amount of charge swept to the vertical transfer unit 11 for each time is small, and the swept charge is discharged at high speed. All charges obtained in the photoelectric conversion unit 10 can be sufficiently transferred by transferring with the above-mentioned method, and the amount of charges transferred at one time is reduced, so that the vertical transfer unit 11 has two phases as described above. It can be driven by a clock pulse φ _A.

Then, while the charges are transferred from the vertical transfer unit 11, the transfer gate 18 is opened and
Each integrator 13 is placed in the hold mode, and the transferred charges are temporarily stored in each integrator 13.

This integrator section 16 takes this for 1/60 second (1 field period)
After the charge for one frame obtained by the photoelectric conversion unit 10 is completed, the charge accumulated through the transfer gate 18 is transferred for one field at a high transfer rate by the clock pulse φ _B. The data is swept out so as to be interlaced one by one and transferred to each vertical register 15 of the storage section 17.

Then, the transferred charges are transferred to the clock pulse φ _C ,
The signal is transferred from the vertical register 15 and the horizontal transfer unit 14 at φ _H and is output from the output terminal 19 for each one field.

As described above, in the CCD according to this embodiment, the area occupied by the vertical transfer unit 11 can be made sufficiently small, so that the aperture ratio of this CCD can be increased.

Further, by increasing the transfer speed from the vertical transfer unit 11 to each integrator 13, the transfer charge amount of the vertical transfer unit 11 can be increased, so that the dynamic range of the CCD can be expanded. .

On the other hand, while charges are transferred from the vertical transfer unit 11, the integrators 13 are placed in the hold mode and the transfer gate 18 is opened / closed at a predetermined timing.
By discarding the charges transferred while the transfer gate 18 is closed through the overflow drain (not shown), the charges obtained by one exposure can be thinned out, and the sensitivity of this CCD can be set arbitrarily. Can be changed to.

And regarding the thinning method, for example, FIG.
Among the charges swept from the photoelectric conversion unit 10 as shown in, the charges swept at even times are discarded, or the charges swept at odd times are discarded as shown in FIG. It should be thinned out evenly.

By the way, in the above-described embodiment, the charges of the photoelectric conversion units 10 are mixed and swept out, but as shown in FIG. 3, the charges may be swept out without being mixed.

Then, in this case, the integrator in the integrator section 16 is divided into one for accumulating charges for odd fields 13o and one for accumulating charges for even fields 13e.
The transfer gates 18o and 18e, which are driven and controlled by clock pulses φ _T1 to 3o and 13e, selectively transfer the charges from the photoelectric conversion units 10, and further, the integrators described above.
Corresponding to 13o and 13e, the vertical registers 15o and 15e and the horizontal transfer sections 14o and 14e are respectively set to 2 channels, and charge is transferred to transfer gates 20 and 21 which are driven and controlled by clock pulses φ _V and φ _T2, respectively. It is sufficient to control the transfer path of.

Next, another embodiment according to the present invention will be described.

The frame interline CCD according to this embodiment is the fourth CCD.
As shown in the figure, the imager unit 12, the integrator 16, the storage unit 17, and the horizontal transfer unit 14 similar to those of the previous embodiment are provided, and the horizontal register 23 is provided between the integrator 16 and the storage unit 17. Has been done.

Then, the charges swept from the horizontal transfer section 14 are transferred to the horizontal register 23 via the switch 24.

As a result, the CCD according to this embodiment circulates the electric charge obtained by one exposure a plurality of times at a predetermined cycle, and outputs the same electric charge from the output terminal 19 for each circulation.

Therefore, for example, one exposure time is one field period (1 /
Even if it is longer than 60 seconds, the cyclic period as described above is 1/60
By setting the time to seconds, it is possible to obtain a video signal for each field, and it is possible to prolong the exposure time when a subject with low illuminance is photographed, so that the sensitivity can be significantly improved.

Further, since the electric charge obtained by one exposure can be output a plurality of times regardless of the exposure time, it is possible to easily obtain a video signal for frame still reproduction or strobe reproduction, and particularly for a fast-moving subject. It is possible to obtain a clear reproduced image without blurring when performing frame still reproduction, etc., and more clear than field still reproduction.

Furthermore, according to the present invention, as described above, since the aperture ratio of the imager unit 12 can be increased to improve the sensitivity, sufficient charges can be obtained even when the exposure time is extremely short, As a result, the image quality of the frame still reproduction can be further improved by using the CCD according to this embodiment.

Further, since the CCD has a wide dynamic range, it is possible to prevent smearing and blooming even when a bright subject is photographed with a long exposure time, and to photograph clearly.

The transfer and sweeping of charges to and from the horizontal register 23 in this CCD are controlled by transfer gates 25 and 26 which are driven and controlled by clock pulses φ _T and φ _V.

Further, in this embodiment, the charges of the photoelectric conversion units 10 are mixed and swept out, but as shown in FIG. 5, the charges may be swept out without being mixed.

In this case, in the same way as the embodiment described in FIG. 3, the integrators 13o and 13e, the vertical registers 15o and 15e, the horizontal transfer units 14o and 14e, and the horizontal registers 23o and 23e each have two channels. And clock pulses φ _T1 , φ _T2 ,
The transfer gates 18o, 18e, 27, 28, 29, 30, 31 may be driven and controlled by φ _T3 , φ v _L1 , φ v _L2 , and φ _T4 to control the charge transfer path.

(Effect of the Invention) As is apparent from the above description, according to the first invention, the aperture ratio of the imager portion can be increased and the dynamic range can be expanded.

Further, since the amount of transferred charges per one time in the vertical transfer unit is small, this vertical transfer unit can be driven by a two-phase clock.

Furthermore, according to the second aspect, the sensitivity of the solid-state image pickup device can be changed by appropriately thinning out the charges swept from the photoelectric conversion unit.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an embodiment of a solid-state image sensor according to the present invention, FIG. 2 is a diagram schematically showing discharge of charges, and FIG. 3 is a diagram schematically showing another embodiment. FIG. 4 is a view schematically showing another embodiment, FIG. 5 is a view schematically showing still another embodiment, and FIG. 6 is a view showing a conventional example. 10 ... Photoelectric conversion part, 11 ... Vertical transfer part, 12 ... Imager part, 13 ... Integrator, 14 ... Horizontal transfer part, 15 ... Vertical register.

Claims (2)

[Claims] 1. An imager section having a photoelectric conversion section for photoelectrically converting imaging light corresponding to each pixel, and a vertical transfer section for transferring charges from the photoelectric conversion section to the imager section, and each of the imager sections transferred from the imager section. An integrator that temporarily accumulates charges from the photoelectric conversion unit, a vertical register for outputting charges swept from these integrators and a horizontal transfer unit, and an area occupied by the vertical transfer unit in the imager unit. Is formed to be sufficiently smaller than the occupied area of the photoelectric conversion unit, and the storage capacity of each integrator is set to be larger than the charge amount obtained in each photoelectric conversion unit by one exposure. The electric charges obtained in the vertical transfer section are swept to the vertical transfer section in plural times and transferred from the vertical transfer section to each integrator at high speed in time for the sweeping out from the horizontal transfer section. A solid-state image sensor characterized in that 2. An imager section having a photoelectric conversion section for photoelectrically converting imaging light corresponding to each pixel, and a vertical transfer section for transferring charges from the photoelectric conversion section to the imager section, and each of the imager sections transferred from the imager section. An integrator that temporarily accumulates charges from the photoelectric conversion unit, a vertical register for outputting charges swept from these integrators and a horizontal transfer unit, and an area occupied by the vertical transfer unit in the imager unit. Is formed to be sufficiently smaller than the occupied area of the photoelectric conversion unit, and the storage capacity of each integrator is set to be larger than the charge amount obtained in each photoelectric conversion unit by one exposure. The electric charge obtained in step 2 is swept to the vertical transfer section in plural times, and is transferred from the vertical transfer section to each integrator at high speed in time for the sweep from the horizontal transfer section. The driving method of the solid-state image sensor, characterized in that the sensitivity can be varied by arbitrarily thinning out the charges swept from the photoelectric conversion units in a plurality of times. method.