JPH04223680A - Driving method for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent the generation of a smear component and a flicker owing to light which leaks into a vertical transfer part when the image pickup of a still picture is executed. CONSTITUTION:The signal electric charge of the first field is transferred from a vertical transfer part 2 to an electric charge storing part at high speed, a signal is read from an electric charge storing part 3 at normal speed, after that, the signal electric charge of the second field is transferred to the electric charge storing part 3 at the high speed and after that, the electric charge of the electric charge storing part is transferred in a condition that the transfer of the electric charge of the vertical transfer part is stopped by reading the signal in order at the normal speed. The transfer of the signal electric charge from the vertical transfer part to the electric charge storing part 3 is executed at the high speed both on the first and the second fields and a smear and flicker noise are prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a solid-state imaging device optimal for photographing still images.

0002

[Prior Art] In recent years, solid-state image sensors have been developed using frame interline transfer type CCDs (FITs) as shown in FIG.
-CCD) are often used. FIG. 3 is a schematic diagram showing an example of such a solid-state image sensor. In this figure, 1
a is a first field light receiving element constituting a light receiving section having a photoelectric conversion function, and 1b is a second field light receiving element. The light receiving elements 1a and 1b are arranged alternately as shown in the figure to constitute the light receiving section 1. The signal charges photoelectrically converted in the light receiving section 1 are given to the vertical transfer section 2. Vertical transfer section 2
transfers signal charges in the vertical direction in accordance with an input clock, and its output is given to the charge storage section 3. The charge storage section 3 accumulates the transferred signal charges and provides the signal charges to the line transfer section 4. The line transfer section 4 sequentially reads out the accumulated signal charges using horizontal drive pulses applied to the input terminal 5 and outputs them as serial signals. Input terminals 6 and 7 are input terminals for clock signals applied to the vertical transfer section 2 and charge storage section 3, respectively.

FIG. 4 is a block diagram showing the configuration of a conventional solid-state image sensor driving circuit. In this figure, a shutter pulse 8 generates a pulse to open the shutter of the image sensor, and the shutter pulse is generated by a pulse control circuit 9.
given to. The pulse control circuit 9 is a control circuit that controls the timing of various pulse generators based on the shutter pulse, and its output is supplied to the first and second charge pulse generators 10 and 11, the sweep pulse generator 12, and the high-speed pulse generator. It is given to the transfer pulse generator 13 and the normal read pulse generator 14. The first and second field charge pulse generators 10 and 11 generate a first field charge pulse and a second field charge pulse for transferring the light reception data of the light receiving element of the first field and the second field to the vertical transfer section 2, respectively. It generates pulses. Further, the sweep pulse generating section 12 and the high-speed transfer pulse generating section 13 generate clock signals for faster reading than normal reading, and their outputs are given to the adder 15. Further, the adder 15 is supplied with a clock signal at a normal read speed from the normal read pulse generator 14. The adder 15 adds these signals and provides them to the input terminals 6 and 7 as a vertical transfer pulse and a charge accumulation pulse.

Next, a driving method for capturing a still image using a conventional solid-state image sensor will be described. Figure 5 (a
) is a shutter pulse for starting exposure of the light receiving section 1, and light is given to the light receiving section 1 at H level. At time t1 when the shutter pulse becomes H level, a charge pulse for the first field and a charge pulse for the second field are simultaneously applied as shown in FIGS. 5(b) and (c), and the exposure of the first and second fields is performed. All unnecessary charges before the start are transferred to the vertical transfer section 2, and the light receiving elements 1a,
Exposure of 1b is started at the same time. Then, the signal is moved by the vertical transfer pulse shown in FIG. 5(d) and the charge accumulation pulse shown in FIG. 5(e). As shown in FIG. 5(d), charges are applied from the vertical transfer unit 2 to the charge transfer unit 3 at high speed by the vertical pulse applied to the input terminal 6, and at the same time, the charge accumulation pulse is also a high-speed sweep pulse. Unnecessary charges such as dark components accumulated before the start of exposure and smear components during exposure can be swept out to the line transfer section 4. Then, at time t2 when the shutter pulse becomes L level, as shown in FIG. 5(b), the signal charge of the first field light receiving section 1a accumulated during the exposure time by the first field charge pulse is vertically transferred. 2, and the exposure of the first field is completed. Then, as shown in FIG. 5(d), the charge is transferred to the charge storage section 3 in a short time and at high speed by the high-speed transfer pulse (a). At time t3 after all the signal charges of the first field have been transferred to the charge storage section 3 at high speed, the charges of the second field light receiving section 1b are increased by the charge pulse of the second field, as shown in FIG. 5(c). The image is transferred to the vertical transfer section 2, and the exposure of the second field light receiving element 1b is completed. Then, by the normal read pulse (c) synchronized with the synchronization signal,
The signal charges of the field are read out from the signal storage section 3 to the line transfer section 4, and the signal charges of the second field are sequentially transferred from the vertical transfer section 2 to the charge storage section 3. The signal charges read out from the line transfer section 4 are sequentially output by horizontal drive pulses. After time t4 when all the signal charges of the first field have been transferred to the line transfer section 4 in this way, all of the signal charges of the second field are also transferred to the signal storage section 3. Then, two fields of signal charges can be sequentially read out from the charge storage section 3 to the line transfer section 4 by a normal read pulse (c) synchronized with the horizontal synchronizing signal, and further output by a horizontal drive pulse.

[0005]

[Problems to be Solved by the Invention] However, in such a conventional solid-state image sensor, the transfer of signal charges in the vertical transfer section 2 and the charge storage section 3 is the same as shown in FIGS. 5(d) and (e). It is done at a traffic light. Since the signal charges of the first field of the vertical transfer section 2 are transferred to the charge storage section 3 at high speed and in a short time by the high-speed transfer pulse (a), there is very little vertical smear. However, due to the normal read pulse (c) synchronized with the vertical synchronization signal that transfers the signal charge of the first field in the charge storage section 3 to the line transfer section 4, the signal charge of the second field is also transferred from the vertical transfer section 2 to the charge storage section. Transferred to 3. Therefore, since the signal charge of the second field cannot be transferred from the vertical transfer section 2 to the charge storage section 3 at high speed, the vertical smear component due to the light leaking into the vertical transfer section 2 is transferred from the vertical transfer section 2 to the charge storage section 3. This occurs in the signal charge of the second field inside. Therefore, there is a difference in the amount of smear between the first field and the second field, resulting in flicker, which has the disadvantage that it is not possible to take a still image of a good frame.

The present invention has been made in view of these conventional problems, and by transferring the first and second fields from the vertical transfer section to the charge storage section at high speed, a clear charge storage section can be obtained. A technical problem is to provide a method for driving a solid-state image sensor that can obtain a still image of a frame.

[0007]

[Means for Solving the Problems] The invention of claim 1 of the present application is directed to a plurality of fields of light receiving sections comprising a plurality of light receiving elements having a photoelectric conversion function, and to vertically transferring signal charges given from the light receiving sections. A method for driving a solid-state image sensor having a vertical transfer section that stores signal charges transferred from the vertical transfer section, and a charge storage section that stores signal charges transferred from the vertical transfer section, the method comprising: It is characterized by transferring the electric charges of the parts. Further, the invention of claim 2 of the present application transfers the signal charges of the first field of a certain frame from the light receiving section to the vertical transfer section, transfers the signal charges of the first field to the charge storage section at high speed, and then transfers the signal charges of the first field to the vertical transfer section. transfer is stopped, the signal charge of the second field constituting the same frame is transferred from the light receiving section to the vertical transfer section, and while the signal charge of the second field is held in the vertical transfer section, the signal charge of the first field of the charge storage section is transferred. After reading out the signal charges of the field and reading out all the signal charges of the first field from the charge storage section, the signal charges of the second field held in the vertical transfer section are transferred at high speed to the charge storage section, and the signal charges of the second field are transferred to the charge storage section, and the signal charges of the first field are read out from the charge storage section. The second field signal charge transferred to the second field is sequentially read out.

[0008]

[Operation] According to the present invention having such characteristics, the charge transfer unit is driven while the drive of the vertical transfer unit is stopped, and the signal charges of the first field are transferred from the vertical transfer unit when a still image of a frame is captured. The charges of the first field are transferred to the charge transfer section at high speed, the transfer of the charge transfer section is stopped, and the signal charges of the second field are held in the vertical transfer section, while the charges of the first field are read out to the line transfer section. After all the signal charges of the first field are read out, the signal charges of the second field held in the vertical transfer section are transferred to the charge storage section at high speed.

[0009]

Embodiment Next, a method for driving a solid-state image sensor according to an embodiment of the present invention will be described. The solid-state image sensor itself shown in FIG. 3 is the same as the conventional example described above, and the same parts are given the same reference numerals and the explanation thereof will be omitted. FIG. 2 is a block diagram showing the configuration of a driving circuit for a solid-state image sensor according to this embodiment. In this figure, the output of the charge pulse generator 8 is given to a pulse control circuit 21. The pulse control circuit 21 provides a timing signal to each block based on the shutter pulse as in the conventional example described above. The first and second charge pulse generators 10 and 11 are similar to the conventional example described above, and the outputs of the sweep pulse generator 12 and the high-speed transfer pulse generator 13 are given to an adder 22.
It is applied to the input terminal 6 as a transfer pulse of the vertical transfer section 2. Further, the outputs of the sweep pulse generation section 12 and the normal read pulse generation section 14 are applied to the input terminal 7 via the adder 23 as a transfer pulse for the charge storage section 3. The other configurations are the same as those of the conventional example described above.

Next, the operation of this embodiment will be explained. In this embodiment, it is assumed that the solid-state image sensor is driven according to a time chart as shown in FIG. In other words, in FIG. 1, unnecessary charges are transferred to the line transfer unit 4 at high speed for the vertical transfer pulse d.
It consists of a sweep pulse (A) that transfers the signal charge to the vertical transfer section, and a high-speed transfer pulse (B) that transfers the signal charge in the vertical transfer section at high speed.The charge accumulation transfer pulse is the sweep pulse (A)
, a high-speed transfer pulse (a), and a normal read pulse (c) driven at a normal read speed. The signal actually input to the solid-state image sensor is a three-value signal that is a combination of field charge pulses (b) and (c) and vertical transfer pulse (d). Also, the signal charge transfer method of the vertical transfer section 2 and the charge storage section 3 is single phase, two phase, three phase,
It says 4-phase, but usually 3-phase or 4-phase is used.
A signal input corresponding to the number of phases is required.

First, at time t11 when the shutter pulse (a) becomes H level, the first and second field charge pulses are inputted as shown in FIGS. All unnecessary charges before the start are transferred to the vertical transfer section 2. Then, exposure of the subject to be photographed simultaneously to the first and second field light receiving elements 1a and 1b is started. Then, unnecessary components such as dark components accumulated before the start of exposure and smear components during exposure in the vertical transfer section 2 and charge storage section 3 are swept out from the line transfer section 4 by a high-speed sweep pulse (A). Then, when the shutter pulse becomes L level at time t12, the signal charge of the first field light receiving element 1a accumulated during the exposure time is transferred to the vertical transfer section by the first field charge pulse, as shown in FIG. 1(b). Transfer to 2. And the first field light receiving element 1
Finish the exposure of a and transfer the signal charge with a high-speed transfer pulse (a)
is transferred to the charge storage section 3 at high speed. After all the signal charges are transferred to the charge storage section 3, the vertical transfer pulse (d) is stopped as shown in FIG. 1(d). and Figure 5(c)
As shown in FIG. 3, at time t13, the signal charge of the object accumulated during the exposure period in the second field light receiving section 1b is transferred to the vertical transfer section 2 and held there by the second field charge pulse. Then, only the signal charges of the first field stored in the charge storage section 3 are sequentially read out to the line transfer section 4 by a normal read pulse (c) synchronized with the horizontal synchronization signal. The signal charges read out to the line transfer section 4 are sequentially outputted by horizontal drive pulses. After time t14 when all charges of the first field stored in the charge storage section 3 are read out to the line transfer section 4, the vertical transfer pulse is input again as a high-speed transfer pulse (a) as shown in FIG. 1(d). Then, the signal charges of the second field held in the vertical transfer section 2 are transferred at high speed. After all the signal charges of the second field are transferred to the charge storage unit 3, the signal charges of the second field in the charge storage unit 3 are sequentially read to the line transfer unit 4 by the normal read pulse (c) synchronized with the horizontal synchronization signal. put out. The signal charges read out to the line transfer section 4 are sequentially outputted by horizontal drive pulses.

As described above, in this embodiment, the signal charge of the first field is transferred from the vertical transfer section 2 to the charge storage section at high speed using a high-speed transfer pulse, and the transfer pulse of the vertical transfer section 2 is stopped to transfer the signal charge of the second field. While the signal charges are held in the vertical transfer section 2, the signal charges of the first field of the charge storage section 3 are read out to the line transfer section 4 using a normal read pulse. After reading out all the signal charges of the first field, a high-speed transfer pulse is input as a vertical transfer pulse to transfer the signal charges of the second field to the charge storage section 3 at high speed. Therefore, the signal charges are transferred from the vertical transfer section 2 to the charge storage section 3 first.
, and the second field can be performed at high speed, and in both fields it is possible to obtain a clear frame still image with little vertical smear and no flicker.

[0013]

As described in detail above, according to the inventions of claims 1 and 2 of the present application, since the drive of the vertical transfer section is stopped and the charge storage section is driven, the first and second All the signal charges in the field can be transferred to the charge storage section at high speed. Therefore, it is possible to obtain a clear frame still image with very little vertical flare in both the first and second fields and no flicker.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing the operation when driving a solid-state image sensor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a driving device for a solid-state image sensor according to the present embodiment.

FIG. 3 is a schematic diagram showing the configuration of a solid-state image sensor.

FIG. 4 is a block diagram showing a drive circuit for a conventional solid-state image sensor.

FIG. 5 is a time chart showing a conventional method for driving a solid-state image sensor.

[Explanation of symbols]

1a First field light receiving element 1b Second field light receiving element 1 Light receiving part 2 Vertical transfer section 3 Charge storage section 4 Line transfer section 6, 7, 8 Input terminal

Claims (2)

[Claims] 1. A plurality of fields of light-receiving sections configured of a plurality of light-receiving elements having a photoelectric conversion function; a vertical transfer section that vertically transfers signal charges provided by the light-receiving section; and a vertical transfer section that transfers signal charges from the vertical transfer section. a charge accumulation section for accumulating signal charges, the method further comprising transferring charges in the charge accumulation section while stopping transfer of charges in the vertical transfer section. Features: Driving method of solid-state image sensor. 2. After transferring the signal charge of the first field of a certain frame from the light receiving section to the vertical transfer section and transferring the signal charge of the first field to the charge storage section at high speed,
The transfer of the vertical transfer section is stopped, the signal charges of the second field constituting the same frame are transferred from the light receiving section to the vertical transfer section, and the signal charges of the second field are held in the vertical transfer section. The signal charges of the first field are read out from the charge storage section, and after all the signal charges of the first field are read out from the charge storage section, the signal charges of the second field held in the vertical transfer section are transferred to the charge storage section at high speed. 2. The method of driving a solid-state image sensor according to claim 1, further comprising transferring the signal charges to a storage section and sequentially reading out the signal charges of the second field transferred to the charge storage section.