JPH03214962A - Drive method for solid-state image pickup device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a method for driving a solid-state imaging device that converts optical image information into an electrical signal, and particularly relates to a method for driving a solid-state imaging device that converts optical image information into an electrical signal. The present invention relates to a method for driving a 3-line color image sensor suitable for applications such as the following.

(Prior Art) A conventional method for driving a solid-state imaging device will be described with reference to FIG. 2, which shows the configuration of the device.

Solid-state imaging devices (hereinafter referred to as CCDs) are arranged in three rows (CCDI~3) in the vertical direction (sub-scanning direction), and each photosensitive element row 1-3 is covered with a color filter of a primary color or complementary color. . Taking CCDI as an example, shift gates 4 that control the time during which charges are integrated in the photosensitive element array 1 are adjacent to both sides of the photosensitive element array 1. Analog shift registers 7 and 8 are adjacent to each other and sequentially transfer the received signal charges. The analog shift register 7 transfers signal charges of odd-numbered pixels of the photosensitive element column 1, and the analog shift register 8 transfers signal charges of even-numbered pixels of the photosensitive element column 1. The transferred signal charges are converted into voltage signals by output circuits 13 and 14 arranged at the left ends of analog shift registers 7 and 8, and output to the outside of the device.

When using a solid-state imaging device with such a configuration to perform stepless enlargement and reduction reading by changing the scanning speed of the optical system, it is necessary to set the integration time of each CCDI to 3 to be the same. In this case, the reading positions on the document surface differ between each of the CCDs 1 to 3. As a result, image shift or color shift occurs in the sub-scanning direction. To prevent such a phenomenon, it is necessary to make the integration time of each CCDI~3 variable.

FIG. 3 shows conventional drive pulses that vary the integration time for each CCDI to 3. Main scanning synchronization signal Φ to synchronize in the horizontal direction (main scanning direction) for sampling
The pulse width of SH1 to SH3 is determined by each analog shift register 7.
It is sufficiently wide compared to the two-phase transfer clocks ΦIA1-3 and Φ2A1-3 (several MHz or more) that drive the clocks ΦIA1-12. Furthermore, during the period in which the main scanning synchronization signals ΦSHI-3 are being generated, the two-phase transfer clocks ΦIAI-3 need to be fixed at a high level, and the two-phase transfer clocks Φ2A1-3 need to be fixed at a low level. Therefore, during the generation period of the main scanning synchronization signals ΦSHI~3, the respective two-phase transfer clocks ΦIA1~3,
and Φ2A1-3 are all in a stopped state, and there are discontinuous portions in the two-phase transfer clocks ΦIA1-3 and Φ2A1-3. By using such drive pulses, it becomes possible to cope with enlargement and reduction.

(Problem to be solved by the invention) However, if the integration time is made variable, the periods in which discontinuous portions occur in the two-phase transfer clocks ΦIA1-3, 2A1-3 of each CCDI-3 will shift as shown in Figure 3. It's coming. As a result, for example, the CCDI two-phase transfer clock ΦIAI
, 2AI will cause crosstalk to the output signals OS2-3 of the other CCDs 2 and 3.

This evening losstalk is caused by discontinuous clock pulses arriving between adjacent CCDs. As a result, each output signal OS1 to
3 as a fixed amount of offset signal. As a result, the values of the black level signal partially differ, and when an image is outputted, such as by printing, in this state, image quality deterioration such as streaks and unevenness occurs.

Conventionally, in order to avoid such a situation, the value of the black level signal has been corrected. However, in order to do this, it is necessary to separate the area where crosstalk has occurred from other areas, generate a black level correction signal corresponding to each area, and correct each area separately at the stage of reading the image signal. Must be. As a result, the circuit configuration and arithmetic processing process become more complicated.
There is a problem in that the device becomes larger and the cost increases.

The present invention has been made in view of the above circumstances, and it is possible to prevent crosstalk from occurring between each CCD when the integration time is made variable, and to prevent deterioration of image quality without adding correction to the output signal. An object of the present invention is to provide a method for driving a solid-state imaging device.

[Structure of the invention]

(Means for Solving the Problems) The present invention has three photosensitive element rows arranged in the sub-scanning direction in which a plurality of photosensitive elements that generate signal charges according to the amount of incident light are arranged in the main scanning direction. The upper surface of each of the photosensitive elements is covered with a color filter, and a shift gate that controls the integration time of the signal charge generated by each of the photosensitive element rows is adjacent to each of the photosensitive elements, and an analog shift register that sequentially transfers the generated signal charge. is adjacent to each of the shift gates, and an output circuit that outputs the transferred signal charge to the outside as a voltage signal is adjacent to each of the analog shift registers.
When the integration time controlled by the shift gate differs for each photosensitive element row, all analog shift registers are synchronized to prevent the difference in the generation period of the signal synchronized in the main scanning direction from interfering with the voltage signal. It is characterized by being driven using pulses.

(Function) If the integration times of the signal charges in the three photosensitive element rows are different, the generation period of the signal synchronized in the main scanning direction will be shifted, but by driving all the analog shift registers with synchronized pulses, Interference with the voltage signals output from each output circuit does not occur, and deterioration of image quality is prevented even without correction of the black level signal.

(Example) Hereinafter, a method for driving a solid-state imaging device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a timing chart of driving pulses used in this embodiment. In this embodiment, unlike the conventional case shown in FIG. 3, synchronized two-phase transfer clocks ΦIA1-3 and Φ2A1-3 are used.

Here, the pulse width of main scanning synchronization signals ΦSH1 to ΦSH3 is 2
It is sufficiently wide compared to the phase transfer clocks ΦIA1-3, Φ2A1-3, and during the period when this main scanning synchronization signal ΦSHI-3 is generated, the two-phase transfer clocks ΦIA1-3 are at high level, and the two-phase transfer clocks Φ2A1-3 are at a high level. 3 is fixed at a low level to be in a stopped state, which is the same as in the conventional case.

A two-phase transfer clock ΦIA that satisfies these conditions
In order to synchronize all of the signals 1 to 3 and Φ2A1 to 3, all two-phase transfer clocks are stopped during a period when any one of the main scanning synchronization signals ΦSHI to 3 is generated. For example, when the main scanning synchronization signal ΦSHI is generated, the two-phase transfer clock ΦIA1 related to the same CCDI
, Φ2A1 as well as other two-phase transfer clocks ΦIA
2 to 3 and Φ2A2 to 3 are also stopped at the same time.

By driving using such pulses, all discontinuous portions occur at the same time, making it possible to prevent crosstalk from occurring. As a result, an offset signal as shown in FIG. 3 is not superimposed on the output signals OS1 to OS3. Therefore, the black level signals all have the same value, and image quality does not deteriorate even if the correction required in the past is not performed. Thereby, it is possible to prevent the circuit configuration and the calculation process from becoming complicated.

Also, since parts that are not originally needed are stopped, the period during which the signal is output will be longer, or the timing will be the same as other continuous parts.
No inconvenience will occur.

The embodiments described above are merely examples and do not limit the present invention. For example, the waveforms of the driving pulses shown in FIG. 1 do not necessarily all match;
It is sufficient that the transfer clocks that drive the analog shift registers are synchronized.

〔Effect of the invention〕

As explained above, the present invention can synchronize all analog shift registers even when the integration times of signal charges in three rows of photosensitive element rows are different and there is a shift in the generation period of the signal to be synchronized in the main scanning direction. Since it is driven by pulses, there is no interference with the output voltage signal, and it is possible to prevent deterioration of image quality without having to correct the black level signal, which complicates the circuit configuration and calculation processing, making the device more compact. , cost reduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a timing chart showing driving pulses used in a method for driving a solid-state imaging device according to an embodiment of the present invention;
FIG. 2 is a circuit configuration diagram showing the configuration of a solid-state imaging device to which this embodiment can be applied, and FIG. 3 is a timing chart showing driving pulses used in a conventional method for driving a solid-state imaging device. 1, 2.3...Photosensitive element row, 4...Shift gate (
Shift gate (for photosensitive element row 1), 5... Shift gate (for photosensitive element row 2), 6... Shift gate (for photosensitive element row 3), 7
... Analog shift register (for odd-numbered pixels in photosensitive element row 1), 8... Analog shift register (for even-numbered pixels in photosensitive element row 1), 9... Analog shift register (
(for odd-numbered pixels in photosensitive element row 2), 10... analog shift register (for even-numbered pixels in photosensitive element row 2), 11...
Analog shift register (for odd-numbered pixels in photosensitive element row 3)
, 12... Analog shift register (for even-numbered pixels in photosensitive element row 3), 13... Output circuit (for odd-numbered pixels in photosensitive element row 1), 14... Output circuit (for even-numbered pixels in photosensitive element row 1) ), 15... Output circuit (for odd-numbered pixels in photosensitive element row 2), 16... Output circuit (for even-numbered pixels in photosensitive element row 2), 17... Output circuit (for odd-numbered pixels in photosensitive element row 3) (for pixels), 18...output circuit (for even-numbered pixels in photosensitive element row 3)
.

Claims (1)

[Scope of Claims] Three rows of photosensitive elements are arranged in the main scanning direction in which a plurality of photosensitive elements that generate signal charges according to the amount of incident light are arranged in the sub-scanning direction, and the upper surface of each of the photosensitive element rows is arranged in three rows in the sub-scanning direction. A shift gate covered with a color filter and controlling an integration time of signal charges generated by each of the photosensitive element arrays is adjacent to each of the photosensitive elements, and an analog shift register that sequentially transfers the generated signal charges is arranged between the photosensitive element arrays. A method for driving a solid-state imaging device adjacent to each of the analog shift registers, wherein an output circuit that is adjacent to each of the shift gates and outputs the transferred signal charge to the outside as a voltage signal is controlled by the shift gate. When the integration time is different for each of the photosensitive element rows, in order to prevent a difference in the generation period of the signal for synchronizing in the main scanning direction from interfering with the voltage signal, all the analog shift registers are synchronized with pulses. 1. A method for driving a solid-state imaging device, characterized by driving the solid-state imaging device using the following method.