JPS58170168A - Driving system of image sensor - Google Patents

Abstract

PURPOSE:To always give a proper amount of light to an image sensor, by varying the scanning period in response to the light volume given to the image sensor. CONSTITUTION:The gain of an amplifier 2 is previously controlled so that the saturation voltage of an image sensor is set at a constant level after the amplifier 2. The output of a peak holding circuit 4 is supplied to the terminal of one side of a comparator 5 and compared with the reference voltage. Then the scanning period is successively extended from 20ms. When the peak holding voltage level of the first scanning does not reach the reference voltage, a signal of this difference is delivered from the comparator 5 and supplied to a scanning period control circuit 7 via an A/D converter 6. The circuit 7 extens successively the scanning period until no difference output is delivered any more from the comparator 5. In such a way, several times of scanning are satisfactory for obtaining the optimum scanning period, i.e., the optimum exposure time for the image sensor.

Description

Detailed Description of the Invention (1) Technical Field of the Invention Image sensor drive method that converts unexploded hFi optical information into electrical signals It is used for converting into signals, and OCR (optical character reader) is used to automatically read characters such as bank passbook characters, stamps, etc. Such an image sensor generally has a large number of pixels arranged with optical quality changing ability, and the output signal of the image sensor is -j depending on the amount of light given to these many pixels.
! It is read out at the Takitsubo period.

The amount of light for the image sensor is 111
As shown in the figure, it is determined by the product of light intensity and exposure time. When the amount of light given to the image center tK (light intensity x m light time) becomes too much, the center t reaches a saturated state and becomes proportional to the amount of light and no output signal can be obtained.

On the other hand, if the amount of light is too small, noise from the senna and the enclosure will cloud the 8/N ratio. Therefore, if the intensity of the light IIO light changes, or if the saturation exposure of the image sensor becomes too low, adjust the light intensity of the light source so that the amount of light to the image sensor becomes an appropriate value. Must do! There is.

(Tsuru) To change the strength of the light IIO light between the conventional technology and the light source, the strength of the current to the light source, t
If this is the case, you must either change the optical IIO position or adjust the lens O aperture. However, the light source is a warning light
In this case, it is difficult to change the current, and changing the position of the light source has a large mechanism, so the image quality is poor, and changing the aperture of the lens takes advantage of my resolution. This is not desirable.

(4) Purpose of the Invention The purpose of the present invention is to provide a driving method for an image sensor in order to solve the above-mentioned conventional problems.

(5) Structure of the invention The object of the present invention is to provide a plurality of ijs having a photoelectric conversion function.
In an image sensor in which storage is arranged and the WIJ elements are sequentially read out at a constant scanning period, the scanning period is changed according to the amount of light given to the image sensor. It will be achieved.

(6) Example #4 The present invention will now be described with reference to the drawings. FIG. 3 shows an image sensor driving circuit 1 according to an embodiment of the present invention.
The third plot shows a graph showing the relationship between beaterhold output voltage and the number of scan intervals.

By the way, the view given to the image senna is as mentioned above.
Even if the exposure time is changed by 0, which is (light intensity x exposure time), it is difficult to adjust the light amount. The point of this invention is K.
It is a JI model, and it is good because it has a rotation step that changes the exposure time of the image sensor and the scanning period of the camera according to the amount of light. If you want to see a stationary object with a two-dimensional image sensor, if you can scan more than 80mm K1, it will be Arashi.
For example, if the scanning period is in the range of gowm~@0m5O, 3
This means that a 0III node with twice the amount of light will be created.

Next, a method of driving the image sensor O will be explained with reference to the embodiment shown in FIG.

The output from the image sensor 1 is amplified by the amplifier 2, and the output of the amplifier 2 is converted to a digital signal by the A/DW converter 8 and converted into data! 6! It is sent to Section II, where reading, image, and character discrimination I6 are performed. On the other hand, the output from the amplifier 2 is input to a peak hold circuit 4. Note that the amplifier gain is adjusted in advance so that the saturation voltage of the image sensor becomes a constant value after amplifier 2.
Input to the terminal,! The quasi-voltage (for example, when the image is saturated, the voltage o'ro-> is compared with the voltage o'ro-> II!, and the scanning period is 10
Increase the length sequentially from mm.
When the O beater hold voltage value during scanning of Ill does not reach the reference voltage, a signal representing the difference is outputted from the comparator 5 and inputted to the scan period control circuit 7 via the M/D converter 6.

Scanning period control circuit 7 The scanning period is gradually lengthened until there is no differential output from the humperator device, and if several scans are performed as shown in <oF-, the optimum O scanning period is reached. Even in the case of C-dimensional scanning where uniform exposure times can be obtained, this method can be applied by changing the medium feeding speed etc. in accordance with the scanning period.11:b.

(7) Effects of WA As can be explained above, according to the image sensor driving method according to the present invention, there is no need to adjust the light intensity), there is no change in resolution, and the image sensor is always driven using the optimal light IK. It has the advantage of being able to

[Brief explanation of the drawing]

[Figure 1 is a graph showing the relationship between the light amount and output voltage of the image sensor, Figure 2 is a graph showing the image sensor drive circuit according to the embodiment of the present invention, and Figure 3 is the graph showing the relationship between the output of the peak hold circuit and the number of scanning pixels. In the diagram, 1 is the image sensor, 2 is the amplifier, 3.6
A uA/D converter, 4 a vinyl hold circuit, 7 a scanning cycle control circuit, and an 8-digit data processing section. Figure 3 Abandoned ridge

Claims (1)

[Claims] The pixels of the decimal number are arranged and have the function of converting into 9xi!
An image sensor driving method characterized in that the image sensor sequentially reads out an il tree at a constant scanning period, and the scanning period is changed according to the amount of f given to a wrinkle image sensor.