JPH0376464A - Close contact type image sensor - Google Patents

Abstract

PURPOSE:To eliminate the need for a correction circuit on the outside of a sensor by providing a correction means uniformizing nearly a photoelectric conversion characteristic and obtaining a desired output value and a correction coefficient storage means storing a correction coefficient in matching with each photoelectric conversion element and inputting the coefficient to the correction means. CONSTITUTION:A scanning circuit 2 uses a MOS transistor(TR) 14 to switch photo diodes 15 and inputs the diode to an operational amplifier 13 with sequential changeover. The amplification factor of the operational amplifier 13 is set to a predetermined value by using output data ma, mb, mc, md of a ROM 17 synchronously with a scanning circuit 2 with a synchronizing signal i to correct the dispersion of the photoelectric conversion characteristic of the photodiodes 15. Thus, the output of the operational amplifier 13 is not dependent on the dispersion of the photoelectric conversion characteristic of the photo diodes and amplified to a desired value.

Description

[Detailed Description of the Invention] [Industrial Application Field] D! that optically reads document information. ! The present invention relates to a wearable image sensor.

[Summary of the invention]

The present invention provides a contact image sensor having a plurality of charging conversion elements and a scanning circuit that sequentially switches and operates the photoelectric conversion elements, and corrects variations in the photoelectric conversion characteristics of the photoelectric conversion elements and amplifies them to a desired value. By mounting the correction means and the correction coefficient storage means for storing the correction coefficient of the correction means on the contact type image sensor substrate, it is possible to almost uniformly correct variations in the photoelectric conversion characteristics and to amplify the photoelectric conversion characteristics to a desired value. sensor output can be obtained.

This suppresses adverse effects such as non-uniform brightness of the read document and non-uniform color reproduction caused by variations in photoelectric conversion characteristics, facilitates post-processing of sensor output, and provides an output that is resistant to noise.

[Conventional technology]

In conventional technology, variations in the photoelectric conversion characteristics of the photoelectric conversion elements are not corrected on the sensor board, but a circuit like the one shown in Figure 2 is provided outside the sensor, and standard data is used to approximately correct the photoelectric conversion characteristics. Corrected uniformly.

FIG. 2 will be explained.

Weak sensor output j output from the image sensor 11
is amplified by the amplifier 5, and the amplified sensor output k is expressed as S/H (
sample/hold) sampled by circuit 6, A/D
It is input to the conversion circuit 7. The A/D conversion circuit 7 is a known one that converts an analog signal into a digital signal. Further, the amplifier 5 may be of a known type consisting of a transistor, an operational amplifier, etc., and the S/H circuit 6 may also be of a known type.

When the output signal of the A/D conversion circuit 7 reads the reference data e, it is converted into a reciprocal number by the correction coefficient table 8 and inputted to the line memory 9 as correction data.

Next, when the original is read, the signal is converted into a digital signal by the A/D conversion circuit 7 and then input to the digital multiplier 10 . At this time, the image data f is multiplied by the correction data g stored in the line memory 9 to obtain an output signal with variations corrected.

[Problem to be solved by the invention]

In the method of correcting variations in photoelectric conversion characteristics as described above, the contact image sensor outputs the output of the photoelectric conversion element without correction or amplification, resulting in a weak and uneven sensor output. Moreover, for this reason, a complicated circuit as shown in FIG. 2 is required externally.

In addition, as shown in FIG. 2, the sensor output j is weak and is input to the amplifier 1Fg unit 5 as a signal containing variations, but the image sensor 11 uses digital No. 18 as the $IIm signal l. Therefore, a noise source such as radiation noise is present in the vicinity of the sensor output j. Therefore, it is difficult to ensure the S/N ratio of the weak sensor output j.

[! Means for Solving I8] In order to solve the above-mentioned LIB, in the present invention, the photoelectric conversion characteristics of the charging conversion element on the conventional contact type image sensor are almost uniform and a desired output value is obtained. and a correction coefficient storage means for storing correction coefficients suitable for each photoelectric conversion element and inputting them to the correction means.

[Effect]

According to the above configuration, variations in the photoelectric conversion characteristics of the photoelectric conversion elements can be corrected and amplified to a desired output value within the contact type image sensor substrate.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a configuration block diagram showing an embodiment of a contact type image sensor according to an embodiment of the present invention. In FIG. 1, a photoelectric conversion element 1 is a known type including a phototransistor, a photodiode, etc., and converts image data from light into an electrical signal. The scanning circuit 2 is a known type consisting of a counter, a shift register, etc., and operates by sequentially switching the photoelectric conversion elements 1 in accordance with an external control signal, and guides the output of the photoelectric conversion element 1 to the correction means 3. By using the data in the correction coefficient storage means 4, it is possible to correct variations in the photoelectric conversion characteristics of each photoelectric conversion element 1 and obtain a more or less uniform output. The correction coefficient storage means 4 consists of storage elements such as ROM, RAM, and registers, and stores predetermined correction coefficients.

FIG. 3 is a configuration diagram of an embodiment of the present invention.

The operation shown in FIG. 3 will be explained. The scanning circuit 2 switches the photodiode 15 using the MO3 type transistor 14, and sequentially switches the photodiode 15 and inputs it to the operational amplifier 13. The operational amplifier 13 receives output data ma from the ROM 17, which is synchronized with the scanning circuit 2 by the synchronization signal i.

The amplification factor is set to a predetermined value by mb, me, and md, and variations in the photoelectric conversion characteristics of the photodiode 15 are corrected. Here, the correction means 3 is the operational amplifier 13
The correction coefficient storage means 4 corresponds to the ROM 17.

As a result, the output of the operational amplifier 13 does not depend on variations in the photoelectric conversion characteristics of the photodiodes, and is amplified to a desired value.

Furthermore, by replacing the ROM 17 with RAM in the embodiment shown in FIG. 3, it becomes possible to rewrite the correction coefficients.

However, in this case, the RAM requires a data bus to be used when writing data.

By taking the data bus outside the contact type image sensor, it becomes possible to write arbitrary correction data from the outside.

The present invention is a contact image sensor characterized in that a correction means and a correction storage means are mounted on the same chip as a photoelectric conversion element.

FIG. 4 is a layout diagram of the embodiment of FIG. 3. The photoelectric conversion element 1 is a photodiode 15, and the correction means 3 is an operational amplifier 13. Resistors 18 and 19. MO3 type transistor 16,
The correction coefficient storage means 4 respectively correspond to the ROM 17 and are arranged as shown in FIG.

C Effects of the Invention As described above, according to the present invention, variations in the photoelectric conversion characteristics of photoelectric conversion elements can be corrected within the contact type image sensor substrate, eliminating the need for a correction circuit outside the sensor and reducing the need for a circuit wheel. can be achieved. Furthermore, the output impedance of the contact type image sensor becomes the output impedance of the operational amplifier in the output stage, and becomes very small.

Therefore, it can be connected to an external circuit in a state where it is not easily affected by noise, leading to an improvement in S/N.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a contact type image sensor of the present invention, FIG. 2 is a block diagram showing an example of a conventional photoelectric conversion characteristic variation correction circuit, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a layout diagram of the embodiment of FIG. 3.・Photoelectric conversion element ・Correction means ・Amplifier ・A/D conversion ・Line memory Scanning circuit Correction coefficient storage means S/H circuit correction table Digital multiplier or higher

Claims (1)

[Scope of Claims] A contact image sensor having a plurality of photoelectric conversion elements and a scanning circuit that sequentially switches and operates the photoelectric conversion elements, comprising: correcting variations in photoelectric conversion characteristics of the photoelectric conversion elements;
A contact type image sensor, characterized in that a correction means for amplifying to a desired value and a correction coefficient storage means for storing a correction coefficient of the correction means are mounted on a contact type image sensor substrate.