JPS63180267A - Photoelectric converter - Google Patents

Abstract

PURPOSE:To improve S/N and the accuracy by executing pseudo read processing at a timing corresponding to the quantity of light without saturating an accumulative type image sensor. CONSTITUTION:Light radiated from a light source 1 reflects at the surface 2 of an original, and is converged by an optical system lens 3, and an image is formed on the accumulative type image sensor 4. A photoelectric conventing means 5 drives the sensor 4, and simultaneously quantize its output and outputs it to an external section. A light quantity detection means 6 detects at all time the light-quantity from the light source 1, and according to the result of this detection, a charge sweeping means 7 determines at which one of the plural times of reading timings preliminarily set within one time read scanning period is the pseudo read processing to be executed in order not to saturate the sensor, and outputs the timing signal of the pseudo read processing to the means 5. Accordingly, the exposure time of the sensor 4 is relatively shortened, hence it does not go to a saturated status. As a result, an output in sufficient dynamic range can be obtained, and the S/N and the accuracy can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoelectric conversion device for an optical system such as an image sensor or a facsimile.

[Conventional technology]

FIG. 2 is a block diagram showing the configuration of a conventional photoelectric conversion device. In the figure, 1 is a light source realized by, for example, a fluorescent lamp, 2 is the document surface which is the object to be read, 3 is an optical system lens,
Reference numeral 4 denotes an accumulation type image sensor which stores the amount of light reflected from the document surface 2 as a charge, and 5 denotes a photoelectric conversion means which drives the accumulation type image sensor 4, quantizes its output, and outputs it to the outside.

Next, the operation of this conventional device will be explained.

Light emitted from a light source 1 is reflected by a document surface 2, and this reflected light is collected by an optical system lens 3 and formed into an image on an accumulation type image sensor 4. As a result, storage type image sensor 4
outputs a voltage or current proportional to the accumulated exposure amount,
The level of the voltage or current is determined by the photoelectric conversion means 5 and outputted to the outside (later-stage circuit) as quantized data.

[Problem that the invention seeks to solve]

Since the conventional photoelectric conversion device is configured as described above, for example, when a fluorescent lamp is used as the light source 1 and the light intensity of the light source 1 changes greatly depending on the temperature etc., the output of the storage type image sensor 4 will depend on the input light intensity. Since the exposure time of the storage type image sensor 4 must be set according to the maximum light intensity, the storage type image sensor 4 must be set in proportion to the product of There were problems such as difficulty in obtaining an output with a sufficient dynamic range and poor S/N ratio.

This invention was made to solve the above-mentioned problems, and provides a highly accurate photoelectric conversion device that changes the exposure time of a storage image processor according to changes in the amount of light without reducing the syo ratio. The purpose is to

a light amount detection means 6 that detects the
light amount detection means 6 within a predetermined readout scanning period of
Charge sweeping means 7 is provided to determine that the photoelectric conversion means 5 performs a pseudo readout process for sweeping out the accumulated charge of the accumulation type image sensor 4 at a timing corresponding to the amount of light detected by the accumulation type image sensor 4. This is to prevent the sensor 4 from becoming saturated.

[Effect]

The photoelectric conversion device according to the present invention suffers from saturation and -c scratches when the amount of light fluctuates greatly due to the insertion of pseudo read processing. Since the accumulated charge of the storage type image sensor is swept out in the middle of a predetermined readout process, a saturation state does not occur in the storage type image sensor, and an output with a sufficient dynamic range can be obtained. [Embodiment] An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, components corresponding to those shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted. The light amount detection means 6 detects the amount of light from the light source 1 and outputs the detection result. The charge sweeping means 7 causes the photoelectric conversion means 5 to sweep the accumulated charge of the storage image sensor 4 at a timing corresponding to the amount of light detected by the light amount detection means 6 within a predetermined readout scanning period of the storage image sensor 4. This is to determine whether to perform a pseudo (dummy) read process to cause the data to be read. That is, the charge sweeping means 7 performs signal output readout processing for reading out the output of the accumulation type image sensor 4 at a predetermined readout scanning period by the photoelectric conversion means 5 according to the output of the light amount detection means 6, and the accumulation The time difference with the pseudo readout process for sweeping out the accumulated charge of the type image sensor 4 is switched.

Next, the operation of this embodiment will be explained. Light emitted from a light source 1 is reflected by a document surface 2, and this reflected light is collected by an optical system lens 3 and formed into an image on an accumulation type image sensor 4. The photoelectric conversion means 5 is an accumulation type image sensor 4
At the same time, the output is quantized and output to the outside. At this time, the light amount detection means 6 constantly detects the light amount of the light source 1. Based on this detection result, the charge sweeping means 7 determines at which timing among a plurality of preset readout timings within one readout scanning period of the storage type image sensor 4 the pseudo readout process is to be performed. , outputs a timing signal for causing the photoelectric conversion means 5 to perform pseudo read processing. Therefore, the storage type image sensor 4 is subjected to signal output readout processing for outputting to the outside by the photoelectric conversion means 5 once within one readout scanning period, but if the storage type image sensor 4 is saturated in this scanning period. In this case, pseudo read processing is performed once at an appropriate time. For example, when the light amount of the light source 1 is twice the optimum light amount in a certain scanning period, the photoelectric conversion means 7 causes the charge sweeping means 7 to perform a pseudo readout process in a half cycle of the next signal output readout process. Outputs a timing signal to. As a result, the exposure time of the storage type image sensor 4 is relatively shortened, and the storage type image sensor 4 is prevented from becoming saturated.

In the above embodiment, the light amount detection means 6 constantly detects the light amount of the light source 1, and the charge sweeping means 7 determines the timing for sweeping out the accumulated charge of the storage type image sensor 4 according to the detected light amount. However, the light amount detection means 6 does not need to constantly detect the light amount of the light source 1. For example, in the case of an image sensor, the light amount is detected at the beginning of reading the document, and the charge sweeping means 7 detects the amount of light. The timing for discharging the accumulated charge may be determined according to the amount of light, and the amount of light may be detected until the reading of the document is completed.

charge sweep for determining that the photoelectric conversion means performs a pseudo readout process for sweeping out the accumulated charge of the storage type image sensor at a timing corresponding to the amount of light detected by the light amount detection means within a predetermined readout scanning cycle; Since the exposure time of the storage type image 7/s can be changed even when the light intensity of the light source changes greatly, the storage type image 7/s is not saturated and the S/N ratio is reduced. The effect is that it is possible to provide a highly accurate photoelectric conversion device without having to do so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a photoelectric conversion device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional photoelectric conversion device. 1...Light source, 2...Document surface (ugly object to be inspected), 4...
Storage type image sensor, 5... Photoelectric conversion means, 6...
- Light amount detection means, 7... Charge sweeping means. Agent Masu Oiwa A (and 2 others) Figure 2 Procedure amendment (self
Column for name of the invention Photoelectric conversion device 3, person making the correction Representative Moriya Shiki 5, and detailed description of the invention to be corrected. 6. Contents of correction (11 Specification, page 7, line 5, ``Increase the amount of light until the interval'' is corrected to ``Increase the amount of light over a certain period of time until the interval''.)

Claims (1)

[Claims] In the photoelectric conversion device, the photoelectric conversion device includes an accumulation type image sensor that accumulates the amount of light reflected from the light irradiated on the detected object as a charge, and a photoelectric conversion means that quantizes the output of the accumulation type image sensor. A light amount detection means detects the amount of light irradiated onto an object, and the photoelectric conversion means accumulates light at a timing corresponding to the light amount detected by the light amount detection means within a predetermined readout scanning period of the storage type image sensor. What is claimed is: 1. A photoelectric conversion device comprising: charge sweeping means for determining to perform a pseudo readout process for sweeping out accumulated charges of a storage type image sensor, thereby preventing saturation of the storage type image sensor.