JPS61201562A - Optical image reader - Google Patents

Abstract

PURPOSE:To obtain a proper binary-coding output corresponding to a change in a background color of an original by changing a sensor output of an original at a region at read and scanning of the original in response to the total sum of sensor outputs at the preceding region to the said region. CONSTITUTION:A limit is given to a variable range of an optical storage time of a CCD sensor and the light storage time of the CCD sensor is not extended at a time or over even at total black level. Or, the light storage time of the CCD sensor is not shortened less than a time even at total white level. Thus, a limiter 10 is provided. In driving a pulse motor for feeding the original synchronously with a pulse controlling the light storage time of the CCD sensor, the part of the original of background having no information is carried faster an the part having image information of the original is fed at a speed corresponding to the quantity. Thus, the read speed is quickened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical image reading device, and particularly relates to an illumination system that irradiates light onto the surface of a document, and an optical transmission system that transmits light from the document. The present invention relates to an optical image reading device having a cell that outputs an electrical signal in response to light transmitted through the transmission system.

[Prior art]

Conventionally, in this type of optical image reading device, if the contrast of the image or text against the background color of the document to be read is poor, or if the amount of reflected light from the document surface decreases due to deterioration of the illumination system, etc. Means for automatically correcting and obtaining a constant binarized output have been carried out by adjusting the light source of the illumination system or by adjusting the slice level voltage of a comparator during binarization.

However, although adjusting the light source is a simple method,
There is a limit to the amount of light that can be adjusted because changing the amount of light emitted changes the distribution of the emission spectrum, and increasing the amount of light emitted reduces the lifespan. Furthermore, adjusting the slice level voltage of the comparator during binarization does not correct the analog output from the sensor, so there were problems such as a drop in the S/N ratio at low signal levels. .

[Purpose of the invention]

In view of the above-mentioned problems of the prior art, an object of the present invention is to obtain a signal with a high S/C ratio without affecting the emission spectrum distribution of the illumination system or the degradation of the life cycle, and to improve the image quality of the original. An object of the present invention is to provide an optical image reading device that can obtain an appropriate binarized output in response to color changes.

[Summary of the invention]

In order to achieve the above object, the optical image reading device of the present invention changes the light accumulation time of the sensor when scanning a certain area of a document according to the sum of sensor outputs in the area before the area. It is characterized by having means.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of an optical image reading device of the present invention.

In FIG. 1, 1 is a lamp of an illumination system, 2 is a document, 3 is a lens system, and 4 is a sensor, which is hereinafter referred to as a COD image sensor (hereinafter referred to as a CCD sensor). 5 is a comparator, 6 is an analog output accumulation circuit, 7 is a light accumulation time control pulse generation circuit, and 8 is a step motor control circuit. 9 is a step motor, and 10 is a limiter that determines the maximum and minimum limits of the light accumulation time. The light emitted from the lamp 1 of the illumination system is reflected by the original 2,
It passes through a lens 3 and is imaged onto a pixel of a CCD sensor 4. The CCD sensor 4 outputs an optical signal of an image as an electric signal depending on the amount of light incident on each pixel.

The CCD sensor 4 is connected to a comparator 5 and an analog output storage circuit 6, and the output of the CCD sensor 4, which enters the comparator 5, is binarized by comparison with the slice level voltage of the comparator 5 and becomes the final output. . On the other hand, the output of the CCD sensor 4, which enters the analog output storage circuit 6, is stored as an electrical output corresponding to all pixels in an analog quantity. The accumulation time of the CCD sensor in the next reading area is determined by the optical accumulation time control pulse generation circuit 7 in inverse proportion to this accumulated total output, and is fed back to the CCD sensor 4.

No. 9 The document or optical image reading device is fed by the lous motor 9, and set in the next reading area.
A feed signal 9 Lus is output from the Luss motor control circuit 8, the light accumulation time control signal 4 Lus generation circuit 7 latches the light accumulation time of the CCD sensor, and the analog output accumulation circuit 6 resets the accumulated analog output. after which the read operation begins.

The image on the document is read while the above-described operations are repeated, and this will be explained in detail with reference to the output signals of the CCD sensor in FIG. 2. Now, assuming that the output of the CCD sensor 4 in a certain reading area is as shown in FIG.・The light accumulation time of the CCD sensor 4 in the next reading area, which is the sum of . It is set equal to V8. Tsuma 夛N2=va...The relationship of (2) is set so that it holds true.

However, if control is performed so that the relationship in equation (2) is always maintained, the output of each pixel of the CCD sensor will be equal to the slice level of comparator 5 when a black or white area continues in the previous reading area. The voltage may exceed the voltage level or fall below the slice level voltage, making it impossible to determine whether the output of each pixel is black or white.

FIG. 3(&) is a configuration diagram showing each pixel of the CCD sensor when a black area continues, and FIG. 3(b) is a graph showing the output of the CCD sensor.

FIG. 4(,) is a configuration diagram showing each pixel of the CCD sensor when a white area continues, and FIG. 4(b) is a graph showing the output of the CCD sensor.

In Figures 3 and 4, the number of pixels of the CCD sensor is 7.
It will be explained as an individual. In FIGS. 3(&) and 4(a), each pixel of the CCD sensor corresponding to a black area of the document is shaded and corresponds to a white area. Distinguish from CCD sensor.

In FIGS. 3(a) and 3(b), if in one reading area 1, the document surface corresponding to pixels A1 to A7 is a continuous black area, in the next reading area 2, each of pixels A1 to A7 is The light accumulation time t1 is too long, and the pixel A corresponding to the black area of the document surface! s A3 e The slice level voltage (Vs) of the output comparator from A4 exceeds it, and all are judged to be white.

In FIGS. 4(a) and 4(b), if the document surface corresponding to pixels A5 to A7 in a certain reading area 3 is a series of white pixels, then in the next reading area 4, each of pixels A1 to A7 is Light accumulation time 1. is too short, and the image AleAspA, #A corresponding to the white area of the document surface.

The output from the converter is also equal to the slice level voltage (V
s), all are judged to be black.

Therefore, we set a limit on the variable range of the light accumulation time of the CCD sensor, so that the light accumulation time of the CCD sensor does not extend beyond a certain amount of time that is also the all-black level, or that the light accumulation time of the CCD sensor is kept below a certain amount of time that is also the all-white level. It is necessary to ensure that the time is not shortened. For this purpose, a limiter 10 is provided.

In the above embodiment, if the pulse motor for document feeding is operated in synchronization with the pulse that controls the light accumulation time of the CCD sensor, the portion of the document where there is no information can be rapidly fed.
By feeding the document at a speed corresponding to the amount of image information, the reading speed can be increased. In addition, in this embodiment, the sensor is described as a COD line image sensor, but it can also be used as a CID line image sensor, which is the same solid-state image sensor, an MO8 type line image sensor, or various image pickup tubes by using the mechanical scanning method. etc. can also be used.

〔Effect of the invention〕

As described in detail below, the image reading device of the present invention is provided with means for changing the sensor output in a certain area of the document during scanning of the document according to the sum of the sensor outputs in the area in front of the area. In particular, it is possible to obtain a signal with a high signal to noise ratio without affecting the illumination system's emission spectrum distribution or reducing its lifespan, and it can respond appropriately to changes in the background color of the original. Accordingly, it is possible to provide an optical image reading device that can obtain a binary output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical image reading device according to the present invention. FIG. 2 is a graph showing the output of the CCD image sensor. FIG. 3(,) is a configuration diagram showing each pixel of the CCD image sensor when a black area continues, and FIG.
It is a graph showing the output of the D image sensor. Fig. 4(,) is a configuration diagram showing each pixel of the CCD image sensor when a white area continues, and Fig. 4(b) is a configuration diagram showing each pixel of the CCD image sensor when the white area continues.
It is a graph showing the output of the D image sensor. 1... Lamp, 2... Document, 3... Lens system, 4
. . . CCD image sensor, 5 .
...Pulse motor, 10...Limiter agent Patent attorney Jo Taira Yamashita Figure 1 Figure 2 Figure 3 (b)

Claims (2)

[Claims] (1) Optical image that has an illumination system that irradiates light onto the document surface, an optical transmission system that transmits light from the document, and a sensor that outputs an electrical signal in accordance with the light transmitted by the transmission system. An optical image reading device, characterized in that the reading device has means for changing the light accumulation time of the sensor when reading and scanning a certain area of a document according to the sum of sensor outputs in an area before the area. . (2) The optical image reading device according to claim 1, wherein the sensor is a CCD image sensor.