JPS62165467A - Image sensor driving device - Google Patents

Abstract

PURPOSE:To stabilize an image sensor output in an optional effective image area and to improve an S/N by driving the image sensor at a low transfer frequency level in the required area of an image and at a high transfer frequency level in other areas. CONSTITUTION:An original 1 is projected by a light obtained from a light source 2, the reflected light from the original 1 is formed by a lens 3 and the formed image is read out by an one-dimensional image sensor 4. The number of picture elements of the original 1 is set up as a picture element line L and the required area of the original 1 is set up as the area of oblique lines surrounded by the picture element lines M, L and lines ls, li. To read out the image in the required area, the original 1 is carried quickly up to the line ls and a read start picture element signal 1a and a read end picture element signal 1b are outputted from a controller 9 so as to correspond to the lines M, L. A CCD sensor driving circuit 7 controls the reading of the sensor 6 based on the signals 1a, 1b, a signal processing circuit 8 extracts the image from the sensor 6 and said operation is repeated up to the line li to stabilize the output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image sensor driving device used in, for example, an image scanner or a facsimile.

[Conventional technology]

FIG. 2 is a block diagram showing a conventional image sensor driving device disclosed in, for example, Japanese Unexamined Patent Publication No. 60-24676. In FIG. 2, 1 is a document, 2 is a light source that illuminates the document, and 3 is a document. 1 is a lens that forms an image, 4 is a one-dimensional image sensor that reads the image formed by lens 3, 5 is a CCD sensor drive circuit that drives the one-dimensional image sensor 4, and 6 is an output signal of the one-dimensional image sensor 4. This is a signal processing circuit that shapes the waveform.

Next, the operation of a commonly used drive system will be explained using FIGS. 2 and 3.

In FIG. 2, light emitted from a light source 2 is reflected by an original 1, and this reflected light is imaged on a -dimensional image sensor 4 by a lens 3. The -dimensional image sensor 4 receives a pulse signal φ8. shown in FIG. 3 from the CCD sensor drive circuit 5. φ7 is supplied. The pulse signal φ is a signal that transfers the charge generated in the photoelectric conversion section of the one-dimensional image sensor 4 to the analog shift register in the image sensor, and the optical signal accumulation time is determined by the pulse period T. , becomes high level, so that the charges of all bits of the photoelectric conversion section are transferred to the analog shift register.

The signal charge transferred to the analog shift register is sequentially processed for each pixel in synchronization with a clock pulse signal φT with a pulse width Tp (TP - Tx /L) corresponding to the pitch 1-BL of the one-dimensional image sensor 4. The signal is input to the circuit 6, where it is waveform-shaped and a signal for one line is obtained.

Furthermore, by moving the document by one pixel in a direction perpendicular to the scanning direction of the one-dimensional image sensor 4 using a document feeder (not shown) and repeating the above operations in sequence, a two-dimensional image decomposed into line signals can be obtained. It will be done.

Furthermore, as a method for driving a one-dimensional image sensor when the number of effective read pixels is smaller than the maximum number of bits of the one-dimensional image sensor, a method disclosed in Japanese Patent Laid-Open No. 60-24676 will be described.

The maximum number of bits of the normal-dimensional image sensor 4 is 256.
The number of bits is often set to 512.1024.2048 pixels, etc., which is not the number of bits actually required for each device. Therefore, in the driving method described in Japanese Patent Application Laid-Open No. 60-24676, as shown in FIG.
Therefore, an image of the document is formed by the lens 3, and unnecessary pixels are shielded from light by a mask plate 41, and the pulse width T of the transfer lock signal φA shown in FIG.

The clock width is set to be T p = T x /P, thereby making it possible to lower the transfer lock frequency and obtain a stable output.

[Problem that the invention seeks to solve]

Conventional image sensor drive devices read documents using the operations described above, and the method of reading out the entire maximum number of bits of a -dimensional image sensor is wasteful when reading only a portion of the document. The method shown in No. 60-24676 had the drawback that the entire image could not be read out.

The above drawbacks will be explained in more detail below using FIG.

In FIG. 5, when an image on a document 1 is read by a one-dimensional image sensor in the direction indicated by the arrow, all pixels are usually read using the maximum number of bits of the image sensor. However, being able to read only the necessary parts of a manuscript is often convenient when editing the manuscript. For example, when reading the shaded area in FIG. 5, for example, 1. From the line! , the original is mechanically fed to the line, and the signal output for each line is
It would be better to obtain it from a CD sensor, but in that case, the effective pixels corresponding to the shaded part of the output of the CCD sensor are from the Mth pixel to the Nth pixel, so all L bits can be obtained with the same clock as described above. There is a lot of waste when reading. In addition, with a method that images only the required number of bits and blocks light from the rest, it is not possible to read any part of the image, so for example, only the M-N pixels in Figure 5 can be read, which has the disadvantage that the entire document cannot be read. there were.

This invention was made in order to solve the above-mentioned problems, and it is possible to read the entire document when reading a document or an image using a -dimensional image sensor, and it is also possible to read a one-dimensional image when reading an arbitrary part of the document. To provide an image sensor driving device capable of lowering the transfer lock pulse signal frequency per bit of an effective pixel portion of a sensor, and reducing the signal transfer time per line if the frequency is the same. .

[Means for solving problems]

The image sensor driving device according to the present invention is a driving circuit that drives a one-dimensional image sensor at a low transfer frequency in the effective pixel area and at a high transfer frequency outside the effective pixel area when reading a specified area of a document. and a signal processing circuit that extracts signals as valid image information only when driving at the low transfer frequency.

[Effect]

In this invention, since the -dimensional image sensor has no light-shielding portion, it is possible to read the entire document by making the effective pixel area equal to the width of the document. In addition, when reading out the effective pixel area, the one-dimensional image sensor is driven at a low transfer frequency in the effective pixel area, which improves the signal-to-noise ratio and makes it possible to stabilize the extracted output signal. If the transfer frequency is the same as the transfer frequency during pixel readout, the transfer frequency outside the effective pixel area is high, so the signal charge transfer time per line is shortened.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an image sensor driving device according to an embodiment of the present invention. In the figure, 1.2, 3.degree. 4 is the same as in FIG. 2, and the explanation will be omitted.

9 is a controller controlled by a program;
This is for specifying the required area in the document to be photoelectrically converted. 7 is 1 in the above required area from the controller 9.
1 by obtaining a readout start signal 1a and a readout end pixel signal 1b indicating the readout start position and readout end position in the line.
This is a signal processing circuit that extracts only effective pixel signals from line signals.

Next, the operation of an embodiment of the present invention is illustrated in FIGS. 1 and 5.

This will be explained using FIG. In FIG. 1, the operations until the original 1 is read by the one-dimensional image sensor 4 are the same as those in the conventional example shown in FIG. 2, so the explanation will be omitted.

Next, in FIG. 5, the case of reading a required area (shaded area in the figure) of the original 1 will be described using the block diagram of FIG. The one-dimensional image sensor 4 reads the arrow 1a and lb force direction image in FIG. Normally, the image in the direction of the arrow is read using the maximum number of bits of pixels of this one-dimensional image sensor. 72. To read the required area in FIG. The document is mechanically fed to the line, and then the controller 9 sets the readout start pixel signal 1a to M and the readout end pixel signal 1b, using the Nth pixel to the Nth pixel of the image sensor as an effective area.
is set as N and output to the CCD sensor drive circuit and signal processing circuit, respectively (However, Of, M≦N≦L). The CCD sensor drive circuit 7 receives a pulse signal φ8. at the timing shown in FIG. φ, is generated. In other words, the image sensor is driven at a high transfer frequency during the T1 period from the Oth pixel to the N-1st pixel, and at a low transfer frequency during the period 7231J1 from the Nth pixel to the Nth pixel, and the image sensor is driven at a low transfer frequency from the Nth pixel to the N-th pixel. The T3 period up to the end is driven at a high transfer frequency. However, M=
In the case of O, transfer at a high frequency during the T1 period is not performed. Similarly, in the case of NL, transfer at a high frequency during the T3 period is not performed.

The signal processing circuit 8 receives the readout start pixel signal 1a and the readout end pixel signal 1b from the controller 9, extracts only effective pixel information from the Nth pixel to the Nth pixel from the output signal of the one-dimensional image sensor 4, and outputs it as a line. Output as .

The above-mentioned operation is carried out by step-feeding the document 1 as shown in step 2 of FIG. By repeating the process up to the line, reading of the required area in FIG. 5 is completed.

From the above explanation, it can be easily understood that the transfer frequency during the effective pixel output period of the required area is reduced and the output signal of the one-dimensional image sensor 4 is stabilized (the signal-to-noise ratio is improved). Furthermore, if the transfer frequency during the effective pixel output period when reading the required area is the same as the transfer frequency when reading out the planned pixels, it is clear that the signal charge transfer time per line can be reduced compared to when reading out the planned pixels. . Furthermore, since the -dimensional image sensor is not shielded from light, it is possible to read the entire document by setting the required area to the entire document.

In the above embodiment, the document moving type image scanner was used as an example, but when using a -dimensional image sensor, the element arrangement direction is the main scanning, and the mechanical scanning in the direction perpendicular to the element arrangement direction is the sub-scanning. In this case, the sub-scanning mechanism is not limited to the document moving type described above, but may be a document fixed type image scanner in which the lens and the one-dimensional image sensor move and the document is fixed. be effective.

Further, the sub-scanning mechanism is configured to scan a document 1 as shown in FIG.
．． An image scanner in which the lens 3 is fixed and the one-dimensional image sensor moves in the sub-scanning direction may be used, and the same effects as in the above embodiment can be achieved.

Further, the sub-scanning mechanism is configured to scan a document 1 as shown in FIG. Lens 3. - the dimensional image sensor 4 is fixed;
It may be a mirror scan type image scanner in which the optical image moves by θ rotation of the galvano mirror 11,
The same effect as the above embodiment is achieved.

〔Effect of the invention〕

As described above, according to the image sensor driving device according to the present invention, the image sensor is driven at a low transfer frequency in a required area of a document, and at a high transfer frequency in other parts. , it is possible to further stabilize the image sensor output in an arbitrary pixel area, improve the signal-to-noise ratio, and also make it possible to read the entire document by specifying the entire document as the required area.

Further, when the transfer frequency during the readout period of the required area is made the same as the transfer frequency during all pixel readout, there is an effect that the signal charge transfer time per line can be shortened.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an image sensor driving device according to an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional example, Fig. 3 is a timing chart for explaining the conventional example, and Fig. 4 is a block diagram showing an image sensor driving device according to an embodiment of the present invention. FIG. 5 is a diagram showing a light shielding plate of a conventional one-dimensional image sensor.
6 is a timing chart for explaining the operation of FIG. 1, FIG. 7 is a diagram showing the second embodiment of the present invention, and FIG. 8 is a diagram of the present invention. It is a figure which shows the 3rd Example of invention. In the figure, 1 is a document, 2 is a light source, 3 is a lens, 4 is a one-dimensional image sensor, 7 is a CCD sensor drive circuit (-dimensional image sensor drive circuit), 8 is a signal processing circuit, and 9 is a controller. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A device for driving a one-dimensional image sensor with a total number of L pixels, in which 0 out of a specified readout start pixel M and a specified readout end pixel N (however, 0≦M≦N≦L) M-1 from the pixel
Driving a one-dimensional image sensor in which the T1 period up to the pixel and the T3 period from the N+1th pixel to the Lth pixel are driven at a high transfer frequency, and the T2 period from the Mth pixel to the Nth pixel is driven at a low transfer frequency. An image sensor driving device comprising: a circuit; and a signal processing circuit that receives a signal from the image sensor and performs signal processing of the input signal only when driving at the low transfer frequency. (2) The image sensor driving device according to claim 1, wherein the low transfer frequency is the same as the transfer frequency when reading out all pixels for one line of the original.