JPH04123660A - Image reader - Google Patents

Abstract

PURPOSE:To suppress the degree of ''blurring'' to the minimum by generating an information light obtained through a document only in a period in which a light source is turned on. CONSTITUTION:A light source 11 is provided so that its longitudinal. direction coincides with the width direction of a document, and a turn-on period is controlled by a light source control part 13. A CCD 12 is constituted by providing an optical signal. accumulating part 12a and a shift register 12b. The optical signal accumulating part 12a is provided with a photodiode group in the longitudinal direction. Also, each photodiode is constituted so as to input a reflected light reflected by a document 15 and to accumulate optical. signal charge corresponding to an image. The shift register 12b outputs a picture data signal based on an optical signal. transferred from the optical signal. accumulating part 12a. In such a way, ''blurring'' in image read can be reduced without shortening the optical signal accumulation time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device that has been improved to reduce resolution degradation in the sub-scanning direction during image reading, specifically, to reduce so-called "blurring".

' and its amount The image reading device is, for example, an LED (LightEmitt
A light source consisting of a CCD (Ching Diode) and a CCD (Ch.
(large coupled device). The CCD includes at least a group of pixel photodiodes and a shift register. The operation of this type of image reading device will be explained as follows. That is,
The light source irradiates the document with light, and the reflected light (information light) reflected by the document enters the photodiode group.

The photodiode group accumulates optical signal charges corresponding to reflected light, and this optical signal charges are transferred to the shift register at a predetermined timing. And this shift register is
Image data signals based on the optical signals are sequentially output based on a predetermined clock.

FIG. 3 is a timing chart showing the timing required for the above operation. For example, the light source is turned on at the same time as the image reading operation starts, and continues to be turned on until the image reading is completed.

A period T in the control signal is an optical signal accumulation period, and at the end of this period T, optical signal charges are transferred to the shift register. The clock is used when sequentially outputting the image data signals from the shift register.

For example, the image reading device scans the original at 8 lines/IIl [1
It is configured to read at a density of 1, and every time one line is read, the processes of accumulation of optical signals, transfer to a register, and output of one image data are repeated.

By the way, when reading an image, it is necessary to move the reading lines in order, so the original document or COD is moved. Therefore, relative movement between the original and the COD occurs during the optical signal accumulation time T, and this movement has the disadvantage of causing so-called "shaking" in the sub-scanning direction in the read image. be.

Note that in order to reduce this, the optical signal accumulation time T
It is conceivable to shorten this optical signal accumulation time T
is set in consideration of the time required to send all signals from the shift register, etc.
It is difficult to shorten the time T by itself.

In view of the above circumstances, it is an object of the present invention to provide an image reading device that can reduce the above-mentioned "shake" without shortening the optical signal accumulation time T.

In order to solve the above-mentioned problems, an image reading device according to the present invention for "1. In an image reading device equipped with a reading means for accumulating optical signals of
The present invention is characterized in that it includes a light source control means that turns on the light source for each optical signal accumulation period for a period shorter than the optical signal accumulation period.

According to the above configuration, the information light obtained through the manuscript is
This occurs only while the light source is on.

Since the lighting period of the light source is shorter than the optical signal accumulation period, the information light acquisition period iJ is substantially shortened, and the actual amount of relative movement between the document and the reading means is also reduced accordingly. As a result, the degree of ``runout'' is suppressed to a small level.

Disaster-Jf6JL An embodiment of the present invention will be described below based on FIGS. 1 and 2.

In FIG. 1, 11 is a light source made of, for example, an LED;
2 is a CCD (reading means), 13 is a light source control section, 14 is a drive timing control section, and 15 is a document.

The light source 11 is provided so that its longitudinal direction coincides with the width direction of the document, and is configured to irradiate light onto the document 15 in a linear manner in the width direction. The lighting period of the light source 11 is controlled by the light source control unit 13, as will be described later.

The CCD 12 includes an optical signal storage section 12a and a shift register 1.
2b. The optical signal storage section 12a is provided so that its longitudinal direction coincides with the width direction of the document, and
This longitudinal direction and a group of photodiodes are provided. Further, each photodiode is configured to take in reflected light (information light) reflected by the original 15 and accumulate optical signal charges corresponding to an image.

The shift register 12b sequentially outputs image data signals based on the optical signals transferred from the optical signal storage section 12a in accordance with a clock described later.

FIG. 2 shows a timing chart of signals necessary for the above operation. The lighting period S of the light source 11 is set shorter than the optical signal accumulation period T, and is provided for each optical signal accumulation period. The period between the control pulses P and P is an optical signal accumulation period T, and the optical signal charge is transferred to the shift register 12b at the same time as the end of each period T. The clock is used when the shift register 12b sequentially outputs image data based on the optical signal.

The drive timing control section 14 generates each of the timing signals shown above, and outputs these timing signals to the CCDI 2 and the light source drive section 13 described above. C
The CD 12 transfers optical signal charges and sequentially outputs image data based on a control signal and a clock, and the light source driving section 13 performs a switching operation to control ON/OFF of the light source 11 based on a light source turn-on signal.

According to the above configuration, the information light obtained through the original 15 is generated only during the period S during which the light source 11 is turned on. The lighting period S of the light source 11 corresponds to each optical signal accumulation period T.
Since it is shorter, the period for capturing the information light becomes substantially shorter, and the amount of relative movement between the document 15 and the CCD 12 also decreases accordingly.

As a result, the degree of "shift" in image reading is suppressed to a small level.

Note that the insufficient light amount due to the lighting period of the light source 11 in each optical signal accumulation period becoming shorter than before can be solved by, for example, using a light source 11 with a high emission intensity, or
This problem can be solved by using a highly sensitive CCD 12.

Furthermore, in this embodiment, the start of the lighting period of the light source 11 is aligned with the start of the optical signal accumulation period, but it is possible to start from the middle of the optical signal accumulation period and end it in the middle, or to start from the middle of the optical signal accumulation period. It may be arranged to end at the end of the optical signal accumulation period. In addition,
If the lighting period of the light source 11 is divided into two parts, the beginning and end of the optical signal accumulation period, even if the information light acquisition period is substantially shortened, the actual distance between the document and the reading means will be reduced. This means that the relative movement amount will not change by 4 degrees, so try to avoid this.

Further, although the lighting period shortening control of the light source 110 is performed for each optical signal accumulation period as described above, it is not necessary to perform lighting period shortening control for all optical signal accumulation periods, and in this case, the lighting period It is possible to reduce the vibration in the part where the shortening control is performed.

According to the present invention, in which the total distance is Ω, it is possible to reduce "shaking" in image reading without shortening the optical signal accumulation time.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show an embodiment of the present invention, and FIG. 1 is an explanatory diagram showing a schematic configuration of an image reading device;
FIG. 2 is a time chart showing the drive timing of each component, and FIG. 3 is a time chart showing the drive timing of each component, showing a conventional example. 11...Light source, 12...CCD (reading means), 1
2a... Optical signal storage unit, b... Shift register, 3... Light source control unit, 4... Drive timing control unit, 5... Original document.

Claims (1)

[Claims] (1) In an image reading device that includes a light source that illuminates the original and a reading means that captures information light obtained through the original within an optical signal accumulation period and stores an optical signal corresponding to an image, the optical signal as described above is provided. An image reading device comprising: a light source control means for turning on a light source during an optical signal accumulation period for a period shorter than an accumulation period.