JPS5833357A - Image reader - Google Patents

Abstract

PURPOSE:To ensure an image with high quality without lowering the image resolution, by controlling the reading timing of an image sensor in case the black information is contained in the image information of a read-out scanning line. CONSTITUTION:The black information is detected in the image information by a black information detector 17 while the signal showing that image buffers 14-16 are in the writing mode is delivered. In such case, the black information signal is delivered. The image signal stored in a CCD7 is ignored by the black information signal, and the writing is carried out to the buffers 14-16 with the next reading signal to read out the image signal by the next reading signal. Then the reading timing is delayed by a degree larger than the difference between the transmission time of the scanning line containing especially the black information and the transmission time of the scanning line containing no black information. In such way, an image with high quality is obtained with no reduction of the image resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device C1, and more particularly to an image reading device C1 such as a facsimile machine that reads a plane image by dividing it into pixels.

A plane scanning type image reading device, such as a facsimile machine, which is applicable to C2, employs a method of compressing the redundancy of image information and reading it. In this type of device C2, the amount of information for each scanning line is different, and therefore the transmission time is different, so the sub-scanning frequency changes by 1 for each scanning line. As stepper motors have been widely adopted, open-loop control morphs have contributed to device simplification (2).

However, in recent years, as facsimile machines have become faster, the minimum transmission time for one scanning line has become shorter, from 1OrrL to 20m (6) and 101m to 5m (8).
It became necessary for the speed of the sub-scanning motor to follow this. However, because the inertial mass of the rotor itself of the stepping motor for sub-scanning is large, and the inertia of movable mechanical parts for reading such as the document transport roller is also large, a delay occurs in the sub-scanning operation. .

As a result, while the document is not moving in the sub-scanning direction, the image information of the six scanning lines is read, resulting in a decrease in the resolution between adjacent scanning lines, and in some cases (in some cases, the image may be distorted or information may be missing). .

In order to solve these inconveniences, methods have been proposed to increase the response speed of the stepping motor and to increase the reduction ratio of the sub-scanning drive system to reduce the inertial load applied to the motor.

However, if a method of increasing the response speed of the stepping motor is adopted, there are drawbacks such as an increase in the size of the motor as a whole and an increase in power consumption, and a further drawback that damping characteristics are significantly reduced. Furthermore, if a method of increasing the reduction ratio of the scanning drive system is adopted, it is necessary to use a motor with faster response characteristics, which requires a special motor and increases costs.

The present invention has been made to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a plane scanning type image reading device that can obtain good images without deteriorating resolution.

In order to achieve the above object in the present invention (f2), black information detection means is provided for detecting whether or not two black pixels exist in the scanning line image read by the image sensor. A structure is adopted in which means is provided to control the timing of reading the next scanning line information according to the output of the means (2).

Hereinafter, the present invention will be described in detail based on Drawing C and Embodiment C.

FIG. 1 is a block diagram showing a schematic configuration of a facsimile image reading device to which the present invention is applied.
2, and is generally fed 4 times by a stepping motor 3. Reference numeral 4 indicates a light source, and the image information, which is the reflected light from the image position of the light beam irradiated from the light source, goes up the mirror 5f2 and is guided to the lens 6, where it is imaged on the image sensor CCD 7, which is a photoelectric conversion element. be done.

The image information accumulated in the image sensor CCD 7 is stored in a buffer memory 9 (2), subjected to signal processing, and then sent to a transmission line via a modem IO.

The reference numeral 8 is a control device for the entire reading device, which controls the stepping motor 3, CCD 7, or buffer memory 9.
control.

FIG. 2 explains in detail the parts of the control device 8 and buffer memory 9 which are added to FIG.

In FIG. 2, the reference numeral 12 is a control section, and from the readout signal RCLK+2, the controller 11 of the image sensor CCD 7 transfers the image information (DATA) accumulated in the CCD 7 to the CCD clock (CCDCLK).
). At this time, the image information stored in the image buffer memory 14C is sent out on the transmission path via the modulator/demodulator 10, and if the image buffer 14 is empty, the control unit 12 sends the image information stored in the image buffer memory 14C to the CCD 7. To transfer the accumulated image information (DATA), set the image buffer 14 to the write state C:/\
゛Operate the sofa controller 13. Simultaneously [2, C
CCD for reading to CD controller 11
A control signal is output to apply a clock (CCDCLK) to the CCD 7, and the sub-scanning stepping motor 3 (transfers the document by 21 scanning lines).

Reference numeral 17 outputs an output when the image information read out by the black information detector (two black information is included), and controls the timing of outputting the read signal (RCLK) of the CCD 7 depending on the presence or absence of black information.

FIG. 3 is a time chart showing a specific operation. The state of the image buffers 14 to 16 is currently detected, and if there is an empty image buffer, the main control unit (CPU) in the control unit 12
etc.), a write signal (BXEC) to the image buffer is output. This signal is launched and the writable signal (
BWENA), and the predetermined accumulation time τ. If the period has elapsed, a read signal (RCLK) is output.

When the write enable signal BWENA is output, writing to the image buffer is started in synchronization with the read signal RCLKT.

At this time, a signal BBSY indicating that the image buffers 14 to 16 are in the write state is output. This belief-;-B
BSY is reset when a predetermined number of hits of the image signal DATA are written into the image buffer C2. Also,
Signal BB indicating that the image buffer is in the write state
A driving signal SMCLK for the sub-scanning stepping motor is output in synchronization with the rising edge of SY.

Signal B indicating that the image buffer is in the writing state (2)
When BSY is being output, the presence or absence of black information in the image signal DATA is detected. If there is even one pixel of black information, a black information signal BLACK is output. When the black information BLACK is output, the read signal RCLK is set to τ. It outputs at a shorter period τ1.

The black information signal BLACK is reset by the read signal RCLK. The write enable signal BWENA is reset by the read signal RCLK gated by the black information signal BLACK, and triggered by the read signal RCLK gated by the black information signal BLACK of the write signal to the image buffers 14 to 16 (two configurations). For example, the image signal A2 accumulated in the image sensor CCD7 with an accumulation time of τ1
(see Figure 3) is ignored and the next read signal RCLK
Writing to the image buffer is performed at , and the image signal A3 is read.

Considering the movement of the stepping motor 3 at this time, if the influence of the mechanical parts f2 such as the transport rollers is ignored, the movement of the document can be approximated by replacing the rotation angle (2) of the rotor of the stepping motor. .

That is, as shown in the lower part of FIG.
2 becomes information C2 which is almost the same as the image information A1 of scanning line 0 due to the delay of the rotor.

Here, if the reading timing is delayed by a time τ1 until the rotor moves by a predetermined amount, the image information A3 will correctly become the image information of the scanning line 1.

Here, in a device such as a digital facsimile device that compresses the redundancy of image information and transmits it, the time it takes to transmit scanning line information that does not include white information (2 times, compared to 1 time for black information).
It takes a long time to transmit the information of the scanning line, which also includes pixels.

Therefore, if the difference between the transmission time of a scanning line in which only one pixel of black information exists and the transmission time of a scanning line that does not include black information is set to 71 or more, the reading speed will not become slower than the transmission time.

FIG. 4 is a circuit diagram explaining the embodiment of the present invention in more detail, and FIG. 5 is a timing chart showing its operation. Here, the minimum transmission time of the scanning line containing black information (
Here, the storage time of the CCD 7 is set to be half the time (which is twice the transmission time of a scanning line that does not include black information).

In FIG. 4, reference numeral 17 is a black information detection circuit, and the CC
The image information DATA read by D7 is sent to the D terminal,
It is configured as a D flip-flop in which the readout clock CCDCLK of CCD 7 is connected to the clock terminal. When black information (LOW level) exists in the image information DATA, the output Q of Fujitsubu flop '18 is LOW.
Become W level. This is the black information signal BLACK(b).

Here, when the write signal BEXEC to the image buffer is output from the control section, it is latched by the flip-flop 21,
This becomes the image buffer write enable signal BWE NA (a).

Black information signal BLACK (bl and write enable signal BWE)
NA(a) is input to the Nants gate 22 of the delay circuit 20. In the delay circuit 20, B LACK (al and BWE
Gate 22 when both NA(a) and C2 are at HIGH level.
output, that is, the image buffer write request signal BWR
E(Xc) is set to LOW level, flip-flop Q,
T, that is, the image buffer write wait signal BWRDY is set to H.
Set to IGH level. The standby signal BWRDY reaches the HIGH level, and writing to the image buffer is started in synchronization with the readout signal RCLK of the CCD 7. At this time,
The signal BBSY, which is the Q output of the Fujitsubu flop 24 and which indicates that the image buffer is in the write state, goes to the HIGH level, and the main control unit [2] notifies that the image buffer is in the write state. At this time, a driving signal SMCLK for the sub-scanning stepping motor is output from the main control section in synchronization with the BBSY signal. Note that 25 is a CCD
BWE with a flip-flop that uses CLK as a clock input
ND(d) is a clock signal (generated two times synchronously and resets the D flip-flop 24, so that every second output signal <2B
The BSY signal is inverted to a LOW signal.

Moreover, good images can be obtained without deterioration of resolution.

As is clear from the above description (2), according to the present invention, when black information is included in the image information of the read scanning line, a configuration is adopted in which the reading timing of the image sensor is controlled, and in particular, black information is the scanning line transmission time, including
Since the delay is controlled to be longer than the difference from the transmission time of a scanning line that does not include black information, it is possible to provide an image reading device that can obtain good image quality without reducing resolution.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an image reading device to which the present invention is applied, and FIGS. 2 and 3 are block diagrams and timing charts showing details of the control circuit of the image reading device shown in FIG. , FIG. 4, and FIG. 5 are a block diagram and a timing chart of a control circuit showing one embodiment of the present invention. 1°°°Original 3...Stevinink' motor 7...Image sensor 17...Black information detector 1B, 21, 23.24...Flip-flop.

Claims (3)

[Claims] (1) In an image reading device equipped with an image sensor consisting of a multi-bit photoelectric conversion element and a means for conveying an original in a direction perpendicular to the scanning direction of this image sensor (2), the scanning read by the image sensor A black information detection means for detecting whether ≦1 black pixel exists in the line image information, and a means for controlling the timing of reading the next scanning line image information according to the output of the black information detection means are provided. An image reading device characterized by: (2) When the black information detection means C2 detects that a black pixel is included (only in the second case, the patent claim is characterized in that the black information detection means C2 is provided with a control means for delaying the timing of reading the next scanning line information). The image reading device according to scope 1. (3) Any one of claims 1 to 2, characterized in that the storage time of the image sensor is one integral multiple of the minimum image readout time when black information is included. The image reading device described in item 1.