JPH02301365A - Picture reader - Google Patents

Abstract

PURPOSE:To prevent picture deviation due to interruption/restart without increasing the read time by using a position detection means provided in an original placing means to detect the road position of a scanning means. CONSTITUTION:An original placing means is provided with a position detection means 21 detecting a read position of a scanning means. When a host computer stops tentatively the reception of picture information, the optical system is stopped, the picture information is written in a storage circuit 211 and when the reception of the picture information is restarted, while the optical system is started, a scanning position detection circuit 212 is checked and whether or not picture information is written in the storage circuit 211 is discriminated to read the picture. Thus, picture deviation due to restart or stop of the optical system is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that reads an image of a document.

[Conventional technology]

In a conventional image reading device, a personal computer (hereinafter referred to as a host) is used as an output unit for image information, and a memory of about 256 bytes to 640 bytes is used within the device.

For example, when reading A4 size at 300 dpi and 1001% F, the amount of information output from the device to such a host will be more than 1 MB, so when transferring to the host, the image may be transferred depending on the host's convenience. It was possible to interrupt the

Conventional image reading devices use a pulse motor to stop the movement of the reading scanning means and to transfer the image information when the host instructs the reading to be interrupted. I was making an interruption.

When the transfer is canceled after the transfer is interrupted, reading resumes from the transfer interrupted position, but since there is a deviation in the reading position, the deviation in the reading position is corrected. The method is to return to the position where reading has already been completed, move the reading scanning means to the previous stop position, and then
Methods for restarting image transfer are known.

(Problem to be Solved by the Invention) However, when reading is restarted immediately from the interrupted position, it is difficult to prevent image shift caused by the interruption/resumption.

Additionally, there is a known method of slowing down the scanning speed to prevent image shift caused by interruption/resumption.
In this case, a new problem arises in that the reading time increases.

Furthermore, when resuming reading after interrupting the transfer,
A method is known in which the reading/scanning means returns to the position where it has already been read, moves to the interrupted position, and starts information transfer from the interrupted position. This method uses pulse
Although this method is effective in correcting positional deviations caused by backlash between the driving means such as a motor and the reading means, the problem arises that the reading time increases when interruptions and restarts occur frequently.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading device that solves the above-mentioned problems and can prevent image shift due to interruption/resumption without increasing reading time.

(Means for Solving the Problems) In order to achieve such an object, the present invention includes a document placing device for placing a document, a scanning device for scanning the placed document and reading an image. In the image reading apparatus, the document placing means includes a position detecting means for detecting a reading position of the scanning means.

(Function) In the present invention, the reading position of the scanning means is detected by the position detecting means provided in the document placing means.

(Example〕 DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

1 to 3 show one embodiment of the present invention.

(1) Configuration (Figs. 1 to 3) In the figure, 1 is an original M image reading device (hereinafter referred to as a reader), 2 is a reader main body, and 2 is a reader main body, and an original (image) is placed on a platen glass 27 as a mounting means. A document illumination unit 24 illuminates the document (downward), and a document image is formed via a reflecting mirror 25 onto a CCD (charge coupled device) 22 consisting of a plurality of light receiving elements arranged in the main scanning direction by a lens 26. It is composed. Original illumination unit 24
The mirror 25 is movable in a sub-scanning direction perpendicular to the main-scanning direction by a drive system (not shown). The reflecting mirror 25, the lens 26, and the CCD 22 constitute a scanning means.

21 is a control unit, 23 is a CCD driver, and the circuit configurations of both are shown in FIG. 28 is a document reference position indicator plate.

(2) Operation (Figure 2.3) The operation of the reader will be explained based on FIGS. 2 and 3.

The reader 1 is connected to an external device (for example, a personal computer, etc.), and communication of control signals with these external devices and output of image information signals to the external device are performed via an interface circuit 207.

The original is placed on the platen glass 27 with the image facing downward and the left end thereof serving as the leading edge of the original. In this state, instructions for various modes are manually given by an external device. For example, the pixel density is 400 dpi.

For example, whether to use 300 dpi or 200 dpi, or whether to convert the image signal into a binary signal or a multi-value signal.

Upon receiving this, the timing signal generation circuit 209
A control signal is sent to the selector 206 to set the pixel density and image signal. Next, from the external device, the original g4
When a reading start command is input, first, a lamp control signal is output to turn on the lamp of the document illumination unit 24. At this point, do not start scanning for document reading immediately, but wait for approximately 300 ms to 50 ms until the light intensity of the lamp stabilizes.
Wait for 0 ms.

During this time, the image signal is manually input to the storage circuit 211 through the selector 206, and then to the interface circuit 207, but the image signal is not output to the external device due to the control signal. Immediately after the lamp light intensity becomes stable, scanning of the original illumination unit 24 is started in the six directions shown by the arrows in FIG.

The distance from the initial position of the original illumination unit to the leading edge position of the original on the platen glass 27 is approximately 7111 to 8 mm, and during this time, the scanning speed of the optical system is controlled to be stabilized by a motor (not shown).

When the original illumination unit 24 reaches the leading edge position, it outputs a control signal indicating that image signal output is "enabled" to the interface circuit 207, and the read image signals are sequentially sent to an external device.

The scanning length of the optical system is uniquely determined by the number of pulses used by the C-Pυ208 to drive the motor, so when the required number of pulses are output to the motor, it is determined that document reading is complete, the lamp is turned off, and the image is The signal output is "disabled", the motor is reversed, and the original 1n reading completion signal is output to the external device.

By motor reversal control, the document illumination unit 24
It advances in the direction of arrow B shown in the figure and stops when the reference plate 28 detects that it has reached the initial position. If the next original 8% reading start command is not received from the external device during this optical system return period, the initial position is stopped and the series of operations is completed.

(3) Circuit operation (FIG. 3.5) Next, the circuit operation will be explained based on the circuit block diagram of FIG. 3 and the signal waveform timing chart shown in FIG. 5.

The CCD 22 on the CCD driver 23 shown in FIG. 1 generates each timing signal φ1. φ2. φ8. It is driven by φSH (FIG. 5) through the CCD drive circuit 203.

The image analog signal output from the CCD 22 is amplified by the amplifier 201 and converted into an analog/digital (A/D) signal.
) is manually input to the converter 202. In this ^10 converter 202, a timing signal φ generated by a timing signal generation circuit 209 is used. As a result, the image signal is converted from an analog signal to an 8-bit digital signal and output to the control unit 21.

The control unit 21 can output the input digital image signal to an external device in either of the two modes described above, that is, the binary mode or the multilevel mode. Which of these two modes is to be output is determined by a command from an external device, and the CPU 2-08 outputs a control signal to the selector 206. In the case of the multi-value mode, an 8-bit image signal is input to the selector 206, and after being selected and passing through the storage circuit 211, it is sent to the interface circuit 2.
07, the data is output to an external device.

In addition, in the case of binary mode, the CPU 2013 sets the slice level to the binarization circuit 205 in advance so that the binarization circuit 205 converts 8-bit image information into 1
The image information is converted into bit image information and manually inputted to the selector 206. There are two types of slice levels; one is information specified by an external device; in this case, this information is output as is (: PD 208 outputs it to the binarization circuit 205 as a slice level).

The other one is the background density detection circuit 204 in the image main scanning direction 1.
The maximum density value (the brightest value) for each line is detected, taken in by the CPt 1208, and the result of averaging several lines is output to the binarization circuit 205 as a slice level.

The image signal binarized in this way is sent to the selector 20.
6, is output to the memory circuit 211 in units of 8 pixels, and is output from the interface circuit 207 to an external device.

The storage circuit 211 has a capacity that can store 4 lines (4 punctures) of image information, and has an address counter for writing and reading only, which is set in advance by the CPO 208. It is necessary to keep it.

When the optical system is at the reading start position, a write permission signal is output to the storage circuit 211, and image information is written to the storage circuit 211 in synchronization with the sub-scanning synchronization signal, and
The bank (one of four is selected) in the storage circuit 211 is switched so that image information is written to another bank with the next sub-scanning synchronization signal. Thereafter, an image information transfer start signal is output to the interface 207 so that the image information written in the storage circuit 211 is output to an external device through the interface 207. The interface 207 reads one byte while controlling the readout of the memory circuit 211 and the address counter, and transfers it to an external device. When one line of image information has been transferred, this operation stops.
A 1 line transfer end signal is output to the CPO 208.

When the 1-line transfer end signal is received, an image information transfer start signal is output in synchronization with the next sub-scanning synchronization signal, and this is repeated until all lines are transferred.

(4) Pixel density conversion method (FIG. 6) Next, the pixel density conversion method performed in this embodiment will be explained.

6(a) to 6(C) respectively show two enlargements of the enable signal VE and the system clock signal CLK in the sub-scanning direction of the optical system of the reader 1, and the clock signal CL corresponding to one cycle of the VE signal. Show the diagram.

In FIG. 6(a), for example, when the pixel density is 400 dpi, one period of the VE signal corresponds to one line of the optical system scanner, and the period of the clock signal CL is as follows.
Each timing signal φ8. It has the same period as φ2 etc. (Fig. 5).

FIG. 6(b) shows the case where the pixel density is 200 dpi, that is, the pixel density of 172 in the case of FIG. 6(a), and the signal V
The periods of E and clock signal CL are 172 in the case shown in FIG. 6(a).

It is controlled by the VE multiplication signal CPt1208, and the
), the optical system scanning motor rotates and image signals are obtained at the same cycle, but the image signals are output to the external device only when the VE multiplied signal is active.

Furthermore, by controlling the timing generation circuit 209 by the CPU 208, the signal to CL is outputted to the background density detection circuit 204, the binarization circuit 205, and the interface circuit 207 as shown in FIG. ,
The image signal is sent to the interface circuit 2 once every two pixels.
Output on 07. Therefore, the main scanning and sub-scanning of the optical system correspond to 1/2 pixel density.

In FIG. 6(C), the pixel density is 174 as in FIG. 6(a), that is, 100 dpi.

(5) Optical system position detection method (FIGS. 4, 7, and 8) FIG. 4 shows a scanning position detection circuit 6 as a position detection means. As shown in FIGS. 7 and 8, the back of the document index board is marked with diagonal lines. The information on the back of the document index plate is latched by the selector 601 using the shaded area A signal generated by the timing generation circuit 209 and the signal VCL.
Write to 1-606. Although a latch is used here, a memory circuit may also be used. These latches 601-60
6 is read line by line from the CPO 208, and the previously read information is compared with the currently read information to detect the position of the optical system.

(6) Reading accuracy In reading, the reading operation may be temporarily stopped and restarted depending on the image information receiving method of the host computer.

As shown in FIG. 9(a), image information is disturbed due to the temporary stop (optical system stop) and restart (optical system start) of the reading operation.

In FIG. 9(a), Sl is the point in time when the optical system is stopped/started. From the image information cutoff shown in Fig. 9(a), it can be seen that the optical system overran when the optical system was stopped, and since the same information is from point S3 to point S52, there is a delay in starting the optical system at the time of startup. I know it was there.

Therefore, when the host computer temporarily stops receiving image information, the optical system is stopped and the image information is written into the storage circuit 211. However, if the scanning position detection circuit 212 is checked and the amount of movement with respect to the previous line is small, writing is not performed.

When the host computer resumes receiving image information, the scanning position detection circuit 212 starts up the optical system.
The image is read while checking whether to write the image information to the storage circuit 211 or not.

In this embodiment, an example in which a scanning position detection circuit is installed has been described, but a storage circuit for storing image information may be read from CPt1.

Further, in the present embodiment, the mark shown in FIG. 7 was attached to the document indicator board, but even if the mark shown in FIG.

[Effects of the Invention] As explained above, according to the present invention, since it is configured as described above, it is possible to prevent image shift caused by stopping and restarting the optical system.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the appearance of an embodiment of the present invention, Fig. 2 is a block diagram showing the structure of an embodiment of the invention, and Fig. 3 is a diagram showing a CCD driver/control unit circuit of an embodiment of the invention. 4 is a block diagram showing the scanning position detection circuit, FIG. 5 is a timing chart showing an example of the timing of each signal waveform, FIG. 6 is an explanatory diagram explaining the pixel density conversion method, and FIG. 7 is a block diagram showing the scanning position detection circuit. Figure 8 is an enlarged view of the original index plate shown in Figure 7. Figure 9 is a diagram showing the reading information of the original index plate. Figure 10 is an example of the original index plate. It is a figure showing other examples. DESCRIPTION OF SYMBOLS 1... Image reading device, 6... Scanning position detection circuit, 21... Control unit, 22... CCD. 23... CCD driver, 24... Original illumination unit, 25... Reflection mirror, 26... Lens, 27... Platen glass, 28... Original index plate. 1sjishiaki-many(1τ已F1a-cut inkstone diagram fig. 1)
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Claims (1)

[Scope of Claims] 1) An image reading device including an original placing means for placing an original, and a scanning means for scanning the placed original to read an image, wherein the original placing means An image reading device characterized by comprising position detection means for detecting a reading position of the means.