JPH07131606A - Image reader - Google Patents

Abstract

PURPOSE:To eliminate the blur or shift of images by making the timing to start the reading of image information coincide with the timing to move a reading target image for one line. CONSTITUTION:While the image information is fetched, the image information fetched by the last scan is converted into digital information by an A/D converting circuit 41 for each picture element synchronously with a clock from a clock generating circuit 40. This image information is subjected to white-and- black data correction by a shading correction circuit 43, and outputted digital raw sate are corrected by a gamma correcting circuit 43 and sent to an image processing circuit 45. Then, each process is entirely completed while a line sensor 33 fetches images for one line. When the next, horizontal synchronizing signal Hsync is generated, a pulse is similarly outputted from an image scan drive circuit 47 as well, a stepping motor 50 is rotated for one pulse, and the image information to be read by an image sensor 33 is moved just for one line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for reading an image of, for example, a microfilm with a line sensor.

[0002]

2. Description of the Related Art In an image reading apparatus in which an image on a microfilm is read line by line by a line sensor, a high precision is required for sub-scanning, so that it is very fine. A stepping motor that can obtain speed control and accurate position accuracy is used as a drive unit of the sub-scanning system. Generally, this stepping motor has a property that resonance may occur if the frequency of the drive pulse is too low, and that torque may become insufficient and step out may occur if the frequency of the drive pulse is too high. Optimal phase excitation control is performed within a frequency range where such a problem does not occur and within a range where a desired sub-scanning speed is obtained.

[0003]

However, in the conventional image reading apparatus which drives the stepping motor as described above, the sub-scanning speed is determined independently of the main scanning speed. There may be a case where a plurality of steps of sub-scanning are performed while the image for one line is captured, and in such a case, there is a problem that screen blur occurs and the image quality is impaired.

The present invention has been made in view of such conventional problems, and an object thereof is to provide an image reading apparatus for controlling main scanning and sub scanning in synchronization with each other.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a line sensor that captures image information of an image to be read line by line, and the image to be read in a direction perpendicular to the line sensor. A scanning unit that moves line by line; an image information capturing unit that captures image information from the line sensor; and a control unit that synchronizes the movement start timing of the scanning unit with the capturing start timing of the image information capturing unit. It is characterized by having.

[0006]

With this structure, the timing of starting the reading of the image information by the line sensor and the timing of moving the image to be read by one line match. For this reason, blurring or deviation of the image is eliminated, and the image quality can be improved.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an external view of an image processing apparatus including an image reading apparatus according to the present invention. Reader scanner 10
Has a function of projecting an image of the microfilm on the screen 11 and a function of electrically reading the image of the microfilm and sending it to the laser printer 12. The laser printer 12 prints an image on a microfilm electrically read by the reader scanner 10. Normally, the reader scanner 10 and the laser printer 12 constitute an image processing apparatus as a set, and these are mounted on the mounting table 15 as shown in the figure.

FIG. 2 is a diagram showing the internal structure of the reader scanner 10. A light source for irradiating light to the microfilm is provided at the lower surface side of the reader scanner 10 shown in the figure, and the light from the lamp 22 is condensed by the condenser lens 23 and is transferred to the microfilm placed on the microfilm carrier 24. Is irradiated.

The light passing through the microfilm is guided to the image rotation prism 26 via the projection lens 25. The image rotation prism 26 has a function of rotating the image from the projection lens 25 at an arbitrary angle. The image from this projection lens 26 is guided to a scanning mirror 27 which functions as a scanning means. The scanning mirror 27 has a function of switching between an optical path of a scanner system for electrically reading an image of a microfilm and an optical path of a reader system for projecting the image of the microfilm on a screen, and scanning the image of the microfilm during scanning ( And a function for performing sub-scanning). When the scanning mirror 27 is set at an angle as shown by the solid line in the drawing, the optical path of the reader system is set, and the image on the microfilm is reflected by the reflection mirror 28 and projected on the screen 11 in an enlarged manner. On the other hand, when the scanning mirror 27 is set at the angle shown by the dotted line in the figure, the optical path of the scanner system is set, and the image on the microfilm is reflected by the reflecting mirror 30,
It is guided to the line sensor 33 via 31. in this case,
A scanning operation (sub-scanning) is required to read the image of the entire microfilm, and this scanning operation changes the angle in synchronization with the reading of the scanning mirror 27 by the line sensor 33.

The image processing apparatus is normally set to the reader mode, and is set to the read mode when a read command is issued. FIG. 3 is a diagram showing a configuration for causing the scanning mirror 27 to perform a scanning operation. The scanning mirror 27 is attached to a control plate 35 as shown in the drawing, and the control plate 35 is rotatably supported by a support base 36. A pre-scan tip detection sensor 37 for detecting the tip position during the pre-scan is attached to one end of the control plate 35, and the set angle of the scanning mirror 27 during the pre-scan is controlled. The determination as to whether or not the scanning mirror 27 is set at the leader position is made by the leader position detection sensor 38 arranged so as to detect the end of the control plate 35.

Further, the control plate 35 is provided with a drive lever 39 which engages with the drive shaft of the stepping motor at a target position with respect to the scanning mirror 27. Therefore,
The angle of the scanning mirror 27 changes as the drive shaft rotates. As shown in the figure, the scanning mirror 27 is driven in the lying direction during the preliminary scanning, and is driven in the opposite direction during the main scanning. Therefore, the preliminary scan and the main scan are completed in one round trip.

Since very fine control is required to drive the scanning mirror 27, a stepping motor capable of precise speed control and position control is used in this embodiment. In the present invention, the sub-scan is performed in synchronism with the main scan. Therefore, it is necessary to have a mechanism / hardware that can synchronize the driving step of the stepping motor and the reading cycle for one line.

In the structure as in this embodiment, the scanning speed of the scanning mirror 27 changes depending on the ratio (gear ratio i) between the diameter φR of the drive shaft of the stepping motor and the diameter φQ of the drive lever 39. . Therefore, in the phase excitation setting of the stepping motor during image reading, the gear ratio may be configured such that the sub-scanning speed during reading becomes equal to the reading time of the line sensor 33.

The read time will be described with reference to FIG. When the reading operation is started in the reading mode, the transmitted light of the microfilm emitted by the lamp 22 is incident on the line sensor 33. Are sequentially transferred to the output section as analog signals pixel by pixel in synchronization with the clock signal CLK. When this transfer is completed for all pixels, the analog signal transferred to the output section is output to the peripheral device connected thereto in synchronization with the horizontal synchronization signal Hsync. Therefore, the time until the reading of all pixels is completed, that is, the generation time interval of the horizontal synchronizing signal Hsync becomes the reading time.

In the present embodiment, the sub-scanning speed is set as follows. It is assumed that the total scanning length L of the sub-scan shown in FIG. 5 is 305 mm and the rotation angle θ of the scanning mirror 27 is designed to be 10.2189 degrees.
Then, the horizontal synchronization signal time th set by the connected laser printer, that is, Hsync time is 0.001 s.
Assuming ec, the image reading speed V at a normal density with a reading density of 4000 dpi is V = (25.4 / 400) /0.00
1 = 63.5 msec.

If a stepping motor having a basic step angle of 1.8 degrees is scanned by 1-2 phase excitation in synchronization with the Hsync time, the stepping motor is set to have a step angle d of 0.9 degrees and a pulse rate. f is 100
0pps = 1 / th.

Under these conditions, if the reduction ratio of the stepping motor to the mirror is i, then (L / θ) · d
From (1 / i) = V / f, i = (305 × 0.9 × 1000) / (10.2189 × 63.5) = 423.023 Therefore, in FIG. 3, the reduction ratio of the worm wheel is 1 If the diameter φQ of the / 24 drive lever is 100 mm, the diameter φR of the drive shaft is (1 / i) = (1/24).
From (R / Q), R = 24 × 100 / 423.023 =
It becomes 5.6723 mm.

That is, in the above example, if the above design value is used, one driving step of the step motor is set to Hsy.
It becomes possible to synchronize with nc.

FIG. 6 is a block diagram of a control system of the image reading apparatus according to the present invention, which controls the operation of the hardware designed as described above.

In the figure, a line sensor 33 photoelectrically converts the light transmitted through the microfilm for each pixel and outputs an image analog signal. The image analog signal for each pixel is sequentially output to the A / D conversion circuit 41 in synchronization with the clock signal output from the clock generation circuit 40, where the image analog signal is converted into an 8-bit digital signal. The shading RAM 42 stores in advance the result of black and white data correction for each pixel of the line sensor 33, and the 8-bit digital data output from the A / D conversion circuit is stored in the shading RAM 42. The shading correction circuit 43 corrects the data based on the data. The data after this correction becomes appropriate digital raw data.

The γ correction circuit 44 is a part for correcting digital raw data which is output from the shading correction circuit 43 and which changes exponentially with respect to the image density so as to change the data linearly. The image processing circuit 45 is a portion that performs image processing such as an edit RAM area of an output area, negative / positive inversion, and halftone processing, and functions as an image reading unit. The external I / F circuit 46 controls data communication with peripheral output devices such as the laser printer 12.

The image scan drive circuit 47 functioning as a control means is a control circuit for sub-scanning by changing the angle of the scanning mirror 27 every second when the optical path of the scanner system is set. The stepping motor 50 is driven in accordance with the command. The lamp light amount control circuit 51 is a circuit for setting the light amount of the lamp 22 to a required brightness, which is also the CPU 48.
It is a circuit for controlling the brightness of the lamp 22 based on a command from. The CPU 48 is a system ROM
52, the sub-scanning speed to be supplied to the image scan drive circuit 47 is calculated based on the system data stored in the system RAM 53, and the reader / preliminary scan / main scan to be supplied to the lamp light amount control circuit 51 is performed. It has a function of calculating the required light amount. The control program stored in the system ROM 52 is activated when the power is turned on. The edit RAM 54 sets an output area in the image processing circuit 45, sets negative / positive inversion,
RA storing edit data for halftone processing
It is M.

The image reading apparatus of the present invention configured as described above reads an image as follows.

As shown in FIG. 7, the horizontal synchronizing signal H
With the occurrence of sync, a pulse is also output from the image scan drive circuit 47, and the stepping motor 50 rotates by one pulse to move the image information read by the image sensor 33 by one line. At the same time, the image sensor 33
Therefore, the acquisition of the image information is started.

While capturing image information,
The image information captured by the previous scan is converted into digital information by the A / D conversion circuit 41 pixel by pixel in synchronization with the clock from the clock generation circuit 40. The digitized image information is subjected to black-and-white data correction by the shading correction circuit 43 with reference to the information stored in the shading RAM 42. The digital raw data output from the shading correction circuit 43 is corrected by the γ correction circuit 44 and then sent to the image processing circuit 45. These processes are all completed while the line sensor 33 is capturing an image for one line, that is, until the next horizontal synchronizing signal Hsync is generated. When the next horizontal sync signal Hsync occurs,
Similarly, a pulse is also output from the image scan drive circuit 47, and the stepping motor 50 rotates by one pulse to move the image information read by the image sensor 33 by one line. At the same time, the image sensor 33 starts capturing the image information. Then, after that, the image processing described above is performed.

The generation of this horizontal synchronizing signal Hsync is based on the program stored in the system ROM 52, and is C
Although it is generated from the PU 48, when the pulse is generated to the stepping motor 50 by software, an interrupt is generated when the horizontal synchronizing signal Hsync is generated, and the stepping motor is generated in this interrupt processing. The pulse generation control to 50 may be performed.

If the pulse rate falls within the self-starting area, the stepping motor will be driven without step-out even if the pulse rate is suddenly applied, but if it is desired to drive at a pulse rate outside the self-starting area, acceleration / deceleration is performed. Requires processing. Therefore, when performing acceleration / deceleration, the generated horizontal synchronizing signal Hsync should be counted to output a driving pulse to the stepping motor for every predetermined number, and the number of the horizontal synchronizing signal Hsync should be gradually decreased. If so, acceleration control becomes possible. On the other hand, in the case of deceleration, deceleration control becomes possible by gradually increasing the number of the horizontal synchronizing signals Hsync.

[0028]

As described above, according to the present invention, the timing of starting the reading of the image information by the line sensor and the timing of moving the image to be read by one line are made coincident with each other. It is possible to improve the image quality.

[Brief description of drawings]

FIG. 1 is an external view of an image processing apparatus including an image reading apparatus according to the present invention.

FIG. 2 is a diagram showing an internal structure of the reader scanner shown in FIG.

FIG. 3 is a diagram showing a configuration for causing the scanning mirror shown in FIG. 2 to perform a scanning operation.

FIG. 4 is a time chart for explaining the reading time of the line sensor.

5 is a diagram showing an optical path of the scanning mirror shown in FIG.

FIG. 6 is a block diagram of a control system of the image reading apparatus according to the present invention.

FIG. 7 is a timing chart showing a state in which main scanning and sub-scanning of the image reading apparatus according to the present invention are synchronized.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Reader scanner 11 ... Screen 12 ... Laser printer 27 ... Scanning mirror (scanning means) 33 ... Line sensor 45 ... Image processing circuit (image information capturing means) 47 ... Image scan drive circuit (scanning means) 48 ... CPU (control) Means) 50 ... Stepping motor (scanning means)

Claims (1)

[Claims] 1. A line sensor that captures image information of an image to be read line by line, a scanning unit that moves the image to be read line by line in the vertical direction with respect to the line sensor, and image information from the line sensor. An image reading apparatus comprising: an image information capturing unit that captures the image information; and a control unit that synchronizes the movement start timing of the scanning unit with the capture start timing of the image information capturing unit.