JPH09205528A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read a normal image even when an original face is floated like a thick book binding by measuring a distance between an original from a light source with a distance sensor in real time and calculating and controlling an original scanning speed in real time based on the measured value. SOLUTION: As soon as a scanner 90 starts its operation, an emitted light from a light emitting section 85 of an optical distance sensor 21 is fed to a sense section 84 via an optical fiber 80, reflected in an original face and made incident again into a photoelectric conversion section 86 via the optical fiber 80. The photoelectric conversion section 86 generates data of a distance X between the original face and an original platen and the data are fed to a scanning speed calculation section 87. The scanning speed calculation section 87 calculates the scanning speed based on the data of the distance X and gives scanning speed data to a scanning speed control section 88 composed of an exciting circuit, a drive circuit and a pulse generating section. The scanning speed control section 88 controls a stepping motor 18 to drive the scanner 90 in response to the scanning speed data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image of an original by using an image sensor, for example, a digital copying apparatus or a scanner for outputting the read image data to a recording material such as paper. It can be applied to facsimiles, etc.

[0002]

2. Description of the Related Art For example, when a thick book is used as a document to be copied by a copying apparatus, the central binding portion, that is, the portion raised from the document holder is usually copied as a black line. Therefore, in the prior art, Japanese Patent Laid-Open No. 3-26127
As described in Japanese Patent No. 0, the black line is read as gradation data in the photo reading mode,
There is a method of making the image data easy to see by a means for avoiding the loss of data as much as possible and a mask processing means for forcibly erasing the portion corresponding to the black line and converting it to white.

For example, if the original to be copied is a thick book and an attempt is made to copy over both pages of the spread,
As shown in FIG. 3, in the bookbinding unit 5, the document holder 51
Can be divided into contact portions 52 and 52 in which the original is in contact with the surface of the document, proximity portions 53 and 53 in which the original is floating but can be read, and unreadable portions 54 in which the original cannot be read. As shown in FIG. 4, the image copied in this state is such that the contact portions 61 and 61 that are normally copied, the adjacent portions 62 and 62 that are reduced in the horizontal direction of the original, and the unreadable portion 63 that is a black line in the vertical direction of the original. An image for each part is output as shown in. The problem here is that the adjacent portions 62, 6 which are unintentionally reduced in the horizontal direction of the original document.
2. The unreadable portion 63 is a black line in the document vertical direction.

In the above problems, the unreadable portion 63 which becomes a black line in the vertical direction of the original can be improved by the means as described in Japanese Patent Laid-Open No. 3-261270 described above. No improvement can be made to the horizontally reduced proximity portions 62,62.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and it is possible to reduce the proximity portions 62, 62 that are reduced in the horizontal direction of the document. It is an object of the present invention to provide an image reading device capable of outputting a normal image without the above.

[0006]

According to the first aspect of the present invention,
In an image reading apparatus that optically reads an image of a document, a distance sensor that measures the distance to the document in real time, a scanning speed calculation unit that calculates the scanning speed of the document in real time from the data of the distance sensor, and the calculation thereof. And a scanning speed control means for controlling the scanning speed in real time based on the scanning speed data.

The invention according to claim 2 is characterized in that the distance sensor is provided in a light source portion which irradiates and scans a document.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a document reading apparatus according to the present invention will be described below. In FIG.
Reference numeral 11 indicates a document holder made of a transparent glass plate. The original to be copied is placed on the original holding table 11 with the original surface facing down. Further, the reference position of the document is set on the paper surface of FIG. 1, for example, on the left front side of the document holding table 11. Next, reference numeral 12 indicates a movable light source unit. As shown in FIG. 2, the movable light source unit 12 is composed of an optical distance sensor 21, light sources 22 and 22 composed of two fluorescent lamps arranged in parallel at a distance, and a scanning slit 23. ing. The optical distance sensor 21 is provided between the ends of the light sources 22 and 22. Further, in FIG. 1, reference numeral 17 is the light sources 22 and 22.
, A reference numeral 18 is a stepping motor for moving the movable light source unit 12 and a scanning mirror described later, reference numeral 1
Reference numeral 9 denotes a video processing circuit that processes an output signal from a photoelectric conversion element described later.

In FIG. 1, the light emitted from the movable light source unit 12 illuminates the document surface of the document holding table 11, and the reflected light is reflected by the scanning slit 23, the first scanning mirror 13,
The light enters the CCD 16 which is a photoelectric conversion element through the second scanning mirror 14 and the imaging lens 15, and an original image is formed on the light receiving surface of the CCD 16 and converted into a digital signal.

Next, the reading operation will be described with reference to FIG. First, the movable light source section 12 is turned on, and the movable light source section 12 is moved in parallel by the motor 18 by the guide rail 20 to the broken line section 12 'while the first scanning mirror 13 is attached. Therefore, the first scanning mirror 13 moves to the broken line portion 13 '. In addition, the second scanning mirror 14
Moves at a speed half the speed of the movable light source unit 12 and, at the same time, moves in parallel to the broken line portion 14 '. This difference in speed is for keeping the optical path length from the movable light source unit 12 to the CCD 16 constant.

The moving speeds of the movable light source unit 12 and the first scanning mirror 13 in the above-described operation process will be described. At the same time as the above movement, the optical distance sensor 21 provided in the movable light source unit 12 is used for the document surface 50 as shown in FIG.
The distance between the document holder 51 and the document holder 51 is measured. Here, the distance can be obtained from the difference between the distance between the optical distance sensor 21 and the document surface 50 and the constant distance between the optical distance sensor 21 and the upper surface of the document holder 11.

FIG. 5 shows a broken line frame portion in FIG. Here, as shown in FIG. 5, the distance between the document surface 50 and the document holder 51 is X, and the angle between the tangent line of the document surface 50 and the document holder 51 at a certain position P is θ. .
Further, as shown in FIG. 6A, the scanning speed V0 for scanning a certain fixed distance 1 in the scanning time t is 1 / t. For example, when an A3 landscape original (l = 420) is scanned at t = 2.50 seconds, the scanning speed V0 is 168.0 mm / s.
Here, the scanning speed is predetermined for each digital copying machine and is one of the main elements that determines the copying speed of the copying machine.

When the scanning speed V0 is set to a reference scanning speed for correctly scanning a document that is in close contact with the document holding table 51, a document forming an angle θ with respect to the document holding table 51 is
As shown in FIG. 6B, the image on the document holding table 51 is a reduced image in the scanning direction of lcos θ. If this is scanned at the scanning speed V0 as it is, an image reduced in the scanning direction is read as in the proximity portion 62 shown in FIG. Therefore, in order to correctly read this reduced image as l, this image lc
It is sufficient to scan osθ for the time t required to scan the image 1 at the reference scanning speed V0.

The scanning speed V (X) with the distance X between the document surface 50 and the document holder 51 as a parameter can be expressed by the following equation. V (X) = (lcos θ) / t = V0 × cos θ = V0 × {1-X ² / (V0 ² × t ² )} ^1/2

Further, the effective range of the scanning speed V (X) is within the readable distance of the distance X between the document surface 50 and the document holder 51. Therefore, assuming that the readable distance is X _th , the above formula V (X) is applied when the distance X between the document surface 50 and the document holder 51 is 0 ≦ X ≦ X _th (X _th << V0t). It is possible. However, when X exceeds X _th , V (X) = V0.

Next, the control operation will be described with reference to FIGS. 7 to 8. The optical distance sensor 21 includes a sensing section 84, an optical fiber 80, a light emitting section 85, and a photoelectric conversion section 86. Of these, the light source unit 1 of the scanner
2 (see FIG. 2) is a sense unit 84. At the same time when the operation of the scanner 90 is started, the light emitted from the light emitting portion 85 is sent to the sense portion 84 via the optical fiber 80 connecting the light emitting portion 85 and the sense portion 84, and after being reflected on the document surface 50. , And again enters the photoelectric conversion unit 86 via the optical fiber 80. Thereafter, the photoelectric conversion unit 86 creates data of the distance X between the document surface 50 and the document holder 51, and sends the data of the distance X between the document holder 51 to the scanning speed calculation unit 87. To be The data of the distance X can be obtained by a known method.
The scanning speed calculation unit 87 calculates the scanning speed from the data of the distance X sent, and sends the scanning speed data to the scanning speed control unit 88 including the excitation circuit, the drive circuit, and the pulse generation unit. The scanning speed control unit 88 controls the stepping motor 18 that drives the scanner 90 according to the scanning speed data. FIG. 8 shows the flow of the operation described above.

According to the embodiment described above, the distance to the original is measured by the distance sensor in real time, and the original scanning speed is calculated and controlled based on the measured value in real time. Even if the document surface is floated like the binding portion of, the normal image can be read without reducing the floating document surface in the scanning direction. Therefore, a normal copy can be obtained by importing the read data into a well-known digital copying machine and executing a series of electrophotographic wrestling such as charging, exposure, development, transfer and fixing of the photosensitive drum.

[0018]

According to the present invention, a light source portion for irradiating and scanning an original, a distance sensor for measuring the distance to the original in real time, and a scanning speed of the original in real time are calculated from the data of the distance sensor. Since the scanning speed calculation means and the scanning speed control means for controlling the scanning speed in real time based on the calculated scanning speed data are included, the document is like a binding part of a thick book, Even if it is floating, the part of the document that floats up from the document holder of the central binding part can be read by the scanner without being unintentionally reduced in the scanning direction, and special processing devices, means, etc. must be used. No, you can load a normal image. The present invention can be applied not only to a digital copying machine but also to an image reading device such as a scanner or a facsimile, and the intended effect can be obtained.

[Brief description of drawings]

FIG. 1 is an optical layout diagram showing an entire example of a digital copying apparatus having an image reading apparatus according to the present invention.

FIG. 2 is a perspective view showing a movable light source unit applicable to the image reading apparatus according to the present invention.

FIG. 3 is a front view showing an example of a document reading state by the image reading apparatus according to the present invention.

FIG. 4 is a mode view showing an example of a transfer sheet in a conventional copying apparatus.

FIG. 5 is a graph showing an example of a method of calculating a document scanning speed in the image reading apparatus according to the present invention.

FIG. 6 is a simplified diagram showing the above calculation method.

FIG. 7 is a flowchart showing a control process of the image reading apparatus according to the present invention.

FIG. 8 is a block diagram showing a control process of the image reading apparatus according to the present invention.

[Explanation of symbols]

 11 Document Holder 12 Movable Light Source 13 First Scanning Mirror 14 Second Scanning Mirror 15 Imaging Lens 16 CCD 18 Stepping Motor 21 Distance Sensor 87 Scanning Speed Calculator 88 Scanning Speed Controller 90 Scanner

Claims (2)

[Claims] 1. An image reading apparatus for optically reading an image of an original, a distance sensor for measuring the distance to the original in real time, and a scanning speed calculation means for calculating the scanning speed of the original in real time from the data of the distance sensor. And an image reading device having a scanning speed control means for controlling the scanning speed in real time based on the calculated scanning speed data. 2. The image reading apparatus according to claim 1, wherein the distance sensor is provided in a light source unit that irradiates and scans the document.