JPH0425284A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain read picture information with fidelity to an original by preventing fluctuation of a reference voltage of an A/D converter due to reflection from the original. CONSTITUTION:A book original 18 is placed on a platen glass 17 while the original side is directed downward and a light radiates to the original from a fluorescent light 15a of an original lighting unit 15 of the optical scanning system and the original image is formed to a CCD(charge coupling device) 12 comprising plural photodetectors arranged in the main scanning direction by a lens 14. Moreover, a platen cover 19 pressing the original 18 onto the platen glass 17 closely and a shading correction white reference board 32 are provided to the reader. The reflection from the original is not reached by parting the position of, e.g. a side white color reference board from the original placing reference position and an accurate white level reference voltage is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that sends an image signal obtained by scanning an original image to an external device or the like.

[Prior Art] Conventionally, as shown in the internal cross-sectional view in the main scanning direction of FIG. Ta. 1
5 is an original illumination unit, 15a is a lamp, 17 is a platen gas, 18 is an original, and 19 is a platen cover.

[Problems to be Solved by the Invention] However, in the above conventional example, as shown in FIG. 5(b), the reflected light from the original 18 reaches the side white reference plate 40, so that an accurate white reference voltage cannot be obtained. was not obtained. To explain using an example of an actual read image (the actual circuit configuration is the same as that shown in Figure 3 described later), as a reading condition, first, the chart should be placed on the side white reference plate side as shown in Figure 7 (d). A chart is used in which there are white and black parts, and the rest is a uniform density of the play. The output is 2
The values, window position and size are Wl (Fig. 7(d)
)) and read. At this time, when the gray density is slightly lower than the slice level (when the binary output of the gray part is white), the conventional image reading device shown in Fig. 5 produces an image as shown in Fig. 12. is obtained. This phenomenon will be explained using FIG. 7.

FIG. 7(d) In the white part of the chart, as shown in FIG. 5(b), due to the reflection from the original 18, the brightness of the part a of the white reference plate becomes high, and the white reference voltage becomes high. (a). Therefore, the A/D of the original image reading signal
At the time of conversion output, the output of part a becomes high (b), and if the slice level is slightly higher than the density of the original uniform gray part, the binary output of part a becomes black, the binary output of part b becomes white, and they are the same. The density is different even when reading the original 8
This results in a forceful result. This is reproduced as phenomena such as black streaks even when the density is sequentially set to AE.

An object of the present invention is to provide an image reading device that solves the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a photoelectric conversion means for photoelectrically converting and reading a document on a document table, and a method for converting an output signal from the photoelectric conversion means into a digital signal. an analog/digital conversion means for outputting an output signal, a white reference plate located on the side of the document mounting table, and an output signal from the analog/digital conversion means based on the white reference plate.
In an image reading device having means for obtaining a white reference voltage and means for setting the white reference voltage in the analog/digital converting means, the white reference plate is configured to control reflection from the original on the original placing table. It is characterized by having a means for preventing.

[Function] According to the present invention, for example, by moving the position of the side white reference plate away from the document placement reference position, reflection from the document can be prevented (this makes it possible to obtain an accurate white reference voltage). .

[Example 1] Embodiments of the present invention will be described below with reference to the accompanying drawings.

(1)! FIG. 1 is an external perspective view of an embodiment of an image reading device to which the present invention is applied, and FIG. 2 shows its internal configuration.

In FIG. 2, 1 is a document image reading device (hereinafter referred to as a reader). This reader is a so-called “sheet” (
In other words, 1 g of a book manuscript (not necessarily a bound book, but may be in the form of a sheet) is placed on the platen glass 17 with the manuscript surface is placed face down and illuminated by the fluorescent lamp 15a of the original illumination unit 15 of the optical scanning system, and the CCD (CCD) consisting of a plurality of light receiving elements arranged in the main scanning direction by the lens 14 is exposed through the reflection mirror 16.
The device is configured to form an image of the document on the charge coupled device (charge coupled device) 12. This CGD 12 is a CCD driver I
3. 11 is a control unit which will be described later; 19 is a platen cover for bringing the document 18 into close contact with the platen glass 17; and 32 is a white reference plate for shape ink correction. Note that a side white reference plate is provided on the side (main scanning direction end) of the platen glass 17 at a predetermined distance from the document contact reference position.

Next, FIG. 3 shows a block diagram of the main circuit configuration of the device of this embodiment. This figure shows the main circuit parts of the COD driver 13 and control unit 11 in FIG.
A CD drive circuit, 21 is an amplifier, and 22 is an A/D converter. On the other hand, the control unit 11 includes a background density detection circuit 24, a binarization circuit 25, a selector 26, and an interforce circuit 27 for outputting to an external device. ROM 28A and RAM 2111B that store control procedures as shown in FIG.
CPo 2g, timing signal generation circuit 29 and its oscillator 30, gamma RAM 31. A D/A converter 33 is provided.

(2) Operation Next, the operation of the reader 1 according to this embodiment will be explained with reference to FIGS. 2.3 and 4. FIG. 4 is a sequence flowchart of the reading operation. The document 18 is placed on the platen glass 1 in FIG. 2 when the platen cover 19 is opened.
The original 18 is placed on the paper 7 so that the right end thereof becomes the leading edge of the original, and the platen cover 19 is bound to hold the original 18 and bring it into close contact with the platen glass 17.

The original illumination unit 15 of the optical system is configured such that the right end in FIG. 2 is the initial position (reference position), and the position is confirmed by an optical position sensor (not shown).

The reader 1 of this embodiment is always connected to an external device (for example, a digital printer, a personal computer, etc.) (not shown).
The communication of control signals with these external devices and the output of image signals from the hoop 1 to the external devices are performed by the interface circuit 27 (see Fig. 3).
It is done through.

Prior to the operation of the reader 1, commands for various modes are inputted from an external device. For example, set the density to 400 or increase the pixel density (dots/inch = dpi) to 400.
, 300, or 200, whether the image reading area is to be set at the position of the document, and whether the image is to be output in binary or multi-value, etc., are input. Upon receiving these instructions, the CPo 28 outputs a control signal to the timing signal generation circuit 29 and selector 26 in advance to set the pixel density and reading area position/size.

As shown in FIG. 4, when a document reading start command is input from an external device, first, in step S1, it is confirmed whether or not the document 18 is in the book position, and the CP
o 2g outputs a lamp control signal to light the lamp 15a of the original illumination unit 15 (step S2)
. Here, the reader 1 performs shading correction and starts scanning in the direction of the arrow in FIG.

From the initial position of the original illumination unit 15 to the platen glass 1
There is a distance of approximately 2 to 3+ nm from the position of the leading edge of the original on the document 7, and during this time, the scanning speed of the optical system is controlled to be stabilized by a pulse motor (not shown).

When the original illumination unit 15 reaches the above original position, C
Po 2g outputs a control signal to enable image signal output to the interface circuit 27, and the read images are sequentially sent to an external device (step S3).

The scanning length of the optical system is uniquely determined by the number of pulses that the CPU 28 drives a pulse motor (not shown), so the CPo 28 determines that document reading is complete when the required number of pulses is output to the motor. Judging, lamp 15a
is turned off (step S4), image signal output is disabled, motor reversal is controlled, and a document reading completion signal is output to an external device.

Due to the motor reversal control (step S5) of the CPU 28, the document illumination unit 15 moves in the opposite direction to the direction of the arrow in FIG. 2, and the optical position sensor (not shown) indicates that it has reached the initial position (home position). When detected (step S6), it stops (step S7). If the next document reading start command is not received from the external device during the return period of the optical system, the optical system stops at the initial position and ends the operation.

(3) Circuit operation Next, the circuit operation will be explained based on the block diagram shown in FIG. The CCD 12 on the CCD driver 13 in FIG. 2 is driven through the CCD drive circuit 23 by each timing signal generated by the timing signal generation circuit 29 on the control unit 11.

The image analog signal output from the CCD 12 is amplified by the amplifier 21 and converted into an analog/digital (A/
D) Input to converter 22. In this A/D converter 22, the image signal is converted from an analog signal into an 8-bit digital signal using a timing signal generated by a timing signal generating circuit 29, and is output to the control unit 11. In addition, here, the white reference data read from the side white reference plate is sent to the CPU 28, D
The voltage is set in the A/D converter 22 via the /A converter 33 as the white reference voltage for the next line.

The control unit 11 detects non-uniformity in the image signal level (shading and call)
is electrically removed by the shading correction circuit 20. This shading-corrected digital image signal is processed by the selector 26 into an output mode instructed by the external device, and is sent to the external device through the interface circuit 27.

(4) Position of the side white reference plate As shown in FIG. 6, the position of the side white reference plate 40 is
By moving the document away from the reference position, the lamp 15
There is light reflected from the original and the light reflected from the original does not hit the side white reference plate 40. Therefore, the fluctuation of the white reference voltage caused by the reflected light from the original as explained in FIG. As a result, the read image of the chart shown in FIG. 7(d) is as shown in FIG. 13.

In addition, as shown in FIGS. 8(a) and 8(b), by widening the width of the side white reference plate 42 (and using only the data in the center part), the influence of reflection can be eliminated, and the side white reference plate 42 can be Since it is possible to prevent dust from entering between the reference plate 42 and the platen glass 17, it is also possible to prevent fluctuations in the reference voltage due to dust.

[Example 2] Also, as shown in the above example, the side white reference plate 40
As shown in FIG. 9, by locating the document 18 at a position opposite to the abutment reference position, rather than on the abutment reference side, the distance from the document 18 is more convenient for comparison than if it were located on the abutment side. Since the target is often far away, it is possible to reduce the effects of reflection. Furthermore, by using this method, the size of the main body can be made smaller than by using the method shown in the above embodiment.

[Example 3] Next, a description will be given of means for blocking reflected light.

As shown in Figures 1θ (a) and (b), adjacent originals 1
A partition 43 is provided between 8 and a side white reference plate 40 to block reflection. It is also possible to provide a blocking wall 150 on the lamp 15a side (FIG. 11).

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain read image information that is faithful to the original by preventing fluctuations in the reference voltage of the A/D converter due to reflection from the original. .

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of an image reading device according to an embodiment of the present invention, FIG. 2 is an internal configuration diagram of the device, FIG. 3 is a block diagram of the main circuit configuration of the device, and FIG. 4 is a diagram of the reading operation. A diagram showing a flowchart, FIG. 5(a) is an internal sectional view in the main scanning direction of a conventional device, FIG. 5(b) is an explanatory diagram of reflection, and FIG. 6(a) is an image reading device according to an embodiment of the present invention. 6(b) is an explanatory diagram of reflection in the same embodiment. FIG. 7 is an explanatory diagram of the occurrence of black streaks. FIGS. 8(a) and (b) are other embodiments. FIG. 9 is an explanatory diagram of the reference plate position in another embodiment; FIGS. 10(a), (b), and 11 are explanatory diagrams for preventing glare in another embodiment; FIG. 12 is a diagram showing an example of a read image sample according to a conventional example, and FIG. 13 is a diagram showing an example of a read image sample according to an embodiment of the present invention. l...Reader (image reading device) 15...Original illumination unit, 15a...Light source (fluorescent lamp), 12...CCD. DESCRIPTION OF SYMBOLS 11... Control unit, 18... Document, 17... Platen glass, 40... Document side white reference plate, 19... Platen cover (Fig. Figure 5 Main scanning Noshun 5a Figure 6 Figure 8 Figure 9 Figure 10 Figure 10 Figure 12 Figure 13

Claims (1)

[Claims] 1) A photoelectric conversion means for photoelectrically converting and reading the original on the original table, an analog/digital converting means for converting the output signal from the photoelectric conversion means into a digital signal, and a side of the original placing table. a white reference plate located;
An image reading device comprising means for obtaining a white reference voltage based on the white reference plate from the output signal from the analog/digital conversion means, and means for setting the white reference voltage in the analog/digital conversion means, The image reading device is characterized in that the white reference plate has means for preventing reflection from the original on the original placing table.