JPH0641271U - Document reader - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide a document reading apparatus capable of obtaining a uniform output without inducing a decrease in S / N ratio. When the original 80 is read, the LED light source 75 emits irradiation light to the original 80. LED light source 75
Since both ends of the document 80 are arranged so as to approach the document 80, the distance between the both ends and the document 80 is reduced, and the amount of light emitted to both ends of the document 80 also increases. The original 80 reflects the irradiation light,
The reflected light enters the reduction lens 77. Since the amount of light emitted to both ends of the original 80 is increased, the amount of light reflected from the end of the original to the reduction lens 77 is also increased. Therefore, even if the reflected light is once converged and then diffused by using the reduction lens 77, the amount of light received by the light receiving elements at the central portion and the end portion of the CCD image sensor 70 becomes uniform.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device, and more particularly to uniforming read output.

[0002]

[Prior art]

 Generally, for reading with a document reading device such as a facsimile, there is a method of irradiating a document to be read with irradiation light from a light source and reading reflected light. As a light source used in this method, there are an LED (Light Emitting Diode) and a fluorescent lamp. FIG. 6 shows a document reading device using an LED as a light source. This original reading device is composed of an LED light source 75 in which a plurality of LEDs are arranged in a row, a reduction lens 77, and a CCD image sensor 70. The operation of the document reading device 70 is as follows. First, the LED light source 75 irradiates the original 80 with irradiation light. Then, the original 80 emits reflected light for the given irradiation light. The reflected light is once converged by the reduction lens 77 and then received by each light receiving element of the CCD image sensor 70. Then, the CCD image sensor 70 outputs a voltage according to the amount of received light and the like (lightness of the original).

It is assumed that a uniform original (blank original) is read using such an original reading device. In this case, the same voltage must be output from each light receiving element (center portion and end portion) of the CCD image sensor 70. However, the actual output waveform of the CCD image sensor 70 has a difference that the output voltage at the central portion is large and the output voltage at the end portions is small, as shown by the waveform WF1 in FIG. The reason is that since the contracted lens 77 is used to once converge the reflected light, the amount of transmitted light with respect to the reflected light at the center of the lens is large, but the amount of light at the end of the lens is small.

In order to eliminate the difference in output voltage as described above, a method of providing a shading plate 79 in front of the reduction lens 77 (on the side of the original) is adopted. This shading plate 79 is shown in FIG. The shading plate 79 blocks only the reflected light from the central portion of the reduction lens 77. 6 shows the waveform of the output voltage of the CCD image sensor 70 when the shading plate 79 is provided on the waveform WF2 of FIG. In this way, the shading plate 79 is provided so that the amount of light received by the light receiving elements at the center and the end of the CCD image sensor 70 becomes uniform. Therefore, the output voltage difference between the central portion and the end portion of the CCD image sensor 70 becomes small.

[0005]

[Problems to be solved by the device]

 However, the conventional document reading apparatus has the following problems. In the method of providing the shading plate 79, a uniform output (waveform WF2) is obtained by reducing the amount of light received at the center of the CCD image sensor 70 (see FIG. 5). Therefore, there is a problem that the amount of received light is reduced and the S / N ratio is deteriorated.

Therefore, an object of the present invention is to provide a document reading apparatus that can obtain a uniform output without causing a decrease in S / N ratio.

[0007]

[Means for Solving the Problems]

 The document reading apparatus according to the present invention is characterized in that both ends of the illumination means are arranged so as to come close to the document.

[0008]

[Action]

 In the document reading apparatus according to the present invention, both ends of the illumination means are arranged so as to approach the document. Therefore, the amount of light given to the photoelectric conversion means can be made uniform.

[0009]

【Example】

 FIG. 4 is a cross-sectional view of a facsimile apparatus 100 equipped with a document reading apparatus according to an embodiment of the present invention, and its configuration and operation outline will be described. The facsimile device 100 includes the following parts. The mounting table 5, the separation roller 25, the document reading sensor 30, the press roller 38, the discharge roller 35, the LED light source 75, the first mirror 73, the second mirror 72, the reduction lens 77, and the CD image sensor 70.

The operator places the document 80 on the mounting table 5 and performs a communication operation. When the line with the other party is connected, the original 80 is taken in by the separating roller 28. After the leading edge of the document 80 that has been taken in passes through the document reading sensor 30, the document 80 is fed by a predetermined distance and positioned at the reading position. After that, the LED light source 75 irradiates the original 80 with irradiation light for reading. On the other hand, the original 80 emits reflected light with respect to the given irradiation light. The reflected light from the original 80 enters the reduction lens 77 via the first mirror 73 and the second mirror 72. The reflected light is once converged by the reduction lens 77, diffused, and received by each light receiving element of the CCD image sensor 70. By this light reception, the CCD image sensor 70 outputs a voltage according to the amount of light received (light and shade of the original). The document 80 after being read is sandwiched between the press roller 38 and the discharge roller 35 and discharged from the discharge port 95.

FIG. 1 shows a schematic view of a document reading device provided in the facsimile apparatus 100 shown in FIG. As shown in FIG. 1, both ends of the LED light source 75 are bent so as to approach the original 80. As a result, the distance from the both ends of the LED light source 75 to the original 80 is reduced, and the amount of light to both ends of the original 80 is also increased. Therefore, the amount of reflected light from both ends of the original 80 also increases, and the amount of reflected light in the central portion and the amount of reflected light become substantially equal.

Next, FIG. 3 is a partially enlarged view showing the positional relationship between the LED light source 75 shown in FIG. 1 and the original 80. As shown in the figure, in this embodiment, both ends of the PC board (wiring board) 82 are bent, for example, by 5 °, and the LED light source 75 is mounted thereon. Therefore, as described above, the distance from the both ends of the LED light source 75 to the original 80 becomes shorter, and the amount of light reflected from the edges of the original to the reduction lens 77 increases. In this way, even if the reflected light is once converged by the reduction lens 77 and then diffused, the amount of light received by the light receiving elements at the central portion and the end portion of the CCD image sensor 70 becomes uniform.

As a result, the output waveform of the CCD image sensor 70 becomes the waveform WF3 shown in FIG. In addition to the waveform WF3, FIG. 2 also shows the waveforms WF1 (output waveform when the shading plate 79 is not used) and WF2 (output waveform when the shading plate 79 is used) shown in FIG. As is clear from comparing these three waveforms, the waveform WF3 is different from WF2 in that the output at the end of the CCD image sensor 70 is not lowered and the S / N ratio does not deteriorate.

As described above, in the document reading apparatus according to the present embodiment, it is possible to obtain a uniform output without lowering the S / N ratio.

In the present embodiment, the PC board 82 is bent and the LED light source 75 is mounted thereon in order to bring both ends of the LED light source 75 closer to the original. However, another method may be used, for example, a method of inserting a spacer between the PC board 82 and the LED light source 75. Further, in this embodiment, the angle at which the PC board 82 is bent is set to 5 °, but it may be appropriately changed depending on the relationship between the original 80, the reduction lens 77, the CCD image sensor 70, and the like.

[0016]

[Effect of device]

 In the document reading apparatus according to the present invention, both ends of the illumination means are arranged so as to approach the document. That is, the amount of light given to the photoelectric conversion means can be made uniform.

Therefore, it is possible to obtain a uniform output without lowering the S / N ratio.

[Brief description of drawings]

FIG. 1 is a schematic view of a document reading apparatus according to the present invention.

FIG. 2 is a diagram showing output waveforms of the document reading device shown in FIG. 1 and a conventional document reading device.

FIG. 3 is a partial enlarged view showing the positional relationship between the LED light source shown in FIG. 1 and a document.

4 is a cross-sectional view of a facsimile device 100 including the document reading device shown in FIG.

FIG. 5 is a diagram showing an output waveform of a conventional document reading apparatus.

FIG. 6 is a schematic view of a conventional document reading apparatus.

[Explanation of symbols]

 70: CCD image sensor 75: LED light source 77: Reduction lens 80: Original

Claims (1)

[Scope of utility model registration request] 1. An original reading apparatus comprising an illuminating means in which a plurality of light sources for irradiating an original are arranged in a row, and a photoelectric conversion means for detecting reflected light from the original and reading the light and shade of the original. A document reading device, wherein both ends of the illuminating means are arranged so as to approach a document.