JPH05308474A - Picture reader - Google Patents

Abstract

PURPOSE:To devise the reader to light an original efficiently without production of unevenness and to adopt a structure offering ease of miniaturization. CONSTITUTION:An image forming light focusing lens array 20 and an image sensor 22 opposite to its on end face are supported by a case 24, a case opening opposite to the other end face of the lens array is covered by a transparent cover member 30 and an image forming light is transmitted from the front side of the transparent cover member toward the light focusing lens array on the rear side. The transparent cover member has a light diffusion face 32 extended in a strip in the lengthwise direction at the rear side of a glass plate 31 and a light shield layer 34 is provided to the rear side of the light diffusion face. A light of the light source is made incident from the end face of the transparent cover member in the lengthwise direction and the transparent cover member is used for a lighting guide system.

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 used in a facsimile machine or the like. More specifically, the present invention relates to an image reading apparatus that uses a transparent cover member as a light guide system for illumination by forming a light scattering surface on the transparent cover member that covers the opening of the housing.

[0002]

2. Description of the Related Art A typical configuration example of a conventional image reading apparatus is shown in FIG. This apparatus includes a light converging lens array 10 for image formation, and a large image sensor 12 that opposes one end surface (lower end surface in FIG. 6) of the array at a distance and photoelectrically converts it. The inside of the housing 1 is covered with a transparent cover glass 16 to cover the housing opening spaced apart from the other end surface (the upper end surface in FIG. 6) of the light converging lens array 10.
4 is a structure in which an LED (light emitting diode) array 18 in 4 illuminates the document surface from the back surface side of the transparent cover glass 16.

The light converging lens array 10 is an optical system in which a large number of rod lenses of the gradient index type are arranged to form one continuous image as a whole. The original 20 is pressed on the transparent cover glass 16 by the pressing drum 22 and is fed in a state of being in close contact with it. LED array 1
Reference numeral 8 denotes a large number of chip-shaped LED elements arranged in a line, which are attached to the housing 14 in a tilted state (tilt angle θ). As indicated by the one-dot chain line arrow, the illumination light from the LED array 18 illuminates the document 20 obliquely from the back surface side of the transparent cover glass 16, and the imaging light reflected on the document surface passes through the transparent cover glass 16. An image is formed on the image sensor 12 by the light converging lens array 10.

[0004]

The conventional image reading apparatus having such a structure has a feature that it can be considerably miniaturized.
On the other hand, however, the working distance of the rod lens is very short, so that the space for incorporating the illumination device becomes small, and the point of design is how to efficiently and uniformly illuminate the original. Of course, cost reduction is also important. In order to efficiently illuminate the document surface in this type of apparatus, it is necessary to bring the light source as close to the document surface as possible and to make the illumination light strike the document surface at a right angle.

However, since the LED array 18 has a structure in which a large number of chip-shaped LED elements are arranged and is not a continuous light source in the longitudinal direction, if it is arranged close to the document surface, the uneven illumination becomes large. On the other hand, there is a problem in that the illumination efficiency decreases when the distance is increased in order to suppress the uneven illumination.

Further, since the LED array 18 is large, it cannot be arranged at a position where it can be illuminated at right angles to the document surface. Therefore, since the illumination is performed in the oblique direction as described above, the brightness decreases as the tilt angle θ increases (the brightness is proportional to the cosine of the tilt angle θ), and the reflection on the transparent cover glass 16 is also caused by the oblique irradiation. It becomes large and cannot illuminate efficiently. In general, the lighting is inclined at about 45 degrees, so the efficiency is reduced by about 30%.

In addition, since the illumination is from an oblique direction and a certain amount of illumination space is required in order to reduce the unevenness between the chip-shaped LED elements, it is very difficult to make the size smaller than the current state.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to achieve high illumination efficiency and to prevent uneven illumination.
An object of the present invention is to provide an image reading device that can be easily miniaturized.

[0009]

According to the present invention, a light converging lens array for image formation and an image sensor facing one end face thereof are held by a housing, and the other of the light converging lens array is held. It is premised on an image reading apparatus having a structure in which a housing opening facing the end face is covered with a transparent cover member, and image forming light is transmitted from the front surface side of the transparent cover member toward the light converging lens array on the back surface side. Is. In the device, the feature of the present invention is that a light-scattering surface is formed in the longitudinal direction of the back surface or the inner surface of the transparent cover member, and a light-shielding layer is provided on the back surface of the light-scattering surface, in the longitudinal direction from the end surface of the transparent cover member. The point is that light from the light source is made incident and the transparent cover member is used as a light guide system for illumination.

[0010]

The light source light incident on the end surface of the transparent cover member proceeds while repeating total reflection along the longitudinal direction of the transparent cover member. A part of the light is scattered by the light scattering surface toward the center of the surface of the transparent cover member to illuminate the document surface. The light shielding layer formed on the back surface of the light scattering surface blocks the scattered light so that the scattered light does not go to the light converging lens array located on the back surface side. That is, in the present invention, the transparent cover member serves as a light guide system for illumination and serves as an illumination body. Since the light-scattering surface is formed in the longitudinal direction of the transparent cover member, the illumination light hits the surface of the document substantially evenly at right angles, and the illumination can be efficiently performed. In addition, a space for housing the light source inside the housing is unnecessary.

[0011]

FIG. 1 is a sectional view showing an embodiment of an image reading apparatus according to the present invention, which is an elongated structure extending from the front side of the paper surface to the back side thereof over a required document surface width or more. Is. In this device, the transparent cover member constitutes an illumination light guide system as shown in FIG. 3 is a front view of this device.

The light converging lens array 20 for image formation is held by the side surface thereof in the center of the housing 24. Then, the image sensor 22 is arranged so as to face one end surface (the lower end surface in FIG. 1) of the light converging lens array 20, and the image sensor 22 is placed in the housing 24.
Hold at the bottom of. A transparent cover member 30 covers a housing opening formed so as to face the other end surface (the upper end surface in FIG. 1) of the light converging lens array 20. The imaging light a is transmitted from the document surface to the light converging lens array 20 on the back surface side of the transparent cover member 30. Although not shown, the document is sent in a state in which it is pressed against the surface of the transparent cover member 30 by the pressing drum and in close contact with it, as in the conventional structure.

Here, the transparent cover member 30 is made of a glass plate-like body 31 whose front surface is polished, and has a light-scattering surface 32 in a belt shape in both longitudinal directions, which is slightly off the central portion in the width direction of the back surface thereof.
And a light shielding layer 34 on the back surface of the light scattering surface 32.
Is a structure that has formed. There is no light-scattering surface 32 or light-shielding layer 34 in the central portion of the glass plate 31 in the width direction (the portion indicated by reference numeral 33 that extends in the longitudinal direction in the shape of a strip), and that portion serves as the transmission optical path of the image-forming light a. The light scattering surface 32 may be, for example, a ground glass processed surface, and can be formed by grinding, sandblasting, or chemical etching using hydrofluoric acid or the like. Instead of the ground glass surface, a paint or an adhesive in which a light-scattering powder such as magnesium oxide is mixed with an epoxy resin may be applied. The light-scattering surface 32 is preferably provided as close as possible to a position right below the document reading portion as long as it does not hinder the transmission of the image-forming light. The light shielding layer 34 may be a reflective layer or a light absorbing layer. Specifically, it may be a light-shielding tape, a vapor deposition film, or the like, or a layer printed with a black resin by a screen printing method or the like.

As shown in FIG. 3, the light source 28 is arranged near both end faces of the transparent cover member 30 in the longitudinal direction, and the light from the light source is made to enter the transparent cover member 30 from both end faces. The light source may be a halogen lamp, an LED, or the like, or a method of introducing external light using a light guide bundle (a bundle of optical fibers). It is also effective to provide a light guide structure so that the light from the light source is efficiently incident from the end surface of the transparent cover member 30.

Light from the light source that has entered the transparent cover member from both end faces proceeds while repeating total reflection on the inner surface of the transparent cover member 30. By polishing the outer surface of the glass plate 31, the reflectance is increased and the light is guided efficiently. This light guide eventually strikes the light scattering surface 32 and is scattered. The light scattered and traveling upward illuminates the original surface efficiently and uniformly from a short distance. Further, of the scattered light, downward light is blocked by the light blocking layer 34 to prevent the light from entering the light converging lens array 20. This prevents a reduction in contrast.
The imaging light a reflected on the document surface passes through the transparent cover member 30 and is imaged on the image sensor 22 by the light converging lens array 20.

FIG. 4 shows another embodiment of the transparent cover member suitable for use in the present invention. Transparent cover member 40
Consists of a glass plate-like body 41 whose front surface is polished, forms a light-scattering surface 42 in a strip shape in the longitudinal direction on both sides, which is slightly deviated from the central portion in the width direction of the back surface, and forms the central portion in the width direction of the front surface and the back surface (bonding). This is a structure in which a reflective layer 44 is formed on the entire outer surface excluding the image light a transmitting portions 43a and 43b and both end surfaces.
The light scattering surface 42 may be, for example, a ground glass processed surface, or may be a coating film of light scattering powder. The reflective layer 44 may be a vapor deposition film or the like. In this way, most of the glass plate 41 is covered with the reflective layer 44.
By covering with, the reflectance on the inner surface of the glass becomes high,
The leakage of light from the light source is reduced, and the illumination efficiency is further improved.

FIG. 5 shows still another embodiment of the transparent cover member suitable for use in the present invention. The transparent cover member 50 is mainly composed of a combined body of two glass plate-like bodies whose surfaces are polished. The light absorbing layer 54 is formed in a strip shape in the longitudinal direction on both sides, which is slightly off from the central portion in the width direction of the upper surface of the lower glass plate 52.
And the light scattering surface 56 is formed on the upper surface of the light absorption layer 54. The light absorption layer 54 is a layer in which black resin is printed by a screen printing method or the like, and the light scattering surface 56 is a coating film of light scattering powder. The upper glass plate 58 is bonded and integrated with it by a transparent adhesive 60. The transparent adhesive 60 has
A material having a refractive index substantially equal to that of the lower glass plate 52 and the upper glass plate 58 is selected to reduce loss.
A reflective layer 62 is formed on the entire outer surface except the central portions (transmission portions of the image-forming light a) 61a and 61b of the front surface and the rear surface of this glass bonded body and both end surfaces. The reflective layer 62 may be a vapor deposition film or the like.
With this structure, the light scattering surface 56 comes closer to the original surface and is covered with the reflective layer 62, so that the reflectance on the inner surface of the glass is increased and the illumination efficiency is further improved.

[0018]

As described above, according to the present invention, the transparent cover member is used as the light guide system for illumination, and the light scattering surface and the light shielding layer are provided to illuminate the original surface. Since the illumination can be performed from the right angle and near the document surface, the illumination efficiency is improved. Further, since the illumination is performed by the scattered light from the light scattering surface that is continuous in the longitudinal direction, the uneven illumination is reduced.

In the present invention, since it is not necessary to install a light source such as an LED array inside the housing, it can be made very compact, and the light source light is introduced from the outside of the housing, so that the degree of freedom in selecting the light source is increased. Further, there is an advantage that the cost can be reduced because an expensive LED array is unnecessary.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is an explanatory view of a transparent cover member used for it.

3 is a front view of the device of FIG.

FIG. 4 is an explanatory view showing another example of the transparent cover member used in the present invention.

FIG. 5 is an explanatory view showing still another example of the transparent cover member used in the present invention.

FIG. 6 is a sectional view showing an example of a conventional image reading apparatus.

[Explanation of symbols]

 20 Light Focusing Lens Array 22 Image Sensor 24 Housing 30 Transparent Cover Member 32 Light Scattering Surface 34 Light Shielding Layer

Claims (1)

[Claims] 1. A housing opening portion in which a light-focusing lens array for image formation and an image sensor facing one end surface thereof are held by a housing and the other end surface of the light-focusing lens array faces the housing opening portion. In an image reading device in which image forming light is transmitted from the front surface side of the transparent cover member toward the light converging lens array on the back surface side of the transparent cover member. A light-scattering surface is formed, a light-shielding layer is provided on the back surface of the light-scattering surface, and light source light is made incident in the longitudinal direction from the end surface of the transparent cover member to make the transparent cover member an illumination light guide system. Image reading device.