JPS6179364A - Small-sized original reader - Google Patents

Abstract

PURPOSE:To utilize effectively luminous amount and to attain sharp reading at high speed by fitting a convex lens to an end face of a focusing rod lens array opposing to the original and fitting a concave lens to an end face opposing to a large-sized image sensor so as to collect the reflected light from the original. CONSTITUTION:The original 1 is moved, a light source 2 is placed on an original face to irradiate the original. The luminous flux subjected to irradiation and reflection as shown in dotted lines on an original face is introduced to a light leading system 13 and it is required for the arrangement of the system 13 close to the original 1 to refract the light for a length equivalent to the conjugate length by a convex lens. Thus, the convex lens 14 is mounted to the end face of the system 13 opposite to the original 1 so that the reflected ray is refracted and led to the system 13. Further, a concave lens 15 is fitted to the end face of the system 13 opposite to the sensor, the ray going straight in the inside of the system 13 is refracted and the image is formed to the sensor 4. Thus, the light reflected on the original is collected efficiently and enters the system and collected again on the sensor, the image is formed, then the brightness efficiency is improved remarkably.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a document reading device, which includes a contact type image sensor as a photoelectric conversion part, a small ring i-reading device including this, a light source, a light guide system, and a sensor. It is related to the device.

Generally, in small document reading devices, a glass focusing rod lens array (for example, the product name is Selfox Lens Array) is used as a light guide system.
Even if the sensor is not in close contact with the document, the light guide system allows the sensor to be in close contact with the document even in a non-contact manner by setting the distance between the document and the sensor to a conjugate length determined by the lens alloy. Similarly, the light from the original is imaged on the sensor at a ratio of 1:1, and the original can be read.

However, when such a focusing rod lens array is used, the ratio of the amount of light from the light source being reflected on the document surface, passing through the light guide system, and reaching the sensor is extremely low.
This method has the disadvantage that it cannot be achieved without using a light source with high luminance.

[Conventional technology]

FIG. 2 is a schematic cross-sectional view for explaining the light guide system of a conventional small document reading device. There is a document 1, which is moving in the direction of the arrow, and a light emitting diode is used as the light source 2. This light source is placed at a distance of approximately 5.0 mm from the document surface and irradiates the document with approximately 2000 lux, but light irradiation and light reflection occur on the document surface as shown by the dotted line. The light flux is incident on the light guide system 3 of the SELFOC lens array used as a focusing rod lens array, and the emitted light flux is about 4.5 mm from the other end surface of the light guide system.
The size of the document and the surface of the sensor 4 at a distance of 1:1
The image is formed to the size of , and the document is read.

However, the reading depth from the original is ±0 from the optimal position.
．． 3 mm, which means it has a fairly wide tolerance range.

However, the ratio of the amount of light finally input to the sensor to the amount of light from the normal light source is extremely small, at 1.5%.
Since it is about ~3.0%, it was necessary to increase the luminous intensity of the light source.

[Problems to be solved by the invention] □ In the small document reading device with the above configuration, when the amount of light projected from the light source is applied to the document surface, the light reflected from the document surface is diffusely reflected. The problem is that the amount of light that efficiently enters from the end face of the light guide system is small, resulting in a problem that the ratio of the amount of light that is finally input to the sensor becomes extremely small.

[Means for solving problems]

The present invention provides a compact document reading device that solves the above-mentioned problems. A convex lens is attached to the end surface of the focusing rod lens array facing the document, and a concave lens is attached to the end surface facing the large image sensor, so that light reflected from the document is focused and introduced into the sensor. This can be achieved by a document reading device characterized by the following configuration.

[Effect]

The present invention aims to minimize the gap between the document surface and the focusing rod lens array, since the amount of light irradiated from the light source to the document surface is diffusely reflected and scattered on the document surface, reducing light collection efficiency. to increase the amount of light incident on the convergent rod lens array, and on the other hand, to increase the amount of light incident on the end surface of the convergent rod lens array, the end surface of the convergent rod lens array is A convex lens is attached, and a concave lens is attached to the end face of the focusing rod lens array facing the large image sensor, so that light can be introduced into a sensor element with a small radius. It is.

〔Example〕

FIG. 1 is a schematic cross-sectional view for explaining the light guide system of the small document reading device of the present invention. There is a document 1, this document is moving, and a light source 2 is placed on the surface of the document. , the original is irradiated with approximately 2000 lux, and the light beam that has been irradiated and reflected on the original surface as shown by the dotted line is introduced into the light guide system 13, but as the light guide system 13 approaches the original 1, In order to arrange the document 1 with a conjugate length, it is necessary to refract it with a convex lens in order to make it correspond to the conjugate length. A convex lens 14 is attached to the end face of the light guide system 13 facing the sensor, and a concave lens 15 is attached to the end face of the light guide system 13 facing the sensor for the same reason.
The light beam that went straight through the inside of the sensor part 4 undergoes optical refraction.
The structure is such that an image is formed.

Normally, the element spacing of sensor elements arranged in an array is 8.
In the case of 1/mm resolution, it is about 10 μm to 30 μm, so it is necessary to use a lens with an appropriate refractive index that takes into account the conjugate length and to prevent mutual interference in imaging between adjacent elements. .

The light guide system of the document reading device configured in this way efficiently collects the light reflected by the document, enters the light guide system, and then condenses the light again and forms an image on the sensor, resulting in a remarkable luminance efficiency. It has advantages such as improved reading speed and no need for a particularly high-intensity light source.

(Effects of the Invention) As explained in detail above, the document reading device of the present invention has the great effect that it can perform high-speed and clear reading by effectively utilizing the amount of light, and can be provided by a high-quality device. .

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view for explaining the light guide system of a small original reading device of the present invention, and FIG. 2 is a schematic sectional view for explaining the light guiding system of a conventional small original reading device. I is the original, 2 is the light source, 13 is the light guide system, 14
15 indicates a convex lens, and 15 indicates a concave lens. Figure 1 Figure 2

Claims (1)

[Claims] In a document reading device comprising a light guide system consisting of a light source, a focusing rod lens array, and a large image sensor, a convex lens is attached to an end surface of the focusing rod lens array facing the document, and an end surface facing the large image sensor. 1. A compact document reading device, characterized in that a concave lens is attached to the device so that reflected light from the document is collected and introduced into the sensor.