JPS63271968A - Contact type image sensor - Google Patents

Abstract

PURPOSE:To enable an image sensor of this design to be small in size, low in price, high in sensitivity, and also high in driving speed by a method wherein a first and second photoconductive film are irradiated by the same light source, whose light ray is guided to the ends of the first and second photoconductive film so that the first and the second photoconductive films irradiate the surface of a manuscript and the photodetective face of a photodetective element respectively. CONSTITUTION:A first and a second photoconductive films 7 and 8, which are formed between a manuscript 4 and a photodetective element 2, are irradiated by the same light source 3 and the irradiating light is guided to the ends of the first and the second photoconductive films 7 and 8 through the said photoconductive film 7 and 8. And, the light ray emitted from ends of the first and second photoconductive films 7 and 8 irradiates the surface of the manuscript 4 and the photodetective face of the photodetective element 2 respectively, so that the light source 3 can be used as a light source for irradiating the manuscript and also a constant irradiating light source for the photodetective element 2 as well without an optical lens system. By these processes, the sensor small in size, low in price, moreover high in sensivity, and high in driving speed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an improvement in a contact type image sensor suitable for use in facsimiles and character image reading/input devices.

<Prior Art> Generally, in an image reading device using a line sensor, information on a document illuminated by a fluorescent lamp or an LED (light emitting diode) array is imaged onto a sensor through an optical lens or a rod lens array. Alternatively, the sensor is configured to read two-dimensional information by moving the sensor.

Conventional image reading devices use a CCD (charge-coupled device) as a light-receiving element, and have a configuration that combines this CCD with an optical system, or a configuration that combines a contact image sensor and a rod lens array. There is something. In particular, the latter has been developed in recent years with the aim of making facsimiles smaller and cheaper.

In addition, as a photoelectric conversion film constituting a contact image sensor, a type that uses an amorphous silicon thin film (a-5i) to form a photodiode, or a type that uses Cd5-CdSe
There is a type that uses a solid solution to form a photoconductive cell.
Both have their advantages and disadvantages.

First, when an amorphous silicon thin film is used, it exhibits a high-speed response to signal light, so high-speed driving is possible. However, since it is an independent driving method, it requires a large number of driving ICs, which poses a cost problem. However, the yield and reproducibility of sensor characteristics are also poor. On the other hand, when using Cd5-CdSe solid solution,
Since a matrix drive method can be adopted, the cost of the drive circuit can be reduced and a highly sensitive sensor can be obtained. However, since the response speed to signal light is inferior to that of amorphous silicon thin films, high-speed driving has been considered difficult.

Therefore, recently, in order to improve this optical response speed, a method of superimposing stationary light on top of the signal light incident on the light receiving sensor surface has been studied. This effect is due to the fact that the traps involved in the photoresponse are filled to some extent by stationary light, so the number of traps involved in the photoresponse of the signal light is reduced.

<Problems to be Solved by the Invention> Conventionally, contact type image sensors have naturally had a limit to miniaturization because information from a document is imaged onto the sensor through a rod lens array.

FIG. 2 is a cross-sectional view showing the structure of a conventional general contact type image sensor, in which 11 is a substrate, 12 is a light receiving element, and 13 is a
1 is an LED array light source, 14 is a document, and 15 is a rod lens array. In the type shown in FIG. 2, it is necessary to separate the long conjugate document 14 of the rod lens array 15 from the sensor, and the thickness of the contact type image sensor unit is usually 20 to 30 mm. Furthermore, since a lens system is used, optical adjustment is required, and there is also the problem of a reduction in light transmission rate.

In addition, as mentioned above, in order to obtain a high optical response speed, a contact image sensor is constructed using a Cd5-(d5e solid solution as a photoelectric conversion film) and irradiates the sensor surface with constant light in addition to the signal light, as shown in Figure 3. The contact image sensor having the structure shown in FIG. 3 has a light source 16 for emitting constant light in addition to the LED array light source 3 for emitting signal light onto the document 14 as shown in FIG. cost,
Furthermore, problems arise in terms of miniaturization.

The present invention was devised in view of the above two problems, and uses a single light source as a light source for irradiating a document and a light source for irradiating steady light to a light receiving element without using a lens system. ,
The purpose of the present invention is to provide a contact image sensor that is smaller in size, lower in price, and capable of high sensitivity and high-speed driving.

<Means for Solving the Problems> In order to achieve the above objects, the contact image sensor of the present invention comprises: a first light-guiding film that guides irradiated light from a light source to a document to be read; and a second light guiding film for irradiating the light receiving surface of the reading light receiving element with irradiated light from the same light source as constant light, and the first and second light guiding films are connected to the original document. and the light-receiving element, the light source guides light to the ends of the first and second light-guiding films by irradiating the first and second light-guiding films. The first light-guiding film illuminates the document surface, and the second light-guiding film illuminates the light-receiving surface of the light-receiving element, thus providing a structure without a lens system.

Effect> As described above, in the present invention, by irradiating the first and second light guiding films formed between the original and the light receiving element with the same light source, the irradiated light is directed to the first and second light guiding films, respectively. The light emitted from the end of the first light guiding film illuminates the document surface and is guided to the end of each light guiding film through the transparent film. The emitted light illuminates the light receiving surface of the light receiving element. As described above, by using a single light source as both the light source for irradiating the original and the light source for irradiating the light-receiving element with steady light without using a lens system, it is possible to achieve miniaturization, low cost, high sensitivity, A contact image sensor that can be driven at high speed and is easy to manufacture can be provided.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a contact type image sensor showing an embodiment of the present invention.

In FIG. 1, l is a transparent substrate, 2 is a receiving groove element provided on one side of the transparent substrate, 3 is a light source provided on the other side of the substrate 1, 4 is a document, 5 is a transparent or semi-transparent protective film formed on one surface of the substrate 1 to protect the light receiving element 2; 6 is the above-mentioned protective film formed to prevent the light from the light source 3 from directly irradiating the light receiving element 2; A light shielding film 7 provided at a predetermined position on the other surface of the substrate 1 is located between the original 4 and the light receiving element 2 so as to receive light from the light source 3 and guide the light to the original 4. A first light guide film 8 provided on one side of the protective film 5 is located between the document 4 and the light receiving element 2, and receives light from the light source 3 and directs the light to the light receiving element 2. A second light guide film 9 provided on the other side of the protective film 5 is placed at a predetermined position on the other surface of the substrate l to limit the weight of light guided to the light receiving element 2. A light attenuation filter is provided.

Next, a method for manufacturing the contact type image sensor of the embodiment shown in FIG. 1 will be explained.

First, CdS is deposited on one main surface of the transparent insulating substrate 1.

A light receiving element 2 containing CdSe solid solution as a main component is formed, and then a protective film 5 of the light receiving element 2 is formed. The protective film 5 is made of a transparent or semi-transparent film through which the light from the light source 3 passes. A light shielding film 6 is formed at a predetermined position, and a light attenuation filter film 9 is also formed.

Next, the first light-guiding film 7 and the second light-receiving film 8 are formed at predetermined positions on the surface of the protective film 5 by coating or adhesion.
Finally, a protective film is further formed on this to complete the process.

The first and second light guide films 7 and 8 are made of a resin layer containing a suitable phosphor, and the incident light irradiated from the light source 3 onto the flat side causes the fluorescence in the light guide films 7 and 8 to be emitted. The body lights up randomly in a radial manner, and the light emitted by the phosphor passes through the light guiding films 7 and 8 while satisfying the condition of total reflection.
and 8a, and the light is emitted from the light guiding film ends 7a and 8a. At this time, the shapes of the ends 7a and 8a of the light guide films 7 and 8 are such that the first light guide film 7 directs light toward the document 4 side, and the second light guide film 8 directs light toward the light receiving element 2 side. In order to facilitate irradiation, the ends 7a and 8a of the light guide films 7 and 8 are processed to have end faces with a certain angle.

The first and second light-guiding films 7 and 8 are desirably shaped so that the light emitted from the phosphor contained therein is totally reflected as much as possible. It is desirable that the surface in contact with is flat. Alternatively, a metal film may be attached to this surface to block light and reduce light leakage.

Light absorption spec I- of the phosphor contained in the light guiding film 7.8
/ is on the shorter wavelength side than the emission spectrum. Therefore, in order to cause the phosphor to emit light, it is necessary to use a light source containing components on the shorter wavelength side than the emission spectrum as the light source 3. Normally, the light irradiated onto documents used in facsimiles, etc. often uses a green light source because it is necessary to read the red document information, and in this case, the light emitted from the phosphor is green as well. It is desirable that the light-guiding gonads 7 and 8 contain a phosphor that emits green light, for example, with an emission peak around 530 nm.

In addition, normally, the distance between the light receiving element 2 and the original 4 cannot be read with good resolution unless the distance between the light receiving element 2 and the original 4 is equal to or less than the resolution pitch of the light receiving element 2. A light guide film with a thickness of about 80 μm is formed (300 to 500 #m in the case of 1 film/ff).

In this embodiment, a daylight-colored fluorescent tube is used as the light source 3, and the phosphor contained in the first and second light-guiding films 7 and 8 is a green phosphor as described above. Documents containing commonly used colors such as red can also be read faithfully.

In addition, the effect of improving the light response speed is usually observed when the constant light irradiated to the light receiving element 2 side has an illuminance of 10% to 50% of the reflected light from the original 4, but if the constant light is irradiated with an illuminance higher than that, the opposite effect occurs. Since the deterioration of the contrast ratio becomes large, the second light guiding film 8
In order to limit the light irradiated to the surface, a suitable light attenuating film 9 is placed on a light-transmitting insulating substrate on the opposite side of the light receiving element so that the amount of light emitted from the original is 10 to 50%. 1.

The contact image sensor manufactured in this way does not use an optical lens compared to conventional ones, so it is lower in cost and ultra-small, and does not require optical adjustment. In addition, we used a Cd5-CdSe solid solution for the light-receiving element, which has conventionally been considered difficult to drive at high speed due to its slow optical response speed.
Fine scanning speed is 1 to 2 m5ec/ /ine
This made it possible to read data at high speeds.

<Effects of the Invention> As described above, according to the present invention, by irradiating the first and second light guiding films formed between the light receiving element and the document with the same light source, the irradiated light is transmitted to the respective first and second light guiding films. The light is guided to the edge of each light guide film through the first and second light guide films, and the first light guide film irradiates the document surface, and the second light guide film irradiates the light receiving element. In order to irradiate the light-receiving surface, it is possible to provide a close-contact image sensor in which a single light source can serve as both the light source for irradiating the document and the light source for irradiating steady light to the light-receiving element without using a lens system. It is low cost, ultra-small, does not require optical adjustment, and has an improved optical response speed, allowing high-speed driving, making it possible to easily provide a highly sensitive contact image sensor.

In addition, the light emitted from the end of each light-guiding film is transmitted by radiation from the phosphor and total reflection from the interface.
There is very little unevenness in the amount of light.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a contact type image sensor according to an embodiment of the present invention, FIG. 2 is a sectional view showing the structure of a general conventional contact type image sensor, and FIG. In addition to the structure shown in FIG. 1... Translucent insulating substrate, 2... Light receiving element, 3...
Light source (daylight fluorescent tube), 4... Original, 5... Transparent or translucent protective film, 6... Light shielding film, 7... First light guide film, 8... Second Light guiding film, 9... Light attenuation film, 7a. 8a...Light guide film end surface.

Claims (1)

[Scope of Claims] 1. A first light-guiding film that guides the irradiated light from the light source to the document to be read; and a second light-guiding film that guides the irradiated light from the light source to the light-receiving surface of the reading light-receiving element as constant light. A contact image sensor comprising: a light guiding film, wherein the first and second light guiding films are formed between the document and the light receiving element. 2. The contact image sensor according to claim 1, wherein the first and second light-guiding films are composed of resin films containing a phosphor.