JPH0795792B2 - Contact image sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a contact type having a size corresponding to 1: 1 with a document width used on a reading side of a facsimile, a hand scanner or the like and reading in close contact with a document. The present invention relates to an image sensor.

2. Description of the Related Art In the conventional contact type image sensor, for example, Japanese Patent Laid-Open No.
As shown in Japanese Patent No. 40856, the structure was as shown in FIG.

That is, in FIG. 4, the light shielding layer 2 having the illumination window 3 is formed on the light transmissive insulating substrate 1, and in order to maintain the insulation between the photoelectric conversion element 5 and the light shielding layer 2, SiO ₂ , Si ₃ N ₄ or the like is used. An insulating layer is formed, and a photoelectric conversion element 5 such as CdS, CdSe or a solid solution thereof is formed on the insulating layer in an island shape, and the photoelectric conversion element 5 is grouped into a certain number of common electrodes 6 and each photoelectric conversion element. 5 is a contact type image sensor in which a counter electrode composed of the individual electrodes 7 corresponding to 5 is provided, and then a transparent protective layer 12 having a high transmittance such as microsheet glass is provided on the counter electrode. The reflected light is reflected by the original 9, and the reflected light 10 is converted into an electric signal by the photoelectric conversion element 5 as information of the original 9.

However, in the contact type image sensor having such a structure, when the photoelectric conversion element 5 is made of a non-accumulation type such as a photoconductor of II-VI group compound, a large amount of photocurrent can be obtained. However, the optical response time is as slow as 10's of msec. For high-speed reading, a structure that sacrifices photocurrent must be used, for example, a storage type. In such a structure, there is a problem that the signal processing circuit becomes complicated because the output signal is very small.

In view of this point, an object of the present invention is to provide a contact type image sensor having a simple structure, a large photocurrent, and capable of reading document information at high speed.

Means for Solving the Problems In order to solve the above problems, the present invention reduces the transmittance of a transparent protective layer. With this configuration, a part of the light incident from the illumination window is applied to the original. Light that becomes reflected light and partly becomes scattered light inside the transparent protective layer is simultaneously incident on the photoelectric conversion element as bias light.

The present invention has the above-described structure and can reduce the effective trap concentration of carriers by the bias light added at the same time as the reflected light from the original, and photoelectric conversion using the photoconductor thin film of II-VI group compound. In the device, the light response time can be easily and significantly shortened.

Embodiment One embodiment of the present invention will be described below with reference to the accompanying drawings.

In the sectional view in the sub-scanning direction of FIG. 1, a light-shielding layer 2 having an illumination window 3 is formed on a transparent insulating substrate 1 such as 7059 glass manufactured by Corning Co., Ltd. by using Si, Cr, Ta, W, Ti, etc. In order to maintain insulation with the photoelectric conversion element 5, the light-transmissive insulating layer 4 made of SiO ₂ , Si ₃ N ₄ or the like is formed of a single layer or a multilayer film. Then, the photoelectric conversion elements 5 arranged in an island shape in the main scanning direction above the light shielding layer 2 are formed of a photoconductive thin film of, for example, CdS, CdSe or a solid solution thereof, and the photoelectric conversion elements 5 are grouped into a common unit. Electrode 6 and individual electrode 7 corresponding to each photoelectric conversion element 5
Is provided with a counter electrode. Further, a transparent protective layer 8 is provided above the photoelectric conversion element 5 for introducing reflected light 10 from the original 9 and for protecting the photoelectric conversion element 5. At this time, the thickness of the transparent protective layer 8 is made thinner than the pitch of the photoelectric conversion elements 5 in order to prevent the deterioration of resolution. When the transmittance of the transparent protective layer 8 is set to 100 as the maximum value of the reflected light 10 from the original 9, the intensity of the scattered light 11 in the transparent protective layer 8 which becomes the bias light of the photoelectric conversion element 5 is photoelectric. 5 to 100 on the surface of the conversion element 5, preferably 10 as shown in the relationship between the relative bias light amount and the light response time as shown in FIG.
Set it to be ~ 100. Thus, the transparent protective layer 8
The amount of bias light on the surface of the photoelectric conversion element 5 can be adjusted by arbitrarily changing the transmittance of the. Here, the transparent protective layer 8
Although the increase of the scattered light 11 in FIG. 9 reduces the illuminance on the surface of the original 9, the effect of the light amount on the light response time is smaller than the bias light amount effect and is not a problem.

As a result, the reflected light 10 from the original 9 is reflected on the surface of the photoelectric conversion element 5.
As shown in Fig. 3, the light response time can be easily and simply set by simultaneously injecting the scattered light 11 which becomes the bias light and the light can be reduced to 1/2 to 1/10 or less and high-speed reading can be performed. It will be possible. Moreover, since the photocurrent does not decrease, the signal processing circuit configuration is easy.

Next, another embodiment of the present invention will be described.

FIG. 2 shows a sectional view in the sub-scanning direction in another embodiment, which is the same as the structure in FIG. 1 except for the transparent protective layers 12 and 13 in FIG. In the present embodiment, as shown in FIG. 2, a multilayer film of a first transparent protective layer 12 and a second transparent protective layer 13 is used, and the refraction of the first transparent protective layer 12 and the second transparent protective layer is made. By changing the refractive index, a transparent material in which the refractive index of the second transparent protective layer 13 is larger than that of the first transparent protective layer 12, such as SiO _2, is used.
By using Al ₂ O ₃ , SiC, TiO ₂ , diamond, etc., the scattered light 11 by the interface between the first transparent protective layer 12 and the second transparent protective layer 13 is used as the bias light. The same effect as the example can be obtained, and the second transparent protective layer 13
By using a material having a high hardness such as Al ₂ O ₃ or SiC, the surface of the transparent protective layer 13 is less likely to be scratched by contact with the original 9, and the durability can be improved.

It is needless to say that the transparent protective layer is not limited to two layers as in this embodiment, and three or more layers can be formed.

EFFECTS OF THE INVENTION According to the present invention, the bias light and the reflected light including the information of the original are reflected on the surface of the photoelectric conversion element with a very simple structure such that the transmittance of the transparent protective layer is reduced and a multilayer film having different refractive indexes is formed. It can be incident at the same time, the light response time can be reduced to 1/2 to 1/10 or less of the conventional one without damaging the photocurrent, the signal processing circuit is easy, and the durability of the transparent protective layer can be improved. That is, it is very excellent in practical use.

[Brief description of drawings]

FIG. 1 is a sectional view in the sub-scanning direction of a contact image sensor according to an embodiment of the present invention. FIG. 2 is a sectional view in the sub-scanning direction of a contact image sensor according to another embodiment of the present invention. Is a characteristic diagram showing the relationship between the amount of bias light and the optical response time,
FIG. 1 is a sectional view of a conventional contact image sensor in the sub scanning direction. 2 ... Shading layer, 3 ... Illumination window, 5 ... Photoelectric conversion element, 8
...... Transparent protective layer with low transmittance, 9 …… Original, 10 …… Reflected light, 11 …… Scattered light, 12 …… Transparent transparent protective layer, 13 …… Transparent protective layer with different refractive index.

Claims (2)

[Claims] 1. A light-shielding layer having an illumination window on a light-transmissive insulating substrate, a light-transmissive insulating layer, a plurality of photoelectric conversion elements arranged in an island shape in the main scanning direction on the light-shielding layer, and the photoelectric converter. A common electrode that is commonly connected for every fixed unit number of conversion elements, a counter electrode that is connected to each of the photoelectric conversion elements, and incident light that enters through the illumination window from the back surface of the translucent insulating substrate. Irradiating the original on the transparent protective layer, when the maximum value of the amount of light reflected from the original is 100, the transparent having a constant transmittance such that the amount of scattered light is 5 to 100 on the photoelectric conversion element surface. A contact image sensor, comprising: a protective layer, wherein the reflected light is signal light, and the scattered light on the transparent protective layer is incident on the photoelectric conversion element as bias light. 2. A transparent protective layer is composed of a multilayer film having a refractive index which is successively increased. Scattered light from the interface of the multilayer films having different refractive indexes is used as bias light, and the maximum value of the amount of reflected light from the original is 100. The amount of scattered light is 5 to 100 on the surface of the photoelectric conversion element at that time.
The contact image sensor according to the item.