JPH0461546A - Image sensor - Google Patents

Abstract

PURPOSE:To make a transparent board small without deteriorating S/N by making one of an end face of the transparent board opposite to a light source and making an end face of the opposite side opposite to an original. CONSTITUTION:A light shield film 2 is provided onto a transparent board 1, a photoelectric conversion element 3 is provided on the film 2, one of an end face of the transparent board 1 is made opposite to a light source and an end face of the opposite side is made opposite to an original 10. The light shield film 2 is formed up to the end face of the side opposite to the original and an illumination light to the photoelectric conversion element and a signal light (reflected light) are completely separated, no stray light exists and high resolution is attained. However, since the stray light is entirely interrupted, the luminous quantity is less. Thus, high sensitive element is used for the photoelectric conversion element 3. The width of the transparent board is made small without deteriorating the S/N.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image sensor, and particularly to a same-size image sensor.

[Prior art]

In the conventional example, as shown in FIG. 1, the light is incident from a light source from the back side of a transparent substrate 1, passes through a lighting window 4 provided in a light-shielding film 2, is reflected by an original lO, and is transmitted as signal light to a photoelectric conversion element. A typical example is a full-contact type 1-magnification sensor of type 3.

In this conventional method, the width of the sensor transparent substrate is 5R11
As described above, when the thickness is 2III11 or less, the effect of the light shielding film is recognized, and a sufficient signal amount for the image has been obtained.

However, due to the demand for smaller devices, the width of the transparent substrate has become smaller.
The trend is for the width to become narrower, such as 2on, Inn, and 0.6on.

In this case, the scattered light (stray light) from the end face of the transparent substrate increases and the dark signal becomes larger, so the bright signal (S) and the dark signal (
N) becomes smaller.

An optical sensor with a substrate width of 3 on and a thickness of 2 m and an S/N of 30 dB has a substrate width of 1111 mm and a thickness of 2 m.
I makes it difficult to secure 18 to 20 dB.

Furthermore, the board area has become smaller due to the narrower width, which limits the space occupied by the optical sensor and the lighting window.

This is becoming difficult due to the physical structure.

Furthermore, since the complete contact type uses the platen roller 11 to feed the document 10, it is necessary to form a wear-resistant plate 9 or a film on the photoelectric conversion element 3.

This involves the use of adhesive 8 and the process becomes longer.

In addition, the wear-resistant plate 9 and the photoelectric conversion element 3. Alternatively, if there is micron-order dust on the quick-acting circuit pattern, the roller pressure may destroy the protective film or cause defects in the cracked pattern of the wear plate.

The increase in the number of steps has resulted in higher costs, lower yields, and lower reliability.

〔the purpose〕

An object of the present invention is to achieve narrowing of the transparent substrate without reducing the S/N ratio. Another object of the present invention is to provide an image sensor having a structure that does not require a conventional wear-resistant plate.

〔composition〕

The present invention provides an image sensor of a type in which a light-shielding film is provided on a transparent substrate, a photoelectric conversion element is provided thereon, one end surface of the transparent substrate faces a light source, and the other end surface faces an original document. The present invention relates to an image sensor characterized in that the light-shielding film is present at least within 500 μm, preferably within 100 μm from the opposite end face.

Further, in the present invention, it is possible to provide an inclination at the end portion on the side facing the document, and to provide the photoelectric conversion element on the inclined surface.

Various specific types of the invention will be described with reference to FIGS. 2-7.

In the case shown in Fig. 2, the light-shielding film 2 is formed up to the end face on the side facing the original, and this completely separates the illumination light to the photoelectric conversion element 3 from the signal light (reflected light), so there is no stray light. High resolution can be achieved. The amount of light is low because it completely blocks out stray light. Therefore, as the photoelectric conversion element 3, one with high sensitivity is used.

These types of image sensors are useful in high performance applications such as scanner facsimiles.

The one in FIG. 3 is also a case in which the light-shielding film 2 is formed up to the end face on the side facing the original, but the end face on the side facing the original is sloped.
A photoelectric conversion element is provided on the inclined surface.

The one shown in FIG. 4 is of a type in which the light-shielding film 2 has a width of 20 to 100 μm in the direction of X from the end surface facing the original.

Since the light-shielding film 2 does not reach the end face in this way, it takes in continuous light, which lowers the resolution but increases the amount of light, making it possible to use a relatively low-sensitivity photoelectric conversion element. It is possible and economical. Such an image sensor is useful as a sensor for electronic whiteboards and the like.

The device shown in FIG. 5 is of the type shown in FIG. 4, with the end face being an inclined surface, and a photoelectric conversion element is provided on the inclined surface, and the above-mentioned X is preferably 20 to 100 μm.

The one in Figure 6 has an optical waveguide 16 on the top layer of the one in Figure 4.
was formed. Reference numeral 17 denotes a transparent electrode made of ITO or the like, which is used in all optical sensors, but is omitted in other figures.

The one in Figure 7 has an optical waveguide I6 on the top layer of the one in Figure 5.
was formed.

Note that the protective film 15 can also serve as an optical waveguide.

As described above with reference to FIGS. 2 to 7, in the present invention, one of the end faces of the transparent base #Fi faces the light source.

This is a new type of image sensor in which the opposite end faces the original, and the structure of its light-shielding film has been devised.

As described above, the transparent substrate is used as a light guide path for irradiating the document with incident light from the light source.

The transparent substrate is made of a transparent material such as quartz, glass, or synthetic resin.

The optical waveguide is made of transparent material.

When using an optical waveguide, signal light can be sufficiently taken in even if X>10 μm, so the S/N ratio is 30 to 40.
dB level can be maintained.

In particular, it is more effective to cover the upper part of the optical waveguide with a light-shielding film (for example, coated with black paint).

What is the relationship between the refractive index of the transparent substrate and the optical waveguide?

Guide waveguide> A transparent substrate is preferable, but to give a specific example, if quartz is used as the transparent substrate, n = 1.43 to 1.45, and if 5iON is used as the optical waveguide, n = 1.55 to 1. ．．
When using 62.5in2, n = 1.46 to 1.5
It becomes 0. Note that if ITO is used as the transparent electrode provided on the light-receiving surface of the photoelectric conversion element, n=1.65 to 1.70.
It is. A laminated structure in which the layers have a higher refractive index toward the inside is preferable.

The angle of inclination is preferably about 45° to 60°.

Although there is no particular restriction on the point at which the tendency of the end surface starts, it is preferable to avoid creating a sloped surface that would form a sharp edge because this is the point where the end surface comes into contact with the original or the roller. There are two types of inclined surfaces: flat surfaces and curved surfaces. The curved surface is concave. The amount of light incident on the sensor increases due to the lens effect on a curved surface than on a flat surface. For a flat surface, it depends only on the amount of shift of light due to the angle of inclination and the refractive index. Regarding the curvature of the curved surface, it is necessary to consider the curvature of the roller and the space between the document surface and the sensor (including an air layer), but it is preferable that the document surface be located near the focal point of the curved surface.

In addition, in FIGS. 2 to 7, if the passivation film 7 and the protective film 15 are made of transparent materials, they both function as light-condensing films.

〔effect〕

(1) The image sensor of the present invention has a structure in which one end face of the transparent substrate faces the light source and the other end face faces the original, so the conventional image sensor shown in Fig. 1 requires a wear-resistant plate. However, such a wear-resistant plate is no longer necessary. Furthermore, since the wear-resistant plate is no longer necessary, manufacturing costs have been reduced accordingly.

Additionally, since there is less wear, the generation of dust associated with it has also been reduced.

(2) In order to optimize the amount of reflected light from the end surface of the transparent substrate, the width of 4
It was possible to make it 0 dB.

(3) In the conventional type, when the width of the transparent substrate is reduced, the lighting window becomes smaller and the S/N ratio decreases, but in the present invention, the amount of lighting can be secured by the thickness of the transparent substrate, so the width of the transparent substrate can be reduced. Narrowing became possible.

(4) By providing the inclined surface, the depth of focus with respect to the pixels can be adjusted freely, so the resolution of the pixels can be increased or decreased. Furthermore, since the pixels are illuminated from the entire inclined surface, a large amount of signal light can be obtained and the S/N ratio can be improved.

(5) By providing the photoelectric conversion element on the inclined surface, the sensor area can be increased to a pixel, and the reflected light from the original can be received more effectively. Furthermore, since the rollers and other parts do not come into contact with the sensor, there is little chance of damage.

(6) By providing an optical waveguide made of inorganic or organic material on the protective film, reflected light from the original could be received more effectively.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional image sensor, and FIGS. 2 to 7 are sectional views showing specific examples of the image sensor of the present invention. l Transparent substrate 2... Electrode and light shielding film 3... Photoelectric conversion element 4... Lighting window 5 - Protective film 6... Upper electrode 7 - Passivation film 8 - Adhesive 9... Transparent wear-resistant plate 10. Document 1 Doplatin roller 12...Support 1
3...Slit J5・Protective film 16・Optical waveguide 17・ITO electrode Figure 2 Figure 3

Claims (1)

[Claims] 1. An image sensor of a type in which a light-shielding film is provided on a transparent substrate and a photoelectric conversion element is provided thereon, one end face of the transparent substrate faces a light source, and the other end face faces a document. An image sensor characterized in that the light-shielding film is present at least within 500 mμ from the end face on the side facing the original. 2. The image sensor according to claim 1, wherein the end portion facing the document is sloped, and the photoelectric conversion element is provided on the sloped surface.