JP2928043B2 - Complete contact image sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perfect contact type image sensor having a length equal to that of a document and performing a reading operation almost completely in contact with the document.

[0002]

2. Description of the Related Art A contact-type image sensor has a length equal to that of a document and has a length of one time.
The optical path length is shorter than that of D (charge coupled device), and the image sensor itself is large, but there is an advantage that the reading device can be downsized. Although there are many configurations of the contact type image sensor, FIG. 6 shows a typical configuration thereof. In FIG. 6, an original 4 is illuminated with illumination light 5 emitted from an LED array 1 and reflected signal light 6 is condensed by a rod lens array 3 on an image sensor substrate 2 having the same size as the original 4. The image of the document is formed on the surface of the sensor element (not shown), and the image is read. Even though it is a close contact type, since a rod lens is used, the distance indicated by A in the figure (usually 10
２０20 mm) is required.

The image sensor substrate 2 usually includes, in addition to the sensor element, a switching element such as a thin film transistor or a diode for switching the element, and a driving circuit or wiring for driving the element. In the description, the description will be made mainly on the sensor element portion which is a characteristic portion of the present invention. In one-dimensional and two-dimensional image sensors, both ends of the sensor element are connected to these switching elements, a power supply, a detection circuit, or the like, respectively. Is called a common electrode because it is common to all elements.
In this specification, the names are unified.

[0004] In recent years, a completely close contact type image sensor has been put to practical use in which the rod lens array 3 is omitted from the configuration shown in FIG. 6 and the cost and size are reduced. There are several types of perfect contact type image sensors, and FIG. 7 shows a perspective view of one example.

FIG. 7 shows a configuration in which a very thin glass of about 50 μm is adhered to an image sensor surface, the glass is brought into close contact with a document, and a hole is formed in a sensor element to introduce illumination light from the hole. . Such an image sensor is disclosed in, for example, JP-A-59-48954 and JP-A-59-81968. In FIG. 7, the illuminating light 5 emitted from the LED array 1 passes through the image sensor substrate 2, the window of the sensor element 7 and the thin film glass 9 having a thickness of about 50 μm and strikes the original 4, and the signal light 6 reflected by the original 4 The sensor element 7 at the nearest position is entered. The image sensor substrate 2 and the thin film glass 9 are bonded to the adhesive layer 8
It is fixed with. The document 4 is in close contact with the substrate 2 by rollers 10 for transporting the document 4 to the image sensor substrate 2. In this example, the height of the entire image sensor is the distance A between the LED array 1 and the document 4, and is reduced to about A = 5 mm compared to A = 10 mm in the case of a rod lens.

Next, FIG. 8 shows a case where a special glass called a fiber array plate is used. The illumination light 5 emitted from the LED array 1 is obliquely incident, passes through a part of the fiber array plate 11, and illuminates the document 4. The light reflected by the original 4 travels through the fiber 12 as signal light 6 by total reflection, enters the sensor element 7 and is read there. Reference numeral 2 denotes an image sensor substrate, 8 denotes an adhesive layer between the image sensor substrate 2 and the fiber array plate 11, and 10 denotes a roller for bringing a document into close contact with the image sensor and transporting the original.

[0007]

First, as shown in FIG.
The problem of a completely contact type image sensor having a structure using thin film glass will be described. An important point in this image sensor is the thin film glass 9. The thickness of the thin film glass 9 has a great influence on the resolution, and it is desirable that the thickness is 50 μm or less in the case of a currently general resolution of about 8 lines / mm.
However, the thickness of 50 μm makes handling of the glass very difficult, which is one of the factors that lower the yield. In addition, there is still an image sensor with a higher resolution of 16 lines / mm, and the facsimile G
This resolution is expected to be generalized with the spread of the four standards. However, it is difficult to further reduce the thickness of the glass in response to this. Thus, this technique has the disadvantage of being limited to low resolution.

[0008] The thinness of the glass also affects the life of the image sensor. As described above, since the distance between the document 4 and the sensor element 7 must be kept at 50 μm or less, so-called floating of the document is not allowed.
For this reason, it is necessary to increase the pressing pressure of the roller 10. If the pressing pressure is increased, the friction naturally increases and the image sensor is easily damaged. Further, in the case of this type of image sensor, a layer of a transparent conductive film is sometimes formed on the thin film glass 9 in order to prevent static electricity, but there is a problem that the layer is peeled off due to the friction.

Another disadvantage of this image sensor is that the width B of the image sensor substrate must be increased. In FIG. 7, in order to bring the original 4 into close contact with the image sensor, the width B of the image sensor substrate needs to be about 5 mm or more in order for the roller 10 to wind the original 4. In general, the cost of the image sensor substrate is proportional to the size of the substrate. In this case, since the longitudinal direction is determined by the size of the document 4, the substrate width B ultimately determines the cost. Since the width required for the image sensor unit is 1 mm or less for a drive circuit integrated type using a polysilicon thin film transistor, the image sensor shown in FIG. 7 wastes four times the cost. turn into.

[0010] Next, the problem of the complete contact type image sensor using the fiber array plate shown in FIG. 8 will be described. Various types of light guides have been proposed in addition to the fiber plate, but each has various problems, and the fiber array plate is the most excellent at present. In this case, as can be seen from FIG. 8, the width B of the image sensor element can be reduced to about 1 mm as described above, and there is no problem of cost.
Further, since the fiber array plate is in principle resistant to lifting of the original, there is no problem as described above. However, there is a problem that the resolution is deteriorated by another factor.

FIG. 9 shows the paths of illumination light and signal light when a fiber array plate is used. FIG. 9 (a)
Is an example using a fiber array plate in which the space between the fibers 12A is formed of transparent glass. A cross-sectional view in the longitudinal direction of the image sensor substrate is shown for ease of explanation, and the illumination light 5 actually enters obliquely from a direction perpendicular to the paper surface. This is reflected on the document 4 to become a signal light 6, which reaches the sensor element 7 by repeating total reflection in the fiber 12 </ b> A. However, those which did not satisfy the condition for total reflection proceed as shown by C, and this becomes leakage light 14 and enters another sensor element, causing a reduction in resolution.

FIG. 9 (b) shows an example in which two types of fiber array plates having a transparent fiber and an opaque fiber are used in order to reduce this effect. Ito et al., Sharp Technical Report, No. 43 No., 1989, December, p. 29-
It is described in detail on page 34. FIG. 9B shows a cross section of the substrate in the sub-scanning direction (narrower substrate width). In the figure, 7 is a sensor element, 8 is an adhesive layer, 12B is a fiber coated with a light absorbing layer, 12A is a fiber having a transparent space between fibers, 13 is a light shielding plate, and 4 is a document. By doing so, it is possible to reduce the influence of the leaked light 14 traveling as indicated by C in FIG. But it is not perfect. In addition, there is a disadvantage that the cost of the fiber array plate increases by adopting the hybrid configuration in the first place, and even if the rod lens array is removed, the cost becomes high.

[0013]

According to the present invention, there is provided a complete contact type image sensor having a light source for emitting illumination light, and at least one or more light guide holes penetrating the front and back sides of the light receiving surface. An image sensor substrate including a sensor element that performs photoelectric conversion according to the intensity of incident light, and a light guiding unit including at least one or more light guides for guiding light incident from one surface to the other surface, arranged in this order in the radial direction of the illumination light from the light source, versus the sensor element
At least one of the cross sections of the respective light guides of the corresponding light guiding means.
Part is covered with the light receiving surface, the illumination light emitted from the light source is incident on one surface of the light guide means through the light guide hole provided in the sensor element, the other of the light guide means The light guide unit is configured to guide the light reflected from the surface of the document to the surface of the document sent to the surface, guide the light reflected from the surface of the document from the other surface of the light guide unit to one surface, and make the light incident on the light receiving surface of the sensor element. It is characterized by having done.

[0014]

Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a basic configuration of a complete contact type image sensor of the present invention. Hereinafter, a description will be given using a conventionally used fiber array plate. However, the light guide is not limited to the fiber, and may be any type as long as at least its cross-sectional area is smaller than the size of the light receiving surface of the sensor element.

Referring to FIG. 1, in the complete contact type image sensor of the present invention, the illumination light 5
Unlike the conventional complete contact type image sensor, illuminates the sensor element 7 on the image sensor substrate 2 without directly entering the fiber array plate 11. As will be described later, the individual sensor elements 7 have a plurality of holes, through which the illumination light 5 enters the fiber 12 and illuminates the original 4. The signal light 6 reflected by the document 4 travels backward in the fiber 12 and enters the sensor element 7 where the signal is read. In FIG. 1, reference numeral 8 denotes an adhesive layer between the image sensor substrate 2 and the fiber array plate 11, and reference numeral 10 denotes a roller.

FIG. 2 is a view showing details of the sensor element 7 and the fiber array plate in the first embodiment of the present invention, and is a perspective view of a part of a one-dimensional sensor array having a resolution of 8 lines / mm. is there. In the figure, 15 is a glass substrate, 16A is an opaque common electrode made of chromium having a thickness of 100 nm, and has a length at least equal to or greater than the read width along the array. It is connected to the. This common electrode 16A
Is opaque because the illumination light 5 from the LED array 1 is not directly applied to the photosensitive layer 17A. Reference numeral 17A denotes an amorphous silicon film having a thickness of 0.5 to 2 μm from the side of the opaque common electrode 16A, and 30 n in which polon is doped to reduce the resistance.
a photosensitive layer in which a p-type amorphous silicon film having a thickness of m
Each layer is formed by a plasma CVD apparatus. Reference numeral 18A denotes a transparent individual electrode made of indium tin oxide, which is separated for each pixel and connected to a reading switch. This image sensor substrate is adhered to a fiber array plate in which fibers 12B covered with a light absorbing layer 19 are bundled in an array via a transparent adhesive layer 8.

The opaque common electrode 16A, the photosensitive layer 17A and the transparent individual electrode 18A are provided with a light guiding hole which is a feature of the present invention. Since the diameter of the fiber 12B was 25 μm, the holes were 4 μm, 6 μm and 6 μm from the opaque common electrode side, respectively. The reason why the hole diameter of the opaque common electrode 16A is small is to prevent light from entering the side surface of the photosensitive layer 17A due to light diffraction as much as possible. Also, this hole has an average of 2 to 3 per fiber.
It is formed with a density that overlaps at the rate of individual pieces. If this ratio is too high, the light receiving area of the essential sensor element is reduced, and the signal amount is reduced. Conversely, if this ratio is too low, the illuminance of the illumination light will decrease, and the signal amount will also decrease. Therefore, this ratio has an appropriate range for the resolution and the fiber diameter.

The illuminating light 5 emitted from the LED array 1 passes through the light guide hole, and the fiber 12B whose side surface is covered with the light absorbing layer 19
And reaches the document 4. The light reflected here becomes the signal light 6, returns in the fiber 12B, and reaches the sensor element. As mentioned earlier, fiber 12B
Is covered with the light absorbing layer 19, and the light entering one fiber 12B does not leak to the other, whether it is illumination light or signal light. Therefore, in the perfect contact type image sensor of the present embodiment, the resolution is not deteriorated unlike the related art even though the fiber array plate is used.

Here, as an example of a conventional complete contact type image sensor, an image sensor using a thin film glass as shown in FIG. Combination with the used fiber array plate does not allow effective reading. This is because the portion of the fiber that is completely contained in the hole cannot be read, while the portion of the photosensitive layer far from the hole cannot be read because light does not enter, and eventually the hole near the hole The signal can be detected only in the portion corresponding to the fiber including both the photosensitive layer and the photosensitive layer. Therefore, the signal amount becomes very small.

In this embodiment, the shape of the light guide hole is not limited to a circular shape. FIG. 3 shows a plan view of the configuration of FIG. FIG. 3A shows a case of a circular light guide hole, and FIG. 3B shows a case of a slit light guide hole. In both figures, 18A is a transparent individual electrode, 20A and 20A.
B indicates a light guide hole, and 12B indicates a fiber. As described above, the object of the present invention can be achieved with any shape of the light guide hole as long as the light guide hole and the light receiving portion of the sensor are simultaneously included in the cross section of the fiber 12B.

FIG. 4 is a sectional view of a second embodiment showing an example in which the present invention is applied to a two-dimensional perfect contact image sensor. In a two-dimensional image sensor, pairs of sensor elements and switching elements are two-dimensionally arranged in a matrix, and FIG. 4 shows a cross section of the sensor element portion. In FIG. 4, 15 is a glass substrate, 18B is 1
An opaque individual electrode made of tungsten having a thickness of 50 nm, which is connected to a switching element (not shown) such as an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor. 17B is an opaque individual electrode 18B
From the side, a p-type amorphous silicon layer doped with boron having a thickness of 100 nm, an amorphous silicon film formed by mixing about 3 ppm of diborane with silane gas during deposition to a thickness of 0.5 to 2 μm, Is a photosensitive layer having a so-called pin structure in which an n-type amorphous silicon film having a thickness of 30 nm and having a reduced resistance is laminated, and each layer is formed by a plasma CVD apparatus. The photosensitive layer 17B is formed in such a manner that the planar pattern is smaller than the planar pattern of the opaque individual electrode 18B and is completely overlaid. 21 is a side wall of the photosensitive layer 17B and the opaque individual electrode layer 1
8B, and is not formed on the light receiving surface of the photosensitive layer 17B. This layer is formed of silicon dioxide, but may be a silicon nitride film. The main role of this layer is to form a transparent common electrode 16 made of indium tin oxide.
B and insulation between the individual electrode 18B and protection of the side surface of the photosensitive layer 17B. The above-described image sensor substrate is bonded to a plate on which the fibers 12B are integrated via the bonding layer 8. Reference numeral 4 denotes an original.

In this example, since the sensor is two-dimensional, the light source (not shown) must be a surface light source, and is a light source similar to a liquid crystal display backlight or the like. The shape, size, density, light path, and the like of the light guide hole are basically the same as those in the first embodiment.

The feature of this embodiment is that the photosensitive layer 17B is completely separated for each sensor element and is formed so as not to protrude above the opaque individual electrode 18B. The photosensitive layer 17 from the opaque individual electrode 18B
By making B smaller, it is possible to prevent the illumination hole from directly entering the photosensitive layer 17B and to prevent the light / dark ratio of the signal from deteriorating. Has the advantage that it can be adopted. In the first embodiment shown in FIG. 2, the opaque common electrode 16A has a sufficient size to prevent the illumination light 5 from directly entering the photosensitive layer 17A. Is limited, it is difficult to adopt the same configuration as in FIG. This embodiment has a structure that solves the problem.

Next, FIG. 5 shows a plan view and a sectional view of a third embodiment of the present invention. This embodiment is an example of a one-dimensional perfect contact type image sensor in which opaque individual electrodes are formed on the substrate side and the photosensitive layer is not separated for each sensor element. 5A and 5B, reference numeral 15 denotes a glass substrate, and reference numeral 18C denotes an opaque individual electrode made of chromium having a thickness of 100 nm. 17C is from the opaque individual electrode 18C side,
FIG. 5 shows a photosensitive layer in which an amorphous silicon film having a thickness of 0.5 to 2 μm and a phosphorus-doped 100 nm-thick silicon carbide film formed using a mixed gas of phosphine, silane, and methane as a raw material are laminated. As shown in (a),
It is patterned in a comb shape. In this state, illumination light enters a portion of the photosensitive layer that protrudes from the opaque individual electrode 18C, and the light / dark ratio of the signal is degraded. This prevents direct illumination light from entering the layer 17C. As described above, the advantage of this structure is that the light-shielding of the photosensitive layer 17C is sufficient, so that the vicinity of the sensor element can be formed compact. Reference numeral 23 denotes an insulating film made of silicon dioxide for insulating the light shielding film 22 and the opaque individual electrode 18C, 16C denotes a transparent common electrode made of indium phosphorus oxide, and 20 denotes a light guide hole. The light-shielding film 22 is connected to a constant potential, and
A capacitance is formed between C and C to serve as an additional capacitance for the sensor element. The light receiving surface is a portion of the photosensitive layer 17C where a large number of light guide holes 20 are arranged in an array.

[0025]

As described above, in the complete contact type image sensor according to the present invention, the illumination light is guided to the fiber through the light guide hole formed in the sensor element, and the light reflected by the original is read. Crosstalk is less than that of a full contact image sensor using a plate. In addition, since there is no need to take a special method such as making the fiber array plate a hybrid structure using the fibers covered with the light absorbing layer, the cost is low.

By overcoming the drawbacks of conventional light guides such as fiber array plates, which have not been used because of problems in terms of crosstalk and cost, which have been said to be suitable for perfect adhesion, According to the present invention, a high-resolution and low-cost complete contact image sensor can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a basic configuration of the present invention.

FIG. 2 is a cross-sectional view of the first embodiment of the present invention.

FIG. 3A is a plan view illustrating an example of a light guide hole according to the first embodiment of the present invention. FIG. 5B is a plan view showing another example of the light guide hole in the first embodiment of the present invention.

FIG. 4 is a sectional view of a second embodiment of the present invention.

FIG. 5 (a) is a plan view of a third embodiment of the present invention. (B) is a sectional view of the third embodiment of the present invention.

FIG. 6 is a perspective view of an example of a conventional contact image sensor.

FIG. 7 is a perspective view of an example of a conventional complete contact type image sensor.

FIG. 8 is a perspective view of another example of the conventional complete contact type image sensor.

9 is a diagram showing diffusion of signal light in the complete contact type image sensor shown in FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LED array 2 Image sensor board 3 Rod lens array 4 Original 5 Illumination light 6 Signal light 7 Sensor element 8 Adhesive layer 9 Thin film glass 10 Roller 11 Fiber array plate 12, 12A, 12B Fiber 13 Shielding plate 14 Leakage light 15 Glass substrate 16A , 16B, 16C Common electrode 17A, 17B, 17C Photosensitive layer 18A, 18B, 18C Individual electrode 19 Light absorbing layer 20, 20A, 20B Light guide hole 21 Protective insulating layer 22 Light shielding film 23 Insulating film

Claims (6)

(57) [Claims] A light source for emitting illumination light; and a sensor element having at least one or more light guide holes penetrating inside and outside the light receiving surface and performing photoelectric conversion according to the intensity of light incident on the light receiving surface. And at least one or more of its side surfaces that guide light incident from one surface to the other surface
And a light guiding means comprising a light guide covered by a light absorbing layer are arranged in this order with respect to the direction of emission of the illumination light from the light source, and the cross section of each light guide of the light guiding means is a light receiving section of the sensor element.
The light guide hole and the receiving hole are smaller than an optical surface and are within the cross section.
At least a part of the light portion, the illumination light emitted by the light source is made incident on one surface of the light guide means through the light guide hole provided in the sensor element, and the other surface of the light guide means is provided. And the light reflected on the surface of the document is guided from the other surface of the light guide means to one surface and is incident on the light receiving surface of the sensor element. A completely-contact type image sensor characterized by the following. 2. A perfect contact type image sensor according to claim 1.
The circular light guide hole provided in the sensor element on the light guide means.
Characterized in that the diameter is smaller than the diameter of the single light guide
Completely contact type image sensor. 3. A completely contact type image sensor according to claim 1.
In service, slit-like provided in the sensor element on the light guiding means
The short side of the light guide hole is smaller than the diameter of the single light guide
A complete contact type image sensor characterized by the following. 4. The perfect contact type image sensor according to claim 1, wherein the sensor element has an opaque common electrode and a photoelectric conversion element in the radiation direction of the illumination light from the light source. And a transparent individual electrode for determining a photosensitive region of the sensor element are stacked in this order. 5. The complete contact type image sensor according to claim 1, wherein the sensor element determines a photosensitive area of the sensor element with respect to the radiation direction of the illumination light from the light source. An opaque individual electrode, a photosensitive layer for performing photoelectric conversion having a planar shape included in the planar shape of the opaque individual electrode, and an opening on the photosensitive layer covering the opaque electrode and the photosensitive layer. A completely-contact image sensor, wherein the insulating film layer and the transparent common electrode are laminated in this order. 6. The complete contact type image sensor according to claim 1, wherein the sensor element includes a light-shielding layer and a light-shielding layer with respect to the radiation direction of the illumination light from the light source. An insulating film layer that covers the light-shielding layer, a part of which overlaps the light-shielding layer via the insulating film layer, and an opaque individual electrode that determines a photosensitive area of the sensor element by a portion that does not overlap the insulating film layer; A photosensitive layer that performs photoelectric conversion of a shape included in the combined shape of the planar shape of the opaque individual electrode and the transparent common electrode, and a transparent common electrode, which is stacked in this order. Contact image sensor.