JPH10190945A - Close contact image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a close contact image sensor in which degradation of read image quality resulting from the input of noise light to a light receiving element is avoided with a simple configuration and cost is lowered by reducing the number of components. SOLUTION: A close contact image sensor 20 is provided with a casing 21, a glass cover 22 fitted to an upper face of the casing, a board 24 on which a plurality of image sensor chips 25 are mounted, and a light-emitting element 28 to light an original on the glass cover 22 and where a reflected light from an original on the glass cover 22 is focused on the light-receiving element on the image sensor chip 25, and the light-emitting element 28 is mounted on the board 24 on which the image sensor chip 25 is mounted and a surface of the image sensor chip 25 on the board 24 has a low reflection color and the surface of the light-emitting element 28 on the board 24 has a high reflection color.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type image sensor which reads an image of a document conveyed in contact on an image reading surface set on an outer surface of a casing line by line.

[0002]

2. Description of the Related Art A conventional close contact type image sensor 1 of this kind.
9 and 10 show a general configuration example of 0. FIG. A transparent glass cover 1 is provided on the upper surface of the casing 11 having a rectangular cross section.
2, a document reading surface 12a is provided. The document D backed up by the platen 13 is transported in the sub-scanning direction while being in contact with the document reading surface 12a. On the bottom surface of the casing 11, a plurality of image sensor chips 15 mounted on the substrate 14 are arranged. The image sensor chip 15 is, for example, a semiconductor element in which 96 light receiving elements 15a arranged at equal intervals are integrally formed, and is chip-bonded on a substrate 14 on which a predetermined wiring pattern is formed. The terminal pads on the upper surface and the wiring patterns on the substrate are connected by wire bonding 16. For example, in order to achieve a reading density of 200 dots / 1 mm for an A4 width document, 18 image sensor chips are mounted in the reading width direction (the direction orthogonal to the screen of FIG. 9) in the longitudinal direction so as to closely contact each other. Will be.

[0005] Between the read line L set on the original reading surface 12a and the image sensor chip 15 (more specifically, the light receiving elements arranged on the upper surface) arranged as described above, the read line L A rod lens array 17 for focusing an image of the original D along the image sensor chip 15 at the same size as the erect image is arranged.

A plurality of light source elements 18 are mounted on a substrate 19 in a lateral space of the casing 11 with respect to the rod lens array 17 as a light source for illuminating the original D on the reading line L. Is done. Conventionally, a so-called chip-type LED is often used as the light source element.

[0005]

The conventional contact type image sensor 10 having the above configuration has the following problems to be solved.

First, since the substrate 14 for mounting the image sensor chip 15 and the substrate 19 for mounting the chip type LED 18 as a light source are separate members, the number of parts is large and the number of assembly steps is large.

Second, when the substrate 14 on which the image sensor chip 15 is mounted is formed of, for example, a ceramic substrate, since the ceramic substrate usually has a white surface, as shown in FIG. The light reflected on the surface of the substrate 14 is further transmitted to the image sensor chip 15 and the substrate 1.
4 may be reflected on a wire 16 for electrical connection, and this may be input to the light receiving element 15a of the image sensor chip 15 as noise light.
The quality of the read image is degraded.

Third, when the substrate on which the image sensor chip 15 is mounted is formed of a white ceramic substrate, external light transmitted through the ceramic substrate may act as noise light for the image sensor chip 15. This also leads to a reduction in the quality of the read image.

The present invention has been conceived in view of such circumstances, and has a simple structure to prevent the deterioration of the read image quality due to the input of noise light to the light receiving element and to reduce the number of parts. It is an object of the present invention to provide a contact-type image sensor capable of reducing costs and achieving a cost reduction.

[0010]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

That is, the contact-type image sensor according to the present invention illuminates a casing, a glass cover mounted on an upper surface of the casing, a substrate on which a plurality of image sensor chips are mounted, and a document on the glass cover. A contact-type image sensor, comprising: a light-emitting element for performing reflection of light from a document on the glass cover to a light-receiving element on the plurality of image sensor chips. While a plurality of image sensor chips are mounted on the same substrate as the substrate, the peripheral surface of the image sensor chip on the substrate has a low reflection color, and the light emitting element of the substrate has a low reflection color. The surrounding surface is characterized by having a highly reflective color. Here, the high reflection color means a light color such as white, for example, and the low reflection color means a dark color such as black.

In the present invention, since the periphery of the image sensor chip on the substrate on which the image sensor chip is mounted is formed in a low reflection color such as black, a part of the light reflected from the original on the glass cover is Even if it reaches, this light is less likely to be reflected by the substrate,
Therefore, it is possible to avoid as much as possible that the light reflected by the substrate is reflected by the wire connecting the image sensor chip and the substrate and is input to the light receiving element as noise light as in the related art.

Further, according to the present invention, since the light emitting elements are mounted on the same substrate as the substrate on which the image sensor chip is mounted, the number of parts can be reduced and the number of components can be reduced as compared with the conventional structure shown in FIG. The man-hour can be reduced.

Further, in the present invention, since the periphery of the light emitting element mounted on the same substrate as the substrate on which the image sensor chip is mounted is formed in a highly reflective color such as white, the light emitting element When the emitted light reaches the substrate, this light can be further reflected toward the original on the glass cover, so that the illumination efficiency is increased and the light emitting element original can be mounted on the same substrate as the image sensor chip. It is possible to compensate for a decrease in illumination efficiency due to the distance from the camera being increased.

In a preferred embodiment, a white ceramic substrate is used as the substrate, and the high reflection color is formed on the surface of the ceramic substrate and / or on the substrate for mounting the light emitting element. And the low reflection color is formed by a black protective layer applied to the surface of the substrate.

The ceramic substrate can be usually selected as a substrate for mounting electronic components. In view of the circuit configuration, a wiring pattern is naturally formed on such a substrate by, for example, thick film printing using a conductive paste. Therefore, in order to achieve the high reflection color as described above,
This is achieved by selecting the material of the substrate and selecting the conductive paste for forming the wiring pattern, and does not cause any increase in the number of manufacturing steps. In addition, the wiring pattern on the substrate is usually covered with a protective layer formed by printing a thick glass paste. Therefore, in the above embodiment, such a glass paste can be achieved by selecting, for example, a black opaque glass paste, and does not cause any increase in the number of manufacturing steps.

In a preferred embodiment, the light emitting element is formed by a plurality of LED chips arranged at a predetermined pitch on the substrate. That is,
In this embodiment, when mounting the light emitting element on the same substrate as the substrate on which the image sensor chip is mounted,
By adopting the bare LED chip, the light emitting element is mounted on the substrate in the same process as the mounting of the image sensor chip, for example, using the same method or device as the chip bonding of the image sensor chip or the wire bonding. can do. Also,
By employing a bare LED chip as the light source element, the loss is reduced as compared with a so-called chip type LED, and the efficiency of document illumination can be increased accordingly.

In a preferred embodiment, the plurality of LED chips as the light source element are continuously covered with a transparent protective coat, and at least L around the LED chips on the substrate.
The high reflection color is set in a region having a diameter of about ／ of the arrangement pitch of the ED chips.

In order to protect the bare chip or the bonding wire, the bare chip of the LED is covered with a transparent protective layer made of, for example, a silicone polymer. The refractive index of such a protective layer is approximately 1.4. Therefore, of the light emitted from the bare chip of the LED, the light incident on the surface boundary of the protective layer at an angle larger than the so-called critical incident angle is , And totally reflects without going outside the protective layer. Although the light totally reflected in this manner is returned to the substrate surface, in the present invention, since the substrate surface is formed in a high reflection color as described above, the light that has reached the substrate surface is further radiated to the outside. You can do it. According to the experiment, at least approximately three LED chip arrangement pitches are required.
If the surface of the substrate in the area with a diameter of / 5 is set as a highly reflective color,
As described above, it has been found that light totally reflected at the surface boundary surface of the protective layer without escaping to the outside can be radiated to the outside without excess or deficiency.

[0020] In a preferred embodiment, the casing further includes a lens array for focusing an image of the original on the glass cover on the light receiving elements on the plurality of image sensor chips at an equal magnification. And a light guide member for guiding light emitted from the light emitting element to the document on the glass cover.

When a lens array is employed, a certain distance is required between the original reading surface on the glass cover and the image sensor chip as a light receiving element. Therefore, a light emitting element is arranged on the same substrate as the image sensor chip. In this case, the distance from the light emitting element to the document reading surface becomes longer. However, in this embodiment, by using the light guide member, unnecessary diffusion of light emitted from the light emitting element in the casing is suppressed, and the efficiency is improved. Document illumination can be performed well.

In a preferred embodiment, a part or all of the back surface of the substrate is covered with a light shielding layer.

When a white ceramic substrate is used as a substrate on which the image sensor chip is mounted, the ceramic substrate allows some light transmission. In the present embodiment,
Since a part or all of the back surface of such a ceramic substrate, that is, at least a predetermined range corresponding to a portion where the image sensor chip is mounted is covered with the light shielding layer,
Light source and room light in the device incorporating such a contact type image sensor enter the casing through the substrate,
It is possible to prevent noise light from being input to the image sensor chip as much as possible, which also greatly contributes to improvement in image reading quality of the contact type image sensor according to the present invention. The light-shielding layer as described above can be easily achieved by black painting, black printing, attaching a black tape, or the like.

[0024] Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the drawings.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a contact type image sensor 20 according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing components of a contact type image sensor 20 according to a preferred embodiment, FIG. 2 is a plan view, FIG. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, and FIG.
6 is a partial enlarged plan view of the head substrate, FIG. 7 is an enlarged sectional view taken along line VII-VII of FIG. 6,
FIG. 8 is an enlarged sectional view taken along line VIII-VIII in FIG.

The contact type image sensor 20 has a substantially rectangular cross-sectional shape and a casing 21 having a predetermined longitudinal dimension.
The casing 21 can be configured as a molded product using, for example, a black resin. As shown in FIG. 3, the casing 21 has an internal space penetrating vertically and a glass cover 22 is attached so as to close an upper opening. The glass cover 22 functions as a document reading surface 22a,
While being brought into contact with the original reading surface, the platen 2
The document D backed up by 3 is conveyed in the sub-scanning direction. Further, a head substrate 24 described later is attached so as to close a lower opening of the casing 21.

The head substrate 24 is formed using a white ceramic substrate, and a plurality of image sensor chips 25 are arranged close to one side in the width direction on the upper surface of the head substrate 24 in the longitudinal direction. It is mounted on. The image sensor chip 25 is a semiconductor element in which, for example, 96 light receiving elements are arranged integrally at equal intervals, and are chip-bonded on the substrate 24 on which a predetermined wiring pattern is formed. The wire bonding 26 is performed between the terminal pad on the upper surface and the wiring pattern on the substrate. A plurality of LED bare chips 28 as illumination light sources are mounted at predetermined intervals near the other side in the width direction. Also in this case, the bare chip is chip-bonded 29 on a substrate on which a predetermined wiring pattern has been formed, and the upper surface terminal pads and the wiring pattern are connected by wire bonding 29.

The interior space of the casing 21 efficiently transmits the light from the LED to the glass cover 2.
Light guide member 30 made of transparent resin for irradiating the original on 2
And a rod lens array 27 for focusing the image of the original D along the reading line L set on the glass cover 22 on the image sensor chip 25 at an erect equal magnification. .

The rod lens array 27 is held so as to be inserted from above into a groove-like holder 31 formed in the casing 21. The groove-shaped holder portion 31 has a concave groove 31 corresponding to the planar form of the rod lens array 27.
a, and the bottom thereof has a rod lens array 2
A slit 32 is formed to allow the light transmitted through 7 to pass therethrough and reach a plurality of image sensor chips 25 disposed below the light.

The light guide member 30 emits from the LED bare chip 28 mounted on the head substrate 24 at a position displaced laterally from the read line L set on the extension of the optical axis of the rod lens array 27. This is a member for efficiently guiding light to the reading line L or a region near the reading line L by the prism effect. The light guide member 30 includes a bottom wall 34 having a through-hole window 33 opened corresponding to the arrangement of the LED bare chip 28, an inner wall 21 a on one side of the casing 21, and the groove-shaped holder 3.
It is attached so as to fit into the space surrounded by the first outer wall 31b.

As shown in FIGS. 1, 2 and 5, both ends of the light guide member 30 are provided between the inner wall 21a on one side of the casing and the outer wall 31b of the grooved holder 31. A fitting block 30a having predetermined vertical dimensions that can be fitted is integrally formed.
A pressing piece 30b for pressing the upper surfaces of both ends of the rod lens array 27 is formed integrally with the rod piece 27a.

On the head substrate 24, a wiring pattern 35 for mounting a plurality of image sensor chips 25 and an LED bare chip 28 as a light source are provided.
The wiring pattern 36 for mounting is formed. In the present embodiment, these wiring patterns 35, 36
Is formed by a thick film printing method using a silver / platinum paste. The surface of the wiring pattern thus formed has a white color. As a result, coupled with the fact that the head substrate is a white ceramic substrate and that the wiring pattern printed thereon has a white color,
The color of the upper surface of the head substrate 24 at the stage when the wiring patterns 35 and 36 are formed as described above is white.

In the head substrate 24, in the step after the wiring patterns 12, 35, and 36 are formed as described above, a part of the wiring pattern to be subjected to wire bonding or a part to be exposed as a terminal is left. Then, the glass paste is covered with a protective layer formed by thick-film printing. In the above-described embodiment, particularly, in a predetermined region where the image sensor chip 25 is to be mounted, as shown in FIG. Is used as the protective layer 37. As a result, of the surface of the head substrate 24, the surface of the region where the image sensor chip 25 is to be mounted has a black color. On the other hand, the surface of the area where the LED bare chip 28 as the light source is to be mounted has a white color as described above. In addition,
As the black glass paste, for example, a glass paste containing iron oxide powder is used.

A plurality of image sensor chips 25 and a plurality of LED bare chips 28 are bonded to predetermined portions of the head substrate 24 formed as described above by a chip bonder, and the upper surface pads of each chip are bonded by a wire bonder. And the wiring pattern are connected by a thin metal wire such as a gold wire. Then, in order to protect each chip and bonding wire, a protective coating 38 made of, for example, a transparent silicone polymer is used.
Is made. As shown in FIG. 8, a light-shielding layer 39 made of black paint or the like is formed on the back surface of the head substrate in the present embodiment.

The contact type image sensor 20 having the above configuration is
It can be assembled as follows. First, the rod lens array 27 is attached to the groove-shaped holder 31 of the casing 21.
Is inserted from above. Next, the light guide member 30 is fitted into a space surrounded by the casing inner wall 21a and the holder outer wall 31b from above. The light guide member 30 is held at a fixed position by fitting the fitting blocks 30a formed at both ends thereof into the space. And
The pressing pieces 30b formed on the fitting blocks 30a at both ends of the light guide member 30 press the upper surfaces of both ends of the rod lens array 27. Thereby, the rod lens array 27
Are stably and reliably held in place.

The glass cover 22 is fixed by, for example, bonding so as to be fitted into an opening on the upper surface of the casing 21. The head substrate 24 is fitted into the lower surface opening of the casing 21 so that the stopper 4
Fixed by 0. As shown in FIGS. 1 and 4, the stopper 40 is formed by bending a spring plate member into a substantially M-shaped cross section, and an engaging hole 40 b formed in a leg portion 40 a thereof has a casing 40. 21 engages with engagement projections 41 formed on both side surfaces. In the contact type image sensor 20 having the above-described configuration, since the image sensor chip 25 as the light receiving element and the LED bare chip 28 as the illumination light source are mounted on the same ceramic substrate 24, the number of parts is small. As described above, assembly is easy.

Next, the operation of the contact type image sensor 20 having the above configuration will be described.

The light emitted from the LED bare chip 28, which is an illumination light source, is radiated toward a narrow area along the reading line L on the glass cover 22 by the prism effect of the light guide member 30, and the original on the glass cover 22 Illuminate D efficiently.

As shown in detail in FIG. 7, each of the LED bare chips 28 is continuously covered with a protective layer 38 made of a transparent silicone polymer. This protective layer 38
Has a refractive index of about 1.4, of the light that spreads radially from the LED bare chip 28,
Light incident at an angle smaller than the critical incident angle at the boundary surface is radiated as it is to the outside of the protective layer 38, but light incident at an angle larger than the critical incident angle is
8, the light is totally reflected at the boundary surface without returning to the outside of the protective layer 38. By the way, in the above configuration, the surface of the head substrate in the vicinity of the LED bare chip 28 has a high-reflection color of white as described above, so that the protective layer 38 is totally reflected at the boundary surface as described above.
Most of the light that has returned to the inside and reached the surface of the head substrate 24 is irregularly reflected without being absorbed by the substrate surface, and again passes through the boundary surface of the protective layer and is emitted to the outside. According to experiments, it has been found that the light reflected on the surface of the white substrate within a range of a diameter of 3/5 of the arrangement pitch P of the LED centering on the LED bare chip 28 contributes to an increase in illumination light amount. Therefore, in order to enjoy the advantages of the present invention, it is preferable that the surface of the substrate in the range of at least 3/5 of the arrangement pitch P around the LED bare chips 28 be a high reflection color such as white. It can be said that it is necessary.

The image of the document D illuminated as described above along the reading line L is focused by the rod lens array 27 on the light receiving elements 25a on the plurality of image sensor chips 25 at an equal magnification. Each image sensor chip 25 reads out the image data on the line by serially outputting the outputs from all the light emitting elements. At this time, the reflected light from the original at the position deviating from the reading line L is also allowed to reach the surface of the substrate 24 via the rod lens array 27. In the above embodiment, the image sensor on the surface of the substrate 24 Since the periphery of the mounting portion of the chip 25 has a low reflection color of black, the light reaching the substrate surface as described above is absorbed by the substrate 24 without being reflected. Therefore, as pointed out as a conventional problem with reference to FIG. 9, the reflected light from the surface of the substrate is reflected by the bonding wire and is input to the image sensor chip as noise light, which deteriorates the read image quality. It can be avoided effectively.

In the embodiment, since the back surface of the ceramic substrate 24 is covered with the light-shielding layer 39, the light source and the room light in the device in which the contact type image sensor 20 is incorporated are passed through the substrate and into the casing. Break in,
It is possible to prevent noise light from being input to the image sensor chip 25 as much as possible, which also greatly contributes to the improvement of image reading quality of the contact type image sensor according to the present invention.

Of course, the scope of the present invention is not limited to the above embodiment. A method for setting a predetermined area of the head substrate to a low reflection color or a method for setting a light reflection color is not limited. The low reflection color does not necessarily have to be black, and the high reflection color does not necessarily have to be white.

In the embodiment, the light guide member for efficiently guiding the light emitted from the light source to the original on the glass cover is used. However, whether to provide such a light guide member is a matter of choice. Also, the form of the light guide member is not limited to the embodiment.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing components of a contact image sensor according to a preferred embodiment of the present invention.

FIG. 2 is a plan view of the contact type image sensor shown in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV in FIG. 2;

FIG. 5 is a sectional view taken along the line VV in FIG. 2;

FIG. 6 is a partially enlarged plan view of a head substrate according to the present invention.

FIG. 7 is an enlarged sectional view taken along line VII-VII of FIG. 6;

8 is an enlarged sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a cross-sectional view showing a general configuration of a conventional contact image sensor.

FIG. 10 is an explanatory diagram of a problem of the conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 20 contact image sensor 21 casing 22 glass cover 24 head substrate 25 image sensor chip 27 rod lens array 28 bare chip LED (light emitting element) 30 light guide member 39 light shielding layer

Claims (6)

[Claims] A casing, a glass cover mounted on an upper surface of the casing, a substrate on which a plurality of image sensor chips are mounted, and a light emitting element for illuminating a document on the glass cover; A contact image sensor configured to focus reflected light from a document on the glass cover to light receiving elements on the plurality of image sensor chips, wherein the light emitting element is a substrate on which the plurality of image sensor chips are mounted. The peripheral surface of the image sensor chip on the substrate has a low reflection color, and the peripheral surface of the light emitting element on the substrate has a high reflection color. A contact type image sensor. 2. A white ceramic substrate is used as the substrate, and the high reflection color is formed on a surface of the ceramic substrate and / or silver / silver formed on the substrate to mount the light emitting element. The contact type image sensor according to claim 1, wherein the contact type image sensor is formed by a wiring pattern of a platinum paste, and the low reflection color is formed by a black protective layer applied to a surface of the substrate. 3. The contact type image sensor according to claim 1, wherein the light emitting element is formed by a plurality of LED chips arranged at a predetermined pitch on the substrate. 4. The plurality of LED chips are continuously covered with a transparent protective coat, and at least about ／ of the arrangement pitch of the LED chips around the LED chips on the substrate. The contact type image sensor according to claim 3, wherein a high reflection color is set in a region having a diameter of?. 5. A lens array for focusing an image of a document on the glass cover on light receiving elements on the plurality of image sensor chips at an equal magnification in the casing, and light emitted by the light emitting elements. And a light guide member for guiding the light to a document on the glass cover.
A contact type image sensor according to claim 4. 6. The contact type image sensor according to claim 2, wherein a part or all of the back surface of the substrate is covered with a light shielding layer.