JP2002218160A - Contact image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact image sensor that can realize high reading accuracy, small power consumption, and downsizing by making a maximum luminous quantity part of an emission light from a light source approach closer the main scanning line, i.e., ideally matching the part with the main scanning line. SOLUTION: In the contact image sensor 31 whose the light 34 from a light source 36 is made incident onto an original face P via a light guide 36a, and a distributed refractive-index rod lens array 40 collects the reflected lights to form the image at an image read section 9, the distributed refractive-index rod lens array 40 is placed at a position opposite the light guide 36a and fixed on a plane of the light guide side of a flat plate member 49 made of a rigid material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating light from a light source onto a document surface via a light guide, and condensing the reflected light by a gradient index rod lens array to form an image on an image reading unit. More specifically, the present invention relates to a contact type image sensor to be improved in order to reduce the size of the device, increase the reading accuracy, and reduce the power consumption.

[0002]

2. Description of the Related Art Conventionally, in facsimile machines, copiers, scanners, and the like, a contact type image sensor has been used in a reading section of a document image, and for example, those having a structure as shown in FIGS. ing.

A contact type image sensor 1 shown in FIG.
In the state where the document surface P and the outer surface 2a of the cover glass 2 are in close contact with each other, the light 4 emitted from the light source 6 is incident on the document surface P via the light guide 6a, and the reflected light is distributed in a refractive index distribution type. The light is condensed by the rod lens array 10 and focused on the image reading unit 8. Here, in the gradient index rod lens array 10, a plurality of gradient index rod lenses 11 having the same diameter are arranged in a line along the main scanning line O (perpendicular to the plane of the paper). The whole is sandwiched between a pair of plate-like frames 13a and 13b. The illumination device that irradiates the document surface P is configured by a line illumination device including a light source 6 including a light emitting element such as an LED and a light guide 6a. The illuminating device has a longitudinal direction perpendicular to the paper surface, and the illuminating light illuminates the periphery of the main scanning line O with uniform intensity. The light guide 6a is a rod-shaped transparent body made of glass or plastic. The light emitting element of the light source 6 is in contact with one end or both ends of the light guide 6a. Also,
A light scattering pattern 30 is provided on a surface of the light guide 6a facing the light exit surface, and light incident on the light guide 6a from the light source 6 is scattered and emitted from the light guide 6a. The light scattering pattern 30 is designed such that light is emitted from the light emitting surface of the light guide 6a with uniform intensity in the longitudinal direction (see Japanese Patent Application Laid-Open No. H10-126581).

The line illuminating device is arranged to be inclined at a certain angle with respect to the gradient index rod lens array 10. The external shape is appropriately determined so as to be suitable for the angle. The light 4 emitted from the light guide 6a is reflected on the original surface P toward the gradient index rod lens array 10 side, and the reflected light is incident on each gradient index rod lens 11 of the gradient index rod lens array 10. I do.

In the contact type image sensor 1 described above, the sensor body frame (not shown) integrally supporting the line illumination device and the gradient index rod lens array 10 is moved in the sub-scanning direction (in FIG. Direction) or by moving the document surface P in the sub-scanning direction, the pixels on the document surface P in both the main scanning direction and the sub-scanning direction are detected, and the image reading unit 8 converts the pixel into a two-dimensional image. Process.

The contact type image sensor 21 shown in FIG. 4 has an end face on the side facing the inner surface 2b of the cover glass 2 instead of the light guide 6a in the contact type image sensor 1 shown in FIG. Refractive index distribution type rod lens array 1
Light guide 26 processed into an inclined surface descending toward zero side
The light guide 26a is arranged in parallel with one frame 13b of the gradient index rod lens array 10. The light guide 26a has a characteristic of deflecting the optical axis 24a of the emitted light 24 toward the gradient index rod lens array 10 when the emitted light 24 from the light source 26 is emitted from the inclined surface.

In this contact type image sensor 21 as well, the light 24 emitted from the line illuminating device is made incident on the document surface P, and the reflected light is distributed to the refractive index distribution type rod lens array 1.
The light is condensed at 0 and forms an image on the image reading unit 8. By moving a sensor main body frame (not shown) integrally supporting the line illumination device and the gradient index rod lens array 10 in the sub-scanning direction, or by moving the document surface P in the sub-scanning direction, Pixels on the surface P in both the main scanning direction and the sub-scanning direction are detected, and the image reading unit 8 processes the pixels into a two-dimensional image.

[0008]

By the way, in the gradient index rod lens array 10, the refractive index gradient rod lens 11 is warped or distorted by an external action, and the refractive index gradient rod lenses 11 are positioned relative to each other. If the accuracy or linearity decreases, the reading accuracy decreases. In general, the refractive index distribution type rod lens 11 may be broken when a bending load or the like is applied because the lens diameter is small,
It becomes impossible to read a pixel at a portion shared by the broken refractive index distribution type rod lens 11.

Therefore, in the conventional gradient index rod lens array 10, the frames 13a and 13b for sandwiching the gradient index rod lens 11 are formed with a sufficient thickness to prevent warpage of the gradient index rod lens 11. It prevents distortion and protects against external forces. But frame 1
As the thicknesses of 3a and 13b increase, the refractive index distribution type rod lens 11 and the light guides 6a and 26a separate from each other, and the optical axes 4a and 24a of the outgoing lights 4 and 24 and the main scanning line in FIGS. The distances S1 and S2 from O are widened. as a result,
As shown by the light intensity distribution curves F1 and F2 on the document surface P in each drawing, the maximum light intensity portion is greatly shifted from the main scanning line O, and the light intensity becomes insufficient, thereby lowering the reading accuracy. In order to compensate for the shortage of light quantity, it is necessary to increase the number of light emitting elements used in the line illumination device and to employ light emitting elements having a larger light emission amount, which causes new problems such as an increase in cost and an increase in power consumption. Separation of the frames 13a, 13b from the gradient index rod lens 11 also hinders miniaturization of the entire apparatus.

The present invention has been made in view of such a situation, and makes the maximum light amount portion of the light emitted from the light source closer to the main scanning line, and ideally makes them coincide with each other to improve the reading accuracy. It is an object of the present invention to provide a contact type image sensor that can be reduced in power consumption, and furthermore, can be downsized and realized.

[0011]

In order to achieve the above-mentioned object, the present invention provides a light source, in which light from a light source is incident on a document surface via a light guide, and the reflected light is distributed by a refractive index distribution type rod lens array. In a contact type image sensor for condensing light and forming an image on an image reading unit, the light guide of the flat-plate-shaped member made of a rigid material, wherein the refractive index distribution type rod lens array is located on the opposite side to the light guide. Provided is a contact-type image sensor which is fixed on a body-side plane.

In order to achieve the same object, the present invention also provides a light source for making light from a light source incident on a document surface via a light guide,
In a contact type image sensor in which the reflected light is condensed by a gradient index rod lens array to form an image on an image reading unit, the gradient index rod lens array includes a flat member made of a rigid material and the light guide. Provided is a contact-type image sensor characterized in that the image sensor is sandwiched and supported by a body.

In order to achieve the same object, the present invention further comprises the step of causing light from a light source to enter a document surface via a light guide,
In a contact type image sensor in which the reflected light is condensed by a gradient index rod lens array to form an image on an image reading unit, the gradient index rod lens array is fixed to a side surface of the light guide. Provided is a contact image sensor characterized by the following.

[0014]

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

(First Embodiment) FIG. 1 is a sectional view showing a first embodiment of a contact image sensor according to the present invention. This contact type image sensor 31 is basically the same as the contact type image sensor 1 shown in FIG. 3, and is provided with a light from the line illumination device in a state where the document surface P and the outer surface 2a of the cover glass 2 are in close contact with each other. The emitted light 34 is made incident on the document surface P, and the reflected light is distributed to the gradient index rod lens array 40.
, And is focused on the image reading unit 8.

The line illumination device includes a light source 36 composed of a light emitting element such as an LED and a light guide 36a. The light emitting element of the light source 36 is in contact with one or both ends of the light guide 36a. The light guide 36a is a rod-shaped transparent body, and a light scattering pattern 30 is provided on a surface facing the light exit surface, and scatters light incident on the light guide 36a from the light source 36 to form a uniform light. Emitted with intensity. The line illuminating device is disposed so as to be inclined with respect to the gradient index rod lens array 40 at a certain angle, so that the light 34 emitted from the light guide 36a is distributed on the original surface P by the gradient index rod lens array 40. Side, and the reflected light is distributed to each of the gradient index rod lenses 41 of the gradient index rod lens array 40.
Incident on.

On the other hand, a gradient index rod lens array 4
0 denotes a plurality of gradient index rod lenses 41 having the same diameter.
Are aligned in one or more rows so that the respective optical axes 41a are along the main scanning line O (however, one row in FIG. 1), and the refractive index distribution type rod lenses 41 are fixed with black resin, and Optical axis 4 of gradient index rod lens 41
It is formed by molding so that the outer surface parallel to 1a becomes a plane.

Also in this contact type image sensor 31, the sensor main body frame integrally supporting the line illumination device and the gradient index rod lens array 40 is moved in the sub-scanning direction, or the document surface P is moved in the sub-scanning direction. , Pixels in both the main scanning direction and the sub-scanning direction on the document surface P are detected, and the image reading unit 8 processes the image into a two-dimensional image.

According to the present invention, for example, in the contact type image sensor 1 shown in FIG.
The frames 13a and 13b that sandwich the light guide 36 are removed, and a flat member 49 made of a rigid material is disposed on the opposite side of the light guide 36a, as shown in FIG.
The gradient index rod lens array 40 is fixed to a plane facing the side a.
The feature is that the rigidity is secured. The gradient index rod lens array 40 without a frame is easily bent in the axial direction. However, if the gradient index rod lens array 40 without the frame is fixed to a flat member having appropriate rigidity by bonding with an adhesive or the like, the refractive index gradient rod lenses 41 are linearly aligned. It can be used as a rate distribution type rod lens array 40. Therefore, for example, a flat plate made of blackened polycarbonate is arranged on the side opposite to the light guide 36a, and the gradient index rod lens array 40 is fixed to the flat plate with an adhesive, a double-sided adhesive tape, or the like. The refractive index distribution type rod lens 41 can be held with good linearity.

The shape and dimensions of the flat member 49 are as follows.
There is no particular limitation as long as the bending of the refractive index distribution type rod lens 41 can be corrected and good linearity can be maintained. For example, it may be a single flat plate over the entire width in the longitudinal direction of the gradient index rod lens array 40, or a plurality of strip-shaped plate members may be used along the full width in the longitudinal direction of the gradient index rod lens array 40. At predetermined intervals. The material may be a resin other than the above-mentioned polycarbonate, a metal, or the like. The plate thickness of the flat plate member 49 is appropriately selected depending on the material to be used so that sufficient rigidity can be maintained.

By using the gradient index rod lens array 40 having no frame, the light guide 36a can be closer to the gradient index rod lens array 40, and as shown by the optical axis 34a, from the light source 36. Can be moved to the vicinity of the position of the main scanning line O. As a result, the maximum light amount portion in the light amount distribution F3 of the outgoing light 34 shown in the figure can be made closer or coincident with the main scanning line O, and the above-mentioned problems caused by the light amount shortage can be solved.

In the above description, the refractive index rod lens array 40 having no frame is used. However, in some cases, a frame thinner than usual may be provided on at least one side surface of the refractive index rod lens array 40. When the thickness of the frame is reduced, warpage generally occurs in the refractive index rod lens array 40. This warp can be corrected by fixing the warp to the flat member 49 in the same manner as described above. In a contact-type image sensor such as a general facsimile, a copier, a scanner, or the like, if the thickness is about 0.4 mm or less, mechanical reinforcement can be ensured and a favorable light amount distribution for document irradiation can be obtained. However, even if there is no frame, the mechanical reinforcement of the gradient index rod lens array 40 and the correction of the bending can be performed by the attached plate-shaped member 49, so that the number of members is reduced unless there is no particular reason for requiring the frame. It is desirable not to provide a frame also from the meaning.

Here, a specific configuration example of the contact type image sensor 31 shown in FIG. 1 will be shown, and its effect will be described.

As the gradient index rod lens 41, a lens having a lens diameter of 0.6 mm, an opening angle (θ) of 20 ° and a TC length (L) of 9.1 mm was used. A plurality of the lenses were aligned, and the lenses were fixed with resin. At this time, the optical axis 41
A glass plate is pressed from four directions parallel to a to form a resin into a flat plate shape. The entire width of the gradient index rod lens array 40 was 230 mm. Next, while being held between the glass plates, the gradient index rod lens 41 was cut so as to have a lens length of 4.3 mm, and the cut surface was polished. After this,
The glass plate was removed to obtain a gradient index rod lens array 40 without a frame. Then, one surface of the refractive index distribution type rod lens array 40 was fixed to a blackened polycarbonate flat plate having a thickness of 10 mm using an adhesive. With the addition of the polycarbonate plate, the bending of the gradient index rod lens array 40 could be made substantially zero. Next, 45 degrees are applied to the gradient index rod lens array 40 having the polycarbonate plate attached.
A light guide 36a having a thickness of 2 mm was arranged at a position inclined at an angle to produce a contact image sensor 31. The light amount (P) immediately below the gradient index rod lens array 40
1) was measured. The thickness (t) of the cover glass 2 is 3
mm.

Further, a comparative refractive index distribution type rod lens 41 having the same specifications as described above is used, and the thickness is smaller than the conventional one by 0.3.
A gradient index rod lens array (see FIG. 3 for the configuration) sandwiched between FRP frames having a thickness of 2 mm was prepared.
Next, a light guide 36a having a thickness of 2 mm was arranged at a position inclined by 45 degrees with respect to the refractive index distribution type rod lens array, thereby producing a close contact type image sensor. The light amount (P2) immediately below the gradient index rod lens array was measured.

Further, for comparison, a gradient index rod lens array of the same specification as above using a comparative gradient index rod lens 41 sandwiched by a conventional FRP frame having a plate thickness of 0.95 mm. Was prepared. Next, a light guide 36a having a thickness of 2 mm was arranged at a position inclined by 45 degrees with respect to the refractive index distribution type rod lens array, thereby producing a close contact type image sensor as shown in FIG. And
Similarly, the light amount (P3) immediately below the refractive index distribution type rod lens array was measured.

When the measured values were compared, (P1 / P3)
About 1.8 is obtained, which indicates that the light guide 36a can be approached by the gradient index rod lens array 40, and the light amount is increased. Also,
About 1.7 is obtained as (P2 / P3), which indicates that, when a frame is used, an effect of increasing the amount of light can be obtained by setting the plate thickness to 0.4 mm or less.

(Second Embodiment) FIG. 2 is a sectional view showing a contact image sensor according to a second embodiment of the present invention. The basic configuration of the contact image sensor 51 is the same as that of the contact image sensor 21 shown in FIG.
Graded index rod lens array 40 without frame
With the light guide 56a and the flat member 4 made of a rigid material.
9, for example, sandwiched and supported by a blackened polycarbonate plate. In this contact type image sensor 51 as well, the distance S3 between the main scanning line O and the optical axis 54a of the light 54 emitted from the light source 56 is greatly reduced, and as shown by the light amount distribution curve F4 in FIG. The amount of eccentricity of the maximum light amount portion with respect to O is reduced. Even without a frame, mechanical reinforcement and bending correction of the gradient index rod lens array 40 can be performed by the flat plate member 49 and the light guide 56a.

In the above description, the refractive index rod lens array 40 having no frame is used. However, as in the first embodiment, depending on the case, at least one side surface of the refractive index rod lens array 40 may be thicker than usual. A thin frame may be provided. Again, the frame thickness is about 0.4
mm or less. However, for the same reason as in the first embodiment, if there is no particular need for a frame, it is preferable not to provide a frame from the viewpoint of reducing the number of members.

In order to confirm the effect of increasing the amount of light, the gradient index rod lens array 40 used in the above-described measurement of the amount of light in the first embodiment was used. The board was fixed with an adhesive. In addition, a gradient index rod lens array 4
2, a light guide 56a having a thickness of 2 mm is fixed to the other surface of the light guide 56 with an adhesive, and the contact type image sensor 5 having the configuration shown in FIG.
1 was produced. By inclining the output end face of the light guide 56a with respect to the inner surface 2b of the cover glass 2, the output light 54 can be converted into the gradient index rod lens 41 as shown in FIG.
(The main scanning line O). Then, the light amount (P4) immediately below the gradient index rod lens array 40 was measured.

Further, a comparative refractive index distribution type rod lens 41 having the same specification as the above is used, and the thickness is smaller than the conventional one by 0.3.
A gradient index rod lens array sandwiched between FRP frames having a thickness of 2 mm was fabricated, and a similar contact image sensor was fabricated. Then, the light amount (P5) immediately below the gradient index rod lens array was measured.

Further, for comparison, a gradient index rod lens array sandwiched between a conventional FRP frame having a plate thickness of 0.95 mm using a comparative gradient index rod lens 41 having the same specifications as above. And a contact image sensor as shown in FIG. The light amount (P) just below the gradient index rod lens array
6) was measured.

When the measured values were compared, (P4 / P6)
Is obtained, which indicates that the light guide 56a can be approached by the gradient index rod lens array 40 and the light amount is increased. Also,
(P5 / P6) is about 2.5, which indicates that when a frame is used, an effect of increasing the light amount can be obtained by setting the plate thickness to 0.4 mm or less.

The light guide 56a is usually made of glass and has high rigidity.
9 can be omitted, and the light guide 56a can support the gradient index rod lens array 40. By doing so, the gradient index rod lens array 40
And the light guide 56a can be integrated into a single member, so that the cost can be further reduced by reducing the number of component parts and the number of assembling steps as compared with the case where the components are individually provided. it can.

In the first and second embodiments, the specifications of the gradient index rod lens 41 to be used are not particularly limited, and those used in the conventional contact type image sensor are not limited. It can be appropriately selected according to the application. It is desirable that the aperture angle of the lens be large in terms of the amount of light, but in general, the resolution tends to decrease as the aperture angle increases. Also, it can be said that a smaller lens diameter is desirable for resolution and also desirable for miniaturization of the apparatus. Therefore, it is desirable to compensate for the reduced resolution caused by increasing the aperture angle by using a small-diameter lens. As a specific example, assuming that a refractive index distribution type rod lens 41 having a maximum aperture angle of 15 to 20 °, which is practical in a contact type image sensor such as a facsimile, a copier, and a scanner, is used. Must be 0.7 mm at the maximum, and can be as small as about 0.1 mm in diameter. Although the resolution can be improved as the lens diameter decreases, the brightness decreases as the lens diameter decreases. Therefore, it is necessary to select the aperture angle and the lens diameter within the above range in consideration of the balance between the two.

[0036]

As described above, according to the close-contact type image sensor of the present invention, the frame that holds the gradient index rod lens is removed, so that the maximum light amount portion of the light emitted from the light source is main-scanned. Since the light source is located on the line, the irradiation efficiency of the light source is improved. Therefore, it is possible to prevent a shortage of light amount without depending on an increase in the number of light emitting elements used for the light source or adoption of a light emitting element with a larger light emission amount, and it is possible to realize higher reading accuracy and lower power consumption. In addition, the proximity of the refractive index distribution type rod lens and the light source makes it possible to reduce the size of the device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a first embodiment of a contact image sensor according to the present invention.

FIG. 2 is a sectional view of a main part of a second embodiment of the contact type image sensor according to the present invention.

FIG. 3 is a sectional view of a main part of a conventional contact image sensor.

FIG. 4 is a cross-sectional view of a main part of another conventional contact image sensor.

[Explanation of symbols]

 2 Cover glass 8 Image reading unit 30 Light scattering pattern 31, 51 Contact image sensor 34, 54 Outgoing light 36, 56 Light source 36a, 56a Light guide 40 Refractive index distribution rod lens array 41 Refractive index distribution rod lens 49 Flat plate -Shaped member P Original surface

Claims (5)

[Claims] 1. A contact type image sensor in which light from a light source is incident on a document surface via a light guide, and the reflected light is collected by a refractive index distribution type rod lens array to form an image on an image reading unit. A contact type image sensor, wherein the refractive index distribution type rod lens array is located on a side opposite to the light guide, and is fixed on a plane on the light guide side of a flat member made of a rigid material. 2. A contact image sensor in which light from a light source is made incident on a document surface via a light guide, and the reflected light is condensed by a gradient index rod lens array to form an image on an image reading unit. A contact type image sensor, wherein the refractive index distribution type rod lens array is supported by being sandwiched between a plate member made of a rigid material and the light guide. 3. A contact image sensor in which light from a light source is made incident on a document surface via a light guide, and the reflected light is condensed by a refractive index distribution type rod lens array to form an image on an image reading unit. A contact type image sensor, wherein the gradient index rod lens array is fixed to a side surface of the light guide. 4. The gradient index rod lens array aligns a plurality of gradient index rod lenses in one or more rows, fixes the gradient index rod lenses to each other with black resin, and The contact type image sensor according to any one of claims 1 to 3, wherein the refractive index distribution type rod lens is formed so that an outer surface parallel to an optical axis is a flat surface. 5. The contact type image sensor according to claim 1, wherein the flat member is a blackened polycarbonate plate.