JP3080810B2 - 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 contact type image sensor, and more particularly, to a contact type image sensor in which an original is read by a sensor array including a plurality of photoelectric conversion elements arranged one-dimensionally.

[0002]

2. Description of the Related Art As a conventional contact type image sensor, for example, as shown in FIG. 7, a document supporting member 1 having a light transmitting property, an LED array 2 for illuminating a document, and optical information of the document are converted into a time-series electric signal. And a lens array 4 that forms an original image on the sensor array 3 and a frame 5 that supports these members.

Further, there is a contact type image sensor of a type using two LED arrays as shown in FIG. 8 for the purpose of eliminating a shadow formed around irregularities of a document when reading the document and obtaining a high-quality output image.

[0004]

However, the contact type image sensor shown in FIG. 8 requires two LED arrays, leading to an increase in cost and an increase in the size of the device.

[0005]

According to the present invention, there is provided a light source for emitting light for illuminating a document, a document supporting member for transmitting light from the light source and supporting the document, and a reading line for the document supporting member. An optical sensor that converts optical information of the upper document into an electric signal, and a contact image sensor including the same, at least a part of the document support, which is on the side opposite to the light source arrangement side with respect to the reading line, A reflection surface is provided for reflecting a part of the irradiation light from the light source to guide the light to the reading line, and the optical axis of the illumination light from the light source is between the reading line and the reflection surface or the reflection. It is characterized by being located on a surface.

According to another aspect of the present invention, there is provided a light source that emits light for illuminating a document, a document support member that transmits the light from the light source and supports the document, and an optical system of the document on a reading line of the document support member. An optical sensor for converting information into an electric signal, wherein the light source irradiates at least a part of the document support, which is on the side opposite to the light source arrangement side with respect to the reading line. While providing a reflection surface for reflecting a part of the light to guide the light to the reading line, the light source, the illuminance of the document surface at the reading line position by the light directly irradiated from the light source, the reflection surface The light source has a directional characteristic that is the same as the illuminance of the document surface at the reading line position by the reflected and irradiated light.

[0007]

The present inventors have disclosed a contact image sensor having the same configuration as that of the contact image sensor of FIG. 7 and capable of obtaining the same effect as that of the contact image sensor of FIG. Has proposed a contact type image sensor in which the end surface of the document supporting member 1 as shown in FIG. 6 is used as a reflecting surface and light reflected from the reflecting surface is used for document illumination.

However, as a result of repeated experiments on the contact type image sensor shown in FIG. 6, the present inventor has found that the L type image sensor shown in FIGS.
When the optical axis Y of the illumination light from the ED array is adjusted to the reading position X on the document support member, it has been found that it is difficult to obtain the effect of eliminating shadows when reading a document having irregularities. It is considered that this is because the optical paths A and B in the figure have different optical path lengths, and the light amount ratio of the irradiation light passing through the optical paths A and B does not become 1: 1.

The present invention has been made in view of this point, and reflects at least a part of the irradiation light from the light source on at least a part of the document support, which is on the side opposite to the light source arrangement side with respect to the reading line. When a contact type image sensor as shown in FIG. 6 is provided by providing a reflection surface for guiding to the reading line, the optical axis of illumination light from the light source is between the reading line and the reflection surface. Or by being located on the reflective surface, the illuminance of the document surface at the reading line position by light directly irradiated from the light source,
The illuminance of the document surface at the reading line position by the light reflected from the reflecting surface and irradiated is the same.

Further, according to the present invention, at least a part of the document support, which is on the side opposite to the light source arrangement side with respect to the reading line, reflects a part of the irradiation light from the light source and guides it to the reading line. When a close contact type image sensor as shown in FIG. 6 is configured by providing a reflection surface, the illuminance of the document surface at the reading line position by light directly radiated from the light source using a light source having a gradual directivity characteristic. And the illuminance of the document surface at the reading line position by the light reflected from the reflecting surface and irradiated.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the contact type image sensor according to the present invention, which best illustrates the features of the present invention. Referring to FIG. 1, reference numeral 1 denotes a document supporting member having a light transmitting property; 1a, a reflecting surface of the document supporting member 1; 2, an LED array for illuminating the document; 3, a optical information of the document; A sensor array, 4 is a lens array for forming an original image on the sensor light receiving surface, 6 is a lens for adjusting the position of the optical axis Y of the illumination light from the LED array 2, and 5 is a frame supporting these members. is there.

The light emitted from the LED array 2 is shown in FIG.
The tracing reaches the reading position X by following the optical paths of the middle A and B. In order to minimize the influence of the shadow formed around the irregularities of the original at the reading position X, the illuminance of the original surface due to the direct irradiation light at the reading position X and the illuminance of the original surface due to the light reflected from the reflecting surface are set to 1 : 1.

Now, for ease of understanding, consider a case where light is transmitted as it is without reflection on the reflecting surface. FIG. 2 is a partially enlarged view of FIG. 1 showing the optical paths A and B and a virtual optical path B ′, and FIG. 3 is an illuminance distribution on the document supporting member without a reflection surface. B 'is a virtual optical path when there is no reflective surface (corresponding to an optical path in the case of the contact type image sensor in FIG. 7), X' is a virtual reading position,
It is assumed that the illuminance at the virtual reading position X ′ corresponds to the illuminance at the reading position X due to the light that has reached the optical path B.

As shown in FIG. 6, when the optical axis Y of the illumination light from the LED array 2 is at the reading position X on the document supporting member 1, the illuminance distribution becomes as indicated by a broken line in FIG. The illuminance on X is y ₁ , the illuminance on the virtual reading position X ′ is y ₃ , and y ₁ > y ₃ . That is, the illuminance at the reading position X due to the light reaching the reading position X from the optical path A is different from the illuminance at the reading position X due to the light reaching the reading position X from the optical path B.

In this embodiment, the optical axis Y of the illumination light from the LED array 2 is shifted from the reading position X as shown in FIG.
By arranging the illuminance at the position Z on the reflecting surface, the illuminance distribution on the document supporting member is changed to the distribution indicated by the solid line in FIG.
In this case, the illuminance of the illuminance and the virtual reading position X 'at the reading position X both become y _2. That is, optical path A
Reading position X by light reaching reading position X from
The illuminance on the reading position X is equal to the illuminance on the reading position X by light reaching the reading position X from the optical path B.

As described above, by shifting the maximum value of the illuminance distribution on the document supporting member, the amount of light reaching the document reading position X following the optical path of A and the amount of light reaching the document reading position X following the optical path of B can be reduced. Can be made substantially equal, and the illuminance on the original surface due to the direct irradiation light at the reading position X and the illuminance on the original surface due to the light reflected from the reflection surface are approximately 1:
It becomes 1.

In this embodiment, the lens 6 is used for adjusting the optical axis Y. However, the optical axis Y may be adjusted by changing the mounting angle of the substrate of the LED array and the package shape of the LED chip.

In this embodiment, the optical axis Y is arranged at a position on the reflecting surface (the position Z in the figure). However, the present invention is not limited to such a position, and the directional characteristics of the LED array, the reflectance of the reflecting surface, and the like. Accordingly, the optical axis Y may be arranged at an appropriate position between the reading position X and the reflection surface (a region in the drawing) or on the reflection surface (b region in the drawing).

FIG. 4 is a sectional view of another embodiment of the contact type image sensor of the present invention. In the present embodiment, the LE has a directional characteristic that is gentle so as not to cause an illuminance difference due to a difference in optical path.
This uses a D array. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, considering the optical paths A and B and the virtual optical path B 'similar to FIG. 2, the illuminance distribution is as shown in FIG. 5, and the reading position X, the position Z on the reflecting surface, the virtual The illuminance at the reading position X 'is almost the same. Accordingly, the illuminance on the original surface due to the direct irradiation light on the optical path A at the reading position X and the illuminance on the original surface due to the light reflected from the reflecting surface on the optical path B are approximately 1: 1. In this case, since the illuminance distribution is gentle at the position of the optical axis Y, no setting accuracy is required, the mounting margin of the LED array is increased, and the configuration is easy to assemble.

[0022]

As described above, according to the present invention,
When using a contact type image sensor that utilizes the reflected light from the reflection surface of the document support member together with the direct irradiation light from the light source, the optical axis of the illumination light of the light source is set between the reading line and the reflection surface, or the reflection surface. By arranging them so as to be positioned above, the light amount ratio at the reading line position of the dual optical path can be made approximately 1: 1, thereby maximizing the effect of eliminating shadows around irregularities of the original. Further, the utilization rate of the light from the light source is improved, and the light amount at the reading line position is doubled, so that the load on the light source is reduced. That is, a high-quality contact image sensor having the same performance as the two-LED type shown in FIG. 8 can be realized at a smaller size and at a lower cost, and the power consumption of the light source can be suppressed.
Further, it is possible to provide a contact image sensor capable of responding to higher-speed sensor driving.

The above effect can also be achieved by using a light source such as an LED array having a gradual directional characteristic as the light source. In this case, the mounting margin of the light source is increased and the structure is easy to assemble.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a contact image sensor according to the present invention.

FIG. 2 is a partially enlarged view of FIG. 1 showing optical paths A and B and a virtual optical path B ′.

FIG. 3 is an illuminance distribution on a document supporting member having no reflection surface.

FIG. 4 is a sectional view of another embodiment of the contact type image sensor of the present invention.

FIG. 5 is an illuminance distribution on a document surface when no reflection surface is provided.

FIG. 6 is a cross-sectional view illustrating a contact type image sensor in which an end surface of a document supporting member is a reflection surface.

FIG. 7 is a cross-sectional view illustrating a conventional contact image sensor.

FIG. 8 is a cross-sectional view showing a contact image sensor of a type using two LED arrays.

[Description of Signs] 1 Document support member 2 LED array 3 Sensor array 4 Lens array 5 Frame 6 Lens X Reading position Y Optical axis Z Position on reflecting surface A Optical path B Optical path

Claims (2)

(57) [Claims] 1. A light source for emitting light for illuminating a document, a document support member for transmitting light from the light source and supporting the document, and optical information of the document on a reading line of the document support member is electrically transmitted. A light sensor for converting the light from the light source to at least a part of the document support, which is on the side opposite to the light source arrangement side with respect to the reading line. A reflecting surface for reflecting the portion and leading to the reading line, and an optical axis of illumination light from the light source is located between the reading line and the reflecting surface or on the reflecting surface. A contact type image sensor characterized by the following. 2. A light source which emits light for illuminating a document, a document supporting member which transmits the light from the light source and supports the document, and electrically transmits optical information of the document on a reading line of the document supporting member. A light sensor for converting the light from the light source to at least a part of the document support, which is on the side opposite to the light source arrangement side with respect to the reading line. A reflection surface for reflecting the light and guiding the light to the reading line is provided.The illuminance of the document surface at the reading line position by the light source, which is directly radiated from the light source, reflects the reflection surface. A contact type image sensor, wherein the light source has a directional characteristic that is the same as the illuminance of the original surface at the reading line position by the irradiated light. Over.