JPH06303381A - Contact type image sensor - Google Patents

Abstract

PURPOSE:To maximize an effect for eliminating shadows generated around the projecting and recessed parts of an original and to improve the availability of light from a light source by providing a reflection surface on a part of an original supporting member and shifting the maximum value of illuminance distribution. CONSTITUTION:When the optical axis Y of illuminating light from an LED array is at a read position X on the original supporting member 1, illuminance on the position X is different from the illuminance on a virtual read position X'. That is, the illuminance by the light reaching from an optical path A to the position X and the illuminance by the light reaching from the optical path B to the position X are different and the latter is smaller. Then, the optical axis Y of the illuminating light from the array 2 is shifted from the position X and arranged at the position Z on the reflection surface. In this case, the illuminance at the position X and the illuminance at the position X' become equal. That is, the illuminance by the light reaching from the optical path A to the position X and the illuminance by the light reaching from the optical path B to the position X become equal.

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 a document is read by a sensor array composed of a plurality of one-dimensionally arranged photoelectric conversion elements.

[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 time-series electrical signals. There is a sensor array 3 for converting the image into an image, a lens array 4 for forming a document image on the sensor array 3, and a frame 5 for supporting these members.

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

[0004]

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

[0005]

SUMMARY OF THE INVENTION According to the present invention, a light source that emits light for illuminating a document, a document supporting member that transmits the light from the light source and supports the document, and a reading line of the document supporting member. In a contact image sensor including an optical sensor for converting optical information of an original document into an electric signal, at least a part of the original document support on the side opposite to the side where the light source is arranged with respect to the reading line, A reflecting surface is provided for reflecting a part of the irradiation light from the light source and guiding it to the reading line, and the optical axis of the illumination light from the light source is between the reading line and the reflecting surface, or the reflection surface. It is characterized in that it is positioned on the surface.

Further, according to the present invention, 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 the reading line of the document support member. In a contact image sensor including an optical sensor for converting information into an electric signal, at least a part of the document support on the side opposite to the side where the light source is arranged with respect to the reading line is irradiated from the light source. A reflecting surface for reflecting a part of the light and guiding the light to the reading line is provided, and the illuminance of the document surface at the reading line position by the light directly radiated from the light source causes the reflecting surface to reflect the reflecting surface. It is characterized in that 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 light reflected and emitted.

[0007]

The present inventors have proposed a contact type image sensor having a structure similar to that of the contact type image sensor of FIG. 7 and having the same effect as that of the contact type image sensor of FIG. 8 in Japanese Patent Application No. 4-318015. Then, a contact type image sensor was proposed in which the end face of the original document supporting member 1 as shown in FIG. 6 was used as a reflecting surface and the light reflected from this reflecting surface was used for original document illumination.

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

The present invention is made from this point of view, and reflects a part of the irradiation light from the light source on at least a part of the document support on the side opposite to the side where the light source is arranged with respect to the reading line. When a contact surface 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 the illumination light from the light source is between the reading line and the reflecting surface, Alternatively, by locating on the reflecting surface, the illuminance of the document surface at the reading line position by the light directly emitted from the light source,
The illuminance of the document surface at the reading line position due to the light emitted by reflecting off the reflecting surface is the same.

Further, according to the present invention, in order to guide a part of the irradiation light from the light source to the reading line by reflecting at least a part of the document support on the side opposite to the side where the light source is arranged with respect to the reading line. When the contact type image sensor as shown in FIG. 6 is configured by providing the reflection surface of FIG. 6, the illuminance of the document surface at the reading line position by the light directly radiated from the light source is used by using the light source having a gentle directional characteristic. The illuminance on the document surface at the reading line position due to the light reflected by the reflecting surface and irradiated is the same.

[0011]

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

FIG. 1 is a sectional view of an embodiment of the contact type image sensor of the present invention, which best shows the features of the present invention. In the figure, 1 is a translucent original document supporting member, 1a is a reflecting surface of the original document supporting member 1, 2 is an LED array for illuminating the original document, and 3 is optical information of the original document converted into time series electric signals. A sensor array, 4 is a lens array for forming an original image on the light receiving surface of the sensor, 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 for supporting these members. is there.

The light emitted from the LED array 2 is shown in FIG.
The optical path of middle A and B is traced to reach the reading position X. In order to minimize the influence of the shadow formed around the unevenness of the original at the reading position X, the illuminance of the original surface by the direct irradiation light at the reading position X and the illuminance of the original surface by the reflected light from the reflecting surface are set to 1 You can set it to: 1.

For ease of understanding, let us consider a case where light is transmitted as it is without being reflected by the reflecting surface. FIG. 2 is a partially enlarged view of FIG. 1 showing the optical paths A and B and the virtual optical path B ′, and FIG. 3 is an illuminance distribution on the document supporting member when it has no reflecting surface. In addition, B'is a virtual optical path when there is no reflective surface (corresponding to the optical path in the case of the contact type image sensor of 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 reaching by 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 the 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 by the light reaching the reading position X from the optical path A and the illuminance at the reading position X by the light reaching the reading position X from the optical path B are different.

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 at the position Z on the reflecting surface, the illuminance distribution on the document supporting member is made to be the distribution of the solid line in FIG.
In this case, the illuminance at the reading position X and the illuminance at the virtual reading position X ′ are both y ₂ . That is, the optical path A
Reading position X due to light reaching from X to reading position X
The illuminance above is equal to the illuminance on the reading position X due to the 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 by following the optical path of A and the amount of light reaching the document reading position X by following the optical path of B. Can be made substantially equal to each other, 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 reflected light from the reflecting surface are approximately 1:
It becomes 1.

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

Further, in the present embodiment, the optical axis Y is arranged at the position on the reflecting surface (the position of Z in the figure), but it is not limited to this position, and the directivity of the LED array, the reflectance of the reflecting surface, etc. Therefore, the optical axis Y may be arranged at an appropriate position between the reading position X and the reflecting surface (area a in the drawing) or on the reflecting surface (area b 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 having a directional characteristic is gentle so that the illuminance difference due to the difference in the optical path does not occur.
It uses a D array. The same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, considering the optical paths A and B and the virtual optical path B ′ similar to those in FIG. 2, the illuminance distribution is as shown in FIG. 5, and the reading position X, the position Z on the reflecting surface, and the virtual position are shown. The illuminance at the reading position X'is almost the same. Therefore, 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 reflected light 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, setting accuracy is not required, the mounting margin of the LED array is increased, and the structure is easy to assemble.

[0022]

As described above, according to the present invention,
When using a contact image sensor that utilizes the reflected light from the reflecting 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 between the reading line and the reflecting surface, or the reflecting surface. By arranging them so that they are positioned above, the light amount ratio at the reading line position of the dual optical path can be made approximately 1: 1, and this maximizes the effect of eliminating the shadows formed around the irregularities of the document. Also, the utilization rate of light from the light source is improved, the light quantity at the reading line position is doubled, and the load on the light source is reduced. That is, a contact image sensor with high image quality and the same performance as the two-LED type as shown in FIG. 8 can be realized at a smaller size and at lower cost, and the power consumption of the light source can be suppressed.
Furthermore, it is possible to provide a contact-type image sensor that can drive the sensor at a higher speed.

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

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a contact image sensor of 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 when it has no reflecting surface.

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

FIG. 5 is an illuminance distribution on a document surface when a reflection surface is not provided.

FIG. 6 is a cross-sectional view showing a contact type image sensor in which an end surface of a document supporting member is used as a reflecting surface.

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

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

[Explanation of symbols]

 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)

[Claims] 1. A light source that emits light for illuminating an original, an original supporting member that transmits the light from the light source and supports the original, and an optical information of the original on a reading line of the original supporting member is electrically supplied. A contact type image sensor including a light sensor for converting into a signal, wherein at least a part of the document support on the side opposite to the side where the light source is arranged with respect to the reading line is provided with an irradiation light from the light source. A reflecting surface for reflecting the portion and guiding it to the reading line is provided, and the optical axis of the illumination light from the light source is located between the reading line and the reflecting surface or on the reflecting surface. A contact image sensor that is characterized by 2. A light source that emits light for illuminating an original, an original supporting member that transmits the light from the light source and supports the original, and an optical information of the original on the reading line of the original supporting member is electrically supplied. A contact type image sensor including a light sensor for converting into a signal, wherein at least a part of the document support on the side opposite to the side where the light source is arranged with respect to the reading line is provided with an irradiation light from the light source. A reflecting surface for reflecting a portion to guide to the reading line is provided, and the illuminance of the document surface at the reading line position by the light directly radiated from the light source reflects the reflecting surface. A contact type image sensor characterized in that it is a light source having a directional characteristic that is equal to the illuminance of the original surface at the reading line position by the emitted light. Over.