JPH0588068U - Image sensor unit - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the signal-to-noise ratio of the signal output in the image sensor and reduce its variation. A reflection member 24 is attached to a housing 22 of a contact image sensor unit, and a part of light emitted from the LED array 18 is guided to a photodiode on the image sensor 12 via a rod lens array 14, By irradiating the photodiode with bias light, the signal output is increased to make it less susceptible to the effects of noise and the variation is reduced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an image sensor unit, and more particularly, to a contact-type image sensor unit used for a facsimile, an image scanner, a digital copying machine, an electronic blackboard and the like.

[0002]

[Prior Art]

 For example, as shown in FIG. 10, a conventional image sensor unit 1 includes an image sensor 2 in which a large number of photoelectric conversion elements such as photodiodes are linearly formed on a substrate such as glass, and a photoelectric conversion element in the image sensor 2. An optical member 3 such as a rod lens array that forms an image on the original, a transparent original table 4 such as glass that supports the original, a light source 5 such as an LED array that illuminates the original, and an image sensor 2 are activated. It is composed of a circuit board 6 to be operated, an image sensor 2, an optical member 3, a transparent manuscript table 4, a light source 5 and a casing 7 for supporting and fixing the circuit board 6.

The image sensor unit 1 is used by being attached to a facsimile or the like, and originals are sequentially conveyed while being pressed to a reading position of the transparent original table 4 by a platen roller or the like. The reflected light from the document illuminated by the light source 5 is photoelectrically converted by the photoelectric conversion element in the image sensor 2 through the optical member 3, and the image on the document is read.

[0004]

[Problems to be solved by the device]

 However, since the image sensor unit 1 is generally operated with a low light amount, the signal output is small, and the image sensor unit 1 is easily affected by noise, variability, offset, etc. generated in the capacitance kick and the circuit board 6. Therefore, there is a problem that the signal output varies widely and the SN ratio is low. In particular, in the case of a diode-pair type image sensor in which a photodiode is used as a photoelectric conversion element and a blocking diode is connected in series in reverse polarity, the forward characteristic of each blocking diode depends on the position where it is formed. Since they are different, there is a problem that there is a large variation in signal output between bits. In addition, this signal output was sometimes accompanied by regular fluctuations such that black read immediately after white became blacker and white read immediately after black became whiter.

In order to solve such a problem, for example, in Japanese Patent Laid-Open Nos. 62-5656 and 2-234563, in addition to the light source 5 for illuminating a document, a photoelectric sensor on the image sensor 2 is provided. A light source for irradiating the conversion element with bias light is provided to increase the signal output. However, the cost was high, and the space for installing the light source for the bias light was required. In addition, it was difficult to always ensure a stable signal output, because the amount of bias light may fluctuate due to deterioration, etc., and the fluctuation may appear in the signal output.

In the case of a photoconductive type image sensor using CdS-CdSe or the like as a photoelectric conversion element, for example, see JP-A-62-36960 and JP-A-62-36968. It is also disclosed that a light guide system or the like is provided on one side to guide a part of light emitted from a light source for illuminating an original to a photoelectric conversion element as bias light. However, the purpose of these is to shorten the response time and enable high-speed reading, which is different from the present invention.

The present inventors have conducted intensive studies to solve these problems and, as a result, arrived at the present invention.

[0008]

[Means for Solving the Problems]

 The gist of the image sensor unit according to the present invention is that a photoelectric conversion element, an optical member that forms an image on a document on the photoelectric conversion element, a transparent document table that supports the document, and the document In an image sensor unit composed of a light source for irradiating and a casing for supporting and fixing these, a reflection member for guiding a part of the light emitted from the light source to the photoelectric conversion element via the optical member. It has been arranged.

Further, in the image sensor unit, the reflecting member is arranged at least at one position among the housing, the transparent document table, and the light source and the transparent document table.

[0010]

[Action]

 According to this image sensor unit, a part of the light emitted from the light source is guided to the photoelectric conversion element via the optical member by the reflecting member without reaching the original document. As a result, the photoelectric conversion element is always irradiated with a constant bias light, and the signal output is increased. Therefore, it is less likely to be affected by noise such as capacitance kick, and variations in signal output are reduced. Further, even if the amount of light emitted from the light source fluctuates due to deterioration of the light source, etc., the ratio of the amount of light applied to the original and the amount of bias light is constant, so a stable signal output can always be secured. it can. The reflecting member may be arranged anywhere such as the housing, the transparent manuscript table, between the light source and the transparent manuscript table, and may be arranged at two or more places.

[0011]

【Example】

 Next, an embodiment of an image sensor unit according to the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 is an embodiment of an image sensor unit according to the present invention. The image sensor unit 10 includes an image sensor 12 having a large number of photodiodes as photoelectric conversion elements, and an optical member such as a rod lens array for forming an image on an original on a photodiode of the image sensor 12. 14, a transparent manuscript table 16 such as glass or hard resin for supporting the manuscript, an LED array for illuminating the manuscript, a light source 18 such as a halogen lamp, a circuit board 20 for operating the image sensor 12, and these image sensors 12 A housing 22 for supporting and fixing the optical member 14, the transparent original stage 16, the light source 18 and the circuit board 20 as an integrated structure, and a part of the light emitted from the light source 18 is contained in the housing 22. A reflecting member 24 for guiding the light to the photodiode on the image sensor 12 through the optical member 14 is attached. It has been.

The greatest feature of this embodiment is that the reflecting member 24 is provided. As the reflecting member 24, a metal plate such as aluminum may be used instead of a plane mirror. The image sensor 12 is formed by forming a large number of photodiodes PD and blocking diodes BD connected in series with opposite polarities in an array on a substrate such as glass as shown in FIG.

The image sensor unit 10 is used by being attached to a facsimile or the like, and a document is sequentially conveyed while being pressed against a reading position of the transparent document table 16 by a platen roller or the like. Light is emitted from the light source 18 to the document, and the reflected light from the document is guided to the photodiode PD on the image sensor 12 via the optical member 14. That is, the image on the original is imaged on the photodiode by the optical member 14. On the other hand, a part of the light emitted from the light source 18 is reflected by the reflecting member 24 and made incident on the optical member 14. As a result, the photodiode PD on the image sensor 12 is irradiated with a constant bias light in addition to the reflected light from the document. Therefore, the signal output is increased, and it is less susceptible to noise such as capacitance kick and noise generated in the circuit board 20, variations, and offsets, and the SN ratio becomes high. Moreover, since the signal output is increased, the variation in the signal output becomes relatively small. Further, even if the forward characteristic of the blocking diode is slightly different depending on the position where the diode is formed, the signal output is sufficiently large, so that the variation in the signal output between bits is relatively small. Further, even if the amount of light emitted changes due to deterioration of the light source 18, etc., the ratio of the amount of light applied to the document and the amount of bias light is constant, so a stable signal output is always secured.

As described above, since the image sensor unit 10 is provided with the reflecting member 24 and the photodiode PD is always irradiated with the constant bias light, the signal output increases and the variation thereof decreases. Therefore, the sensitivity is improved and it is possible to operate at a higher speed. Further, the fluctuation of the bias light amount does not appear in the signal output as in the case where another light source is provided for the bias light. Further, since it is not necessary to secure a special space only by providing the reflecting member 24, it is extremely low in cost and highly practical. In addition, the regular fluctuations contained in the signal output will be reduced.

Although one embodiment of the image sensor unit according to the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, but can be implemented in other modes.

For example, as shown in FIG. 3, the reflecting member 26 may be provided at a position different from that of the above-described embodiment. As is clear from this example, the positions where the reflecting members 24 and 26 are attached are not particularly limited, and may be any positions as long as they can guide a part of the light emitted from the light source 18 to the optical member 14. ..

Further, as shown in FIG. 4, a reflection member 28 is attached to the inner surface of the transparent original table 16, and a part of the light emitted from the light source 18 by the reflection member 28 is transmitted through the optical member 14 to the image sensor. You may make it lead to the photodiode on 12. Further, as shown in FIG. 5, the optical member 30 may be attached to the outer surface of the transparent document table 16 instead of the inner surface thereof.

Further, as the reflecting member arranged in the housing, as shown in FIG. 6, a part 32 of the housing 22 is mirror-finished, and a part of the light emitted from the light source 18 is reflected by the mirror-surface portion 32. May be guided to the photodiode on the image sensor 12 via the optical member 14. As is clear from this example, not only a member different from the housing 22 may be attached to the housing 22 as a reflecting member, but a part or all of the housing 22 may be used as a reflecting member.

Further, as shown in FIG. 7, a reflecting member 34 formed by repeatedly folding a metal plate or the like may be disposed between the light source 18 and the transparent document table 16. In this example, a part of the light emitted from the light source 18 is scattered by the reflecting member 34 and is guided to the photodiode on the image sensor 12 via the optical member 14. Of course, instead of such a scattering reflecting member 34, a flat reflecting member as in the past may be arranged between the light source 18 and the transparent document table 16.

Further, as shown in FIG. 8, a reflecting member 36 such as a half mirror is arranged on the optical path from the light source 18 to the document, and a part of the light emitted from the light source 18 is imaged via the optical member 14. It may be led to a photodiode on the sensor 12.

Further, as shown in FIG. 9, the present invention can be applied to an image sensor unit 44 of a type in which light sources 42 are arranged on both sides of the optical member 40 and a document is irradiated by these two light sources 42. Here, two reflecting members 48 are attached to the transparent document table 46, and a part of the light emitted from each light source 42 by these reflecting members 48 is photoelectrically converted on the image sensor 50 via the optical member 40. I am trying to lead to the element. Further, not only the image sensor unit 44 as described above but also the image sensor unit having one light source described above may be provided with reflecting members at two or more places, and further, both the casing and the transparent manuscript table. You may provide a reflective member in. As described above, the reflecting member may be provided in at least one of the housing, the transparent manuscript table, and the space between the housing and the transparent manuscript table.

Further, a concave mirror may be used as the reflecting member, whereby a part of the light emitted from the light source may be condensed and guided to the photoelectric conversion element via the optical member. Further, the reflectance may be adjusted to an appropriate amount by applying a striped or spotted black paint to the surface of the reflecting member.

In addition, the present invention can be carried out in a mode in which various improvements, modifications and variations are added based on the knowledge of those skilled in the art without departing from the spirit of the invention.

[0025]

[Effect of the device]

 Since the image sensor unit according to the present invention is provided with the reflection member for guiding a part of the light emitted from the light source to the photoelectric conversion element through the optical member, the photoelectric conversion element is always irradiated with a constant bias light. And the signal output is increased. This improves sensitivity, enables faster response, and reduces variations in signal output. Further, it is also possible to deal with an image sensor having a high gradation such as 64 gradations. In particular, even in the case of an image sensor in which a photodiode is used as a photoelectric conversion element and a blocking diode is connected in series to the photoelectric conversion element in reverse polarity, variations in signal output between bits are reduced. In addition, since a part of the light emitted from the light source is guided to the photoelectric conversion element, the ratio of the amount of light applied to the document and the amount of bias light is always constant, and stable signal output must be ensured. You can Moreover, since it is not necessary to secure a special space, it is extremely cost-effective and highly practical. Furthermore, since the regular fluctuation included in the signal output is also reduced, the variation of the γ characteristic is reduced, and the present invention has various excellent effects.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of an image sensor unit according to the present invention.

FIG. 2 is a circuit diagram showing one element of the image sensor shown in FIG.

FIG. 3 is a side view showing another embodiment of the image sensor unit according to the present invention.

FIG. 4 is a side view showing another embodiment of the image sensor unit according to the present invention.

FIG. 5 is a side view showing another embodiment of the image sensor unit according to the present invention.

FIG. 6 is a side view showing still another embodiment of the image sensor unit according to the present invention.

FIG. 7 is a side view showing another embodiment of the image sensor unit according to the present invention.

FIG. 8 is a side view showing another embodiment of the image sensor unit according to the present invention.

FIG. 9 is a side view showing still another embodiment of the image sensor unit according to the present invention.

FIG. 10 is a side view showing an example of a conventional image sensor unit.

[Explanation of symbols]

 Image sensor unit 12, 50; Image sensor 14, 40; Optical member 16, 46; Transparent document table 18, 42; Light source 22; Housing 24, 26, 28, 30, 34, 36, 48; Reflection Member 32; Mirror surface portion (reflection member) PD; Photodiode (photoelectric conversion element)

Claims (2)

[Scope of utility model registration request] 1. A photoelectric conversion element, an optical member for forming an image on a document on the photoelectric conversion element, a transparent platen for supporting the document, a light source for irradiating the document, and a support for fixing them. In an image sensor unit including a housing, a reflection member for guiding a part of light emitted from the light source to the photoelectric conversion element via the optical member is provided. unit. 2. The image sensor according to claim 1, wherein the reflection member is arranged at least at one position among the housing, the transparent document table, and the light source and the transparent document table. unit.