JP4123266B2 - Image sensor - Google Patents

Description

  The present invention relates to an image sensor, and in particular, reads an object to be irradiated having a light transmission portion such as a bill.

  Conventionally, as this type of image sensor, for example, there is one described in JP-A-6-273602 (Patent Document 1). In this Patent Document 1, as described in FIGS. 1 and 2, the light emitted from the light emitting diode 1 passes through the illumination window 41 on the transparent protective plate 4 and is applied to the document 6. A so-called reflective image sensor is described in which the light reflected by the document 6 is converged by the microlens array 42 on the transparent protective plate 4 and the document is read by the light receiving sensor chip 2. In this reflection type image sensor, the microlens array 42 is configured such that the number of microlenses matches the number of elements in the light receiving sensor array, and the lens elements and the light receiving elements are in one-to-one correspondence.

  On the other hand, as disclosed in Japanese Patent Laid-Open No. 2003-87564 (Patent Document 2), as shown in FIG. 2, a light source 22 for reflective originals or a light source 80 for transparent originals is used. An image reading apparatus configured to be accommodated in the document cover 60 and detachably locked to the document cover 60 is attached to the document cover 60 when reading a reflective document and is removed from the document cover 60 when reading a transparent document. Is described.

JP-A-6-273602 (FIGS. 1 and 2)

JP 2003-87564 A (paragraph 0024, FIG. 2)

  However, what is described in Patent Document 1 is a so-called reflection type image sensor, in which the number of microlenses is made to match the number of elements of the light receiving sensor array, and the lens elements and the light receiving elements are made to correspond one-to-one. Since they must be configured, there is a problem that their alignment becomes difficult.

  On the other hand, what is described in Patent Document 2 is an image sensor that combines a so-called transmissive type and a reflective type. When reading a reflective original, the original mat is attached to the original cover, and when reading a transparent original, the original mat is attached. Since it takes time and effort to remove it from the document cover, there is a problem that switching between the so-called reflection type and the transmission type is troublesome.

  Therefore, according to the present invention, in a so-called transmissive image sensor, a refracting member in which a large number of protrusions are continuously formed along the main scanning direction is provided between the light source and the original (object to be irradiated). A new image that enables reading of a highly accurate document (illuminated object) with reduced illuminance deviation over the main scanning direction of the document (illuminated object) by the light from the light source passing through and being refracted through A sensor is provided.

  The image sensor according to claim 1 converges the light transmitted through the irradiated object with respect to the irradiated light source arranged in the main scanning direction and the irradiated object conveyed in the sub-scanning direction orthogonal to the main scanning direction. A lens array extending in the main scanning direction; a sensor arranged in the main scanning direction for detecting light converged by the lens array; and disposed between the light source and the object to be irradiated. A first light guide that repeatedly reflects light inside and guides the light toward the irradiated object, and a light guide provided on the light emission side of the first light guide, and a plurality of light guides along the main scanning direction. And a refracting section that irradiates light in the main scanning direction of the irradiated object by allowing light from the light source to pass through and refract.

  According to a second aspect of the present invention, there is provided an image sensor in which the first light source arranged in the main scanning direction and the first light from the first light source are conveyed in the sub-scanning direction orthogonal to the main scanning direction. A first light guide that guides light to an object, and a light emitting side of the first light guide, and a plurality of protrusions are continuously formed along the main scanning direction. A refracting unit that transmits light from the light source in the main scanning direction and refracts it to irradiate light in the main scanning direction of the irradiation object; a second light source arranged in the main scanning direction; and the second light source. A second light guide for guiding light from the second light source side to the irradiated object side so as to irradiate the irradiated object with the first light, the first light transmitted through the irradiated object, and the irradiated object A lens array that converges the second light reflected from the object, and photoelectrically converts the first light and the second light converged by the lens array A sensor, a first substrate provided with the sensor, a second substrate provided on the side opposite to the lens array side with respect to the first substrate, and provided with the second light source; An electrical signal that is interposed between the surface of the first substrate opposite to the surface on which the sensor is provided and the surface of the second substrate that faces the surface is photoelectrically converted by the sensor from the first substrate. And a connector for transmitting to the second substrate.

An image sensor according to a third aspect is the one according to the first or second aspect, wherein a cross-sectional shape of the first light guide in a sub-scanning direction is a trumpet shape.
An image sensor according to a fourth aspect is the image sensor according to the first or second aspect, wherein the first light guide and the refracting portion are integrally formed of a resin material.
The image sensor according to a fifth aspect is the one according to the first or second aspect, wherein a cross-sectional shape of the protrusion of the refracting portion in the main scanning direction is a semicircular shape or a semielliptical shape.
The image sensor according to a sixth aspect is the one according to the first or second aspect, wherein a cross-sectional shape of the protrusion of the refracting portion in the main scanning direction is a triangular shape.

  According to the first to sixth aspects of the invention, the illuminance deviation in the main scanning direction on the document (object to be irradiated) can be reduced, and the document reading accuracy can be improved.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional configuration diagram of an image sensor according to the first embodiment. In FIG. 1, reference numeral 1 denotes a manuscript (irradiated object), a reading medium such as banknotes, securities or checks, and 2 a transmissive light source provided outside a contact image sensor (hereinafter also referred to as CIS). is there. 3 is a first light source in which LED chips are linearly arranged in an array in the main scanning direction, 4 is a trumpet light guide that guides illumination light emitted from the first light source 3 to the CIS side, and 4a is a trumpet type. The light emitting part (ejecting part) 5 of the light guide 4 is a refraction sheet attached to the light emitting part 4a, and the light emitting part 4a and the refraction sheet 5 constitute a refraction member. 6 is a glass plate that transmits light emitted from the refractive sheet 5 to the CIS side, 7 is an LED substrate on which the LED chip of the first light source 3 is mounted, 8 is a connector for driving the light source 3, and 9 is a trumpet type. This is a transmissive light source housing that houses or holds the light guide 4, the glass plate 6, and the LED substrate.

  Next, the configuration on the CIS side will be described. In FIG. 1, 10 is a second light source in which LED chips are linearly arranged in an array, 11 is a refractive light guide that guides illumination light emitted from the second light source 10 to the document 1, and 11a is a refractive type. The light emitting part (ejecting part) of the light guide 11, 12 is a glass plate that transmits the light emitted from the light emitting part 11 a to the document surface, and 13 is the transmitted light from the first light source 3 or the second light source. A rod lens array (lens array) for converging the reflected light reflected from the original surface by the light from 10, and a light receiving unit 14 for receiving the light converged by the rod lens array, a plurality of photoelectric conversion units and their driving This is a sensor IC in which a circuit or the like is incorporated. Reference numeral 15 denotes a sensor board on which a plurality of sensor ICs 14 are mounted. Reference numeral 16 denotes a board made of a printed wiring board on which the second light source 10 is mounted on both sides. In this way, the image sensor as a whole is constituted by the transmissive light source 2, the CIS side, and the like.

  That is, basically, a transmissive image sensor is constituted by the transmissive light source 2, the trumpet light guide 4, the refraction sheet 5, the rod lens array 13, and the light receiving unit 14, while the second light source 10, the refraction type The light guide 11, the rod lens array 13, and the light receiver 14 constitute a reflective image sensor.

  17, after the analog signal photoelectrically converted by the light receiving unit 14 is A / D converted, a correction circuit for shading correction or all bit correction of the signal output of each pixel (bit) is incorporated, and image information from the document 1 is incorporated. A signal processing IC (ASIC) 18 which outputs as an image signal supplies power to an input signal such as a start signal (SI), a clock signal (CLK) and a power source for driving the CIS, and a transmissive light source, and the image signal is externally supplied. 19 is a relay connector that transfers signals between the sensor substrate 15 and the substrate 16, 20 is an internal housing that houses or holds the rod lens array 13 and the sensor substrate 15, and 21 is a refractive light guide 11. This is an external housing that houses or holds the glass plate 12 and the substrate 16. The internal housing 20 is held by the relay connector 19, and the transmissive light source 2 and the external housing 21 are fixed to the main body of a reading system (not shown) such as a financial terminal device. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 2 is a partial cross-sectional view of the LED chips linearly arranged on the LED substrate 7. In the first embodiment, the first light sources 3 are arranged at intervals of 10 mm in the main scanning direction (document reading direction). The second light source 10 composed of LED chips linearly arranged on both sides of the substrate 16 has the same arrangement.

  Next, the operation will be described. When the second light source 10 mounted inside the CIS is used to receive the reflected light from the document 1 and use it as image information, the second light source 10 is turned on, and the bent type has a relatively long optical path length. The original 1 is irradiated with light through the light guide 11. Since the illumination light from the second light source 10 is radiated obliquely with respect to the document 1, the scattered light reflected on the document surface is collected as reflected light by the rod lens array 13, and is photoelectrically converted by the sensor IC 14. The

  When the first light source 3 of the transmissive light source 2 installed outside the CIS side of the image sensor is used to receive the transmitted light from the document 1 and use it as image information, the first light source 3 is turned on. Then, the original 1 is irradiated with light through a trumpet light guide 4 having a relatively short optical path length. Since the illumination light from the first light source 3 is radiated in a direction perpendicular to the document 1, the direct light transmitted through the document surface is collected by the rod lens array 13 and photoelectrically converted by the sensor IC 14.

  In FIG. 2, the pitch interval of the LED chips in the main scanning direction is 10 mm, and the illumination light is diffused by the trumpet light guide 4 so that the illuminance distribution in the main scanning direction on the original surface of the transmissive light source 2 is uniform. It is considered to be.

  However, when adjusting the amount of transmitted light or the like, that is, when detecting the illuminance from the transmissive light source 2 in the absence of the document 1 and using it as a reference signal (reference signal) for shading correction, etc. It is preferable that the illuminance of each pixel in the light receiving unit 14 in the scanning direction is uniform. If the reference signal is greatly different in illuminance for each pixel, it will hinder the collection of accurate image information data of the document 1. This is because the light emitting part 4a of the trumpet type light guide 4 has a flat shape, and when there is no original, the light beam passing through the position corresponding to the original surface has a different angular distribution depending on the position, and the illuminance difference between the pitches of the LED chips is different. This is because a ripple appears in the output of each pixel after photoelectric conversion.

  Next, the function of the image sensor of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of a CIS drive circuit. The analog output (SO) photoelectrically converted by the light receiving unit 14 is obtained at the timing of the start signal (SI) synchronized with the CIS clock signal (CLK). After amplification, the signal processing IC 17 performs analog-to-digital (A / D) conversion, and the correction circuit performs shading correction including sample and hold, all-bit correction, and the like. To correct the digital signal data obtained from the SO, a preset reference signal (reference signal) data is read from the RAM area, and is processed by the image information collected from the document 1 and the correction circuit of the signal processing IC 17. . When the transmissive light source 2 is used, the first light source 3 is turned on, and the second light source 10 housed in the CIS is turned off, so that the illuminance in the absence of the document 1 is photoelectrically detected by the light receiving unit 14. It is converted into a reference signal and applied to light amount adjustment and correction data.

  FIG. 4 is an external view of the trumpet type light guide 4 in a state where the refractive sheet 5 is attached to the entire surface of the light emitting portion 4a with a transparent adhesive. Each of the refractive sheets 5 has a bowl-shaped cross section, and is continuously arranged so that both arc-shaped end portions thereof are in close contact with adjacent arc-shaped end portions. Further, it is pasted so that the hook-shaped cross section is arranged in the main scanning direction. This refractive sheet 5 is also called a lenticular lens. The lenticular lens is integrally formed of transparent glass or transparent acrylic resin. In FIG. 4, the refractive member is formed by attaching a refractive sheet to the emission portion 4 a of the trumpet-shaped light guide 4. The thing of the structure to perform may be sufficient.

  FIG. 5 illustrates a refractive sheet having a different shape, FIG. 5a illustrates a semicircular (semi-elliptical) lenticular lens, and FIG. Are arranged so as to be in close contact with each other, and the refractive sheet 5 having this shape is also referred to as a prism sheet. The prism sheet 5 is integrally formed of an acrylic resin.

  Next, the operation of the trumpet light guide 4 with the lenticular lens attached will be described with reference to FIG. FIG. 6 shows an optical path in the main scanning direction when the refracting sheet 5 is added on the emission part 4 a of the trumpet light guide 4 of the transmissive light source 2. In FIG. 6, the light emitted from the first light source 3 passes through the trumpet light guide 4 and is refracted and reflected by the refractive sheet 5 as diffused light. The reflected light is repeatedly reflected again, and finally re-radiated from the emitting portion 4a as refracted light. Therefore, by adding the refraction sheet 5 to the exit surface 4a of the trumpet light guide 4, the radiation angle component is dispersed, and even when there is no document, the angular distribution of rays passing through the position corresponding to the document surface is averaged and the illuminance is increased. It becomes uniform. The dispersed light emitted from the emitting unit 4 a passes through the glass plate 6 and is directly incident on the document 1 and the light receiving unit 14 as transmitted light of the transmissive light source 2. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  FIG. 7 is a diagram for explaining the output distribution and the bright output average value of each pixel in which various refractive sheets 5 are attached to the emitting portion 4a and the irradiation light from the transmissive light source 2 is measured by the light receiving portion. In the first embodiment, a case where a highly transparent document 1 such as an OHP sheet is mounted as a reading medium will be described. In the experiment, the number of pixels was 1536 bits, the pixel density (inter-pixel pitch) was 0.125 mm, and the photoelectric conversion output was measured with an 8-bit resolution (256 gradation resolution) output after amplification.

  In FIG. 7a, the display A is when the refractive sheet 5 is not attached to the emitting portion 4a, the display B is when a lenticular lens is attached, the reference display C is a case where a prism lens is attached in a single layer structure, The display is the output distribution of each pixel when a prism lens is attached in a two-layer structure. From FIG. 7a, it can be seen that by attaching the refractive sheet 5 to the emission part 4a of the trumpet type light guide 4, there is a decrease in bright output (the smaller the digit value, the lower the output), and the value is As shown in FIG. 7b, when the case where the refractive sheet 5 is not attached to the exit portion is 100 (A display), the average of the lenticular lens (B display) is about 66%. This means that the light transmittance is reduced as compared with the case where the refractive sheet is not attached.

  Next, a case where a document such as an OHP sheet is not mounted will be described. FIG. 8 is a diagram for explaining the illuminance deviation obtained from the output distribution of each pixel obtained by pasting the various refractive sheets 5 to the emission part 4 a and measuring the irradiation light from the transmissive light source 2 by the light receiving part 14. In FIG. 8 a, when the refractive sheet 5 is not attached to the emission part 4 a of the trumpet light guide 4, the direct light from the transmissive light source 2 is directly incident on the light receiving part 14 without passing through the document 1, so that the large illuminance Presents a deviation. On the other hand, when a lenticular lens is attached to the emitting portion 4a as shown in FIG. 8b, the illuminance deviation is improved to 27%, the illuminance uniformity is good, and it is used as a reference signal for light quantity adjustment and bit correction. Applicable.

  The deviation of the illuminance distribution (illuminance deviation) was defined as illuminance deviation (%) = {(imax−imin) / (imax)} · 100. Here, i represents the obtained illuminance value.

Embodiment 2. FIG.
In the first embodiment, the case where a lenticular lens is mainly applied as the refractive sheet 5 has been described. In the second embodiment, a case where a prism sheet is applied as the refractive sheet 5 will be described. As described above, the prism sheet is formed by arranging the triangular projections having a cross-sectional shape having a plane layer at the bottom thereof. As shown in FIG. When a single layer structure is applied to the light body 4, the bright output is high and the transmittance is improved as compared with the case where a lenticular lens is attached. That is, it can be seen that the bright output of the lenticular lens (B display) is 66%, whereas the prism lens single-layer structure (C display) is 74%, and the transmittance is high.

Embodiment 3 FIG.
In the second embodiment, the case where the prism sheet is attached in a single layer structure as the refractive sheet 5 has been described. However, in the third embodiment, the prism sheet as the refractive sheet 5 is formed in the trumpet type light guide 4. The case of pasting in will be described. When the prism sheet is attached in a two-layer structure, the planar layer of the second prism sheet is fixed to the apex of the triangular projection of the first prism sheet with an adhesive. In this case, as shown in FIG. 9, there is an improvement in illuminance deviation as compared with the case where one prism sheet is attached. That is, it can be seen that the illuminance deviation in the one-layer structure of the prism sheet is 43%, whereas it is 36% in the two-layer structure of the prism sheet, and the illuminance uniformity is good.

It is a cross-sectional block diagram of the image sensor by Embodiment 1 of this invention. It is sectional drawing of the LED chip mounted in the LED board of the image sensor by Embodiment 1 of this invention. It is a drive circuit block diagram of the image sensor by Embodiment 1 of this invention. It is an external view which added the refractive sheet to the light guide of the image sensor by Embodiment 1 of this invention. It is an external appearance schematic diagram of a refraction sheet. It is optical path explanatory drawing of the light irradiated from the transmissive | pervious light source of the image sensor by Embodiment 1 of this invention. It is explanatory drawing of the photoelectric conversion output distribution of the image sensor by Embodiment 1 thru | or 3 of this invention. It is explanatory drawing of the photoelectric conversion output of the image sensor by Embodiment 1 thru | or 3 of this invention. It is a figure explaining the illumination intensity deviation of the various refractive sheets of the image sensor by Embodiment 1 thru | or 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Original (object to be irradiated), 2 Transmission type light source, 3 First light source (LED chip), 4 Light guide (trumpet type light guide), 4a Ejection part (light emission part), 5 Refraction sheet, 6 Glass Plate, 7 LED substrate, 8 connector, 9 housing (transmission type light source housing), 10 second light source (LED chip), 11 light guide (refractive light guide), 11a emitting unit (light emitting unit) ), 12 glass plate, 13 rod lens array (lens array), 14 light receiving unit (sensor IC), 15 sensor substrate, 16 substrate, 17 signal processing IC (ASIC), 18 connector, 19 relay connector, 20 internal housing, 21 External housing.

Claims (6)

A light source arranged in the main scanning direction and a lens array extending in the main scanning direction for converging the light transmitted through the irradiation object with respect to the irradiation object conveyed in the sub-scanning direction orthogonal to the main scanning direction And a sensor that detects light converged by the lens array and arranged in the main scanning direction, and is disposed between the light source and the irradiated object, and repeatedly reflects light from the light source therein. A first light guide that guides light to the irradiated object side and a light emission side of the first light guide , and a plurality of protrusions are continuously formed along the main scanning direction. An image sensor comprising: a refracting unit that transmits light from the light source and refracts it to irradiate light in the main scanning direction of the irradiated object. A first light source arranged in the main scanning direction, and a first light guide for guiding the first light from the first light source to an irradiation object conveyed in the sub-scanning direction orthogonal to the main scanning direction; Provided on the light emitting side of the light body and the light guide of the first light guide, a plurality of protrusions are continuously formed along the main scanning direction, and allows the light from the first light source to pass through. A refracting unit that refracts and irradiates light in the main scanning direction of the irradiated object, a second light source arranged in the main scanning direction, and irradiates the irradiated object with light from the second light source. The second light guide for guiding light from the second light source side to the irradiated object side, the first light transmitted through the irradiated object, and the second light reflected from the irradiated object. A converging lens array, a sensor for photoelectrically converting the first light and the second light converged by the lens array, and a first sensor provided with the sensor A second substrate provided on the opposite side of the first substrate from the lens array side and provided with the second light source, and the sensor of the first substrate. A connector that is interposed between a surface opposite to the surface opposite to the surface of the second substrate and that transmits an electrical signal photoelectrically converted by the sensor from the first substrate to the second substrate; Image sensor equipped with. The image sensor according to claim 1, wherein a cross-sectional shape of the first light guide in a sub-scanning direction is a trumpet shape. The image sensor according to claim 1, wherein the first light guide and the refracting part are integrally formed of a resin material. The image sensor according to claim 1, wherein a cross-sectional shape of the protrusion of the refracting portion in a main scanning direction is a semicircular shape or a semielliptical shape. The image sensor according to claim 1, wherein a cross-sectional shape of the protrusion of the refracting portion in a main scanning direction is a triangular shape.

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