Contact image sensor, output correction device for contact image sensor, and output correction method for contact image sensor

A light source unit emits light for irradiating a document. A light guide in which light emitted from the light source unit propagates has a first exit part for emitting light to the document and a second exit part, which is a different part from the first light part, for emitting light to the outside. A corrective light receiver is disposed in an area receiving direct light of the light emitted from the second exit part, and outputs reference data corresponding to the direct light. A controller compares predetermined criterion data with the reference data output from the corrective light receiver, and performs processing for correcting a bright output based on a result of the comparison.

TECHNICAL FIELD

The present disclosure relates to a contact image sensor, an output correction device for the contact image sensor, and an output correction method for the contact image sensor.

BACKGROUND ART

A contact image sensor reads an image represented on a document M by irradiating the document M with light from a light source and converting light reflected by the document M into an electrical signal with a light receiving element, and then outputs the result as image data.

The amount of light emitted from the light source can fluctuate depending on various factors. The amount of light from the light source can fluctuate depending on the environmental temperature, for example, due to the temperature characteristic of the light source. The amount of light from the light source can also fluctuate due to chronological factors of the order of a few seconds to a few hours for a shorter elapsed time period to of the order of a few days to a few years for a longer elapsed time period.

For stable reading of the image of the document M by a contact image sensor despite fluctuations in the amount of light from the light source, a bright output that is an output of the contact image sensor when the document M is white is corrected. For example, when the image data output from the light receiving element depending on light reflected by a platen roller described in Patent Literature 1 or a white reference tape described in Patent Literature 2 is given as reference data, the bright output can be corrected by comparing the reference data with predetermined criterion data.

CITATION LIST

Patent Literature

Patent Literature 1: Unexamined Japanese Patent Application Kokai Publication No. H6-54189.

Patent Literature 2: Unexamined Japanese Patent Application Kokai Publication No. H7-79341.

SUMMARY OF INVENTION

Technical Problem

However, when the output of the light receiving element depending on light reflected by the platen roller is used as reference data, as described in Cited Reference 1, the reference data cannot be acquired because the light receiving element cannot receive light reflected by the platen roller while the document M is positioned. Therefore, the bright output cannot be corrected while the document M is positioned. The amount of light from the light source can fluctuate in a short time due to the environmental temperature, chronological factors, and the like, which can lead to instability of the bright output.

In Cited Reference 2, the white reference tape is provided on the platen glass in an area where the document M does not pass. The white reference tape and the platen glass often have different coefficients of linear expansion. Therefore, when the output of the light receiving element depending on light reflected by the white reference tape is given as reference data, a fluctuation in the environmental temperature can degrade the accuracy of the reference data. In addition, the presence of the document M or the density of the image represented on the document M can affect the accuracy of the reference data adversely. The bright output cannot be corrected accurately with the inaccurate reference data, which results in instability of the bright output.

The present disclosure is made to solve the problems described above, and an objective of the present disclosure is to provide a contact image sensor that enables a stable bright output to be obtained, and the like.

Solution to Problem

To achieve the foregoing objective, the contact image sensor of the present disclosure includes a light source that emits light for irradiating a target to be read, a light guide in which light emitted from the light source propagates, the light guide having a first exit part for emitting the light to the target to be read and a second exit part, which is a different part from the first light part, for emitting light to the outside, a corrective light receiver that is disposed in an area receiving direct light of the light emitted from the second exit part and outputs reference data corresponding to the direct light, a reading light receiver that generates image data representing an image of the target to be read by photoelectrically converting the light emitted from the first exit part and reflected by the target to be read, and a corrector that compares predetermined criterion data with the reference data output from the corrective light receiver and, based on a result of the comparison, performs processing for correcting a bright output indicated by the image data generated by the reading light receiver when the target to be read is white.

Advantageous Effects of Invention

According to the present disclosure, the reference data for correcting the bright output corresponds to direct light of the light emitted from the light guide. Thus, the bright output can be corrected based on the reference data that accurately reflects the amount of light emitted from the light source. Therefore, the stable bright output can be obtained.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure are explained with reference to the drawings. The same reference numerals denote the same elements throughout the drawings.

First Embodiment

A contact image sensor according to a first embodiment of the present disclosure is a device for reading an image of a document M that is a target to be read, and is mounted, for example, to a facsimile machine, a copier, a scanner, a multifunctional device, a banking terminal, an industrial inspection device, and the like. The target to be read is not limited to the document M, and can be, for example, an optical mark recognition sheet, paper money, security documents including a check and any other documents, and the like.

The contact image sensor irradiates with light a reading part that is predetermined as a location where the document M is in close contact with the reading part and that extends linearly in a main scanning direction. Thus the document M that is in close contact with the reading part is irradiated with linear light. The contact image sensor receives light reflected by the document M, and then reads the image of the linear part of the document M irradiated with light.

The contact image sensor reads the image on the reading surface of the document M by sequentially reading the image of the linear part of the document M while the contact image sensor moves relatively to the document M in a sub-scanning direction. Here, the sub-scanning direction is a direction transverse to the main scanning direction and, in the present embodiment, a direction perpendicular to the main scanning direction.

The contact image sensor100includes a frame101, a transmission body102, a lens body103, two light guides104, four light source units105, four corrective light receivers106, a retainer107, a sensor body108, and a controller109, as shown in the exploded perspective view ofFIG. 1.

As shown therein, the frame101is a box-shaped member with an open top, configured to have a rectangular bottom having a longitudinal direction defined as the main scanning direction and a transverse direction defined as the sub-scanning direction and side walls extending upwards from the outer edges of the bottom. The frame101can be made, for example, of a black resin. The bottom of the frame101has an opening extending longitudinally at the middle in the transverse direction.

The transmission body102is mounted on the top of the frame101so as to close the upper side of the frame. The sensor body108is mounted to the outside of the bottom of the frame101. The lens body103, the light guides104, the light source units105, the corrective light receivers106, and the retainer107are housed in a substantially closed space defined by the frame101, the transmission body102, and the lens body103. In the present embodiment, the controller109is disposed at the lower side of the sensor body108, but the controller109can be provided in any appropriate place.

The transmission body102is a member that transmits light with which the document M placed in close contact with the reading part110is irradiated and light reflected by the document M, and includes a transmissive section111and a retaining frame112.

As shown inFIG. 2, which is a plan view of the contact image sensor100, the transmissive section111has the linear reading part110extending in the main scanning direction on the external surface, and is a translucent, preferably, transparent flat plate made, for example, of a resin such as an acrylic or a polycarbonate, glass, and the like.

The retaining frame112is a frame which surrounds the circumference of the transmissive section111and retains the transmissive section111, and is made, for example, of a resin. The retaining frame112is mounted so that the outer edge is in close contact with the top of the frame101, as shown inFIG. 3which is a sectional view of the contact image sensor100as viewed in the main scanning direction, andFIG. 4which is a sectional view of the contact image sensor100as viewed in the sub-scanning direction. This enables the retaining frame112to close the upper side of the frame101to prevent entry of dust particles and the like.

The lens body103is a member that focuses light reflected by the document M to the sensor body108and extends in the main scanning direction as shown inFIG. 1. The lens body103has a plurality of rod lenses arranged in the longitudinal direction. Each rod lens is placed above the opening disposed in the bottom of the frame101with the optical axis arranged vertically, as shown inFIG. 3.

Each of the light guides104is an elongated cylindrical member in which light entering into each of the light guides propagates in the longitudinal direction. Each of the light guides104has an entrance part113, a first exit part114, a second exit part115, and a light diffusing layer116, as shown inFIG. 5, which is an enlarged view of the vicinities of the ends of the light guide104inFIGS. 3 and 4.

The entrance part113is a part of the external surface of the light guide104and from which light emitted from the light source unit105enters the light guide. The first exit part114is a part of the external surface of the light guide104, from which light is emitted toward the document M. The second exit part115is a part of the external surface of each of the light guides104, from which light is emitted toward the corrective light receiver106. The light diffusing layer116is a part that causes light propagating in the light guide104to be reflected and diffused, and can be formed such as by application of a light reflective material such as a white pigment, surface roughening of the light guide104, serrated prism shaping, or pyramid shaped embossing.

In the present embodiment, the entrance part113and the second exit part115are formed in the respective ends of each of the light guides104. The first exit part114and the light diffusing layer116are parts of the peripheral surface extending in the main scanning direction and are formed substantially symmetrically about the longitudinal axis of the light guide104.

Each of the light source units105is a member that emits light for irradiating the document M, and includes four light emitting diode (LED) chips117, an LED board118, a thermally conductive sheet119, and a heat sink120.

Each of the LED chips117is a light source that emits visible light (red, blue, green, and yellow), ultraviolet light having a wavelength on the order of 365 nm, infrared light having a wavelength on the order of 700-1000 nm, and the like. The four LED chips117form one set, and light emitted from the one set of LED chips117enters from the entrance part113of the one light guide104.

In the present embodiment, two light source units105share a single common LED board118. This means that the eight LED chips117that serve as light sources for emitting light are mounted on the surface of the LED board118. The LED chips117can be mounted directly on the LED board118, or can be provided as a package with the LED chips mounted on the LED board118.

The thermally conductive sheet119and the heat sink120are provided at the backside of the LED board118. The thermally conductive sheet119and the heat sink120dissipate heat generated by the LED chips117to the outside, so that the LED chips117can emit light efficiently. For example, a ceramic board, an aluminum board, a rigid flexible board, or the like is preferably used as the LED board118to improve the heat dissipation efficiency.

Each of the corrective light receivers106is configured as a photodiode or the like having light receiving sensitivity to light emitted from the LED chips117, and outputs an electrical signal depending on the amount of light received. One set of the LED chips117is provided in association with one corrective light receiver106. Therefore, in the present embodiment, the two corrective light receivers106are mounted on the surface of the one LED board118. The corrective light receivers106can be mounted directly on the LED board118, or can be provided as a package with the corrective light receivers106together with the LED chips117mounted on the LED board118.

The retainer107is a member for securing, in the frame101, the two light guides104and the light source units105provided with the corrective light receivers106, and includes two supports121and two holders122.

Each of the two supports121supports the one light guide104with the longitudinal direction oriented to the main scanning direction, and is provided so that the support covers the peripheral surface of the light guide104except the first exit part114.

Each of the holders122has two holes into which the ends of the light guides104fit. A projection is provided on the peripheral surface near each end of each light guide104, and upon fitting of each end into the hole of the holder122, each projection engages into the hole. This restrains movement of each light guide104in the main scanning direction and rotation around the longitudinal axis of the light guide104, in the frame101.

The two light guides104and the retainer107are secured in the frame101so that the supports121support the respective light guides104, the ends on the one side of the two light guides104are fitted into the respective holes in the one holder122, and the ends on the other side of the two light guides104are fitted into the respective holes in the other holder122. The two light guides104are secured in the frame101in parallel to each other with the longitudinal direction oriented to the main scanning direction by the retainer107, and are placed symmetrically with respect to the lens body103. In addition, as shown inFIG. 3, each of the light guides104is placed so that light propagating in the light guide and reflected and diffused by the light diffusing layer116is emitted from the first exit part114to the reading part110, that is, toward the document M. Note that the light diffusing layer116can be formed on each support121instead of or together with each light guide104.

As shown inFIG. 5, the LED boards118are mounted to the respective holders122so that the surfaces face the ends of the light guides104. By this, the set of the four LED chips117and the one corrective light receiver106are positioned facing all the respective ends of the two light guides104.

The positional relationship between the respective ends on the one side of the light guides104and the sets of the LED chips117and the corrective light receivers106is explained with reference toFIG. 3.

As shown therein, as viewed in the main scanning direction, one of the LED chips117is positioned in the center of the light guide104, and the other three LED chips117are each positioned equidistant from the center in the up, left, and right directions. The corrective light receiver106is positioned apart from the transmissive section111, that is, below the center of the light guide104so that the corrective light receiver is unlikely to receive light entering the contact image sensor100from the outside via the transmissive section111described in detail below.

The sensor body (reading light receiver)108receives light reflected by the document M via the lens body103, generates image data representing the read image by photoelectric conversion or the like, and then outputs the image data. The image data handled by the sensor body108is analog data and thus hereinafter referred to as analog image data. The sensor body108includes a sensor board123, a plurality of reading converters124, and amplifiers125, as shown inFIGS. 3 and 4.

The sensor board123is a rectangular board having substantially the same size as the bottom of the frame101, and the upper surface of the sensor board is positioned facing the external surface of the bottom of the frame101and is secured to the frame101, for example, by means of screwing.

The reading converters124are configured to have a plurality of photodiodes, capacitors, and the like, and have light receiving sensitivity to light emitted from the LED chips117. The reading converters124each generate an electrical signal depending on the received light, and then output the electric signal as analog image data acquired by photoelectric conversion. Specifically, the reading converter124produces photovoltaic power in response to the received light, and then generates an electrical signal depending on the received light by photoelectric conversion of light energy into an electrical signal.

The reading converters124are arranged on the upper surface of the sensor board123in the main scanning direction, and when the sensor board123is fixed to the frame101, are positioned in or below the opening at the bottom of the frame101.

The amplifier125is configured, for example, as a circuit disposed on the sensor board123, and amplifies the electrical signal generated by the reading converters124and then outputs the amplified electrical signal. The amplifier125outputs the generated electrical signal as amplified analog image data.

The controller109performs correction processing of the bright output, output processing of the image data representing the document M, and the like by transmitting and receiving various signals (data) to and from the reading converters124, the light source units105, and the corrective light receivers106. The image data output from the controller109is digital data. The image data that is digital data is hereinafter referred to as digital image data.

Here, the bright output is contents (such as each pixel value) indicated by image data that is generated by the contact image sensor100when a white target to be read is read. Specifically, the bright output is the contents indicated by the image data that is generated by the reading part110when the target to be read is white.

The controller109is configured to have an electrical circuit, a microcomputer, a flash memory, and the like, or any combination thereof. As shown inFIG. 6, the controller109functionally includes an LED driver126, a corrective A/D (Analog/Digital) converter127, a storage128, a comparative corrector (corrector)129, a synchronous controller130, a reading A/D converter131, a shading corrector132, and an image processor133.

The LED driver126controls the amount of light by controlling, for example, the magnitude of current applied to the LED chips117, the length of time for which current is applied to the LED chips117, and the like, while causing the LED chips117to emit light.

The corrective A/D converter127converts an electrical signal that is analog data output from the corrective light receiver106into reference data that is digital data.

The storage128stores criterion data indicating a criterion of the bright output. The criterion data is stored in the storage128, for example, upon shipping of the contact image sensor100, initial operation of the contact image sensor100, or the like. An example of data to be set as the criterion data is amount of light from the LED chips117received by the corrective light receivers106at a timing of storing as stated above.

The comparative corrector129compares the reference data generated by the corrective A/D converter127with the criterion data in the storage128. Then, the comparative corrector129causes the LED driver126to change the length of time for which current is applied to the LED chips117, the magnitude of the current, and/or the like so that the content of the reference data meets the criterion indicated by the criterion data. This changes the amount of light emitted by the LED chips117, thereby correcting the bright output. Specifically, for example, the bright output is corrected so that each value indicated by the reference data is equal to the value indicated by the criterion data.

Note that the comparative corrector129can correct the bright output based on the reference data that is analog data and the criterion data associated therewith.

The synchronous controller130outputs a synchronization signal for synchronizing light emission of the LED chips117with one or both of photoelectric conversion of the reading converters124and A/D conversion of the corrective A/D converter127to the LED driver126and one or both of the reading converters124and the corrective A/D converter127. The reading A/D converter131generates digital image data by converting the analog image data amplified by the amplifier125of the sensor body108into digital data. The shading corrector132generates shading-corrected digital image data by acquiring the digital image data from the reading A/D converter131and then performing shading correction. The image processor133acquires the digital image data shading corrected by the shading corrector132and generates image data by performing predetermined image processing, and then outputs the image data.

For example, when the contact image sensor100is applied to an industrial inspection device, the image processor133can determine whether the target to be read meets the inspection criteria by collating the generated image data with the pre-stored determination data. Here, the determination data indicates a criterion for determining whether the target to be read meets the inspection criteria. Then, the image processor133can output data that indicates the determination result.

As a further example, when the contact image sensor100is applied to a reading device for an optical mark recognition sheet, the image processor133can identify selected marks on the optical mark recognition sheet, and then output data indicative of the identified result. Specifically, the image processor133identifies the selected marks on the optical mark recognition sheet by locating the selected marks on the optical mark recognition sheet from the generated image data and then collating the locations of the marks with pre-stored identification data, for example. Here, the identification data indicates, for example, a location represented by each of the marks (numerals, alphabets, symbols, and the like) on the optical mark recognition sheet.

The configuration of the contact image sensor100according to the first embodiment of the present disclosure has been explained. The operation of the contact image sensor100is explained with reference to the drawings hereafter.

The contact image sensor100performs general read processing, as shown inFIG. 7, in response to reading synchronization signal from the synchronous controller130with the document M in close contact with the reading part110. The contact image sensor100performs read processing repeatedly while moving relatively to the document M in the sub-scanning direction with the document M in close contact with the reading part110, thereby reading the image of the reading surface of the document M and then generating and outputting image data representing the image.

As shown therein, the LED driver126causes the LED chips117to emit light upon receiving the reading synchronization signal from the synchronous controller130(step S101). The LED driver126then controls the amount of light emitted from the LED chips117by controlling the magnitude of current applied to the LED chips117, the length of time for which current is applied to the LED chips117, and the like to be a predetermined magnitude, length, and the like, respectively.

Light emitted from the LED chips117enters the light guides104from the end of the light guides104facing the LED chips117. Light entering the light guides104propagates in the light guides104in the main scanning direction while totally reflecting. The light scattered and reflected on the light diffusing layer116, which is a part of the light propagating in the light guides104, is emitted from the first exit part114.

Here, the supports121of the retainer107are, as described above, provided so as to cover the peripheral surfaces except the first exit parts114of the light guides104. The light not totally reflected in the light guides104leaks from the peripheral surface except the first exit part114to the outside of the light guides104and is reflected by the supports121. Therefore, the supports121covering the peripheral surfaces except the first exit parts114of the light guides104can improve extraction efficiency of light emitted to the document M that is the target to be read.

The document M that is in close contact with the reading part110is irradiated via the transmissive section111with the light emitted from the first exit part114, and then the light is reflected by the document M. The light reflected by the document M passes through the lens body103via the transmissive section111. The light passing through the lens body103converges to each light receiver of the reading converters124and is then received by the light receiver.

Each of the reading converters124performs photoelectric conversion for generating an electrical signal depending on the received light (step S102). Each of the reading converters124outputs analog image data acquired by the photoelectric conversion. Here, the analog image data output from the reading converters124included in the sensor body108represents the image of the linear part of the document M that is in close contact with the reading part110.

The amplifier125amplifies the electrical signal output from each of the reading converters124, that is, the analog image data acquired by the photoelectric conversion (step S103). The amplifier125outputs the amplified analog image data.

The reading A/D converter131converts the amplified analog image data into digital image data (step S104). The reading A/D converter131then outputs the digital image data acquired by the conversion.

The shading corrector132applies predetermined shading correction processing to the digital image data output from the reading A/D converter131(step S105). The shading corrector132outputs the digital image data that has been shading corrected.

The image processor133performs predetermined image processing on the digital image data that has been shading corrected by the shading corrector132(steps S106). The image processor133then outputs the digital image data that has processed with the image processing. The image processor133completes the read processing.

The application of such read processing sequentially generates read data, digitally converted data, shading corrected data, and image data, all of which represent the image of the linear part of the document M that is in close contact with the reading part110. The contact image sensor100performs read processing repeatedly while moving relatively to the document M in the sub-scanning direction with the document M in close contact with the reading part110, and thus acquires image data representing image of the reading surface of the document M.

The contact image sensor100performs output correction processing as shown inFIG. 8. The output correction processing is processing for correcting the bright output and is performed in response to the output correcting synchronization signal from the synchronous controller130. The output correcting synchronization signal can be, for example, common to the reading synchronization signal as stated above, can be output upon startup of the contact image sensor100, or can be output in response to operation applied to an operation unit not shown.

As shown therein, the LED driver126causes the LED chips117to emit light upon receiving the output correcting synchronization signal from the synchronous controller130(step S111). As with the light emission processing in step S101, the LED driver126then controls the amount of light emitted from the LED chips117.

Note that when the output correcting synchronization signal and the reading synchronization signal are common, step S111and step S101are the same processing.

The light emitted from the LED chips117positioned facing one end of the respective light guides104propagates in the light guides104, and then is received by the corrective light receiver106positioned facing the other ends of the light guides104. The corrective light receiver106performs photoelectric conversion for generating an electrical signal corresponding to the received light (step S112). The corrective light receiver106then outputs an electrical signal that is analog data generated by the photoelectric conversion.

Upon receiving of a synchronization signal from the synchronous controller130, the corrective A/D converter127then generates reference data by A/D converting the electrical signal that is analog data acquired from the corrective light receiver106(step S113). The reference data is digital data indicative of the amount of light received from the LED chips117by the corrective light receiver106upon receiving of the synchronization signal from the synchronous controller130.

The comparative corrector129acquires reference data from the corrective A/D converter127and reads criterion data from the storage128(step S114).

The comparative corrector129compares the reference data with the criterion data (step S115).

The comparative corrector129determines whether the bright output is required to be corrected or not, based on the comparison result (step S116). For example, when the reference data and the criterion data each indicate the same value, the comparative corrector129determines that the bright output is not required to be corrected (step S116; No), and then ends the output correction processing.

For example, when the reference data and the criterion data each indicate the different values, the comparative corrector129determines that the bright output is required to be corrected (step S116; Yes).

The comparative corrector129controls the LED driver126so that the reference data and the criterion data each indicate the same value. Specifically, the comparative corrector129adjusts the amount of light from the LED chips117by causing the LED driver126to change the magnitude of current applied to the LED chips117and the length of time for which current is applied to the LED chips117. The comparative corrector129thereby corrects the bright output (step S117), and then ends the output correction processing.

In the present embodiment, the corrective light receiver106directly receives light that has propagated in the light guides104. The bright output is then corrected based on the reference data corresponding to direct light received by the corrective light receiver106. The output correction processing can be thus performed at any time, for example, depending on light emitted during read processing with or without the document M. Therefore, the bright output can be corrected even when the amount of light from the LED chips117varies due to not only long term degradation of the LED chips117but also due to environmental temperatures, short-term chronological factors, and the like. This thus enables obtaining stable bright output.

In addition, the corrective light receivers106receives direct light that has propagated in the light guides104, and does not receive indirect light emitted from the light guides104and reflected by members such as a platen roller, a white reference tape, and the like. The reference data that accurately reflects the amount of light emitted from the LED chips117can be thus acquired without the influence of degradation of intervening members, dirt, and the like. This thus enables obtaining stable bright output.

In addition, the image data output from the sensor body108can transiently vary during the warm-up time after power-up. In the present embodiment, the bright output is not substantially affected by transient variations of the image data output from the sensor body108because the bright output is corrected based on the reference data corresponding to direct light received by the corrective light receiver106. Therefore, even during the warm-up time after power-up, the bright output can be corrected and the stable bright output can be obtained.

Acquisition of the stable bright output can improve either one of the quality of the read image, determination accuracy in inspection, identification accuracy of selected marks on an optical mark recognition sheet, and the like, that is suitable for the application of the device to which the contact image sensor100is implemented.

In addition, the corrective light receiver106is not irradiated directly by external light transmitted through the transmission body102or light reflected by the document M, and the external light or the reflected light is required to pass at least through the light guides104before being received by the corrective light receiver106. Therefore, the influence on light received by the corrective light receiver106due to the external light or the reflected light can be reduced. This can improve the accuracy of the reference data, which enables obtaining the stable bright output.

With the LED chips117emitting ultraviolet light, for example, acquisition of the reference data itself can be difficult when the reference data is acquired upon receiving of light reflected by a platen roller, a white reference tape, or the like. Moreover, even when the reference data can be acquired, degradation over time can be significant and this can result in poorer accuracy. According to the present embodiment, the corrective light receiver106directly receives light that has propagated in the light guide104. Use of the corrective light receiver106having a sensitivity to ultraviolet light thus enables accurate reference output of ultraviolet light to be obtained even with the LED chips117emitting ultraviolet light. Therefore, the stable bright output can be obtained even with ultraviolet light. Similarly, the stable bright output can be obtained even with infrared light.

In the present embodiment, the bright output can be corrected by causing the LED driver126to control the amount of light emitted by the LED chips117. The LED driver126is provided in a typical contact image sensor100. Therefore, an increase in the number of parts for correcting the bright output can be mitigated and the stable bright output can be obtained with a simple configuration.

Second Embodiment

A contact image sensor according to the present embodiment differs from the contact image sensor100according to the first embodiment in arrangement of light source units and corrective light receivers.

The contact image sensor200according to the present embodiment includes light source units205and corrective light receivers206that are respectively positioned facing one end and the other end of the respective light guides104, as shown inFIG. 9, which is a sectional view as viewed in the main scanning direction, andFIG. 10, which is a sectional view as viewed in the sub-scanning direction. The light source unit205includes four LED chips217disposed on an LED board, as shown inFIG. 11as viewed in the main scanning direction, and the LED chips217are each positioned facing the one end of the light guide104at equidistant positions from the center of the one end of the light guide104in the up, down, left, and right directions.

The contact image sensor200according to the present embodiment operates similarly as in the first embodiment. As shown inFIGS. 9 and 10, light emitted from the light source unit205thus enters from the one end (entrance part213) of the light guide104and then propagates in the light guide104. A part of the light propagating in the light guide104is emitted from the other end (second exit part215) of the light guide104and is received directly by the corrective light receiver206. Then, the corrective light receiver206generates an electrical signal corresponding to the received light, and then corrects bright output based on reference data generated from the electrical signal. Therefore, the stable bright output can be obtained as in the first embodiment.

In the present embodiment, LED board218with the LED chips217is positioned at the one end of each light guide104, and corrective light receivers206is positioned at the other end, for example, with the corrective light receiver206mounted on a board. The corrective light receiver206generates relatively less heat, so that no thermally conductive sheet119or heat sink120is required to be provided on the corrective light receiver206. This thus enables the reduced number of parts constituting the contact image sensor200and the more compact contact image sensor200.

Third Embodiment

A contact image sensor according to the present embodiment differs from the contact image sensor200according to the second embodiment in arrangement of corrective light receivers.

In the contact image sensor300according to the present embodiment, LED chips217of light source units205similar to the second embodiment are positioned at the one end of each of the light guides104, as shown inFIG. 11. Also, a support121and a frame101are provided with a hole334extending therethrough downwardly from a second exit part315formed on the peripheral surface near the other end of each of the light guides104to the upper surface of a sensor board123.

The contact image sensor300according to the present embodiment operates similarly as in the first embodiment. Light emitted from the light source unit205thus enters from the one end (entrance part) of the light guide104and then propagates in the light guide104, as in the second embodiment. A part of the light propagating in the light guide104is emitted downwardly from a part (second exit part315) of the peripheral surface near the other ends of the light guides104and is received directly by the corrective light receiver306. Then, the corrective light receiver306generates an electrical signal corresponding to the received light, and then corrects bright output based on reference data generated from the electrical signal. Therefore, the stable bright output can be obtained as in the first embodiment.

In the present embodiment, the corrective light receiver306is provided near the each end of the each light guide104, but the corrective light receiver306has a larger distance from the transmission body102than the corrective light receiver106according to the first embodiment. Therefore, the influence on light received by the corrective light receiver306due to the external light or the light reflected by the document M can be further reduced. This can improve the accuracy of the reference data, which enables the stable bright output to be obtained.

Fourth Embodiment

A contact image sensor according to the present embodiment differs from the contact image sensor100according to the first embodiment in shape of light guides and arrangement of corrective light receivers.

As shown inFIG. 12, which is a sectional view of the contact image sensor400according to the present embodiment as viewed in the sub-scanning direction, light guides404are members that extend in the main scanning direction and taper from the center toward both ends. A V-shaped notch435is provided on the top at the center. The section of the light guide404as viewed in the main scanning direction is, for example, in the form of an isosceles trapezoid having a wider base at the lower side, a first exit part414is provided on the upper surface of the light guide404, and a second exit part415is provided on the lower surface of the light guide404positioned below the notch435. A light diffusing layer416is provided on the lower surface of the light guide404except the second exit part415.

Light source units405are positioned near the respective ends of the light guides404, and LED chips of the light source units405are positioned facing the respective ends of the light guides404. The corrective light receivers406are in the center of the light guides404in the main scanning direction and are positioned facing or in contact with the lower surface.

The contact image sensor400according to the present embodiment operates similarly as in the first embodiment. Light emitted from the light source units405thus enters from the each end (entrance part413) of the light guides404and then propagates in the light guides404toward the center. A part of light propagating near the center of the light guide404is reflected downwardly by the V-shaped notch and emitted from the lower surface (second exit part415) near the center of the light guide404, and then received by the corrective light receiver406. Then, the corrective light receiver406generates an electrical signal corresponding to the received light, and subsequently corrects bright output based on reference data generated from the electrical signal. Therefore, the stable bright output can be obtained as in the first embodiment.

Fifth Embodiment

A contact image sensor according to the present embodiment differs from the contact image sensor100according to the first embodiment in shape of light guides and arrangement of light source units and corrective light receivers.

FIG. 13shows the contact image sensor500according to the present embodiment as viewed in the main scanning direction. Each of the light guides504is a member having the same cross section extending in the main scanning direction, and integrally includes a fore section536located closer to the center of the frame101and a rear section537located closer to the side wall of the frame101.

The fore section536has ends perpendicular to the main scanning direction and a first exit part514is provided on the top of the fore section536. The rear section537has ends forming an acute angle with the interface between the rear section537and the fore section536, as shown inFIG. 14, which is an enlarged plan view of a portion near the end of the light guide504. A light diffusing layer516is provided on the bottom of the fore section536and the rear section537, and a first exit part514is provided on the top of the fore section536.

As shown inFIG. 14, LED chips517of the light source unit505and the corrective light receiver506are positioned facing the respective ends of the fore section536and the rear section537. The corrective light receiver506is provided on an LED substrate518included in the light source unit505, as in the first embodiment.

The contact image sensor500according to the present embodiment operates similarly as in the first embodiment. Light emitted from the light source unit505thus enters from the one end (entrance part513) of the fore section536of the light guide504and then propagates in the light guide504. A part of the light propagating in the light guide504is emitted downwardly from the other end (second exit part515) of the rear section537of the light guide504and is received directly by the corrective light receiver506. Then, the corrective light receiver506generates an electrical signal corresponding to the received light, and then corrects bright output based on reference data generated from the electrical signal. Therefore, the stable bright output can be obtained as in the first embodiment.

Sixth Embodiment

A contact image sensor according to the present embodiment differs from the contact image sensor100according to the first embodiment in shape of light guides and arrangement of light source units and corrective light receivers.

FIG. 15shows a sectional view of the contact image sensor600according to the present embodiment as viewed in the sub-scanning direction. Light guide604is a member extending in the main scanning direction and having a section, for example, in the form of an isosceles trapezoid having a reduced width from the upper to the lower in the sub-scanning direction, as shown inFIG. 16, which is an enlarged perspective view of the vicinity of the end of the light guide. A light diffusing layer616is provided on the bottom of the light guide604and a first exit part614is provided on the top of the light guide604. As shown therein, the end of the light guide604has a pair of inclined surfaces, and the inclined surfaces are provided symmetrically with respect to the vertical plane that is parallel to the main scanning direction.

A light source unit605includes an LED board618and LED chips617mounted on the LED board618, as shown inFIG. 17, which is an enlarged view of the vicinity of the end of the light guide604as viewed from above. The LED chips617are positioned facing one of the inclined surfaces of the light guide604. A corrective light receiver606is provided on the LED board618, and is positioned facing the other of the inclined surfaces of the light guide604.

Note that the end of the light guide604can have a plurality of pairs of inclined surfaces symmetric with respect to a plurality of respective different faces and, for example, the corrective light receiver606can be positioned facing one of the inclined surfaces, while the LED chips617can be positioned facing the other respective inclined surfaces.

The contact image sensor600according to the present embodiment operates similarly as in the first embodiment. Light emitted from the light source unit605thus enters from one (entrance part613) of the inclined surfaces provided on the one end of the light guide604, and then propagates in the light guide604. A part of the light propagating in the light guide604is emitted from the other (second exit part615) of the inclined surfaces provided on the other end of the light guide604and is received directly by the corrective light receiver606. Then, the corrective light receiver606generates an electrical signal corresponding to the received light, and then corrects bright output based on reference data generated from the electrical signal. Therefore, the stable bright output can be obtained as in the first embodiment.

Seventh Embodiment

A contact image sensor according to the present embodiment differs from the contact image sensor100according to the first embodiment in shape of light guides and arrangement of light source units and corrective light receivers.

FIG. 18is an enlarged view of light guide end portions739as the contact image sensor700is viewed in the sub-scanning direction. The light guide end portions739are portions located near the ends of the light guides704and having extension portions740extending in the main scanning direction. The extension portion740has a downwardly facing extended end and inclined surface having a shape with a portion of an elliptical profile extruded in the sub-scanning direction. As shown inFIG. 18, light source units705and corrective light receivers706are positioned facing the extended ends. The LED chips717of the light source units705are provided on an LED board718, and the corrective light receivers706are also provided on the LED board718.

The contact image sensor700according to the present embodiment operates similarly as in the first embodiment. Light emitted from the light source unit705thus enters from one (entrance part713) of the extended ends of the light guide704and then propagates in the light guide704. A part of the light propagating in the light guide704is emitted from the other end (second exit part715) of the extended ends of the light guide704and is received directly by the corrective light receiver706. Then, the corrective light receiver706generates an electrical signal corresponding to the received light, and then corrects bright output based on reference data generated from the electrical signal. Therefore, the stable bright output can be obtained as in the first embodiment.

Eighth Embodiment

In the first embodiment, the bright output is corrected by adjusting the amount of light from the LED chips117. In the present embodiment, the bright output is corrected by adjusting an output level of a sensor body by an amplifier.

The contact image sensor according to the present embodiment has construction generally similar to the contact image sensor100according to the first embodiment. A controller809of the contact image sensor according to the present embodiment has a different construction from the controller109according to the first embodiment.

The controller809according to the present embodiment includes a comparative corrector829instead of the comparative corrector129according to the first embodiment, as shown inFIG. 19. The comparative corrector829causes the amplifier125to change the output level so that the content of the reference data meets the criterion represented by the criterion data. The content of the analog image data output from the sensor body108is thus changed, which enables obtaining the bright output.

The contact image sensor according to the present embodiment performs read processing and output correction processing similar to the first embodiment. In the present embodiment, in step S117of output correction processing as shown inFIG. 8, the comparative corrector829adjusts the content of the analog image data by causing the amplifier125to change the output level.

In the present embodiment, the bright output is corrected by causing the amplifier125to control the output level. The amplifier125is provided in a typical contact image sensor. Therefore, an increase in the number of parts for correcting the bright output can be mitigated and the stable bright output can be obtained with a simple configuration.

Although the foregoing describes some example embodiments and variations of the present disclosure, the present disclosure is not limited thereto. The present disclosure has any appropriate combination of the embodiments and variations, and modifications added thereto as appropriate.

This application claims the benefit of priority based on Japanese Patent Application No. 2012-178137, filed on Aug. 10, 2012, the entire disclosure of which is incorporated by reference herein.

REFERENCE SIGNS LIST