1. Field of the Invention
The present invention relates to a recording-medium identification device for identifying the type of recording medium fed by analyzing the optical characteristic thereof.
2. Description of the Related Art
Hitherto, various kinds of recording devices such as copiers, facsimile machines, printers, and so forth, have been used to perform printing on recording mediums such as sheets of paper, plastic sheets for an overhead projector (hereinafter referred to as an OHP sheet), and so forth. These recording devices can establish the best printing mode according to the type of recording mediums. For example, an ink-jet printer can change its ink-jetting mode so as to form a suitable image according to the type of recording medium, such as a plain-paper sheet, a high-quality-paper sheet, the OHP sheet, and so forth. In the past, a user of the recording device usually would manually set the type of a recording medium. However, when the user performs the setting improperly or neglects to perform the setting because of its complex procedures, it is impossible for the user to perform printing properly according to the type of the recording medium. Therefore, for solving the above-described problems, techniques for adding a recording-medium identification device to identify the type of recording medium for the recording device have been introduced.
For example, the following two methods are among those which have been introduced to identify the type of recording medium. According to a first method, the type of a recording medium is identified by measuring the thickness of the recording medium. According to a second method, the type of a recording medium is identified by reflecting light off the print surface of the recording medium and observing the reflected light to identify the type of recording medium.
Japanese Patent Laid-Open No. 8-188322 discloses the above-described first method. According to this method, however, the print-surface condition of the recording medium cannot be measured directly. Therefore, it has been difficult to identify the print-surface condition with precision and determine the type of the recording medium.
Japanese Patent Laid-Open No. 10-198093 discloses the above-described second method. In this method, a light-emitting element and a reflected-light-receiving element are provided adjacent the print surface of the recording medium. The light applied on the recording medium is reflected by the print surface thereof, whereby the type of the recording medium is identified. In this case, the print-surface condition can be determined directly. However, it is difficult to determine the print-surface condition with precision using only two parameters, that is, the specularly reflected light and the diffusely reflected light that are observed. This problem occurs in the case where specularly reflected light and diffusely reflected light obtained by a first recording medium and those obtained by a second recording medium, the second recording medium being different from the first recording medium in type, are similar to one another.
Recording media such as the high-quality-paper sheets and the plain-paper sheets other than OHP or coated-paper sheets produce a small amount of specularly reflected light. Since it is difficult to differentiate between the high-quality-paper sheet and the plain-paper sheet according to the intensity and amount of diffusely reflected light obtained by these two paper-sheets, the differentiation is often performed improperly. Thus, it has been difficult to identify with precision the type of a recording medium according to the above-described methods.
It is an object of the present invention is to provide a recording-medium identification device for identifying various types of recording media with precision and stability.
According to an aspect of the present invention, there is provided a recording-medium identification device for identifying a recording medium type. The recording-medium identification device comprises a light emitting unit for reflecting light off a surface of the recording medium, the light emitting unit applying light on the surface in a predetermined direction other than a direction normal to the surface, a detection unit for detecting an amount of light reflected in a backward direction of the light emitted by the light emitting unit, and an identification unit for identifying the type of the recording medium based on the amount of light detected by the detection unit.
Preferably, the detection unit further comprises a specularly-reflected-light detection unit for detecting the amount of specularly reflected light of the light reflected off the surface of the recording medium. Therefore, it becomes possible to identify the recording medium type with precision higher than that in the past.
Preferably, the detection unit further comprises a diffusely-reflected-light-detection unit for detecting an amount of diffusely reflected light of the light reflected off the surface of the recording medium. The diffusely reflected light is reflected at a predetermined angle other than the angle at which the light applied by the light emitting unit is made incident. Therefore, it becomes possible to identify the recording medium type with precision higher than that in the past.
The light emitting unit may preferably be a laser light. Accordingly, it becomes possible to emit lights that travel in straight lines and that are of the same wavelength and in the same phase and make diffusely reflected lights interfere with one another.
Preferably, the detection unit includes a semiconductor light receiving element for detecting the amount of received light reflected off the surface of the recording medium. Accordingly, it becomes possible to convert the received light into an electrical signal and measure the electrical signal.
The recording-medium identification device may further comprise a reflector positioned between the light emitting unit and the recording medium to reflect in a predetermined direction light reflected off the surface of the recording medium.
According to the present invention, therefore, it becomes possible to correctly identify the type of a recording medium by measuring the diffusely reflected light reflected by the recording medium into a backward direction, that is, a direction opposite to the direction in which the applied light is made incident. This diffusely reflected light is referred to as coherent backscattering of light.
Preferably, the reflector is a half mirror.
According to another aspect of the present invention, there is provided a recording-medium identification device for identifying a recording medium type. The recording medium identification device comprises a light emitting unit for reflecting light off a surface of the recording medium. This light emitting unit is positioned to direct light onto the surface of the recording medium in a predetermined direction other than a direction normal to the surface of the recording medium. The recording medium identification device further comprises a specularly-reflected-light receiving element provided at a predetermined position so as to receive specularly reflected light at a predetermined angle the same as that at which the light emitted from the light emitting unit was made incident, a half mirror positioned between the light emitting unit and the recording medium to reflect light in a direction generally perpendicular to the direction of the light emitted from the light emitting unit, a coherent-backscattering-of-light receiving element for receiving light reflected from the half mirror, and an identification unit for identifying the type of recording medium based on the amount of light detected by the specularly-reflected-light receiving element and the coherent-backscattering-of-light receiving element.
Preferably, the half mirror and the coherent-backscattering-of-light receiving element are combined and movable in unison.
Preferably, the light emitting unit is movable.
Preferably, the recording-medium identification device further comprises a diffusely-reflected-light receiving element provided at a position so as to receive diffusely reflected light reflected at a predetermined angle other than the angle at which the light emitted from the light emitting unit is made incident. The identification unit may also base the identification of the type of recording medium on an amount of light detected by the diffusely-reflected-light receiving element.
According to another aspect of the present invention, there is provided a recording-medium identification device for identifying a recording medium type. The recording medium identification device comprises a light emitting unit for reflecting light off a surface of the recording medium. This light emitting unit is positioned to direct light onto the surface of the recording medium in a predetermined direction other than a direction normal to the surface of the recording medium. The recording medium identification device further comprises a specularly-reflected-light receiving element provided at a predetermined position so as to receive specularly reflected light at a predetermined angle the same as that at which the light emitted from the light emitting unit was made incident, a half mirror positioned between the light emitting unit and the recording medium to reflect light in a direction generally perpendicular to the direction of the light emitted from the light emitting unit, and a movable coherent-backscattering-of-light receiving element for receiving light reflected from the half mirror. The coherent-backscattering-of-light receiving element is movable between a position where it receives light reflected from the half mirror and a position where it receives diffusely reflected light reflected at a predetermined angle other than the angle at which light emitted from the light emitting unit is made incident. The recording medium identification device further comprises an identification unit for identifying the type of recording medium based on an amount of light detected by the specularly-reflected-light receiving element and an amount of light detected by the coherent-backscattering-of-light receiving element at the end of the two positions.
According to another aspect of the present invention, there is provided a recording-medium identification device for identifying a recording medium type. This recording-medium identification device comprises a light emitting unit for reflecting light off a surface of the recording medium. This light emitting unit applies light on the surface in a predetermined direction other than a direction normal to the surface of the recording medium. The recording-medium identification device further comprises a half-mirror positioned between the light emitting unit and the recording medium to reflect light in a direction generally perpendicular to the direction of the light emitted from the light emitting unit and a single light receiving element. This light receiving element is movable between a first position where the light receiving element receives specularly reflected light reflected off the recording medium, a second position where the light receiving element receives diffusely reflected light reflected off the recording medium, and a third position where the light receiving element receives coherent backscattering of light reflected off the half mirror. The recording-medium identification device further comprises an identification unit for identifying the type of recording medium based on respective outputs of an amount of light detected by the light receiving element at the first position, the second position and the third position.
According to another aspect of the present invention, there is provided a recording-medium identification method for identifying a recording medium type using a recording-medium identification device comprising a light emitting unit for reflecting light off a surface of the recording medium, the light-emitting unit applying light on the surface in a predetermined direction other than a direction normal to the surface. The recording-medium identification method comprises the steps of detecting an amount of light reflected in a backward direction of the light emitted by the light emitting unit and identifying the type of the recording medium based on the amount of light detected in the step of detecting an amount of light.
Preferably, in the step of detecting an amount of light, an amount of light specularly reflected off the surface of the recording medium is further detected.
Preferably, in the step of detecting an amount of light, an amount of light diffusely reflected off the surface of the recording medium at a predetermined angle other than the angle at which the light applied by the light emitting unit is made incident is further detected.
As has been described, according to the present invention, it becomes possible to receive the specularly reflected light, the coherent backscattering of light, and the diffusely reflected light that are generated by light applied on a recording medium by a laser-light source and compare these specularly reflected light, coherent backscattering of light, and diffusely reflected light to stored identification reference so as to identify the recording medium type with precision higher than that in the past.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments (with reference to the attached drawings).
Preferred embodiments of the present invention will now be described with reference to the attached drawings.
As shown in
A predetermined position on the surface of the recording medium 0 is determined to be an irradiation-reference position IRP. Then, the laser-light source 1 is provided in a predetermined position at a 180°-θ angle with respect to the irradiation-reference position IRP (0°<θ<90°). The specularly-reflected-light-receiving element 2 is provided at a predetermined position at a θ angle with respect to the irradiation-reference position IRP. The half mirror 4 is provided at a predetermined position on an optical path between the laser-light source 1 and the irradiation-reference position IRP on the recording medium 0 so as to reflect coherent backscattering of light from the irradiation-reference position IRP. The light emitted from the laser-light source 1 is made incident through the optical path. The coherent-backscattering-of-light-receiving element 3 is provided at a predetermined position so as to receive the coherent backscattering of light reflected by the half mirror 4. The diffusely-reflected-light-receiving element 5 is provided at a predetermined position other than the positions in which the specularly-reflected-light receiving element 2 and the coherent-backscattering-of-light-receiving element are provided. These light-receiving elements (photo sensors) can be formed of various kinds of photo diodes such as PIN-photo diodes, an avalanche-photo diode, and so forth.
The coherent backscattering of light will now be described as below.
In the case where laser light is used as the light that is made incident so as to be applied to the print surface of the recording medium 0 and predetermined conditions are satisfied, interference may occur among the diffusely reflected light of coherent components. When the diffusely reflected light of one of the coherent components and the diffusely reflected light of another propagate in the same optical path, they reach an observation surface in the same phase, for they propagate the same distance. In this case, the diffusely reflected light and the other diffusely reflected light interfere with each other so that the combined intensity increases. This increase corresponds to a coherent-backscattering phenomenon. In this case, the intensity of the diffusely reflected light observed in a direction in which the incident light goes back, that is, the backward direction, is twice as high as the intensity of diffusely reflected light of isotropic scattered components. The isotropic scattered components are normal scattered components that are reflected at angles other than that at which the light emitted from the laser-light source 1 is made incident. In this case, the observed intensity of the diffusely reflected light is the sum of the isotropic scattered components and the coherent components. Therefore, the peak of the intensity distribution points in the backward direction (refer to
The intensity of the coherent backscattering of light is changed according to the configuration of dispersed particles on a reflection surface. In this case, the reflection surface is the surface of the recording medium. Since the coherent backscattering of light from the recording medium includes the information about the recording medium, it becomes possible to determine the type of the recording medium based on that information. In particular, when the recording medium is neither an OHP sheet nor a sheet of glossy paper, but a sheet of high-quality paper or a sheet of plain paper, the type of the recording medium can be efficiently identified by using the coherent backscattering of light. That is to say, even though it is not possible to determine the size and material of an anisotropic particle by using the coherent backscattering of light, it is possible to observe coherent backscattering of light that is unique to the anisotropic particle. This embodiment can be used for differentiating between the high-quality paper having particles of silica or the like applied on its surface and the plain paper including fibers such as cellulose, the high-quality paper and the plain paper being part of a recording medium that generates a small amount of specularly reflected light. That is to say, it becomes possible to observe coherent backscattering of light unique to the high-quality paper having particles of diameters that are relatively the same with one another and another coherent backscattering of light unique to the plain paper having the anisotropic particles, respectively. Since it has been difficult to identify such recording mediums by using the normal diffusely reflected light, the difference between the high-quality paper and the plain paper is used for differentiating between recording mediums generating a small amount of specularly reflected light. Coherent laser light is used as the light emitted from the light-emitting element for causing the coherent-backscattering phenomenon.
In
As has been described, the light-receiving elements 2, 3, and 5 detect the intensity of reflected light, the light having been emitted from the light-emitting element, for determining the type of a recording medium. More specifically, one of the light-receiving elements detects the intensity of coherent backscattering of light, which is reflected in a direction opposite to the direction in which light is made incident, that is, a backward direction. The other light-receiving elements detect the intensity of specularly reflected light and that of diffusely reflected light, respectively. Subsequently, the type of recording medium can be identified according to the detected values of the intensity of the specularly reflected light, the diffusely reflected light, and the coherent backscattering of light. Therefore, it becomes possible to identify the types of recording mediums with precision.
In this embodiment, the types of recording mediums are identified according to the intensity of three types of components, that is, a specularly-reflected-light component, a diffusely-reflected-light component, and a coherent-backscattering-of-light component. However, if the type of recording medium can be identified according to two types of light components, for example, the specularly-reflected-light component and the coherent-backscattering-of-light component, or the diffusely-reflected-light component and the coherent-backscattering-of-light component, the recording-medium identification device may be configured so as to detect the intensity of only two light components. Further, in the case where the type of recording medium can be identified according to the intensity of the coherent-backscattering-of-light component alone, the recording-medium identification device may be configured so as to detect the intensity of the coherent-backscattering-of-light component alone.
Further, in this embodiment, the types of the recording medium have been identified to include the OHP sheet, the plain-paper sheet, and the coated-paper sheet. However, the types of recording medium which may be identified are not limited to these three recording mediums. If the information of other types of recording mediums had already been stored in a recording device such as the memory 9, it becomes possible to identify various types of recording mediums.
A second embodiment of the present invention will now be described with reference to
A predetermined position on the surface of a recording medium 20 is determined to be an irradiation-reference position IRP. Then, a laser-light source 21 is provided in a predetermined position at a 180°-θ angle with respect to the irradiation-reference position (0°<θ<90°). A specularly-reflected-light-receiving element 22 is provided in a predetermined position at a θ angle with respect to the irradiation-reference position IRP. A half mirror 24 is provided on a predetermined position on an optical path between the laser-light source 21 and the irradiation-reference position IRP so as to reflect coherent backscattering of light from the irradiation-reference position IRP. Light emitted from the laser-light source 21 is made incident through the optical path. A light-receiving element 23 is provided in a predetermined position for receiving the coherent backscattering of light reflected by the half mirror 24 and other diffusely reflected light. These light-receiving elements (photo sensors) can be formed of various kinds of photo diodes such as a PIN-photo diode, an avalanche-photo diode, and so forth.
The light emitted from the laser-light source 21 reaches the recording medium 20 and is reflected and diffusely reflected according to the condition of the surface of the recording medium 20. In the case where a glossy recording medium such as an OHP sheet is used, a large amount of specularly reflected light can be observed while a small amount of diffusely reflected light is observed. However, in the case where a recording medium whose surface is coarse such as a sheet of plain paper is used, most of the light emitted from the laser-light source 21 is diffusely reflected and little of the light is specularly reflected. The diffusely reflected light and the reflected light are received by the specularly-reflected-light receiving element 22 and the coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23, respectively. The coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23 is installed in movable manner.
The coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23 is movable by using a motor or the like. When functioning as a coherent-backscattering-of-light-receiving element, the coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23 must receive light reflected by the half mirror 24 with reliability higher than that in the case where the coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23 functions as a diffusely-reflected-light-receiving element. Therefore, the reference position on which the coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23 is installed as shown by the solid line in
The memory 28 stores an output signal transmitted from the specularly-reflected-light-receiving element 22, the above-described two output signals transmitted from the coherent-backscattering-of-light-and-diffusely-reflected-light-receiving element 23, and a determination program. Therefore, a CPU 27 can identify the type of recording medium by using these three output signals from the three light-receiving elements by using the determination program, the program being used for comparing output signals that had already been obtained for various types of recording mediums to the output signals transmitted from the light-receiving elements.
Further, as shown in
Further, the laser-light source 21 may be movable. In this case, specularly reflected light and coherent backscattering of light are received by the specularly-reflected-light-receiving element 22 and the coherent-backscattering-of-light-and-diffusely-reflected-light receiving element 23, respectively, as shown in
According to the second embodiment, three types of light can be determined by using two light-receiving elements.
A recording-medium identification device according to a third embodiment of the present invention will now be described. In the first embodiment, the laser-light source 1 and the three light-receiving elements, that is, the specularly-reflected-light-receiving element 2, the coherent-backscattering-of-light-receiving element 3, and the diffusely-reflected-light-receiving element 5, are used. However, the recording-medium identification device of this third embodiment has only one laser-light source and only one light-receiving element. Since the laser-light source and the light-receiving element are movable, the light-receiving element can function as the above-described three types of light-receiving elements.
A predetermined position on the surface of a recording medium 30 is determined to be an irradiation-reference position. Then, a laser-light source 31 is provided in a predetermined position at a 180°-θ angle with respect to the irradiation-reference position IRP (0°<θ<90°). A specularly-reflected-light-receiving element 32 is provided in a predetermined position at a θ angle with respect to the irradiation-reference position IRP. A half mirror 33 is provided on a predetermined position on an optical path between the laser-light source 31 and the irradiation-reference position IRP so as to reflect coherent backscattering of light from the irradiation-reference position IRP. Incidentally, light emitted from the laser-light source 31 is made incident through the optical path. Light emitted from the laser-light source 31 for measuring specularly reflected light is reflected specularly at the irradiation-reference position IRP on the recording medium 30 and received by the specularly-reflected-light-receiving element 32. Then, the specularly-reflected-light-receiving element 32 is moved to a position where it functions as a diffusely-reflected-light-receiving element, as shown in
The light receiving element 32 can be moved by using a motor or the like. When functioning as a coherent-backscattering-of-light-receiving element, the light-receiving element 32 must receive light reflected by the half mirror 33 with reliability higher than that in the case where the light-receiving element 32 functions as the diffusely-reflected-light-receiving element, or as the specularly-reflected-light-receiving element. Therefore, the reference position on which the light-receiving element 32 is installed may preferably be determined to be the position on which the coherent-backscattering-of-light-receiving element is installed.
Further, the half mirror 33 and the light-receiving element 32 may be combined together, as shown in
Instead of installing a movable light-receiving element 32, the laser-light source 31 is movable. In this case, the laser-light source 31 emits light from a position suitable for measuring coherent backscattering of light, as shown in
According to the third embodiment, three types of light reflection can be measured by using one light-receiving element.
While the present invention has been described with reference to what are presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Number | Date | Country | Kind |
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2002-314605 | Oct 2002 | JP | national |
2003-352289 | Oct 2003 | JP | national |
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Number | Date | Country |
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8-188322 | Jul 1996 | JP |
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Number | Date | Country | |
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20040257942 A1 | Dec 2004 | US |