Source: https://patents.justia.com/patent/9267886
Timestamp: 2020-08-09 17:29:55
Document Index: 699017339

Matched Legal Cases: ['Application No. 2005', 'art 181', 'art 190', 'art 190', 'Application No. 2011', 'Application No. 2011']

US Patent for Optical sensor and image forming apparatus Patent (Patent # 9,267,886 issued February 23, 2016) - Justia Patents Search
Justia Patents US Patent for Optical sensor and image forming apparatus Patent (Patent # 9,267,886)
Nov 25, 2011 - RICOH COMPANY, LTD.
In a first method, as described in Japanese Laid-open Patent Application No. H10-160687, the reflected light amount is detected in a specular reflection direction of light on a surface of the recording medium, and the name or the like of the recording medium is specified based on the reflected light amount in the specular reflection direction.
However, Japanese Laid-open Patent Applications No. 2002-340518 and No. 2003-292170 disclose a contact method. Thus, there is a problem in which the surface of the recording paper or the like as the recording medium may become damaged. In Japanese Laid-open Patent Application No. 2005-156380, it is possible to determine the smoothness or the like of the recording medium but it is difficult to determine the thickness or the like of the recording medium.
In Japanese Laid-open Patent Applications No. H10-160687, No. 2006-062842, and No. H11-249353, it is possible to roughly determine the recording medium, but it is not possible to determine the thickness or the like of the recording medium in detail. In an apparatus for determining material of a sheet member disclosed in Japanese Laid-open Patent Application No. H10-160687 and apparatuses disclosed in Japanese Laid-open Patent Applications No. 2006-062842 and No. H11-249353, it is possible to identify (determine) only a non-coated paper, a coated paper, and an OHP sheet but it is not possible to specify the name of the recording medium for a high quality image formation.
FIG. 56A through FIG. 56C are diagrams for explaining a change of a detected light amount due to a displacement between a measurement plane and the surface of the recording paper in the eighth embodiment.
First, reflected light in a case of emitting light onto a recording medium such as a recording paper or the like will be described with reference to FIG. 1A, FIG. 1B, and FIG. 1C. In the case of emitting the light onto a recording paper 1 as the recording medium, it is possible to separate reflected light into light reflected from a surface of the recording paper 1 and light reflected inside the recording medium. Moreover, it is possible to separate the light reflected from the surface of the recording paper 1 into specular reflected light and diffuse reflected light. In the first embodiment, light specularly reflected from the surface of the recording paper 1 illustrated in FIG. 1A is described as a surface specular reflected light. Light diffusely reflected from the surface of the recording paper 1 is illustrated in FIG. 1B. In the first embodiment, a case of the recording medium being the recording paper 1 to which the light is illuminated will be described. Alternatively, the recording medium may be a resin film, a fabric, a skin, and the like. A similar measurement and the like may be performed.
On the other hand, in a case in which the recording medium is the recording paper 1, light reflected inside the recording paper 1 includes the diffuse reflected light alone due to a multiple reflection caused by fabric formed by the recording paper 1. The light diffusely reflected inside the recording paper 1 illustrated in FIG. 10 is described as internal diffuse reflected light.
Next, as illustrated in FIG. 5A and FIG. 5B, in a case of emitting light 12 in a perpendicular direction to the grain of the recording paper 1, that is, in a case in which the light path of the light 12 illuminated on the recording paper 1, an illuminated surface may be regarded as a slope portion on an irregular surface of the recording paper 1. Thus, the light 12 is diffusely reflected from the surface and the specular reflection hardly occurs. Thus, the light amount of a surface diffuse reflected light 12a is increased. In this case, also, as the diffuse reflected light, the internal diffuse reflected light 12b, which is diffusely reflected inside the recording paper 1, occurs but the light amount is less. Thus, the reflected light of the light 12 is almost the surface diffuse reflected light 12a. FIG. 5A is a perspective diagram illustrating a state in which the reflected light of the light 12 illuminating the recording paper is mostly the surface diffuse reflected light 12a. FIG. 5B is a cross-sectional diagram illustrating a surface perpendicular to the grain of the recording paper 1. That is, in FIG. 5B, a cross-sectional surface in an XZ plane is illustrated.
A high accurate detection method of the internal diffuse reflected light will be described. In order to detect the internal diffuse reflected light at higher accuracy, first, it is required to exclude a component of the surface specular reflected light in a detection direction at least. However, it is difficult to completely exclude light other than light of the linear polarization in one direction alone in an actual irradiation system. That is, it is difficult to leave light of the linear polarization in a first polarization direction alone. The reflected light on the surface of the recording paper 1 includes a component in a second polarization direction perpendicular to the first polarization direction.
In detail, in a case in which a photodetector is arranged at a location where the surface specular reflected light is detected and the light amount of the component of the light in the second polarization direction by using an optical filter, if the component of the light in the second polarization direction is included in the light emitted on the recording paper 1, this component is also detected by the photodetector. Thus, the light amount of the internal diffuse reflected light may not be precisely detected. In this case, since the light amount of the internal diffuse reflected light is generally smaller, the light amount of the component of the light in the second polarization direction included in the light emitted onto the recording paper 1 may be greater than that of the internal diffuse reflected light. Also, it may be possible to make the light emitted onto the recording paper 1 be a perfect light in the first polarization direction. In this case, it is required to use a polarization filter having a higher extinction ratio. Thus, this configuration costs more.
FIG. 8 illustrates a change of the contrast ratio with respect to the total light amounts in a case of changing the number of the light emitting elements while each light amount of the light emitting elements is fixed (for example, 1.66 mW) and in a case of changing the light amount for each of the light emitting elements while the number of the light emitting elements is fixed to 30 elements.
FIG. 10 illustrates an effective light intensity distribution in a case of changing the driving current at high speed. The light intensity distribution is the same as an average value of the light intensity distribution in multiple driving currents illustrated in FIG. 9. Thus, it is confirmed that a change of the light intensity is suppressed. The contrast ratio of the speckle pattern in the case of changing the driving current indicates 0.72, and the contrast ratio of the speckle pattern in the case of fixing the driving current indicates 0.96. Thus, the contrast ratio in the former case is suppressed to be lower than that in the latter case.
The first measurement system 110 and the second measurement system 120 are covered with a dark box 180. An opening part 181 is provided to the dark box 180 to illuminate light onto the surface of a recording paper 100. The first measurement system 110 and the second measurement system 120 are enclosed by the dark box 180 and the recording paper 100. External light and the like do not entered from the outside. Thus, it is possible to perform a precise measurement. Also, the first light emission system 111, the first specular reflected light detection system 112, the first diffuse reflected light detection system 113, the second light emission system 121, the second specular reflected light detection system 122, and the second diffuse reflected light detection system 123 are connected to a control part 190.
Also, in the first embodiment, the first measurement system 110 and the second measurement system 120 are arranged so that an angle, which is formed by a light path of light emitted from the first light emission system 111 and another light path of light emitted from the second light emission system 121, becomes 150° on a XY plane. That is, an angle, which is formed by a component parallel to the recording paper 100 in the light emitted from the first light emission system 111 and another component parallel to the recording paper 100 in the light emitted from the second light emission system 121, becomes 150° on the XY plane. It is preferable for this angle to be more than 90° and less than 180°. In a case in which the angle is more than 90° and less than 180°, the light emitted from the second light emission system 121 includes a component emitted from an opposite direction as illustrated in FIG. 6 with respect to the light emitted from the first light emission system 111. Therefore, it is possible to identify the recording medium at higher accuracy. Also, in the first embodiment, “emitting light on the XY plane” indicates a state of projection on the XY plane.
The first light emission system 111 includes a light source 114, a collimating lens 115, and the like. A configuration of the second light emission system 121 is the same as the configuration of the first light emission system 111. The first light emission system 111 is arranged at a location where the light enters at an angle θ1 with respect to the normal line of the recording paper 100. The second light emission system 121 is arranged at a location where the light enters at an angle θ2 with respect to the normal line of the recording paper 100. In the first embodiment, the angle θ1 and the angle θ2 are the same and approximately 80°. The angle θ1 is regarded as an angle formed by a direction of the light emitted from the first light emission system 111 to the recording paper 100 and the normal line of the surface of the recording paper 100. The angle θ2 is regarded as an angle formed by a direction of the light emitted from the second light emission system 121 to the recording paper 100 and the normal line of the surface of the recording paper 100.
The first diffuse reflected light detection system 113 is used to detect the surface diffuse reflected light and the internal diffuse reflected light in the light emitted from the first light emission system 111 to the recording paper 100, and includes a photodetector 117 formed by a light receiving element such as a photo diode or the like. A polarizing filter 118 is provided in front of the photodetector 117. The second diffuse reflected light detection system 123 is used to detect the surface diffuse reflected light and the internal diffuse reflected light in the light emitted from the second light emission system 121 to the recording paper 100, and includes a photodetector 127 formed by a light receiving element such as a photo diode or the like. A polarizing filter 128 is provided in front of the photodetector 127.
The first light emission system 111 and the second light emission system 121 are formed so that light of a S-polarization is emitted to the recording paper 100. In a case of using a non-polarized light source of a LED (Light Emitting Diode), white light, or the like as the light source 114 and the like, a polarizing filter is arranged for the light emitted from the light source 114 and the like to be light of the S-polarization. The light emitted from the light source 114 and the like is needed to be the light of the S-polarization, by passing through the polarizing filter. Also, light is emitted from the first light emission system 111 at the angle θ1, and light is emitted from the second light emission system 121 at the angle θ2. The angle θ1 and the angle θ2 are 80°. However, greater angles related to the angle θ1 and the angle θ2 of respective incident light are preferable to specify the type or the like of the recording paper 100.
When the light enters an interface of a medium, a surface including an irradiated light and the normal line of the interface at an incident point is called an “incident surface”. In a case in which the irradiation light is formed by multiple light beams such as the surface emitting laser array 200 (VCSEL array) including the nine light emitting elements 201 illustrated in FIG. 13, the incident surface may exist for each light beam. However, in the first embodiment, the incident surface of the light emitted from the light emitting element 201 arranged in a center of the surface emitting laser array 200 (VCSEL array) is represented as the incident surface to the recording paper 100.
The first diffuse reflected light detection system 113 is used to detect the diffuse reflected light in the light emitted from the first light emission system 111, and is arranged in a direction in which an angle ψ1 indicates 90° with respect to the surface of the recording paper 100 at the illumination center. The second diffuse reflected light detection system 123 is used to detect the diffuse reflected light in the light emitted from the second light emission system 121, and is arranged in a direction in which an angle ψ2 indicates 90° with respect to the surface of the recording paper 100 at the illumination center. The angles ψ1 and ψ2 may be 90° preferably. Since each of the first diffuse reflected light detection system 113 and the second diffuse reflected light detection system 123 includes a predetermined size, location thereof may be cause of interference with each other. Accordingly, it is preferable in that the first diffuse reflected light detection system 113 and the second diffuse reflected light detection system 123 are arranged at angles not to mutually interfere, the angles close to 90° as possible, that is, approximately 90°.
The polarizing filter 118 provided in the first diffuse reflected light detection system 113 passes light of the P-polarization and shields light of the S-polarization. The polarizing filter 128 provided in the second diffuse reflected light detection system 123 also passes light of the P-polarization and shields light of the S-polarization. Instead of using the polarizing filter 118 and polarizing filter 128, a polarizing beam splitter having an equivalent function may be used. The first diffuse reflected light detection system 113 and the second diffuse reflected light detection system 123 are arranged at positions of the same distance from the illumination center so that angles ψ1 and ψ2 are approximately the same angles.
In addition, the photodetector 116 of the first specular reflected light detection system 112, the photodetector 117 of the first diffuse reflected light detection system 113, the photodetector 126 of the second specular reflected light detection system 122, and the photodetector 127 of the second diffuse reflected light detection system 123 output electronic signals (photoelectric conversion signals), respectively. In the first embodiment, in a case of emitting the light from the first light emission system 111 onto the recording paper 100, a signal level of an output signal of the photodetector 116 of the first specular reflected light detection system 112 is denoted by “S11”, and a signal level of an output signal of the photodetector 117 of the first diffuse reflected light detection system 113 is denoted by “S12”. Similarly, in a case of emitting the light from the second light emission system 121, a signal level of an output signal of the photodetector 126 of the second specular reflected light detection system 122 is denoted by “S21”, and a signal level of an output signal of the photodetector 127 of the second diffuse reflected light detection system 123 is denoted by “S22”.
In a case of printing the recording paper 100 by the image forming apparatus, the signal levels S11, S12, S21, and S22 are measured by the optical sensor 1001 in the first embodiment. Based on the signal levels 511, S12, S21, and S22, the name, the smoothness, the thickness, and the density related to the type of the recording paper 100 are determined by referring to the recording paper determination table. This determination is performed by an adjustment device, or the control part 190 in the image forming apparatus.
In a case illustrated in FIG. 15, if a location based on the signal levels S11 and S12 detected by the first measurement system 110 for the recording paper 100 indicates a point 301, the point 301 is included in both a range 311 (regarded as an output range by the signal levels S11 and S12 of a name A) and a range 321 (regarded as an output range by the signal levels S11 and S12 of a name B). The recording paper 100 may be the name A or the name B. However, it is not possible to specify which name A or B is that of the recording paper 100. If a location based on the signal levels S21 and 522 detected by the second measurement system 120 for the recording paper 100 indicates a point 302, the point 302 exists in a range 312 (regarded as an output range by the signal levels S21 and S22 of the name A) but does not exist in a range 322 (regarded as an output range by the signal levels S21 and S22 of the name B). Accordingly, it is possible to determine the recording paper 100 as the name A.
In general, fabric taken from pulp is streamed in one direction in a production apparatus and the recording paper 100 is produced. By streaming in one direction in the production apparatus, the fabric forming the recording paper 100 is aligned toward a streaming direction. Accordingly, a streaming direction of the recording paper 100 becomes the orientation direction of the fabric. As described above, the irregular surface is formed by oriented fabric. In general, a paper is cut in a parallel direction and in a perpendicular direction to the stream of the fabric, thereby multiple recording papers 100 are produced in a predetermined size in the production stage.
Moreover, a third measurement system is formed by a third light emission system 131, a third specular reflected light detection system 132, and a third diffuse reflected light detection system 133. The third measurement system is arranged so that the light path of the light emitted from the first light emission system 111 forms an angle of 180° on the XY plane with the light path of light emitted from the third light emission system 131. That is, the third measurement system is arranged so that an angle between the component of the light emitted from the first light emission system 111 in which the component is parallel to the recording paper 100 and a component of the light emitted from the third light emission system 131 in which the component is parallel to the recording paper 100 is formed to be 180°.
The third light emission system 131 and the fourth light emission system 141 are equivalent to the first light emission system 111. The third specular reflected light detection system 132 and the fourth specular reflected light detection system 142 are equivalent to the first specular reflected light detection system 112. The third diffuse reflected light detection system 133 and the fourth diffuse reflected light detection system 143 are equivalent to the first diffuse reflected light detection system 113.
In the fourth embodiment, the first light emission system 111 interferes with the third specular reflected light detection system 132 in their locations. The second light emission system 121 interferes with the fourth specular reflected light detection system 142 in their locations. The third light emission system 131 interferes with the first specular reflected light detection system 112 in their locations. The fourth light emission system 141 interferes with the second specular reflected light detection system 122 in their locations. In order to prevent location interference, a distances from the first light emission system 111 to its illumination center is set to be a different distance from the third specular reflected light detection system 132 to its illumination center. Alternatively, the light emitted from the first light emission system 111 is reflected by a mirror or the like to illuminate its illumination center. The similar manner is applied to other location interferences.
Configurations other than the above described configuration in the fifth embodiment are the same as the configurations in the first embodiment and the second embodiment, and the explanation thereof will be omitted.
The printer control device 2090 includes a CPU (Central Processing Unit), a ROM (Read-Only Memory), a RAM (Random Access Memory), and an A/D converter, and the like. The ROM stores a program described in code interpretable by the CPU and various data used to execute the program. The RAM is regarded as a memory used as a working area. The A/D convertor converts analog data into digital data. Thus, the printer control device 2090 controls each of component parts in response to a request sent from the upper apparatus 701, and sends image information sent from the upper apparatus 701 to the optical scanner 2010.
The fixing device 2050 applies heat and pressure to the recording paper 100. Then, the toner is fixed on the recording paper 100. The recording paper 100 is carried to the ejection tray 2070 through the pair of paper ejection rollers 2058, and is stacked on the ejection tray 2070.
Also, FIG. 29C illustrates a case in which the surface of the recording paper 100 is displaced by d in height with respect to the measurement plane 9a, that is, a case the surface of the recording paper 100 is displaced in a Z-axis direction. In this case, if the light emitting system 101 and the specular reflection detection system 102 are arranged similar to an arrangement in FIG. 29A, the light path of the specular reflected light is displaced by 2 d×sin θ. Accordingly, for the light path of the specular reflected light from the recording paper 100, the specular reflected light detection system 102 detects the light at a location displaced by 2 d×sin θ. As a result, the light amount detected by the specular reflected light detection system 102 is changed. Thus, it may be difficult to identify the recording paper 100 in detail.
Also, by using the photo diodes being arrayed to the light receiving part of the specular reflected light detection system 102, for a displacement of the light path of the specular reflected light, the light receiving area may be formed to be sufficiently large. In this case, even if the light of the specular reflected light is displaced, the greatest light signal may be regarded as a signal of the specular reflected light in light signals detected by each of the photo diodes. Also, in a case of arraying the photo diodes, it is possible to form the light receiving area to be smaller for each of the photo diodes. Thus, it is possible to reduce fluctuation of an output due to a displacement between the specular reflected light and the center of the light receiving area, and it is possible to realize a further precise detection.
In FIG. 30, the color printer 2000a may be a multicolor printer of a tandem system to form a full-color image by overlapping four colors (black, cyan, magenta, and yellow). The color printer 2000a includes an optical scanner 2010, four photosensitive drums 2030a, 2030b, 2030c, and 2030d, four cleaning units 2031a, 2031b, 2031c, and 2031d, four charging devices 2032a, 2032b, 2032c, and 2032d, four developing rollers 2033a, 2033b, 2033c, and 2033d, four toner cartridges 2034a, 2034b, 2034c, and 2034d, a transfer belt 2040, a transfer roller 2042, a fixing device 2050, a feeding roller 2054, a pair of registration rollers 2056, a pair of paper ejection rollers 2058, a paper feed tray 2060, an ejection tray 2070, a communication control device 2080, an optical sensor 2245, and a printer control device 2090.
The toner cartridge 2034a stores black toner, and the black toner is supplied to the developing roller 2033a. The toner cartridge 2034b stores cyan toner, and the cyan toner is supplied to the developing roller 2033b. The toner cartridge 2034c stores magenta toner, and the magenta toner is supplied to the developing roller 2033c. The toner cartridge 2034d stores yellow toner, and the yellow toner is supplied to the developing roller 2033d.
The paper feed tray 2060 stores a plurality of the recording papers 100. In vicinity of the paper feed tray 2060, the feeding roller 2054 is arranged. The feeding roller 2054 picks out each of the recording papers 100 one by one to convey to the pair of the registration rollers 2056. The pair of the registration rollers 2056 sends out a recording paper 1 toward a gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. By this configuration, a color image formed on the transfer belt 2040 is transferred to the recording paper 1. The recording paper 1, on which the color image is transferred, is carried to the fixing device 2050.
The cleaning unit 2031a removes residual toner on the surface of the photosensitive drum 2030a. After the residual toner is removed, the surface of the photosensitive drum 2030a returns a position facing the charging device 2032a. The cleaning units 2031b, 2031c, and 2031d operate similar to the cleaning unit 2031a.
Each of the light receiver 13 and the light receiver 15 outputs an electronic signal (photoelectric transfer signal) corresponding to a received light amount to the printer control device 2090. In the following, in a case of emitting the light flux from the light source 11 to the recording paper 1, a signal level in an output signal of the light receiver 13 is called “S1”, and a signal level in an output signal of the light receiver 15 is called “S2”.
FIG. 39 illustrates a change of the contrast ratio with respect to the total light amounts in a case of changing the number of the light emitting elements 6a while each light amount of the light emitting elements 6a is fixed (for example, 1.66 mW) and in a case of changing the light amount for each of the light emitting elements 6a while the number of the light emitting elements 6a is fixed to 30 elements.
FIG. 41 illustrates an effective light intensity distribution in a case of changing the driving current at high speed. The light intensity distribution is the same as an average value of the light intensity distribution in multiple driving currents illustrated in FIG. 40. Thus, it is confirmed that a change of the light intensity is suppressed. The contrast ratio of the speckle pattern in the case of changing the driving current indicates 0.72, and the contrast ratio of the speckle pattern in the case of fixing the driving current indicates 0.96. Thus, the contrast ratio in the former case is suppressed to be lower than that in the latter case.
In the eighth embodiment, the light source 11 of the optical sensor 2245 includes the surface emitting laser array 5a in which nine light emitting elements 6a are arrayed in two dimensions. The CPU of the printer control device 2090 supplies the driving current of the triangular waveform to the surface emitting laser array 5a. By this configuration, the speckle pattern is suppressed. It is possible to detect an accurate reflected light amount. Accordingly, it is possible to improve precision of identifying the recording paper 1. That is, it is regarded that the speckle pattern is suppressed by temporally changing the wavelength of the emitted light.
For a sensor to detect the surface state of a print sheet based on the reflected light amount, it is preferable to use the semiconductor laser as the light source 11, in order to improve the S/N. In this case, the speckle pattern is caused, when the light flux is emitted onto a rough surface such as the surface of the print sheet. The speckle pattern is different depending on a portion illuminated by the light flux. Dispersion of detection by the light receivers 13 and 15 is caused and accuracy is degraded. Accordingly, in general, the LED or the like has been conventionally used.
Accordingly, in the eighth embodiment, by increasing the emitted light amount, the higher optical resolution is acquired. In detail, as described above, since the light amount of the internal diffuse reflected light is decreased at approximately 30% substantial to the diffuse reflected light (A+B+C), the light amount of the irradiated light is required to be 3.3 times more than the related art. Moreover, since a paper determination is performed in detail five times more than the related art, the light amount, which is 3.3×5 times more than that in the related art, needed to emit. As described above, proportional to specifying more types of the recording papers 1, the light amount to emit is needed to be increased. In the eighth embodiment, in a case in which a non-polarized light source such as a LED is used to emit the S-polarization, light is needed to pass the polarizing filter to be the linear polarization (S-polarization) before the light is emitted. In this case, the cheaper polarizing filter as described above may be used. The light amount to emit onto the recording paper 1 becomes approximately 40% (=50% (cut portion of the P-polarization)×80% (decreased portion by the polarizing filter)) of the light amount emitted from the LED. Accordingly, in a case of a LED light source, the light amount to emit, which is 40 (=3.3×5/0.4) times greater than the related art, is needed. However, the light amount emitted from a cheaper LED may be approximately a few mW (1 mW as representative value). It is difficult to assure the light amount greater than 40 mW to 50 mw to emit. On the contrary, in the surface emitting laser array 5a, the multiple light emitting elements 6a are simultaneously lighted. Thus, it is possible to easily assure a desired light amount to emit. Accordingly, in the surface emitting laser array 5a, it is possible to assure the light amount for specifying the types of the recording papers 1 more than the related art.
Moreover, FIG. 45 illustrates the light intensity distribution in the light source including the surface emitting laser array in which the five light emitting elements are arrayed in one dimension and the light emitting elements are irregularly arranged with a ratio of 1.0:1.9:1.3:0.7, the light intensity distribution, which is acquired by observing the speckle pattern with a beam profiler. In this case, the periodical fluctuation of the light intensity distribution is suppressed. In this case, the contrast ratio indicates 0.56, and is reduced more than the case of arranging the light emitting elements with an equal interval.
(2) Values of the signal levels S1, S2, and S4 are acquired from output signals of the light receivers 13, 15, and 19.
(4) By referring to the recording paper determination table, the name of the recording paper 1 is specified based on the acquired values of the signal levels S4 or S1 and S2 (refer to FIG. 52).
FIG. 53A illustrates an investigation result related to influence of the disturbing light in a case of specifying the paper type by using only the signal levels S1 and S2. FIG. 53B illustrates an investigation result related to influence of the disturbing light in a case of specifying the paper type by using the signal level S4 or S1 and the signal level S3 or S2. Apparent from FIG. 53A and FIG. 53B, if there is the disturbing light, values respectively detected by the light receiving systems become greater. In the case of specifying the type of the recording paper 1 by using only the signal levels S1 and S2, the type may be erroneously specified. On the other hand, in the case of specifying the paper type by using the signal level S4 or S1 and the signal level S3 or S2, even if there is the disturbing light, the signal level S4 or S1 and the signal level S3 or S2 hardly change from a state in which there is no the disturbing light. Therefore, it is possible to specify a proper type of the recording paper 1.
For example, in a case in which the third light detection system may include two light receivers and the fourth light detection system may include two pairs of a polarizing filter and a light receiver, output levels of the light receivers are denoted by signal levels “S3” and “S5” in the third light detection system, and output levels of the light receivers are denoted by signal levels “S4” and “S6” in the fourth light detection system. A value calculated as (S4/S1+S6/S1) and a value calculated as (S3/S2+S5/S2) may be used, and the paper type may be specified. Also, a value of S4/S1, a value of S6/S1, a value of S3/S2, and a value of S5/S2 may be used, and the paper type may be specified.
It is important to reproduce a measurement for the optical sensor 2245 used to identify the recording paper 1 based on the reflected light amount. For the optical sensor 2245 used to identify the recording paper 1 based on the reflected light amount, a measurement system is arranged in a condition in which a measurement plane and the surface of the recording paper 1 are on the same plane when a measurement is performed. However, the surface of the recording paper 1 is inclined or lifted due to arcuation, vibration, and the like. Thus, the surface of the recording paper 1 may not be on the same plane as the measurement plane. In this case, the reflected light amount is changed, and a stable detailed determination is difficult to be performed. In the following, as an example, the specular reflected light will be described.
FIG. 56B illustrates a case in which the surface of the recording paper 1 is inclined at an angle α with respect to the measurement plane 9a. In this case, if the location relationship between a light emission system and the light detection system 315 is the same as that in the case illustrated in FIG. 56A, the light detection system 315 receives light in a direction displaced at an angle 2α from a specular reflection direction. The reflected light intensity distribution moves along the displacement. If the distance from a center location of the irradiation area to the light detection system 315 is denoted by L, the light detection system 315 receives light at a position displaced at an angle L×tan 2α. Also, an actual incident angle is displaced at the angle α from the incident angle θ with respected the perpendicular line 9b. The angle θ is regulated. A reflectance from the recording paper 1 is varied. A change of the detected light amount is caused. As a result, it becomes difficult to identify the recording paper 1 in detail.
Moreover, FIG. 56C illustrates a case in which the surface of the recording paper 1 is displaced by distance d in height with respective to the measurement plane 9a, that is, a case in that the surface of the recording paper 1 is displaced in the Z-axis direction. In this case, if the location relationship between the light emission system and the light detection system 315 is the same as that in the case illustrated in FIG. 56A, since the reflected light intensity distribution moves along a displacement, the light detection system 315 receives light at a position displaced at an angle 2 d×sin θ from a specular reflected light position. A change of the detected light amount is caused. As a result, it becomes difficult to identify the recording paper 1 in detail.
In cases illustrated in FIG. 56B and FIG. 56C, the condensing lens is arranged in front of the light detection system 315 with respect to a movement amount so as to certainly detect the specular reflected light. It is possible to correspond to a case in which the reflected light intensity distribution moves, by condensing the light fluxes.
Alternatively, by using a sufficiently large sized photo diode (PD) which is the light receiving area for the light receivers 13, 15, 17, 19, and the like, by narrowing a beam diameter for the irradiated light, it is possible to overcome a problem in which the surface of the recording paper 1 and the measurement plane are on the same plane.
a first light detection system configured to include a first light detector arranged on a first light path of a specular reflected light, which is emitted from the light emission system and is specularly reflected from the target object;
a second light detection system configured to include a second light detector arranged on a second light path of a diffuse reflected light which is diffusely reflected from an incident plane on the target object, the second light detector receiving second light passed by an optical element which passes a linear polarization component of a second polarization direction perpendicular to the first polarization direction;
a third light detection system configured to include at least one third light detector arranged on a third light path of a diffuse reflected light which is diffusely reflected from the incident plane on the target object without passing the optical element,
wherein the second light detection system and the third light detection system are arranged on paths different from the first light path of the specular reflected light which is emitted from the light emission system and is specularly reflected from the target object.
2. The optical sensor as claimed in claim 1, wherein the optical element and the second light detector are arranged on the second light path of the diffuse reflected light which is diffusely reflected in a normal direction of the surface of the target object.
a processing part configured to specify the target object based on a ratio of a third output of the third light detector of the third light detection system and the first output of the first light detection system, and the second output of the second light detector.
a processing part configured to specify the target object based on a ratio of a third output of the third light detector of the third light detection system and the second output of the second light detector, and the first output of the first light detector.
a fourth light detection system configured to include a fourth light detector arranged on a fourth light path of the diffuse reflected light which is diffusely reflected from the incident plane on the target object, the fourth light detector receiving fourth light passed by a second optical element which passes the linear polarization of the second polarization direction perpendicular to the first polarization direction; and
a processing part configured to specify the target object based on a ratio of a third output of the third light detector of the third light detection system and the first output of the first light detector, and a ratio of a fourth output of the fourth light detector of the fourth light detection system and the second output of the second light detector.
7. The optical sensor as claimed in claim 1, further comprising a mechanism configured to temporally change a waveform of a secondary light, wherein the secondary light is light emitted from a semiconductor laser.
8. An image forming apparatus for forming an image on the recording medium, comprising: the optical sensor as claimed in claim 1.
multiple measurement systems including a first measurement system and a second measurement system, each of the first measurement system and second measurement system being configured to include a light emission system configured to emit polarized light of a linear polarization in a first polarization direction to a recording medium; a specular reflected light detection system configured to detect specular reflected light which is specularly reflected from the recording medium, based on the polarized light emitted from the light emission system; and a diffuse reflected light detection system configured to include an optical device for passing another polarized light in a second polarization direction perpendicular to the first polarization direction, to detect diffuse reflected light which is diffusely reflected from the recording medium, based on the polarized light emitted from the light emission system,
wherein the light emitted by the light emission system of the first measurement system to the recording medium and the light emitted by the light emission system of the second measurement system are directed in different respective directions to respective incident planes that are different from each other.
10. The optical sensor as claimed in claim 9, wherein illumination centers of the polarized light emitted from light emission systems of the multiple measurement systems are approximately the same location.
11. The optical sensor as claimed in claim 9, wherein incident angles of the polarized light emitted from the light emission systems of the multiple measurement systems are approximately the same on the recording medium,
first angles, which are formed by a surface of the recording medium and first straight lines connecting between the illumination centers of the polarized light and a plurality of specular reflected light detection systems, are approximately the same, and
second angles, which are formed by the surface of the recording medium and second straight lines connecting between the illumination centers of the polarized light and the multiple diffuse reflected light detection systems, are approximately at a right angle.
12. The optical sensor as claimed in claim 9, wherein a shape of the recording medium is square or rectangle, and
in at least one system of light emission systems of the multiple measurement systems, a light path of the polarized light emitted from the system exists on a plane parallel to one side of the recording medium.
13. The optical sensor as claimed in claim 9, further comprising a control part configured to control a light source for each of light emission systems of the multiple measurement systems so as not to overlap emission time of the polarized light in the multiple light emission systems.
14. The optical sensor as claimed in claim 9, wherein each of light emission systems of the multiple measurement systems is configured to include a surface emitting laser array including light emitting elements.
15. The optical sensor as claimed in claim 14, wherein light emitting elements of the multiple measurement systems are arrayed in two dimensions.
16. The optical sensor as claimed in claim 14, wherein light emitting elements of the multiple measurement systems are arranged so that at least one of intervals among light emitting elements in one direction is different from other intervals.
17. An image forming apparatus for forming an image on the recording medium, comprising: the optical sensor as claimed in claim 9.
18. The image forming apparatus as claimed in claim 17, further comprising a table configured to define a relationship between a first output range from the specular reflected light detection system and a second output range from the diffuse reflected light detection system on the recording medium for each of multiple of recording media,
wherein based on outputs from the specular reflected light detection system and the diffuse reflected light detection system, each of names of the multiple of the recording media is specified.
19. An optical sensor, comprising:
multiple light emission systems including a first light emission system and a second light emission system, each of the first light emission system and second light emission system being configured to emit polarized light of a linear polarization in a first polarization direction to a recording medium;
multiple specular reflected light detection systems each configured to detect specular reflected light which is specularly reflected from the recording medium, based on the polarized light emitted from a respective light emission system in the multiple light emission systems; and
a diffuse reflected light detection system configured to include an optical device for passing other polarized light in a second polarization direction perpendicular to the first polarization direction, to detect diffuse reflected light which is diffusely reflected from the recording medium, based on the polarized light emitted from the respective light emission system,
wherein the light emitted by the first light emission system to the recording medium and the light emitted by the second light emission system are directed in different respective directions to respective incident planes that are different from each other.
20. The optical sensor as claimed in claim 1, wherein the second detection system is arranged at a normal direction of the surface of the target object nearer than the third detection system.
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Patent Publication Number: 20130194573
Application Number: 13/879,451
Current U.S. Class: 139/273.0A
International Classification: G01J 4/00 (20060101); H04L 12/28 (20060101); G02B 26/10 (20060101); B60Q 1/26 (20060101); F21V 1/00 (20060101); H01J 3/14 (20060101); G01J 1/42 (20060101); G01N 21/55 (20140101); G01N 21/47 (20060101); G01B 11/06 (20060101); G01N 21/21 (20060101); G01N 21/57 (20060101); G03G 15/00 (20060101);