JP2014178298A - Reflective optical sensor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective optical sensor which effectively prevents the reduction of a detection area due to fluttering of a surface of an object.SOLUTION: A reflective optical sensor 200a includes: an irradiation optical system formed by arranging at least two unit irradiation optical systems including two or more irradiation system LEDs and irradiation lenses; and a light-receiving optical system including at least two light-receiving unit PDs 212a and light-receiving lenses. The light emitted from a light-emitting unit is guided to a surface of an object, to form an irradiation light spot shifted in one direction. A light-receiving system includes the light-receiving unit, and is configured to receive the light irradiated on the surface by the unit irradiation optical systems and reflected via the light-receiving lens 220aC. A positional relation between the light-emitting unit and the irradiation lens is adjusted so that the spots emitted from each of all the light-emitting units and irradiated on the surface are continuously arranged in one direction and some spots are irradiated at different incident angles from adjacent unit irradiation optical systems.

Description

  The present invention relates to a reflective optical sensor and an image forming apparatus.

  The image forming apparatus can be implemented as an analog or digital electronic copying machine, an optical printer, a facsimile machine, or an optical plotter.

  Alternatively, it can be implemented as an MFP (multi-function printer) that combines the functions of these devices.

  Detecting surface information about the state of an object surface has important significance in various technologies.

  For example, as in a digital copying apparatus, an “image forming apparatus that forms a toner image by an electrophotographic process and fixes the toner image on a sheet-like recording medium by a fixing device” is known.

  In such a case, if there is an abnormality such as a “scratch” on the surface of the fixing belt or fixing roller included in the fixing device, the fixing of the toner image is hindered and the image quality of the formed image is deteriorated.

  For this reason, it is important to detect “scratches” on the surface of the fixing belt or the like as surface information.

  As a method for detecting surface information, there is known a method of irradiating light on a surface, receiving reflected light from the surface, and detecting “the presence / absence of scratches”, “surface degradation”, etc. from the amount of received light (Patent Document) 1).

  There has been proposed a reflection type optical sensor having a combination of an illumination unit in which a plurality of light emitting units are arranged and a light receiving system in which a plurality of light receiving units are arranged (Patent Document 2).

  The reflection type optical sensor described in Patent Document 2 describes a case where it is used for detection of toner density and position of a toner pattern formed on a transfer belt.

  However, a reflective optical sensor having a combination of an illuminating unit in which a plurality of light emitting units are arranged and a light receiving system in which a plurality of light receiving units are arranged can also be used for detecting surface information on a fixing belt or the like.

  When detecting surface information of an object such as a fixing belt using such a reflective optical sensor, the following factors can be considered as factors affecting detection accuracy.

  First, detecting the surface information of the fixing belt is generally performed while the fixing belt is in operation, and the fixing belt is not stationary at the time of detection.

  For this reason, there is a phenomenon in which the surface of the fixing belt from which surface information is to be detected tilts in a swinging manner with respect to the arrangement direction of the light emitting units and the light receiving units.

  This phenomenon is hereinafter referred to as “belt surface flapping” or “flapping”.

  Second, it is conceivable that the positional relationship of the reflective optical sensor with respect to the surface of the fixing belt deviates from an appropriate relationship due to attachment errors and changes with time.

  If there is the above “flapping” or “positional deviation”, the parallelism with the arrangement direction of the light emitting unit and the light receiving unit of the reflection type optical sensor is distorted.

  If there is such a deviation in parallelism, among the light receiving units arranged in one direction, the light receiving unit near the end in the arrangement direction may not be able to properly receive the reflected light from the belt surface.

  Thus, if there is a light receiving portion that cannot properly receive the reflected light from the belt surface, data necessary for detecting the surface information is lost.

  This data loss causes a narrow detection area in which surface information can be detected, making it difficult to detect surface information properly.

  This invention makes it a subject to implement | achieve the reflection type optical sensor which can reduce effectively the narrowing of the detection area resulting from the said flutter and the shift | offset | difference of positional relationship in view of the situation mentioned above.

  The reflection type optical sensor of the present invention is a reflection type optical sensor for irradiating the surface of an object to be detected, receiving light reflected by the surface and detecting surface information of the surface. And a light receiving optical system including a light receiving system and a light receiving lens, and the irradiation system of the unit irradiation optical system emits two or more lights. And the irradiation lens of the unit irradiation optical system is shared by the two or more light emitting units, and guides and emits light emitted from the two or more light emitting units to the surface of the test object. The light spot is formed by shifting in one direction, the light receiving system of the light receiving optical system has two or more light receiving parts, and the light receiving lens is shared by the two or more light receiving parts, The surface of the specimen is irradiated by each unit irradiation optical system of the irradiation optical system. The reflected light reflected by the surface is configured to be received by the light receiving system via the light receiving lens of the light receiving optical system, and is emitted from each of the light emitting units and applied to the surface. The light emitting section in the irradiation optical system, such that there are spots that are continuously arranged in one direction, and among these spots, there are those irradiated from different unit irradiation optical systems at different incident angles, The positional relationship of the irradiation lens is adjusted.

  According to the present invention, it is possible to realize a reflective optical sensor that can effectively reduce the narrowing of the detection region caused by the flickering of the test object and the positional relationship with the test object.

It is a figure for demonstrating a color printer. FIG. 6 is a diagram for explaining detection of surface information of a fixing belt. It is a figure for demonstrating a reflection type optical sensor notionally. It is a figure for demonstrating the arrangement | sequence relationship of a light emission part and a light-receiving part. It is a figure which shows the state which looked at the structure of the reflective optical sensor of FIG. 3 from the y direction. It is a flowchart showing the detection of the surface information by the reflective optical sensor of FIG. It is a figure for demonstrating the output of a reflection type optical sensor. It is a figure for demonstrating the relationship between the light emission part, light-receiving part, and opening part of a reflection type optical sensor. It is a figure for demonstrating the opening part of a reflection type optical sensor. It is a figure for demonstrating Embodiment 1 of a reflection type optical sensor. It is a figure for demonstrating Embodiment 1 of a reflection type optical sensor. It is a figure for demonstrating Embodiment 1 of a reflection type optical sensor. It is a figure for demonstrating the effect of Embodiment 1 of a reflection type optical sensor. It is a figure for demonstrating Embodiment 2 of a reflection type optical sensor. It is a figure for demonstrating Embodiment 4 of a reflection type optical sensor. It is a figure for demonstrating the effect of Embodiment 4 of a reflection type optical sensor. It is a figure for demonstrating Embodiment 5 of a reflection type optical sensor. It is a figure for demonstrating other embodiment of a reflective optical sensor. It is a figure for demonstrating other embodiment of a reflection type optical sensor. It is a figure for demonstrating other embodiment of a reflection type optical sensor.

  Prior to the description of the embodiments of the invention, the concept and terms of the reflective optical sensor will be described.

  FIG. 1 is a diagram for explaining a “color printer” which is one type of image forming apparatus.

  A color printer is an image forming apparatus that forms a toner image by an electrophotographic process and fixes the toner image on the surface of a sheet-like recording medium by a fixing device to form an image.

  FIG. 1A illustrates only a main part of the color printer 100 in an explanatory manner. The color printer 100 is a so-called “tandem printer”.

  A “transfer belt” denoted by reference numeral 11 is an endless belt, is provided around a plurality of rollers (three in the drawing) including a driving roller, and is driven by the driving roller to rotate counterclockwise.

The lower portion of the transfer belt 11 in the drawing is stretched in a “planar” manner, and image forming units UY, UM, UC, UB are disposed in this portion.
“Y, M, C, B” in the code represents each color of “yellow, magenta, cyan, black”.

  The image forming unit UY is a unit that forms a yellow image, and the image forming unit UM is a unit that forms a magenta image.

  The image forming unit UC is a unit that forms a cyan image, and the image forming unit UB is a unit that forms a black image.

  Below the image forming units UY to UB, an optical scanning device 13 which is an “image writing device” is provided, and a cassette 15 is further provided below the optical scanning device 13.

Since the image forming units UY to UB are structurally the same, the image forming unit UY is taken as an example and will be briefly described with reference to FIG.
The image forming unit UY has a structure in which a charger 30Y, a developing device 40Y, a transfer member 50Y, and a cleaning device 60Y are arranged around the photoconductive photosensitive drum 20Y.
The charger 30Y is a “contact type charging roller”.

A space between the charger 30Y and the developing device 40Y is set as an “image writing unit using the scanning light LY”.
The transfer member 50 </ b> Y has a roller shape and is disposed on the opposite side of the photosensitive drum 20 </ b> Y via the transfer belt 11 and is in contact with the back surface of the transfer belt 11.

The image forming units UM to UB have the same configuration as the image forming unit UY.
Hereinafter, the photosensitive drums 20M to 20B, the chargers 30M to 30B, the developing devices 40M to 40B, the transfer members 50M to 50B, and the cleaning devices 60M to 60B are used.

Such a “color image printing process” by the color printer 100 is well known, but will be briefly described below.
Note that the “rectangular shape indicated by a broken line” in FIG. 1B indicates the unit of the image forming unit UY as “collectively”, and does not necessarily indicate an entity such as a casing.

When the color image forming process starts, the photosensitive drums 20Y to 20B and the transfer belt 11 start to rotate.
The rotation of the photosensitive drums 20Y to 20B is clockwise, and the rotation of the transfer belt 11 is counterclockwise.

  The photosensitive surfaces of the photosensitive drums 20Y to 20B are uniformly charged by the chargers 30Y to 30B, respectively.

The optical scanning device 13 writes an image on each of the photosensitive drums 20Y to 20B by optical scanning with the scanning lights LY to LB.
Various types of optical scanning devices 13 that perform such image writing have been well known in the past. As the optical scanning device 13, these known devices are appropriately used.

  The photosensitive drum 20Y is optically scanned using a laser beam whose intensity is modulated according to the yellow image as the scanning light LY, and a yellow image is written.

  By this optical scanning, an “electrostatic latent image corresponding to a yellow image” is formed.

  The formed electrostatic latent image is a so-called negative latent image, and is visualized as a “yellow toner image” by reversal development using yellow toner by the developing unit 40Y.

  The visualized yellow toner image is electrostatically primarily transferred onto the surface side of the transfer belt 11 by the transfer roller 50Y.

  The photoconductor drum 20M is optically scanned using a laser beam whose intensity is modulated in accordance with the magenta image as the scanning light LM, and a magenta image is written.

By this optical scanning, an electrostatic latent image (negative latent image) corresponding to the magenta image is formed.
The formed electrostatic latent image is visualized as a “magenta toner image” by reversal development using magenta toner by the developing unit 40M.

  The photosensitive drum 20C is optically scanned using a laser beam whose intensity is modulated according to the cyan image as the scanning light LC, and a cyan image is written.

By this optical scanning, an electrostatic latent image (negative latent image) corresponding to the cyan image is formed.
The formed electrostatic latent image is visualized as a “cyan toner image” by reversal development using cyan toner by the developing unit 40C.

  The photosensitive drum 20B is optically scanned using a laser beam whose intensity is modulated according to the black image as the scanning light LB, and a black image is written.

By this optical scanning, an electrostatic latent image (negative latent image) corresponding to the black image is formed.
The formed electrostatic latent image is visualized as a “black toner image” by reversal development using black toner by the developing unit 40B.

  The magenta toner image is primary-transferred electrostatically to the transfer belt 11 side by the transfer roller 50M.

At this time, the magenta toner image is superimposed on the “yellow toner image previously transferred” on the transfer belt 11.
Similarly, the cyan toner image is primarily transferred onto the transfer belt 11 by the transfer roller 50C.

  At that time, the cyan toner image is overlaid on the “yellow toner image and magenta toner image transferred on top of each other”.

  The black toner image is primarily transferred to the yellow, magenta, and cyan color toner images on the transfer belt 11 by the transfer roller 50B.

  In this way, four color toner images of yellow, magenta, cyan, and black are superimposed on the transfer belt 11 to form a “color toner image”.

  Each of the photosensitive drums 20Y to 20B is cleaned by the cleaning devices 60Y to 60B after the toner image is transferred to remove residual toner, paper dust, and the like.

  The transfer paper S is stacked and accommodated in the cassette 15, and is fed by a well-known paper feeding mechanism (not shown).

  The supplied transfer sheet S stands by with its tip end held by a timing roller (also referred to as a registration roller) (not shown).

  Then, the color toner image on the transfer belt 11 is sent to the “secondary transfer portion” at the same timing.

  The secondary transfer portion is a contact portion between the transfer belt 11 and the secondary transfer roller 17 that rotates in contact with the transfer belt 11.

  The transfer paper S is fed to the secondary transfer portion by a timing roller in time with the color toner image on the transfer belt 11 reaching the secondary transfer portion.

  Thus, the color toner image and the transfer paper S are superimposed, and the color toner image is secondarily transferred (electrostatic transfer) onto the transfer paper S.

  The transfer sheet S on which the color toner image is transferred by the secondary transfer is fixed on the color toner image in the fixing device 19 and is discharged onto the tray TR on the upper side of the color printer 100.

  The outline of the “color image printing process” by the color printer 100 has been described above.

  Next, the fixing device 19 in the color printer of FIG. 1A will be described with reference to FIG.

  The fixing device 19 is a so-called “belt fixing method” as shown in FIG.

  The fixing portion includes a fixing roller 61, a heating roller 62, a fixing unit roller 64, a pressure roller 63, a tension roller 65, a peeling claw 66, and the like.

  The fixing belt 61 is configured to have a “release layer made of PFA or PTFE” on a base material such as nickel or polyimide.

  There is also a configuration in which an “elastic layer such as silicone rubber” is provided between the substrate and the release layer.

  Accordingly, the surface of the fixing belt 61 is “resin such as PFA or PTFE forming a release layer”, and the information on the surface is “surface information” to be detected.

  The fixing belt 61 is an endless belt and is wound around a heating roller 62 and a transfer roller 64 and is given a “necessary tension” by a tension roller 65.

  The heating roller 62 is a hollow roller made of aluminum or iron and includes a heat source H such as a halogen heater. The heat source H heats the fixing belt 61 via the heating roller 62.

  Although not shown, a temperature sensor (such as a thermopile) for detecting the surface temperature of the fixing belt 61 is provided on the surface of the fixing belt 61 in a “non-contact” manner.

The fixing roller 64 has a metal core metal surrounded by silicone rubber to give elasticity. The fixing roller 64 rotationally drives the fixing belt 61 counterclockwise.
The pressure roller 63 is provided with an elastic layer such as silicone rubber on a metal core such as aluminum or iron, and the surface layer is constituted by a release layer such as PFA or PTFE.

  The pressure roller 63 is in pressure contact with the fixing belt 61 at a position corresponding to the fixing roller 64.

  This pressure contact deforms the fixing roller 64 to form a “nip portion”. This nip portion becomes a fixing portion.

  The tension roller 65 is a metal core provided with silicone rubber.

  A plurality of peeling claws 66 are arranged in the axial direction (direction perpendicular to the paper surface) of the fixing roller 64 so that the pointed portion thereof is in contact with the surface of the fixing belt 61.

  Instead of the non-contact temperature sensor (not shown) for detecting the surface temperature of the fixing belt 61 described above, a contact-type temperature sensor (thermistor) may be used.

  When fixing is performed, the fixing belt 61 rotates counterclockwise and the pressure roller 63 rotates clockwise while being heated by the heater H.

  When the surface temperature of the fixing belt 61 reaches a fixable temperature, the transfer sheet S on which the color toner image is transferred is conveyed in the direction of the arrow and enters the fixing unit.

  The color toner image receives heat from the fixing belt 61 side at the transfer portion, is pressed against the fixing belt 61 by the pressure roller 63, receives pressure, and is fixed on the transfer paper S.

  Supplementally, the color printer 100 has a cleaner (not shown) for cleaning the transfer belt 11.

  The “cleaner” is disposed on the left side of the image forming unit UY in FIG. 1A so as to face the portion where the transfer belt 61 is strung over the roller.

  The cleaner has a cleaning brush and a cleaning blade disposed so as to contact the transfer belt 11.

Then, “foreign matter such as residual toner and paper dust” on the transfer belt 11 is scraped and removed by the cleaning brush and the cleaning blade.
The cleaner also has discharge means (not shown) for carrying out and discarding the residual toner removed from the transfer belt 11.

  In the example of the image forming apparatus (color printer) shown in FIG. 1, the transfer system performs primary transfer and secondary transfer as described above, but the transfer system is not limited to this.

  For example, a system in which the transfer paper S is carried on the transfer belt 11 while being conveyed and brought into contact with each photosensitive drum, and a toner image of each color is directly superimposed on the transfer paper S and transferred is also possible.

  Also in this case, the fixing of the color toner image may be the same as described above.

  In the image forming apparatus (color printer 100) shown in FIG. 1, the fixing device 19 includes a “surface information detecting device” that detects surface information of the fixing belt 61.

  The surface information detection device includes a reflective optical sensor 200 and an information detection device 300.

  Further, a movable light shielding member 400 is provided between the reflective optical sensor 200 and the fixing belt 61. However, the movable mechanism is not shown.

  The light blocking member 400 is for blocking the optical path between the reflective optical sensor 200 and the fixing belt 61, and the light blocking member 400 is moved as necessary to open and close the optical path.

  As shown in FIG. 1C, the reflective optical sensor 200 is disposed so as to face the “portion wound around the heating roller 62” of the fixing belt 61.

  The reflective optical sensor 200 has an irradiation optical system and a light receiving optical system.

  The irradiation optical system irradiates a plurality of light spots toward the surface of the fixing belt 61 in the “direction intersecting the traveling direction of the surface of the fixing belt 61”.

  The light receiving optical system receives the reflected light from the fixing belt 61.

  The above-mentioned “direction intersecting with the advancing method on the surface of the fixing belt 61” corresponds to the “main scanning direction” at the time of image writing by optical scanning, and will be simply referred to as “main scanning direction” below.

  The information detection apparatus 300 is configured as a microcomputer or a CPU, is connected to the reflective optical sensor 200, and is disposed in the color printer 100.

  In response to the detection signal from the reflective optical sensor 200, the surface state of the fixing belt 61 is detected as surface information.

  The surface of the fixing belt 61 is initially intact, but as the fixing operation is repeated, offset and scratches are generated.

  “Offset” is a state in which a part of the toner adheres to the transfer belt and is fixed on the film over time when the toner image is fixed.

  Further, as the scratches generated on the surface of the fixing belt, there are a scratch due to contact with the peeling claw 66 and the like and a “striated scratch” due to the sheet-like recording member.

  Such “the state of the surface where the scratch or offset occurs”, that is, “the presence / absence or degree of offset, the state or position of the scratch” is “surface information” and is a target to be detected by the reflective optical sensor.

In the following, detection of surface information for “striated wounds” will be mainly described.
FIG. 2 is a diagram illustratively showing fixing by the fixing device 19.

The vertical direction in FIG. 2 corresponds to the “direction intersecting the traveling direction TRD on the surface of the fixing belt 61 (the aforementioned main scanning direction)”.
Reference numeral S indicates a transfer paper (sheet-like recording medium) having a color toner image to be fixed.
In this example, the transfer sheet S is “A4 size”, and can be conveyed in the longitudinal direction and the width direction.

Symbol A4T indicates the paper width when the A4-size transfer paper S is conveyed in the longitudinal direction, and symbol A4L indicates the paper width when the A4-size transfer paper S is conveyed in the width direction (short direction).
The paper width A4L is substantially equal to the width of the fixing belt 61 (the length in the vertical direction in the figure).

  Accordingly, when the A4-size transfer sheet S is conveyed in the width direction (short direction), the streak-like scratches generated at the end in the longitudinal direction are practically not a problem.

  On the other hand, the paper width A4T is shorter than the width of the fixing belt 61, and a line-shaped scratch may occur inside the paper width A4L and cause a “fixing failure problem”.

  Reference numerals W1 and W2 in FIG. 2 indicate margins of movement of the transfer paper width end portion in the main scanning direction when the A4-size transfer paper S is conveyed in the longitudinal direction.

  Even if the A4-sized transfer sheet S is transported in the longitudinal direction, it is not possible to “completely match the transport position in the main scanning direction with respect to each transfer sheet”.

  Accordingly, the passing positions of both end portions of the transfer sheet S slightly vary in the main scanning direction.

  Alternatively, when a so-called “belt shift” occurs in the fixing belt 61 itself, the surface of the fixing belt fluctuates with respect to both end portions of the transfer sheet S in the main scanning direction.

  The margin widths W1 and W2 take into account such fluctuations.

  Further, when the fluctuation range of the position where the transfer sheet S and the fixing belt 61 contact is “narrow”, streak-like scratches are concentrated in a narrow range.

In order to avoid this, the “transport position in the main scanning direction” may be intentionally shifted for each transfer sheet during transfer sheet transfer.
The margin widths W1 and W2 are also considered in such a case. However, the margin width is about “10 mm” at most.

  When the A4 size transfer sheet S is fed in the longitudinal direction, if “existence of streak” is detected as surface information, the detection area A needs to be set larger than the margin widths W1 and W2.

  In the example of FIG. 2, the detection area A is set so as to “include the margin width W2” among the margin widths W1 and W2, and is not provided on the side where the margin width W1 is present.

  This is because streak-like scratches are considered to occur in substantially the same manner in the area of the margin width W1 and the area of the margin width W2, and detection within one margin width is considered to be practically sufficient.

  Of course, a detection area may be set for each of the marginal widths W1 and W2, and further, the size of the detection area may be set so as to extend over the entire width of the fixing belt 61.

  The reflective optical sensor 200 irradiates a plurality of light spots in the main scanning direction. A region irradiated with the plurality of light spots forms a detection region A.

  Since the reflective optical sensor 200 can form a long detection region A, the “relative positional relationship in the main scanning direction” between the reflective optical sensor 200 and the end in the width direction of the transfer paper may be relatively rough.

The information detection device 300 receives the detection signal from the reflective optical sensor 200 and detects “surface state of the fixing belt” in the detection area A as surface information.
When the width direction end portion of the transfer paper is included in the detection area A, the information on the streak formed by the width direction end portion of the transfer paper is quantified as the surface information of the fixing belt 61.

  The information on the line-shaped wound is at least one of “scratch level” and “scratch position (position in the main scanning direction)”.

  The scratch level refers to “scratch level”, that is, “scratch depth (roughness) and scratch width (size)”.

It supplements about "the depth of a wound".
When “scratches (scratches caused by contact with the thermistor or peeling nails or streak-like scratches)” occur on the surface of the fixing member, “contact pressure between the recording paper and the toner image” becomes weak at the scratched portions.
For this reason, “fixing failure” occurs according to the scratch, and “fixed image” causes “image abnormality” called “white spot (a phenomenon in which image density decreases)”.

  The “scratch depth” referred to in this specification is a parameter that represents the degree of image abnormality by quantitatively grasping such “correlation between the scratch and image abnormality caused by the wound”. .

  Next, the structure of the reflective optical sensor 200 will be described with reference to FIG.

  Assume that the above-described transfer belt is used as a test object and surface information of the surface is detected.

As shown in FIGS. 3A and 3B, x, y, and z directions orthogonal to each other are determined.
The x direction is the “direction intersecting the traveling direction” in the above description, and is the “main scanning direction” in the example being described.
The y direction corresponds to the “traveling direction”. The z direction is “a direction orthogonal to both the x and y directions”.

  Reference numeral 61S denotes a “surface portion including the detection region (detection region A)” of the fixing belt 61. Therefore, the z direction is a direction from the reflective optical sensor 200 toward the “surface portion 61S”.

  In FIG. 3, reference numeral 210 denotes a substrate, reference numeral 240 denotes a side plate, and reference numeral 220 denotes a lens element.

  FIG. 4 is a diagram for explaining the arrangement of the light emitting units and the light receiving units on the substrate 210.

  The “light emitting part” is an LED light emitting diode, and the “light receiving part” is a photodiode (hereinafter referred to as “PD”).

  In FIG. 4, reference numerals 211-1-1 to 211-P-4 denote individual LEDs, and reference numerals 212-1 to 212-N denote individual PDs.

The LEDs are arranged in the x direction as “P set with four as one set”. The arrangement direction of the four LEDs constituting each group is also the x direction.
That is, counting from the left side of FIG. 4, four LEDs 211-i-1 to 211-i-4 are arranged in the i-th group (i = 1 to P).

  The total number of LEDs to be arranged is determined by design conditions, and can generally be set to several tens to several hundreds. Further, the number of LEDs constituting one set of LEDs is not limited to four.

  In FIG. 4, P sets of LEDs are arranged at equal intervals.

  One set of LEDs constitutes an “irradiation system”. That is, in the example being described, four light emitting units (LEDs) constitute an irradiation system, and P sets of irradiation systems are arranged at equal intervals.

  The p-th irradiation system counted from the left side of FIG. 4 is an irradiation system 211-p (p = 1 to P).

  The N PDs 212-1 to 212 -N are also arranged at equal intervals in the x direction. These N PDs constitute a “light receiving system by the light receiving unit”.

  In the example being described, the number of light emitting parts: 4P and the number of light receiving parts: N are the same.

  That is, the same number of light emitting units and light receiving units are arranged on the substrate 210 in parallel with each other.

  Next, the irradiation lens and the light receiving lens will be described with reference to FIGS.

  3B and 5 indicates a lens element in which a light receiving lens and P irradiation lenses are integrally formed.

  As shown in FIGS. 3A and 3B, the P irradiation lenses 220-1 to 220-P are arrayed in the X direction to form an “irradiation lens array”.

  As shown in FIGS. 3A and 5, the light receiving lens 220C is a “single positive cylindrical lens” in which the direction having no refractive power is set in the x direction.

  The P irradiation lenses 220-1 to 220 -P are the same as the number “P” of “irradiation systems” composed of the “four LEDs (light emitting units)” described above.

  Each irradiation lens 220-p (p = 1 to P) of the irradiation lens array corresponds to the “p-th irradiation system”.

  That is, the irradiation lens 220-p is shared by the four LEDs 211-p-1 to 211-p-4 constituting the p-th irradiation system.

  A plurality of light emitting units forming one irradiation system and an irradiation lens shared by the plurality of light emitting units constitute a “unit irradiation optical system”.

  In the example in the description, the four LEDs 211-p-1 to 211-p-4 constituting the p-th irradiation system and the irradiation lens 220-p shared by these are “unit irradiation optical systems”.

  FIG. 5 is a diagram of the reflective optical sensor 200 as viewed from the “positive direction of the y-axis”.

  The light receiving lens 220C has “positive refractive power” only in the y direction.

  As described above, the irradiation lens array and the light receiving lens 220 </ b> C are integrally formed as the lens element 220. The lens element 220 can be integrally molded by resin molding.

  FIG. 3B shows a state where the q (1 ≦ q ≦ 4) th LED (light emitting unit) of the p (1 ≦ p ≦ P) th irradiation system emits light.

  The figure shows a state where the second (q = 2) LED 211-1-2 of the first (p = 1) irradiation system emits light.

  The emitted divergent light beam is collected by the irradiation lens 220-p shared by the p-th irradiation system, and forms a spot of irradiation light on the fixing belt surface 61S.

  As shown in FIG. 3A, the reflected light at the spot portion of the fixing belt surface 61S is condensed by the positive refractive power of the light receiving lens 220C in the Y direction and enters one of the PDs 212.

  FIG. 5 shows a state in which this state is viewed from the y direction.

  Reflection on the fixing belt surface 61S is not specular reflection but close to irregular reflection. The reflected light is not collected in the x direction by the light receiving lens 220C.

  Accordingly, the reflected light is received by the “plurality of PDs”.

  As described above, the N PDs constitute a “light receiving system including N light receiving units”, but the light receiving lens 220C is shared by the N light receiving units PD 210-1 to 210-N.

  The N PDs 210-1 to 210-N and the light receiving lens 220C constitute a “light receiving optical system”.

  The above explanation can be summarized as follows.

  That is, the reflective optical sensor described with reference to FIGS. 3 to 5 is for irradiating the surface of the object to be tested (fixing belt) with light and receiving the reflected light from the surface to detect surface information on the surface. Is.

  The irradiation optical system includes two or more unit irradiation optical systems including an irradiation system and an irradiation lens, and the light receiving optical system includes a light receiving system and a light receiving lens.

  The irradiation system 211-p of the unit irradiation optical system includes two or more light emitting units 211-p-1 to 211-p-4.

  The irradiation lens 220-p is shared by two or more light emitting units, and guides the light emitted from the two or more light emitting units to the surface of the test object to shift the irradiation light spot in one direction (x direction). Form.

  The light receiving system of the light receiving optical system has two or more light receiving portions 212-1 to 212-N, and the light receiving lens 220C is shared by the two or more light receiving portions.

  The reflection type optical sensor receives light reflected from the surface 61S of the test object by each unit irradiation optical system and received by the light receiving system via the light receiving lens 220C of the light receiving optical system.

  The detection of surface information by the reflective optical sensor 200 described above will be described.

  FIG. 6 is a flowchart showing this detection operation.

  In the irradiation optical system, “p-th irradiation system is irradiation system 211-p (p = 1 to P)”, and four LEDs included in this irradiation system are “LED 211-pq (q = 1 to 4)”. "

  The light emission of each LED is “sequentially lit” on the fixing belt surface 61S so that the irradiation light is sequentially irradiated from the left end spot S-1 to the right end spot S-N in FIG. .

  That is, lighting is sequentially performed from irradiation systems 211-1 to 211-P in the irradiation system unit, but is performed in the order of q = 4, 3, 2, 1 in each irradiation system.

  This is because the irradiation lens used in the unit irradiation optical system is an “inverted system”.

“Sequential lighting” turns on and off each LED in the above order.
In synchronization with the lighting of the LEDs 211-pq, the reflected light from the fixing belt surface 61S is condensed only in the y direction by the light receiving lens 220C and received by the PD of the light receiving unit.

  As described above, the reflected light reaching the light receiving unit is not collected in the x direction, and is received by a plurality of PDs.

  For simplicity of explanation, it is assumed that the number of light-receiving PDs is “odd number”, and m is an integer and is (2m + 1).

  It is assumed that the reflected light when the LED 211-pq is turned on is received by the PD 212-n and “m PDs on both sides”.

  That is, as shown in FIG. 6, the reflected light is received by PD212- (nm) to PD212- (n + m).

  If m = 2, there are five PDs that receive reflected light: PD212-n-2, PD212-n-1, PD212-n, PD212-n + 1, and PD212-n + 2.

  These PDs photoelectrically convert the amount of received light, and the photoelectrically converted signal is amplified to become a “detection signal”. Each detection signal for each PD is sent to the information detection apparatus 300 for each detection.

The value of m may not be 2, and a correlation with the surface state of the transfer belt may be experimentally obtained in advance, and a good m may be selected.
However, if m is as small as 0, there is only one PD output value, and since the value is small, detection variation becomes large.

  Conversely, when m is large and corresponds to the total number of PDs (N), the contrast of surface information (streak-like scratches) to be detected decreases. “Good m” is about 2 to 6.

  When the LED of “p = 1, q = 4” is sequentially turned on and the last LED 211-P-1 of “p = P, q = 1” is “lighted / turned off”, this is turned on sequentially as one cycle. Ends.

  In some cases, in order to increase detection accuracy, sequential lighting may be performed over a plurality of cycles, and an average value processing of detection results in each cycle may be performed.

  In the case of the above description, consider the case where the spots S-1 and S-2 near the left end on the surface 61S of the fixing belt are irradiated with illumination light as shown in FIG.

In this case, although the LED 211-1-3 and the LED 211-1-4 are turned on, the illumination lens 220-1 is an inverted magnification system, so that the number of PDs that receive the reflected light is less than five.
The same applies when the spot is the spot SN near the right end.

  In view of such circumstances, it is possible to remove two LEDs each having a spot on the fixing belt surface 61S closer to the left end and closer to the right end without using N LEDs that are sequentially lit.

  That is, you may make it light up sequentially about N-4 LED.

  That is, in general, it is not necessary to use all N LEDs to be turned on / off, and N ′ (≦ N) of them may be used.

FIG. 7 shows the experimental results when the reflective optical sensor described above is operated according to the procedure of FIG.
FIG. 7A shows the result in a state where there is no fixing belt 61 (that is, a state where there is no object reflecting the light beam emitted from the reflective optical sensor).

That is, the output values of PDn (n = 1 to 28) when the LEDs 211-pq (q = 1 to 4) are turned on without the fixing belt 61 are shown.
In FIG. 7, LED 211 -pq (q = 1 to 4) is simply referred to as “LED-pq”. This notation is also used in the following description regarding FIG.

  When there is no fixing belt, the output of each PD should be zero if it is originally, but according to the experimental results, a “mountain output distribution” is obtained centering on PD14 and PD15.

This phenomenon occurs as follows.
That is, the reflective optical sensor in the description has opening members 230-p (p = 1 to P) and 231 as shown in FIGS.

  The opening member 230-p prevents “flare light” at the adjacent portion of the unit irradiation optical system by the “LED 211-pq (q = 1 to 4) and the irradiation lens 220-p.

  The opening member 231 mainly prevents “flare light between the arrangement of the LEDs 211-pq (q = 1 to 4) and the arrangement of the PD 212-p”.

  FIG. 9 shows a state in which the opening members 230 and 231 are integrated when P = 7.

  An opening is provided corresponding to each of the “unit irradiation optical system” including a set of an irradiation system including four LEDs 211-pq (q = 1 to 4) and an irradiation lens 220-p.

  By providing an opening, it is possible to prevent the influence of flare light that passes through the “irradiating lens not corresponding to the LED being lit” and reflected by the fixing belt, or reflected by the lens surface and incident on the PD.

  As shown in FIG. 8, when the LED 211-pq is turned on, a part of the emitted divergent light beam is reflected and scattered by the end surfaces of the opening members 230-p and 231.

  The “end face” is the “end face by thickness” on the side facing the LED of the opening member as shown in FIG.

  The light reflected by the end face is received by a plurality of PDs.

  The light shielding member 400 shown in FIG. 1C is for intentionally creating a state without the fixing belt 61 in the image forming apparatus.

When the fixing belt 61 exists, the PD output including the reflected light from the end surface of the opening member in addition to the reflected light from the fixing belt to be originally detected is detected.
Therefore, the PD output is detected with the light shielding member 400 closed, and then the PD output is detected with the light shielding member opened, and the difference between the two is calculated.

By doing so, “output of only reflected light from the surface of the fixing belt” can be obtained.
FIG. 7B shows the PD output when the PD output acquired with the light shielding member 400 closed is subtracted from the PD output acquired with the fixing belt 61.
That is, the PD output in FIG. 7B is a signal only of the reflected light from the fixing belt 61. In FIG. 7 (b), when the peak peaks blink in the order of LED-p-4, LED-p-3, LED-p-2, LED-p-1, the PD number increases from 1 to 4. Has shifted to.

This is because when the LED-p-4, LED-p-3, LED-p-2, and LED-p-1 blink in this order, the spot on the fixing belt surface 61S moves from left to right.
FIG. 7A shows a state where light from the LED is directly reflected by the aperture member and received by the PD.

If the shape of the “end face of the opening member” is the same when viewed from each LED, it is considered that the PD received light amount proportional to the LED light emission amount can be detected.
The pitch of the opening members is sufficiently larger than “the interval between the LEDs 211-p-1 to 211-p-4”, and can be regarded as substantially the same shape from any LED.

  For this reason, the distribution in FIG. 7A is also similar for each LED, and is considered to represent the variation in the amount of emitted LED light at the time of detection.

  The code | symbol 241 in Fig.3 (a) shows the side plate of the width direction (y direction). The side plates 240 and 241 are integrated to form a case.

  The opening members 230 and 231 can be integrated with the “case” by resin molding.

  The above is the description of the basic concept of the reflective optical sensor.

  Based on the above description, embodiments of the invention will be described below.

  FIG. 10 is a diagram for explaining one embodiment (hereinafter, referred to as Embodiment 1) of the reflective optical sensor of the present invention.

  In FIG. 10, the x direction is the main scanning direction, the y direction is the sub-scanning direction, and the z direction is a direction orthogonal to the xy plane, which is the “direction in which the reflective optical sensor 200a faces the fixing belt 61a”.

  As the “test object”, a fixing belt is assumed.

The size and arrangement of the individual light receiving parts constituting the light receiving system are the same as those of the reflective optical sensor 200 described with reference to FIG.
As will be described later in detail, the size and arrangement state of the individual light emitting units constituting the irradiation system are the same.

  However, the arrangement of the irradiation system is not necessarily the same for each unit irradiation optical system.

  As shown in FIG. 10, the reflective optical sensor 200a has an irradiation optical system and a light receiving optical system.

  The irradiation optical system is configured by an array of unit irradiation optical systems including an irradiation system and an irradiation lens.

  The light receiving optical system includes a plurality of light receiving portions and a light receiving lens.

  In FIG. 10, the x direction corresponds to the main scanning direction, and the y direction corresponds to the sub scanning direction. The z direction is also the optical axis direction of the irradiation lens.

  FIG. 10A shows a state in which the reflective optical sensor is viewed from the x direction, where reference numerals 211a-pq denote light emitting units, and reference numerals 220a-p (p = 1 to 7) denote irradiation lenses. .

The light emitting units 211a-pq are LEDs and emit near-infrared light.
FIG. 10B shows a state in which the reflective optical sensor is viewed from the “−y direction”.

  As shown in FIG. 10B, the four LEDs 220a-1-1-1 to 220a-1-4 are arranged at equal intervals close to each other in the x direction to form the irradiation system 1.

Seven irradiation systems 1 to 7 having the same configuration as the irradiation system 1 are “arranged in the x direction”.
The rightmost irradiation system 7 in FIG. 10B includes LEDs 211a-7-1 to 211a-7-4.

Irradiation lenses are provided for each of the irradiation systems 1 to 7 in a one-to-one correspondence.
The irradiation lenses 220a-1 to 220a-7 correspond to the irradiation systems 1 to 7, respectively.

  As shown in FIGS. 10A and 10B, the irradiation lens 221a-1 and the like and the light receiving lens 222ac are anamorphic lenses having different curvatures in the x direction and the y direction.

  The irradiation lens 221a-1 and the like and the light receiving lens 222ac are integrated to form a lens array 220a.

  FIG. 11 shows a state in which the reflective optical sensor is viewed from the y direction.

  As shown in FIG. 11, the light receiving optical system includes PDs 212 a-1, 212 a-2,..., 212 a-28 as light receiving units arranged on a substrate 210 a.

  FIG. 12 shows a simplified portion necessary for explanation in the state shown in FIG.

  That is, FIG. 12 shows five irradiation systems and irradiation lenses of the reflective optical sensor from the one end (left end) side in the x direction.

  That is, the irradiation systems 1 to 5 and the irradiation lenses 220a-1 to 220a-5 corresponding one-to-one to these are shown.

  Each of the irradiation system 1 to the irradiation system 5 is configured by arranging four LEDs, which are light emitting units, close to each other in the x direction.

  That is, as p (= 1 to 5) and q (= 1 to 4), the illumination system p includes four light emitting units “LEDs 211a-p-1 to 211a-p-4”.

  As shown in FIG. 11, irradiation lenses 220a-2 to 220a-5 correspond to the irradiation systems 2 to 5, respectively.

  The light emitting portions in these irradiation systems 2 to 5 are LEDs 211a-p-1 to 211a-p-4 as p (= 2 to 4).

  The LEDs 211a-p-1 to 211a-p-4 of each irradiation system p (p = 2 to 5) are arranged as shown in FIG.

  That is, the LEDs 211a-p-1 to 211a-p-4 are arranged symmetrically in the x direction with respect to a plane including the optical axis of the irradiation lens 220a-p and parallel to the y direction.

  Assuming that the plane is a plane p, the LEDs 211a-p-1 and 211a-p-2 are located on the left side of the plane p, and the LEDs 211a-p-3 and 211a-p-4 are located on the right side of the plane p. .

  On the other hand, in the light shielding system 1 in which p = 1, all of the LEDs 211a-1 to 211a-1-4 are located on the left side of the plane 1 including the optical axis of the irradiation lens 220a-1 and parallel to the y direction.

  The arrangement form of the four LEDs 211a-pq constituting the irradiation system p is the same, and the arrangement pitch is also the same.

  In the irradiation system p (= 2 to 5), the LEDs 211a-p to 211a-p-4 are all arranged symmetrically in the x direction with respect to the plane p (= 2 to 5).

  In the illumination system 1, the LEDs 211 a-1-1 to 211 a-1-4 are arranged by shifting two pitches to the left with respect to the plane 1 from positions symmetrical to the plane 1.

  For later explanation, an array in which the LEDs are shifted is called a “shift array”, and an array that is not shifted is called an “original array”.

  When the light emitting section in the irradiation system 1 is set to the “shift arrangement”, the light emitted from the LED 211a-1-1 irradiates the position of the spot Sa-4 on the fixing belt surface 61Sa.

  The light emitted from the LED 211a-1-2 irradiates the position of the spot Sa-3 on the fixing belt surface 61Sa.

  The light emitted from the LED 211a-1-3 irradiates the position of the spot Sa-2 on the fixing belt surface 61Sa.

  The light emitted from the LED 211a-1-4 irradiates the position of the spot Sa-1 on the fixing belt surface 61Sa.

  The position of the spot Sa-4 is also the position of a spot formed by the light from the LED 221a-2-3 of the irradiation system 2 being condensed by the irradiation lens 220a-2.

  The position of the spot Sa-3 is also the position of the spot formed by condensing the light from the LED 221a-2-4 of the irradiation system 2 by the irradiation lens 220a-2.

  The symbols (Sa-1), (Sa-2), (Sa-3),... In FIG. 12 are irradiated with light from each light emitting unit when the LED array of the irradiation system 1 is set to the “original array”. It is a spot to do.

  The position of the spot Sa-1 is the same position as the spot (Sa-3) formed by collecting the light from the LED 211a-1-2 in the “original arrangement” by the irradiation lens 220a-1.

  The position of the spot Sa-2 is the same position as the spot (Sa-4) formed by condensing the light from the LED 211a-1-1 in the “original arrangement” by the irradiation lens 220a-1.

  The position of the spot Sa-4 is also the position of a spot formed by the light from the LED 221a-2-3 of the irradiation system 2 being condensed by the irradiation lens 220a-2.

  Of course, the incident angles of the two light beams that irradiate the spot Sa-4 are different between the LED 211a-1-1 and the LED 211a-2-3.

  The “incident angle” is an angle formed by the straight line connecting the center of gravity of the spot formed by the irradiation light and the exit lens surface vertex of the irradiation lens collecting the irradiation light, and the optical axis of the irradiation lens. It is.

  Similarly, the position of the spot Sa-3 is also the position of a spot formed by the light from the LED 221a-2-4 of the irradiation system 2 being condensed by the irradiation lens 220a-2.

  Also in this case, the incident angles of the two light beams that irradiate substantially the same position are different.

  If the array of the four LEDs of the irradiation system 1 is the “original array” and is the same as the array of the irradiation system 2 or the like, the irradiated spots are spots (Sa-1), (Sa-2).・ It is.

  In the embodiment being described, since the array of LEDs of the irradiation system 1 is a “shift array”, the irradiated spots are spots Sa-1, Sa-2,.

  The arrangement of the LEDs of the irradiation system 1 is a shift arrangement, and the positions of the spots (Sa-1) and (Sa-2) in the case of “original arrangement” are not irradiated.

  Instead, the spots Sa-3 and Sa-4 are also irradiated by the light beams from the LEDs 221a-2-4 and 221a-2-3 of the irradiation system 2 adjacent to the irradiation system 1.

  That is, both the spots Sa-3 and Sa-4 are irradiated with light beams having different incident angles from two adjacent unit irradiation optical systems.

  Two adjacent unit irradiation optical systems are based on the irradiation system 1 and the irradiation lens 220a-1 and on the irradiation system 2 and the irradiation lens 220a-2.

  Returning to FIG. 10B, in the irradiation system 7 at the right end in the x direction of the reflective optical sensor 200a, the arrangement of the four LEDs is a “shift arrangement”.

  That is, the four LEDs 221a-7-1 to 221a-7-4 constituting the irradiation system 7 are asymmetric with respect to the plane 7 including the optical axis of the irradiation lens 220a-7 and parallel to the y direction.

  That is, it is shifted to the right by 2 pitches with respect to the plane 7.

  For this reason, the irradiated spots (Sa-27) and (Sa-28) are not irradiated in the shift arrangement in the case of the original arrangement.

  Instead, the spots Sa-27 and Sa-28 are irradiated with light beams having different incident angles from two adjacent unit irradiation optical systems.

  Accordingly, the reflective optical sensor according to the embodiment described with reference to FIGS. 10 to 12 includes the irradiation optical system and the light receiving optical system.

  The irradiation optical system is formed by arranging unit irradiation optical systems including irradiation systems 1 to 7 and irradiation lenses 200a-1 to 220a-7.

  The light receiving optical system includes PDs 212a-1 to 212a-28, which are light receiving systems, and a light receiving lens 220ac.

  The irradiation system p (p = 1 to 7) of the unit irradiation optical system includes LEDs 211a-pq (q = 1 to 4) which are a plurality of light emitting units.

  The irradiation lenses 220a-p (p = 1 to 7) of the unit irradiation optical system are shared by the four light emitting units, and guide light emitted from each light emitting unit to the surface 61Sa of the test object.

  The guided light is formed by irradiating the surface 61Sa and shifting the irradiated light spots Sa-1, Sa-2,... In the x direction.

  The light receiving system of the light receiving optical system has two or more light receiving parts PD212a-1 to 212a-28, and the light receiving lens 220ac is shared by two or more light receiving parts.

  The reflected light that is irradiated onto the surface 61Sa of the test object by each unit irradiation optical system of the irradiation optical system and reflected by the surface is received by the light receiving system via the light receiving lens 220ac.

  The spots Sa-1, Sa-2,... Radiated from the individual light emitting units and applied to the surface 61Sa are continuously arranged in the x direction.

  Among these spots, there are those (spots Sa-1, Sa-2, Sa-27, Sa-28) irradiated from different unit irradiation optical systems at different incident angles.

  The positional relationship between the light emitting unit and the irradiation lens in the irradiation optical system is adjusted so that such a condition is satisfied.

  FIG. 13 is a diagram for explaining the characteristics of the reflective optical sensor described above with reference to FIGS.

  The horizontal axis of the figure represents the angle β (degrees) formed by the x direction described above (the longitudinal direction of the reflective optical sensor 200a and corresponding to the main scanning direction) and the fixing belt surface 61Sa.

  This angle: β is hereinafter referred to as “skew angle: β”. The skew angle β is positive when the fixing belt surface 61Sa is tilted counterclockwise with respect to the x-axis.

  The skew angle β is ideally 0 degree, and at this time, the light-irradiated portions of the reflective optical sensor 200a and the fixing belt surface 61Sa are parallel.

  However, if the positional relationship with respect to the fixing belt is shifted due to an assembly error of the reflective optical sensor 200a, the skew angle is not zero.

  Further, when there is a phenomenon in which the fixing belt surface 61Sa tilts in a swinging manner with respect to the arrangement direction of the light emitting units and the light receiving units (the above-described “fluttering”), the skew angle: β also varies.

  In order to obtain the result of FIG. 13, four LEDs were blinked independently in each of the irradiation systems (irradiation system 1 to irradiation system 7) belonging to the irradiation lenses 200a-1 to 200a-7.

  Each time each LED is caused to emit light, the sum of the output of the PD having the maximum output and the output of a total of nine PDs including this PD was defined as the sensor light receiving unit output.

  A result of normalizing the sensor light receiving unit output with a median value (β = 0 [deg] in the graph) when the skew angle: β is 0 is a “relative value” on the vertical axis.

  The range of the skew angle: β was ± 3 degrees.

  Suppose that the flaw of the fixing belt can be detected when the fluctuation of the light receiving unit output is within the range of the median value: ± 10%.

  At this time, it is assumed that the fluctuation range of the skew angle: β due to “flapping of the fixing belt” and “deviation due to assembly error” is ± 1 degree.

  In this case, the light receiving unit outputs by the four LEDs 211a-1-1, 211a-1-2, 211a-2-1 and 211a-2-2 are stable.

  Moreover, as p = 3-5 and q-1-4, the output by 12 LEDs 211a-pq is also stable.

  Furthermore, the light receiving unit output by the four LEDs 211a-6-3, 211a-6-4, 211a-7-3, and 211a-7-4 is also stable.

  Therefore, even when there is a flutter or a positional deviation within a skew angle: β of ± 1 degree, the 20 LEDs can be used for “detecting a flaw (surface information) on the fixing belt using the light emitting portion”.

  Therefore, it is possible to detect flaws on the fixing belt in the “detection area A ′” facing the irradiation lenses 220 a-2 to 220 a-6.

  In other words, when the skew angle β is negative, the light receiving unit outputs of the LEDs 211a-1-3, 211a-1-4, 211a-2-3, and 211a-2-4 are greatly reduced.

  This is because the incident direction when the light from these LEDs irradiates the fixing belt surface 61Sa is directed to the left side in FIG.

  That is, in such an incident direction, the direction of the reflected light from the fixing belt surface 61Sa is also directed to the left in FIG.

  For this reason, at a negative skew angle, the direction of the reflected light is further swung to the left in the figure, the amount of incident light on the PD that receives the reflected light is reduced, and the light receiving unit output is reduced.

  When the array of the LEDs 211a-1-1 to 211a-1-4 constituting the irradiation system 1 is the “original array”, the region that can be detected within the range of the skew angle: β of ± 1 degree is the detection region A ′ of FIG. 'become.

  That is, the LEDs 211a-1-3 and 211-a-1-4 in the shift array correspond to the LEDs 211a-1-1 and LEDs 211a-1-2 in the “original array”.

  Also, the LEDs 211a-2-3 and 211-a-2-4 in the shift array correspond to the LEDs 211a-2-3 and LED 211a-2-4 in the “original array”.

  Regarding the LEDs of the irradiation system 7, the LEDs 211a-7-1 and 211a-7-2 in the shift system correspond to the LEDs a-7-3 and LEDs 211a-7-4 in the “original arrangement”.

  Regarding the LED of the irradiation system 6, the LED 211a-6-1 and the LED 211a-6-2 in the shift system correspond to the LEDa-6-1 and the LED 211a-6-2 even in the “original arrangement”.

  Based on these correspondences, when FIG. 13 is viewed, the LED whose fluctuation of the light receiving unit output exceeds the “median value ± 10%” in the range where the skew angle: β is ± 1 degree is as follows.

  That is, in the “original arrangement” with respect to the irradiation systems 1 and 2, they are the LED 211a-1-3, the LED 211a-1-4, the LED 211a-2-3, and the LED 211a-2-4.

  The irradiation systems 6 and 7 are the LEDa-6-1, LEDa-6-2, LED 211a-7-3, and LED 211a-7-4 in the “original arrangement”.

  In the “original array”, the spots irradiated with light from these eight LEDs are the spots (Sa-1), (Sa-2), (Sa-5), (Sa-6), and the spots (Sa -23), (Sa-24), (Sa-27), and (Sa-28).

Therefore, even if the skew angle: β is in the range of ± 1 degree, spots whose fluctuation of the light receiving unit output does not exceed the “median range of ± 10%” are (Sa-3) and (Sa− 4), (Sa-7), (Sa-8)... (Sa-21), (Sa-22), (Sa-25), (Sa-26).
Since (Sa-5), (Sa-6), (Sa-23), and (Sa-24) exceed the “median range of ± 10%”, as a result, the skew angle: β is ± 1 degree. The area detectable in the range is the detection area A ″ up to (Sa-7), (Sa-8)... (Sa-21), (Sa-22) in the “original array”.

  Hereinafter, the lens parameters of the irradiation lens and the light receiving lens will be specifically described.

  As shown in FIG. 10, the irradiation lenses 220a-p (p = 1 to 7) have an anamorphic aspherical surface on the irradiation system side and a flat surface on the fixing belt surface side.

  The curvature radius in the main scanning direction (x direction) of the anamorphic aspheric surface is 4.6 mm, the cone constant is 0, the radius of curvature in the sub scanning direction (y direction) is 4.3 mm, and the cone constant is −2.0. .

  The lens diameter of the anamorphic aspherical surface is 2.4 mm in the x direction, 9.2 mm in the y direction, and the lens thickness is 6.6 mm.

  As shown in FIGS. 10 and 11, the light receiving lens 220ac has an anamorphic aspherical surface on the irradiation system side and a flat surface on the fixing belt surface side.

  The radius of curvature of the anamorphic aspheric surface of the light receiving lens 220ac in the x direction is 30 mm, the conic constant is −1.5, the radius of curvature in the y direction is 4.8 mm, and the conic constant is −1.6.

  The lens diameter of the light receiving lens 220ac is x direction: 17 mm, y direction: 11.2 mm, and lens thickness: 6.6 mm.

  The distance between the irradiation lens 212a-p and the light receiving lens 220ac in the y direction is 2.53 mm, and the distance between the irradiation system and the irradiation lens in the z direction is 10.37 mm.

  The distance between the light receiving system (PD) and the light receiving lens in the z direction is 10.37 mm.

  In the reflective optical sensor of Embodiment 1, the light emitted from the light emitting part of the irradiation system on the end side in the x direction of the reflective optical sensor reaches the light receiving system regardless of variations and the like.

  For this reason, even if there is a “flutter around the y direction” on the surface of the transfer belt or a deviation in the assembly position of the reflective optical sensor, accurate detection is possible.

  With reference to FIG. 14 and subsequent figures, another embodiment of the reflective optical sensor (hereinafter referred to as Embodiment 2) will be described.

  In order to avoid confusion, the same reference numerals as those in FIGS. 10 to 12 are used for those that are not likely to be confused.

  In the reflective optical sensor 200a of the first embodiment described above, as shown in FIG. 10, the transfer belt surface 61Sa irradiated with light from the LED that is the light emitting portion is planar.

  The fixing belt has an endless belt shape and is wound around a plurality of rollers.

  In addition, as shown in FIG. 1C, the reflective optical sensor 200a is often disposed opposite to the surface of the fixing belt at a portion wound around a roller.

  In this case, the surface of the fixing belt irradiated with light from the reflective optical sensor is a curved surface (cylindrical surface) convex in the sub-scanning direction, and scatters the reflected light in the sub-scanning direction.

  In this case, in order to guide the reflected light to the light receiving unit, it is necessary to enlarge the light receiving lens in the sub-scanning direction, or to apply “a large positive refractive power in the sub-scanning direction”.

  The second embodiment described below takes such points into consideration.

  FIG. 14 shows the reflective optical sensor 200b following the reflective optical sensor 200a of FIG. In the code | symbol in a figure, it is p = 1-7 and q = 1-4.

  The fixing belt surface 61Sb whose surface information is detected by the reflective optical sensor 200b is wound around a roller (not shown) and forms a “partial cylindrical surface” as shown in FIG.

  As shown in FIG. 14A, the irradiation lenses 220b-p make the light from the LEDs 211b-pq incident in a focused state on the fixing belt surface 61Sb in the y direction.

That is, the optical parameters of the irradiation lens 220b-p are optimized so that the “diameter in the sub-scanning direction” of the spot of the irradiation light is minimized on the fixing belt surface 61Sb.
In order to minimize the diameter of the spot in the sub-scanning direction on the surface of the fixing belt, the LEDs 211b-pq and the fixing belt surface 61Sb may be in a conjugate relationship in the sub-scanning direction.

  In this way, even if the reflected light has a tendency to diverge in the sub-scanning direction with the curvature of the fixing belt surface 61Sb in the sub-scanning direction, the spread of the reflected light beam in the sub-scanning direction is suppressed.

  Therefore, it is not necessary to enlarge the size of the light receiving lens 220bC in the y direction.

  As shown in FIG. 14, the irradiation lenses 220b-p (p = 1 to 7) have an anamorphic aspheric surface on the irradiation system side and a flat surface on the fixing belt surface side.

  Specific lens parameters of the irradiation lens 220b-p and the light receiving lens 220bC are as follows.

  The radius of curvature of the irradiation lens 220b-p in the x direction is 4.6 mm, the cone constant in the x direction is 0, the radius of curvature in the y direction is 4.0 mm, and the cone constant in the y direction is −2.0.

The irradiation lens 220b-p has a lens diameter in the x direction of 2.4 mm, a lens diameter in the y direction of 9.2 mm, and a lens thickness of 6.6 mm.
As is clear from this, the irradiation lens 220b-p differs from the irradiation lens 220a-p only in “the radius of curvature of the lens surface in the y direction”.

  That is, the irradiation lens 220b-p has a stronger positive refracting power in the sub-scanning direction than the irradiating lens 220a-p, and the above “conjugated relationship” is realized by this refracting power.

  As shown in FIG. 14, the light receiving lens 220bC has an anamorphic aspheric surface on the irradiation system side and a flat surface on the fixing belt surface side.

  The radius of curvature of the anamorphic aspherical surface of the light receiving lens 220bC in the x direction is 30 mm, the conic constant is −1.5, the curvature radius in the y direction is 4.8 mm, and the conic constant is −1.6.

  The lens diameter of the light receiving lens 220ac is x direction: 17 mm, y direction: 11.2 mm, and lens thickness: 6.6 mm.

  As is clear from this, the light receiving lens 220bC is the same as the light receiving lens 220ac in the above-described embodiment.

  The distance between the irradiation lens 212a-p and the light receiving lens 220ac in the y direction is 2.53 mm, and the distance between the irradiation system and the irradiation lens in the z direction is 10.37 mm.

  The distance between the light receiving system (PD) and the light receiving lens in the z direction is 10.37 mm.

  Also in the second embodiment, a plurality of irradiation lenses and a light receiving lens are integrated into one lens to form a lens array 220b.

  The reflective optical sensor 200b described above can be used for the fixing belt surface 61Sb in exactly the same manner as the reflective optical sensor 200a described above.

  As described above, the “optical function in the main scanning direction” of the reflective optical sensor 200b is the same as that of the reflective optical sensor 200a.

  Therefore, even if there is a flutter or a positional shift in the range where the skew angle β is ± 1 degree, it is possible to detect flaws in the fixing belt within the “detection area A ′” shown in FIG.

  The “detection area A ′” is a range facing the irradiation lenses 220 b-2 to 220 b-6.

  In FIG. 14, reference numeral 212b denotes a light receiving part (PD), reference numeral 210b denotes a substrate that supports the LED and PD, and reference numeral 240b denotes a case.

  As described above, if the irradiation area of the spot that irradiates the surface of the fixing belt can be reduced, reflected light that cannot reach the light receiving system can be suppressed.

  Therefore, it is possible to detect the surface state of the fixing member with high accuracy even if a reflection type optical sensor is disposed not only on the plane portion not affected by the curvature of the roller but also in the vicinity of the roller.

  The following is a modification of the reflective optical sensor 200b described immediately above. Hereinafter, this embodiment will be referred to as a third embodiment.

  In order to avoid complication, FIG. 14 is also used for the description of the third embodiment.

Specific lens parameters of the irradiation lens 200b-p (p = 1 to 7) and the light receiving lens 200bC will be listed.
The shape of these lenses is the same as that described above, and the irradiation system / light receiving part side is an anamorphic aspherical surface, and the fixing belt surface side is flat.

  As described above, the x direction corresponds to the “main scanning direction”, the y direction corresponds to the “sub scanning direction”, and the z direction corresponds to the lens optical axis direction.

  The irradiation lens 220b-p has an x-direction radius of curvature of 4.36 mm, an x-direction cone constant of −1.6, a y-direction radius of curvature of 4.0 mm, and a y-direction cone constant of −2.0. is there.

  The irradiation lens 220b-p has a lens diameter in the x direction: 2.4 mm, a lens diameter in the y direction: 9.2 mm, and a lens thickness: 6.6 mm.

  As is clear from this, in this example, only the radius of curvature of the irradiation lens in the x direction: the conic constant is different from that described above.

  That is, the irradiating lens of the third embodiment has a slightly higher refractive power in the main scanning direction than the irradiating lens of the second embodiment.

  On the other hand, the light receiving lens 220bC has a curvature radius in the x direction of 30 mm, a cone constant in the x direction: -1.5, a curvature radius in the y direction: 4.8 mm, and a cone constant in the y direction: -1.6.

  The light receiving lens 220bC has a lens diameter in the x direction of 17 mm, a lens diameter in the y direction of 11.2 mm, and a lens thickness of 6.6 mm.

  As is clear from this, the light receiving lens of the third embodiment is the same as that of the second embodiment.

  Distance between irradiation lens 220b-p and light receiving lens 220bC in the y direction: 2.53 mm, distance between irradiation system and irradiation lens in the z direction: 10.37 mm, light receiving system (PD) in the z direction And the distance between the light receiving lenses: 10.37 mm.

  That is, the positional relationship among the LED, PD, irradiation lens, and light receiving lens in the third embodiment is the same as that in the second embodiment.

  In the reflective optical sensors 200a and 200b of Embodiments 1 and 2 described above, the distance between spots on the surface of the fixing belt is set to 0.6 mm as an example.

  “Spot-to-spot distance” is an interval (center-to-center distance) between adjacent spots in the main-scanning direction in the arrangement in the main-scanning direction of spots of irradiation light irradiated on the fixing belt surface.

  In the reflective optical sensors of Embodiments 1 and 2, the spot diameter in the x direction is set to about 0.9 mm so that “a portion where no light is irradiated between adjacent spots” does not occur.

  The spot diameter on the test object is directly linked to the detection accuracy of the flaw on the fixing belt.

  In the reflective optical sensor of Embodiment 3, the spot diameter in the x direction is maintained at the same level as that in Examples 1 and 2.

  The “spot diameter in the x direction” of the reflected light incident on the light receiving lens 220bC is made smaller.

  That is, in order to realize this, the refractive power in the x direction (main scanning direction) of the irradiation lens 220bC was adjusted as described above.

  With respect to the x direction, the light emitted from each irradiation system satisfies a conjugate relationship with the light emitting part of each irradiation system at any position from the time it is reflected by the surface of the fixing belt to the light receiving system.

  As a result, the spot diameter on the fixing belt surface in the x direction can be maintained at the same level as in the first and second embodiments.

  The “light beam diameter in the x direction” of the reflected light incident on the light receiving lens 220bC can be made smaller than those in the first and second embodiments.

  That is, since the reflected light once forms an image in the x direction between the fixing belt surface and the light receiving system, the width of the light beam incident on the light receiving lens and the light receiving system can be reduced in the x direction.

By reducing the “light beam diameter in the x direction”, it is possible to more effectively reduce the influence of the fluttering of the fixing belt on the sensor output of the reflection type optical sensor and the positional deviation.
It should be noted that the “any position” that becomes “conjugated with respect to the x direction” with the light emitting portion of each irradiation system is preferably closer to the surface of the light receiving system when the radius of curvature of the light receiving lens in the x direction is zero.

  When the curvature radius in the x direction of the light receiving lens is other than 0, the vicinity of the back surface (fixing belt surface side) of the light receiving lens is preferable. Both are positions where the refractive power of the light receiving lens acts.

  Hereinafter, Embodiment 4 will be described as another embodiment.

  FIG. 15 is a diagram for explaining the reflective optical sensor 200d according to the fourth embodiment.

  FIG. 15A shows a state viewed from the x direction (main scanning direction), and FIG. 15B shows a state viewed from the y direction (sub scanning direction). The z direction is the lens optical axis direction.

  Reference numerals 211 d-1-1 to 211 d-1-4 represent four LEDs constituting the irradiation system 1, and reference numerals 211 d-7-1 to 211 d-7-4 represent four LEDs constituting the irradiation system 7. Show.

Reference numeral 220d-p (p = 1 to 7) denotes an irradiation lens, reference numeral 220dC denotes a light receiving lens, reference numeral 210d-r denotes a PD as a light receiving unit, and r = 1 to 28.
The irradiation lens 220d-p and the light receiving lens 220dC are integrated to form a lens array 220d.

  Reference numeral 210d includes a substrate 210d that supports the irradiation system and the light receiving system, and reference numeral 240d includes a substrate 210d and a case 240d that holds the lens array 220d.

  Specific lens data of the irradiation lens and the light receiving lens will be listed.

  The irradiation lens 220d-p has a curvature radius in the x direction of 4.36 mm, a cone constant in the x direction: -1.6, a curvature radius in the y direction: 4.0 mm, and a cone constant in the y direction: -2.0. is there.

  The lens diameter of the irradiation lens in the main scanning direction is 2.4 mm, the lens diameter of the irradiation lens in the sub-scanning direction is 9.2 mm, and the lens thickness of the irradiation lens is 6.6 mm.

  The light receiving lens 220dC has a curvature radius in the x direction: ∞, a cone constant in the x direction: 0, a curvature radius in the y direction: 4.8 mm, and a cone constant in the y direction: -1.6.

  The light receiving lens 220dC has a lens diameter in the x direction of 17 mm, a lens diameter in the y direction of 11.2 mm, and a lens thickness of 6.6 mm.

  The distance between the irradiation lens and the light receiving lens in the y direction is 2.53 mm, and the distance between the irradiation system and the irradiation lens in the z direction is 10.37 mm.

  The distance between the light receiving system (PD) and the light receiving lens 220dC in the z direction is 10.37 mm.

  That is, the reflective optical sensor 200d of Embodiment 4 is the same as the reflective optical sensor of Example 3 except for the light receiving lens 220dC.

  That is, the reflective optical sensor 200d of the fourth embodiment is obtained by replacing the light receiving lens of the reflective optical sensor of the third embodiment with a “cylindrical lens having no refractive power in the x direction”.

  The reflective optical sensors of Embodiments 1 to 3 described above have a configuration in which 28 PDs forming a light receiving system are arranged in the x direction.

  The reflected light from the transfer belt surface needs to be focused by the light receiving lens in the y direction (sub scanning direction) in consideration of the PD position and the light receiving surface size of the PD.

However, since a plurality (28) of PDs are arranged in the x direction, it is not necessary to squeeze the lens with a light receiving lens.
First, the characteristics of the reflective optical sensor of Embodiment 1 have been described with reference to FIG.

  Also in the reflective optical sensors of Embodiments 2 and 3, the characteristics in the x direction are not different from those in Example 1, so that the description of FIG. 13 can also be used for these reflective optical sensors.

  The characteristics of the reflective optical sensor 200d of Embodiment 4 are shown in FIG. 16 following FIG. The explanation about the vertical axis and the horizontal axis in the figure is the same as that of FIG.

  Comparing FIG. 16 and FIG. 13, it can be seen that the flaw (surface information) on the surface of the fixing belt can be detected even if the light receiving lens is a cylindrical lens having no refractive power in the x direction.

  That is, it is possible to detect flaws on the surface of the fixing belt even if there is a flutter or misalignment within the range of the skew angle β of ± 1 degree on the surface of the fixing belt.

  The cylindrical lens can be easily formed at a lower cost than the “anamorphic light-receiving lens having power in the x and y directions” in the first to third embodiments.

  When the light receiving lens has power in the main scanning direction (x direction) as in the first to third embodiments, the following cases can be considered.

  That is, there are “a plurality of illumination light beams incident at substantially the same incident angle” on the surface of the fixing belt through different illumination lenses.

  In the case of the first embodiment, for example, it is a light beam emitted from the LEDs 211a-2-2, 211a-4-2 and the like and incident on the surface of the fixing belt.

  In this case, the light beam emitted from the LED 211a-2-2 irradiates the surface of the fixing belt and reflected is incident on the light receiving system through a portion close to the end portion in the x direction of the light receiving lens.

  On the other hand, the light beam emitted from the LED 211a-4-2, irradiating the surface of the fixing belt and reflected is incident on the light receiving system through a portion near the center in the x direction of the light receiving lens.

  As described above, the “PD received light amount distribution” in the light receiving unit may be different between the reflected light passing through the end in the x direction of the light receiving lens and the reflected light passing through the center.

  The “PD received light amount distribution” is a distribution of light amounts received by a plurality of PDs.

  As in the fourth embodiment, when the light receiving lens is a cylinder lens having no power in the x direction, the “light beam incident at substantially the same incident angle” on the surface of the fixing belt generates substantially the same PD received light amount distribution. Compared to the case of the lens, the change in the PD received light amount distribution can be suppressed.

  For this reason, surface information on the surface of the fixing belt can be detected with higher accuracy.

In the reflective optical sensor of the present invention, the irradiation lens and the light receiving lens can be basically formed separately from each other and combined so as to have a predetermined positional relationship.
However, as in the first to fourth embodiments, the lens arrays 220a, 220b, and 220d may be formed by integrating a plurality of irradiation lenses and light receiving lenses.

By integrating the irradiating lens and the light receiving lens, it is possible to improve the workability when assembling each lens to the reflective optical sensor, and to improve the arrangement accuracy between the lens surfaces.
Therefore, the light receiving unit output fluctuation (PD light receiving quantity fluctuation) is suppressed, and the surface state of the fixing belt can be detected with higher accuracy.

  In the following, Embodiment 5 will be described as still another embodiment.

  FIG. 17 is a diagram for explaining the reflective optical element 200f according to the fifth embodiment.

  FIG. 17A shows a state where the reflective optical element 200f is viewed from the x direction (main scanning direction), and FIG. 17B shows a state viewed from the y direction (sub scanning direction).

  Reference numeral 211f-pq (p = 1 to 7, q = 1 to 4) denotes an LED constituting the irradiation system, and reference numeral 220f denotes a lens array in which seven irradiation lenses and a light receiving lens are integrated. .

  The irradiation lens and the light receiving lens are the same as those in the fourth embodiment.

  In addition, reference numeral 210f in FIG. 11A indicates an array of 28 PDs forming a light receiving unit. The arrangement of PDs forming the light receiving unit is the same as that of the first embodiment.

  Reference numeral 210f denotes a substrate that supports the LEDs 211f-pq and 28 PDs 212f. Reference numeral 240 denotes a case for holding the substrate 210f and the lens array 220f.

  Reference numerals 230f-0, 230f-1,..., 230f-7, 231f denote “light shielding walls for preventing flare light”.

  The reflective optical sensor 200f according to the fifth embodiment is characterized by having light shielding walls 230f-0, 230f-1,..., 230f-7, 231f.

  These light shielding walls constitute openings that surround the light beams from the individual LEDs 211f-pq when viewed from the z direction.

  By providing such an opening, it is possible to prevent reflected light from the lens surface of the irradiation lens from entering the PD that should not be incident as flare light.

  Therefore, the surface state of the fixing belt can be detected with higher accuracy.

  The light shielding walls 230f-0, 230f-1,..., 230f-7, 231f constituting the opening can be integrally formed with the case 240f by resin molding.

  In each embodiment described above, the blinking of the plurality of LEDs constituting the irradiation optical system is described as “sequential lighting”.

  “Sequential lighting” is a lighting method in which the 28 LEDs of the irradiation system 1 to the irradiation system 7 are turned on and off one by one in a predetermined order.

  That is, the blinking of the light emitting part of the irradiation system is controlled so that the spot of the illumination light formed on the surface of the fixing belt as the test object is sequentially formed.

  The sequential lighting is effective for accurately specifying the position of the flaw on the surface of the fixing belt in the main scanning direction.

  For example, when the spot irradiated on the fixing belt is moved in the positive direction of the x direction by sequentially lighting the LEDs, the lighting is performed in the order of irradiation system 1 to irradiation system 7.

  As described above, in each irradiation system, the LEDs 221-pq are turned on / off in the order of 1 = 4, 3, 2, 1.

  When a series of these operations are repeated and all the LEDs are turned on / off, the lighting is sequentially completed with this as one cycle.

  The operation of the PD when the spot moves in the positive direction in the x direction will be described.

  For simplicity of explanation, it is assumed that 2 m PDs receive reflected light when any one LED is lit. m is an integer.

  The n-th LED is simply 211n, and when this LED 221n is lit, the reflected light is received by 2m PDs. Let 2m PDs be PD1, PD2,.

  Then, out of these 2m PDs, the first and second PD (first) and PD (second) are extracted from the ones with a large received light amount (output).

  These two PDs (first) and PD (second) are generally adjacent to each other, and the center position of these two PDs in the x direction is x = 0.

  Then, the remaining 2m−2 PD positions are x = 0 ± 1.51 × Pt with the PD arrangement pitch being Pt, and the 2m−2 PDs output the light quantity at these positions. .

  The output of each PD received and photoelectrically converted and amplified by the 2m PD1 to PD2m is sent to the state determination means 300 (see FIG. 2C) each time.

  In some cases, in order to increase the detection accuracy, it is possible to sequentially perform lighting over a plurality of cycles and perform an average value processing of detection results.

  Further, it is not necessary to use the total number of arrays: N (= 28) as the LEDs to be turned on / off, and some N ′ (≦ N) of them may be used.

  Sequential lighting has no crosstalk (a phenomenon in which one PD simultaneously receives reflected light from a plurality of light emitting units) as compared to the case where all the light emitting units are simultaneously turned on.

  Therefore, the detection accuracy of the detection result obtained for each light spot position in the main scanning direction can be improved.

  In all of the first to fifth embodiments described above, the lens array is manufactured by molding using an optical resin (polymer resin) having a refractive index of 1.5332.

  The reflective optical sensors of Embodiments 1 to 5 detect the surface state on the surface of the fixing belt, which is the test object, with the direction (main scanning direction) orthogonal to the moving direction of the surface as the x direction.

  FIG. 18A shows this case. The surface of the transfer belt denoted by reference numeral 61 moves in the y direction (sub-scanning direction), and the detection area A ′ by the reflective optical sensor is parallel to the x direction.

  The “sheet end position” in the figure is a portion where the end of the sheet (sheet-shaped recording medium) on which the toner image is fixed is located, and “striped scratches” are likely to occur in this portion.

  Therefore, the detection area A 'is set in this portion.

  In this case, the detection area A ′ may be “cylindrical surface wound around a roller”.

  On the other hand, FIG. 18B shows a case where the transfer belt surface 61 is planar and is set with the x direction (spot arrangement direction) inclined by 45 degrees with respect to the main scanning direction.

  18B, the detection area A ′ in the main scanning direction is shortened to 1 / √2 in the case of FIG. 18A, but the arrangement pitch of spots in the main scanning direction is also reduced to 1 / √2. it can.

  Therefore, the position resolution of the detection result can be increased as compared with the case of FIG.

  When the reflective optical sensor as in each of the above embodiments is mounted on the image forming apparatus described with reference to FIGS. 1 and 2, it is possible to detect in real time whether there is a flaw on the surface of the fixing belt.

  In addition, the position of the scratch and the width of the scratch can be detected.

  Even if the surface of the fixing belt fluctuates or the sensor mounting position shifts, the surface information can be detected while sufficiently maintaining the flaw detection area on the fixing belt.

  Therefore, it is possible to prevent image quality deterioration due to scratches.

  In the image forming apparatus, as shown in FIGS. 19A to 19C, the reflection type optical sensor of the present invention can be partially arranged in the vicinity of the edge of the small paper width.

That is, it is partially arranged at or near the position where the end of the small-sized sheet-like recording medium and the fixing belt contact.
In this way, even if the length of the detection area A ′ in the main scanning direction is shortened, the edge of the sheet width can be included in the detection area A ′.

If the detection area A ′ can be shortened, there is an advantage that the reflective optical sensor 200 can be downsized particularly in the main scanning direction.
The width of the “scratch” as surface information is about several hundred μm to several mm, and the variation range as the position of the scratch is about several mm.

Therefore, the detection area A ′ is preferably “about 5 mm to 15 mm in the main scanning direction”.
The image forming apparatus can use a plurality of sizes of paper such as A3, A4, and A5. In general, the largest number of sheets that can be passed is A3 vertical.

In that case, the “small paper width” refers to “paper size excluding A3 paper”.
If the image forming apparatus is capable of A2 portrait paper, paper sizes other than A2 paper are targeted.

  Further, since there are “two places at both ends” of the small-size sheet width end, one reflection type optical sensor can be arranged at each end of the sheet, that is, two in the main scanning direction.

  However, since the vertical streak caused by the end face of the paper generally occurs on both sides of the paper and there is no significant difference in the level of the scratch, it may be provided only on one side of the paper.

  Further, in the image forming apparatus, the reflection type optical sensor of the present invention may be enlarged in the main scanning direction as shown in FIG.

  That is, it is arranged over the entire length of the fixing belt.

  For example, in the case of an image forming apparatus capable of A1 longitudinal paper, the reflective optical sensor is enlarged in the main scanning direction so as to be able to illuminate the paper width ends of each size of A2 to A5 and B3 to B6.

  Thus, by sufficiently increasing the length of the reflective optical sensor, it is possible to prevent undetected scratches appearing at different locations on the fixing belt depending on the paper size.

  In the above description, the scratch on the surface of the fixing roller has been described as an object of detection of surface information by the reflective optical sensor.

  In the above description, the test object is a fixing belt as a fixing member. However, the test object for detecting surface information is not limited to this, and a semiconductor substrate, paper, or the like can be used.

  The surface state of the transfer belt described above can also be detected as surface information.

  Moreover, although the case where the number of the light emission part (LED) of the irradiation system corresponding to each irradiation lens was demonstrated as an example, it cannot be overemphasized that the number of the light emission parts which comprise an irradiation system is not restricted to this.

65Sa Surface of fixing belt (test object) 220a-1 to 220a-7 Irradiation lens
220aC Light receiving lens
211a-pq Light emitting part (LED)
212a Light receiver (PD)
Sa-1 spot

Japanese Patent Laid-Open No. 05-113739 JP 2011-185988 A

Claims (10)

In the reflection type optical sensor for detecting the surface information of the surface by irradiating the surface of the test object with light and receiving the reflected light from the surface,
An irradiation optical system in which two or more unit irradiation optical systems each including an irradiation system and an irradiation lens are arranged;
A light receiving system and a light receiving optical system including a light receiving lens,
The irradiation system of the unit irradiation optical system has two or more light emitting units,
The irradiation lens of the unit irradiation optical system is shared by the two or more light emitting units, and guides the light emitted from the two or more light emitting units to the surface of the test object, thereby setting the spot of irradiation light to 1 It is formed by shifting in the direction,
The light receiving system of the light receiving optical system has two or more light receiving parts,
The light receiving lens is shared by the two or more light receiving portions,
The reflected light that is irradiated onto the surface of the test object by each unit irradiation optical system of the irradiation optical system and reflected by the surface is received by the light receiving system via the light receiving lens of the light receiving optical system. Configured,
In addition, spots emitted from each of the light emitting units and irradiated on the surface are continuously arranged in one direction, and these spots are irradiated at different incident angles from adjacent unit irradiation optical systems. The reflective optical sensor is characterized in that the positional relationship between the light emitting unit and the irradiation lens in the irradiation optical system is adjusted so that there is an object to be emitted. The reflective optical sensor according to claim 1,
The spot emitted from each irradiation system and irradiated on the surface of the test object is focused on the test object in a focused state with respect to the direction orthogonal to the arrangement direction of the irradiation lens and the optical axis direction by the irradiation lens. A reflective optical sensor that irradiates a surface. The reflective optical sensor according to claim 1 or 2,
With respect to the arrangement direction of the irradiation lenses, the light emitted from each irradiation system is reflected by the surface of the test object and reaches the light receiving system at any position between the light emitting unit of each irradiation system and A reflective optical sensor characterized by satisfying a conjugate relationship. The reflective optical sensor according to any one of claims 1 to 3,
A reflection-type optical sensor, wherein the light-receiving lens is a cylindrical lens arranged with a direction without power parallel to a spot arrangement direction. The reflective optical sensor according to any one of claims 1 to 4,
A reflection-type optical sensor, wherein an irradiation lens and a light-receiving lens of an irradiation optical system are integrated. The reflective optical sensor according to any one of claims 1 to 5,
A reflection-type optical sensor characterized in that an opening is formed by a light shielding wall for each unit irradiation optical system of the irradiation optical system. The reflective optical sensor according to any one of claims 1 to 6,
A reflective optical sensor characterized in that the blinking of the light emitting part of the irradiation system is controlled so that illumination light spots formed on the surface of the test object are sequentially formed. The reflective optical sensor according to any one of claims 1 to 7,
A surface whose surface information is to be detected is used for an object that moves in a predetermined direction of movement parallel to the surface;
A reflection-type optical sensor that detects surface information such that an array direction of a plurality of spots is inclined with respect to the moving direction on a planar surface. In an image forming apparatus that forms a toner image by an electrophotographic process and fixes the toner image on the surface of a sheet-like recording medium by a fixing device to form an image.
The fixing device has an endless fixing belt,
An image forming apparatus using the reflective optical sensor according to any one of claims 1 to 8 as surface information detecting means for detecting surface information of the fixing belt. The image forming apparatus according to claim 9.
Reflective optical sensor
In the direction perpendicular to the advancing direction of the surface of the fixing belt within the surface of the fixing belt, the sheet is partially disposed at or near the position where the end of the small-sized sheet-shaped recording medium contacts the fixing belt. Or
Alternatively, image formation is characterized in that it is arranged over the entire longitudinal direction of the fixing belt in a direction orthogonal to the advancing direction of the surface of the fixing belt so as to correspond to various sizes of the sheet-like recording medium. apparatus.

Images