JP2013068971A - Toner information detection method, reflection-type optical sensor device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce toner consumption and light-emission energy of a light-emitting unit in detecting a position of a toner pattern or toner density without decreasing work efficiency of image formation.SOLUTION: A toner information detection method includes: a preliminary detection process for causing, with the use of radiating means having light-emitting units E1 to E9 and light-receiving means having light-receiving units D1 to D9, r(≤9) light-emitting units of the irradiating means to emit light to preliminarily detect position range information of a toner pattern YP1; and a main detection process for selecting and causing s(<r) light-emitting units of the radiating means to emit light on the basis of the detection result in the preliminary detection process to detect information relating to the position of the toner pattern and/or toner density.

Description

  The present invention relates to a toner information detection method, a reflective optical sensor, and an image forming apparatus.

  An image forming apparatus that forms an image using toner is widely used as an analog or digital “monochrome or color copier”, a printer, a plotter, a facsimile machine, and a multifunction printer (hereinafter abbreviated as “MFP”). It has been implemented.

  An image formed by such an image forming apparatus is a “toner image”. As is well known, in order to obtain a good image, the amount of toner used for developing an electrostatic latent image is appropriate. Must. Various development methods are known, such as a method using a “two-component developer containing toner and carrier” and a mono-toner development method using a developer composed only of toner. The amount of toner supplied to the developing unit where the latent image is developed is referred to as “toner density”.

When the toner density is too low, a sufficient amount of toner is not supplied to the electrostatic latent image, and the resulting toner image is an image with insufficient density.
On the other hand, when the toner density is too high, the density distribution of the image to be formed is biased toward the “high density side”, and the toner image is also difficult to see. As described above, in order to form an appropriate toner image, the toner density must be in an appropriate range.

  Further, in order to obtain a good toner image, it is necessary to accurately grasp the position of the toner image on an image bearing medium such as recording paper.

  For example, when a toner image formed on a photoconductive photoconductor is transferred and fixed on a recording paper to form an image, the toner image on the photoconductor is “a desired position on the recording paper (for example, the central portion)”. It needs to be transferred correctly.

  The “transfer to the proper position” of the toner image cannot be realized unless the “position with respect to the recording paper to be transferred” of the toner image on the photosensitive member is properly grasped.

  In addition, when a plurality of toner images having different colors are overlapped to form a multicolor image or a color image, it is necessary to grasp the position of each toner image having a different color and perform proper overlapping.

  If the positional relationship between the superimposed toner images cannot be adjusted properly, “registration misalignment where the image writing sides deviate from each other”, “magnification misalignment resulting in image length error”, and these are relative to each other between the color toner images. This causes various abnormal images such as “color shift” due to misalignment.

  Conventionally, for proper control of toner density and toner image position, a “toner pattern for toner density detection” and a “toner pattern for toner position detection” are formed and irradiated with detection light to change the reflected light. A method of detecting and detecting the toner density and position of a toner pattern is widely used. An optical device that irradiates a toner pattern with detection light and receives reflected light is called a “reflective optical sensor”.

  Various reflection type optical sensors have been proposed and known for a long time (Patent Documents 1 to 6).

  These conventionally known reflection type optical sensors include one or two light emitting units, or “three light emitting units (LEDs) having different wavelength characteristics”, and one or two for receiving reflected light. Light receiving part (photodiode or phototransistor).

  As described above, the LED is generally used as the light emitting unit. However, the detection light emitted from the LED is applied to the toner pattern for detecting the toner concentration or the toner position for detecting a spot having a size smaller than that of the toner pattern. Is irradiated.

  For example, the toner pattern is formed on the transfer belt and moves as the transfer belt rotates. In this specification, the direction in which the toner pattern moves is referred to as “sub-direction”, and the direction perpendicular to the sub-direction on the transfer belt is referred to as “main direction”. In the case where an electrostatic latent image visualized as a toner image is formed by “optical scanning”, the main direction corresponds to the main scanning direction in optical scanning, and the sub direction corresponds to the sub scanning direction.

  The toner pattern is written in an electrostatic latent image forming unit by optical scanning or the like, and is visualized by development to become a toner pattern. In the above case, the toner pattern is transferred onto the transfer belt, moved in the sub direction, and reflected by the reflective optical sensor. It moves to a detection part and is irradiated with the spot of detection light.

  The spot size of the detection light is usually about 2 to 3 mm in diameter.

Ideally, the “position in the main direction” where the spot of the detection light from the reflective optical sensor is irradiated is the “central part in the main direction” of the toner pattern.
However, when the mounting position of the optical scanning area and the reflective optical sensor in the electrostatic latent image forming unit “changes with time in the main direction” or the transfer belt meanders, the toner pattern and the reflective optical sensor The “positional relationship in the main direction” is not necessarily an ideal state.

  When the “positional relationship in the main direction” between the toner pattern and the reflective optical sensor is shifted, and the spot of the detection light is “extruded and projected” from the toner pattern, the reflected light received by the light receiving means is not appropriate. The toner density and position of the toner pattern cannot be detected properly.

As an example, the detection light is irradiated as one spot, the reflected light is received by one light receiving portion, the specular reflection light (corresponding to the reflection characteristic of the transfer belt surface) and the diffuse reflection light (to the reflection characteristic of the toner pattern) The case where the toner density is detected based on the difference between the two) will be described.
When the light receiving part is arranged so as to "receive regular reflection light on the surface of the transfer belt", when the spot of the detection light irradiates the toner pattern properly without "extruding" from the toner pattern, The amount of light received by the light receiving unit is "smaller than when receiving regular reflection light on the transfer belt surface", and the toner density of the toner pattern is properly detected based on the difference in the amount of received light from when receiving regular reflection light. it can.

  However, when the spot of the detection light is “exposed and irradiated outside the toner pattern”, a part of the spot is diffused and reflected by irradiating the part of the toner pattern. The detection light is regularly reflected by irradiating the “transfer belt surface having no toner pattern”. Accordingly, in this case, the amount of light received by the light receiving unit is larger than “when light diffusely reflected by only the toner pattern is received”.

  Such a “light reception result” can also occur in “a case where the toner amount is small” in the toner pattern. Therefore, in the above case, the toner density of the toner pattern is detected to be lower than actual. Become.

  When detecting the position of the toner pattern, generally, a threshold level is set to “intensity of specularly reflected light” received by the light receiving unit, and the toner pattern position is determined based on this threshold level.

  That is, since the “toner pattern is present” when the amount of received light is lower than the “set threshold level”, the light reception result described above changes in the detection signal, which adversely affects the correct detection of the toner pattern position.

  In order to avoid such a problem, conventionally, the spot of the detection light is “positioned in the toner pattern in the main direction” regardless of the existence of a deviation of the “positional relationship in the main direction” between the toner pattern and the reflective optical sensor. The width of the main direction of the toner pattern is set to a size of about 15 mm to 25 mm as described above, and the spot of the detection light protrudes outside the main direction of the toner pattern even if the above-mentioned “positional deviation” occurs. I was trying not to.

  When detecting the toner density, the width in the sub-direction of the toner pattern is sufficiently larger than the spot size of the detection light so that sufficient diffuse reflection is generated from the toner pattern.

  By the way, in an image forming apparatus, particularly a color image forming apparatus, detection of toner density and toner pattern position using a reflective optical sensor and a toner pattern is performed so that the image forming process can be optimized and “high image quality can be ensured / maintained”. However, since it is performed separately from the output of the image to be formed, the “original image forming process” cannot be performed while the toner density and position of the toner pattern are being detected.

  If the electrostatic latent image to be a toner pattern is written by optical scanning, the time for writing the optical scanning pattern increases in proportion to the size of the toner pattern, which causes a reduction in work efficiency for original image formation. Become.

  Further, the toner that forms the detection toner pattern is consumed as “non-contributing toner” that does not contribute to the original image formation, and the consumption amount of the non-contributing toner increases in proportion to the size (area) of the pattern. That is, the conventionally known detection methods have a problem that it is difficult to improve work efficiency and a problem that the consumption of non-contributing toner is large.

  According to the present invention, when adjusting the image forming apparatus for maintaining the image quality, the original image forming work efficiency is not lowered, and the toner consumption during the adjustment of the image forming apparatus is reduced. It is an object to reduce the emission energy of the light emitting unit.

  The toner information detecting method according to the present invention is “in the image forming method for forming an image with toner, one or more predetermined toner patterns are formed on the surface of the supporting member moving in a predetermined sub-direction, and the detection light is detected on the supporting member by the irradiation means , The light reflected by the support member and / or the toner pattern is received by the light receiving means, and the information on the position of the toner pattern and / or the toner density based on the difference between the reflection characteristics of the support member and the toner pattern with respect to the detection light Is a toner information detection method for detecting ”.

The “image forming method for forming an image using toner” is an image forming method executed in the above-described image forming apparatus such as a copying machine, a printer, a plotter, a facsimile machine, and an MFP, and “forms an electrostatic latent image”. And “process for visualizing the formed electrostatic latent image with toner”.
The electrostatic latent image is formed by performing an “exposure process such as optical scanning” on the uniformly charged photoconductive latent image carrier.

The “toner pattern” is a “toner image” for use in detecting toner information, and is “an electrostatic latent image formed as a toner pattern that has been visualized as a toner image” and is supported when detected. It is formed on the member. In other words, the toner pattern is formed on the support member, and is brought to the detection unit (the portion where the detection light is irradiated and the reflected light is received) by the “movement in the sub direction” of the support member.
The “electrostatic latent image to be a toner pattern” can be formed by exposing an image having a predetermined density pattern, or can be formed by writing by optical scanning.

  The “support member” is a member that holds the toner pattern and moves in the sub-direction when toner information is detected as described above. Specifically, for example, “an electrostatic latent image is formed”. It can be “a latent image carrier itself” or “a transfer belt or intermediate transfer belt used for transferring a toner image”. In some cases, for example, a toner pattern can be transferred to recycled paper or transfer paper using one side, and toner information can be detected for the transferred toner pattern.

  “Toner pattern is predetermined” means that the toner pattern has a fixed shape, that is, “has a certain shape”.

  The “toner information” to be detected is information relating to the position of the toner pattern and / or the toner density. That is, the toner information to be detected is any one of the three types of information relating to the position of the toner pattern, information relating to the toner density in the toner pattern, and information relating to the position and toner density of the toner pattern.

The toner information detection method according to claim 1 has the following characteristics.
In other words, the means used for detecting toner information includes an irradiating means and a light receiving means.
“Irradiation means” means that M (≧ 3) light emitting portions for detecting light that radiate detection light can be irradiated at M spots with detection light spots on the support member, and in a direction orthogonal to the sub-direction. The adjacent spots are arranged in one direction intersecting with the sub direction so that the size of the toner pattern in the orthogonal direction is equal to or less than the size of the toner pattern.

  The “light receiving means” is an irradiation means, and N (≧ 3) light receiving portions are made to correspond to the irradiation means so that the reflected light of the detection light from the support member and / or the toner pattern can be received, and Arranged in one direction to face the support member.

  The N light receiving parts “can receive the reflected light of the detection light by the support member and / or the toner pattern” means that when the detection light is irradiated, the N light receiving parts are reflected light from the support member, toner This means that it is possible to receive both reflected light from the pattern and reflected light from the support member and the toner pattern.

The toner information detection method according to the first aspect includes a preliminary detection step and a main detection step.
The “preliminary detection step” is a step of preliminarily detecting the position range information of the toner pattern by causing the r (≦ M) light emitting portions in the irradiation unit to emit light.
That is, in the preliminary detection step, all of the M light emitting units constituting the irradiation unit or r (<M) light emitting units included in the M light emitting units emit light. Then, “position range information” of the toner pattern on the support member is detected.

  “Position range information” of the toner pattern is information indicating “rough range mainly in the main direction” on the support member where the toner pattern is located.

  In the “main detection step”, information on the position of the toner pattern and / or the toner density is detected by selecting and emitting s (<r) light emitting portions that emit light in the irradiation unit based on the detection result in the preliminary detection step. It is a process to do. That is, “s” is always smaller than “M”.

  That is, after the rough position on the support member of the toner pattern is detected as “position range information” in the preliminary detection step, the detection range is changed to the detection range by “s (<r) light emitting units” in this detection step. Narrow down to detect. The detection target at this time is “information on the position and / or toner density of the toner pattern”. The toner information is arithmetically detected based on the outputs of the N light receiving portions of the light receiving means.

  The toner pattern used for “detection of position range information” in the preliminary detection process may be different from the toner pattern used for detection in the main detection process. A preliminary detection step can also be performed using a part of the above.

The r light emitting units that emit light in the preliminary detection step may emit light simultaneously or sequentially. Similarly, the s light emitting units that emit light in the present detection process may emit light simultaneously or sequentially.
Sequentially emitting r or s light emitting units means that the light emitting units are individually blinked sequentially. In this case, among the r light emitting units, there may be “a plurality of flashing units simultaneously”.

To supplement the description, in the above description, “one direction intersecting with the sub direction” includes a direction orthogonal to the sub direction, that is, “main direction”.
“Between adjacent spots in the direction orthogonal to the sub-direction” refers to “an array of M spots in one direction” formed on the surface of the support member by the detection light emitted from each of the M light-emitting portions. When projected in a direction orthogonal to the direction, that is, the “main direction”, it means between adjacent spots in this projected state.

  “Between spots” is not the distance between the centers of the spots, but refers to the “distance in the main direction from edge to edge” of adjacent spots when adjacent spots do not overlap each other in the projected state.

More specifically, for example, it is assumed that M light emitting portions are arranged at a pitch of 3 mm in the main direction, and the “detection light spot” formed by each light emitting portion is a circle having a diameter of 2 mm.
At this time, on the support member, M spots are arranged at a pitch of 3 mm in the main direction, but between adjacent spots is “1 mm in the main direction”, and this 1 mm region is irradiated with detection light. There is nothing.

  However, if the size of the toner pattern in the main direction is larger than 1 mm, which is “between adjacent spots”, at least one of the toner patterns when passing through the “region where the spots of detection light are arranged”. The part is always irradiated with a spot of detection light.

  Therefore, in this case, in order for the “toner pattern to be irradiated by the spot of the detection light”, the size of the toner pattern in the main direction needs to be slightly larger than 1 mm, and 15 mm to 25 mm in the main direction is conventionally required. The size of the toner pattern can be effectively reduced.

Since the condition between the adjacent spots in the direction orthogonal to the sub direction is “below the size of the toner pattern in the main direction”, the distance between the adjacent spots may be smaller than 1 mm in the above case. Adjacent spots may overlap each other in the main direction. In this case, “between adjacent spots” is a negative value.
When adjacent spots overlap each other in the main direction, the area irradiated with the detection light spot is a “continuous area in the main direction”, so the size of the toner pattern in the main direction is In principle, it can be made as small as possible.

  Even if the size of the spot itself is “smaller than the length in the main direction of the toner pattern”, if the pitch in the main direction of the adjacent spot is “smaller than the length in the main direction of the toner pattern”, Naturally, the distance between adjacent spots is “smaller than the length of the toner pattern in the main direction”, so that the toner pattern can be reliably irradiated with the detection light.

  When the detection light is irradiated to the support member, it is reflected by the “support member and / or toner pattern”, and the reflected light is received by the light receiving means. The light receiving means has three or more light receiving portions, and the amount of light received by each light receiving portion changes according to the positional relationship between the spot of the detection light and the toner pattern. Therefore, the position of the toner pattern and the toner density can be detected based on the outputs of these three or more light receiving portions.

As conventionally known, when a “toner pattern” is irradiated with detection light, the detection light is “diffuse reflected”. On the other hand, for example, when the support member is a photoconductive latent image carrier, the support member surface is smooth and the detection light is regularly reflected.
Therefore, when the detection light is irradiated on the surface of the support member and when the toner pattern is irradiated, there is a difference of “regular reflection and diffuse reflection” in the reflection characteristics. Therefore, the toner information related to the toner pattern can be detected by the outputs of three or more light receiving portions.

  In addition, when the support member is a transfer belt or an intermediate transfer belt, the surface of the support member may be “close to a mirror surface and substantially regularly reflect detection light” or “diffuse and reflect detection light”. Even if the surface of the support member diffuses and reflects the detection light, if there is a difference in reflection characteristics between the diffuse reflection of the detection light on the surface of the support member and the diffuse reflection due to the toner pattern, the detection light is diffused. When the light is reflected and received by multiple light receiving units, the distribution of the amount of received light distributed to the multiple light receiving units is different between the diffuse reflection on the support medium and the diffuse reflection by the toner pattern, so the toner information can be detected. It is.

  As described above, the number of light emitting parts constituting the irradiation means: M is 3 or more, and the number of light receiving parts constituting the light receiving means: N is also 3 or more. M and N may be equal to each other (M = N) or may be different (M ≠ N). It is also possible that M> N or N> M.

  The “irradiating means” can be configured by using LEDs as light emitting units and arranging three or more LEDs in one direction. In this case, if the LED has a “lens function for condensing the emitted light”, the LEDs are arranged, and the emitted light forms “a spot of a desired size on the support member as detection light”. Thus, the positional relationship with respect to the support member may be determined.

  As the light emitting section, an “LED array” having three or more light emitting sections can be used. In this case, an appropriate condensing optical system that condenses the light emitted from the LED light emitting unit on the support member can be combined to form an irradiation unit.

  A PD (photodiode) can be used as the “light receiving portion of the light receiving means”, but a PD array in which three or more PD elements are arranged in an array can be used as the light receiving means.

  In the preliminary detection step or the main detection step, when the light emitting unit is caused to sequentially emit light (flash), the toner pattern that is the detection target of the preliminary detection or the main detection “passes the detection light irradiation region in the sub direction. It is necessary to stop the flashing of the r or s light emitting units for detection within “time”.

  In such a case, the r light emitting units and / or the s light emitting units are sequentially caused to emit light within the “time when the toner pattern passes through the detection light irradiation region in the sub direction”.

  In the toner information detection method according to the first or second aspect, “r (<M) light emitting portions capable of detecting the position range information of the toner pattern are selected in the preliminary detection step” (claim 3).

  That is, when M light emitting portions in the irradiating means are caused to emit light at the same time, the support member is simultaneously irradiated with M spots of detection light. At this time, the “main” is irradiated with M spots. The irradiation range in the direction (hereinafter referred to as “main direction detectable range” for convenience) ”generally refers to the position of the toner pattern even if the position of the toner pattern formed on the support member varies in the main direction. Is set to be sufficiently large with respect to the size of the toner pattern to be detected in the main direction so as not to protrude from the main direction detectable range.

  If the position of the formed toner pattern in the main direction protrudes from the main direction detectable range, the toner pattern is adjusted so that the toner pattern does not protrude from the main direction detectable range. And a preliminary detection step and a main detection step may be performed.

If the toner pattern formed on the support member does not protrude from the main direction detection range, and if the toner pattern forming position is known to some extent “the range within the main direction detection range”, then the preliminary detection step If r (<M) light emitting units capable of irradiating a range that can cover the “range fluctuating within the main direction detection range” is selected, all M light emitting units emit light during the preliminary detection process. In particular, if “when the light emitting units are sequentially blinked”, r blinks can be completed in a shorter time than when all the M light emitting units are blinked. Can be shortened.
As described above, the number of toner patterns formed on the support member is one or more, and the toner pattern used for detection of position range information in the preliminary detection process is the same as the toner pattern used for detection in the main detection process. The toner information detection method according to any one of claims 1 to 3, wherein "the toner pattern dedicated to the preliminary detection step for detecting the position range information by the preliminary detection step" is used as the support member. It is preferable to form on the surface.

  In this case, the toner pattern used for detecting the position information and toner density information of the toner pattern is formed separately from the toner pattern dedicated to the preliminary detection process. That is, in this case, a plurality of toner patterns are formed on the support by using the toner pattern dedicated to the preliminary detection process and the toner pattern for the main detection process, and the surface of the support is displaced in the sub-direction. Since it is performed prior to the detection step, the toner pattern dedicated to the preliminary detection step is formed at the “sub-direction head” with respect to other toner patterns (toner patterns for the main detection step).

  On the contrary, in the toner information detecting method according to any one of claims 1 to 3, the toner pattern for detecting information on the position of the toner pattern and / or the toner density in the main detecting step is “position in the preliminary detecting step”. It can also serve as a toner pattern for detecting range information ”. The number of toner patterns will be described later according to a specific embodiment.

  The “toner information as a detection target” in the toner information detection method according to any one of claims 1 to 5 can be at least “position information on the support member of the toner pattern” (claim 6). In this case, the toner information as a detection target is “toner density and position information, and in this detection step, the number of s light-emitting portions to emit light is the position information when the detection target is the toner density. It can be made different depending on the case (Claim 7).

  In the toner information detection method according to claim 6 or 7, when “toner information as a detection target is position information”, the number of light emitting units to emit: s = 1 can be set (claim 8). Further, in the toner information detection method according to any one of claims 6 to 8, when "the toner information as the detection target is the toner density", it is preferable that the number of light emitting sections to emit: s> 1 ( Claim 9).

  A reflection type optical sensor device according to the present invention is a reflection type optical sensor device used for carrying out the toner information detection method according to any one of claims 1 to 9, wherein the irradiation unit, the light receiving unit, and the control Means (claim 10).

  The “irradiation means” is formed by arranging M (≧ 3) light emitting units that can blink independently or simultaneously in one direction. The irradiating means can be configured by arranging M independent LED elements, or an LED array in which M LED light emitting units are arrayed can be used.

  The “light receiving means” is formed by arranging N (≧ 3) light receiving portions in one direction corresponding to the irradiation means. The light receiving means can be configured by arranging N independent PDs, or a PD array in which N PD light receiving units are arranged and integrated can be used.

  The “control means” is means for controlling the light emission of the M light emitting units according to the preliminary detection process and the main detection process. The control means can be configured as a microcomputer or a CPU.

  The image forming apparatus according to the present invention is an “image forming apparatus that forms an image using toner”, and includes the reflective optical sensor device according to claim 10 as a reflective optical sensor device for detecting toner information. It is characterized (claim 11).

  The image forming apparatus according to the eleventh aspect of the present invention may be “the image to be formed is a multicolor image or a color image with a plurality of types of toners having different colors, and toner information for each color is detected” ( Claim 12).

As described above, the lower limit of M and N is 3, but the upper limit can be appropriately determined depending on the practical size of the reflective optical sensor for detecting toner information. The number: M and N depend on the arrangement pitch if the light emitting unit and the light receiving unit are arranged in a line, and are the number obtained by dividing the detection area covered by the reflective optical sensor in the main direction by the arrangement pitch. become. For example, if a detection area of 25 mm is covered in the main direction, M = N = 50, assuming that the light emitting units and the light receiving units are arranged at a pitch of 0.5 mm.
If the number of light receiving parts is more than twice that of the light emitting parts (N = 2 × M), or if the detection area to be covered becomes large, M and N become large. As practical values, M and N are about several tens to several hundreds.

  As described above, the light emitting units r and s in the M light emitting units constituting the irradiating means may be made to “blink simultaneously or sequentially”. It may be divided into several groups and blinked sequentially from one end side in the arrangement of the light emitting units. “Group sequential blinking” will be described later.

  2. The toner information detection method according to claim 1, wherein when the toner pattern for toner density detection is a “rectangular pattern having a width in the main direction and the sub direction”, m (≧ 3) light emitting portions and , N (≧ 3) light-receiving portions constitute a light-emitting portion / light-receiving portion pair, and the light-emitting portion / light-receiving portion pair is arranged in one direction parallel to or intersecting with the main direction as P (≧ 2) pairs. Each light emitting unit is configured such that the corresponding light emitting unit emits light at the same time in each light emitting unit / light receiving unit pair of the irradiation unit within a time during which the rectangular pattern passes through the detection light irradiation region in the sub direction. Can be emitted sequentially.

As for the “toner pattern”, the toner pattern is a toner image formed in a fixed shape so as to detect the toner information. When the toner density is detected as the toner information, “to represent a representative toner density”. In other words, the toner image may be formed as “a plurality of toner images” as described later.
In the case where a plurality of toner images are formed as described above, each toner image is a toner pattern. A set of the plurality of toner images may be referred to as a “toner pattern”. In addition, the toner pattern of the plurality of toner images may be “formed as a single pattern as a whole” (in this case, the toner color, toner density, and position of the toner image within the single toner pattern). Is changing in the secondary direction).

  As described above, according to the present invention, a novel toner information detection method, a reflective optical sensor used to implement this method, and an image forming apparatus that implements the toner information detection method using this reflective optical sensor are provided. realizable.

As will be described in detail below, according to the present invention, since the size of the toner pattern used for toner information detection can be effectively reduced as compared with the conventional one, the time required for toner information detection can be shortened. Work efficiency for image formation can be improved.
Further, since the size of the toner pattern can be reduced, the consumption of non-contributing toner can be reduced. Furthermore, it is possible to reduce the number of blinks of the light emitting unit, and energy saving for toner information detection can be achieved.

It is a figure for demonstrating one form of an image forming apparatus. It is a figure for demonstrating the detection of the toner pattern by a reflection type optical sensor. It is a figure for demonstrating the detection of the toner pattern by a reflection type optical sensor. It is a figure for demonstrating the output pattern of the light-receiving part of a reflection type optical sensor. It is a figure for demonstrating another example of the output pattern of the light-receiving part of a reflection type optical sensor. FIG. 6 is a diagram for explaining a reflection characteristic and a regular reflection contribution by a toner pattern in the output pattern of FIG. 5. It is a figure for demonstrating the normalized reflection contribution and diffuse reflection contribution. It is a figure for demonstrating the output pattern of a reflection type optical sensor. It is a figure for demonstrating the example of an arrangement | sequence of the light emission part and light-receiving part of a reflection type optical sensor. It is a figure for demonstrating the example of another arrangement | sequence of the light emission part and light-receiving part of a reflection type optical sensor. It is a figure for demonstrating the example of another arrangement | sequence of the light emission part and light-receiving part of a reflection type optical sensor. It is a figure for demonstrating the other example of a reflection type optical sensor. It is a figure for demonstrating the other example of a reflection type optical sensor. It is a figure for demonstrating the other example of a reflection type optical sensor. It is a figure for demonstrating the other example of a reflection type optical sensor. It is a figure for demonstrating a reflection type optical sensor apparatus.

Embodiments of the invention will be described below.
First, an embodiment of an image forming apparatus will be described with reference to FIG.
The image forming apparatus shown in FIG. 1 forms a “color image”. A color image is formed by toners of four colors of yellow: Y, magenta: M, cyan: C, and black: K.
In FIG. 1, a portion indicated by reference numeral 20 is an “optical scanning device”. As the optical scanning device 20, various publicly known devices can be used.
Reference numerals 11Y to 11K denote drum-shaped photoconductors that are “photoconductive latent image carriers”, and the photoconductor 11Y is used to form a toner image with yellow toner, and the photoconductors 11M, 11C, and 11K are respectively Used to form a toner image with magenta toner, cyan toner, and black toner.

That is, the optical scanning device 20 performs “image writing by optical scanning” on the four photoconductors 11Y, 11M, 11C, and 11K.
Each of the photoconductors 11Y to 11K is rotated at a constant speed in the clockwise direction, is uniformly charged by the charging rollers TY, TM, TC, and TK that form a charging unit, and receives “respectively corresponding optical scanning” by the optical scanning device 20, and yellow. , Magenta, cyan, and black color images are written to form a corresponding electrostatic latent image (negative latent image).

  These electrostatic latent images are reversed and developed by developing devices GY, GM, GC, and GK, respectively, and a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on the photoreceptors 11Y, 11M, 11C, and 11K, respectively. Is done.

  These color toner images are transferred to a recording sheet (not shown) (transfer paper or a plastic sheet for an overhead projector). A transfer belt 17 is used for transfer.

  The recording sheet is fed from a “sheet placing portion (not shown)” provided below the transfer belt 17, supplied to the upper peripheral surface on the right side of the transfer belt 17 in FIG. 1, and electrostatically attracted to the transfer belt 17. The transfer belt 17 is conveyed counterclockwise by rotating counterclockwise.

  While being conveyed in this manner, the recording sheet is transferred with the yellow toner image from the photoreceptor 11Y by the transfer device 15Y, and the magenta toner image from the photoreceptors 11M, 11C, and 11K by the transfer devices 15M, 15C, and 15K, respectively. A cyan toner image and a black toner image are sequentially transferred.

In this way, a yellow toner image to a black toner image are superimposed on the recording sheet to compose a color image synthetically.
On the recording sheet, the carried color image is fixed by the fixing device 19 and discharged out of the device.

  Instead of the above, an intermediate transfer belt is used, and the four color toner images are superimposed on the intermediate transfer belt and transferred to obtain a color image. This color image is transferred to a recording sheet and fixed. You may make it do.

  FIG. 2 illustrates the positional relationship between the toner pattern formed on the transfer belt 17 as a “support member” and the reflective optical sensors OS1 to OS4.

  In the image forming apparatus shown in FIG. 1, image writing is performed by optical scanning as described above, and the main scanning direction in the optical scanning is a direction orthogonal to the drawing of FIG. 1, and this direction is the “main direction”.

In FIG. 2, the vertical direction is the main direction and corresponds to the “direction orthogonal to the drawing” in FIG.
Further, the leftward direction in the left-right direction in FIG. 2 is the sub direction, which is the moving direction of the surface of the transfer belt 17 (indicated by an arrow A in the figure).

  In FIG. 2, symbols YP1 to KP1, PP1 to PP4, and DP1 to DP4 indicate toner patterns used for toner information detection. The toner patterns YP1 to KP1 are each formed as a single pattern, but the toner patterns PP1 to PP4 and DP1 to DP4 are each formed as a “collection of a plurality of toner patterns”.

  To explain these toner patterns, the toner patterns YP1 to KP1 are “toner patterns exclusively used for the preliminary detection step”, and “other toner patterns PP1 to PP4 and DP1 to DP4” are printed on the surface of the transfer belt as a support member. It is formed at the “head in the sub direction”.

  The toner pattern YP1 is formed of yellow toner, and the toner patterns MP1 to KP1 are formed of magenta toner, cyan toner, and black toner, respectively.

  Each of the toner patterns PP1 to PP4 is composed of “four line patterns parallel to the main direction and four line patterns inclined with respect to the main direction”, and the positions of the respective color toner images are set in the main direction and the sub-direction. This is for detecting position information at four locations in the main direction with respect to the direction.

  In each of these toner patterns PP1 to PP4, the line pattern forms a pair of “one parallel to the main direction and one inclined with respect to the main direction”, and each pair is yellow, magenta, cyan, and black. Formed with each toner.

The toner patterns DP1 to DP4 are patterns for detecting the density of each color toner. The toner pattern DP1 is formed of yellow toner, and the toner patterns DP2 to DP4 are formed of magenta toner, cyan toner, and black toner, respectively. Yes.
In the toner patterns DP1 to DP4, a plurality of toner patterns having different densities (five types of patterns in the drawing) are arranged in an “adjacent direction in the sub direction” by the four color toners.
That is, the toner pattern DP1 is a pattern for detecting the density of yellow toner, and the toner patterns DP2, DP3, and DP4 are patterns for detecting the density of magenta toner, cyan toner, and black toner, respectively.

As for these toner patterns, “electrostatic latent images to be toner patterns” formed by being individually written on the photoconductors 11Y to 11K by the optical scanning device 20 shown in FIG. The toner image is reversely developed by GC and GK to form a toner image, which is further directly transferred onto the surface of the transfer belt 17.
As described above, in the embodiment being described, the transfer belt 17 is a “support member”, and hereinafter, the transfer belt 17 is also referred to as a “support member 17”. The toner pattern is formed on the transfer belt 17 as a support member, and moves in the “sub-direction” by the rotation of the transfer belt 17, and toner information is detected by the reflective optical sensors OS 1 to OS 4.

  Various toner patterns formed on the transfer belt 17 are removed from the surface of the transfer belt 17 by a cleaning device (not shown) on the right side of the reflective optical sensors OS1 to OS4 in FIG. 1, that is, on the downstream side of these sensors. .

  Here, taking toner patterns YP1 and DP1 formed by yellow toner as an example, these are both formed as a “electrostatic latent image developed by yellow toner” on the same photoreceptor 11Y by a series of optical writing. As shown in FIG. 2, the central portion in the main direction of the toner pattern YP1 and the central portion in the main direction of the toner pattern DP1 can be formed to coincide with each other. The positional relationship between the other toner patterns MP1 to KP1 and DP2 to DP4 is the same.

  As a modification, for example, the toner patterns DP2 to DP4 are formed “upstream in the sub direction” after the toner pattern DP1 of FIG. 2 so that the four toner patterns DP1 to DP4 are continuous in the sub direction. These can be sequentially subjected to toner density detection by the reflective optical sensor OS1. In this case, for example, the reflection type optical sensor OS4 is omitted, the formation of the toner pattern KP1 is omitted, and the three reflection type optical sensors OS1 to OS3 are used at three locations in the main scanning direction. CP1 and position detection patterns PP1 to PP3 may be detected.

  In the above, an example in which the toner pattern to be detected is “formed on the transfer belt 17 for conveying and transferring the recording sheet” has been described. However, depending on the form of the image forming apparatus, a photosensitive member as a latent image carrier Alternatively, each of the toner patterns formed on the intermediate transfer belt (or intermediate transfer member) can be detected by a reflective optical sensor.

Hereinafter, detection of “toner information” using a reflective optical sensor and a toner pattern will be described through embodiments.
In FIG. 3A, the symbol OS1 indicates the reflection type optical sensor described above. Since the four reflective optical sensors OS1 to OS4 described above are structurally identical, the detection by the reflective optical sensor OS1 will be described as an example.

  In FIG. 3A, the vertical direction is the “main direction”, and the leftward direction in the left-right direction is the “sub direction”.

As shown in FIG. 3A, the reflective optical sensor OS1 includes light emitting portions E1 to E9 (M = 9) for radiating detection light arranged at regular intervals at a predetermined pitch in parallel to the main direction. In addition to “irradiating means”, light receiving portions D1 to D9 (N = 9) that receive reflected light from the support member / toner pattern are arranged in parallel at a predetermined pitch in parallel to the main scanning direction to be “light receiving means”. These irradiating means and light receiving means are made to correspond to each other and integrally assembled to an appropriate housing.
The housing is arranged in a predetermined positional relationship at “a position below the transfer belt 17” shown in FIG.

  The light-emitting portions E1 to E9 that form the irradiation means and the light-receiving portions D1 to D9 that form the light-receiving means are located at the same position in the main direction, and as shown in FIG. When the surface of the transfer belt 17 is irradiated, the reflected light from the transfer belt 17 is incident on the light receiving portions D1 to D9 corresponding to the light emitting portions, that is, the light emitting portions Ei (i = 1 to 9) are set. The positional relationship is determined such that when the light is emitted, the reflected light from the transfer belt 17 enters the light receiving portion Di. Therefore, the arrangement pitch of the light receiving parts D1 to D9 is equal to the arrangement pitch of the light emitting parts E1 to E9.

  Here, the number of light emitting units and light receiving units is set to M = N = 9, but this is for the sake of simplicity of explanation, and practically, as described above, M and N are about several tens to several hundreds ( For example, it is common to take a value of 50 to 500).

  For the sake of concreteness of description, the surface of the transfer belt 17 is smooth, and “regular reflection light” on the surface of the transfer belt of the detection light emitted from each light emitting portion Ei is incident on the corresponding light receiving portion Di. It shall be.

  Therefore, in FIG. 3B, the reflected light incident on the light receiving portions D <b> 1 to D <b> 9 is regular reflected light from the surface of the transfer belt 17.

The light emitting units E1 to E9 are specifically LEDs, and the light receiving units D1 to D9 are specifically PDs (photodiodes).
The arrangement pitch of the light emitting portions E1 to E9 is such that the detection light emitted from each light emitting portion irradiates the surface of the transfer belt 17 as nine spots arranged in the main scanning direction, and the toner pattern YP1 is between adjacent spots. , PP1 and DP1 are set to be smaller than the “width in the main direction”.

In the example shown in FIG. 3A, the size of the spot formed on the surface of the transfer belt 17 by the detection light emitted from the light emitting portions E1 to E9 is the pitch of the light emitting portions E1 to E9 (as an example). Smaller than 0.5 mm (for example, 0.3 mm), and nine spots are arranged “adjacent to each other in the main direction” on the transfer belt 17.
The toner pattern YP1 dedicated to the preliminary detection process is formed so that the “size in the main direction” is equal to the pitch (0.5 mm) of the light emitting portions Ei.
At this time, the distance between adjacent spots in the main direction is 0.2 mm, which is smaller than the size of the toner pattern YP1 in the main direction: 0.5 mm.

The toner patterns YP1, PP1, and DP1 are formed in this order from the downstream side in the sub direction toward the upstream side.
That is, the toner pattern YP1 dedicated to the preliminary detection process is formed at the head in the sub direction in the toner pattern row, and the other toner patterns PP1 and DP1 are formed as the surface of the transfer belt 17 as the support member is displaced in the sub direction. Prior to this, the detection area of the reflective optical sensor OS1 is approached.
The toner pattern YP1 has a “time when it is formed”, and the time it takes to reach the detection region after the formation is substantially determined. Therefore, the light emitting units (LEDs) E1 to E9 are controlled to blink at an appropriate timing when the toner pattern YP1 approaches the detection area.

The flashing of the light emitting unit is sequentially performed from the light emitting unit E1 toward the light emitting unit E9 (r = 9).
That is, first, the light emitting unit E1 is turned on and turned off, and then the light emitting unit E2 is turned on and turned off. Next, the light emitting unit E3 is turned on / off, and the light emitting unit E4, the light emitting unit E5, the light emitting unit E6, the light emitting unit E7, the light emitting unit E8, and the light emitting unit E9 are sequentially turned on / off.
The light emitting units E1 to E9 are repeatedly turned on / off at high speed. Therefore, the surface of the transfer belt 17 is “repeatedly scanned in the main direction” with nine spots of detection light. This is hereinafter referred to as “spot scanning with detection light”.

As described above, when the surface of the transfer belt 17 is smooth and the detection light is irradiated to the portion where the toner pattern is not formed, the reflected light is regular reflected light.
For the sake of simplicity of explanation, the light receiving parts D1 to D9 are arranged such that when the detection light from the light emitting part Ei (i = 1 to 9) is irradiated to a part other than the toner pattern, the light receiving parts Di (i = 1 to 9). Assume that only the regular reflection light of the detection light from the light emitting unit Ei is received.

  Of course, depending on the configuration of the reflective optical sensor, when the detection light from the light emitting portion Ei (i = 2 to 8) is irradiated to a portion other than the toner pattern, the light receiving portion Di and Di− that is the light receiving portion adjacent to the light receiving portion Di. The three light receiving units 1 and Di + 1 (i = 2 to 8) may receive only the specularly reflected light of the detection light from the light emitting unit Ei, or may receive more light receiving units. However, here, for the sake of simplicity of explanation, it is assumed that the “regularly reflected light on the surface of the support member” of the detection light from the light emitting portion Ei is received only by the light receiving portion Di.

Under such conditions, for example, when the central portion of the toner pattern YP1 in the main direction is at the “position irradiated with the spot of the detection light from the light emitting portion E5”, the light emitting portions E1, E2, E3, E4, E6, The detection lights emitted from E7, E8, and E9 are regularly reflected on the surface of the transfer belt 17, and are received by the light receiving portions D1, D2, D3, D4, D6, D7, D8, and D9, respectively.
On the other hand, when the light emitting portion E5 is turned on and the detection light irradiates the toner pattern YP1, the detection light is regularly reflected and diffusely reflected by the toner pattern YP1, as shown in FIG.
While the regular reflection light component received by the light receiving unit D5 is reduced by the influence of diffuse reflection, the diffuse reflection light component is also received by the other light receiving units D1 to D9.

Looking at the outputs of the light receiving parts D1 to D9 in this state where the light emitting part E5 emits light, the amount of light received by the light receiving part D5 corresponding to the light emitting part E5 is low, and the other light receiving parts Di (i ≠ 5) The output is non-zero.
Depending on the configuration of the reflective optical sensor, the light receiving unit (such as the light receiving unit D1 or D9) far away from the light receiving unit D5 may not receive diffusely reflected light. It shall be able to receive light.
It is essential that the amount of light received by the light receiving portion D5 is “lower when the toner pattern YP1 is present than when there is no toner pattern YP1”, and the amount of light received by the other light receiving portions is not a problem.
From the result of the light receiving output of the light receiving part Di (i = 1 to 9), it can be seen that the toner pattern YP1 is at the position of the light emitting part E5 in the main direction.
When the toner pattern YP1 is between the light emitting units E5 and E6 in the main direction, the output of the light receiving unit D5 is low when the light emitting unit E5 is lit, and when the light emitting unit E6 is lit, the output of the light receiving unit D6. The output is also low.
Accordingly, it can be seen that the toner pattern YP1 is between the light emitting portions E5 and E6 in the main direction. At this time, if the output of the light receiving unit D5 is smaller than the output of the light receiving unit D6, it is understood that the toner pattern YP1 is on the “side closer to the light emitting unit E5”.

  In this way, during the time when the toner pattern YP1 dedicated to the preliminary detection process moving in the sub-direction passes through the detection area of the reflective optical sensor OS1, nine (r = 9) light-emitting portions “at least 1 in the main direction”. By performing spot scanning once, it is possible to select which light emitting portion Ei (i = 1 to 9) detects the reflected light of the toner pattern YP1.

This is the “preliminary detection step”.
In the above example, the case where the number of “sequentially flashing light emitting units”: r is M in the preliminary detection step has been described. However, the formation position of the toner pattern YP1 may be “fluctuated greatly in the main direction”. If it is known in advance that it is not in the spot position of the detection light from the light emitting parts E1 and E9 at the end of the reflective optical sensor OS1, the number: r = M−2 (light emitting parts E2 to E2). If it is known that it is in the arrangement region of the light emitting parts E3 to E7, the number of light emitting parts to be blinked: r = M−4 (light emitting part) It is also possible to blink E3 to E7.)

  Next, the main detection process following the preliminary detection process will be described.

  For the sake of concreteness of description, an example will be described in which toner information is detected by blinking three of the nine light emitting units of the reflective optical sensor OS1.

  In the preliminary detection step, the toner pattern YP1 passes through the detection area of the reflective optical sensor OS1. Subsequently, the toner patterns PP1 and DP1 pass through the detection area.

  Normally, it is desirable that the toner patterns YP1, PP1 and DP1 are “in the same position in the main direction”. However, even if the positions in the main direction are not the same position, the toner patterns are formed by optical scanning. The relative positional relationship in the main direction is known.

  Here, a case is considered in which the central portions of the toner patterns PP1 and DP1 in the main direction are “substantially the same position as the central portion of the toner patterns YP1 in the main direction”.

  As described above, it is known that the position of the toner pattern YP1 in the main direction is “position of the light emitting portion E5 (position where the spot of the detection light from the light emitting portion E5 is irradiated)” by the preliminary detection step. Shall.

At this time, the positions of the toner patterns PP1 and DP1 in the main direction are also located in the vicinity of the “position of the light emitting portion E5”.
That is, in the preliminary detection step, “position range information” which is “a guideline of positions where the toner patterns PP1 and DP1 exist in the main direction” is detected.

Assuming that the size of the toner patterns PP1 and DP1 in the main direction is “three times the size of the toner pattern YP1 in the main direction (0.5 mm)”. That is, the size of the toner patterns PP1 and DP1 in the main direction is 1.5 mm. Strictly speaking, {(s-1) × (pitch of light emitting portion) + spot size} or more is sufficient, and if it is 1.3 mm or more, the spot can irradiate the toner pattern.
As described above, the pitch between the light emitting portions Ei is 0.5 mm, and the size of the spot formed on the surface of the transfer belt 17 by the detection light emitted from the light emitting portion is 0.3 mm.
In the preliminary detection step, it is known as position range information that the position in the main direction of the toner pattern YP1 is “position of the light emitting portion E5”, and the center portion in the main direction of the toner patterns PP1 and DP1 is “main in the toner pattern YP1. It is known as the positional relationship in the main direction of the toner patterns YP1, PP1, and DP1 that it is “substantially the same position as the center of the direction”.
Therefore, in this detection process, while the toner patterns PP1 and DP1 pass through the detection regions, the “light spot scanning by the detection light” is performed by the blinking of the three light emitting portions of the light emitting portion E5 and the light emitting portions E4 and E6 on both sides thereof. 3D, the toner patterns PP1 and DP1 are irradiated by the spots S4, S5, and S6 formed on the surface of the transfer belt 17 by the detection light emitted from these three light emitting portions, as shown in FIG. To generate diffusely reflected light.

  Therefore, the toner information can be detected based on the difference between the reflection characteristic (here, regular reflection) of the transfer belt 17 as the support member and the reflection characteristic (here, diffuse reflection) due to the toner pattern.

  As described above, since the “position range in the main direction” of the toner patterns PP1 and DP1 is narrowed down as a result of detection of the toner pattern YP1 in the preliminary detection step, all the light emitting portions E1 to E9 in the reflective optical sensor are sequentially blinked. Instead, according to the narrowed position range, in the case of the above example, the toner information by the toner patterns PP1 and DP1 can be obtained by performing spot scanning by the three issuing units E4 to E6.

  For example, it is necessary to perform spot scanning 60 times while the toner patterns PP1 and DP1 pass through the detection area of the reflective optical sensor OS1 in the sub direction, and 30 spot scannings are performed in the preliminary detection process using the toner pattern YP1. Consider when you need it.

  If spot scanning is performed using all M = 9 light emitting units in the preliminary detection step, the total number of light emission of the light emitting units in the preliminary detection step is 270 times. Further, the total number of times of light emission of the light emitting sections (three) in the main detection process following the preliminary detection process is 180 times for 60 spot scans, and the number of light emission is 450 times through the preliminary detection process and the main detection process. .

  On the other hand, when the toner information is detected from the toner patterns PP1 and DP1 by 60 spot scans without performing the preliminary detection process, the number of times of light emission of the light emitting portion is 9 in each spot scan. The number of light emissions necessary for detection is 540 times.

  That is, the preliminary detection step is performed to obtain the position range information of the toner pattern, and the number of light emitting portions (= s) in the main detection step is set based on the detection result. The number of times can be reduced from 540 to 450 times.

  Of course, while the toner patterns PP1 and PP1 move to the detection area after the toner pattern YP1 is detected in the detection area, the attachment state of the reflection optical sensor OS1 changes or the movement of the reflection optical sensor due to a change in environmental conditions. There is a possibility that the misalignment of the toner pattern PP1 or DP1 in the main direction may occur due to various factors such as skewing or meandering of the support member. Is also "small". If it may be larger than that, it is possible to determine the number s of light emitting units to emit light in consideration of the amount of displacement.

  As can be seen from the above example, even if the toner pattern is misaligned in the main direction, the size of the toner pattern in the main direction is “{(s−1) × (light emitting portion pitch) + the size of the spot. } Is not deviated from the spot scanning of the S spots formed on the surface of the transfer belt.

As described above, the “detection of the toner pattern YP1 for the preliminary detection process by spot scanning with the detection light” has been described with respect to the embodiments shown in FIGS.
Hereinafter, detection of the positional relationship between the sub-directions and the main direction of the respective color toner images using the toner patterns PP1, DP1, etc., that is, detection of toner pattern position information / toner density information will be described.

FIGS. 3E to 3G illustrate “detection of position information by the toner pattern PP1” in an explanatory manner.
As described above, the toner pattern PP1 includes the line patterns LPY1, LPM1, LPC1, LPB1 parallel to the main direction and the line patterns LPY2, LPM2 inclined obliquely with respect to the main direction, as shown in FIG. , LPC2 and LPB2.
The line patterns LPY1 and LPY2 form a pair and are formed of yellow toner.
Similarly, the line patterns LPM1 and LPM2 are paired and formed with magenta toner, the line patterns LPC1 and LPC2 are paired and formed with cyan toner, and the line patterns LPB1 and LPB2 are paired and formed with black toner. Formed with.

A pair of line-shaped patterns of these toners is formed so as to form a constant interval in the sub direction (vertical direction in FIGS. 3E to 3G).
In other words, if these pairs are arranged in the sub-direction at regular intervals, the yellow to black toner images used for image formation are formed so as to have an “appropriate positional relationship in the sub-direction”. Is done.

For detecting whether or not the positional relationship in the sub-direction is appropriate, as shown in FIG. 3E, the timing when the position detection pattern PP1 approaches the reflective optical sensor is measured, for example, at a suitable timing. The part E5 is pulse-lit.
As the position detection pattern PP1 moves, the spot due to the detection light from the light emitting portion E5 is displaced in the sub direction with respect to the support member, and first, the line patterns LPY1 to LPB1 are sequentially irradiated. The pulse light emission of the light emitting part E5 is “short enough for the period” so that these linear patterns can be irradiated without any exception.

When the detection light irradiates each of these linear patterns, the output of the light receiving unit D5 that receives specularly reflected light decreases, and the output of other light receiving units that receive diffusely reflected light increases.
Accordingly, by tracking the outputs of the light receiving portions D1 to D9 in time, it is possible to detect the time interval during which the detection light irradiates the four line patterns. In the example in the description, it is known that the toner patterns LPY1 to LPB1 are reliably irradiated by the spot of the detection light from the light emitting unit E5 by the preliminary detection process, and the light is received when the detection light irradiates the toner pattern. Since it is known that the output of the part D5 decreases, it is basically sufficient to track the output of the light receiving part D5.
If the time interval is equal, the positional relationship between the toner images in the sub-direction is appropriate, and if the time interval is not equal, there is a shift in the positional relationship between the toner images. The timing of starting optical scanning for image formation can be controlled so as to correct.

  The “deviation in the main direction between toner images” can be detected as follows. The detection in this case will be described with reference to FIGS. 3F and 3G for the case of a yellow toner image.

FIG. 3F shows a case where the yellow toner image is at an appropriate position in the main direction (left and right direction in the figure). At this time, the spot of the detection light from the light emitting unit E3 irradiates the line pattern LPY1. Let T be the time until irradiation with the line pattern LPY2.
FIG. 3G shows a case where the yellow toner image is shifted by ΔS in the main direction. Since the line pattern LPY2 is inclined with respect to LPY1, the time from when the spot of the detection light from the light emitting unit E5 irradiates the line pattern LPY1 to the line pattern LPY2 is T + ΔT, which is appropriate. Time at a certain position: Time difference from T: ΔT “Difference in main direction” can be known.

That is, if the angle formed by the line pattern LPY2 in the main direction is “θ” and the moving speed in the sub direction of the transfer belt 17 as a support member is V,
ΔS · tanθ = V · ΔT
Therefore, the deviation amount ΔS in the main direction is
ΔS = V · ΔT · cotθ
Can know as.

  By detecting the “position information” of the toner pattern described above, the toner patterns LPY1 to LPB1 used for detecting the position information in the sub direction are formed “parallel to the main direction”. In this case, even if the light emitting parts other than the light emitting part E5 are caused to emit light, there is a problem if the spot of the detection light of the emitted light emitting part Ei (i ≠ 5) is in a position where the toner patterns LPY1 to LPB1 can be irradiated. There is no.

  Further, when detecting “positional information regarding the main direction”, for example, when the light emitting unit E5 is caused to emit pulses as described above, the time: ΔT is determined according to the light emitting unit E5, and accordingly, The positions of the toner patterns LPY1, LPY2 in the main direction are determined based on the position of the light emitting unit E5 in the main direction.

  However, when the “positional deviation of the toner patterns LPY1 and LPY2 in the main direction” is large with respect to the reflective optical sensor, the spot of the detection light from the light emitting part E5 is the toner pattern even if the light emitting part E5 is caused to emit light. It is also conceivable that LPY1 and LPY2 are not irradiated.

  In this case, if “spot scanning by the light emitting portions E1 to E9” is performed on the toner patterns LPY1 and LPY2, the toner patterns LPY1 and LPY2 can be reliably detected even when the positional deviation in the main direction is large. In this case, the number of times of light emission of the light emitting unit is increased.

  Even in such a case, in the case of the present invention, the toner pattern YP1 for the preliminary detection process is detected by the preliminary detection process, and the toner pattern YP1 and the toner patterns LPY1 and LPY2 are “substantially the main direction. In this detection step, the light emitting portion Ei that can form a spot that can reliably irradiate the toner patterns LPY1 and LPY2 is selected to emit light, whereby the toner pattern PP1 is used. Position detection can be performed reliably.

  The case where one light emitting unit (the light emitting unit E5 in the above example) is used for detecting the position information of the toner pattern PP1 for position detection has been described above, but the density of the toner pattern DP1 described below is described. As in the case of information detection, three (s = 3) light emitting units can also emit light.

  That is, when the position detection toner pattern PP1 approaches the reflective optical sensor OS1, the spot scanning is performed by sequentially lighting three light emitting units, for example, the light emitting units E4, E5, and E6, at an appropriate timing.

  Of course, each line-like pattern of the toner pattern PP1 moving in the sub direction passes through the detection area of the reflective optical sensor OS1 and is detected by spots of detection light from three (s = 3) light emitting units. It is necessary to “scan at least once in the main direction”.

  Since the operation when attention is paid to each light emitting unit is the same as described above, the average value of these three values is obtained by knowing the deviation amounts ΔS of the three main directions corresponding to each light emitting unit, for example. It is also possible to improve the detection accuracy.

  As will be described later, in the above example, “the nine light emitting portions E1 to E9 are intermittently emitted simultaneously in the preliminary detection step”, and in the main detection step, the three light emitting portions (for example, E4 to E6) are simultaneously intermittently provided. It can also emit light.

Next, a case where the toner density is detected by using the toner pattern DP1 for detecting the toner density by the reflection type optical sensor will be described.
As described above, the toner patterns DP1 to DP4 for toner density detection are formed for each color of yellow, magenta, cyan, and black toner.

As an example, the toner pattern DP1 shown in FIG. 3A is formed of yellow toner.
The toner pattern DP1 is obtained by changing the density to a plurality of gradations (5 gradations in the illustrated example) and forming each pattern for each density in a rectangular shape.

  That is, the toner pattern DP1 is a set of five “rectangular toner patterns” having different density gradations. These rectangular toner patterns with different density gradations can be formed by adjusting the laser power or light emission duty in optical scanning or adjusting the developing bias.

As shown in FIGS. 3A and 3B, the toner pattern DP1 is formed on the surface of the transfer belt 17 as a support member and moves in the sub direction, and approaches the detection area of the reflective optical sensor OS1. .
The toner pattern DP1 also has a “time when it is formed”, and the time to reach the detection region after the formation is also substantially determined. Therefore, three (s = 3) light emitting units are sequentially controlled to blink at an appropriate timing when the toner pattern DP1 approaches the detection region.
Needless to say, three (s = 3) light emitting units are moved to the “main direction” within the time when “individual rectangular toner patterns” of the toner pattern DP1 moving in the sub-direction pass through the detection region of the reflective optical sensor OS1. At least once ".

  As described above, when the surface of the transfer belt 17 is smooth and the detection light is irradiated on the portion where the toner pattern is not formed, the reflected light is specular reflection light, and as described above, the light emitting unit Ei (i = When the detection light from 1 to 9) is applied to a portion other than the toner pattern, the light receiving unit Di (i = 1 to 9) receives only the regular reflection light of the detection light from the light emitting unit Ei. ing.

In the example in the description, as described above, through the preliminary detection process of the toner pattern YP1 for detecting position information, the central portion of the “individual rectangular pattern” of the toner pattern DP1 is “detection light from the light emitting portion E5”. It is known that it is in the “irradiated position at the spot”.
Therefore, when the three light emitting units E4, E5, and E6 are sequentially controlled to blink at an appropriate timing when the toner pattern DP1 approaches the detection region, the detection light emitted from the light emitting units E4, E5, and E6 irradiates the toner pattern DP1. In the state where the detection is not performed, the detection light is regularly reflected on the surface of the transfer belt 17 and received by the light receiving portions D4, D5, and D6, respectively. At this time, the amount of light received by the light receiving unit Dj (j = 1, 2, 3, 7, 8, 9) corresponding to the light emitting unit that does not emit light is zero.

As shown in FIG. 3C, when the light emitting portion E5 is turned on and the detection light irradiates the toner pattern DP1 (any one of the rectangular patterns), the detection light is regularly reflected and diffused by the toner pattern DP1. Reflected.
While the regular reflection light component received by the light receiving unit D5 is reduced due to the influence of diffuse reflection, the diffuse reflection light component is also received by the other light receiving units D1 to D9. The same applies when the toner pattern DP1 is irradiated with the detection light from the light emitting units E4 and E6.

  Therefore, when the outputs of the light receiving units D1 to D9 are viewed, in a state where the light emitting unit E5 (or the light emitting unit E4 or E6) emits light, the light receiving unit D5 (or the light emitting unit) corresponding to the light emitting unit E5 (or the light emitting unit E4 or E6). The amount of light received by the portion D4 or D6) is low, and the output at the other light receiving portions (Dj, j ≠ 4, 5, 6) is a value other than zero.

  In the toner pattern DP1, the density is changed to a plurality of gradations, and the light reception amount of the light receiving portion D5 and the light reception amounts of other light receiving portions change corresponding to the gradation (the toner density of the rectangular pattern is changed). The higher the value, the greater the amount of diffuse reflection.) Therefore, the toner density can be obtained from this change.

  That is, the relationship between the toner density of the toner pattern and the data of the amount of light received by each light receiving unit when the detection pattern is irradiated with the spot of the toner pattern is stored in a table or formula, and the output of each light receiving unit and the toner are stored. The toner density of the toner pattern can be determined according to the density correspondence.

As described above, as an example in which the light emitting portions E1 to E9 and the light receiving portions D1 to D9 are arranged at a pitch of 0.5 mm, the toner pattern PP1 (each line pattern) and DP1 (each rectangle pattern) The size in the main direction was 1.5 mm.
By using such a small reflection type optical sensor, even if the “sub-direction size” of the toner patterns PP1 and DP1 is the same as the conventional one, the conventional main direction width is 15 mm to 25 mm. Is 1/10 to 1/16, and the amount of non-contributing toner consumed in the toner pattern can be reduced according to the area.

  Of course, the spot size (0.3 mm in the above embodiment) formed on the surface of the transfer belt 17 by the detection light emitted from the light emitting portions E1 to E9 is also about 1/5 to 1/10 of the conventional sensor. As a matter of course, the size of the toner pattern in the sub direction can also be reduced.

  For example, in the case of the toner pattern PP1 for detecting the toner position, the size in the sub direction is newly reduced from 0.5 mm to 0.5 mm or less from the conventional 1 mm, and in the case of the toner pattern DP1 for detecting the toner concentration, the conventional 15 mm to 25 mm. Therefore, it can be newly reduced to about 2 mm. Therefore, the area ratio as the toner pattern can be reduced to about 1/20 to 1/200.

  In the above embodiment, the main direction size of the toner pattern YP1 for the preliminary detection process is set smaller than the main direction size of the toner patterns PP1 and DP1.

  The toner pattern YP1 for the preliminary detection process is for determining which light emitting part position is closest to the “position in the main direction through which the toner pattern passes”, and therefore the size thereof is “between spots formed by adjacent light emitting parts. It is sufficient that at least one of the light emitting portions is irradiated to a spot formed on the surface of the transfer belt, and the size can be reduced.

On the other hand, since the toner patterns PP1 and DP1 are toner patterns for detecting toner information, it is better to set the “size with a margin” than to make it too small.
The size of the toner pattern YP1 in the main direction (and / or the sub direction) may be equal to the size of the toner patterns PP1 and DP1.

Further, in the above embodiment, the blinking control of the light emitting units E1 to E9 in the preliminary detection step is performed so that “the light emitting units are turned on and off sequentially”. In this case, since the light receiving state of each light receiving unit is always due to lighting of one light emitting unit, the SN ratio of the light receiving signal is improved.
However, the present invention is not limited to this, and intermittent light emission of a plurality of light emitting units (light emitting units E1 to E9 in the above example) can be performed simultaneously.

For the sake of concreteness of description, consider a case where the central portion of the toner pattern YP1 in the main direction is “position irradiated with the spot of the detection light from the light emitting portion E5”.
Each light receiving part Di (i = 1 to 9) is a specularly reflected light of the detection light from the light emitting part Ei when the detection light from the light emitting part Ei (i = 1 to 9) is irradiated to a part other than the toner pattern. Therefore, when the light emitting unit E1 is lit, only the light receiving unit D1 receives light. Similarly, the light receiving units E2, E3, E4, E6, E7, E8, and E9 receive the light receiving unit. Only D2, D3, D4, D6, D7, D8, and D9 receive light.
When the light emitting unit E5 is turned on, the amount of light received by the light receiving unit D5 is smaller than that of the other light receiving units because of the diffuse reflected light from the toner pattern YP1.
When the light emitting parts E1 to E9 are caused to emit light simultaneously, the amount of light received by each light receiving part Di is the sum of “a regular reflection part by the support member and a diffuse reflection part by the toner pattern”.
In other words, the amount of light received by each light receiving portion is “the amount of light received when each light emitting portion emits light individually is superimposed on all light emitting portions” in spot scanning.

  In this case, if the central portion of the toner pattern YP1 in the main direction is at the “position irradiated with the spot of the detection light from the light emitting portion E5”, the regular reflection light received by the light receiving portion D5 is “the largest decrease”. Therefore, among the light receiving parts D1 to D9, the light receiving amount of the light receiving part D5 is the smallest.

  The amount of light received by each light receiving portion is inferior in the SN ratio compared to spot scanning in which the light emitting portions are sequentially blinked, but it is possible to determine the position of the toner pattern YP1 to obtain the position range information of the toner pattern. It is. Further, there is an advantage that the time required for performing the preliminary detection process can be shortened as compared with the case where spot scanning is performed by sequentially blinking the individual light emitting units.

That is, when the light emitting unit Ei (i = 1 to 9) is blinked at the same time, and the output of the light receiving unit Di (i = 1 to 9) is Si (i = 1 to 9), any spot of the detection light is When the toner pattern is not irradiated, the outputs Si are equal to each other.
When the output Sj of the detection light is the smallest, it can be seen that the toner pattern YP1 is at the position of the light receiving part Dj. When the outputs Sk and Sk ± 1 are small, it can be seen that the toner pattern is between the light receiving portions Dk and Dk ± 1 in the main direction (the relationship between Sk and Sk ± 1 indicates the light receiving portions Dk and You can see which of Dk ± 1.)

On the upper side, in addition to the toner pattern PP1 for position information and the toner pattern DP1 for density information, a “toner pattern YP1 dedicated to the preliminary detection process” is formed, and the preliminary detection process is executed on the toner pattern YP1. An example was explained.
As another example, in the embodiment of FIG. 3, the preliminary detection step may be performed for the toner pattern (line pattern LPY1) at the head in the sub-direction of the toner pattern PP1 except for the toner pattern YP1.

  That is, at the timing when the line pattern LPY1 approaches the detection area, the r light emitting units (for example, the light emitting units E1 to E9) are sequentially blinked to perform spot scanning, or the light emitting units are blinked simultaneously to form a line shape. Preliminary detection process for the pattern LPY is performed to obtain position range information. Based on the position range information thus obtained, s (<r) light emitting units are targeted for each toner pattern after the line pattern LPM1. This detection step can be performed using.

In this way, since the dedicated toner pattern YP1 is not required for the preliminary detection process, the time required for acquiring the toner information as a whole can be shortened.
When the toner pattern DP1 is located downstream of the toner pattern PP1 in the sub direction, the preliminary detection process is performed on the rectangular pattern at the head of the sub direction in the toner pattern DP1. You can do it.

  In the embodiment described above, as a premise of detection, when the detection light from the light emitting unit Ei (i = 1 to 9) of the reflective optical sensor is irradiated to a part other than the toner pattern, the light receiving unit Di (i = 1 to 9) explained the case where “only the regular reflection light of the detection light from the light emitting portion Ei” is received.

  That is, when the detection light emitted from one light emitting portion Ei is irradiated on the “supporting member surface on which no toner pattern exists” in the correspondence relationship between the same number of light emitting portions and light receiving portions of the reflective optical sensor, this light emission Only the light receiving part Di corresponding to the part detects “regularly reflected detection light”.

For example, the detection light emitted from the light emitting unit E5 is received only by the light receiving unit D5 when the toner pattern does not exist in the irradiation unit, and is not received by the other light receiving units.
When the detection light emitted from the light emitting unit E5 irradiates the toner pattern, the detection light is diffusely reflected by the toner pattern and received by the other light receiving units D1, D2, D3, D4, D6, D7, D8, and D9. .

This state is shown in FIG. 4 as an explanatory diagram.
FIG. 4A shows that the detection light emitted from the light emitting unit E5 is irradiated on the surface of the supporting member where the toner pattern does not exist and is regularly reflected and received only by the light receiving unit D5, and the other light receiving units D1, D2, D3, D4, D6, D7, D8, and D9 indicate “output distribution of the light receiving portion Di (i = 1 to 9)” when no light is received.

  In FIG. 4B, the detection light emitted from the light emitting part E5 is diffusely reflected by irradiating the toner pattern, and not only the light receiving part D5 but also other light receiving parts D1, D2, D3, D4, D6, D7, “Output distribution of light receiving portion Di (i = 1 to 9)” when D8 and D9 are also receiving light is shown.

  “Specular reflection light” reflected by the toner pattern decreases monotonously as the toner density increases, and “diffuse reflection light” increases monotonously as the toner density increases. The output of the light receiving unit D5 and the outputs of the other light receiving units D1, D2, D3, D4, D6, D7, D8, and D9 can be used as “information for determining the toner density of the toner pattern”. The toner density can be detected by a preset algorithm of “arithmetic processing for deriving a toner density value”.

  For example, in the above case, it is known that the toner pattern is located at the position of “light emitting portion D5” in the main direction due to a decrease in output at the light receiving portion D5. At this time, another light receiving portion Di (i ≠ 5) When this sum is taken, this changes in proportion to the toner density of the toner pattern. Therefore, the toner density can be detected from the sum of the outputs. At this time, a decrease in output from the light receiving unit D5 can also be used as data for determining the toner density, and using this makes it possible to detect the toner density with higher accuracy.

  In such a case, the “reflected light by the support member” and the “reflected light by the toner pattern” are “caused by regular reflection” received by the light receiving unit Di corresponding to the light emitting unit Ei (i = 5 in the above example). The “regular reflection contribution output” that is “the output to be performed” and the “diffuse reflection contribution output” that is the “output due to diffuse reflection” received by the light receiving unit Dj (j ≠ i) that does not correspond to the light emitting unit Ei. Since the classification is possible, the algorithm of “arithmetic processing for deriving the toner density value” is also simplified.

  However, depending on the form of the reflective optical sensor, the output of each light receiving unit cannot be simply classified into “regular reflection contribution output” and “diffuse reflection contribution output”. There is a possibility that the output will be mixed.

  For example, even in the case of “having nine light emitting portions E1 to E9 and light receiving portions D1 to D9 corresponding to these” as in the reflective optical sensor described with reference to FIG. When the “arrangement pitch” is reduced and the “arrangement pitch of the light receiving parts D1 to D9” is correspondingly reduced, or “the detection light emitted from the light emitting part Ei is divergent and is regularly reflected on the surface of the support member. Then, the light beam diverges toward the light receiving part and spreads to a light beam width equal to or larger than the arrangement pitch of the light receiving parts at the arrangement position of the light receiving part. Furthermore, these two cases are mixed.

Such a case will be described with reference to FIGS. 3A to 3C as an example.
As described above, in FIG. 3, it is assumed that the surface of the transfer belt 17 is smooth, and the reflected light when the detection light is irradiated to the portion where the toner pattern is not formed is specular reflection light.
Further, when the detection light from the light emitting unit Ei (i = 1 to 9) that sequentially emits light is applied to a portion other than the toner pattern, the specularly reflected light is transmitted to the light receiving unit Di corresponding to the light emitting unit Ei. It is assumed that light is received by the adjacent light receiving part Dj (j = i ± 1).

FIG. 5A shows a state of “output of each light receiving portion Di (i = 1 to 9)” when the light emitting portion E5 is turned on and the “lighting portion other than the toner pattern” is irradiated with the detection light. Yes.
The light receiving parts D4, D5, D6 receive “regularly reflected light from the transfer belt 17”, but the outputs of the light receiving parts D1, D2, D3, D7, D8, D9 are zero.

As described above, when the detection light from the light emitting portion Ei (i = 1 to 9) is irradiated on a portion other than the toner pattern, the specularly reflected light is adjacent to the light receiving portion Di corresponding to the light emitting portion Ei. As an example, the central portion in the main direction of the toner pattern DP1 is set to the “position irradiated with the spot of the detection light from the light emitting portion E5” under the condition that “the light is received by the light receiving portion Dj (j = i ± 1)”. Consider a case.
In this case, the detection light emitted from the light emitting part E1 is regularly reflected on the surface of the transfer belt 17, and received by the light receiving parts D1 and D2, and the detection light emitted from the light emitting part E2 is received by the light receiving parts D1, D2 and D3. Received light. Detection light emitted from the light emitting unit E3 is received by the light receiving units D2, D3, and D4, and detection light emitted from the light emitting unit E4 is received by the light receiving units D3, D4, and D5.

  Similarly, the detection light emitted from the light emitting unit E8 is regularly reflected by the surface of the transfer belt 17, and received by D7, D8, and D9. The detection light emitted from the light emitting unit E9 is received by the light receiving units D8 and D9. Received light. The detection light emitted from the light emitting unit E6 is received by the light receiving units D5, D6, and D7, and the detection light emitted from the light emitting unit E7 is received by the light receiving units D6, D7, and D8.

When the light emitting unit E5 is turned on and the detection light irradiates the toner pattern DP1, the detection light is “reflected and diffusely reflected” by the toner pattern DP1.
The “specularly reflected light component received by the light receiving portions D4, D5, and D6” is reduced due to the influence of the diffuse reflection by the toner pattern DP1, while the diffuse reflected light is received by the light receiving portions D1, D2, D3, other than the light receiving portion D5. Light is also received by D4, D6, D7, D8, and D9.

  The state of “output of each light receiving part D1 to D9” in this state is as shown in FIG.

  As understood from the comparison between FIG. 5A and FIG. 5B, the output of the light receiving unit D5 corresponding to the light emitting unit E5 is only the output due to “regular reflection by the support member or the toner pattern” (FIG. 5A ("Output by specular reflection light") is reduced by diffuse reflection in (b)). Out of the eight light receiving portions Dj (j ≠ 5) that do not correspond to the light emitting portion E5, the outputs of the six light receiving portions D1, D2, D3, D7, D8, and D9 are outputs resulting from “diffuse reflection by the toner pattern”. Only.

  On the other hand, among the eight light receiving parts Dj (j ≠ 5) not corresponding to the light emitting part E5, the outputs of the two light receiving parts D4 and D6 on both sides of the light emitting part E5 are specular reflection components (FIG. 5 ( a)) and the diffuse reflection component (FIG. 5B) by the toner pattern are mixed (the outputs of the light receiving portions D4 and D6 are in the state of FIG. 5A by receiving the diffuse reflection component). It ’s getting bigger.)

  As is clear from the comparison between FIGS. 5A and 5B, the output distribution of the light receiving portions D1 to D9 indicates that the detection light from the light emitting portion E5 is “irradiating the support member or irradiating the toner pattern”. Therefore, it is possible to calculate the “toner density in the toner pattern” using the difference in output as toner information.

  However, from the viewpoint of simplifying the algorithm of operation, as described above, “the light receiving portion in which the regular reflection component by the support member and the diffuse reflection component by the toner pattern are mixed (in the above example, the light receiving portions D4 and D6). Is preferably removed from the information used for the calculation.

  That is, the output of the N light receiving units of the light receiving means is “the output of the light receiving unit Di corresponding to each light emitting unit Ei is a regular reflection contribution output” and “the light receiving unit not corresponding to each light emitting unit Ei (Dj j ≠ i and j The output of ≠ i ± 1) is classified as “diffuse reflection contribution output”, and the toner density can be detected arithmetically based on these outputs.

  This will be described in the case of the light emitting unit Ei (i = 1 to 9) and the light receiving unit Di (i = 1 to 9) described above, and the light receiving unit Dj (j when the light emitting unit Ei emits light will be described. = 1-9), the light receiving part Di that receives only the specular reflection component of the detection light from the light emitting part Ei is referred to as “light receiving part corresponding to the light emitting part Ei”, and the output is “regular reflection contribution output”. And

  Further, when the light emitting unit Ei is caused to emit light, the light receiving unit Dj (j ≠ i and j ≠ i ± 1) that receives only the diffuse reflection component is defined as “light receiving unit not corresponding to the light emitting unit Ei”, and the output thereof is “ "Diffuse reflection contribution component".

  In the above example, if the light emitting unit E5 is caused to emit light, the output of D5 corresponding to the light emitting unit E5 is the “regular reflection contribution output”, and the light receiving units D1, D2, D3, not corresponding to the light emitting unit E5, The outputs of D7, D8, and D9 are “diffuse reflection contribution outputs”.

  The light receiving units D4 and D6 receive “regular reflection light and diffuse reflection light”, and the target of light reception is “not only regular reflection light but also diffuse reflection light”. Not classified as either “regular reflection contribution output” or “diffuse reflection contribution output”.

  In this way, the outputs of the light receiving parts D1 to D9 are classified into “regular reflection contribution output and diffuse reflection contribution output”, and toner density calculation is performed by using the regular reflection contribution output and the diffuse reflection contribution output. Since the influence of regular reflection by the surface of the support member and the influence of diffuse reflection by the toner pattern are separated, the calculation algorithm can be simplified.

  That is, if the explanation is supplemented when the light emitting unit E5 is turned on, the output of the light receiving unit D5 corresponding to the light emitting unit E5 is the “regular reflection contribution output”, but the six light receiving units not corresponding to the light emitting unit E5. The “output due to regular reflection at the support member” of the parts D1, D2, D3, D7, D8, D9 is zero, which is “regular reflection contribution output is zero”, that is, “diffuse reflection contribution output”, The output of the light receiving unit D5 can be regarded as “diffuse reflection contribution output is 0”.

  Here, since there are generally two or more light receiving parts Ej that do not correspond to the light emitting part Ei, by taking the “sum of outputs” of these light receiving parts Ej, diffuse diffused contribution output over a plurality of light receiving parts is obtained. Therefore, “diffuse reflected light detection accuracy” can be improved.

  For example, when the toner pattern DPI is irradiated with the detection light from the light emitting unit E5, the regular reflection contribution output of the light receiving unit D5 corresponding to the light emitting unit E5 and the light receiving units D1, D2, D3, not corresponding to the light emitting unit E5, Among the outputs of D7, D8, and D9, the outputs from the light receiving portions D1, D2, D3, D7, D8, and D9 are diffuse reflection contribution outputs related only to the diffuse reflection due to the toner pattern. The system for density detection can be enhanced by increasing the amount of information for toner density information.

When the outputs of the seven light receiving portions D1, D2, D3, D5, D7, D8, and D9 are used, the reflection characteristics of the support member (the output of the light receiving portion D5 that is a regular reflection contribution output) and the reflection characteristics of the toner pattern (positive) Difference between the output of the light receiving unit D5 that is the reflection contribution output and the output of the light receiving units D1, D2, D3, D7, D8, and D9 that is the diffuse reflection contribution output (difference between the regular reflection contribution output and the diffuse reflection output) Based on the above, the toner density can be detected.
A brief description will be given in relation to the calculation.
Focusing on “regular reflection contribution output only” as the reflection characteristic, and calculating the correlation between “the difference between the output of the light receiving part D5 by the support member and the output of the light receiving part D5 by the toner pattern” and “the image density of the toner pattern” As another example, focusing on “diffuse reflection contribution output only” as the reflection characteristic, “light output by the support members D1, D2, D3, D7, D8, and D9 (= 0) and light reception by the toner pattern The toner density can be detected by calculating the correlation between “the difference between the output sums of the portions D1, D2, D3, D7, D8, and D9” and “the image density of the toner pattern”.

  Further, if attention is paid to “both regular reflection contribution output and diffuse reflection contribution output” as the reflection characteristics, it is possible to calculate and calculate the toner density with higher accuracy. Here, the above-mentioned “difference” does not intend only so-called subtraction, but means “difference”.

  Since the outputs of the two light receiving parts D4 and D6 not corresponding to the light emitting part E5 are “mixed with the output due to the regular reflection and the output due to the diffuse reflection,” the outputs from these light receiving parts D4 and D6 are By excluding from the calculation information, the calculation algorithm can be simplified, and more efficient processing is possible.

  As described above, the outputs of the two light receiving parts D4 and D6 that do not correspond to the light emitting part E5 are “the output due to the regular reflection contribution and the output due to the diffuse reflection contribution are mixed”, but by the method described below, The outputs of the light receiving portions D4 and D6 can be separated into “an output component due to regular reflection and an output component due to diffuse reflection”.

  According to this method, the calculation algorithm is slightly complicated, but the signals of all the light receiving units can be used effectively.

As described above, when the toner pattern DPI (any of the rectangular patterns) is irradiated with the detection light from the light emitting unit E5, the regular reflection contribution output from the toner pattern is the output of the light receiving unit D5.
On the other hand, when the detection light irradiates the surface of the support member, the regular reflection light from the surface of the support member is received by the light receiving portions D4, D5, and D6 with an output distribution as shown in FIG.

That is, the reflection characteristic of the toner pattern (output distribution shown in FIG. 5B) and the reflection characteristic of the support member (that is, the “regular reflection characteristic” output distribution shown in FIG. 5A) are respectively output by the light receiving unit D5. The standardized version is shown in FIG.
In FIG. 6, the “white bar” can be considered as the reflection characteristic of the toner pattern (FIG. 5B), and the “black bar” can be considered as the “regular reflection contribution” of the reflection characteristic of the toner pattern. By normalization, the value of the regular reflection characteristic and the value of the diffuse reflection characteristic of the output of the light receiving unit D5 are equal.

In the output distribution of FIG. 6, the diffuse reflection contribution can be obtained by subtracting the size of the black bar from the size of the white bar, that is, by subtracting the regular reflection contribution from the reflection characteristics of the toner pattern. it can.
That is, FIG. 7 shows the “reflecting characteristics of the toner pattern” in FIG. 5B divided into the regular reflection contribution and the diffuse reflection contribution. The diffuse reflection contribution indicated by “white bar” in FIG. 7 is obtained by subtracting “black bar” from each “white bar” in FIG. 6, and “black bar” in FIG. Is the same.

That is, as shown in FIG. 7, the outputs of the two light receiving parts D4 and D6 that do not correspond to the light emitting part E5 are “output due to regular reflection (black bar) and output due to diffuse reflection (white bar)”. Have been separated.
Using the outputs of the nine light receiving parts Di (i = 1 to 9), the reflection characteristics of the support member (outputs of the light receiving parts D4, D5 and D6 (black bars) which are regular reflection contribution outputs) and the reflection characteristics of the toner pattern Difference between (outputs of light receiving parts D4, D5, and D6, which are regular reflection contribution outputs, and outputs (white bars) of light receiving parts D1, D2, D3, D4, D6, D7, D8, and D9, which are diffuse reflection contribution outputs) The toner density can be detected based on (difference between regular reflection contribution output and diffuse reflection output).
In the example described so far, the specularly reflected light on the transfer belt surface of the detection light emitted from each light emitting portion Ei is the corresponding light receiving portion Di and the light receiving portion Dj (j = i ± 1) adjacent thereto. ) And received light.
As described above, when the support member is an intermediate transfer belt or the like, there is a case where “the detection light is diffusely reflected on the surface of the support”.
However, if there is a difference in the reflection characteristics between the diffuse reflection by the support and the "diffuse reflection by the toner pattern", the "distribution of the output of the plurality of light receiving parts" depends on the diffuse reflection by the support and the diffuse reflection by the toner pattern. Therefore, “toner density detection” is possible from the difference in the output distribution.

An example of “when the support member surface diffuses and reflects detection light” will be described.
In the example shown in FIG. 8, the number of light emitting parts Ei of the reflection type optical sensor: M = number of light receiving parts Di = N = 7 is shown.

Except that the number of light emitting parts and light receiving parts is 7, and that the supporting member is an “intermediate transfer belt that diffuses and reflects detection light with a non-smooth surface”, it is the same as in the case of FIG.
For the sake of simplicity, it is assumed that the toner pattern has a higher degree of diffusion due to diffuse reflection than the intermediate transfer belt. In the opposite case, that is, in the case where “the intermediate transfer belt has a higher degree of diffusion due to diffuse reflection than the toner pattern”, it may be considered that “intermediate transfer belt and toner pattern are interchanged” in the following description.

FIG. 8A shows an output state of the light receiving portion Di (i = 1 to 7) when the portion other than the toner pattern (intermediate transfer belt) is irradiated with the light emitting portion E4 turned on.
The light receiving parts D2 to D6 receive “regular reflection light and diffuse reflection light by the intermediate transfer belt”, but the outputs of the light receiving parts D1 and D7 are zero.

  FIG. 8B shows an output state of the light receiving unit Di (i = 1 to 7) when the light emitting unit E4 is turned on and “when the detection light irradiates the toner pattern”.

At this time, “regular reflection light and diffuse reflection light by the toner pattern” are received by the light receiving portions D1 to D7.
In this example, “the toner pattern has a greater degree of diffusion of diffuse reflected light than the intermediate transfer belt”, and therefore FIG. The spread of the distribution has increased.

  In FIG. 8A, it is desired to specify “light receiving part including contribution due to diffuse reflected light” among the light receiving parts D2 to D6 whose output of the light receiving part is not zero. Of course, the output of the light receiving part D4 corresponding to the light emitting part E4 is a regular reflection contribution output.

  Assuming that the surface of the intermediate transfer belt is smooth, “how far the range of the light receiving unit that receives specularly reflected light reaches” depends on the optical simulation modeling the reflective optical sensor and the actual reflective optical sensor. It is easy to identify separately by an experiment using a transfer belt having a smooth surface.

  Therefore, by identifying the light receiving unit including the contribution due to the regular reflection light in advance, the “light receiving unit including only the contribution due to the diffuse reflection light” among the outputs of the light receiving units D2 to D6 in FIG. Can be identified.

FIG. 8C shows the “contribution due to regular reflection light” obtained by “an experiment using a transfer belt having a smooth surface” with hatching.
By comparing (a) and (c) in FIG. 8, the output of the light receiving unit D4 in FIG. 8 (a) represents “regular reflection contribution output due to regular reflection by the intermediate transfer belt”, and the light receiving unit D2 and The output of D6 is “diffuse reflection contribution output due to diffuse reflection by the intermediate transfer belt”.
Further, in FIG. 8A, the outputs of the light receiving portions D1 and D7 are zero, but this can also be regarded as “output due to diffuse reflection” being zero. The outputs of the light receiving parts D3 and D5 are a mixture of “outputs resulting from regular reflection and diffuse reflection”.

  Therefore, also in FIG. 8B, the output of the light receiving unit D4 is “only the output due to regular reflection by the toner pattern”, and the output of the light receiving units D1, D2, D6, and D7 is “diffuse reflection by the toner pattern”. Only the resulting output ”, and the outputs from the light receiving portions D3 and D5 are mixed with the outputs resulting from regular reflection and diffuse reflection.

That is, the output of the light receiving unit D4 corresponding to the light emitting unit E4 can be classified as a regular reflection contribution output, and the outputs of the four light receiving units D1, D2, D6, and D7 not corresponding to the light emitting unit E4 can be classified as diffuse reflection contribution outputs.
Further, the outputs of the two light receiving parts D3 and D5 that do not correspond to the light emitting part E4 are not taken into the calculation of the toner density because “regular reflection component and diffuse reflection component” are mixed.

  Above, in the case of a combination of a reflection type sensor of M = N = 9 and a transfer belt (FIG. 5) that can be regarded as “a smooth surface and reflection of detection light is substantially regular reflection” as a supporting member; The case of the combination of the reflection type sensor of M = N = 7 and the intermediate transfer belt (FIG. 8) as the supporting member “the surface is not smooth and diffusely reflects the detection light” has been described. It goes without saying that "it does not depend on the number of M or N, and can support any kind of support member".

As shown in FIG. 5 and FIG. 8, when the light receiving unit that receives the specularly reflected light is “only the light receiving unit corresponding to the light emitting unit and its adjacent light receiving units”, Is mixed with the contribution of diffuse reflection.
In this case, the number of light receiving parts to which diffuse reflection contributes is (N−3) ((N−2) light emitting parts at both ends). That is, in particular, even when “the pitch of the light emitting unit and the light receiving unit is small” and the spot diameter of the detection light reflected by the support member is larger than the pitch of the light receiving unit, “the regular reflection light from the support member is incident. It is “only the light receiving part corresponding to the light emitting part and its neighbors”, so that the number of light receiving parts serving as diffuse reflection contribution outputs can be maximized, and “diffuse reflection contribution detection efficiency” can be improved.

  The example described with reference to FIGS. 4 to 8 above is a case where “toner density information” is detected as the main detection step using the reflective optical sensor OS1 with respect to the toner pattern DP1. As a premise, the position of the toner pattern in the main direction in the preliminary detection step is a position irradiated with the spot of the detection light from the light emitting unit E5, and the specularly reflected light is received by the light receiving unit D5.

  As in this example, when it is known from the position range information obtained by the preliminary detection step that the position in the main direction of the toner pattern DP1 is a position corresponding to the light receiving part D5, As described above, it is possible to detect the toner density information as the main detection by using the light emitting unit that emits light in the main detection process as one light emitting unit E5.

  In other words, if the preliminary detection process knows that the position of the toner pattern DP1 in the main direction is a position corresponding to the light receiving part Di (i = 1 to 9, or i = 1 to 7), As described above, it is possible to detect the toner density information as the main detection by using the light emitting unit that emits light in the main detection step as one light emitting unit Ei.

  When the pre-detected position range information is a little wider, not only the light emitting part of one light emitting part is used, but, for example, three light emitting parts Ei, Ei ± 1 (in the case of the above example, The main detection process may be performed by causing the light emitting units E4, E5, and E6) to emit light, and the concept of toner density detection is the same as that described above. As the amount of signal used for density detection increases, accurate detection is possible.

Hereinafter, another embodiment will be described.
As described above, in the toner pattern detection described with reference to FIGS. 3A to 3C, the light emitting units E1 to E9 blink sequentially in the reflective optical sensor OS1. In this case, it takes a finite time from when the light emitting unit E1 is turned on / off to when the light emitting unit E9 is turned on and off.
This time is called “scan time”.

  In the above, the case where spot scanning is performed on the toner pattern YP1 by sequentially blinking the light emitting units E1 to E9 when performing the preliminary detection step has been described. In this case, the toner pattern YP1 is reflected optically during the scanning time. It must be present in a spot scanning region by the sensor (a region where spot scanning is performed by sequential blinking with a spot of detection light, which is the detection region described above). In other words, the light emitting units E1 to E9 must complete the sequential lighting and extinguishing while the toner pattern YP1 is present in the spot scanning region.

The scan time is short if the number of light emitting parts included in the reflective optical sensor: M is small, and is almost instantaneous.
However, as described above, in order to reduce the toner pattern formation time so as not to reduce the work efficiency of the image forming operation, and to reduce the consumption of non-contributing toner effectively, the toner pattern is reduced in size. There is a need to.
In order to detect the toner density by appropriately irradiating the small-size toner pattern with the detection light, the arrangement pitch of the light emitting unit and the light receiving unit must be reduced as the toner pattern becomes smaller in the main direction.
If an allowable amount for the “relative positional deviation in the main direction” between the toner pattern and the reflective optical sensor is about 10 mm or more, if the arrangement pitch is reduced, the number of light emitting units to be arranged: M is also a considerable number (for example, 200). Increase).
As the number M of light emitting parts increases, the scan time also increases.
In the present invention, when the toner information for the position detection toner pattern PP1 and the toner density detection toner pattern DP1 is detected in this detection process, the positions of these toner patterns on the support member are detected by the preliminary detection process. Based on the obtained position range information, it has been narrowed down to some extent in advance, and only a small number of S light emitting portions are caused to emit light accordingly, so that the scanning time can be effectively shortened in the main detection step of detecting toner information. .

  However, in the preliminary detection step for obtaining the position range information, it cannot be denied that the scan time becomes longer as the number of light emitting units: M increases.

  If the scan time is “st” and the speed of the support member that is formed in the toner pattern and moves in the sub direction is “V”, the support member is displaced in the sub direction by “V · st” within the scan time. become.

  Then, when the number of light emitting parts: M increases and the scanning time becomes longer, depending on the moving speed of the support member: V, the toner pattern (toner pattern YP1 in the above example) passes through the spot scanning region in the preliminary detection step. The time may be shorter than the scan time, and in such a case, an appropriate preliminary detection process becomes difficult.

FIGS. 9A and 9B are diagrams showing an embodiment in which such a problem can be solved.
In the embodiment shown in FIGS. 9A and 9B, the reflective optical sensor has 15 light emitting portions E1 to E15 and 15 light receiving portions D1 to D15 corresponding to the light emitting portions 1: 1. ing.
The reason why the number of light emitting units and light receiving units is set to 15 is to avoid the complexity of the drawing, and the number of 15 is merely for convenience of explanation. Actually, several tens to several hundreds are assumed as the number of light emitting units and light receiving units.

  The preliminary detection step will be described as being performed on the toner pattern YP1 shown in FIG.

In the embodiment shown in FIG. 9A, the arrangement of the light emitting parts E1 to E15 and the light receiving parts D1 to D15 is divided into three in one direction (vertical direction in the figure), and each divided part, that is, the light emitting part E1. To E5, the light receiving parts D1 to D5, the light emitting parts E6 to E10, the light receiving parts D6 to D10, and the light emitting parts E11 to E15 and the light receiving parts D11 to D15 are in the sub-direction of the support member (the horizontal direction in the figure). ) Is shifted in the sub-direction with a predetermined shift width (referred to as ΔL) corresponding to the moving speed to.
The light emitting units E1 to E15 are sequentially turned on and off from E1 to E15. At this time, the toner pattern YP1 (not shown) moves at a speed V in the sub direction.
In this case, if the scanning time is “st”, the time required for the light emitting units E1 to E5 to complete sequential lighting / light emission is “st / 3”, and the light emitting units E6 to E10 are sequentially turned on / The time required to complete the light emission and the time required for the light emitting units E11 to E15 to complete the sequential lighting and light emission are also “st / 3”.

During this time: st / 3, the toner pattern YP1 (not shown) is displaced in the sub direction by “V · st / 3”, so that the deviation amount: ΔL is ΔL = V · st / 3.
Is set so as to satisfy the above, spot scanning of the toner pattern YP1 by the light emitting portions E1 to E15 can be properly terminated within the scan time.

  In the embodiment shown in FIG. 9B, the 15 light emitting units / light receiving units are arranged in a direction in which the direction in which the light emitting unit and the light receiving unit are arranged is the sub-direction of the support member (up and down direction in FIG. 9B). It is inclined by a predetermined angle (referred to as α) corresponding to the moving speed (referred to as V in the left direction in the figure).

In this case, if the scanning time is “st” and the arrangement length of the light emitting parts E1 to E15 and the light receiving parts D1 to D15 in the main direction is “Z”,
Z ・ tanα ＝ V ・ st
If the angle α is set so as to satisfy the above, spot scanning of the toner pattern YP1 (not shown) by the light emitting portions E1 to E15 can be properly terminated within the scanning time.

  In the embodiment shown in FIG. 10, optimization of spot scanning in the preliminary detection process is performed as follows.

  Also in this figure, the reflective optical sensor has fifteen light-emitting parts 5 and fifteen light-receiving parts corresponding to the light-emitting parts 1: 1. The reason why the number of light emitting units and light receiving units is set to 15 is to avoid the complexity of the drawing, and the number of 15 is merely for convenience of explanation. Actually, several tens to several hundreds are assumed as the number of light emitting units and light receiving units.

  In the 15 light emitting units / light receiving units in the embodiment of FIG. 10, one direction in which the light emitting units are arranged and one direction in which the light receiving units are arranged are substantially parallel to the main direction (vertical direction in the drawing).

Of the 15 light emitting units and 15 light receiving units, 5 light emitting units and 5 light receiving units constitute a light emitting unit / light receiving unit pair, and 3 light receiving unit / light emitting unit pairs are aligned in the main direction. Are arranged.
The light receiving part / light emitting part pair G1 is composed of five light emitting parts E11 to E15 and five light receiving parts D11 to D15 corresponding to the light emitting parts 1: 1 to E15. The five light emitting units E21 to E25 and the five light receiving units D21 to D25 corresponding 1: 1 with the light emitting units E21 to E25. The light receiving unit / light emitting unit pair G3 includes five light emitting units E31 to E35. Each of the light emitting units and the five light receiving units D31 to D35 corresponding to the light emitting units 1: 1 are provided.

The light receiving portion / light emitting portion pairs G1 to G3 are structurally identical.
Then, in the state in which the 15 light emitting units perform toner density detection, the three light emitting units corresponding to each other in the three light emitting unit / light receiving unit pairs G1 to G3 blink simultaneously and sequentially.

  That is, when spot scanning is performed in the preliminary detection step, first, the first light emitting units E11, E21, E31 in the light receiving unit / light emitting unit pair G1 to G3 are turned on / off simultaneously, and then the light emitting units E12, E22. , E32 are turned on / off simultaneously, and the light emitting units E13, E23, E33 are simultaneously turned on / off, the light emitting units E14, E24, E34 are simultaneously turned on / off, and the light emitting units E15, E25, E35 are simultaneously turned on.・ Lights off.

  In this way, the scanning time can be shortened to st / 3 compared to the case of FIG. 4, and the spot scanning is completed while the toner pattern YP1 (not shown) passes through the spot scanning region. it can.

  The positions of the light emitting parts E11, E21, E31 and the positions of the light receiving parts D11, D21, D31 in the light emitting part / light receiving part pairs G1 to G3 shown in FIG. As shown in the embodiment of FIG. 9B, the light receiving portions may be arranged with an inclination at “an angle corresponding to the moving speed of the support member in the sub direction (left side of the drawing)”.

  As in the embodiment shown in FIG. 9 and FIG. 10, when the arrangement pitch is equal by increasing the number of light emitting units and light receiving units, the length of the reflective optical sensor in the main direction increases and the sensing region becomes larger. Since the length becomes longer, an allowable amount for “the positional deviation of the toner pattern YP1 with respect to the main direction” becomes larger. Further, when the lengths of the reflective optical sensors are equal, the arrangement pitch of the light emitting units and the light receiving units is shortened, and the “spatial resolution in the main direction” is increased.

  In the example shown in FIGS. 9 and 10, if the position range information is known in the preliminary detection process for the toner pattern YP1 by spot scanning as described above by 15 light emitting units, position information detection is performed based on the position range information. It is only necessary to perform the main detection by spot scanning with s light emitting sections that can surely detect the spot of the toner pattern PP1 for toner and the toner pattern DP1 for toner density detection.

  As described above, the number of light emitting parts: M and the number of light receiving parts: N constituting the reflective optical sensor used in the practice of the present invention need not be the same.

That is, M ≠ N.
FIG. 11 shows three embodiments in such a case.

The form example shown in FIG. 11A is an example in which N = 15 and M = 30.
In the light emitting means, the light emitting portions E11 to E1i to E115 are arranged in the main direction (vertical direction in the drawing) at one row and the same pitch, and the light emitting portions E21 to E2i to E215 are arranged in the main direction at the same pitch and these two rows. As for the arrangement of the light emitting parts, corresponding ones are in the same position in the main direction.

Fifteen light receiving portions D1 to Di15 are arranged at equal pitches in the main direction so as to be sandwiched between the two light emitting portion rows, and each light receiving portion is connected to the corresponding light emitting portion in the “main scanning direction”. It is located at the same position ”.
For i = 1 to 15, the light emitting portions E1i and D2i at the same position in the main scanning direction are turned on / off simultaneously and sequentially in each column, thereby outputting the detection light for irradiating the support member and the toner pattern. Can be doubled.
The light emission output of the LED generally used as the light emitting part does not depend on the area of the light emitting part but depends on the injection current density.
If the injection current density is increased in order to increase the light emission output, the life of the LED is shortened, and therefore the injection current density cannot be increased beyond a certain level. In this case, the injection current amount can be increased by increasing the area of the light emitting portion (without increasing the injection current density). Invite.

  In such a case, as shown in FIG. 11A, it is preferable that the light output area is not increased, the light emission parts are arranged in two rows, and the light output is doubled without changing the current density.

In the example shown in FIG. 11B, conversely, M = 15 and N = 30.
Fifteen light emitting units E1 to Ei to E15 are arranged in the main direction at an equal pitch in one row, 30 light receiving units are divided into two groups of 15 each, and the light receiving units D11 to D1i to D115 are arranged in one row in the main direction. The light receiving portions D21 to D2i to D215 are arranged at an equal pitch in the main direction, and the light emitting portion rows are sandwiched between the two light receiving portion rows in the sub direction.
As i = 1 to 15, the corresponding light emitting unit Ei and the light receiving units D1i and D2i are located at the same position in the main scanning direction.

  Thus, by receiving the detection light (reflected light) in two rows of PDs constituting the light receiving means, the light receiving sensitivity can be increased by a factor of two. It is also possible to improve the light receiving sensitivity by doubling the light receiving area in the sub-scanning direction with the PDs arranged in one row, but depending on the spot size of the reflected light reflected from the support member and the toner pattern (the spot size is The improvement rate of light receiving sensitivity is small (especially when small). In contrast, as shown in FIG. 11B, it is expected that the light receiving sensitivity can be improved by arranging two rows at positions symmetrical to the sub-direction with the LED array in between.

In the embodiment described above with reference to FIGS. 2 to 11B, the arrangement pitch of the light emitting units and the light receiving units is equal, and the arrangement pitch of the light emitting units and the arrangement pitch of the light receiving units are equal to each other.
However, the arrangement pitch of the light emitting units and the arrangement pitch of the light receiving units can be different from each other.

FIG. 11C shows an example of such a case.
In this embodiment, 14 light receiving parts D1 to Dj to D14 are associated with seven light emitting parts E1 to Ei to E7, and the arrangement pitch of the light receiving parts is set to ½ of the arrangement pitch of the light emitting parts. Thus, two light receiving sections correspond to each light emitting section Ei (i = 1 to 7). As described above, it is possible to “enhance the spatial resolution in the main direction” by reducing the PD arrangement pitch with respect to the LED arrangement pitch.

Note that the spatial resolution in the main direction can be increased by arranging the reflective optical sensor at an angle with respect to the main scanning direction.
That is, if the angle of the inclination of the reflection type optical sensor with respect to the main scanning direction (the inclination of the arrangement direction of the light emitting unit / light receiving unit) is “β”, the arrangement pitch of the light receiving unit / light emitting unit in the reflection type optical sensor: pt is The projection in the main direction is reduced to “tp · cos β” and the spatial resolution is increased.

When the arrangement pitch of the light emitting part and the light receiving part is relatively large, the light emitting part and the light receiving part may be configured by integrating high density LEDs and PDs, such as resin mold type and surface mount type, respectively. it can.
If ultra-small LEDs and PDs are used, each element size is “milli-order”, and an arrangement pitch of about 1 mm is possible.

  In order to increase the spatial resolution, it is basically necessary to reduce the arrangement pitch of the light emitting unit and the light receiving unit, but this is realized by using an “LED array or PD array” in which LEDs and PDs are arranged in an integrated manner. it can. Two examples of this embodiment are shown in FIG.

  The form example shown in FIG. 12A includes an LED array EA (irradiation means) in which “six LEDs are integrally arranged in a single line at the same pitch on the same substrate” as six light emitting portions E1 to E6. A reflection type optical sensor OS11 in which a PD array DA (light receiving means) in which six PDs are integrally arranged at the same pitch on the same substrate as six light receiving parts D1 to D6 is incorporated in the same housing. Show.

  In the embodiment shown in FIG. 12B, six light emitting units E1 to E6 are "arrayed in one row at an equal pitch" on the same substrate, and six light receiving units D1 to D1 are arranged. As D6, "6 PDs are arrayed in a line at equal pitches", the irradiating means and the light receiving means are formed on the same substrate to form a light emitting part / light receiving part array DEA. A reflective optical sensor OS12 incorporated in the same housing is shown.

  As shown in FIG. 12, the arrangement pitch of the light emitting units is equal to the arrangement pitch of the light receiving units, and the corresponding light emitting units / light receiving units are at the same position in the main direction. However, the present invention is not limited to this, and “the number of light emitting units and the number of light receiving units can be made different” as in each embodiment shown in FIG. 11, and the arrangement pitch can also be made different.

  In FIG. 12, the number of light receiving parts / light emitting parts is six for reasons of convenience of description and avoiding complication of the figure.

As described above, if an LED array or a PD array is used as the irradiating means / light receiving means, the arrangement pitch of the light emitting part / light receiving part can be in the order of several tens μm to several hundreds μm. In the “main detection step for obtaining”, the spatial resolution can be greatly improved.
Note that the LED array and PD array manufactured by the semiconductor process can greatly improve the positional accuracy of the light emitting unit and the light receiving unit, rather than integrating independent LEDs and PDs.
In the embodiment of FIG. 12B, since the LED array is integrally formed with the PD array on the same substrate, the positional accuracy between the irradiation means and the light receiving means can be greatly improved.

By the way, although the reflection characteristics of the toner pattern have different wavelength dependence depending on the color of the toner constituting the toner pattern, the wavelength dependence on the reflection characteristics in the near infrared to infrared wavelengths, particularly in the wavelength range of 800 nm to 1000 nm. There is almost no.
Therefore, it is preferable that the light emitting portion of the irradiation means in the reflective optical sensor emits light in the above wavelength region, and that the plurality of LEDs constituting the irradiation means in the reflective optical sensor emit light at the same emission wavelength. preferable.
When an LED array is used as the irradiating means, it is convenient because the wavelength is the same from the processing process.

In addition, if the “wavelength sensitivity characteristics” of the N light receiving parts constituting the light receiving means are different from each other, the output changes for each light receiving part even if the reflected light from the same toner pattern is received, and toner density detection is performed. This is an error in the arithmetic processing.
Therefore, it is preferable that the peak sensitivity wavelength of the PD constituting the light receiving unit of the light receiving unit does not vary for each light receiving unit in the light receiving unit. However, as the light receiving unit, the peak sensitivity wavelength is the same from the processing process. This can be realized by using a “PD array”.

  In addition, in order for the detection light emitted from the irradiation unit to be efficiently received by the light receiving unit, the emission wavelength of the LED constituting the light emitting unit and the peak sensitivity wavelength of the PD constituting the light receiving unit are “several tens of nm level. It is preferable that “substantially the same in range”. In general, the emission wavelength of a GaAs LED used as a light emitting element is about 950 nm, and the peak sensitivity wavelength of a Si PD used as a light receiving element is 800 nm to 1000 nm. Therefore, it is preferable to select and use a light emitting element or a light receiving element. .

  Moreover, since the wavelength band can be shifted by adjusting the composition of LED and PD and the device structure, the emission wavelength of LED and the peak sensitivity wavelength of PD can be made substantially the same.

As described above, the detection light emitted from the individual light emitting portions of the irradiating means in the reflective optical sensor is irradiated onto the support member and the toner pattern in a spot shape.
The “independent LED” which is a specific example of the light emitting unit is integrated with a “portion having a lens function for converging radiated light”, and a spot can be formed by the lens function.
When the “LED array that does not have such a function as the element itself” is used as the irradiation means, the reflective optical sensor condenses the detection light emitted from the light emitting part toward the support member surface. Spot illumination of the detection light can be realized by having the illumination optical system for guiding light and / or the light receiving optical system for condensingly guiding the reflected light from the surface of the support member toward the light receiving means.

  Of course, when the light emitting unit is formed by arranging independent LEDs, even if each LED has a function of collecting the irradiation light, the illumination optical system is used to make the detection light irradiation unit more effective. Can be irradiated.

An embodiment in such a case will be described below.
The embodiment shown in FIG. 13 will be described. FIG. 13A schematically illustrates the structure of the reflective optical sensor OS of the embodiment viewed from the main direction.
The irradiating means includes five independent light emitting parts E1 to E5 arranged in a line at equal pitches in the main direction, and the irradiating means includes five independent light receiving parts D1 to D5 as an array of light emitting parts. Arranged at the same pitch.
Each of the light emitting units E1 to E5 is an LED, and each of the light receiving units D1 to D5 is a PD. The LED forming the light emitting unit has a “lens function for focusing the emitted light”.

In FIGS. 13A, 13B, and 13C, symbol LE indicates an “illumination optical system”, and symbol LD indicates a light receiving optical system. As shown in FIGS. 13A to 13C, the illumination optical system LE and the light receiving optical system LD are both cylindrical lenses and have “positive power in the sub direction”.
Reference numeral 17 denotes a support member, specifically a transfer belt, and reference numeral DP denotes a toner pattern for detecting toner density.

The operation of detecting the toner density is as described with reference to FIGS. 2 and 3, and the “preliminary detection step is performed on a toner pattern for a preliminary detection step (not shown)” to determine the position in the main direction with respect to the toner pattern DP. After obtaining the range information, this detection step is performed by light emission of a small number of light emitting parts (for example, the light emitting part E3 or the light emitting parts E2 to E4).
When each light emitting unit (LED) Ei (i = 1 to 5) is turned on / off, the emitted detection light is “more condensing” in the sub-direction by the illumination optical system LE, The support member 17 or the toner pattern DP is irradiated. Then, the reflected light is enhanced in the sub-direction by the light receiving optical element LD and is received toward the light receiving part Di (i = 1 to 5).

The illumination optical system and the light receiving optical system can be configured to realize an appropriate shape of the spot of the detection light irradiated to the support member and the toner pattern and an appropriate shape of the light reception spot received by the light receiving unit.
If the illumination optical system and the light receiving optical system have the same shape, the cost of these optical systems can be reduced. In FIG. 13, the number of the light receiving parts and the light emitting parts is five for reasons of convenience of explanation and avoiding the complication of the drawing.

Another embodiment using the illumination optical system and the light receiving optical system will be described.
In the embodiment shown in FIG. 14, the reflective optical element OSA has a 1: 1 ratio to each light emitting part Ei of the light emitting part in which five light emitting parts (LEDs) E1 to E5 are arranged as shown in FIG. Correspondingly, an illumination condenser lens LEi (i = 1 to 5) is provided to change the degree of condensing diverging light emitted from the light emitting part Ei and to increase the illumination efficiency to the support member 17.
In contrast to the cylindrical lens that is the illumination optical system shown in FIG. 14, it is possible to “further improve the illumination efficiency” by providing the power for condensing in the main scanning direction.
Further, the illumination condenser lens LEi (i = 1 to 5) may be an “anamorphic lens having different powers in the main direction and the sub direction”.

  Further, as shown in FIG. 14A, the illumination optical system uses an anamorphic lens LEi corresponding to each light emitting portion Ei, and the light receiving optical system has a configuration as shown in FIG. 13C. It is also possible to use a cylindrical lens having power only in the sub direction. The combination of the form of the illumination optical system and the form of the light receiving optical system can be selected in accordance with the desired illumination efficiency, “detection light spot shape”, desired light reception efficiency and “light reception spot shape”. In FIG. 9, the number of the light receiving parts and the light emitting parts is five for reasons of convenience of explanation and avoiding complication of the drawing.

FIG. 15 further shows two examples of other forms.
In the example shown in FIG. 15A, the reflection type optical sensor OSB has six light emitting units (LEDs) E1 to E6 as the irradiating means, and condensing power corresponding to each of these light emitting units. It is an example which has the optical system LEA for illumination which integrated the convex lens surface which has and is arranged in an array.
In the illumination optical system LEA, the light condensing power is given only to the LED side and the emission side is flat, but it is of course possible to give power to the emission side. Since the illumination optical system LEA in this example has an integrated structure, it is easier to assemble than a separate lens for each light emitting unit to the reflective optical sensor body, and the arrangement accuracy between the lens surfaces is increased. be able to.

Although not shown in FIG. 15A, the light receiving optical system can be similarly configured as “a structure in which a light receiving lens is integrated”.
In FIG. 15B, the six condensing lenses LE1 to LE6 constituting the illumination optical system and the six condensing lenses LD1 to LD6 constituting the light receiving optical system are appropriately determined with respect to each other. An integrated illumination light receiving optical system LEDA is shown.
By using such an illumination light receiving optical system LDEA, it is possible to further increase the placement accuracy of each of the illumination condenser lenses and each of the light condenser lenses. The array of condensing lenses as shown in FIG. 15 can be formed on a glass substrate or a resin substrate by using a processing method such as photolithography or nanoimprint.
In FIG. 15, the number of the light receiving parts / light emitting parts is six for the sake of convenience of explanation and avoiding complication of the drawing.

  It goes without saying that the illumination optical system and the light receiving optical system take an appropriate form according to the arrangement of the light emitting part and the light receiving part in the case of the light emitting part / light receiving part arrangement as shown in FIG. 9 and FIG. No.

  Needless to say, when the illumination optical system and the light receiving optical system are formed of a lens array or a lens surface array, it is preferable that the arrangement pitches of the lenses and lens surfaces are equal.

The reflective optical sensor device will be described with reference to FIG.
The reflective optical sensor device includes a reflective optical sensor 141 and an arithmetic processing unit 142.
As the reflective optical sensor 141, the one described above with reference to FIGS. 3, 4, 6, 7, etc. can be used.

  The arithmetic processing unit 142 controls the light emission of the M light emitting units of the reflective optical sensor 141 so as to execute the preliminary detection step and the main detection step described above, and further the calculation necessary for detection.

OS1 Reflective optical sensor E1 to E5 Light emitting part (LED)
D1 to D5 Light receiving part (PD)
YP1 toner pattern for preliminary detection process DP1 toner pattern for toner concentration detection 17 support member (transfer belt)

JP-A 64-35466 JP 2004-309292 A JP 2004-21164 A JP 2002-72612 A JP 2003-84530 A Japanese Patent Laid-Open No. 2002-23458

Claims (12)

In an image forming method for forming an image with toner, one or more predetermined toner patterns are formed on the surface of a support member moving in a predetermined sub-direction, and the support member is irradiated with detection light by an irradiating means, and the support member and Light received by the toner pattern is received by the light receiving means, and information on the position of the toner pattern and / or the toner density is detected based on the difference between the reflection characteristics of the support member and the toner pattern with respect to the detection light. A toner information detection method comprising:
M (≧ 3) light emitting portions for detecting light that emit detection light, and the support member can be irradiated with detection light spots at M locations, and between adjacent spots in a direction orthogonal to the sub-direction. Is arranged in one direction intersecting with the sub-direction so as to be equal to or smaller than the size of the toner pattern in the orthogonal direction, and serves as an irradiating means, and N (≧ 3) light receiving portions are used as the support member and / or Alternatively, in order to receive the reflected light of the detection light by the toner pattern, the light receiving means is arranged in one direction so as to correspond to the irradiation means and face the support member,
A preliminary detection step of preliminarily detecting the position range information of the toner pattern by emitting r (≦ M) light emitting portions in the irradiation unit;
A main detection step of selecting information on the position and / or toner density of the toner pattern by selecting and emitting s (<r) light emitting portions that emit light in the irradiating means based on the detection result of the preliminary detection step; And a toner information detecting method. The toner information detection method according to claim 1.
A toner information detection method comprising sequentially emitting r light emitting units and / or s light emitting units within a time during which a toner pattern passes a detection light irradiation region in a sub direction. In the toner information detection method according to claim 1 or 2,
A toner information detection method, wherein r (<M) light emitting portions capable of detecting toner pattern position range information are selected in the preliminary detection step. The toner information detection method according to any one of claims 1 to 3,
A toner information detection method comprising: forming a toner pattern dedicated to a preliminary detection step for detecting position range information by a preliminary detection step on a support member surface at a head in a sub-direction rather than other toner patterns. The toner information detection method according to any one of claims 1 to 3,
Toner information detection characterized in that the toner pattern for detecting information on the position and / or toner density of the toner pattern in this detection step also serves as the toner pattern for detecting position range information in the preliminary detection step Method. The toner information detection method according to any one of claims 1 to 5,
A toner information detection method, wherein toner information as a detection target is at least position information on a support member of a toner pattern. The toner information detection method according to claim 6.
Toner information as a detection target is toner density and position information,
In the present detection step, a toner information detection method characterized in that the number of s light emitting portions to emit light varies depending on whether toner information to be detected is toner density or position information. In the toner information detection method according to claim 6 or 7,
When the toner information as a detection target is position information, the number of light emitting sections to emit light: s = 1. The toner information detection method according to any one of claims 6 to 8,
A toner information detection method, wherein the number of light emitting sections to emit light is s> 1 when the toner information to be detected is toner density. A reflective optical sensor device used for carrying out the toner information detection method according to any one of claims 1 to 9,
An irradiation means in which M (≧ 3) light-emitting portions that can be flashed independently or simultaneously are arranged in one direction;
A light receiving means in which N (≧ 3) light receiving portions are arranged in one direction corresponding to the irradiation means;
A reflection type optical sensor device comprising: a control unit that controls light emission of the M light emitting units according to a preliminary detection step and a main detection step. In an image forming apparatus for forming an image with toner,
An image forming apparatus comprising the reflective optical sensor device according to claim 10 as a reflective optical sensor for detecting toner information. The image forming apparatus according to claim 11.
An image forming apparatus, wherein an image to be formed is a multicolor image or a color image using a plurality of types of toners having different colors, and toner information for each color is detected.

Images