JP5081383B2 - Mark detection apparatus, movement amount detection apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to the amount of rotation of a rotating body such as a photosensitive belt, a transfer belt, a paper conveying belt, a photosensitive drum, and a transfer drum used in an image forming apparatus such as a copying machine, a printer apparatus, or a facsimile apparatus, and various moving bodies. The present invention relates to a mark detection device used when detecting a movement amount, a movement amount detection device and an image forming apparatus using the mark detection device, and particularly to improvement and stabilization of mark detection accuracy.

  2. Description of the Related Art Image forming apparatuses including image forming rotating bodies such as a photoreceptor belt, an intermediate transfer belt, and a sheet conveying belt are widely used. In such an image forming apparatus, the rotation amount (movement amount) of the rotating body is accurately controlled in order to accurately position the image on the rotating body or on the transfer material conveyed by the rotating body. Is required. The amount of rotation of the rotating body often varies for some reason, and it is difficult to suppress an error in the image position. In particular, in a color image forming apparatus, there is a problem in that due to fluctuations in the amount of rotation of a rotating body, images do not overlap at positions that should be overlapped, and positional deviation occurs between colors of images to be formed.

  In order to suppress the positional error of the image due to the speed fluctuation (rotation amount fluctuation) of the rotating body, the image forming apparatus disclosed in Patent Document 1 is a photoconductor for indirectly measuring the surface speed of the rotating body. A rotary encoder is directly connected to a rotating shaft of a rotating body such as a drum or a transfer drum, and the rotational angular speed of the driving motor is controlled based on the rotating angular speed of the rotating shaft of the rotating body detected by the rotary encoder. However, even if the rotational angular velocity of the drive motor is controlled by detecting the rotational angular velocity of the rotating shaft, the surface speed of the rotating member varies due to the eccentricity of the rotating shaft of the rotating member, and the amount of rotation of the rotating member can be accurately determined. It is difficult to control.

  In addition, when an endless belt is used as a rotating body such as a photoreceptor belt or an intermediate transfer belt, the belt speed fluctuation (variation in rotation amount) is caused by belt thickness fluctuation, belt eccentricity and belt movement. This occurs due to uneven speed of the driving motor. In particular, in the color image forming apparatus, the positioning error due to the belt speed fluctuation becomes a waveform having a plurality of frequency components as shown in FIG. An image formed by superimposing toner images of each color of cyan (c), magenta (M), yellow (Y), and black (K) during the belt speed fluctuation is an image in which the positions of the colors are not aligned. Therefore, the belt speed fluctuation causes image quality deterioration such as color shift and color change.

  In order to prevent this belt speed fluctuation, the belt drive control device of the image forming apparatus disclosed in Patent Document 2 directly connects a rotary encoder to the rotation shaft of a driving roller that drives the belt, and outputs pulses from the rotary encoder. The rotation amount and average speed of the rotating body are calculated from the signal, and the drive motor is controlled based on the calculated result. As described above, since the rotation amount and average speed of the rotating body are indirectly obtained by the pulse signal from the rotary encoder provided on the rotating shaft of the driving roller, it is difficult to accurately control the rotating amount of the rotating body. .

In order to directly detect the amount of rotation of the rotating body, the belt conveying device disclosed in Patent Document 3 forms a reflection mark on the surface of the belt, and binarizes an electric signal obtained by detecting the reflection mark with a sensor. The belt surface speed is calculated from the pulse interval of the binarized signal, and the belt speed is controlled by feeding back the amount of rotation of the belt.
JP-A-6-175427 JP-A-9-114348 JP-A-6-263281

  However, belts used for rotating bodies for image formation and the like are flexible and easily deformed, and have deviations in thickness. When the belt is rotating, marks formed on the belt surface are detected. Variation in the distance to the sensor and angle variation will occur. As described above, when the distance between the mark and the sensor changes or the angle changes, the amount of light received by the sensor changes, so the amplitude of the electrical signal output from the sensor changes as shown in FIG. For this reason, the pulse interval of the binarized signal obtained by comparing the electrical signal output from the sensor with the upper and lower amplitude regulation levels determined with the reference level voltage (0 V) as the center is also varied. Further, when the moving speed of the rotating body is not constant, if a high-pass filter is used to remove the offset from the electric signal from the sensor, the electric signal is attenuated at a speed other than the pass band of the high-pass filter and cannot be detected.

  The present invention improves such disadvantages and causes variations in the distance and angle between the mark formed on the surface of the rotating body and various moving bodies and the sensor for detecting them, or the speed of the rotating body and various moving bodies. Provided is a mark detection device capable of detecting a mark with high accuracy and detecting the amount of movement of a rotating body and various moving bodies stably even when fluctuations occur, and a movement amount detection device and an image forming apparatus using the mark detection device. It is intended to do.

  The mark detection device according to the present invention irradiates light to a scale constituted by a plurality of marks arranged in a predetermined periodic pattern in the moving direction of the moving body, and reflects the light beam reflected from the scale mark or the scale. In a mark detection apparatus for detecting a light beam transmitted through a mark, a light projecting device having a light source that emits the light beam and a light shaping unit that shapes the light beam emitted from the light source into a predetermined shape and irradiates the scale And a light receiving unit that receives a light beam that has been irradiated onto the scale from the light projecting unit and reflected from the mark on the scale or a light beam that has passed through the mark on the scale and converts the light beam into an electrical signal. A plurality of heads, and a light source provided in each light projecting unit of the plurality of optical heads emits light beams having different wavelengths and is emitted from each light projecting unit. Of the light beam, characterized in that the irradiation position with respect to the scale is shifted by less mark period of the scale.

  It is desirable that the positions of the plurality of light beams applied to the scale are shifted by a half period of the mark period of the scale.

  The light shaping means transmits a light beam having a predetermined pattern from a collimator lens that optically corrects a light beam emitted from the light source to a substantially parallel light beam, and a light beam that has been made a substantially parallel light beam by the collimator lens. It is preferable to have a fixed mask provided with a plurality of slits. The fixed mask may have a plurality of regions having one or a plurality of slits that transmit a light beam, and the plurality of light beams that irradiate the scale may be shaped into a predetermined shape with one fixed mask. .

  The movement amount detection device of the present invention includes any one of the mark detection devices described above, and calculates a movement amount of the moving body by binarizing a signal output from the light receiving unit.

  The image forming apparatus according to the present invention includes the movement amount detection device, and the moving body is any one of a photosensitive belt, a photosensitive drum, a transfer belt, a paper conveyance belt, and a transfer drum.

  This invention irradiates a plurality of light beams having different wavelengths to substantially the same position of a scale constituted by a plurality of marks arranged in a predetermined periodic pattern, and reflects light or scale reflected from the scale marks. By detecting the light that has passed through the mark, offset fluctuations can be removed, and even if a light beam is irradiated to an adjacent position on the scale, the detected light beam is scattered or stray light from the other light beam. A mark detection signal having a high S / N can be obtained without receiving light.

  In addition, by irradiating the irradiation position of multiple light beams to the scale at almost the same position and detecting the light reflected from the mark on the scale or the light transmitted through the mark on the scale, a plurality of mark detection signals that are out of phase are detected. It can be obtained from a position in the vicinity of the scale, and there is little deviation with respect to short-time fluctuations caused by scratches or dirt on the scale, and reliable offset removal can be achieved.

  In addition, by shifting the position of the plurality of light beams irradiating the scale by a half period of the mark period of the scale, a plurality of mark detection signals can be reliably obtained from positions near the scale.

  Furthermore, the amount of movement of the moving body can be stably detected by binarizing the plurality of mark detection signals and calculating the amount of movement of the moving body.

  In addition, by detecting the amount of movement of the photosensitive belt, photosensitive drum, transfer belt, paper transport belt, or transfer drum of the image forming apparatus from a plurality of mark detection signals, a high-quality image free from color misregistration can be stably obtained. Can be formed.

  FIG. 1 is a layout view showing the configuration of the image forming apparatus of the present invention. As shown in the figure, the image forming apparatus 1 includes a plurality of image forming units 4K, 4K arranged in order from the upstream side in the rotation direction (conveying direction) of the conveying belt 3 along the conveying belt 3 that conveys the recording paper 2. 4M, 4Y, 4C and transfer units 5K, 5M, 5Y, 5C provided at positions facing the image forming units 4K, 4M, 4Y, 4C across the conveying belt 3 and the downstream side of the conveying belt 3. The fixing device 6 is provided.

  The image forming unit 4K forms a black image, the image forming unit 4M forms a magenta image, the image forming unit 4Y forms a yellow image, and the image forming unit 4C forms a cyan image. Each of the image forming units 4K, 4M, 4Y, and 4C includes a photosensitive drum 7 as an image carrier, a charger 8, an exposure device 9, a developing device 10, and a photosensitive cleaner 11 disposed around the photosensitive drum 7. Etc. The exposure device 9 is a laser scanner, reflects the laser light from the laser light source with a polygon mirror, and emits it through an optical system using an fθ lens, a deflection mirror, or the like.

  The conveyor belt 3 is formed of an endless belt wound around a driving roller 12 and a driven roller 13 that are driven to rotate, and rotates in the direction of arrow A. Below the conveying belt 3, there is a paper feed tray 14 in which the recording paper 2 is stored. The recording sheet 2 at the uppermost position among the recording sheets 2 stored in the sheet feeding tray 14 is sent out at the time of image formation, and is electrostatically attracted to the transport belt 4 and transported, and the image forming units 4K, 4M, 4Y. , 4C is transferred.

  When a color image is formed by the image forming apparatus 1, first, the surface of the photosensitive drum 7 of the image forming unit 4K is uniformly charged by the charger 8 and then the exposure device 9 uses a laser beam corresponding to the black image. Exposure to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 7 is visualized with black toner by the developing device 10 to form a black toner image on the photosensitive drum 7. The toner image formed on the photosensitive drum 7 is transferred to the recording paper 2 by the transfer device 5K at the transfer position where the recording paper 2 conveyed by the conveying belt 3 contacts the photosensitive drum 7, and black on the recording paper 2. Form an image. Unnecessary toner remaining on the photosensitive drum 7 having the toner image transferred to the recording paper 2 is removed by the photosensitive cleaner 11 to prepare for the next image formation.

  In this way, the recording paper 2 on which the black toner image is transferred by the image forming unit 4K is transported to the next image forming unit 4M by the transport belt 3, and the image forming unit 4M is exposed to light in the same manner as the image forming unit 4K. The magenta toner image formed on the body drum 7 is transferred while being superimposed on the black toner image on the recording paper 2. Similarly, the yellow toner image formed by the image forming unit 4Y is superimposed and transferred onto the recording paper 2 conveyed by the conveying belt 3, and the cyan toner image formed by the image forming unit 4C is superimposed. A full-color color image is formed on the recording paper 2 by transfer. The recording sheet 2 on which the full-color image is formed passes through the image forming unit 4C, is peeled off from the conveying belt 3, is fixed by the fixing device 6 with heat and pressure, and is discharged.

  As shown in the perspective view of FIG. 2, the driving roller 12 that rotates the conveying belt 3 that conveys the recording paper 2 is connected to the driving motor 16 via the speed reducer 15, and is driven by the driving force of the driving motor 16. Driven by rotation. The end of the drive belt 3 has a scale 17. As shown in the schematic configuration diagram of FIG. 3, the scale 17 has a plurality of reflective marks 18 and a plurality of slits 19 arranged alternately in the rotation direction of the conveyor belt 3, that is, in the movement direction of the outer peripheral surface of the conveyor belt 3. It is provided with a mark period. The reflection mark 18 functions as a reference mark when detecting reflected light, and the slit 19 functions as a reference mark when detecting transmitted light. In other words, the reflection mark 18 and the slit 19 need only change in reflectance and transmittance, and when detecting reflected light, for example, a printed pattern with different colors such as white and black may be used, or an entire film such as an aluminum vapor deposition film may be used. A reflective pattern may be used. Such reflection marks 18 and slits 19 cause a single or continuous reflectance change depending on the number thereof.

  The mark detection device 21 that detects the reflection mark 18 or the slit 19 of the scale 17 is provided at a position facing the scale 17 and a predetermined distance away from the transport belt 3. As shown in FIGS. 3 and 4, the mark detection device 21 includes a plurality of, for example, two sets of optical head portions 22a and 22b. Each optical head part 22a, 22b has light projecting parts 23a, 23b and light receiving parts 24a, 24b.

  The light projecting units 23a and 23b include light sources 25a and 25b that emit light beams and light shaping means 26a and 26b, respectively. The light source 23a emits a light beam having a wavelength λ1, and the light source 23b emits a light beam having a wavelength λ2 different from that of the light source 23a. Each of the light sources 23a and 23b uses, for example, a light emitting diode (LED), but a semiconductor laser or a light bulb may be used. In particular, since it is desirable to use a light beam with good parallelism, it is preferable to use a light beam having a small light emitting area such as a semiconductor laser or a point light source LED. The light shaping means 26a and 26b collect the light beams emitted from the light sources 25a and 25b and shape them into a desired shape. As the light shaping means 26a and 26b, for example, as shown in FIG. 4, a collimating lens 27 and a fixed mask 29 having a slit 28 for passing light as shown in FIG. , 25b, the collimating lens 27 converts the light beam into a parallel beam, and the beam is shaped by the fixed mask 29. For example, as shown in FIG. 5B, the scale 17 is irradiated with the line beams 30a, 30b.

  Each light receiving part 24a, 24b has wavelength filters 31a, 31b and light receiving elements 32a, 32b, respectively. The wavelength filter 31a selects and transmits the light beam of wavelength λ1 emitted from the light source 25a, and the wavelength filter 31b selects and transmits the light beam of wavelength λ2 emitted from the light source 25b. The light receiving elements 32 a and 32 b include, for example, a photodiode or a phototransistor. The light receiving element 32 a is reflected by the light transmitted through the slit 19 and the wavelength filter 31 a of the scale 17 or the reflection mark 18 of the scale 17. The light that has passed through the wavelength filter 31 a is received and subjected to photoelectric conversion, and the light receiving element 32 b is reflected by the light transmitted through the slit 19 and the wavelength filter 31 b of the scale 17 or the reflection mark 18 of the scale 17. The light transmitted through 31b is received and subjected to photoelectric conversion. As shown in the block diagram of FIG. 6, the light receiving elements 32a and 32b are connected to a comparator 34 such as an amplifier or a comparator of the control unit 33 of the drive motor 17. In addition, you may provide the lens which condenses the light which permeate | transmitted the light which permeate | transmitted the slit 19 of the scale 17, and the reflective mark 18 in light-receiving part 24a, 24b.

  The light projecting portions 23 a and 23 b of the mark detection device 21 are preferably provided in a plane that is inclined with respect to the surface of the transport belt 3 and orthogonal to the moving direction (rotation direction) of the transport belt 3. . Thus, by providing the optical axes of the light projecting units 23 a and 23 b in a plane orthogonal to the moving direction of the transport belt 3, the light beam irradiated from the light projecting units 23 a and 23 b to the scale 17 is transmitted from the transport belt 3. Even if there is no angle with respect to the moving direction and there is a gap fluctuation with the conveyor belt 3, the observation position does not change, and highly accurate mark detection can be performed.

  The irradiation positions of the beams 30a and 30b irradiated to the scale 17 by the light projecting portions 23a and 23b of the two sets of optical head portions 22a and 22b are the mark period of the scale 17 in the moving direction of the scale 17, that is, the moving direction of the driving belt 3. The optical head portions 22a and 22b are respectively arranged with respect to the scale 17 so as to irradiate a position shifted by a half cycle.

  The light projecting sections 23 a and 23 b of the optical head sections 22 a and 22 b irradiate the scale 17 and the light transmitted through the slit 19 of the scale 17 is received by the two sets of light receiving sections 24 a and 24 b or reflected from the scale 17. The electric signal (mark detection signal) obtained by receiving the light reflected by the mark 18 by the light receiving elements 32a and 32b of the two sets of light receiving portions 24a and 24b and performing photoelectric conversion is shown in the waveform diagram of FIG. Is output from the light receiving element 32b by a half cycle, that is, 180 degrees out of phase with respect to the mark detection signal 35a output from the light receiving element 32a. The drive motor 16 is controlled using a digital signal obtained by binarizing the mark detection signals 35a and 35b whose phases are shifted by 180 degrees by the comparator 34.

  Thus, the positions where the light beams 30a and 30b having the different wavelengths λ1 and λ2 are shifted from the light sources 25a and 25b of the two sets of light projecting units 23a and 23b by ½ period of the mark period of the scale 17 in the moving direction of the scale 17. The light passing through the slit 19 of the scale 17 is received by the light receiving elements 32a and 32b via the wavelength filters 31a and 31b, or the light reflected by the reflection mark 18 of the scale 17 is passed through the wavelength filters 31a and 31b. By receiving and binarizing the mark detection signals 35a and 35b that are received by the light receiving elements 32a and 32b and being 180 degrees out of phase, offset fluctuations can be removed and the scale 17 is adjacent to the position. Even if the light beams 30a and 30b are irradiated to the light receiving elements 32a and 32b, the light receiving elements 32a and 32b receive scattered light and stray light of the other light beam. The mark detection signals 35a and 35b having a high S / N can be output. Further, since the mark detection signals 35a and 35b that are 180 degrees out of phase can be obtained from the adjacent positions of the scale 17, there is little deviation from short-term fluctuations caused by scratches or dirt on the scale 17, and it is ensured. It is possible to remove the offset. Further, since the light beams applied to the scale 17 by the two sets of light projecting units 23a and 23b in order to obtain the mark detection signals 35a and 35b enter the scale 17 at different beam incident angles, it is possible to prevent signal interference and interference. The mark can be detected with high accuracy.

  In the above description, the case of performing offset removal using the mark detection signals 35a and 35b that are 180 degrees out of phase has been described. However, the phase difference between a plurality of beams does not need to be 180 degrees, and a phase difference necessary for the purpose, for example, 90 degrees. You can choose degrees or 120 degrees.

  In the above description, the case where one slit 28 is provided in the fixed mask 29 of the light shaping means 26a, 26b provided in the light projecting portions 23a, 23b is shown. However, as shown in FIG. The slit 28 may be provided in the fixed mask 29, and as shown in FIG. 8B, the mark detection signals 35a and 35b having a phase difference may be obtained by the plural beams 30a and 30b. Also in this case, the two beam patterns irradiated to the scale 17 from the light projecting units 23a and 23b do not need to be shifted by the size of the beam pattern, and may be shifted by the required phase difference.

  Further, the case where the fixed masks 29 are provided in the light shaping means 26a and 26b of the light projecting portions 23a and 23b has been described. However, as shown in FIG. 9, the light beam 30a having a plurality of slits 28 in the fixed mask 29A. A passage region 36a and a passage region 36b for the light beam 30b may be provided, respectively, and the fixed mask 29A may be used in common by the light shaping means 26a and 26b of the light projecting portions 23a and 23b, as shown in FIG. Thus, by using the fixed mask 29A in common for the light shaping means 26a and 26b of the two sets of light projecting portions 23a and 23b, the number of components of the mark detection device 21 can be reduced and phase adjustment during assembly can be easily performed. It can be carried out.

  In the above description, the case where the light receiving elements 31a and 31b are provided in the light receiving portions 24a and 24b of the two sets of optical head portions 22a and 22b has been described. However, as shown in FIG. 11, two light receiving regions 37a and 37b are provided. The light receiving element 32 having the above may be commonly used in the optical head portions 22a and 22b.

  In the above description, the case where the light projecting portions 23a and 23b of the mark detection device 21 are arranged so as to have different optical axes has been described. However, the optical axes of the light projecting portions 23a and 23b may be coaxial. For example, as shown in FIG. 12, a light projecting unit 23a that emits a light beam having a wavelength λ1 and a light projecting unit 23b that emits a light beam having a wavelength λ2 are arranged so that their optical axes are orthogonal to each other, and the light projecting units 23a and 23b are arranged. The light beams respectively emitted from the light beam are combined coaxially by a wavelength selection mirror 38 such as a half mirror that transmits the light beam having the wavelength λ 1 and reflects the light beam having the wavelength λ 2, and irradiates the scale 17. The light beam transmitted through the slit 19 of the scale 17 is separated by the wavelength selection mirror 39 into a light beam having the wavelength λ1 and a light beam having the wavelength λ2, and the light beam having the wavelength λ1 is received by the light receiving element 32a. Is received by the light receiving element 32b. As the wavelength selection mirrors 38 and 39, polarization beam splitters may be used by changing the polarization of the light beams emitted from the light projecting units 23a and 23b.

  In this way, by irradiating the scale 17 with the light beam with the wavelength λ1 and the light beam with the wavelength λ2 coaxially, the light beam with the wavelength λ1 and the light beam with the wavelength λ2 are generated even if the height variation or inclination of the scale 17 occurs. A mark having a phase difference output from the light receiving elements 32a and 32b can be irradiated to the same position of the scale 17 and the light quantity received by the light receiving elements 32a and 32b is not affected by the position fluctuation or the angle fluctuation of the scale 17. The detection signals 35a and 35b are easier to synchronize, enhance the effect of offset suppression, and obtain the mark detection signals 35a and 35b having a high S / N.

  In the above description, the mark detection device 21 is provided with two sets of light projecting units 23a and 23b. However, a light source that emits a light beam having a plurality of wavelengths and a fixed mask that separates the light beams having a plurality of wavelengths are provided. A set of light projecting units can be used by using the light shaping means. For example, as shown in FIG. 13, the light projecting unit 23c of the mark detection device 21 includes a wavelength multiplexed light source 25c that emits light beams having wavelengths λ1 and λ2, a filter mask 40 for wavelength λ1, and a filter mask for wavelength λ2. What is necessary is just to comprise with the light shaping means 26c which has 41. The wavelength multiplexing light source 25c of the mark detection device 21 may synthesize light having a single wavelength, or may use a light source having a wavelength distribution. For example, even with a normal LED light source, the emission wavelength has a wavelength broadening of about 10 nm. Therefore, if there is sufficient spectral resolution on the filter masks 40 and 41 and the light receiving side, the LED light source can be used. Further, as shown in FIG. 14A, the filter mask 40 cuts off the light beam with the wavelength λ1 and transmits the light beam with the wavelength λ2, and transmits the light beams with the wavelength λ1 and the wavelength λ2. The filter mask 41 transmits light beams having wavelengths λ1 and λ2 at positions corresponding to the wavelength selection region 42 of the filter mask 40, as shown in FIG. 14B. A transmission region 44 that transmits light is provided, and a wavelength selection region 45 that blocks the light beam having the wavelength λ 2 and transmits the light beam having the wavelength λ 1 is provided at a position corresponding to the transmission region 43 of the filter mask 40. Then, by separating the light beam emitted from the wavelength multiplexed light source 25c into the light beam pattern of wavelength λ1 and the light beam pattern of wavelength λ2 by the filter masks 40 and 41, a multiline of the light beam of wavelength λ1 and the light beam of wavelength λ2 The beam can irradiate the scale 17 coaxially. The light beam irradiated on the scale 17 and transmitted through the slit 19 is separated into a light beam having a wavelength λ1 and a light beam having a wavelength λ2 by a wavelength selection mirror 39, and the light beam having a wavelength λ1 is received by a light receiving element 32a. The light beam is received by the light receiving element 32b. Here, the spectral resolution can be enhanced by providing a filter 46 that transmits the light beam having the wavelength λ1 in front of the light receiving element 32a.

  In the above description, the case where the light shaping means 26c is provided with the filter mask 40 for the wavelength λ1 and the filter mask 41 for the wavelength λ2 is described. However, as shown in FIG. A filter mask 49 having a first wavelength selection region 47 that transmits the light beam of λ2 and a second wavelength selection region 48 that blocks the light beam of wavelength λ2 and transmits the light beam of wavelength λ1 is used. Accordingly, the light beam having the wavelength λ1 and the light beam having the wavelength λ2 can be separated by one filter mask 49, and the multi-line beam of the light beam having the wavelength λ1 and the light beam having the wavelength λ2 can be irradiated on the scale 17 coaxially. .

  In this way, by irradiating the scale 17 with the multi-line beam of the light beam of the wavelength λ1 and the light beam of the wavelength λ2 coaxially with the filter mask 40 for the wavelength λ1 and the filter mask 41 for the wavelength λ2, or the filter mask 49, A beam in which the multi-line beam of the light beam having the wavelength λ1 and the multi-line beam of the light beam having the wavelength λ2 are overlapped with a half cycle shift can be formed, and the mark can be detected with high accuracy. Further, by using the filter mask 49 having the first wavelength selection region 47 and the second wavelength selection region 48, the configuration of the mark detection device 21 is simplified and a plurality of filter masks 40 and 41 are used. As in the case, the filter masks 40 and 41 need not be aligned, and the mark detection device 21 can be easily adjusted.

  In the mark detection device 21 shown in FIGS. 12 and 13, the case where the light beam received by the light receiving elements 32a and 32b is separated into the light beam of wavelength λ1 and the light beam of wavelength λ2 by the wavelength selection mirror 39 has been described. As shown in FIG. 16, the light beams received by the light receiving elements 32a and 32b may be separated by using a spectral grating 50 that changes the reflection angle according to the wavelength. By using the spectral grating 50 that changes the reflection angle according to the wavelength in this way, the light receiving elements 32a and 32b can be arranged side by side on one plane, and the mark detection device 21 can be made compact. A transmission type may be used as the spectral grating 50.

  Further, the mark detection device 21 shown in FIGS. 12 and 13 has been described for the case where the light beam transmitted through the scale 17 is separated and received by the light receiving elements 32a and 32b, but the light beam reflected by the scale 17 is separated. The light receiving elements 32a and 32b may receive light.

  Further, in each of the above explanations, the case where the mark detection device 21 detects the mark on the scale 17 provided on the conveyance belt 3 that conveys the recording paper 2 and controls the rotation amount of the conveyance belt 3 has been described. Similarly, a scale mark provided on a rotating body such as the same can be detected to control the amount of rotation of the rotating body.

  Also, when detecting the amount of movement of the moving body with various length measuring devices or measuring devices, it is possible to detect the marks provided on the various scales with high accuracy and stably measure the amount of movement of the moving body.

1 is a layout diagram illustrating a configuration of an image forming apparatus according to the present invention. It is a perspective view which shows the structure of a conveyance belt. It is a perspective view which shows the structure of a transmissive | pervious mark detection apparatus and a scale. It is a block diagram of a reflective mark detection apparatus. It is a block diagram which shows the light beam with which the fixed mask and the scale were irradiated. It is a block diagram which shows the structure of the control part of a drive motor. It is a wave form diagram which shows a mark detection signal and a binarization signal. It is a block diagram which shows the light beam irradiated to the 2nd fixed mask and the scale. It is a block diagram of the 3rd fixed mask. It is a block diagram of the reflective mark detection apparatus using a 3rd fixed mask. It is a block diagram of the light receiving element which has two light receiving areas. It is a block diagram of the mark detection apparatus which irradiates a scale with the light beam from which a wavelength differs coaxially. It is a block diagram of the other mark detection apparatus which irradiates a scale with the light beam from which a wavelength differs coaxially. It is a block diagram of a filter mask. It is a block diagram of another filter mask. It is a block diagram of the light-receiving part which has a spectral grating. It is a change characteristic figure of the positioning error by the speed fluctuation of a belt. It is a wave form diagram which shows the change of a sensor output signal and a binarization signal when the distance fluctuation | variation etc. of a mark and a sensor arise.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Image forming apparatus, 2; Recording paper, 3; Conveying belt, 4; Image forming unit,
5; Transfer device, 6; Fixing device, 7; Photosensitive drum, 8; Charger, 9; Exposure device,
10; Developing device, 11; Photoconductor cleaner, 12; Driving roller, 13;
14; paper feed tray, 16; drive motor, 17; scale, 18; reflection mark,
19; slit, 21; mark detection device, 22; optical head, 23;
24; light receiving unit, 25; light source, 25c; wavelength multiplexed light source, 26; light shaping means,
27; collimating lens, 28; slit, 29; fixed mask, 30; light beam,
31; Wavelength filter, 32; Light receiving element, 33; Control unit, 34;
35; mark detection signal; 37; light receiving region; 38; wavelength selection mirror;
39; Wavelength selection mirror, 40, 41; Filter mask, 49; Filter mask,
50: Spectroscopic grating.

Claims (6)

Light is irradiated to the scale composed of multiple marks arranged in a predetermined periodic pattern in the moving direction of the moving body, and the light beam reflected from the scale mark or the light beam transmitted through the scale mark is detected. In the mark detection device to
A light source that emits a light beam; a light projecting unit that has a light shaping unit that shapes the light beam emitted from the light source into a predetermined shape and irradiates the scale; and A plurality of optical heads including a light beam reflected from the scale mark or a light beam transmitted through the scale mark and converted into an electrical signal;
A light source provided in each light projecting unit of the plurality of optical heads emits light beams having different wavelengths, and a plurality of light beams emitted from each light projecting unit are irradiated on the scale at a mark period of the scale. A mark detection device characterized by being shifted by within a distance. The mark detection apparatus according to claim 1, wherein positions of the plurality of light beams applied to the scale are shifted by a half period of a mark period of the scale . Before Symbol light shaping unit is transmitted and a collimator lens for optical correction into a substantially parallel light beam the light beam emitted from the light source, a light beam of a predetermined pattern from among the light beam into a substantially parallel beam by the collimator lens 1 The mark detection device according to claim 1, further comprising a fixed mask provided with a plurality of slits. The fixed mask has a plurality of regions having one or more slits for transmitting light beams, according to claim 3, wherein the shaping to a predetermined shape a plurality of light beams at a single fixed mask to be irradiated on the scale Mark detection device . 請 Motomeko has a mark detecting device according to any one of 1 to 4, the moving amount detection device and calculates the amount of movement of the moving body by binarizing the signal output from the light receiving portion. An image forming apparatus comprising the movement amount detection device according to claim 5 , wherein the moving body is any one of a photosensitive belt, a photosensitive drum, a transfer belt, a paper conveyance belt, and a transfer drum.

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