JP5505594B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus, and more particularly to an optical scanning apparatus that scans a surface to be scanned with a light beam, and an image forming apparatus including the optical scanning apparatus.

  In electrophotographic image recording, an image forming apparatus using a laser as a light source is widely used. In this case, the image forming apparatus includes an optical scanning device that scans the surface of the photosensitive drum with a light beam emitted from a light source and forms a latent image on the surface of the photosensitive drum.

  A general optical scanning device includes, as an optical system, a pre-deflector optical system into which a light beam emitted from a light source enters, a deflector (for example, a polygon mirror) that deflects the light beam through the pre-deflector optical system, and It has a scanning optical system that guides the light beam deflected by the deflector to the surface of the photosensitive drum (for example, see Patent Document 1).

  In recent years, image forming apparatuses have come to be used for simple printing as an on-demand printing system, and accordingly, an image forming apparatus having further excellent image quality is required.

  Therefore, in order to improve the image quality, it has been considered that a cylindrical lens included in the pre-deflector optical system is coated (see Patent Document 2).

  By the way, in Patent Document 3, an optical element that causes a part of a light beam emitted from a single mode semiconductor laser to be multiple-reflected between a plurality of surfaces and then travels together with the remaining light beam, and this optical element are disclosed. Mode hopping detection of a semiconductor laser comprising a photodetector that detects the amount of light beam that has passed and a signal processing circuit that processes the output signal of the photodetector and detects the presence or absence of mode hopping according to the magnitude of the signal An apparatus is disclosed.

  In Patent Document 4, a refractive optical system that does not have an imaging function is disposed in the optical path of a light beam, and the light transmitted through the refractive optical system is changed by changing the spatial state of the refractive optical system. A multi-beam scanning device for adjusting the position and / or orientation of the beam is disclosed.

From a first viewpoint, the present invention is an optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam, and includes a light source including a vertical cavity surface emitting laser; and a light beam from the light source is cupped. A coupling optical system to be coupled; arranged on an optical path of a light beam through the coupling optical system, and having an entrance surface and an exit surface that are non-parallel to each other, and at least one of the entrance surface and the exit surface A first optical element that includes a transparent substrate on which a film for reducing transmittance is formed, emits transmitted light in a direction different from the incident direction of incident light, and transmitted light emitted from the first optical element. Incident light is incident, and includes a transparent substrate having an incident surface and an emission surface set non-parallel to each other so as to emit transmitted light in the same direction as the incident direction of incident light incident on the first optical element. Transmitted light in a direction different from the direction It includes a second optical element that emits, and a light amount adjusting optical system for emitting a light amount of incident light is changed to a different light intensity; includes a, a thickness of the transparent substrate included in the first optical element When d ₁ , the refractive index is n ₁ , the incident angle of light incident on the first optical element is θ ₁ , the wavelength is λ _1, and m is an integer, 2n ₁ · d ₁ · cos θ ₁ = mλ ₁ and _{2n 1 · d 1 · cosθ 1} = (m + 1/2) both lambda ₁ of not satisfied, the thickness of the transparent substrate included in the second optical element _{d 2,} a refractive index and _{n 2} 2n ₂ · d ₂ · cos θ ₂ = mλ ₂ and 2n ₂ · d ₂ · cos θ , where θ _{2 is} the incident angle of light incident on the second optical element, λ ₂ is the wavelength , and m is an integer. _{2 = (m + 1/2} ) none of the lambda ₂ is not satisfied, the current supplied to the surface emitting laser, Serial relationship with the light amount of the first and the light beam emitted from each second optical element is an optical scanning device having linearity.

  According to this, it is possible to stably and accurately perform optical scanning without causing an increase in size and cost.

  According to a second aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the present invention that scans the at least one image carrier with a light beam modulated according to image information. And an image forming apparatus.

  According to this, since the optical scanning device of the present invention is provided, as a result, it is possible to stably form a high-quality image without causing an increase in size and cost.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. It is a figure for demonstrating the two-dimensional array contained in the light source in FIG. It is a figure for demonstrating a light quantity adjustment optical system. FIG. 5A and FIG. 5B are diagrams for explaining the driving mechanism. It is a figure for demonstrating an optical path when the base board 121A is moved to + W direction. It is a figure for demonstrating the optical path when the base board 121A is moved to -W direction. It is a figure for demonstrating an optical path when the base board 121B is moved to + W direction. It is a figure for demonstrating an optical path when the base board 121B is moved to -W direction. FIG. 10A and FIG. 10B are diagrams for explaining shading, respectively. It is a figure for demonstrating the dispersion | variation range of the light utilization efficiency between several optical scanning devices. It is a figure for demonstrating multiple reflection. It is a block diagram for demonstrating the structure of a scanning control apparatus. It is FIG. (1) for demonstrating the movement of the ND filter 120c. FIG. 10 is a diagram (No. 2) for explaining the movement of the ND filter 120c; It is a figure for demonstrating the modification 1 of a light quantity adjustment optical system. It is a figure for demonstrating the modification 2 of a light quantity adjustment optical system. 1 is a diagram illustrating a schematic configuration of a color printer.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a laser printer 1000 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a charge eliminating unit 1034, a cleaning unit 1035, a toner cartridge 1036, a paper feeding roller 1037, a paper feeding tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, a communication control device 1050, a printer control device 1060 that comprehensively controls the above-described units, and the like are provided. These are housed in predetermined positions in the printer housing 1044.

  The communication control device 1050 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 rotates in the direction of the arrow in FIG.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning unit 1035 are each disposed in the vicinity of the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning unit 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 irradiates the surface of the photosensitive drum 1030 charged by the charging charger 1031 with a light beam modulated based on image information from the host device. As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 1030. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  Incidentally, a scanning area in the main scanning direction in which image information is written on the photosensitive drum 1030 is called an “effective scanning area” or an “image forming area”.

  The toner cartridge 1036 stores toner, and the toner is supplied to the developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038, and the paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning unit 1035 removes the toner remaining on the surface of the photosensitive drum 1030 (residual toner). The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position facing the charging charger 1031 again.

  Next, the configuration of the optical scanning device 1010 will be described.

  As shown in FIG. 2 as an example, the optical scanning device 1010 includes a deflector-side scanning lens 11a, an image plane-side scanning lens 11b, a polygon mirror 13, a light source 14, a coupling lens 15, an aperture plate 16, and a cylindrical lens 17. Two light detection sensors (18a, 18b), two light detection mirrors (19a, 19b), a light amount adjusting optical system 120, a scanning control device 22 (not shown in FIG. 2, see FIG. 13), and the like. Yes. These are assembled at predetermined positions of the optical housing 21.

  In this specification, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of the photosensitive drum 1030 is defined as the Y-axis direction, and the direction along the optical axis of each scanning lens (11a, 11b) is defined as the X-axis direction. explain.

  In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The direction along the optical axis of the coupling lens 15 is defined as “W direction”, and the main scanning corresponding direction in the light source 14 is defined as “M direction”. Note that the sub-scanning corresponding direction in the light source 14 is the same direction as the Z-axis direction.

  As shown in FIG. 3 as an example, the light source 14 has a two-dimensional array 100 in which 40 light emitting units arranged two-dimensionally are formed on one substrate.

  The 40 light emitting units are arranged at regular intervals when all the light emitting units are orthogonally projected onto a virtual line extending in the Z-axis direction. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  Each light emitting unit is a vertical cavity surface emitting laser (VCSEL) having an oscillation wavelength of 780 nm band. That is, the two-dimensional array 100 is a so-called surface emitting laser array.

  Returning to FIG. 2, the coupling lens 15 converts the light beam emitted from the light source 14 into substantially parallel light.

  The aperture plate 16 has an aperture and shapes the light beam that has passed through the coupling lens 15.

  The light amount adjusting optical system 120 is disposed on the optical path of the light beam that has passed through the opening of the aperture plate 16. As shown in FIG. 4 as an example, the light amount adjusting optical system 120 includes four ND filters (120a, 120b, 120c, and 120d). Here, the four ND filters are the same ND filter.

  Each ND filter has a transparent substrate, and a surface (incident surface) on which the light beam is incident on the transparent substrate is coated with a chromium (Cr) film as an example in order to reduce the light transmittance. In addition, it is not limited to a chromium film | membrane, For example, you may coat | cover with the Inconel film | membrane. Further, instead of the metal film, it may be covered with a dielectric film. In short, a film having a uniform film thickness and excellent adhesion to the base (transparent substrate) may be formed so that a desired light transmittance can be stably obtained regardless of the incident position of the light beam.

  Here, the light transmittance of each ND filter is set so that the light transmittance of the entire light amount adjusting optical system 120 is 0.55.

  In addition, an antireflection film is coated on the surface (exit surface) from which the light flux is emitted from the transparent substrate of each ND filter.

  Further, the entrance surface and the exit surface of each ND filter are not parallel to each other.

  The ND filter 120a and the ND filter 120b are arranged so that the incident surface of the ND filter 120a and the emission surface of the ND filter 120b are parallel to each other. Further, the ND filter 120c and the ND filter 120d are arranged such that the incident surface of the ND filter 120c and the emission surface of the ND filter 120d are parallel to each other.

  The ND filter 120a is disposed on the optical path of the light beam that has passed through the opening of the aperture plate 16, changes the amount of incident light to a different amount, and emits transmitted light in a direction different from the incident direction of incident light.

  The ND filter 120b is disposed on the optical path of the light beam that has passed through the ND filter 120a, changes the amount of incident light to a different amount, and emits transmitted light in a direction different from the incident direction of the incident light. The light beam emitted from the ND filter 120b is parallel to the light beam incident on the ND filter 120a.

  The ND filter 120c is disposed on the optical path of the light beam that has passed through the ND filter 120d, changes the amount of incident light to a different amount, and emits transmitted light in a direction different from the incident direction of the incident light.

  The ND filter 120d is disposed on the optical path of the light beam that has passed through the ND filter 120c, changes the amount of incident light to a different amount, and emits transmitted light in a direction different from the incident direction of the incident light. The light beam emitted from the ND filter 120d is on the extension of the optical path of the light beam incident on the ND filter 120a. The light beam emitted from the ND filter 120d is the light beam emitted from the light amount adjusting optical system 120.

  The position of each ND filter in the W direction at this time is hereinafter referred to as “reference position” for convenience.

  Here, as an example, as shown in FIG. 5A, the ND filter 120a and the ND filter 120c are fixed on the support plate 130 in a predetermined positional relationship. The ND filter 120b is fixed at a predetermined position on the base plate 121A. The ND filter 120d is fixed at a predetermined position on the base plate 121B.

  Long holes 123 extending in the W direction are formed in the vicinity of both ends in the M direction of each base plate.

  As shown in FIG. 5B, which is a cross-sectional view taken along the line AA of FIG. 5A, the support plate 130 has a plurality of guide protrusions 131, and these protrusions 131 correspond to the base plates. Is inserted into the long hole 123. Further, the support plate 130 is formed with a screw hole substantially at the center of the line connecting the two adjacent protrusions 131. Then, the screw 126 is screwed into the screw hole through the long hole 123 of each base plate.

  In this case, when the screw 126 is loosened, each base plate can be moved (slid) in the W direction with respect to the support plate 130.

  For example, when the base plate 121A is moved in the + W direction and the ND filter 120b is moved in the + W direction with respect to the reference position, the optical path of the light beam emitted from the light amount adjustment optical system 120 is as shown in FIG. , Shift to + M side. As a result, the effective scanning area on the photosensitive drum 1030 is shifted to the −Y side (see FIG. 2). Therefore, for example, when the effective scanning area on the photosensitive drum 1030 is shifted to the + Y side from the desired position, the effective scanning area on the photosensitive drum 1030 is desired by moving the base plate 121A in the + W direction. It can be shifted to the position.

  Further, when the base plate 121A is moved in the −W direction and the ND filter 120b is moved in the −W direction with respect to the reference position, the light flux emitted from the light amount adjusting optical system 120 is shown in FIG. The optical path is shifted to the -M side. As a result, the effective scanning area on the photosensitive drum 1030 is shifted to the + Y side. Therefore, for example, when the effective scanning area on the photosensitive drum 1030 is shifted to the −Y side from the desired position, the effective scanning area on the photosensitive drum 1030 is moved by moving the base plate 121A in the −W direction. Can be shifted to a desired position.

  When the base plate 121B is moved in the + W direction and the ND filter 120d is moved in the + W direction with respect to the reference position, the optical path of the light beam emitted from the light amount adjusting optical system 120 is as shown in FIG. , Shift to -M side. As a result, the effective scanning area on the photosensitive drum 1030 is shifted to the + Y side. Therefore, for example, when the effective scanning area on the photosensitive drum 1030 is shifted to the −Y side from the desired position, the effective scanning area on the photosensitive drum 1030 is moved by moving the base plate 121B in the + W direction. It can be shifted to a desired position.

  Further, when the base plate 121B is moved in the -W direction and the ND filter 120d is moved in the -W direction with respect to the reference position, as shown in FIG. The optical path is shifted to the + M side. As a result, the effective scanning area on the photosensitive drum 1030 is shifted to the −Y side. Therefore, for example, when the effective scanning area on the photosensitive drum 1030 is shifted to the + Y side from the desired position, the effective scanning area on the photosensitive drum 1030 is moved by moving the base plate 121B in the −W direction. It can be shifted to a desired position.

  Whether the base plate 121A or the base plate 121B is moved when shifting the optical path of the light beam emitted from the light amount adjusting optical system 120 can be selected from the ease of work.

  By the way, the surface emitting laser has a narrower light amount (light output) range of the emitted light beam than the edge emitting laser diode (LD). On the other hand, the light source mounted in the optical scanning device is required to have a wide light output range of a certain degree or more for the following three reasons (reason A, reason B, reason C).

1. Reason A
The light beam emitted from the light source reaches the photosensitive drum via the pre-deflector optical system, the polygon mirror, and the scanning optical system. The optical elements constituting these optical systems are mass-produced products, and have some variation in light transmittance and reflectance. For this reason, it is conceivable that the ratio of the light amount of the light beam emitted from the light source and the light amount of the light beam that has reached the photosensitive drum, that is, the light use efficiency differs for each optical scanning device. Therefore, when the same amount of light is desired on the surface of the photosensitive drum in a plurality of image forming apparatuses, it is necessary to adjust the amount of light emitted from the light source in each optical scanning device.

2. Reason B
Variations in shading due to variations in polygon mirrors and scanning optical systems among a plurality of optical scanning devices are also conceivable. Shading means that the amount of light on the surface of the photosensitive drum varies depending on the position in the main scanning direction (image height position). In order to correct this shading, (1) the amount of light near the position of the image height 0 on the surface of the photosensitive drum (hereinafter also referred to as “center light amount”) is changed to the amount of light at other image height positions (hereinafter referred to as “peripheral”). (Refer to FIG. 10A), the peripheral light amount is lowered, and (2) when the central light amount on the surface of the photosensitive drum is larger than the peripheral light amount (see FIG. 10B). Work is being done to increase the amount of light in the periphery. In order to perform such shading correction, it is necessary to adjust the light amount of the light beam emitted from the light source in order to increase or decrease the peripheral light amount.

  If the variation in light utilization efficiency at the position of the image height of the photosensitive drum between the plurality of optical scanning devices is added to the variation in shading among the plurality of optical scanning devices, the light output range of the light source is expanded. Required (see FIG. 11).

3. Reason C
It is conceivable that the amount of light required on the surface of the photosensitive drum changes due to deterioration of the photosensitive characteristics of the photosensitive drum due to long-term use or changes in the environmental temperature. The light source must cope with such temporal changes.

  When the light source does not have a light output range that can cope with the above three reasons, an ND filter can be used as one of the methods for reducing the variation in light utilization efficiency among a plurality of optical scanning devices. Conceivable.

  For example, when the average value of the light use efficiency in a plurality of light scanning devices is 1.00, an ND filter having a light transmittance of 1 / 1.05 is used for the light scanning device having a light use efficiency of 1.05. By providing an ND filter having a light transmittance of 1 / 1.03 for an optical scanning device having a light utilization efficiency of 1.03, variation in light utilization efficiency among a plurality of light scanning devices can be reduced. Is possible.

  By the way, a glass or plastic flat plate is usually used for the substrate of the ND filter. For example, if an ND filter whose substrate is a flat plate is disposed between a coupling lens and a cylindrical lens, and the light beam emitted from the coupling lens is parallel light, the light beam incident on the ND filter is subjected to multiple reflections within the substrate. And cause multiple interference.

  As shown in FIG. 12, when light having a wavelength λ with an incident angle θ is incident on a transparent plate having a thickness d and a refractive index n, n · (BC + CD) −BE = 2n · d · cos θ using an integer m. = Mλ is satisfied, the transmitted light is strengthened. When n · (BC + CD) −BE = 2n · d · cos θ = (m + 1/2) λ is satisfied, the transmitted light is weakened.

  In addition, the surface emitting laser changes in wavelength within a range of less than 1 nm as the magnitude of the supplied current increases. In the ND filter, when the wavelength of the incident light beam changes, the phase between the plurality of lights emitted from the ND filter changes, and the degree of strengthening and weakening of the multiple reflected light changes. Therefore, the relationship between the current supplied to the surface emitting laser and the amount of light emitted from the ND filter does not have linearity.

  In the light amount adjustment optical system 120 according to the present embodiment, the incident surface and the exit surface of each ND filter are non-parallel to each other, so that multiple interference inside the ND filter can be reduced. Therefore, the relationship between the current supplied to the surface emitting laser and the amount of light emitted from the ND filter has linearity.

  Returning to FIG. 2, the cylindrical lens 17 has a strong power in the Z-axis direction, and forms an image of the light beam through the light amount adjusting optical system 120 in the vicinity of the deflection reflection surface of the polygon mirror 13 in the sub-scanning corresponding direction. Further, the cylindrical lens 17 forms a surface tilt correction system in the sub-scanning corresponding direction in cooperation with each scanning lens.

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system. In the present embodiment, the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, a light amount adjusting optical system 120, and a cylindrical lens 17.

  The polygon mirror 13 has a four-sided mirror, and each mirror serves as a deflection reflection surface. The polygon mirror 13 rotates at a constant speed around an axis parallel to the Z-axis direction, and deflects the light beam from the cylindrical lens 17.

  The deflector-side scanning lens 11 a is disposed on the optical path of the light beam deflected by the polygon mirror 13.

  The image plane side scanning lens 11b is disposed on the optical path of the light beam via the deflector side scanning lens 11a.

  The light beam that has passed through the image plane side scanning lens 11b is condensed on the surface of the photosensitive drum 1030, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 13 rotates. That is, the photoconductor drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”. The rotation direction of the photosensitive drum 1030 is the “sub-scanning direction”.

  The optical system arranged on the optical path between the polygon mirror 13 and the photosensitive drum 1030 is also called a scanning optical system. In the present embodiment, the scanning optical system includes a deflector side scanning lens 11a and an image plane side scanning lens 11b. Note that at least one folding mirror is disposed on at least one of the optical path between the deflector side scanning lens 11a and the image plane side scanning lens 11b and the optical path between the image plane side scanning lens 11b and the photosensitive drum 1030. May be.

  A part of the light beam before the start of writing in one scan out of the light beam that is deflected by the polygon mirror 13 and passes through the scanning optical system enters the light detection sensor 18a via the light detection mirror 19a. Further, a part of the light beam after completion of writing in one scan out of the light beam that is deflected by the polygon mirror 13 and passes through the scanning optical system enters the light detection sensor 18b through the light detection mirror 19b.

  Each of the light detection sensors outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  As shown in FIG. 13 as an example, the scanning control device 22 includes a pixel clock generation circuit 215, an image processing circuit 216, a writing control circuit 219, a light source driving circuit 221 and the like. Note that the arrows in FIG. 13 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.

  The pixel clock generation circuit 215 obtains the time required for the light beam to scan between the light detection sensors from the output signal of the light detection sensor 18a and the output signal of the light detection sensor 18b, and is set in advance to that time. The frequency is set so that a certain number of pulses can be accommodated, and the pixel clock signal PCLK having the frequency is generated. The pixel clock signal PCLK generated here is supplied to the image processing circuit 216 and the writing control circuit 219. The output signal of the light detection sensor 18a is output to the write control circuit 219 as a synchronization signal.

  The image processing circuit 216 rasterizes the image information received from the host device via the printer control device 1060, performs a predetermined halftone process, and the like, and then performs gradation of each pixel with the pixel clock signal PCLK as a reference. Is generated for each light emitting unit. The image processing circuit 216 outputs image data to the writing control circuit 219 in synchronization with the pixel clock signal PCLK when detecting the start of scanning based on the output signal of the light detection sensor 18a.

  The writing control circuit 219 generates a pulse modulation signal based on the image data from the image processing circuit 216, the pixel clock signal PCLK from the pixel clock generation circuit 215, and the synchronization signal.

  The light source driving circuit 221 drives each light emitting unit of the two-dimensional array 100 based on the pulse modulation signal from the writing control circuit 219.

  As is clear from the above description, in the optical scanning device 1010 according to the present embodiment, the ND filter 120a forms the first optical element, the ND filter 120b forms the second optical element, and the ND filter 120c. The third optical element is configured, and the fourth optical element is configured by the ND filter 120d.

  Each base plate and the support plate 130 constitute an adjustment mechanism.

  As described above, according to the optical scanning device 1010 according to the present embodiment, the light source 14 including the surface emitting laser array, the coupling lens 15 that couples the light flux from the light source 14, and the coupling lens 15. A light amount adjusting optical system 120 disposed on the optical path of the light beam, a cylindrical lens 17 that forms an image of the light beam passing through the light amount adjusting optical system 120 in the vicinity of the deflection reflection surface of the polygon mirror 13 in the Z-axis direction, and a cylindrical lens. The polygon mirror 13 that deflects the light beam from 17 and the scanning optical system that condenses the light beam deflected by the polygon mirror 13 on the surface of the photosensitive drum 1030 are provided.

  The light quantity adjusting optical system 120 includes four ND filters (120a, 120b, 120c, and 120d) in which the entrance surface and the exit surface are not parallel to each other. Each ND filter emits transmitted light in a direction different from the incident direction of incident light. In this case, the multiple interference inside each ND filter can be reduced, and the relationship between the current supplied to the light source 14 and the amount of light emitted from the light amount adjusting optical system 120 has linearity. It becomes. That is, the desired light utilization efficiency can be stably maintained.

  The light beam emitted from the ND filter 120b is parallel to the light beam incident on the ND filter 120a. In this case, it is not necessary to change the layout of each optical element in the optical housing 21 for the light amount adjusting optical system 120.

  Therefore, stable and highly accurate optical scanning can be performed without causing an increase in size and cost.

  Further, the light beam emitted from the ND filter 120d is on an extension of the optical path of the light beam incident on the ND filter 120a. In this case, the light amount adjusting optical system 120 can be easily applied to a conventional optical scanning device.

  Moreover, since the exit surface of each ND filter is covered with an antireflection film, multiple reflections can be further suppressed.

  Further, the ND filter b can be moved in the W direction with respect to the ND filter 120a. Thereby, the emission position of the light beam in the light amount adjustment optical system 120 can be adjusted in the main scanning correspondence direction. Therefore, the light spot position on the photosensitive drum 1030 can be adjusted in the main scanning direction.

  Further, the ND filter d can be moved in the W direction with respect to the ND filter 120c. Thereby, the emission position of the light beam in the light amount adjustment optical system 120 can be adjusted in the main scanning correspondence direction. Therefore, the light spot position on the photosensitive drum 1030 can be adjusted in the main scanning direction.

  Moreover, since each ND filter of the light quantity adjustment optical system 120 is the same member, an increase in the number of components can be suppressed, and component management can be simplified. Moreover, the workability of the assembly work can be improved.

  Since the laser printer 1000 according to the present embodiment includes the optical scanning device 1010, it is possible to stably form a high-quality image without causing an increase in size and cost.

  In the above embodiment, when the return light from the light amount adjustment optical system 120 may adversely affect the light source 14, the incident direction of the light beam incident on the light amount adjustment optical system 120 is the incident surface of the ND filter 120a. The light amount adjustment optical system 120 may be arranged so as to be inclined with respect to the normal direction.

  In the above embodiment, the case where all of the four optical elements of the light amount adjustment optical system 120 are ND filters has been described. However, the present invention is not limited to this, and at least one optical element is an ND filter. Other optical elements may be optical elements (for example, prisms) that hardly change the amount of light. In short, it is sufficient that the light amount adjusting optical system 120 has a desired light transmittance as a whole.

  Moreover, although the said embodiment demonstrated the case where all the emission surfaces in each ND filter of the light quantity adjustment optical system 120 were coat | covered with the antireflection film, it is not limited to this.

  Moreover, although the said embodiment demonstrated the case where each ND filter of the light quantity adjustment optical system 120 was the same shape, it is not limited to this.

  Moreover, the shape of each ND filter in the said embodiment is an example, and is not limited to this.

  In the above embodiment, the case where the ND filter b and the ND filter d can move in either the + W direction or the −W direction with respect to the reference position has been described. However, it may be movable only in the + W direction or only in the −W direction.

  For example, when the ND filter b and the ND filter d are movable only in the + W direction with respect to the reference position, the ND filter is used when shifting the optical path of the light beam emitted from the light amount adjusting optical system 120 to the + M side. b is moved, and the ND filter d is moved when shifting the optical path of the light beam emitted from the light amount adjusting optical system 120 to the −M side.

  Further, for example, when the ND filter b and the ND filter d are movable only in the −W direction with respect to the reference position, the optical path of the light beam emitted from the light amount adjustment optical system 120 is shifted to the + M side. The ND filter b is moved when the ND filter d is moved and the optical path of the light beam emitted from the light amount adjusting optical system 120 is shifted to the −M side.

  In the above embodiment, the ND filter a may be movable instead of the ND filter b.

  In the above embodiment, the ND filter c may be movable instead of the ND filter d (see FIGS. 14 and 15). In this case, the light emission position in the light amount adjusting optical system 120 can be shifted without changing the size of the light amount adjusting optical system 120 (the distance between the ND filter a and the ND filter d).

  In the above embodiment, only one of the ND filter b and the ND filter d may be movable. When only the ND filter b is movable, the light flux in the light amount adjusting optical system 120 is not changed without changing the size of the light amount adjusting optical system 120 (the distance between the ND filter a and the ND filter d). The injection position can be shifted.

  Further, when it is not necessary to shift the emission position of the light beam in the light amount adjustment optical system 120, both the ND filter b and the ND filter d may be fixed on the support plate 130. That is, there is no need for each base plate.

  Further, for example, when a mechanism for adjusting the light spot position on the photosensitive drum 1030 with respect to the main scanning direction is separately provided, the light amount adjustment is performed on the extension line of the optical path of the light beam incident on the light amount adjustment optical system 120. When it is not necessary to emit a light beam from the optical system 120, the ND filter c and the ND filter d may be omitted as shown in FIG. In this case, the light quantity adjustment optical system 120 can be reduced.

  In the above embodiment, as shown in FIG. 17 as an example, an ND filter e in which the ND filter b and the ND filter c are integrated may be used instead of the ND filter b and the ND filter c. In this case, the light quantity adjustment optical system 120 can be reduced.

  Moreover, although the said embodiment demonstrated the case where the two-dimensional array 100 had 40 light emission parts, it is not limited to this.

  Moreover, although the said embodiment demonstrated the case where the light source 14 had the two-dimensional array 100, it is not limited to this. For example, instead of the two-dimensional array 100, the light source 14 may have a one-dimensional array in which a plurality of light emitting units are arranged in a line. Further, the light source 14 may have one light emitting unit instead of the two-dimensional array 100.

  In the above embodiment, the laser printer 1000 is described as the image forming apparatus. However, the present invention is not limited to this. An image forming apparatus other than a printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated may be used. In short, any image forming apparatus including the optical scanning device 1010 may be used.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  Further, for example, as shown in FIG. 18, a color printer 2000 including a plurality of photosensitive drums may be used.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow). The black “photosensitive drum K1, charging device K2, "Developing device K4, cleaning unit K5, and transfer device K6", cyan "photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6", and magenta "photosensitive drum" M1, charging device M2, developing device M4, cleaning unit M5, and transfer device M6 ”,“ photosensitive drum Y1, charging device Y2, developing device Y4, cleaning unit Y5, and transfer device Y6 ”for yellow, and light A scanning device 2010, a transfer belt 2080, a fixing unit 2030, and the like are provided.

  Each photoconductor drum rotates in the direction of the arrow in FIG. 18, and a charging device, a developing device, a transfer device, and a cleaning unit are arranged around each photoconductor drum along the rotation direction.

  Each charging device uniformly charges the surface of the corresponding photosensitive drum. The surface of each photosensitive drum charged by the charging device is optically scanned by the optical scanning device 2010, and a latent image is formed on each photosensitive drum.

  Then, a toner image is formed on the surface of each photosensitive drum by a corresponding developing device. Further, the toner image of each color is sequentially transferred onto the recording paper on the transfer belt 2080 by the corresponding transfer device, and finally the image is fixed on the recording paper by the fixing unit 2030.

  The optical scanning device 2010 has a light amount adjustment optical system similar to the light amount adjustment optical system 120 for each color. Therefore, the same effect as the optical scanning device 1010 can be obtained.

  The color printer 2000 can obtain the same effects as the laser printer 1000.

  Note that in a tandem multicolor printer, color misregistration of each color may occur due to machine accuracy or the like. However, the accuracy of correcting color misregistration of each color can be increased by selecting a light emitting unit to be lit.

  Further, in this color printer 2000, an optical scanning device may be provided for each color, or may be provided for every two colors.

  As described above, the optical scanning device of the present invention is suitable for performing stable and highly accurate optical scanning without causing an increase in size and cost. The image forming apparatus according to the present invention is suitable for stably forming a high-quality image without causing an increase in size and cost.

  DESCRIPTION OF SYMBOLS 11a ... Deflector side scanning lens, 11b ... Image side scanning lens, 13 ... Polygon mirror, 14 ... Light source, 15 ... Coupling lens (coupling optical system), 17 ... Cylindrical lens, 100 ... Two-dimensional array (surface emission) Laser array), 120... Light quantity adjustment optical system, 120 a... ND filter (first optical element), 120 b... ND filter (second optical element), 120 c... ND filter (third optical element), 120 d. Filter (fourth optical element), 1000 ... laser printer (image forming apparatus), 1010 ... optical scanning apparatus, 1030 ... photosensitive drum (image carrier), 2000 ... color printer (image forming apparatus), 2010 ... optical scanning Apparatus, K1, C1, M1, Y1... Photosensitive drum (image carrier).

Japanese Patent No. 3227226 JP 2008-33062 A JP 05-160467 A JP 2002-174785 A

Claims (11)

An optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam,
A light source including a vertical cavity surface emitting laser;
A coupling optical system for coupling a light beam from the light source;
Arranged on the optical path of the light flux through the coupling optical system,
A direction that is different from the incident direction of incident light, including a transparent substrate having a non-parallel incident surface and an emission surface, and a film on which at least one of the incident surface and the emission surface is formed to reduce light transmittance. A first optical element for emitting transmitted light to
The incident light and the emission surface are not parallel to each other so that the transmitted light emitted from the first optical element is incident and the transmitted light is emitted in the same direction as the incident direction of the incident light incident on the first optical element. And a second optical element that emits transmitted light in a direction different from the incident direction of the incident light, and changes the amount of incident light to a different amount and emits the light. comprising a; system and
The thickness of the transparent substrate included in the first optical element is d ₁ , the refractive index is n ₁ , the incident angle of light incident on the first optical element is θ ₁ , the wavelength is λ ₁ , m Is an integer,
Neither 2n ₁ · d ₁ · cos θ ₁ = mλ ₁ and 2n ₁ · d ₁ · cos θ ₁ = (m + 1/2) λ ₁ are satisfied,
The thickness of the transparent substrate included in the second optical element is d ₂ , the refractive index is n ₂ , the incident angle of light incident on the second optical element is θ ₂ , the wavelength is λ ₂ , m Is an integer,
Neither 2n ₂ · d ₂ · cos θ ₂ = mλ ₂ nor 2n ₂ · d ₂ · cos θ ₂ = (m + 1/2) λ ₂ are satisfied,
An optical scanning device in which a relationship between a current supplied to the surface emitting laser and a light amount of a light beam emitted from each of the first and second optical elements has linearity .   The optical scanning device according to claim 1, wherein an incident surface of the first optical element and an emission surface of the second optical element are parallel to each other.   The optical scanning apparatus according to claim 1, further comprising an adjustment mechanism for adjusting an interval between the first optical element and the second optical element.   The optical scanning device according to claim 1, wherein the film is a metal film.   5. The optical scanning device according to claim 1, wherein at least one of the incident surface and the reflection surface of the first and second optical elements is coated with an antireflection film. .   The optical scanning device according to claim 1, wherein the first and second optical elements have the same shape. The light amount adjusting optical system is:
A third optical element disposed on the optical path of the light beam transmitted through the second optical element and emitting the transmitted light in a direction different from the incident direction of the incident light; and the light beam transmitted through the third optical element. 7. The optical device according to claim 1, further comprising a fourth optical element disposed on the optical path and emitting transmitted light on an extension of the optical path of the incident light in the first optical element. The optical scanning device described.   8. The optical scanning device according to claim 7, wherein the third and fourth optical elements have the same shape. The light amount adjusting optical system is:
An optical path of a light beam disposed on the optical path between the first optical element and the second optical element, and emitted from the second optical element, is an optical path of incident light in the first optical element. 7. The apparatus according to claim 1, further comprising a third optical element that changes an optical path of a light beam emitted from the first optical element so as to be located on an extension line. 8. Optical scanning device. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to any one of claims 1 to 9 configured to scan the at least one image carrier with a light beam modulated according to image information.   The image forming apparatus according to claim 10, wherein the image information is multicolor image information.

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