JP4992154B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device provided in an electrophotographic image forming apparatus, and an image of a laser printer, a laser plotter, a digital copying machine, a plain paper facsimile, or a composite machine of these equipped with the optical scanning device. The present invention relates to a forming apparatus.

  In electrophotographic image forming apparatuses used in laser printers, laser plotters, digital copying machines, plain paper facsimiles, or multi-function machines of these types, in recent years, colorization and high speed have been advanced, and photoconductors that are image carriers. An image forming apparatus compatible with a tandem method having a plurality of (usually four) is widely used. In this tandem image forming apparatus, for example, four photoconductors are arranged side by side along a transfer belt (or intermediate transfer belt) that conveys a recording material, and each photoconductor is charged by a charging unit and then written by a writing unit. A latent image is formed on each photoconductor, and the latent image on each photoconductor is developed and visualized with developers of different colors (for example, yellow, magenta, cyan, and black toners) of the developing means. The color images are transferred onto a recording material (or an intermediate transfer belt) conveyed by a transfer belt so as to form a color image.

  The electrophotographic color image forming apparatus has only one photoconductor, rotates the photoconductor by the number of colors, and sequentially superimposes and transfers the image onto the intermediate transfer member. There is also a so-called one-drum-intermediate transfer method in which the image is formed and transferred onto the recording material in a lump. In this case, if there are four colors and one drum, the photoconductor is formed every time one image is formed. Must be rotated four times, and productivity is inferior compared to the tandem method.

As described above, the tandem image forming apparatus can increase the speed and improve the productivity of color image formation as compared with the one-drum-intermediate transfer system. However, in the case of the tandem image forming apparatus, optical scanning is possible. In order to perform optical writing on a plurality of photoconductors by a writing unit using the apparatus, the number of light sources of the optical scanning device inevitably increases (for example, when there are four photoconductors, four light sources are usually required). As a result, problems such as an increase in the number of components, a color shift due to a wavelength difference between a plurality of light sources, and an increase in cost occur.
Further, deterioration of the semiconductor laser is cited as a cause of the failure of the writing unit. For this reason, as the number of light sources increases, the probability of failure increases.

Therefore, there is an example in which the optical scanning device used in the tandem image forming apparatus is devised so as not to increase the number of light sources.
For example, in the invention described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-284822), as means for scanning a surface to be scanned with different beams from a common light source, polygon mirrors stacked in two stages at different phases should be used. However, the polygon mirror whose phase is shifted is not a general-purpose product, and there is a concern about cost increase. In addition, the workability of the polygon mirror is also required, and the surface tilt of each step is different and the surface accuracy is different.

  Further, in the invention described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-060168), a scanning surface with different incident beams is scanned by a single-stage polygon mirror so that the cost can be further reduced. The problem of polygon mirror processability was also cleared, but in this method, since the beam power from a common light source is divided so that it is about half, the actual efficiency of the light source power is lost, and multiple light sources Compared to the method using, power more than double is required. However, the increase in power leads to deterioration of the laser light source and causes a failure of the writing unit.

JP 2006-284822 A JP 2007-060168 A

  The present invention has been made in view of the above circumstances, and can reduce the number of light sources, reduce the beam power, enable high-speed image output, and achieve low-cost, high-quality optical scanning. An object of the present invention is to provide an image forming apparatus, and further to provide an image forming apparatus having high image quality and corresponding to multiple colors provided with the optical scanning device.

In order to achieve the above object, the present invention employs the following solutions.
According to a first aspect of the present invention, there is provided an optical scanning apparatus including a light source to be modulated and driven, a deflection unit having a multi-surface reflection surface, and a scanning optical system for guiding a beam deflected and scanned by the deflection unit to a surface to be scanned. ,
An optical path switching unit is provided between the light source and the deflecting unit, and the optical path switching unit can switch between a first optical path and a second optical path, and an incident optical path of the first optical path to the deflecting unit wherein it is second and the incident light path of the optical path has an opening angle of approximately [pi / 2, and has a reflecting surface of the deflection means 4 side, the beam and the second passing through the first optical path The beam passing through the optical path is guided to different scanning surfaces .

According to a second means of the present invention, in the optical scanning device of the first means, an incident mirror is provided on each of the first optical path and the second optical path between the optical path switching means and the deflecting means, The optical path from the incident mirror of the first optical path to the deflecting means and the optical path from the incident mirror of the second optical path to the deflecting means have an opening angle of approximately π / 2 .
According to a third means of the present invention, in the optical scanning device of the first or second means, the optical path switching means comprises a diffractive optical element and an electric field applying means capable of applying an electric field to the diffractive optical element. It is characterized by becoming.
According to a fourth means of the present invention, in the optical scanning device of the third means, the diffractive optical element constituting the optical path switching means has a period of a region made of non-polymerizable liquid crystal and a region made of an isotropic medium. The refractive index with respect to a specific polarization direction of the region composed of the non-polymerizable liquid crystal is changed by applying an electric field, and the light having the specific polarization direction is transmitted or diffracted according to the applied electric field. To do.
Further, according to a fifth means of the present invention, in the optical scanning device of the third or fourth means, the diffractive optical element constituting the optical path switching means is mainly composed of a region made of a polymer and mainly a non-polymerizable liquid crystal. It is a polymer dispersion type liquid crystal hologram element in which a periodic phase separation structure with a region is formed.

According to a sixth means of the present invention, there is provided an optical scanning apparatus comprising: a light source that is modulated and driven; a deflecting unit having a multi-surface reflecting surface; and a scanning optical system that guides a beam scanned by the deflecting unit to a surface to be scanned.
Between the light source and the deflecting means, there is provided an optical path switching means comprising a polarization switching means capable of switching the polarization direction, and a polarization separation means for separating polarized light components orthogonal to each other . And an incident optical path of the first optical path to the deflecting means and an incident optical path of the second optical path have an opening angle of approximately π / 2, The deflecting means has four reflecting surfaces, and the beam passing through the first optical path and the beam passing through the second optical path are guided to different scanning surfaces .

According to a seventh means of the present invention, in the optical scanning device of the sixth means, an incident mirror is provided on each of the first optical path and the second optical path between the optical path switching means and the deflecting means, The optical path from the incident mirror of the first optical path to the deflecting means and the optical path from the incident mirror of the second optical path to the deflecting means have an opening angle of approximately π / 2.
According to an eighth means of the present invention, in the optical scanning device of the sixth or seventh means, the polarization separation means comprises a diffractive optical element, and the diffractive optical element includes a region exhibiting optical anisotropy, an optical element, and the like. It has a periodic structure composed of regions exhibiting anisotropy, and is characterized by separating polarized light components orthogonal to each other by transmission and diffraction.
According to a ninth means of the present invention, in the optical scanning device of the eighth means, the polarization switching means comprises a pair of transparent substrates, an alignment film provided on the inner surface side of the substrate, and the alignment film. A liquid crystal layer composed of a chiral smectic C phase having homogeneous orientation and an electric field applying means for applying an electric field in a direction substantially perpendicular to the transparent substrate surface, and rotating a specific polarization direction by about 90 ° according to the electric field strength. It is characterized by doing.

According to a tenth means of the present invention, in the optical scanning device of any one of the first to ninth means, a temperature adjusting means is provided.
According to an eleventh means of the present invention, in the optical scanning device of any one of the first to tenth means, a synchronization detecting means is arranged on the opposite side of the scanning optical system with the incident beam as a boundary. And
Further, the twelfth means of the present invention is a pitch adjusting means for adjusting a sub-scanning direction pitch of a plurality of scanning lines formed on the surface to be scanned in the optical scanning device of any one of the first to eleventh means. Is arranged between the optical path switching means and the deflection means.

According to a thirteenth means of the present invention, in the optical scanning device according to any one of the first to twelfth means, the optical scanning device has a plurality of light sources, and the plurality of light sources are arranged at different positions in the sub-scanning direction. It is characterized by.
According to a fourteenth aspect of the present invention, in the optical scanning device according to any one of the first to thirteenth means, when a common light source scans different scanned surfaces, each scanned surface is scanned. It is characterized in that different light amounts are set.
Further, the fifteenth means of the present invention is characterized in that, in the optical scanning device of any one of the first to fourteenth means, a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting LASER)) is used as the light source. .

According to a sixteenth aspect of the present invention, there is provided an image forming apparatus including a writing unit that forms a latent image by irradiating a beam from a light source onto an image carrier that is a surface to be scanned. An optical scanning device according to any one of the fifteenth means is provided.
According to a seventeenth aspect of the present invention, in the image forming apparatus according to the sixteenth aspect , the image forming apparatus includes a plurality of image carriers, and the latent images formed on the plurality of image carriers by the writing unit are developed in different colors. Developing with a developer to form a visible image, and forming a multicolor or full-color image by transferring the visible images of each color formed on the plurality of image carriers onto a recording material directly or via an intermediate transfer member. Features.

In the optical scanning device of the first means, an active optical path switching means is provided between the light source and the deflecting means, and the beam can be switched and used in a time division manner by this active optical path switching means. Compared with the beam splitting method, the beam power from the light source can be efficiently used for optical scanning.
In the optical scanning device of the second means, an incident mirror is provided on each of the first optical path and the second optical path between the optical path switching means and the deflecting means, and from the incident mirror of the first optical path. Since the optical path to the deflecting means and the optical path from the incident mirror of the second optical path to the deflecting means have an opening angle of approximately π / 2, the beam power from the light source can be efficiently used as in the first means. It can often be used for optical scanning.
In the optical scanning device of the third means, in addition to the configuration and effect of the first or second means, the optical path can be switched by electric field control by using a diffractive optical element and an electric field applying means as the optical path switching means. Become.
In the optical scanning device of the fourth means, in addition to the configuration and effect of the third means, a diffractive optical element having a periodic structure of a region made of non-polymerizable liquid crystal and a region made of an isotropic medium is used. The presence or absence of the refractive index difference of the periodic structure can be easily realized by controlling the electric field, and the refractive index difference of the periodic structure can be increased.
In the optical scanning device of the fifth means, in addition to the configuration and effects of the third or fourth means, the liquid crystal hologram element produced by interference exposure can be duplicated, so that the cost can be reduced. Moreover, it has excellent responsiveness to electric field driving.

Since the optical scanning device of the sixth means includes the polarization separation means and the polarization switching means as the optical path switching means, the polarization direction can be controlled by the polarization switching means and the optical path can be switched by the polarization separation means. Further, the switching of the active optical path can efficiently use the beam power from the light source for optical scanning as compared with the conventional beam splitting method.
In the optical scanning device of the seventh means, an incident mirror is provided on each of the first optical path and the second optical path between the optical path switching means and the deflecting means, and from the incident mirror of the first optical path. Since the optical path to the deflecting means and the optical path from the incident mirror of the second optical path to the deflecting means have an opening angle of approximately π / 2, the beam power from the light source is efficiently obtained as in the sixth means. It can often be used for optical scanning.
In the optical scanning device of the eighth means, in addition to the configuration and effect of the sixth or seventh means, a diffractive optical element is used as the polarization separation means, and therefore the influence of variations in mirror surface accuracy due to conventional mirror division is affected. In addition, there is no problem of beam spot diameter degradation due to the influence of the arrangement error, and the cost can be reduced as compared with an expensive half mirror prism.
In the optical scanning device of the ninth means, in addition to the configuration and effect of the eighth means, a ferroelectric liquid crystal element comprising a chiral smectic C phase and an electric field applying means are used as the polarization switching means. By setting the film thickness and orientation direction of the liquid crystal layer corresponding to the polarization direction, switching of the polarization direction can be easily realized by electric field control. In addition, the ferroelectric liquid crystal has an effect that the response is excellent.

In the optical scanning device of the tenth means, in addition to the configuration and effect of any one of the first to ninth means, a temperature adjusting means is provided, so that the light whose switching path response or polarization switching response is stable. A scanning device can be provided.
In the optical scanning device of the eleventh means, in addition to the configuration and effect of any one of the first to tenth means, a layout detection freedom is provided by arranging a synchronous detection means on the opposite side of the scanning optical system with the incident beam as a boundary. The degree is improved.
In the optical scanning device of the twelfth means, in addition to the configuration and effect of any one of the first to eleventh means, a sub-scanning direction pitch adjusting means for a plurality of scanning lines is arranged between the light beam dividing means and the deflecting means. Thus, the scanning line interval in the sub-scanning direction on the surface to be scanned can be accurately corrected.

In the optical scanning device of the thirteenth means, in addition to the configuration and effect of any one of the first to twelfth means, a plurality of light sources are arranged at different positions in the subscanning direction, so that the light fluxes differing in the subscanning direction Can be time-divided with a single optical path switching means, and cost reduction can be achieved.
In the optical scanning device of the fourteenth means, in addition to the configuration and effect of any one of the first to thirteenth means, the light quantity can be adjusted by adjusting the light quantity, and the high quality with excellent color reproducibility. It is possible to output a simple image.
In the optical scanning device of the fifteenth means, in addition to the configuration and effect of any one of the first to fourteenth means, a high-speed optical scanning device can be realized by using a surface emitting laser.

In the image forming apparatus of the sixteenth means, the writing unit is provided with the optical scanning device of any one of the first to fifteen means, so that image formation capable of reducing cost while maintaining high speed and high quality is achieved. An apparatus can be provided.
In the image forming apparatus of the seventeenth means, in addition to the configuration and effects of the sixteenth means, a plurality of the image carriers are provided, and the latent images formed on the plurality of image carriers by the writing unit are developed in different colors. By developing with an agent to develop a visible image, each color developed image formed on the plurality of image carriers is superimposed on a recording material directly or via an intermediate transfer member and transferred to form a multicolor or full color image. Therefore, it is possible to provide a color image forming apparatus capable of reducing costs while maintaining high speed and high quality.

Hereinafter, the configuration, operation, and effects of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an optical scanning device showing an embodiment of the present invention. In the figure, reference numerals 1 and 1 'are semiconductor lasers (LD) as light sources, 2, 2' are incident mirrors, 3 and 3 'are coupling lenses, 4 is an optical path switching means, 5 (5c, 5d) and 5'. (5a, 5b) are two-stage cylindrical lenses, 6 is a soundproof glass, 7 is a deflector as a deflecting means (for example, a polygon mirror having four deflecting reflecting surfaces (reflecting mirrors)), 8 (8a, 8b) Is a first scanning lens, 9 is an optical path folding mirror, 10 (10a, 10b) is a second scanning lens, 11 (11a, 11b) is a photosensitive member as a surface to be scanned, and 12 is an aperture stop (aperture). Show.

  The two divergent light beams emitted from the semiconductor lasers 1 and 1 ′ are converted into weak convergent light beams, parallel light beams, or weak divergent light beams by the coupling lenses 3 and 3 ′. The beams exiting the coupling lenses 3 and 3 ′ pass through the aperture stop 12 for stabilizing the beam diameter on the scanned surface and enter the optical path switching means 4. The beams from the common light source incident on the optical path switching means 4 are each time-divided in two directions. In this case, since the arrangement of the light sources 1 and 1 'differs only in the sub-scanning direction, the optical path switching means 4 can be used in common, and two beams that are different in the sub-scanning direction can be switched in time division to two optical paths. it can. The configuration of the optical path switching unit 4 will be described in detail below.

[First Embodiment]
Embodiments corresponding to the first to fifth means of the present invention will be described with reference to FIGS.
FIG. 2 shows a part of the optical scanning device. This optical scanning device includes a laser light source 1, a coupling lens 3, an optical path switching unit 4, incident mirrors 2 and 2 ', and a deflecting unit (for example, a polygon mirror) 7 having a multi-surface reflecting mirror. In FIG. 2, an aperture stop (aperture), a cylindrical lens, an image forming optical system for a surface to be scanned, and the like are omitted.
As will be described in detail later, the optical path switching means 4 includes a diffractive optical element 50 having an electric field applying means as shown in FIG. 3, and passes through different optical paths when the electric field application is ON and when the electric field application is OFF.

  Here, the operation of the optical scanning device will be described. The beam emitted from the laser light source 1 is incident on the polygon mirror 7 in a state in which the beam optical path is changed in the main scanning direction by the electric field application control in the optical path switching means 4 and the incident angle is different by 90 ° in a time division manner. . Here, in the electric field application control, the optical path 1 is passed when the electric field application is ON, and the optical path 2 is passed when the electric field application is OFF, but the optical path 2 is passed when the electric field application is ON and the optical path 1 is passed when the electric field application is OFF. Also good. The polygon mirror 7 has a configuration using four deflecting reflecting surfaces (reflecting mirrors).

  In such a configuration, by controlling the application of the electric field in the optical path switching means 4, switching between the optical path 1 and the optical path 2 can be realized in a time-sharing manner. When scanning the (scanned surface), the beam passes substantially only through the optical path 1 and hardly passes through the optical path 2. When the optical path 2 is selected and the beam to the polygon mirror 7 is incident at an angle different by 90 ° (relative to the optical path 1) and scans the photosensitive member surface (scanned surface), the beam is only in the optical path 2 only. An operation that passes through the optical path 1 and hardly passes through the optical path 1 can be realized. That is, there is no loss of the amount of beam from the light source, and the light source power can be used efficiently. As a result, the life of the light source is extended and the establishment of deterioration is reduced. In particular, when a surface emitting laser (VCSEL) effective for increasing the density is used as a light source, the effect is increased.

Here, the optical path switching means 4 will be specifically described. FIG. 4 shows an outline of the diffractive optical element 50 constituting the optical path switching means 4.
In this diffractive optical element 50, a grating shape 53 is formed on one side of a pair of substrates 51, 52 facing each other with a predetermined gap by a support member 54, and a liquid crystal material 55 is sealed between the gratings, A periodic structure of a region made of non-polymerizable liquid crystal and a region made of an isotropic medium is formed. Here, the formation of the periodic structure is realized by forming a lattice shape 53 on one substrate 51 by photolithography and etching or cutting or molding technique, and filling a non-polymerizable liquid crystal material 55 between the lattices. it can.

  Regarding the configuration of the diffractive optical element, general liquid crystal types such as nematic, cholesteric, and smectic can be used as non-polymerizable liquid crystals, and transparent resins such as photopolymers, quartz, blue plates, An optical glass material such as a white plate or BK7 can be used, but is not limited to this as long as it does not have birefringence. Although not shown, an electrode capable of applying an electric field that regulates the alignment direction of the liquid crystal is provided at the time of manufacturing, and alignment processing such as alignment film, rubbing, and photo alignment is performed in order to efficiently use the birefringence of the liquid crystal. Is preferred.

Here, FIGS. 5 and 6 show functional operations of the diffractive optical element 50 constituting the optical path switching means 4.
FIG. 5 shows an arrangement in which alignment processing is performed so as to be substantially perpendicular to the substrate surface, and light of s-polarized light (perpendicular to the paper surface) is incident thereon.
As shown in FIG. 5A, when the electric field application is OFF and the ordinary light component refractive index no of the liquid crystal and the refractive index n of the isotropic medium match, the light travels straight without being influenced by the grating, When the electric field application is turned on in FIG. 5B, if the refractive index ne of the extraordinary light component of the liquid crystal does not match the refractive index n of the isotropic medium, the light is diffracted by the influence of the grating.

In FIG. 6, the alignment treatment is performed so as to be substantially horizontal alignment (in the ridge line direction of the lattice) with respect to the substrate surface, and s-polarized light (perpendicular to the paper surface) is incident.
If the extraordinary light component refractive index ne of the liquid crystal and the refractive index n of the isotropic medium do not match when the electric field application is turned off as shown in FIG. 6A, the light is diffracted by the influence of the grating, and the same If the normal light component refractive index no of the liquid crystal coincides with the refractive index n of the isotropic medium when the electric field application is ON in FIG. 5B, the light travels straight without being affected by the grating.

  As described above, the diffractive optical element 50 having the above-described configuration exhibits transmission or diffraction operation by controlling electric field application. By using the diffractive optical element 50 having such an operation, the optical path can be switched. 5 and 6, the incident polarized light is s-polarized light, but the orientation direction of the liquid crystal is substantially horizontal with respect to the substrate surface as shown in FIG. 7A and is substantially perpendicular to the ridge line direction of the lattice. Thus, the same operation can be realized for p-polarized light.

  Although a detailed description of the diffraction function is omitted, it is preferable that the diffraction efficiency of the −1st order light or the + 1st order light is approximately 100%. A type diffraction grating is preferred. In order to increase the efficiency of the one-sided diffracted light, it is preferable to tilt the grating so as to satisfy the Bragg diffraction condition. For the adjustment of the inclination of the grating, the grating shape 53 may be inclined as shown in FIG. 7B, or the diffractive optical element itself may be inclined as shown in FIGS.

Here, the production and operation check of the diffractive optical element 50 constituting the optical path switching means 4 will be described.
A SiON film is formed on a BK7 substrate having a thickness of about 0.5 mm, and a lattice shape having a pitch of about 1 μm and a height of about 2.5 μm is formed by photolithography and etching. As shown in FIG. A nematic liquid crystal 55 (Merck ZLI-2248) was held between the substrates 52. At this time, an alignment film was formed only on the flat substrate 52 by spin coating. The distance between the substrates was set to about 6 μm by a pair of support members (for example, aluminum electrode spacers) 54, and the aluminum electrodes were arranged so that an electric field could be applied in the lattice ridge line direction. When a voltage of electric field strength of 4.5 V / μm (100 Hz) was applied to the diffractive optical element and blue LD light was incident, 70% of the first-order light was obtained in an arrangement in which the element (grating) was inclined by 12 °. A high diffraction efficiency was obtained. When the electric field application was turned off in this state, a transmittance of 70% was obtained with zero-order light. At this time, the polarization direction was set to the lattice ridge line direction (s-polarized light), and the operation shown in FIG. 5 was confirmed.

  Here, a polymer dispersion type liquid crystal hologram element will be described as an example of a volume phase type diffraction grating forming the optical path switching means 4. An outline of a cross-sectional configuration of the liquid crystal hologram element before the interference exposure is shown in FIG. A composition obtained by uniformly mixing non-polymerizable liquid crystal molecules, a polymerizable monomer or prepolymer, and a photopolymerization initiator (not shown) is sandwiched between two transparent substrates on which transparent electrodes (not shown) are formed. The thickness of the composition can be controlled by a spacer member (not shown) that controls the distance between the substrates. Since this composition has photosensitivity, it is handled in an environment in which light in a wavelength region having sensitivity is blocked in the device manufacturing process.

  Regarding the configuration of the liquid crystal hologram element, as the spacer member, a spherical spacer, a fiber spacer, a PET film, a mylar film, or the like used in a liquid crystal display device can be used. Further, a protrusion shape (including an uneven shape) may be processed on the surface of the substrate by photolithography and etching or a molding technique. The spacer member may exist in the hologram region, but it is preferable to form it outside the effective region of the hologram in consideration of the influence of light scattering and the like. The height of the spacer member can be used in the range of several μm to several tens of μm, and is appropriately set so as to have a desired hologram layer thickness according to the wavelength of the diffracted light and the refractive index difference between the polymer part and the liquid crystal part. As the transparent substrate, a glass, a plastic substrate, or the like used in a liquid crystal display device can be used.

Regarding the composition, as the non-polymerizable liquid crystal, a general liquid crystal having refractive index anisotropy can be used. When selecting a liquid crystal material, it is possible to select a liquid crystal material having a refractive index substantially equal to the refractive index of the cured layer of the polymerizable monomer or prepolymer in an orientation state of a certain order parameter. Then, the polymerizable monomer or the prepolymer may be selected so that the refractive index of the liquid crystal is almost equal to the refractive index in an orientation state with a certain order parameter.
As the polymerizable monomer or prepolymer, it is preferable to use one having a large cure shrinkage due to polymerization. In addition to the above, a thermal polymerization inhibitor, a plasticizer, and the like may be added.

  As the photopolymerization initiator, a known material can be used, and the addition amount depends on the absorbance of each material with respect to the wavelength of light to be irradiated, but is 0.1% by weight or more based on the total amount of the monomer or prepolymer. % By weight or less is good, and more preferably 0.5% by weight or more and 3% by weight or less. Although a detailed description of the addition amount of the photopolymerization initiator is omitted, if the addition amount is too small, phase separation between the polymer and the liquid crystal hardly occurs, and the necessary exposure time becomes long. On the other hand, when there are too many photopolymerization initiators, the polymer and the liquid crystal are cured with insufficient phase separation, so that many liquid crystal molecules are taken into the polymer, resulting in poor polarization selectivity. There is. Similarly, the mixing ratio of the non-polymerizable liquid crystal material and the polymerizable monomer or prepolymer also greatly affects the phase separation. If the mixing ratio of the non-polymerized liquid crystal is too small, sufficient birefringence (refractive index modulation amount) Is not obtained, and when the amount is too large, many liquid crystal molecules are taken into the polymer, resulting in poor polarization selectivity. In addition, the liquid crystal molecules in the polymer become droplets and cause scattering components, so that the overall transmittance decreases. As a mixing ratio, the ratio of the non-polymerizable liquid crystal material is preferably 10% by weight to 30% by weight with respect to 100% by weight of the total amount of the polymerizable monomer or prepolymer. Furthermore, the ratio of 20% by weight to 25% by weight is the best. At this ratio, the obtained birefringence and the scattering component by the liquid crystal are well balanced, resulting in high transmittance.

  Here, a hologram forming process by phase separation will be described with reference to FIG. When the composition is exposed using two-beam interference exposure with a laser light source having a desired wavelength (not shown), the photopolymerization reaction of the polymerizable monomer or prepolymer starts in the bright part of the interference fringes. At this time, curing shrinkage occurs, resulting in a density difference, the adjacent polymerizable monomer or prepolymer moves to the bright part, and further polymerization proceeds. At the same time, phase separation occurs when the non-polymerizable liquid crystal present in the bright part is driven out toward the dark part. At this time, it is considered that when the liquid crystal molecules move, a force to align the major axis of the liquid crystal molecules in the moving direction by the interaction with the monomer or polymer chain is considered to work. That is, it is considered that a force for orienting liquid crystal molecules in the direction of the interference fringe acts in the phase separation process. Finally, as shown in the lower diagram of FIG. 11, the periodic structure of the polymer layer and the non-polymerizable liquid crystal layer is formed corresponding to the bright and dark pitch of the interference fringes, and the orientation vector of the liquid crystal layer portion is the distance direction of the interference fringes. It is thought that the state which turned to is obtained. In this interference exposure and phase separation process, the sample is preferably heated and held at an appropriate temperature. It is considered that the phase separation speed changes depending on the temperature and affects the orientation of the liquid crystal molecules. The optimum heating temperature depends on the material used, but is generally about 40 ° C to 100 ° C.

  Strictly speaking, it is difficult for the periodic structure of the polymer layer and the non-polymerizable liquid crystal layer by phase separation to completely separate the polymer and the non-polymerizable liquid crystal periodically, and the polymer layer here has many polymer components. The region may contain liquid crystal molecules. The non-polymerizable liquid crystal layer is a region having a large amount of non-polymerizable liquid crystal components and may contain a polymer component. In actuality, the interface between the polymer layer and the liquid crystal layer is assumed to be uneven rather than an ideal plane. Therefore, the variation in the major axis direction of the liquid crystal molecules at the interface is large as shown in FIG. The parameter is a little small.

The pitch of the periodic structure to be produced varies depending on the desired diffraction angle and wavelength, but is generally in the range of 0.2 μm to 10 μm. For example, in order to obtain a diffraction angle of 40 ° with respect to incident light having a wavelength of 650 nm, a pitch of about 1.0 μm is required, and for incident light with a wavelength of 780 nm, a pitch of about 1.2 μm is required. The inclination angle of the interface between the polymer layer and the liquid crystal layer is preferably about 0 ° to ± 20 ° with the direction perpendicular to the substrate surface being 0 °. As the amount of exposure depends on the temperature during addition concentration and exposure of the photopolymerization initiator, the refractive index modulation is saturated stable state obtaining 0.5 J / cm ² from 30 J / cm ² C., more stable In order to obtain productivity, 1 J / cm ² to 15 J / cm ² is preferable.

Since the liquid crystal hologram element produced by such interference exposure can be duplicated in an original, cost reduction can be realized. In addition, due to the alignment restriction due to the polymer, it is superior in response to electric field driving as compared with a diffractive optical element in which a lattice shape is filled with liquid crystal.
Here, production and operation confirmation of the liquid crystal hologram element constituting the optical path switching means 4 will be described.

  An antireflection film for blue light and red light was formed on one surface of a 0.7 mm thick glass substrate, and an ITO (Indium Tin Oxide) electrode was formed on the surface opposite to the antireflection film. The glass substrates were bonded to each other with respective adhesives mixed with beads spacers having a diameter of approximately 8 μm so that the electrode surfaces face each other. The adhesive was applied to two locations on the edge of the substrate on the surface opposite to the antireflection film forming surface.

Next, a composition comprising a mixture of the following materials (1) to (5) was injected into the cell by the capillary method while being heated to about 65 ° C. to form a composition layer having a thickness of about 8 μm. In addition, since this composition was reactive to light having a shorter wavelength than green, it was handled in a dark room using red light.
(1) Nematic liquid crystal (TL216 manufactured by Merck, Δε> 0): 25 parts by weight (2) Phenylglycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer (AH600 manufactured by Kyoeisha Chemical Co., Ltd.): 75 parts by weight (3) dimethylol tricyclodecandi Acrylate (DCP-A manufactured by Kyoeisha Chemical Co., Ltd.): 10 parts by weight (4) 2-hydroxyethyl methacrylate (HO manufactured by Kyoeisha Chemical Co., Ltd.): 5 parts by weight (5) Bisacylphosphine oxide photopolymerization initiator (Irgacure 819 manufactured by Ciba-Geigy) 1 part by weight After injecting into the cell a composition comprising a mixture of the above materials (1) to (5), this composition was isotropic at room temperature.

Next, a two-beam interference exposure system using a He—Cd laser having a wavelength of 442 nm and an output of 80 mW was prepared. The laser beam was divided and expanded, so that one light beam was parallel light of about 10 mW / cm ² , and the crossing angle of the two light beams was set to 28 degrees. At this wavelength and crossing angle, interference fringes with a period of about 1 μm are generated in the crossing region of the two light beams. With the cell substrate attached to a heating device and heated to about 65 ° C., two-beam interference exposure was performed for about 1 minute to produce a liquid crystal hologram element. At this time, the two light beams were set to enter from directions of +7 degrees and +35 degrees with respect to the direction perpendicular to the substrate surface.

  For evaluating the characteristics of the liquid crystal hologram element, the manufactured element was irradiated with linearly polarized laser light having a wavelength of 633 nm, and the 0th-order light and the + 1st-order diffracted light intensity with respect to the incident light intensity were measured. The incident light intensity is adjusted using an ND filter so that the incident light intensity is about 5 mW, a linearly polarizing plate and a half-wave plate are arranged in the incident light path, and the optical axis of the half-wave plate is rotated 45 degrees to enter the element. The polarization direction (p-polarized light, s-polarized light) can be switched. At this time, the p-polarized light was in a direction orthogonal to the interference fringes at the time of interference exposure, and the s-polarized light was in the direction of the interference fringes. When the incident polarization direction was set to p-polarized light, a high diffraction efficiency of 80% was obtained with + 1st order light (0th order light had a transmittance of 8%). Here, when the incident polarization direction is fixed to p-polarized light and a voltage with an electric field strength of 40 V / μm (100 Hz) is applied between the substrates, the diffraction efficiency of the + 1st order light is substantially 0%, and 88% for the 0th order light. % High transmittance was obtained. When the response speed at this time was measured with a high-speed camera, the response time was about 100 μsec when the electric field application was turned on and about 250 μsec when the electric field application was turned off. That is, by using the liquid crystal hologram element as the diffractive optical element 50 shown in FIG. 3, the optical path can be switched by controlling the electric field application.

[Second Embodiment]
Next, embodiments corresponding to the sixth to eighth means of the present invention will be described with reference to FIGS.
FIG. 12 shows a part of the optical scanning device. This optical scanning device includes a laser light source 1, a coupling lens 3, a polarization switching unit 13, a polarization separation unit 14, incident mirrors 2 and 2 ', and a deflection unit (for example, a polygon mirror) 7 having a multi-surface reflecting mirror. As a beam path switching unit for the beam from the common light source 1, the polarization switching unit 13 and the polarization separation unit 14 are combined.
In FIG. 12, an aperture stop (aperture), a cylindrical lens, an imaging optical system for a surface to be scanned, and the like are omitted.

Here, the polarization separating means 14 includes a PBS prism and a diffractive optical element. However, since the PBS prism is expensive, a configuration in which the diffractive optical element 60 is combined as shown in FIG. 13 is more advantageous for cost reduction. It is.
In FIG. 13, the diffractive optical element 60 having a function of transmitting s-polarized light and diffracting p-polarized light is used as a polarization separation element, but has a function of separating polarized light components orthogonal to each other by transmission and diffraction. If so, no problem.

Here, the production and operation confirmation of the polarization separating means combined with the diffractive optical element will be described.
An antireflection film for blue light and red light was formed on one surface of a 0.7 mm thick glass substrate, and the two glass substrates were bonded together with respective adhesives mixed with bead spacers each having a diameter of about 8 μm. The adhesive was applied to two locations on the edge of the substrate on the surface opposite to the antireflection film forming surface.

Next, a composition comprising a mixture of the following materials (1) to (5) was injected into the cell by the capillary method while being heated to about 65 ° C. to form a composition layer having a thickness of about 8 μm. In addition, since this composition was reactive to light having a shorter wavelength than green, it was handled in a dark room using red light.
(1) Nematic liquid crystal (TL216 manufactured by Merck, Δε> 0): 25 parts by weight (2) Phenylglycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer (AH600 manufactured by Kyoeisha Chemical Co., Ltd.): 75 parts by weight (3) dimethylol tricyclodecandi Acrylate (DCP-A manufactured by Kyoeisha Chemical Co., Ltd.): 10 parts by weight (4) 2-hydroxyethyl methacrylate (HO manufactured by Kyoeisha Chemical Co., Ltd.): 5 parts by weight (5) Bisacylphosphine oxide photopolymerization initiator (Irgacure 819 manufactured by Ciba-Geigy) 1 part by weight After injecting into the cell a composition comprising a mixture of the above materials (1) to (5), this composition was isotropic at room temperature.

Next, a two-beam interference exposure system using a He—Cd laser having a wavelength of 442 nm and an output of 80 mW was prepared. The laser beam was divided and expanded, so that one light beam was parallel light of about 10 mW / cm ² , and the crossing angle of the two light beams was set to 28 degrees. At this wavelength and crossing angle, interference fringes with a period of about 1 μm are generated in the crossing region of the two light beams. With the cell substrate attached to a heating device and heated to about 65 ° C., two-beam interference exposure was performed for about 1 minute to produce a liquid crystal hologram element. At this time, the two light beams were set to enter from directions of +7 degrees and +35 degrees with respect to the direction perpendicular to the substrate surface.

  For evaluating the characteristics of the liquid crystal hologram element, the manufactured element was irradiated with linearly polarized laser light having a wavelength of 633 nm, and the 0th-order light and the + 1st-order diffracted light intensity with respect to the incident light intensity were measured. The incident light intensity is adjusted using an ND filter so that the incident light intensity is about 5 mW, a linearly polarizing plate and a half-wave plate are arranged in the incident light path, and the optical axis of the half-wave plate is rotated 45 degrees to enter the element. The polarization direction (p-polarized light, s-polarized light) can be switched. At this time, the p-polarized light was in a direction orthogonal to the interference fringes at the time of interference exposure, and the s-polarized light was in the direction of the interference fringes. When p-polarized light is incident, a high diffraction efficiency of 89% is obtained for the + 1st-order light (0th-order light is 9% transmittance), and when s-polarized light is incident, a high 98% transmittance is obtained for the 0th-order light ( A diffraction efficiency of 0% was obtained for the + 1st order light.

  Here, using the above liquid crystal hologram element, a polarization separation element was produced as shown in FIG. When the p-polarized light and the s-polarized light were respectively incident and the light utilization efficiency with respect to the polarization direction was measured, the light utilization efficiency when the p-polarized light was incident was 78%, and the light utilization efficiency when the s-polarized light was incident was 94%. Could be separated.

  Further, the polarization switching unit 13 can be realized by a configuration in which an electric field applying unit is provided on a material having a property of changing a refractive index when an electric field is applied. For example, there is a configuration composed of a ferroelectric crystal such as LN, a liquid crystal element, etc., but the former has a limit in miniaturization and high density because it cuts out the crystal substrate and processes the device, and is very expensive. The latter is widely used for display applications and is inexpensive, but a twisted nematic liquid crystal generally used as a liquid crystal element has a response speed of several tens of milliseconds and is not suitable for a high-speed response. Therefore, a polarization switching element using a ferroelectric liquid crystal that is relatively inexpensive and exhibits high-speed response is preferable.

  Here, as the operation of the optical scanning device of FIG. 12, the polarization direction of the beam emitted from the laser light source 1 is switched by the electric field control in the polarization switching means 13 and is orthogonalized by the polarization separation means 14. Each beam in the polarization direction is polarized in the main scanning direction by a time division of the beam optical path, and is incident on the polygon mirror 7 with a phase difference of 90 °. The polygon mirror 7 has a configuration using four deflecting reflecting surfaces (reflecting mirrors).

  In such a configuration, by controlling the electric field in the polarization switching means 13, switching between the optical path 1 and the optical path 2 can be realized in a time-sharing manner. The beam is incident on the polygon mirror 7 by selecting the optical path 1 and the surface of the photoconductor (covered surface). When scanning the scanning plane), the beam passes only through the optical path 1 and hardly passes through the optical path 2. When the optical path 2 is selected and the beam to the polygon mirror 7 is incident at an angle different by 90 ° (relative to the optical path 1) and scans the photosensitive member surface (scanned surface), the beam is only in the optical path 2 only. Can pass through the optical path 1 and hardly pass through the optical path 1, and the light quantity from the light source can be used efficiently without loss. As a result, the life of the light source is extended and the establishment of deterioration is reduced. In particular, when a surface emitting laser (VCSEL) array (see FIG. 17) effective for increasing the density is used as a light source, the effect is increased.

Here, the polarization switching means 13 will be specifically described. FIG. 14 shows an outline of the polarization switching means 13 using the ferroelectric liquid crystal element 70.
The polarization switching means includes a pair of transparent substrates 71 and 72, an alignment film (not shown), a ferroelectric liquid crystal layer 75 composed of a chiral smectic C phase having homogeneous alignment, and a direction substantially perpendicular to the transparent substrate surface. The ferroelectric liquid crystal element 70 includes a pair of transparent electrodes 73 and 74 that can apply an electric field, and an electric field applying unit (not shown).

  As described above, it is preferable to use a ferroelectric liquid crystal composed of a homogeneously oriented chiral smectic C phase for a high-speed response, but a nematic liquid crystal can also be used in a similar configuration depending on the application that does not require a high-speed response. . In addition, as the alignment film, a normal alignment film such as polyimide used for TN liquid crystal, STN liquid crystal, or the like can be used. In order to strongly restrict the direction of the liquid crystal director, it is preferable to separately perform a rubbing process or a photo alignment process. ITO or the like can be used for the transparent electrode.

  FIG. 15 is a schematic diagram for explaining the switching operation of the ferroelectric liquid crystal element 60. In general, a ferroelectric liquid crystal layer composed of a chiral smectic C phase has a helical structure. However, when sandwiched between cell gaps d thinner than the helical pitch, the helical structure is unwound and a surface-stabilized ferroelectric liquid crystal layer (SSFLC). ) As shown in FIG. 15, the SSFLC has an orientation state in which the liquid crystal molecules are inclined and tilted with respect to the smectic layer normal by an inclination angle −θ (here, θ = 22.5 °), and tilted by θ in the opposite direction. A state in which a stable alignment state is mixed can be realized. In FIG. 15, W is the layer normal of the smectic phase, n is the long axis direction of the liquid crystal molecules (director), the small black circle (●) symbol in the white circle (◯), and the + symbol in the white circle (◯) are It represents the direction of spontaneous polarization. By applying an electric field in a direction perpendicular to the paper surface, the direction of liquid crystal molecules and their spontaneous polarization can be made uniform, and that state can be maintained. And switching between two states can be performed by switching the polarity of the electric field to apply. That is, when an electric field of −E is applied in FIG. 15, when an electric field of + E is applied to the orientation state 1 inclined by −θ from the layer normal direction W of the smectic phase, only θ from the layer normal direction W of the smectic phase is applied. The tilted orientation state 2 can be stabilized. That is, when θ = 22.5 °, the alignment state 2 tilted 45 ° from the alignment state 1 can be stabilized.

  FIG. 16 is a schematic diagram showing the operation of the polarization switching means using the SSFLC described above. In FIG. 16, the thickness (cell gap) d of the liquid crystal layer is determined by the wavelength λ of incident light (for example, 650 nm or 780 nm) and the refractive index anisotropy Δn at 650 nm or 780 nm of the liquid crystal material, and Δn × d = λ / 2 (Ie, so as to satisfy the half-wave plate condition).

  Here, the incident polarization direction needs to be adjusted and arranged so as to be positioned in the short axis direction or the long axis direction of the liquid crystal molecules in one of the two alignment states of the liquid crystal molecule alignment in the liquid crystal layer ( Here, the minor axis direction of the alignment state 1 when an -E electric field is applied). As an adjustment method, it is possible to adjust the polarization direction by arranging the phase plate. It is also possible to set the initial alignment of the liquid crystal molecules or to adjust the rotation of the liquid crystal element itself by an alignment process such as rubbing.

  With such a configuration, as shown in FIG. 16, when an −E electric field is applied between the transparent electrodes, the liquid crystal molecules are aligned in an orientation state (alignment state) tilted by −θ from the layer normal direction W of the smectic phase. 1), the incident polarized light is emitted while maintaining the polarization direction as it is. On the other hand, when a + E electric field is applied to the transparent electrode, the liquid crystal molecules take an alignment state (alignment state 2) inclined by + θ from the layer normal direction W of the smectic phase. In this case, since θ = 22.5 °, the liquid crystal molecule major axis direction (director) is tilted by 2θ = 45 ° with respect to the incident polarized light. As a result, the half-wave plate condition is satisfied, and the outgoing polarized light has a polarization direction rotated by approximately 90 ° from the incident polarized light. That is, polarization switching can be realized by electric field control, and a ferroelectric liquid crystal is used. Therefore, the response speed for polarization switching is a high-speed response of several tens to several hundreds of μsec.

Here, the production and operation check of the polarization switching means 13 using the ferroelectric liquid crystal element 70 will be described.
An ITO electrode (thickness: 1500 mm) was formed on a non-alkali glass substrate having a thickness of 1.1 mm. An alignment film (AL3046-R31 manufactured by JSR) was formed on the surface of the substrate electrode by spin coating to a thickness of about 800 mm, and the substrate surface was subjected to alignment treatment by rubbing. Two glass substrates as described above were used, and the electrodes were opposed to each other, and bonded together with an adhesive mixed with beads so that the distance between the substrates was about 2.5 μm. A ferroelectric liquid crystal (R5002, manufactured by Clariant, Δn = 0.17, 2θ = 90 degrees) is injected as a liquid crystal layer between the two substrates in a state where the substrate is heated to 90 degrees by a capillary method. A liquid crystal element 60 as shown in FIG. 14 was manufactured by cooling after cooling in a state where a DC voltage of 10 V / μm was applied. When the alignment state was observed with an optical microscope, a substantially uniform alignment state was confirmed. A rectangular wave signal having a frequency of 100 Hz and ± 10 V / μm was input to the liquid crystal element 60, and the switching speed between light and dark under crossed Nicols was measured (liquid crystal element characteristic evaluation apparatus, manufactured by Otsuka Electronics Co., Ltd.). FIG. 18 shows the response speed characteristics of the liquid crystal element. The response speed in the vicinity of room temperature (25 ° C.) is about 1 msec, which is one order of magnitude faster than a general liquid crystal element.

  Here, regarding the operation of switching polarization by electric field control, in order to efficiently realize polarization switching, it is preferable that the cone angle 2θ of the ferroelectric liquid crystal is 45 ° as shown in FIG. Using a ferroelectric liquid crystal (Clariant FELIX018-100, Δn = 0.17, 2θ = 45) at 45 °, a liquid crystal element was produced and evaluated in the same manner as described above. In the evaluation method, the produced liquid crystal element was placed between a λ / 2 plate and a polarizing plate, and the polarization direction at the time of incidence and the polarization direction at the time of emission were evaluated. A red LD (wavelength 650 nm) was used as a light source. First, the incident polarization direction was set so as to be inclined approximately 22.5 ° with respect to the rubbing direction on the λ / 2 plate. Next, when an electric field of +10 V / μm was applied between the device electrodes, it was slightly elliptically polarized, but the polarization directions at the time of incidence and at the time of emission were substantially the same. Furthermore, when an electric field of −10 V / μm having different polarities was applied between the device electrodes, this was also slightly elliptically polarized, but the polarization directions at the time of incidence and at the time of emission differed by approximately 90 degrees. That is, the polarization direction could be switched by 90 ° by controlling the electric field application. The outgoing polarized light becomes elliptically polarized light because the condition Δn × d = λ / 2 is not optimized.

[Third Embodiment]
Next, an embodiment corresponding to the tenth means of the present invention will be described.
In the optical scanning device of the first embodiment or the second embodiment described above, in order to enter the polygon mirror 7 with a 90 ° phase difference in a time division manner without losing the beam from the light source 1, respectively. The response speed of the optical path switching is important. As described above, the optical path is switched by controlling the electric field of the optical path switching means 4 (active diffractive optical element 40) or the polarization switching means 13 (polarization switching element 60 made of a ferroelectric liquid crystal element). Therefore, in order to realize an inexpensive element, the liquid crystal is used. The liquid crystal material generally exhibits temperature dependence, and has a property that the viscosity decreases and the response speed increases as the temperature increases (see FIG. 18). Therefore, it is preferable to provide temperature adjusting means for speeding up the optical path switching.

  As the temperature adjusting means, it is possible to provide a temperature adjusting element such as a Peltier element or a small heater directly on an active diffractive optical element or polarization switching element that affects the response of switching the optical path. In the case of such a configuration, since the temperature of the element is directly adjusted, there is an advantage that the time for reaching the adjustment temperature is quick and high-precision adjustment can be performed. Since a Peltier element is generally expensive, it is preferable to use a small heater. As the small heater, for example, a ceramic heater can be used.

There is also a configuration in which temperature adjusting means is provided in the optical scanning device so as to adjust the temperature in the optical scanning unit. FIG. 19 shows an outline of an optical scanning device provided with temperature adjusting means.
As shown in FIG. 19, a casing that covers optical parts (not shown) (light source, optical path switching means, polygon mirror, imaging optical system, etc.) is configured to adjust the temperature using a heater. For example, the heater can be composed of a heating source and a heat diffusion plate, and the atmosphere heated by the heating source is uniformly diffused by the heat diffusion plate. Also, the temperature in the apparatus can be adjusted by adjusting the amount of air blown by the fan. Moreover, it is preferable to provide a thyristor or a thermostat so as to be adjusted to a specific temperature range.

Here, for example, when a liquid crystal element having responsiveness as shown in FIG. 18 is used for optical path switching, a high-speed response of 0.5 msec or less can be maintained by setting the temperature range in the temperature adjusting means to 30 ° C. to 40 ° C. it can.
As a means for detecting the temperature, a thermistor, a thermocouple, or the like can be used, but it is preferable to use a thermocouple for the following reason. Thermistors have poor linearity of resistance temperature change characteristics and low measurement accuracy. Thermocouples have high thermoelectromotive force, small variation in characteristics, and are compatible. In addition, it has features such as being stable against heat and having a long life, and is highly reliable. As the material, for example, K (chromel-alumel), J (iron-constantan), T (copper-constantan), E (chromel-constantan), N (nycrosyl-nycyl) or JIS standard defined in the JIS standard. External (nickel-nickel 18% molybdenum), (tungsten 5% rhenium-tungsten 26% rhenium), or the like can be used.

[Fourth Embodiment]
Next, in the optical scanning device having the configuration shown in FIG. 1, the configuration of the optical system after the optical path switching means 4 will be described in more detail.
In FIG. 1, the beam emitted from the optical path switching means 4 is formed on the deflection reflection surface of a deflector (polygon mirror) 7 by cylindrical lenses 5 (5c, 5d), 5 '(5a, 5b) arranged on the upper and lower stages respectively. A line image that is long in the main scanning direction is converted in the vicinity.
In FIG. 1, of the light beams time-divided in two directions by the optical path switching means 4, incident light on one side incident on one side of the deflector 7 via the cylindrical lenses 5a and 5b and the incident mirror 2 ′ is shown. Only the scanning optical system (the first scanning lenses 8a and 8b, the optical path folding mirror 9 and the second scanning lenses 10a and 10b) that deflects by the deflector 7 and scans the two photoconductors 11a and 11b is illustrated. However, in actuality, a scanning optical system similar to the optical system shown in the figure is disposed with the deflector 7 interposed therebetween, and the other light beam divided by the optical path switching means 4 is also cylindrical. The light is incident on the other side of the deflector 7 via the lenses 5c and 5d and the incident mirror 2 and deflected, and two photosensitive members (not shown) are scanned via a scanning optical system (not shown) having the same configuration. .

  FIG. 20 is a diagram for explaining optical scanning with time-division light that is time-divided in two directions by the optical path switching means 4. As shown in FIG. 5A, when the beam emitted from the optical path switching means 4 passes through the upper optical path (that is, the incident light x in the figure) in a time division manner, the lower optical path (that is, in the figure). The incident light y) hardly passes, but the beam also passes through the slightly lower optical path. The reverse is also true, and when the beam passes through the lower optical path, the beam passes through the upper optical path. Therefore, when the beam from the upper optical path is scanning the scanning area on the photoreceptor, the beam from the lower optical path must not scan the scanning area on the photoreceptor. The reverse is also true.

  As shown in FIG. 20 (a), the incident light after passing through the optical path switching means from a common light source is incident on different surfaces of the deflector 7 and has a phase difference of 90 ° (in the figure). Incident light x, incident light y). If the phase difference is near 90 °, the divided light beams do not scan the effective scanning area at the same time. As an example, the lower reflected light when scanning the upper effective scanning region x shown in FIG. 20A (when the reflected light a is scanned into the reflected light b and reflected light c) will be described. .

  When the upper incident light x becomes the reflected light a, the lower reflected light does not enter the scanning region because the phase difference of the lower reflected light is 90 ° as shown in FIG. When the polarizer 7 rotates and the upper incident light becomes reflected light b, the lower reflected light becomes b ′ as shown in FIG. 20C and does not enter the scanning region. Further, when the polarizer 7 further rotates and the upper incident light becomes the reflected light c, the lower reflected light becomes c ′ as shown in FIG. 20D and does not enter the scanning region. That is, it can be seen that the reflected light on the lower side from FIG. 20B through FIG. 20C to FIG. 20D does not enter the scanning region. This is because the phase difference of the incident light is 90 ° and the number of surfaces of the polarizer 7 is four. Therefore, the above relationship is established when the phase difference of the reflected light is always 90 °. When the upper incident light (incident light x) scans within the effective scanning region, the lower incident light scans outside the effective scanning region, and the relationship of not scanning the photosensitive member surface is the phase difference. It is self-evident from the above relationship that this holds even if the angle is slightly deviated from 90 °. Conversely, when the lower incident light scans within the effective scanning area, the upper incident light scans outside the effective scanning area and does not scan the surface of the photosensitive member. It is self-explanatory.

  When the upper incident light is scanning the effective scanning area, the light source is modulated and driven based on the image information of the corresponding color (for example, magenta). Furthermore, when the incident light on the lower side scans the effective scanning area, the image of two colors is scanned with the common light source by performing modulation driving of the light source to the image information of the corresponding color (for example, black). It becomes possible to do.

  As shown in FIG. 21, the incident light x and the incident light y can be made incident on the same reflecting surface of the deflector 7. However, it is necessary to fold the light beam by the mirrors 2 and 2 'across the scanning region, and the layout property is improved. Becomes worse. Further, when the light beam is incident on the same reflecting surface of the deflector 7, the divided light beam needs to be incident on the deflector 7 at a different position in the sub-scanning direction. Must be changed. Therefore, as shown in FIG. 1, the layout is improved when the divided light beams are incident on different reflecting surfaces of the deflector 7.

FIG. 22 is a timing chart of exposure for a plurality of colors. In the figure, the vertical axis represents the amount of light and the horizontal axis represents time.
As described above, the beam from the common light source time-divided by the optical path switching means 4 is deflected and scanned by the deflector 7 to expose the two photoconductors 11a and 11b (for example, black and magenta photoconductors). The time chart in the case of performing the division and lighting all in the effective scanning region is shown in FIG. A solid line indicates a portion corresponding to black, and a dotted line indicates a portion corresponding to magenta. The timing of writing in black and magenta is determined by detecting the scanning beam with a synchronization detection means (synchronization detection sensor) arranged outside the effective scanning width. Although the synchronization detection means is not shown in FIG. 1, a synchronization detection sensor using a light receiving element such as a photodiode is usually used.

  FIG. 23 is a timing chart for varying the exposure amount depending on the color. In FIG. 22, the light amounts in the black and magenta regions are set to be the same. However, since the transmittance and reflectance of the optical element are actually different, if the light amount of the light source is the same, the photoconductor The amount of light reaching the beam will be different. Therefore, as shown in FIG. 23, when the different photoconductor surfaces are scanned, the light amounts set on the different photoconductor surfaces can be made equal by making the set light amounts different from each other.

By the way, since each beam emitted from the two light sources 1 and 1 ′ shown in FIG. 1 is exposed to two different photoconductors 11a and 11b, respectively, the two photoconductors 11a and 11b are each exposed once. In this scanning, two scanning lines are formed. At this time, it is necessary to adjust the pitch of the scanning lines in the sub-scanning direction according to the pixel density. As a method often used as a pitch adjustment method in the sub-scanning direction, the light source unit (the light sources 1, 1 ′, the coupling lenses 3, 3 ′, and the aperture stop 12 as one unit) is used as the main scanning direction and the sub-scanning. There is a method of rotating around an axis perpendicular to the direction. In this case, a certain photosensitive member can have a desired pitch. However, for the other photosensitive member, the optical element after the optical path switching means 4 is used. Pitch error occurs due to shape error, mounting error, etc.
In order to solve this problem, it is necessary to provide means for adjusting the pitch in the sub-scanning direction between the optical path switching means 4 and the deflection means (deflector) 7.

Here, FIG. 24 is a diagram showing an example of the pitch adjusting means. FIG. 4A is a diagram showing one-side adjustment means, and FIG. 4B is a diagram showing both-side adjustment means.
Here, as an example, a case will be described in which pitch adjusting means is provided in the optical element 5 (for example, the cylindrical lenses 5a, 5b, 5c, and 5d in FIG. 1) disposed between the optical path switching means 4 and the deflector 7.
The cylindrical lens 5 is attached to a housing (not shown) of the optical scanning device via an intermediate member 21a (or 21b, 21c). A curable resin (for example, a photocurable resin) is previously applied to each mounting surface. At this time, the intermediate member 21a (or 21b, 21c) can be “adjusted eccentrically about an axis parallel to the main scanning direction” and “adjusted in the optical axis direction” with respect to the housing, and the cylindrical lens 5 is connected to the intermediate member 21a. (Or 21b, 21c) can be adjusted “eccentric adjustment around an axis parallel to the optical axis” and “position adjustment in the sub-scanning direction”, and the intermediate member 21a (or 21b, 21c) can be adjusted with respect to the housing. At least one of the possible directions is different from at least one of the adjustable directions of the cylindrical lens 5 with respect to the intermediate member 21a (or 21b, 21c). By adopting such a configuration, a plurality of optical characteristics (thickening the beam waist diameter, reducing beam waist position deviation, and beam spot position deviation) can be secured simultaneously, and the cylindrical lens 5 is decentered around the optical axis. By making the adjustment possible, the scanning line interval in the sub-scanning direction can be set optimally. Further, the surface of the intermediate member 21a that is in contact with the cylindrical lens 5 and the surface that is in contact with the housing are flat and easy to adjust. When the adjustment is completed, the mutual position is fixed by curing the curable resin by a predetermined method (for example, ultraviolet irradiation).

FIG. 25 is a diagram for explaining an example of an actual adjustment method. FIG. 4A shows an example of one-side adjustment, and FIG. 4B shows an example of both-side adjustment.
The cylindrical lens 5 is held by a jig, and the cylindrical lens 5 is moved in the direction to be adjusted (here, the position in the optical axis direction, the eccentricity around the axis parallel to the optical axis, the position in the sub-scanning direction). Thereafter, the intermediate member 21a (or 21b, 21c) coated with a curable resin (for example, an ultraviolet curable resin) is pressed against the cylindrical lens 5 and the pedestal 22 of the housing, and the cylindrical lens 5 is fixed by irradiating ultraviolet rays. With such a configuration, adjustment in a plurality of directions can be easily performed with a simple structure. Here, by making the intermediate member 21a (or 21b, 21c) transparent, it becomes easier to fix with the ultraviolet curable resin.
Although it is possible to hold an optical element (such as the cylindrical lens 5) using one intermediate member 21a as shown in FIG. 24A, a plurality of intermediate members 21b and 21c are arranged on opposite sides of the light beam. By adopting such a configuration, for example, when the linear expansion coefficients of the housing and the intermediate member 21 (assuming resin) are different, even if the temperature rises, the optical axis Since stress is generated symmetrically with respect to the optical element, the posture change of the optical element is reduced.

Usually, a semiconductor laser used in an image forming apparatus performs automatic light quantity control (hereinafter referred to as APC) to stabilize light output. With APC, the optical output of a semiconductor laser is monitored by a light receiving element such as a photodiode (PD), and the forward current of the semiconductor laser is controlled to a desired value by a detection signal of the received light current proportional to the optical output of the semiconductor laser. It is a method.
When the semiconductor laser is an edge-emitting type semiconductor laser, the light receiving element often uses a photodiode that monitors light emitted in the direction opposite to the direction emitted toward the coupling lens. When a ghost light is incident, the amount of light detected by the light receiving element increases.

  For example, when the incident angle of the beam to the reflecting surface (reflecting mirror) of the deflector 7 is 0, the reflecting surface (reflecting mirror) faces the light source direction. When APC is performed at this position, the reflected beam Returns to the light source, and the amount of light detected by the light receiving element for monitoring increases. Therefore, it is set so that APC is not performed when the incident angle is zero. By adopting this configuration, it is possible to output an image with an appropriate density and with little density unevenness.

Next, as an example of the arrangement of the synchronization detection means, as shown on the lower side of FIG. 26, it is possible to detect the scanning light by placing a synchronization detection sensor such as a photodiode outside the effective scanning region on the side opposite to the light source. However, since there is incident light in the vicinity of the effective scanning area on the light source side, there is no room for installing a synchronous detection sensor. Therefore, as shown in the upper side of FIG. 26, the light source side synchronous detection uses reflected light on the light source side for the synchronous detection with the incident light as a boundary.
In place of the above method, the APC light receiving element may be used to perform synchronous detection using the light output of the light receiving element when the incident angle of the beam to the reflecting surface of the deflector 7 is zero. Is possible. This is because, when the incident angle is 0, the reflected light from the reflecting surface of the deflector 7 returns to the LD as it is, so that the light returned to the LD is also detected by the APC light receiving element, and this signal is used to detect synchronization. It is used as a signal. Thus, by performing synchronization detection with a light receiving element for APC, the number of sensors dedicated to synchronization detection can be reduced, the number of parts can be reduced, and a cost reduction effect can be expected.

  The technology of the present invention described above is naturally effective when an integrated surface emitting laser (VCSEL) as shown in FIG. 17 is used as a light source. For example, when a 40 channel surface emitting laser (VCSEL) array is used, With two light sources, a beam of 4 channels of 40 colors can be obtained, and the cost of the light source can be reduced while maintaining the high speed of 40 beam writing.

[Fifth Embodiment]
Next, an embodiment of an image forming apparatus provided with the above-described optical scanning device of the present invention in a writing unit will be described.
FIG. 27 is a schematic configuration diagram of a multicolor image forming apparatus showing an embodiment of the present invention. In the figure, reference numeral 31 is a photoconductor as an image carrier, 32 is a charger for charging the photoconductor, 33 is an electrostatic latent image formed by exposing each charged photoconductor to a beam modulated in accordance with an image signal. A writing unit using the above-described optical scanning device for forming the image; 34, a developing unit for developing the latent image on the photoconductor with each color toner to make it visible; and 35, cleaning the transfer residual toner on the photoconductor Cleaning means 36 is a transfer charging means for transferring the visible image on the photosensitive member to the recording material, 37 is a transfer belt for carrying and transporting the recording material, 38a and 38b are driven by a driving roller on which the transfer belt is stretched. 40, a fixing means for fixing the image transferred to the recording material, 40, a paper feed cassette containing a sheet-like recording material (for example, recording paper) S, and 41, a paper feeding roller for feeding the recording material S , 42 indicates a recording material S fed by a paper feed roller. Separating rollers for separating the recording materials one after another, 43 and 44 are conveying rollers for conveying the recording material, and 45 is a registration roller for feeding the recording material S to the transfer belt 37 in synchronization with image formation on each photoconductor. . Further, Y, M, C, and K attached to the reference numerals represent the colors of the image, and indicate Y: yellow, M: magenta, C: cyan, and K: black, respectively.

  The four photoconductors 31Y, 31M, 31C, and 31K are juxtaposed along the transfer belt 37, rotate in the clockwise direction, and in the order of the rotation direction, the chargers 32Y, 32M, 32C, and 32K, the developing devices 34Y, 34M, 34C, 34K, transfer charging means 36Y, 36M, 36C, 36K, and cleaning means 35Y, 35M, 35C, 35K are provided.

  The chargers 32Y, 32M, 32C, and 32K constitute a charging device for uniformly charging the surface of the photosensitive member. The charger includes a charging member of a contact charging method such as a roller or brush. There are non-contact charging types such as charging chargers. The writing unit 33 irradiates the photosensitive member surfaces between the chargers 32Y, 32M, 32C, and 32K and the developing devices 34Y, 34M, 34C, and 34K with the writing unit 33, and electrostatically applies to the photosensitive members 31Y, 31M, 31C, and 31K. A latent image is formed. Then, based on the electrostatic latent image, toner images of respective colors Y, M, C, and K are formed on the photoreceptor surface by the developing units 34Y, 34M, 34C, and 34K. Further, after the toner images of the respective colors are sequentially superimposed and transferred onto the recording material S conveyed by the transfer belt 37 by the transfer charging units 36Y, 36M, 36C, and 36K, the recording material S is finally transferred by the fixing unit 39. The image is fixed on the screen.

  In the optical scanning device shown in FIG. 1, only the figures corresponding to the two photoconductors 11a and 11b are shown, but the light shown in FIG. 1 is placed in the writing unit 33 of the image forming apparatus shown in FIG. In addition to the configuration similar to the scanning device, as described in the fourth embodiment, a configuration in which a scanning optical system similar to the illustrated optical system is disposed at a symmetrical position with the deflector 7 interposed therebetween. Thus, optical scanning corresponding to the above-described four photoconductors 31Y, 31M, 31C, and 31K can be performed.

Next, specific implementation data of the optical system of the optical scanning apparatus having the configuration shown in the embodiment of FIG. 1 is shown below.
-Wavelength of light source 1, 1 ': 655nm
-Focal length of coupling lens 3, 3 ': 15mm
-Coupling action: Collimating action-Polygon mirror 7: Number of deflecting reflecting surfaces: 4
Inscribed circle radius: 7mm
Further, cylindrical lenses 5 and 5 ′ having a focal length of 110 mm are disposed between the optical path switching unit 4 (or the polarization switching unit 13 and the polarization separation unit 14) and the deflecting unit (polygon mirror) 7. A long line image is formed in the main scanning direction in the vicinity of the surface.

Lens data after the deflector is shown below.
The first surfaces of the first scanning lenses 8a and 8b and both surfaces of the second scanning lenses 10a and 10b are expressed by the following equations (1) and (2).

Main scanning non-arc type The surface shape in the main scanning surface is a non-arc shape, the paraxial radius of curvature in the main scanning surface on the optical axis is Rm, the distance in the main scanning direction from the optical axis is Y, and the cone When the constant is K and the higher-order coefficients are A1, A2, A3, A4, A5, A6,..., The depth in the optical axis direction is X and is expressed by the following polynomial (1).
X = (Y2 / Rm) / [1 + √ {1- (1 + K) (Y / Rm) 2}
+ A1 ・ Y + A2 ・ Y ² + A3 ・ Y ³ + A4 ・ Y ⁴ + A5 ・ Y ⁵ + A6 ・ Y ⁶ + ・ ・
... (1)
Here, when a numerical value other than zero is substituted for the odd-order coefficients A1, A3, A5,..., It has an asymmetric shape in the main scanning direction.
In this embodiment, only the even order is used, and it is a symmetric system in the main scanning direction.

Sub-scanning curvature formula The following formula (2) shows a formula in which the sub-scanning curvature changes according to the main scanning direction.
Cs (Y) = 1 / Rs (0)
+ B1 · Y + B2 · Y ² + B3 · Y ³ + B4 · Y ⁴ + B5 · Y ⁵ + ··
... (2)
Here, when a value other than zero is substituted for the odd odd power coefficients B1, B3, B5,..., The radius of curvature of sub-scanning becomes asymmetric in the main scanning direction.
Further, the second surface of the first scanning lens is a rotationally symmetric aspheric surface, and is expressed by the following equation (3).

A rotationally symmetric aspheric surface The paraxial radius of curvature of the optical axis is R, the distance from the optical axis in the main scanning direction is Y, the cone constant is K, the higher order coefficients are A1, A2, A3, A4, A5, A6,. When represented by the following polynomial, the depth in the optical axis direction is X.
X = (Y2 / R) / [1 + √ {1- (1 + K) (Y / Rm) 2}
+ A1 • Y + A2 • Y ² + A3 • Y ³ + A4 • Y ⁴ + A5 • Y ⁵ + A6 • Y ⁶ + ••
... (3)

The shape of the first surface of the first scanning lens Rm = −279.9, Rs = −61.0
K = -2.900,000E + 01
A4 = 1.755765E-07
A6 = −5.491789E-11
A8 = 1.087700E-14
A10 = -3.183245E-19
A12 = −2.6635276E-24
B1 = −2.066347E-06
B2 = 5.727737E-06
B3 = 3.1252201E-08
B4 = 2.280241E-09
B5 = −3.729852E-11
B6 = −3.283274E-12
B7 = 1.765590E-14
B8 = 1.732929E-15
B9 = −2.889722E-18
B10 = -1.984531E-19
In the above, “E + 01” means “× 10 ⁰¹ ” and “E-07” means “× 10 ^-07 ”, and the same applies to the following.

Shape of second surface of first scanning lens R = −83.6
K = −0.549157
A4 = 2.748446E-07
A6 = −4.502346E-12
A8 = -7.366455E-15
A10 = 1.803003E-18
A12 = 2.727900E-23

The shape of the first surface of the second scanning lens Rm = 6950, Rs = 110.9
K = 0.000000 + 00
A4 = 1.549648E-08
A6 = 1.292741E-14
A8 = −8.811446E-18
A10 = −9.182312E-22
B1 = −9.593510E-07
B2 = −2.135322E-07
B3 = −8.079549E-12
B4 = 2.390609E-12
B5 = 2.881396E-14
B6 = 3.693775E-15
B7 = -3.258754E-18
B8 = 1.814487E-20
B9 = 8.72085E-23
B10 = −1.3340807E-23

The shape of the second surface of the second scanning lens Rm = 766, Rs = −68.22
K = 0.000000 + 00
A4 = -1.150396E-07
A6 = 1.096926E-11
A8 = −6.5542135E-16
A10 = 1.9844381E-20
A12 = −2.411512E−25
B2 = 3.644079E-07
B4 = −4.847051E-13
B6 = −1.666159E-16
B8 = 4.534859E-19
B10 = −2.819319E-23
Note that the refractive index of the scanning lens at the operating wavelength is 1.52724.

The optical arrangement is shown below.
Distance d1: 64 mm from the deflection reflection surface of the deflector to the first surface of the first scanning lens
Center wall thickness d2 of the first scanning lens: 22.6 mm
The distance d3 from the second surface of the first scanning lens to the first surface of the second scanning lens: 75.9 mm
Center wall thickness d4 of second scanning lens: 4.9 mm
Distance d2: 158.7 mm from the second surface of the second scanning lens to the surface to be scanned

In the optical scanning device shown in FIG. 1, a soundproof glass 6 and a dustproof glass (not shown) having a refractive index of 1.514 and a thickness of 1.9 mm are arranged, and the soundproof glass 6 generates ghost light. In order to prevent this, it is installed at an angle of 10 deg with respect to the direction parallel to the main scanning direction in the deflection rotation plane.
Moreover, although not shown about dustproof glass, it is arrange | positioned between the 2nd scanning lenses 10a and 10b and the to-be-scanned surfaces 11a and 11b.

It is a schematic block diagram of the optical scanning device which shows one Embodiment of this invention. It is a figure which shows a part of optical scanning device of 1st Embodiment. It is a figure which shows an example of the optical path switching means which combined the diffractive optical element. It is a figure which shows schematic structure of the diffractive optical element which makes an optical path switching means. It is a figure which shows an example of a functional operation | movement of the diffractive optical element which makes an optical path switching means. It is a figure which shows another example of the functional operation | movement of the diffractive optical element which makes an optical path switching means. It is explanatory drawing of the orientation direction of the liquid crystal of a diffractive optical element, and the inclination direction of a grating | lattice. It is a figure which shows an example of the functional operation | movement of the inclined diffractive optical element. It is a figure which shows another example of the functional operation | movement of the inclined diffractive optical element. It is a figure which shows the outline of a cross-sectional structure of the liquid crystal hologram element before interference exposure. It is explanatory drawing of the hologram formation process by the phase separation of a liquid crystal hologram element. It is a figure which shows a part of optical scanning apparatus of 2nd Embodiment. It is a figure which shows an example of the polarization separation means which combined the diffractive optical element. It is a figure which shows schematic structure of the polarization switching means using a ferroelectric liquid crystal element. It is a schematic diagram explaining the switching operation | movement of a ferroelectric liquid crystal element. It is a schematic diagram which shows operation | movement of a polarization switching means. It is a figure which shows an example of a surface emitting laser (VCSEL) array. It is a figure which shows the response speed characteristic of the liquid crystal element with respect to temperature. It is a block diagram which shows the outline of the optical scanning device provided with the temperature adjustment means. It is a figure for demonstrating the optical scanning by the time division light of an optical path switching means. It is explanatory drawing of the problem when the time division light of an optical path switching means injects into the same reflective surface of a deflector. It is a figure which shows the timing chart of the exposure for multiple colors. It is a figure which shows the timing chart for varying the exposure amount according to a color. It is a figure which shows an example of a pitch adjustment means. It is a figure for demonstrating an example of the actual pitch adjustment method. It is explanatory drawing of the arrangement position of a synchronous detection sensor. 1 is a schematic configuration diagram of a multicolor image forming apparatus showing an embodiment of the present invention.

Explanation of symbols

1, 1 ': Light source (semiconductor laser (LD))
2, 2 ': incident mirror,
3, 3 ': Coupling lens 4: Optical path switching means 5, 5' (5a, 5b, 5c, 5d): Cylindrical lens 6: Soundproof glass 7: Deflection means (deflector (polygon mirror))
8 (8a, 8b): first scanning lens 9: mirror for turning back the optical path 10a, 10b: second scanning lens 11a, 11b: surface to be scanned 12: aperture stop (aperture)
13: Polarization switching means 14: Polarization separation means 31Y, 31M, 31C, 31K
32Y, 32M, 32C, 32K: charger 33: writing unit 34Y, 34M, 34C, 34K: developing unit 35Y, 35M, 35C, 35K: cleaning means 36Y, 36M, 36C, 36K: transfer charging means 37: transfer Belt 38a: Drive roller 38b: Driven roller 39: Fixing means 40: Paper feed cassette 41: Paper feed roller 42: Separation roller 43, 44: Conveyance roller 45: Registration roller 50: Diffraction optical element (optical path switching means)
60: Diffractive optical element (polarized light separating means)
70: Ferroelectric liquid crystal element (polarization switching means)
S: Recording material

Claims (17)

In an optical scanning apparatus having a light source to be modulated and driven, a deflection unit having a multi-surface reflection surface, and a scanning optical system for guiding a beam deflected and scanned by the deflection unit to a surface to be scanned.
An optical path switching unit is provided between the light source and the deflecting unit, and the optical path switching unit can switch between a first optical path and a second optical path, and an incident optical path of the first optical path to the deflecting unit wherein it is second and the incident light path of the optical path has an opening angle of approximately [pi / 2, and has a reflecting surface of the deflection means 4 side, the beam and the second passing through the first optical path An optical scanning device characterized in that beams passing through an optical path are guided to different surfaces to be scanned . 2. The optical scanning device according to claim 1, further comprising incident mirrors on the first optical path and the second optical path between the optical path switching unit and the deflecting unit, respectively, from the incident mirror of the first optical path. An optical scanning device characterized in that the optical path to the deflecting means and the optical path from the incident mirror of the second optical path to the deflecting means have an opening angle of approximately π / 2 . The optical scanning device according to claim 1 or 2 ,
The optical path switching means comprises a diffractive optical element and an electric field applying means capable of applying an electric field to the diffractive optical element . The optical scanning apparatus according to claim 3 Symbol mounting,
The diffractive optical element that constitutes the optical path switching means has a periodic structure of a region made of non-polymerizable liquid crystal and a region made of isotropic medium, and is refracted in a specific polarization direction of the region made of non-polymerizable liquid crystal. An optical scanning device characterized in that the rate changes with the application of an electric field, and the light having the specific polarization direction is transmitted or diffracted according to the application of the electric field . The optical scanning device according to claim 3 or 4 ,
The diffractive optical element that constitutes the optical path switching means is a polymer-dispersed liquid crystal hologram element in which a periodic phase separation structure of a region mainly composed of a polymer and a region mainly composed of a non-polymerizable liquid crystal is formed. An optical scanning device. In an optical scanning apparatus having a light source to be modulated and driven, a deflecting unit having a multi-surface reflecting surface, and a scanning optical system for guiding a beam scanned by the deflecting unit to a surface to be scanned .
Between the light source and the deflecting means, there is provided an optical path switching means comprising a polarization switching means capable of switching the polarization direction and a polarization separation means for separating polarized light components orthogonal to each other. An optical path that can be switched between an optical path and a second optical path, the incident optical path of the first optical path to the deflecting means and the incident optical path of the second optical path have an opening angle of approximately π / 2, and The optical scanning device according to claim 1, wherein the deflecting unit has four reflecting surfaces, and the beam passing through the first optical path and the beam passing through the second optical path are guided to different scanning surfaces . 7. The optical scanning device according to claim 6, further comprising incident mirrors on the first optical path and the second optical path between the optical path switching unit and the deflecting unit, respectively, from the incident mirror of the first optical path. An optical scanning device characterized in that the optical path to the deflecting means and the optical path from the incident mirror of the second optical path to the deflecting means have an opening angle of approximately π / 2 . The optical scanning device according to claim 6 or 7 ,
The polarization separation means includes a diffractive optical element, and the diffractive optical element has a periodic structure including a region exhibiting optical anisotropy and a region exhibiting optical isotropy, and is orthogonal to each other by transmission and diffraction. An optical scanning device that separates polarized light components to be separated . The optical scanning apparatus according to claim 8 Symbol mounting,
The polarization switching means includes a pair of transparent substrates, an alignment film provided on the inner surface side of the substrate, a liquid crystal layer composed of a chiral smectic C phase that is homogeneously aligned by the alignment film, and the transparent substrate surface. An optical scanning device comprising an electric field applying means for applying an electric field in a substantially vertical direction, and rotating a specific polarization direction by approximately 90 ° in accordance with the electric field strength . The optical scanning device according to any one of claims 1 to 9,
An optical scanning device comprising temperature adjusting means . In the optical scanning device according to any one of claims 1 to 10,
An optical scanning device characterized in that synchronization detection means is provided on the side opposite to the scanning optical system with an incident beam as a boundary . In the optical scanning device according to any one of claims 1 to 11,
An optical scanning apparatus characterized in that pitch adjusting means for adjusting a sub-scanning direction pitch of a plurality of scanning lines formed on the surface to be scanned is disposed between the optical path switching means and the deflecting means . The optical scanning device according to any one of claims 1 to 12,
An optical scanning device having a plurality of light sources, wherein the plurality of light sources are arranged at different positions in the sub-scanning direction . The optical scanning device according to any one of claims 1 to 13,
An optical scanning device characterized in that when a common light source scans different scanning surfaces, different light amounts are set for the respective scanning surfaces. The optical scanning device according to any one of claims 1 to 14,
An optical scanning device using a surface emitting laser as the light source. In an image forming apparatus including a writing unit that forms a latent image by irradiating an image carrier, which is a surface to be scanned, with a beam from a light source.
An image forming apparatus comprising the optical scanning device according to claim 1 in the writing unit. The image forming apparatus according to claim 16.
A plurality of the image carriers are provided, and latent images formed on the plurality of image carriers by the writing unit are developed with developers of different colors to be visualized, and each color formed on the plurality of image carriers is developed. An image forming apparatus for forming a multicolor or full color image by transferring an image on a recording material directly or via an intermediate transfer member.

Images