JP4340516B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device.

  In an optical scanning apparatus known in connection with an image forming apparatus such as an optical drawing apparatus, an optical printer, a digital copying machine, an optical plotter, an optical facsimile, etc., a light beam emitted from a light source is generally guided to an optical deflector. The deflected light beam deflected by the deflector is guided to the surface to be scanned through the scanning imaging optical system.

  In an image forming apparatus such as an optical drawing apparatus in which an optical scanning device is used, various types of photosensitive media, a developing device, a fixing device, and the like depending on an image forming process for developing or transferring a latent image formed by optical scanning. The members and devices need to be arranged according to the above process, and the layout of these members and devices is greatly limited. On the other hand, since the optical path from the light source to the surface to be scanned can be easily bent by the mirror, the layout is determined by giving the maximum degree of freedom to the layout of the above-mentioned members and devices. Generally, the layout of the optical scanning device is set in accordance with the “arrangement of members and devices”.

  For this reason, in an optical scanning device incorporated in an image forming apparatus, one or more “optical path bending mirrors” are generally arranged on an optical path from a light source to a surface to be scanned.

  On the other hand, in the above optical scanning device, in order to form a “light spot having a desired size and shape” on the surface to be scanned, “beam shaping” is performed by shielding the peripheral portion of the light beam from the light source side with an aperture. This is performed on the light source side with respect to the deflector.

  In order to perform beam shaping properly, the principal ray of the light beam from the light source side must pass through the center of the aperture opening, but one or more optical path bending mirrors are arranged between the light source and the aperture. The “direction of the reflection surface” of the mirror for bending the optical path is likely to change over time due to the influence of mechanical vibration, etc., and the direction change angle: Δθ is very small when the direction of the reflection surface changes. Since the direction of the reflected light beam changes by 2Δθ, the light beam traveling toward the aperture is likely to be greatly displaced with respect to the aperture.

  If the positional relationship between the light beam and the aperture shifts over time due to changes in the direction of the reflecting surface of the mirror for bending the optical path and environmental changes, if the "deviation" increases to some extent, the light shielding by the aperture increases. The light intensity of the light spot formed on the surface to be scanned becomes insufficient and proper image writing cannot be performed. If such a situation has occurred, conventionally, it has been dealt with by a “method of adjustment by a service person”.

  The present invention effectively prevents the “deviation of the positional relationship between the light beam and the aperture due to the change in the direction of the reflecting surface of the optical path bending mirror with time” in the optical scanning device, and the light spot formed on the surface to be scanned. It is an object to make it possible to write an appropriate image by always keeping the light intensity of the image at an appropriate level.

  The optical scanning device according to the present invention “scans the deflected light beam by modulating the intensity of the light beam emitted from one or more light sources according to the image signal by the modulating means, deflecting the light beam modulated in intensity by the optical deflector. An optical scanning device that forms a light spot by condensing on a surface to be scanned by an imaging optical system and optically scans the surface to be scanned at a constant speed ”, an aperture, an optical path bending mirror, a relay lens And have.

The “aperture” is for performing “beam shaping” of the light beam modulated by the modulation means “before the deflection by the optical deflector”, and is arranged on the optical path from the light source to the optical deflector.
The beam shaping performed by the aperture is to form a “light spot having a desired size and shape” on the surface to be scanned as described above, and the aperture performs beam shaping “every beam”. “For each luminous flux”, when the luminous flux is one luminous flux, one aperture performs beam shaping of the luminous flux. However, when there are a plurality of luminous fluxes, the number of apertures is the same as the number of luminous fluxes. Each aperture shapes one light beam.
The “optical path bending mirror” is disposed on one or more optical paths from one or more light sources to the optical deflector, and “bends the optical path of the light beam according to the optical layout of the optical scanning device”. Is used. One optical path bending mirror may bend the optical path of a single light beam or may bend the optical paths of a plurality of light beams.

The “relay lens” is a “geometrically optically” connection between the “start point of divergence” of the divergent light beam from one or more light sources, the “reflection point” of the one or more optical path bending mirrors, and the aperture. A “substantial conjugate relationship” is used, and two or more are used.
That is, the relay lens has a pair of a light source side relay lens disposed between the light source and the optical path bending mirror and an aperture side relay lens disposed between the optical path bending mirror and the aperture. . The number of such relay lens pairs is the same as the number of light beams.
The relay lens on the light source side says, “The starting point of the divergence of the divergent light beam from the light source side and the reflection point that reflects the light beam of the optical path bending mirror that bends the optical path of this light beam are substantially conjugate optically. It is provided for each luminous flux so as to be “related”.
In addition, the relay lens on the aperture side is such that “the reflection point of the mirror for bending the optical path and the aperture that shapes the light beam reflected at this reflection point have a substantially conjugate relationship geometrically”. Provided for each luminous flux.
Then, with the relay lens on the light source side and the relay lens on the aperture side, an "image of the divergence start point of the light beam emitted from the light source" is placed in the vicinity of the center of the aperture opening of the aperture for beam shaping the light beam. To form a geometric optical image.

That is, if there is one light source and one optical path bending mirror is arranged between the starting point of the divergence of one light beam emitted from the light source and the aperture, the starting point and the optical path of the divergence are described above. One relay lens ( relay lens on the light source side) having a “geometrical optically substantial conjugate relationship” between them is disposed between the bending mirror and the optical path bending mirror and the aperture. Is another relay lens (aperture-side relay lens) having “a geometrically optically conjugate relationship”. In this way, two relay lenses are arranged.

  One or more of the light sources in the optical scanning device according to claim 1 are defined as a “laser light source”, and the laser light emitted from the laser light source is condensed on a modulation section of an “AO modulation element (acousto-optic element)” serving as a modulation means. The intensity modulation is performed according to the image signal by the AO modulation element, and the intensity-modulated light beams are incident on the relay lens as “divergent light beams from the light source side”. ).

  One or more of the light sources in the optical scanning device according to claim 1 may be a “semiconductor laser” (claim 3). Since the light beam emitted from the semiconductor laser is divergent, the light beam emitted from the semiconductor laser is incident on the relay lens as a “divergent light beam from the light source side”, and the geometry of the “light source” that is the origin of the divergence. The imaging position of the optical image is “substantially set on the optical path bending mirror”, and the light beam reflected by the optical path bending mirror is incident on another relay lens. The imaging position of the geometrical optical image at the “reflection point” can be “substantially set at (center of) the aperture opening”.

  “Modulation means” in the case of using a semiconductor laser as a light source is a modulation circuit that modulates the intensity of light emitted from the semiconductor laser according to an image signal.

The optical scanning device according to any one of claims 1 to 3, wherein the number of light sources is plural, and the emission wavelengths of the respective light sources are different from each other (claim 4). In this case, the number of light sources may be 3, and these three light sources may emit red, green, and blue laser beams. The optical scanning device according to claim 5 may be a “device that performs optical scanning using a color photographic paper as an actual surface to be scanned” (claim 6).
In the optical scanning device according to any one of claims 1 to 6, the optical deflector can be a rotary polygon mirror, and the scanning imaging optical system can be an fθ lens.
In the optical scanning device, when the number of light sources is plural, the optical deflector and the scanning imaging optical system are shared by the plural light beams.

  The optical scanning device according to claim 1, 2, or 3 includes “when the number of light sources is one”, but when there are a plurality of light sources as in the optical scanning device according to claims 4 to 6. The plurality of light sources may be constituted by “a combination of different light sources” such as a semiconductor laser, a solid-state laser, and a gas laser.

  The “geometrical conjugate relationship” does not need to be a strict conjugate relationship, and it is sufficient that the conjugate relationship is substantially established. However, as long as an image can be formed in the vicinity of the center of the opening of the aperture, it may be slightly deviated from the strict conjugate relationship.

  As described above, in the optical scanning device according to the present invention, one or more optical path bending mirrors are disposed between the divergence start point of the divergent light beam from the light source side and the aperture, but 2 provided on the optical path. Since the above relay lens has a “geometrically substantial conjugate relationship” between the “starting point of divergence” and the reflection point and aperture of one or more optical path bending mirrors, the reflection of the optical path bending mirrors. Even if the orientation of the surface changes with time, the light intensity of the light spot formed on the surface to be scanned can be always kept appropriate. Appropriate image writing is possible.

FIG. 2 shows a characteristic part in the first embodiment of the optical scanning device.
This optical scanning device modulates the intensity of a light beam emitted from one light source 1 according to an image signal by a modulating means, deflects the intensity-modulated light beam by an optical deflector, and scans the deflected light beam. The light source 1 is a “semiconductor laser”, which is a light scanning device that forms a light spot by condensing on a surface to be scanned by an image optical system, and optically scans the surface to be scanned at a constant speed.
FIG. 2 shows the “optical arrangement between the light source 1 and the beam shaping aperture AP” in a state where the optical path is linearly developed.

The divergent light beam emitted from the light source 1 is incident on the light source side relay lens L1 as a “divergent light beam from the light source side”, converted into focused light, guided to the optical path bending mirror 3, and the optical path bent. When reflected by the mirror 3, the light becomes a divergent light beam and enters the aperture-side relay lens L 2, is converted again into focused light, is guided to the aperture AP, passes through the opening of the aperture AP, Beam shaped ".

  In the relay lens L1 on the light source side, the position of the light source of the light source 1 (the starting point of the divergent light beam divergence) and the optical path bending mirror 3 is in a “geometrically substantial conjugate relationship”. Therefore, geometrically, an image formed by the relay lens L1 of the light source of the semiconductor laser 1 is substantially formed on the “reflecting surface of the optical path bending mirror 3”. In terms of wave optics, as shown in FIG. 2, the focused light from the relay lens L1 is not imaged as a point, and a beam waist is formed at the reflection point position.

  Reflected light from the optical path bending mirror 3 is geometrically optically “substantially imaged” at the center of the aperture of the aperture AP by the relay lens L2 with the “image position” as the object point position. Also in this case, the light beam forms a beam waist centered on the center position of the opening. As shown in the figure, the aperture width of the aperture AP is “set smaller than the beam waist diameter of the condensed light flux” by the relay lens L2, and the aperture AP shields the light flux peripheral portion and performs beam shaping.

  As described above, the light source 1 of the semiconductor laser, which is the light source 1, the optical path bending mirror 3, and the aperture AP are connected by the two relay lenses L1 and L2 in a geometrically optically conjugate relationship. Therefore, even if the direction of the reflecting surface of the optical path bending mirror 3 changes over time or with environmental changes and becomes “as shown by the broken line”, the light reflected by the optical path bending mirror 3 is ( The principal ray is guided to the center of the aperture of the aperture AP by the relay lens L2 (as indicated by a broken line), and proper beam shaping can always be performed regardless of the change in the direction of the reflecting surface of the optical path bending mirror 3. The light intensity of the light spot on the scanned surface can always be kept appropriate.

That is, the optical scanning device of the embodiment shown in FIG. 2 modulates the intensity of a light beam emitted from one light source 1 according to an image signal by a modulation means (not shown), and the intensity-modulated light beam An optical deflector (not shown) deflects the deflected light beam onto a scanned surface (not shown) by a scanning imaging optical system (not shown) to form a light spot, which is scanned. In an optical scanning device that optically scans a surface at a constant speed, an aperture AP that performs beam shaping of an intensity-modulated light beam before deflection by an optical deflector, and an optical path disposed on the optical path from the light source 1 to the optical deflector There are two geometrically optically conjugate relations between the bending mirror 3, the starting point of the divergent light beam from the light source 1, the reflection point of the optical path bending mirror 3, and the aperture. relay lens L1, and a L2, the light source 1 is semiconductive It is a laser.

FIG. 1 shows an embodiment of an optical scanning device.
The optical scanning device of FIG. 1 is a device that performs color image writing by performing optical scanning on the color photographic paper 11 with three light beams of red (R), green (G), and blue (B).

  “Light sources” denoted by reference numerals 1R, 1G, and 1B are laser light sources, respectively. The light source 1R emits a red laser beam having a wavelength of 690 nm. The light source 1G emits a green laser beam having a wavelength of 532 nm, and the light source 1B emits a blue laser beam having a wavelength of 473 nm. Laser beams emitted from the laser light sources 1G and 1B are so-called “harmonic components”.

Each color laser beam emitted from the light sources 1R, 1G, and 1B passes through the corresponding modulation means 2R, 2G, and 2B, and is modulated in accordance with the image signal.
The modulation means 2R, 2G, and 2B are “AO modulation elements (acousto-optic elements)”, and what is used for optical scanning is “light beams diffracted according to image signals (modulated light beams)”.

  Each color laser beam emitted from the light sources 1R, 1G, and 1B is directed toward the modulation unit of the modulation means 2R, 2G, and 2B corresponding to each light source by the action of a condensing lens included in the light source. Condensed to about 1 mm.

  The “modulated light beam” that has passed through the modulation means 2R, 2G, and 2B becomes a “divergent light beam from the light source side” and is incident on the relay lenses L1R, L1G, and L1B to be converted into a focused light beam. The light enters the mirrors 3R, 3G, and 3B, is reflected, passes through the relay lenses L2R, L2G, and L2B, passes through the apertures of the apertures APR, APG, and APB, and is “beam-shaped” to be collimated lenses 4R, 4G, and 4B. Is converted into a “parallel light beam having a predetermined light beam diameter (determined by the aperture width of the apertures AP1 to AP3 and the NA of the collimating lenses 4R to 4B)”.

  These parallel light beams are condensed in the sub-scanning direction by the cylindrical lenses 5R, 5G, and 5B, and are combined into “one light beam” by the optical path combining element 6 having a dichroic film, and the rotation polygon mirror 7 serving as an optical deflector. Incident on the deflecting reflecting surface.

  When the rotary polygon mirror 7 rotates at a constant speed, the “synthesized light beam” is deflected at a constant angular velocity, and is transmitted through the lenses 8, 9, 10 constituting the “fθ lens” that is a scanning imaging optical system, A light spot is formed on the color photographic paper 11 constituting the surface to be scanned, and optical writing is performed by optically scanning the color photographic paper 11 at a constant speed. The color photographic paper 11 forming the substance of the surface to be scanned is conveyed at a constant speed in the sub-scanning direction orthogonal to the drawing. With this conveyance, the main scanning is repeated in the sub-scanning direction and a two-dimensional color image is written. It ’s getting crowded.

  Each color laser beam deflected by the rotary polygon mirror 7 is imaged by the lenses 8, 9, and 10, but the beam toward the optical scanning start position is reflected by the mirror 12 when it passes through the lenses 8 and 9. The light is incident on the photodetector 13 and detected. Based on the detection signal of the photodetector 13, “synchronization of optical writing start” by the light spot is taken, and the optical writing start position is aligned.

  As shown in FIG. 1, each of the light beam diameter portions of about 0.1 mm collected on the modulation sections of the modulation means 2R, 2G, and 2B is the starting point of the divergence of “the divergent light beam from the light source side”. The divergence starting point and the optical path bending mirrors 3R, 3G, and 3B are substantially geometrically conjugated by the relay lenses L1R, L1G, and L1B, respectively, and the optical path bending mirrors 3R, 3G, and 3B are apertured. The relay lenses L2R, L2G, and L2B have a “geometrically substantial conjugate relationship” between the APR, APG, and APB.

Therefore, even if the direction of the reflecting surface of the optical path bending mirrors 3R, 3G, and 3B changes with time, the image of the starting point of the divergence of the luminous flux emitted from each light source is the aperture of the aperture that shapes the luminous flux. Since geometric optical imaging is performed for each light beam in the vicinity of the center, beam shaping by the apertures APR, APG, and APB is performed appropriately, and the light intensity of each light spot on the scanned surface 11 is always kept appropriate. Appropriate optical scanning is realized.

In the optical scanning device shown in FIG. 1, the intensity of a light beam emitted from one or more light sources 1R, 1G, 1B is modulated in accordance with an image signal by modulation means 2R, 2G, 2B, and the intensity is modulated. The deflected light beam is deflected by the optical deflector 7, and the deflected light beam is condensed on the scanned surface 11 by the scanning imaging optical systems 8, 9, 10 to form a light spot. In an optical scanning device for optically scanning optically, apertures APR, APG, and APB that perform beam shaping of an intensity-modulated light beam before deflection by the optical deflector 7 and one or more light sources from one or more light sources to the optical deflector 7 One or more optical path bending mirrors L1R, L1G, and L1B disposed on the optical path, a starting point of divergent light flux from one or more light sources, a reflection point of the one or more optical path bending mirrors, and an aperture Is geometrically optically 2 or more relay lenses L1R to specific conjugate relation, an optical scanning apparatus having L1G, L1B, L2R, L2G, and L2B.

  The light sources 1R, 1G, and 1B are laser light sources, and the laser light emitted from the laser light source is condensed on the modulation unit of the AO modulation elements 2R, 2G, and 2B, and intensity-modulated according to the image signal, and then intensity-modulated. Each of the luminous fluxes is incident on the relay lenses L1R, L1G, and L1B as divergent luminous fluxes from the light source side (claim 2).

  There are a plurality of light sources 1R, 1G, and 1B, the emission wavelengths are different from each other (Claim 4), the number of light sources 1R, 1G, and 1B is 3, and these three light sources emit red, green, and blue laser beams. An optical scanning device (Claim 6) that performs light scanning using a color photographic paper as an actual scanning surface 11 (Claim 6), and the optical deflector 7 is a rotary polygon mirror. The imaging optical systems 8, 9, and 10 are fθ lenses.

It is a figure which shows one Embodiment of an optical scanning device. It is a figure which shows another form of implementation of an optical scanning device only for a characteristic part.

Explanation of symbols

1R, 1G, 1B Light source (Laser light source)
2R, 2G, 2B modulation means (AO modulation element)
L1R, L1G, L1B Relay lens 3R, 3G, 3B Optical path bending mirror L1R, L1G, L1B Relay lens APR, APG, APB Aperture

Claims (7)

A light beam emitted from one or more light sources is intensity-modulated by a modulation means in accordance with an image signal, the light beam modulated in intensity is deflected by an optical deflector, and the deflected light beam is scanned by a scanning imaging optical system. In an optical scanning device that focuses light on top to form a light spot and optically scans the scanned surface at a constant speed,
One or more apertures that perform beam shaping of the intensity-modulated beam for each beam before deflection by the optical deflector;
One or more optical path bending mirrors disposed on one or more optical paths from the one or more light sources to the optical deflector;
The starting point of the divergence of the divergent light beam from the light source side and the reflection point of the light path bending mirror that bends the optical path of the light beam to reflect the light beam so as to have a substantially conjugate relationship geometrically. A relay lens on the light source side provided for each luminous flux;
Aperture side provided for each light beam so as to have a geometrically optically conjugate relationship between the reflection point of the optical path bending mirror and the aperture for beam shaping the light beam reflected at the reflection point. Relay lens,
An optical scanning device characterized in that an image of a divergence starting point of a light beam emitted from a light source can be geometrically optically imaged for each light beam in the vicinity of the center of an aperture of an aperture for beam shaping the light beam. . The optical scanning device according to claim 1,
At least one of the light sources is a laser light source, the laser light emitted from the laser light source is condensed on a modulation unit of an AO modulation element, and the intensity is modulated in accordance with an image signal by the AO modulation element. An optical scanning device that causes a light beam to enter a relay lens as a divergent light beam from a light source side. The optical scanning device according to claim 1,
One or more of the light sources are semiconductor lasers. The optical scanning device according to any one of claims 1 to 3,
An optical scanning device having a plurality of light sources and different emission wavelengths between the light sources. The optical scanning device according to claim 4.
3. An optical scanning device characterized in that the number of light sources is 3, and these three light sources emit red, green, and blue laser beams. The optical scanning device according to claim 5.
An optical scanning apparatus characterized in that color scanning is performed using a color photographic paper as an actual surface to be scanned. The optical scanning device according to any one of claims 1 to 6,
An optical scanning device, wherein the optical deflector is a rotary polygon mirror, and the scanning imaging optical system is an fθ lens.

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