JP4632751B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device.

  In general, an optical scanning apparatus known in connection with an optical drawing apparatus, an optical printer, a digital copying machine, an optical plotter, an optical facsimile, etc., emits light from the light source side in order to form a light spot of a desired shape on the surface to be scanned. "Beam shaping" is performed in which the peripheral portion of the luminous flux is shielded by an aperture.

  In recent years, optical scanning devices have been strongly demanded to increase the speed of optical scanning and “higher density by reducing the diameter of the light spot”, but when beam shaping is performed, a part of the light beam emitted from the light source is scanned. Since the light is shielded from the surface, beam shaping is a negative factor in terms of light energy utilization efficiency. In order to reduce the diameter of the light spot, it is preferable to increase the beam diameter as much as possible. However, since the beam shaping by the aperture limits the beam diameter, the beam shaping is also a negative factor in this aspect.

  In the optical scanning device, the light beam from the light source side is generally a “divergent light beam”, which is collimated by a collimator lens, and the collimated light beam is converted into a “main” beam near the position of the deflecting reflection surface of the optical deflector by a cylindrical lens. Imaging is performed as a “line image that is long in the scanning direction”.

  The divergence angle of the “divergent light beam” from the light source side is not necessarily uniform, and is slightly different depending on the type of light source and each individual. If there is such “divergence” of the divergence angle, if the beam shaping by the aperture is not performed, the spot diameter of the light spot on the surface to be scanned varies depending on the divergence angle variation. Such “spot diameter variation” greatly affects the image quality of a written image in high-density optical scanning.

  To the best of the applicant's knowledge, there is no conventional technique that has a problem of “spot diameter variation” when beam shaping is not performed.

  In addition, laser light beams from three light sources that emit red, green, and blue laser beams are modulated by three light modulation means, and these light beams are deflected by a common optical deflector so that a common scanning connection is obtained. Although it has been practiced to write a color image by forming it as a light spot on a color photographic paper by an image optical system, when using an “expensive imaging system that does not correct chromatic aberration” as a scanning imaging optical system, When the beam shaping is not performed, the spot diameter of each color light spot needs to be adjusted in consideration of the chromatic aberration of the scanning imaging optical system.

  Further, there is a new demand for switching the writing density in the optical scanning device and adjusting the light spot diameter according to the switched writing density.

  It is an object of the present invention to enable a light spot having a desired spot diameter to be formed on a surface to be scanned in an optical scanning device that does not perform beam shaping by an aperture.

The optical scanning device according to the present invention individually modulates the intensity of n light beams emitted from n (≧ 1) light sources according to image signals by n modulation means, respectively. The light beam is deflected by a single rotating polygon mirror , and each deflected light beam is condensed on the surface to be scanned by the fθ lens to form n light spots, and the surface to be scanned is optically scanned at a constant speed. the optical writing a n optical scanning device which performs without the beam shaping by aperture for the light flux from the light source "has n number of the collimating lens system, the n-number of the focal length changing means.

  The “n collimating lens systems” are arranged between the n light sources and the optical deflectors so as to correspond to the light sources in a 1: 1 ratio, and convert the “divergent light beam from the light source side” into a parallel light beam. . In the case of n ≧ 2, each of the n collimating lens systems individually converts a divergent light beam from a corresponding light source into a parallel light beam.

The “n collimating lens systems” are arranged between the n light sources and the rotating polygon mirror so as to correspond to the light sources in a ratio of 1: 1, and convert a divergent light beam from the light source side into a parallel light beam.
The “n focal length variable means” corresponds to the n collimating lens systems in a 1: 1 ratio, and changes the focal length of the corresponding collimating lens system.

The optical scanning apparatus according to claim 1, wherein the individual of n collimator lens system and a "variable focus lens system consisting of two or more lenses", the focal length changing means "variable-focus lens system of the lens position and / or It is possible to adopt a configuration which is “means for changing the interval between the constituent lenses”.

As a reference technology , the collimating lens system has “a plurality of types of collimating lenses with different focal lengths”, and the focal length changing means is “a desired one of the plurality of types of collimating lenses is disposed at a predetermined use position. A configuration that is “means for causing” is also conceivable .

Similarly, as a reference technique, if the collimated lens system collimated light beam is deflected by an optical deflector as it is and condensed as a light spot on the scanned surface by the scanning imaging optical system, the collimating lens system It is possible to change or switch the spot diameter by changing or switching the focal length.

  In such a case, the so-called "face tilt" of the optical deflector becomes a problem, but as a light deflector, a "rotating polygon mirror that corrects the face tilt well" or "rotating single face that does not cause the face tilt in principle. By using a “mirror or galvanometer mirror”, the problem of falling down can be avoided.

As another reference example, one or more types of collimating lenses that can be switched to each other are designated as “variable focal length”, and the focal length is switched by switching (exchange) the collimating lens, and the focal point is changed by changing the focal length of the collimating lens. It is conceivable to adjust the distance.

The optical scanning device according to the first and second aspects of the present invention may be configured such that a light beam converted into a parallel light beam by n collimating lens systems is focused in the sub-scanning direction, and is a line long in the main scanning direction in the vicinity of the deflection reflection surface of the optical deflector. N cylindrical lens systems that form an image ”, and the n cylindrical lens systems correspond to the n collimating lens systems in a 1: 1 ratio.

The n cylindrical lens systems have a configuration in which the focal length of the corresponding cylindrical lens system is changed by “n second focal length variable means” .

Each of the cylindrical lens systems is a “variable focal cylindrical lens system including two or more cylindrical lenses” , and the n second focal length variable means are “lens positions and / or constituent lenses of the variable focal cylindrical lens system”. Means for varying the interval .

  By using the n cylindrical lens systems, the “surface tilt” in the optical deflector can be corrected, and an inexpensive rotating polygonal mirror can be used as the optical deflector.

In the optical scanning device according to the first aspect , since the cylindrical lens system has a variable focal length , the focal length in the sub-scanning direction: F of the cylindrical lens system is adjusted or changed, or the image is formed near the deflecting reflecting surface. The main scanning direction of the light spot focused on the surface to be scanned can be adjusted by changing the "width in the sub-scanning direction (the length of the object in the sub-scanning direction in the scanning imaging optical system)" Can be adjusted independently by changing the focal length f of the collimating lens system and the spot diameter in the sub-scanning direction by changing the focal length F of the cylindrical lens system.

  Therefore, by adjusting the focal length f in the collimating lens system and the focal length (focal length in the sub-scanning direction) F of the cylindrical lens system, the spot diameter of the light spot is independent in the main scanning direction and the sub-scanning direction. Can be adjusted.

In the optical scanning device according to claim 1 or 2 , the n light sources may be "semiconductor lasers" ( Claim 3 ), and the n light sources are laser light sources (gas laser or solid-state laser). The laser light emitted from the n laser light sources is condensed on the modulation unit of the n AO modulation elements, and the divergent light beam modulated by the n AO modulation elements is expressed as “the divergent light beam from the light source side”. ”Can also be configured to be incident on n collimating lens systems ( claim 4 ). When the light source is a semiconductor laser, the “semiconductor laser driving means” constitutes the modulation means.

The optical scanning device according to any one of claims 1 to 4 , wherein n ≧ 2, and the light emission wavelengths of the n light sources are different from each other ( claim 5 ). In this case, the number of light sources: n can be set to 3, and these three light sources can be set to “emits red, green, and blue laser light” ( claim 6 ). The optical scanning device according to the sixth aspect may be one that "scans light using a color photographic paper as an actual surface to be scanned" ( claim 8 ).

As described above, the optical deflector is a rotary polygon mirror, and the deflected light beam is condensed on the surface to be scanned by the fθ lens .

In addition, the optical scanning device according to any one of claims 1 to 7 may be configured as a well-known “tandem type image forming apparatus” using a plurality of them. In this case, by adjusting the spot diameter of the light spot in each optical scanning device, the spot diameter of the light spot on the corresponding photoconductive photosensitive member can be easily “equal to each other”.

  In the above description, the light scanning device of the present invention can be a “multi-beam scanning optical scanning device” by reading that one light source emits two or more light beams.

As described above, according to the optical scanning device of the present invention, the spot diameter of the light spot on the surface to be scanned can be easily adjusted . Further, since the beam shaping by the aperture is not performed, the light use efficiency is high and high-speed optical scanning can be realized.

FIG. 1 shows only one characteristic part of an embodiment of the invention.
In FIG. 1, reference numeral 1 denotes a semiconductor laser as a light source. Reference numeral 3 denotes a collimating lens system, reference numeral 5 denotes a cylindrical lens system, and reference numeral 7 denotes a rotating polygon mirror as an optical deflector.

  That is, FIG. 1 shows that one light beam emitted from n (= 1) light sources 1 is individually converted in accordance with an image signal by one modulation means (“semiconductor laser driving means” not shown). The intensity-modulated light beams are deflected by a single optical deflector 7, and the deflected light beams are condensed on a surface to be scanned (not shown) by a scanning imaging optical system (not shown). In the optical scanning apparatus in which one light spot is formed and optical writing for optically scanning the surface to be scanned at a constant speed is performed without performing “beam shaping by aperture” on the light flux from the light source 1. The part between the light source 1 and the optical deflector 7 "is shown.

  1A shows the sub-scanning direction as the vertical direction, and FIG. 1B shows the main scanning direction as the vertical direction.

  The collimating lens system 3 receives a “divergent light beam” from the side of the semiconductor laser 1 that is a light source, and converts the light beam into a parallel light beam. The collimating lens system 3 is a “variable focal length lens” composed of two lenses 3a and 3b that can be displaced in conjunction with the optical axis direction. The focal length varying means 3A includes the lens positions of the lenses 3a and 3b and / or By changing the distance between the lenses 3a and 3b (in the optical axis direction), the focal length is changed while maintaining the collimating function.

  Therefore, by changing the focal length of the collimator lens system 3, the “light beam diameter of the collimated parallel light beam” can be changed. The change in beam diameter can be a continuous change or a step change.

  The light beam emitted from the semiconductor laser has a different divergence angle between the direction parallel to the resonance surface and the direction orthogonal thereto. In this example, the light source 1 is arranged with the resonance surface parallel to the main scanning direction. For this reason, the light beam diameter of the light beam converted into a parallel light beam by the collimating lens system 3 is large in the sub-scanning direction and small in the main scanning direction.

  The parallel light flux is incident on the cylindrical lens system 5. The cylindrical lens system 5 has a positive refractive power only in the sub-scanning direction and does not have a refractive power in the main scanning direction. For this reason, the light beam that has passed through the cylindrical lens system 5 is focused in the sub-scanning direction as shown in FIG. 1A, and is condensed near the deflection reflection surface of the rotary polygon mirror 7 that is an optical deflector. In the main scanning direction, as shown in FIG. 1B, the cylindrical lens 5 is not affected.

  Therefore, the light beam that has passed through the cylindrical lens system 5 is imaged as a “line image long in the main scanning direction” in the vicinity of the deflection reflection surface of the rotary polygon mirror 7. Then, the light is deflected by the rotation of the rotary polygon mirror 7 and is condensed as a light spot on a scanning surface (not shown) by a scanning imaging optical system (not shown) to perform optical scanning of the scanning surface.

  In this way, by changing the focal length of the collimating lens system 3 while maintaining the collimating function, it is possible to change the beam diameter of the light beam obtained by converting the light beam from the light source 1 into a parallel beam. Since the cylindrical lens system 5 does not have refractive power in the main scanning direction, the “spot diameter in the main scanning direction” of the light spot formed on the surface to be scanned changes when the beam diameter of the parallel light beam is changed.

  Therefore, the spot diameter of the light spot in the main scanning direction can be adjusted by adjusting the focal length of the collimating lens system 3.

  The cylindrical lens system 5 includes two cylindrical lenses 5a and 5b. These cylindrical lenses 5a and 5b are displaced in conjunction with the optical axis direction. The second focal length changing unit 5A is configured to change the focal length in the sub-scanning direction by adjusting the “position and interval in the optical axis direction” of the cylindrical lenses 5a and 5b. The “focal length in the main scanning direction” of the cylindrical lens system 5 is infinite, and this does not change due to the displacement of the cylindrical lenses 5a and 5b.

  By changing the focal length of the cylindrical lens system 5 in the sub-scanning direction, the “width in the sub-scanning direction” of the “line image long in the main scanning direction” that forms an image in the vicinity of the deflecting reflection surface of the rotary polygon mirror 7 (Thickness) "can be changed. This line image is an object point in the image formation in the sub-scanning direction by the scanning image-forming optical system, and the corresponding image point is a light spot. Therefore, by adjusting the focal length of the cylindrical lens system 5 in the sub-scanning direction. The spot diameter in the sub-scanning direction of the light spot can be adjusted by adjusting the thickness of the line image.

  As is well known, the divergence angle of a divergent light beam emitted from a semiconductor laser varies among individual semiconductor lasers, and the focal lengths of the collimating lens system 3 and the cylindrical lens system 5 when beam shaping by an aperture is not performed. Is fixed, the spot diameter of the light spot varies depending on the variation in the divergence angle. However, in the optical scanning device of the present invention, the light spot is not limited regardless of the “variation in the divergence angle”. The spot diameter can be adjusted to a desired value or a predetermined value.

  In the case of “switching the writing density” in the optical scanning device, the light spot diameter can be adjusted in accordance with the switching writing density.

  When the focal length of the cylindrical lens system 5 is set to “fixed focal length”, the collimating lens system 3 adjusts the beam diameter of the parallel beam and “adjusts the spot diameter in the main scanning direction to a desired value”. Since the spot diameter in the scanning direction also varies, the spot diameter in the sub-scanning direction cannot be adjusted to a desired value, but the spot diameter in the main scanning direction is “the length of the pixel signal for writing one dot”. Since it can also be adjusted electrically, it is possible to use a cylindrical lens system 5 having a fixed focal length.

  As the focal length varying means 3A and the second focal length varying means 5A for changing the focal length in the collimating lens system 3 and the cylindrical lens system 5, a mechanism using a cam conventionally known as a zooming mechanism of a zoom lens, etc. A known appropriate mechanism can be used, and the change / switching of the focal length may be performed manually or electrically by computer control or the like.

  Instead of the light source 1 in the form shown in FIG. 1, a light source is a laser light source, and laser light emitted from the laser light source is condensed on a modulation unit of the AO modulation element, and a divergent light beam modulated by the AO modulation element It will be readily understood that the configuration can be configured such that the light is incident on the collimating lens system. In this case, “the divergent light beam modulated by the AO modulation element” is “the divergent light beam from the light source side”. Needless to say, the collimating lens system or the cylindrical lens system may be composed of three or more lenses.

  The optical scanning device of FIG. 2 is a device that performs color image writing by performing optical scanning on a “color photographic paper” (not shown) 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, 1B passes through the corresponding modulation means 2R, 2G, 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. A “modulated light beam” that is condensed to about 1 mm and passes through the modulation means 2R, 2G, and 2B becomes a “divergent light beam from the light source side”.

  The modulated light beams are divergent light beams from the light source side and incident on the collimating lens systems 3R, 3G, and 3B to be converted into parallel light beams, and then the optical path is bent by the mirrors 4R, 4G, and 4B, and the cylindrical lens system The light is condensed in the sub-scanning direction by 5R, 5G, and 5B, is synthesized as “one beam” by the optical path synthesis element 6 having a dichroic film, and is incident on the deflection reflection surface of the rotary polygon mirror 7 as an optical deflector.

  When the rotating polygon mirror 7 rotates at a constant speed, the combined light beam is deflected at a uniform angular velocity, and is transmitted through the lenses 8, 9, and 10 constituting the “fθ lens” that is a scanning imaging optical system, and is not shown. A light spot is formed on the surface to be scanned (substantially “color photographic paper”), and optical scanning is performed by scanning the scanning line 11 at a constant speed. The color photographic paper is conveyed at a constant speed in the sub-scanning direction orthogonal to the scanning line 11, and along with this conveyance, the main scanning is repeated in the sub-scanning direction and a two-dimensional color image is written.

  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, the start of optical writing by the light spot is synchronized, and the optical writing start position is aligned.

  As described above, each color laser beam emitted from the light sources 1R, 1G, and 1B is condensed to a light beam diameter of about 0.1 mm toward the modulation unit of the corresponding modulation unit 2R, 2G, and 2B, and the modulation unit 2R, The “modulated light beam” that has passed through 2G and 2B becomes a “divergent light beam from the light source side”, but when the laser light beam is condensed toward the modulation unit, there is “variation in the condensing state”, Due to this variation, there is also variation in the divergence angle of the divergent light beam from the light source side.

  Further, in this optical scanning device, the deflected laser beams of each color are condensed on the surface to be scanned by the common scanning imaging optical systems 8, 9, and 10, so that the influence of chromatic aberration of the scanning imaging optical system is taken into consideration. There is a necessity (spot diameter, that is, “beam waist diameter” is proportional to the wavelength), and in order to make the spot diameter of each color light spot of R, G, and B uniform, the dispersion of the divergence angle and the scanning imaging optics In consideration of the chromatic aberration of the system, adjustment for each color laser beam is required.

  The collimating lens systems 3R, 3G, and 3B are the same as the collimating lens system 3 described with reference to FIG. 1, and the focal length is changed while maintaining the collimating function by a “focal length varying unit” (not shown). The cylindrical lens systems 5R, 5G, and 5B are the same as the cylindrical lens system 5 described with reference to FIG. 1, and the focal length in the sub-scanning direction is not shown by a “second focal length varying unit” (not shown). Can be changed.

  Therefore, by adjusting the focal lengths of the collimating lens systems 3R, 3G, and 3B, the spot diameters of the R, G, and B color light spots can be adjusted in the main scanning direction, and the cylindrical lens diameters 5R, 5G, and 5B are focused in the sub-scanning direction. By adjusting the distance, the spot diameters of the R, G, B color light spots on the surface to be scanned can be adjusted regardless of the "variation of the divergence angle of the divergent light beam and the influence of chromatic aberration of the scanning imaging optical system". It can be set to a desired value.

That is, the optical scanning device shown in FIG. 2 responds to image signals by three light beams emitted from n (= 3) light sources 1R, 1G, and 1B by three modulation means 2R, 2G, and 2B, respectively. Each of the intensity-modulated light beams is deflected by a single optical deflector 7, and the deflected light beams are collected on a scanned surface 11 by scanning imaging optical systems 8, 9, 10. Light writing is performed to form three light spots and optical scanning is performed on the surface to be scanned at a constant speed without performing beam shaping by apertures on the light beams from the two light sources 1R, 1G, and 1B. Three collimating lenses, which are arranged to correspond to a light source and 1: 1 between three light sources and an optical deflector and convert a divergent light beam from the light source side into a parallel light beam. The system 3R, 3G, 3B and the three collimating lens systems can be made 1: 1. Have corresponding changes the focal length of the collimating lens system and / or switches the three focal length changing means (not shown).

The collimating lens systems 3R, 3G, and 3B are variable focus lens systems composed of two or more lenses, and the focal length variable means changes the lens position and / or the interval between the constituent lenses of the variable focus lens system. The beams collimated by the three collimating lens systems 3R, 3G, and 3B are converged in the sub-scanning direction, and formed as a line image in the vicinity of the deflecting reflection surface of the optical deflector 7 in the main scanning direction. has three cylindrical lens optics 5R, 5G, 5B which causes, not shown three cylindrical lens optics 5R, 5G, three second focal length changing means for changing the focal length of 5B (Figure 2 ) has a.

Each of the cylindrical lens systems 5R, 5G, and 5B is a variable focus cylindrical lens system composed of two cylindrical lenses as shown in FIG. 1, and each second focal length varying means includes each variable focus cylindrical lens system. This is a means for varying the lens position and the interval between the constituent lenses.

The three light sources 1R, 1G, and 1B are laser light sources, and the laser light emitted from these light sources is condensed on the modulation sections of the three AO modulation elements 1R, 1G, and 1B and modulated by the three AO modulation elements. The divergent luminous flux is incident on the three collimating lens systems 3R, 3G and 3B, the light sources 1R, 1G and 1B have different emission wavelengths, and the light sources 1R, 1G and 1B are red, green and blue laser beams. Is radiated .

Further, the optical scanning device of Figure 2 in which "performs optical scanning color photographic paper as substantive scanned surface", the optical deflector at the rotary polygon mirror 7, the scanning image forming optical system 8, 9, 10 is the fθ lens.

An embodiment of the reference technique will be described with reference to FIG .
As in FIG. 1, reference numeral 1 denotes a semiconductor laser as a “light source”, and reference numeral 7 denotes a rotating polygon mirror as an “optical deflector”.
In this embodiment, the collimating lens system 30 includes two types of collimating lenses 31 and 32 having different focal lengths, and the focal length changing means 30A selects a predetermined one of the collimating lenses 31 and 32 as “predetermined”. a means to arrange the "use position (the position of the light beam divergent from the light source side can collimation) of.

The cylindrical lens system 50 includes two types of cylindrical lenses 51 and 52 having different focal lengths, and the second focal length changing unit 50A selects a predetermined one of the two types of cylindrical lenses 51 and 52 as “predetermined”. use position (the collimated light beam to the deflecting reflective surface position of the rotary polygon mirror 7, the position that can be imaged as a linear image extending in a main scanning direction) of a means for disposed. " Light source 1 is a semiconductor laser.

  Since the collimating lenses 31 and 32 and the cylindrical lenses 51 and 52 have different focal lengths, for example, as shown in FIG. 3A, the collimating lens 31 and the cylindrical lens 52 are retracted from the imaging optical axis. The collimating lens 32 and the cylindrical lens 51 are combined, or the collimating lens 32 and the cylindrical lens 51 are retracted from the imaging optical axis as shown in FIG. The spot diameter of the light spot can be switched independently between the main scanning direction and the sub-scanning direction by changing the “combination of the collimating lens and the cylindrical lens”.

  By further increasing the number of collimating lenses constituting the collimating lens system and the number of cylindrical lenses constituting the cylindrical lens system, the number of types of switching can be increased appropriately.

FIG. 4 shows another embodiment of the optical scanning device according to the reference technique . In order to avoid complications, the same reference numerals as those in FIG. This optical scanning device is also a device that performs color image writing by performing optical scanning on a “color photographic paper” (not shown) with three light beams of red (R), green (G), and blue (B).

  Each color laser beam emitted from the light sources 1R, 1G, and 1B passes through the corresponding modulation means 2R, 2G, and 2B (AO modulation elements), and is modulated in accordance with the image signal. What is subjected to optical scanning is a “light beam diffracted according to an image signal (modulated light beam)”. Each laser beam is condensed to a modulation part of the modulation means 2R, 2G, 2B to a beam diameter of about 0.1 mm, and the modulated beam becomes a “divergent beam from the light source side”.

  Each of the modulated light beams is converted into a parallel light beam by the collimating lens systems 30R, 30G, and 30B as "divergent light beams from the light source side", and then the optical path is bent by the mirrors 4R, 4G, and 4B to have a dichroic film It is synthesized as “one beam” by the optical path synthesis element 6 and enters the deflection reflection surface of the oscillating mirror 70 as an optical deflector.

  When the oscillating mirror 70 is oscillated, the combined light beam is deflected sinusoidally and transmitted through the lenses 8A, 9A, and 10A constituting the scanning imaging optical system, and the surface to be scanned (substantially not shown) A light spot is formed on the “color printing paper.” Optical scanning is performed by scanning the scanning line 11 at a constant speed. The color photographic paper is conveyed at a constant speed in the sub-scanning direction orthogonal to the scanning line 11, and along with this conveyance, the main scanning is repeated in the sub-scanning direction and a two-dimensional color image is written.

  The scanning imaging optical system constituted by the lenses 8A, 9A, and 10A has its constant velocity corrected so that “the light spot by each deflected light beam deflected sinusoidally moves on the surface to be scanned”. ing.

  The light beam deflected by the rotary polygon mirror 7 and traveling toward the optical scanning start position is reflected by the mirror 12 and incident on the photodetector 13 when it passes through the lenses 8A and 9A. Based on the detection signal of the photodetector 13, the start of optical writing by the light spot is synchronized, and the optical writing start position is aligned.

  The collimating lens systems 30R, 30G, and 30B are the same as the collimating lens system 30 described with reference to FIG. 3, and the focal length can be switched while maintaining the collimating function by a “focal length varying unit” (not shown). it can. Therefore, the spot diameters of the R, G, and B color light spots can be adjusted by adjusting the focal lengths of the collimating lens systems 30R, 30G, and 30B.

  In the embodiment shown in FIG. 4, since there is no cylindrical lens system in the embodiment shown in FIG. 2, an oscillating mirror 70 without surface tilt is used as an optical deflector. Of course, a “rotating polygon mirror with sufficiently high surface accuracy and substantially no surface tilt” can be used as an optical deflector, and “a long lens for correcting surface tilt” in a scanning imaging optical system. Ordinary rotating polygonal mirrors may be used.

  Further, in place of the collimating lens systems 30R, 30G, and 30B, the collimating lenses 3R, 3G, and 3B described with reference to FIG. 2 may be used. In this case, each light spot diameter is continuously changed. be able to. Conversely, the collimating lens system and the cylindrical lens system in the optical scanning apparatus shown in FIG. 2 can be used as shown in FIG.

  Above, “divergent light beam emitted from the semiconductor laser” as a “divergent light beam from the light source side” and “divergent light beam emitted from the laser light source and condensed on the modulation part of the AO modulation element and modulated. The case of the "sexual flux" is shown. In addition to these, “a divergent light beam emitted from a semiconductor laser is condensed on a modulation unit of an AO modulation element via a collimator lens and a condensing lens, and the divergent light beam after modulation is relay lens The beam may be converted into a parallel light beam.

  In this case, the relay lens can be a “variable focal length collimating lens system”, and the collimating lens can be a “focal length variable collimating lens system”.

It is a figure for demonstrating the characteristic part of 1st Embodiment of an optical scanning device. It is a figure for demonstrating one Embodiment of an optical scanning device. It is a figure for demonstrating embodiment of the optical scanning device concerning a reference technique. It is a figure for demonstrating embodiment of the optical scanning device concerning a reference technique .

Explanation of symbols

1 Light source 3 Collimating lens system with variable focal length 5 Cylindrical lens system with variable focal length in the sub-scanning direction 7 Optical deflector (rotating polygon mirror)

Claims (7)

The n light beams emitted from n (≧ 1) light sources are individually intensity-modulated by n modulation means according to the image signals, and the intensity-modulated light beams are converted into a single rotating polygon mirror. The n light spots are formed by condensing the deflected light beams by the fθ lens to form n light spots, and optically scanning the scanned surface at a constant speed. In the optical scanning device that performs the beam shaping from the light source without performing the beam shaping by the aperture,
n collimating lens systems arranged between the n light sources and the rotating polygon mirror so as to correspond to the light sources in a ratio of 1: 1, and collimate the divergent light beam from the light source side;
N number of focal length variable means for changing the focal length of the corresponding collimating lens system while maintaining the collimating function ;
Further, the n cylindrical lenses that focus the light beams converted into parallel light beams by the n number of collimating lens systems in the sub-scanning direction and form a long line image in the main scanning direction in the vicinity of the deflection reflection surface of the optical deflector. The system,
N second focal length variable means for changing the focal length of the n cylindrical lens systems;
Each of the n cylindrical lens diameters is a variable focus cylindrical lens system including two or more cylindrical lenses,
Each of the n second focal length changing means is means for changing the lens position of the variable focus cylindrical lens system and / or the interval between the constituent lenses . The optical scanning device according to claim 1,
Individual n pieces of the collimating lens system, a variable focus lens system consisting of two or more lenses,
An optical scanning device characterized in that the focal length changing means is a means for changing the lens position and / or the interval between the constituent lenses of the variable focus lens system. The optical scanning device according to claim 1 or 2,
An optical scanning device characterized in that the n light sources are semiconductor lasers . The optical scanning device according to any one of claims 1 to 3,
The n light sources are laser light sources, the laser light emitted from the light sources is condensed on the modulation units of the n AO modulation elements, and the divergent light beam modulated by the n AO modulation elements is n An optical scanning device characterized by being incident on a single collimating lens system . The optical scanning device according to any one of claims 1 to 4,
An optical scanning device in which n ≧ 2 and n light sources have different emission wavelengths . The optical scanning device according to claim 5.
The number of light sources: n is 3, and these three light sources emit red, green and blue laser beams . The optical scanning device according to claim 6.
An optical scanning apparatus characterized in that color scanning is performed using a color photographic paper as an actual surface to be scanned .

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