JP5962267B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus.

  Image forming apparatuses that perform image writing by optical scanning are known as analog or digital electronic copying apparatuses, optical printers, facsimile apparatuses, plotter apparatuses, and the like.

  An MFP (multifunction printer) having the functions of these apparatuses in combination is also known as an image forming apparatus.

  Conventionally, in such an image forming apparatus, synchronization detection is performed in order to make the image writing position by optical scanning constant.

  That is, in general, a synchronization detection sensor that detects a deflected laser beam is installed “outside the image writing area” on the image writing start side, and receives the deflected laser beam that is deflected toward the image writing start unit.

  Then, a synchronization detection signal is generated by the synchronization detection sensor, and the lighting timing at the start of writing of the light source (generally LD) is defined based on the generated synchronization detection signal.

  Recently, image forming apparatuses are required to be reduced in size and cost, and optical scanning apparatuses are also required to be reduced in size and cost.

  The above-described synchronization detection method requires a space for installing a synchronization detection sensor and a space for arranging a light guide optical system that guides a deflected laser beam to the sensor, which becomes an obstacle to downsizing.

  Further, the cost separately generated in the synchronization detection sensor and the “light guide optical system” becomes an impediment to cost reduction.

  In view of such a situation, it is known that a laser beam reflected by a deflecting reflection surface is received by a laser oscillation unit, which is a light emitting unit of a light source, and used as a synchronization detection signal (Patent Document 1).

  In addition, it is known that a laser beam reflected by a deflecting reflection surface is received by a light receiving means provided close to a laser oscillation part of a semiconductor laser and used as a synchronization detection signal (Patent Document 2).

  In this case, since the light source and the synchronization detection signal generator are the same or are “closely close to each other”, a “dedicated light guide optical system” for guiding the deflected laser beam to the light receiving means is not required.

  Polygon mirrors and vibrating mirrors are well known as optical deflectors, but these optical deflectors inevitably have so-called “face tilt” and “axis tilt”.

  The surface tilt or the axis tilt causes an error in the “direction in the sub-scanning direction” of the deflected laser beam toward the light receiving unit, and causes a decrease in detection accuracy by the light receiving unit.

  Such a problem also occurs in the synchronization detection methods disclosed in Patent Documents 1 and 2.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to realize an optical scanning device capable of improving synchronization detection accuracy while being able to be reduced in size and cost.

  Another object is to realize an image forming apparatus using such an optical scanning device.

Optical scanning apparatus of the present invention, the light emitting portion and a semiconductor laser light source and a light detection unit disposed in the vicinity of the light emitting portion, a light deflector for deflecting and scanning by reflecting a laser beam from the light emitting portion When the laser beam divergent from the light emitting unit, a focusing optical system for guiding to the deflecting reflective surface of the optical deflector, the deflected laser light beam is deflected by the optical deflector, on a surface to be scanned comprising a scanning optical system for forming a light spot and guiding, and detects the laser beam reflected by the deflecting reflective surface by said light detection unit, an optical scanning device to obtain a synchronization detection signal of the optical scanning, is reflected by the light deflector, the laser beam toward the semiconductor laser light source via the light condensing optical system forms an image in the sub-scanning direction in the vicinity of the light receiving portion of the light sensing unit, or a divergent in the sub scanning direction be incident on the light receiving unit focused while As such, the optical arrangement from a semiconductor laser light source to said optical deflector is configured having an aperture to the beam shaping by the opening a light beam toward the optical deflector from the light emitting portion is reflected by the deflecting reflective surface When the reflected light beam passes through the opening, the width of the reflected light beam is smaller than the width of the opening in at least one of the main scanning direction and the sub-scanning direction .

In the optical scanning device according to the present invention, as described above, synchronization detection is performed by the light detection unit in the vicinity of the light emitting unit of the semiconductor laser light source, so that the optical scanning device can be easily reduced in size and cost.
The laser beam reflected by the deflecting reflection surface enters the light receiving unit of the light detection unit while diverging or converging through the condensing optical system.
That is, since the light receiving portion of the light detection portion has a “light flux width”, even if the direction of the incident laser light flux fluctuates in the sub-scanning direction, the laser light flux can be reliably received, and the synchronization detection accuracy is improved.

  Therefore, an image forming apparatus using such an optical scanning device can form a good image by correctly aligning image writing positions by optical scanning.

It is a figure explaining the part of the semiconductor laser light source in 1st Embodiment of invention. It is a figure for demonstrating the outline of an optical scanning device. It is a figure explaining the part of the semiconductor laser light source in another embodiment of invention. It is a figure explaining the part of the semiconductor laser light source in other embodiment of invention. It is a figure for demonstrating the characterizing part of invention. It is a figure for demonstrating the characterizing part of invention. It is a figure for demonstrating the characterizing part of invention. It is a figure for demonstrating one example of embodiment using an aperture. It is a figure for demonstrating another example of embodiment using an aperture. It is a figure for demonstrating embodiment using an aperture. It is a figure for demonstrating one example of embodiment using an aperture. It is a figure for demonstrating the relationship between the return light beam and the optical detection part in an Example. It is a figure for demonstrating the relationship between a return light beam and a photon detection part. It is a figure which shows one Embodiment of an optical scanning device. 1 is a diagram illustrating an embodiment of an image forming apparatus.

Hereinafter, embodiments will be described.
Various types of optical scanning devices have been proposed in the past, and since the outline is widely known, the outline of the optical scanning will be described below with reference to FIG.
FIG. 2 shows an embodiment of an optical scanning device for carrying out the present invention.
In FIG. 2, reference numeral 10 denotes a “semiconductor laser light source”, reference numeral 20 denotes a “condensing optical system”, reference numeral 30 denotes an “optical deflector”, reference numeral 40 denotes a “scanning optical system”, and reference numeral 50 denotes a “scanned surface”. , Respectively.

Although the semiconductor laser light source 10 will be described in detail later, a “divergent laser beam” is emitted from the light emitting portion of the semiconductor laser light source 10 like a circumferential pair.
This divergent laser beam is converted into a focused beam by the condensing optical system 20 and is incident on the deflection reflection surface of the optical deflector 30.
In this example, the optical deflector 30 is a “polygon mirror” having four deflecting and reflecting surfaces, and rotates at a constant speed in a predetermined direction, for example, clockwise when optical scanning is performed.

  The laser beam incident on the deflecting / reflecting surface is reflected by the deflecting / reflecting surface and is deflected at a constant angular velocity as the polygon mirror 30 rotates at a constant speed.

  The deflected laser beam to be deflected enters the scanning optical system 40 and is guided by the scanning optical system 40 onto the scanned surface 50 to form a light spot.

  The surface to be scanned 50 is scanned in the main scanning direction by the light spot, and the main scanning is repeated in the sub scanning direction by moving the surface to be scanned 50 at a constant speed in the sub scanning direction.

  The “main scanning direction” is the “vertical direction” in FIG. 2 on the scanned surface 50 and the “direction corresponding to the vertical direction on the optical path from the semiconductor laser light source 10 to the scanned surface 50”.

  The “sub scanning direction” is a direction orthogonal to the main scanning direction on the optical path from the semiconductor laser light source 10 to the scanned surface 50.

In this way, an image is written. The actual surface to be scanned 50 is a photoconductive surface of a photoconductive photoconductor, and is uniformly charged when optically scanned.
By the image writing by the optical scanning, an “electrostatic latent image corresponding to the written image” is formed on the photosensitive member.

  This electrostatic latent image is developed and visualized as a toner image. The obtained toner image is transferred to a sheet-like recording medium such as transfer paper and fixed on the medium.

In this way, image formation is executed.
A few supplements.
The condensing optical system 20 is normally an “anamorphic” optical system having different positive refractive powers in the main scanning direction and the sub-scanning direction.
In general, in order to correct “surface tilt” of the polygon mirror 30, the laser beam is formed as a “line image long in the main scanning direction” at a position near the deflecting reflection surface.

  In response to this, the scanning optical system 40 is also an “anamorphic optical system”, and the imaging position of the line image and the position of the surface to be scanned have a “conjugate relationship with respect to the sub-scanning direction”.

The scanning optical system 40 also has an “fθ characteristic” which is a function for equalizing the speed of light scanning (main scanning) using a light spot.
The condensing optical system 20 shown in FIG. 2 may be composed of one lens or may be composed of two or more lenses.

  The scanning optical system 40 is also composed of “one or a plurality of lenses”. Further, in order to bend the optical path of the laser beam, an “optical path bending mirror” (not shown) is appropriately used.

A “vibrating mirror” may be used instead of the polygon mirror 30 for the optical deflector. When the vibrating mirror is used, the characteristic of the scanning optical system is “f · sin ⁻¹ θ characteristic”.

In the optical scanning device shown in FIG. 2, the present invention is used for the following points.
That is, when the emitted light beam L1 from the semiconductor laser light source 10 is reflected by the deflection reflection surface of the optical deflector 30 and returns to the semiconductor laser light source 10, this is detected as a return light beam L2.

  The above is the outline of the optical scanning device.

  Hereinafter, specific embodiments will be described.

  1, 3, and 4 show three examples of semiconductor laser light source configurations. In order to avoid complications, common symbols are used in each figure for those that are not likely to be confused.

  A semiconductor laser light source 10A shown in FIG. 1 forms a “closed space” by a plate PT on which lead pins LP are disposed, a can package CP, and a cover glass CG.

In this closed space, a support SP is fixedly provided, and a support substrate SB having a light emitting portion LS and a photodiode PD is provided on the support SP.
The light emitting unit LS is a “laser oscillation unit”.
The lead pin LP is connected to light source control means (electronic board) (not shown).

When the light emitting unit LS emits light, a divergent laser light beam is emitted as an emitted light beam L1 in the positive direction of the X direction, and is transmitted through the cover glass CG and emitted.
The photodiode PD is a “light detection unit” in this embodiment.
In this embodiment, the photodiode PD receives a so-called “backlight” emitted in the negative X direction from the light emitting unit LS, and provides automatic control of the intensity of the laser beam.

  In other words, the semiconductor laser light source 10A also has an auto power control (abbreviated as APC) function.

  In FIG. 1, the Z direction corresponds to the “sub-scanning direction”. When the “main scanning direction” is the Y direction, the Y direction is “a direction perpendicular to the drawing” in FIG.

  A “return beam” indicated by a symbol L2 in FIG. 1 is a “focused beam in the Z direction (sub-scanning direction)” as illustrated. The return light beam L2 is deflected in a direction orthogonal to the drawing.

  The return light beam L2 is condensed “behind the position of the photodiode PD (on the negative side in the X direction)” in the sub-scanning direction.

Accordingly, the returning light beam L2 “irradiates the whole light while focusing” on the light receiving portion of the photodiode PD which is the light detecting portion.
The photodiode PD detects the return light beam L2 irradiated in this way, and issues a synchronization detection signal.

  Since the return light beam L2 that irradiates the light detection unit PD irradiates the entire light receiving unit, even if the direction of the return light beam L2 is deviated due to a manufacturing error or a temporal error, a change in the detected light amount is suppressed to be small.

  For this reason, the “intensity fluctuation” of the synchronization detection signal generated by the photodiode PD is reduced, and deterioration in detection accuracy can be effectively prevented.

  Further, since the signal is stabilized, complicated signal detection processing is not necessary.

  In the embodiment shown in FIG. 3, the same reference numerals as those in FIG. 1 denote the same elements as in FIG. Reference numeral 10B denotes a semiconductor laser light source.

  In the embodiment shown in FIG. 3, the photodiode PD constituting the light detection unit is fixed to the plate PT via the support layer SP1, and the light receiving surface (light receiving unit) is orthogonal to the X direction.

  In FIG. 3, the return light beam L2 is focused on the semiconductor laser light source while being focused in the sub-scanning direction (Z direction), focused slightly on the front side of the cover glass CG, and irradiated to the light receiving portion of the photodiode PD while being diverged. .

  Therefore, also in this example, the return light beam L2 that irradiates the light detection unit PD irradiates the entire light receiving unit, so that the variation in the detected light amount can be suppressed to be small as in the embodiment of FIG.

  That is, “intensity fluctuation” of the synchronization detection signal emitted from the photodiode PD is reduced, and deterioration in detection accuracy can be effectively reduced.

  In the embodiment shown in FIG. 3, the diameter of the return beam L2 can be reduced at the position of the cover glass CG, so that the return beam L2 can be efficiently incident on the semiconductor laser light source 10B.

  That is, even if the direction of the return light beam L2 is deviated, the opening of the can package CP hardly shields the return light beam L2, and the deterioration of detection accuracy can be more effectively reduced.

  The embodiment shown in FIG. 4 is a modification of the embodiment shown in FIG. 1, and is an example in which the configuration shown in FIG. 1 is rotated 90 degrees around the X axis.

  In this case, the deflection direction of the return light beam L2 is the vertical direction in the figure (Y direction, that is, the main scanning direction).

  Also in this case, the above-described effect of “the“ intensity change ”of the synchronization detection signal generated by the photodiode PD can be reduced and deterioration in detection accuracy can be effectively prevented” is obtained.

Similarly, it goes without saying that the embodiment shown in FIG. 3 may be rotated by 90 degrees around the X axis.
In the embodiment shown in FIGS. 1 and 3, the angle at which the semiconductor laser light source is rotated around the X axis is not limited to 90 degrees, and can be set to an appropriate angle.

  A so-called multi-beam method is widely known as an example of the optical scanning device. In this case, an “LD array” is often used as a semiconductor laser light source.

  When using an LD array, the LD array is “tilted in the sub-scanning direction” in order to adjust the “interval in the sub-scanning direction” of a plurality of laser beams that simultaneously scan the surface to be scanned.

  In the case of the optical scanning device that tilts the LD array in this way, in the embodiment shown in FIGS. 1 and 3, the semiconductor laser light source using the LD array can be rotated around the X axis.

  By this rotation, it is possible to satisfactorily detect the return beam with respect to the laser beam from each light emitting unit in the LD array.

  Needless to say, the embodiment shown in FIGS. 3 and 4 also has an “auto power control (abbreviated as APC) function” as in the embodiment shown in FIG.

The “can package type semiconductor laser light source” is exemplified above, but the semiconductor laser light source is not limited to this, and a known “frame package type” can also be used.
When a polygon mirror is used as the optical deflector, a major cause of the “incident position shift” of the returned light beam to the photodiode is the “surface deflection of the deflecting reflection surface” as described above.

  As another cause of the “incident position shift”, “processing / assembly error” in the condensing optical system 20 can be considered.

In this case, adjusting the position and position of the condensing optical system in order to adjust the “incident position deviation of the returning light beam” deteriorates the “light spot diameter and scanning line bending”.
However, in the present invention, since the configuration is such that “the light beam diameter of the returning light beam spreads on the light receiving portion of the light detecting portion”, the above-mentioned problem due to the above “processing / assembly error in the condensing optical system” can be avoided.

  FIG. 5 shows a state of the emitted light beam L1 and the return light beam L2 between the semiconductor laser light source 10 and the deflecting / reflecting surface of the optical deflector (polygon mirror or vibrating mirror).

The upper diagram in FIG. 5 relates to the main scanning direction, and the lower diagram relates to the sub-scanning direction.
The condensing optical system 20 is an “anamorphic optical system”, and in the main scanning direction, as shown in the upper diagram of FIG. 5, an emitted light beam emitted as a divergent laser light beam is a “parallel light beam”.

  The outgoing light beam L1 (main), which is a parallel light beam in the main scanning direction, becomes a return light beam L2 (main) when reflected by the deflecting / reflecting surface 30A.

  The return light beam L2 (main) travels backward in the optical path of the emitted light beam L1 (main), and is condensed at the light emitting source position of the semiconductor laser light source 10 if the deflecting / reflecting surface 30A is not tilted.

  Regarding the main scanning direction, the emitted light beam L1 (main) may be converted into a “weakly divergent or weakly convergent” light beam by the condensing optical system 20.

  Even if the emitted light beam L1 (main) in the main scanning direction is weakly divergent or weakly converging, there is no problem as long as it does not affect the synchronization detection accuracy.

  The return light beam L2 (main) is condensed near the light emission position, and is incident on the light receiving portion of the light detection unit disposed in the vicinity thereof in a state where the light beam diameter is narrowed.

  For this reason, the light intensity when the light beam L2 (main) crosses the light receiving portion increases, and the synchronization signal can be generated with high accuracy.

  On the other hand, with respect to the sub-scanning direction, as shown in the lower diagram of FIG. 5, the condensing optical system 20 converts the emitted light beam L1 (sub) into a condensed light beam and collects it at a position slightly shifted from the deflection reflecting surface 30A. Light up.

  In the example of FIG. 5, the return light beam L2 (sub) reflected by the deflecting / reflecting surface 30A is incident on the semiconductor laser light source 10 while being focused in the sub scanning direction.

  In this case, the state of the return light beam L2 (sub) with respect to the semiconductor laser light source 10 is as shown in FIG.

  6 and 7 illustrate the relationship between the deflecting / reflecting surfaces 30A and 30B and the emitted light beam L1 (sub).

  In FIG. 6, the deflection reflection surface 30 </ b> A is a “polygon mirror deflection reflection surface”, and the deflection reflection surface 30 </ b> B in FIG. 7 is a “vibration mirror deflection reflection surface”.

  In FIG. 6, the deflecting / reflecting surface 30A is rotationally displaced as shown in the figure as the polygon mirror rotates.

  In FIG. 7, the deflecting / reflecting surface 30 </ b> B is oscillatingly displaced “around the oscillating shaft” with the oscillation of the oscillating mirror.

  6 and 7, the emitted light beam L1 (sub) is condensed slightly before (light source side) or behind the deflecting / reflecting surfaces 30A and 30B.

  This condensing point is indicated by reference numerals P1 and P2 in FIGS. These condensing points P1 and P2 are “conjugate points of the light emitting part of the semiconductor laser light source” with respect to the emitted light beam L1 (sub).

  When the outgoing light beam L1 (sub) condensed at the condensing point P1 is reflected by the deflecting / reflecting surfaces 30A and 30B, as shown in FIGS. 1 and 4, it is condensed by the photodiode rather than the light emitting portion.

  The emitted light beam L1 (sub) condensed at the condensing point P2 is condensed “before the light emitting portion” as in the case of FIG.

  Then, as described above, the return light beam L2 (sub) enters the light receiving portion of the light detecting portion "entering while diverging or converging in the sub scanning direction", thereby improving the accuracy of synchronization detection.

  That is, it is possible to avoid problems caused by the tilting of the deflecting / reflecting surface 30A, tilting of the swing axis of the deflecting / reflecting surface 30B, and “processing / assembly error in the condensing optical system”.

  By the way, in an optical scanning device, it is required to obtain both a light spot having a desired spot diameter on the surface to be scanned and a conjugate of the deflection reflection surface and the surface to be scanned.

  In the present invention, since the “condensing point in the sub-scanning direction” of the emitted light beam by the condensing optical system is deviated from the deflecting reflection surface, the balance of compatibility may be deteriorated.

  However, recent improvements in processing accuracy such as polygon mirrors and scanning optical systems are remarkable.

  For this reason, a slight deterioration in the balance of the compatibility is suppressed to an error that does not cause a problem on an image.

Even with the configuration of the present invention, there is no adverse effect on the optical scanning performance and image forming performance.
Alternatively, the beam waist position may be shifted by optimizing the surface tilt correction, and the “scanned surface and the deflecting reflection surface” may be shifted from the conjugate relationship by optimizing the beam waist position.

  In this manner, both characteristics can be set so as to be suppressed to an allowable error.

  By the way, in an optical scanning device, generally, an “aperture that performs beam shaping by an opening” is used between a light source and an optical deflector.

  In the case of the present invention, it is preferable that a part of the returning light beam is “not blocked by the aperture”.

With reference to FIG. 8 and subsequent figures, an embodiment with such a device will be described.
The reference numerals are shared in FIGS.

  In these drawings, reference numeral 10 denotes a semiconductor laser light source, reference numeral 20A denotes a coupling lens, reference numeral 20B denotes a cylindrical lens, and reference numeral AP denotes an aperture.

  Reference numeral 30A denotes a deflecting reflecting surface. The deflecting / reflecting surface 30A is assumed to be a deflecting / reflecting surface of a polygon mirror, but the present invention is not limited to this, and the description is the same for the deflecting / reflecting surface 30B of the vibrating mirror.

  The coupling lens 20A and the cylindrical lens 20B constitute a “condensing optical system”. The cylindrical lens 20B has “positive power only in the sub-scanning direction”.

8 and 9, “the vertical direction is the sub-scanning direction (Z direction)”.
The divergent emitted light beam L1 (sub) emitted from the semiconductor laser light source 10 is converted into a parallel light beam by the coupling lens 20A.

Then, the peripheral portion of the light beam is cut by the aperture AP to be shaped.
The beam-shaped emitted light beam L1 (sub) is condensed in the sub scanning direction by the cylindrical lens 20B.

  The condensing position of the emitted light beam L1 (sub) in the sub scanning direction is slightly behind the deflecting / reflecting surface 30A.

  The return light beam L2 (sub) reflected by the deflecting / reflecting surface 30A has a light beam diameter smaller than that of the aperture AP, as indicated by a broken line.

  Then, the light enters the coupling lens 20 </ b> A without being blocked by the aperture AP, is converted into a condensed light beam, and enters the semiconductor laser light source 10.

  At this time, as shown in FIG. 8, the return light beam L2 (sub) incident on the semiconductor laser light source 10 is in the process of focusing, and enters the light receiving portion of the light detection portion as a “return light beam having a light beam diameter”.

  Accordingly, it is possible to avoid problems caused by the surface tilt of the deflecting / reflecting surface 30A (the tilting axis of the deflecting / reflecting surface 30B) and the “processing / assembly error in the condensing optical system”.

Further, since there is no “loss of light quantity of the return light beam L2 (sub)” due to the aperture AP, there is no deterioration of the synchronization detection accuracy.
In the embodiment shown in FIG. 9, the divergent emitted light beam L1 (secondary) emitted from the semiconductor laser light source 10 is converted into a “weakly focused light beam” by the coupling lens 20A, shaped by the aperture AP, and the cylindrical lens. The light is condensed in the sub-scanning direction by 20B.

  The condensing position in the sub-scanning direction is slightly in front of the deflecting / reflecting surface 30A in the example of FIG.

  The return light beam L2 (sub) reflected by the deflecting / reflecting surface 30A is converted into a light beam condensed in the sub-scanning direction by the cylindrical lens 20A.

  The return light beam L2 (sub) is incident on the coupling lens 20A without being blocked by the aperture AP as a light beam having a light beam diameter smaller than the aperture width of the aperture AP.

Then, the light is condensed on the near side of the semiconductor laser light source 10 and enters the light receiving portion of the light detecting portion while being diverged.

  Therefore, in this example as well, problems caused by the surface tilt of the deflecting / reflecting surface 30A (the tilting axis of the deflecting / reflecting surface 30B) and the “processing / assembly error in the condensing optical system” can be avoided.

Further, since there is no “loss of light quantity of the return light beam L2 (sub)” due to the aperture AP, there is no deterioration of the synchronization detection accuracy.
FIG. 10 illustrates the state of the emitted light beam L1 (main) and the return light beam L2 (main) with the vertical direction as the main scanning direction.

  The emitted light beam L1 (main) emitted from the semiconductor laser light source 10 is converted into a weakly convergent light beam by the coupling lens 20A, and is shaped by the aperture AP.

  The beam-shaped emitted light beam L1 (main) passes through the cylindrical lens 20B and enters the deflecting / reflecting surface 30A while maintaining weak convergence.

  The return light beam L2 (main) reflected by the deflecting / reflecting surface 30A passes through the cylindrical lens 20B while narrowing the light beam width, as indicated by a broken line.

  Then, the light passes through the aperture AP without being blocked by the opening of the aperture AP, and is condensed by the coupling lens 20 </ b> A and is condensed on the front side of the semiconductor laser light source 10.

  And it injects into the light-receiving part of a light detection part, diverging.

In this way, since there is no “loss of light quantity of the return light beam L2 (sub)” due to the aperture AP in the main scanning direction, there is no deterioration in synchronization detection accuracy.
The semiconductor laser light source 10, the condensing optical systems 20A and 20B, the deflecting / reflecting surface 30A, and the aperture AP are preferably combined as shown in FIG. 8 and FIG. 10, or FIG. 9 and FIG.

  Specific numerical examples will be given below.

This numerical example is an example in which the optical arrangement of FIG. 8 and the optical arrangement of FIG. 10 are combined.
Light emission wavelength of semiconductor laser light source 10: 655 nm
Coupling lens 20A focal length: 14.5mm
Conversion state of emitted light beam by the coupling lens 20A: parallel light
Thickness of coupling lens 20A: 3mm
Focal length in the sub-scanning direction of the cylindrical lens 20B: 47 mm
Distance from the exit surface of the coupling lens 20A to the aperture AP: 33 mm
The width of the aperture AP opening in the sub-scanning direction: 1.7 mm
Distance from the aperture AP to the incident surface of the cylindrical lens 20B: 18 mm
Thickness of cylindrical lens 20B: 3mm
Distance from the exit surface of the cylindrical lens 20B to the deflecting / reflecting surface 30A: 43 mm
Effective range of the light receiving part of the light detecting part: 0.3 mm × 0.3 mm (rectangular)
FIG. 11 is an explanatory view showing “the form of the light beam in the sub-scanning direction” in this numerical example.

  In FIG. 11, the optical path of the reflected light beam below the deflecting reflecting surface 30A is shown developed on the opposite side to the incident side.

  The thick line represents the marginal ray of the emitted light beam L1 (sub) and the return light beam L2 (sub).

  The returning light beam L2 (sub) to the semiconductor laser light source 10 is defocused by +2.7 mm at the position of the light receiving portion of the light detecting portion.

FIG. 12 shows the relationship between the return light beam L2 (sub) and the light receiving unit of the light detection unit PD.
As shown, the return beam L2 (sub) beam diameter in the light receiving unit is 400 μm.
Since the effective range of the light receiving portion of the light detection portion PD is 300 μm in the sub-scanning direction, a positional deviation up to 100 μm is allowable, and a sufficient margin can be secured.
In FIG. 13, the light receiving unit is “parallel to the sub-scanning direction”.

  However, as shown in FIG. 13, even if the light receiving portion of the photodiode PD that is the light detecting portion is “a plane parallel to the X direction”, it is possible to irradiate an area area sufficiently larger than that of the light receiving portion.

  FIG. 13 shows the case shown in FIGS. In such a case, it is preferable to shift the condensing point of the return light beam LB (sub) behind the light receiving unit.

  In FIG. 13, the portion that holds the light emitting portion LS and the photodiode PD is transparent to the laser beam.

  12 and 13, the “negative direction” in the X direction points to the right side of the figure.

FIG. 14 shows an embodiment of the optical scanning device.
In this optical scanning device, the four scanned surfaces 11Y, 11M, 11C, and 11K are optically scanned with deflected laser beams.
The image carrier forming the substance of the four scanned surfaces 11Y, 11M, 11C, and 11K is a “photoconductive photosensitive drum”.
The electrostatic latent images formed on these four photosensitive drums are individually visualized with magenta, yellow, cyan, and black toners.
Then, the obtained four color toner images are superimposed to form a color image. Accordingly, in the following description, a common reference numeral is given to the surface to be scanned and the photosensitive drum that actually forms the surface.

In FIG. 14, reference numerals 1Y, 1M, 1C, and 1K denote “semiconductor laser light sources”.
The semiconductor laser light sources 1Y and 1M are arranged so as to overlap in the sub-scanning direction which is a direction orthogonal to the drawing.
The intensity of the semiconductor laser light source 1M is modulated by the “image signal corresponding to the magenta image”, and the intensity of the semiconductor laser light source 1Y is modulated by the “image signal corresponding to the yellow image”.

Similarly, the semiconductor laser light sources 1C and 1K are also arranged so as to overlap in the sub-scanning direction.
The intensity of the semiconductor laser light source 1C is modulated by the “image signal corresponding to the cyan image”, and the intensity of the semiconductor laser light source 1K is modulated by the “image signal corresponding to the black image”.

  The light beams emitted from the individual semiconductor laser light sources 1Y and 1M are converted into weakly focused light beams by the coupling lenses 3Y and 3M.

  The coupling lenses 3Y and 3M are arranged so as to overlap in the sub-scanning direction.

  Apertures 12Y and 12M are also arranged so as to overlap in the sub-scanning direction, and perform the above-described beam shaping.

  The laser beams that have passed through the apertures 12Y and 12M are condensed in the sub-scanning direction by the cylindrical lenses 5Y and 5M (arranged so as to overlap in the sub-scanning direction).

  The laser beam condensed in the sub-scanning direction is incident on the polygon mirror 7 which is an optical deflector.

  A “line image long in the main scanning direction” by the cylinder lenses 5Y and 5M forms an image in the vicinity of the deflection reflection surface of the polygon mirror 7.

The light beams deflected by the polygon mirror 7 pass through the scanning lenses 8Y, 8M, 10Y, and 10M, respectively, and form light spots on the scanned surfaces 11Y and 11M.
The scanned surfaces 11Y and 11M are optically scanned by these light spots.

Similarly, the light beams emitted from the semiconductor laser light sources 1C and 1K are converted into parallel light beams by the coupling lenses 3C and 3K, and pass through the apertures 12C and 12K.
Then, the light is condensed in the sub-scanning direction by the cylindrical lenses 5C and 5K arranged in the sub-scanning direction, and is incident on the polygon mirror 7 and deflected.

  The deflected light beams pass through the scanning lenses 8C, 8K, 10C, and 10K, respectively, form light spots on the scanned surfaces 11C and 11K, and optically scan these scanned surfaces.

  In the optical scanning device of FIG. 14, the coupling lenses 3Y to 3K and the cylindrical lenses 5Y to 5K combined therewith form four sets of “light collecting optical systems”.

  The scanning lenses 8Y to 8K and 10Y to 10K form four sets of “scanning optical systems”.

FIG. 15 is a diagram showing a configuration of an image forming apparatus using the optical scanning device shown in FIG.
In FIG. 15, “portion 200” is the portion of the optical scanning device described with reference to FIG.
As shown in FIG. 15, the polygon mirror 7 has four deflection reflection surfaces and has a two-stage configuration.
One of the light beams deflected at the upper stage of the polygon mirror 7 is guided to the photosensitive drum 11M by the optical path bent by the optical path bending mirrors mM1, mM2, and mM3.

  The other light beam is guided to the photosensitive drum 11C through an optical path bent by the optical path bending mirrors mC1, mC2, and mC3.

One of the light beams deflected on the lower side of the polygon mirror 7 is guided to the photosensitive drum 11Y by the optical path bent by the optical path bending mirror mY.
The other light beam is guided to the photosensitive drum 11K through the optical path bent by the optical path bending mirror mK.

Accordingly, the four photosensitive drums 11Y, 11M, 11C, and 11K are optically scanned by the light beams from the four semiconductor laser light sources 1Y, 1M, 1C, and 1K.
Each of the photosensitive drums 11Y to 11K is rotated at a constant speed in the clockwise direction, and is uniformly charged by charging rollers TY, TM, TC, and TK serving as charging means.
Then, the respective color images of yellow, magenta, cyan, and black are written by receiving optical scanning of the corresponding luminous fluxes, and corresponding electrostatic latent images (negative latent images) are formed.

  These electrostatic latent images are reversal developed by developing devices GY, GM, GC and GK, respectively.

  In this way, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on the photosensitive drums 11Y, 11M, 11C, and 11K, respectively.

These color toner images are transferred onto a “transfer sheet” (not shown).
That is, the transfer sheet is conveyed by the conveyance belt 17, and the yellow toner image is transferred from the photosensitive drum 11Y by the transfer unit 15Y.
Further, magenta toner images, cyan toner images, and black toner images are sequentially transferred from the photosensitive drums 11M, 11C, and 11k by the transfer units 15M, 15C, and 15K.

In this way, the yellow toner image to the black toner image are superimposed on the transfer sheet to compose a color image synthetically.
The color image is fixed on the transfer sheet by the fixing device 19 to obtain a color image.

In FIG. 15, the scanning lenses 8Y and 8M on which the light beam deflected to the right side of the polygon mirror 7 is incident may be integrated in two stages.
In FIG. 15, the same applies to the scanning lenses 8C and 8K into which the light beam deflected to the left side of the polygon mirror 7 is incident.

In the optical scanning device 200 used in the image forming apparatus shown in FIG. 15, the semiconductor laser light sources 1Y-1K shown in FIG.
Further, the positional relationship among the coupling lenses 3Y to 3K, the cylindrical lenses 5Y to 5K, the apertures 12Y to 12K, and the deflecting / reflecting surface forming the condensing optical system is determined as described above.

  By doing so, the optical scanning device shown in FIG. 14 can be simplified and the synchronization detection can be performed with high accuracy.

  A good image formation can be realized by the image forming apparatus as shown in FIG.

LS light emitting part
PD photodiode
L1 exit beam
L2 Return beam
10A Semiconductor laser light source

JP-A-5-181076 JP 2009-169362 A

Claims (6)

A semiconductor laser light source comprising a light emitting unit and a light detecting unit disposed in the vicinity of the light emitting unit;
An optical deflector for deflecting and scanning by reflecting a laser beam from the light emitting unit;
A condensing optical system for guiding the divergent laser beam from the light emitting unit to the deflecting and reflecting surface of the optical deflector;
A scanning optical system configured to guide a deflected laser beam deflected by the optical deflector onto a surface to be scanned to form a light spot, and to detect the laser beam reflected by the deflecting reflecting surface as the light detection unit In the optical scanning device that obtains the synchronous detection signal of the optical scanning,
A laser beam reflected by the optical deflector and traveling toward the semiconductor laser light source through the condensing optical system forms an image in the sub-scanning direction in the vicinity of the light-receiving unit of the light detection unit and diverges in the sub-scanning direction. to be incident on the light receiving unit focused while the optical arrangement from the semiconductor laser light source to said optical deflector is set,
An aperture for shaping a light beam from the light emitting portion toward the optical deflector by an aperture;
When the light beam reflected by the deflecting reflecting surface passes through the opening, the width of the reflected light beam is smaller than the width of the opening in at least one of the main scanning direction and the sub-scanning direction. An optical scanning device. The optical scanning device according to claim 1,
Is reflected by the deflection reflective surface of the optical deflector, and wherein the laser beams returning to the light detection unit, the sub-scanning direction of the light beam width of the light receiving portion, larger than the sub-scanning direction of the detection area of the optical detecting unit Optical scanning device. The optical scanning device according to claim 1 or 2,
An optical scanning characterized in that when the light from the light emitting unit is incident on the deflecting / reflecting surface in the main scanning section so as to be orthogonal to the deflecting / reflecting surface, the light detecting unit and the deflecting / reflecting surface are not conjugate in the sub-scanning direction. apparatus. The optical scanning device according to any one of claims 1 to 3,
Deflecting reflection surface and the light receiving portion of the optical detection unit, during operation of the optical deflector, the optical scanning device, characterized in that does not become a conjugate in the sub-scanning direction. The optical scanning device according to any one of claims 1 to 4,
An optical scanning device characterized in that the light detection unit also receives a laser beam emitted backward from the light emitting unit and functions to automatically adjust the emission intensity of the light emitting unit. An image forming apparatus that forms an image by optical scanning,
An image forming apparatus using the optical scanning device according to claim 1 as an optical scanning device for performing optical scanning.

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