JPH07113974A - Optical scanner - Google Patents

Abstract

PURPOSE:To improve reliability without impairing the mechanical precision of an optical scanner even when the scanner is attached into the application equipment of the optical scanner by reducing the rigidity of an attaching part for attaching an optical base to the equipment lower than that of the part other than the attaching part. CONSTITUTION:Various optical parts and mechanical parts are attached to the optical base 91. When the optical scanner is attached to the equipment, distortion occurs due to the precision of an attaching surface of a partner side and a difference between the coefficients of thermal expansion of members due to the temperature change, and thus, the relative positions of respective optical elements attached to the optical base 91 are deviated. For preventing that, it is required that the rigidity of the optical base 91 is increased, and by reducing the rigidity of only the attaching part, the matter that the whole optical base 91 is distorted is prevented. Then, this scanner is constituted so that the thickness of the low rigidity part 94 of the optical base 91 is formed thinner than that of other parts, and the distortion due to an error of the attaching position to the main chassis 101 of the equipment and the difference between the coefficients of thermal expansion due to the temperature are absorbed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used in a laser beam printer or the like, and more particularly to a method for mounting the optical scanning device.

[0002]

2. Description of the Related Art FIG. 16 shows an example of a conventional optical scanning device.
A laser beam (light flux) emitted from the semiconductor laser 211 is collimated into parallel light by a collimator lens 221, and is rotationally deflected by a rotary polygon mirror scanner 230. The deflected beam is imaged as a spot on the surface to be scanned via the scanning lens 251. Scanning lens 251
Is a beam deflected at a constant angular velocity by the scanner by holding the astigmatism and the field curvature to a certain amount in order to form a flat image on the surface to be scanned and by giving a negative distortion aberration. Is scanned at a constant linear velocity on the surface to be scanned.

When the optical scanning device is used for a device for recording or reading an image, recording or reading of image data is carried out based on an electric signal serving as a reference for starting scanning. In many optical scanning devices, a synchronous detector 271 such as a photodetector is provided on the optical path within the scannable range of the deflected beam and outside the effective scan range to detect that the beam has reached a predetermined position for each scan. is doing.

These optical elements are attached to the optical base 291. Due to the relative positional accuracy of each optical element, the imaging position of the laser beam emitted from the semiconductor laser 211 on the surface to be scanned and the aberration performance are greatly deteriorated. Therefore, it is necessary to precisely process the optical base 291 and the optical elements so that each optical element is at a predetermined position on the optical base 291. Further, when a predetermined accuracy cannot be obtained by processing the parts, adjustment work is required.

[0005]

However, even if the optical scanning device alone is precisely processed and adjusted, when the optical scanning device is incorporated into the device, the optical base 2 is caused by a mutual error of the mounting portions.
There was a problem of giving distortion to 91. Also,
Even if there is no distortion during mounting, the optical base 29
There is a problem that the optical base 291 is distorted due to the difference in linear expansion coefficient due to the temperature fluctuation of the member of No. 1 and the device-side member to which it is attached.

[0006] In order to solve this problem
In the 16 gazette, the position of the mounting portion is devised with respect to the reflecting member that reflects the deflected beam, and one of the two mounting portions is displaceable. However, in such a structure, the position of the mounting portion is limited, the degree of freedom in designing the optical scanning device is restricted, and a structure that is displaceable in the mounting portion must be adopted, so that the structure is complicated. There were problems with the cost and reliability of the device.

Therefore, an object of the present invention is to provide a scanning device even if the scanning device is installed in an applied device of the optical scanning device.
An object of the present invention is to provide a highly reliable optical scanning device without impairing the mechanical accuracy of the optical scanning device.

[0008]

In order to solve the above problems, an optical scanning device of the present invention includes a light source, a deflector for deflecting a light beam emitted from the light source, and a light beam deflected by the deflector. An optical scanning device having an imaging optical system for forming a spot of a predetermined shape on a scanning surface and an optical base to which at least one of a light source, a deflector, and an imaging optical system is attached. It is characterized in that the rigidity of the mounting portion for mounting to is lower than that of the portion other than the mounting portion.

Further, it is characterized in that the optical base and the mounting portion are integrally formed of the same material.

Furthermore, the present invention is characterized in that the optical base is made of a resin material.

Alternatively, the present invention is characterized in that the optical base is formed by pressing metal sheet metal.

Alternatively, the present invention is characterized in that a rubber material is interposed in the mounting portion.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a perspective view of an optical scanning device according to the present invention. The laser beam emitted from the semiconductor laser 11 is shaped into a predetermined beam shape by the collimator lens 21. The shaped beam is deflected by the deflection unit 30 and becomes a focused beam by the imaging lens 51. The deflected focused beam is reflected by the folding mirror 61, changes its direction, and is imaged in a predetermined spot shape on the surface to be scanned. In addition, the deflected beam has the synchronization detection mirrors (a) 62 and (b) 6 prior to scanning the surface to be scanned.
It is reflected by 3 and enters the sync detector 71 to generate a sync signal necessary for signal processing for each scanning. These components are fixed to the optical base 91.

FIG. 2 is a sectional view of the collimator unit 10 including the semiconductor laser 11 and the collimator lens 21 described above. The collimator lens 21 is a single lens whose one surface has an aspherical shape, is housed in the collimator lens barrel 22, and is fixed by a collimator lens retainer 23. An outer peripheral groove 29 is cut in the collimator lens barrel 22 and is in contact with the claw portion of the collimator lever 24. On the other hand, the tip of the collimator barrel 22 is pressed against the semiconductor laser by a collimator holding spring (not shown). Therefore, the collimator lever 24 is also biased by the spring in the same direction. One end of the collimator lever 24 is supported by a protrusion 28 provided on the collimator base 26, and the other end is pressed against the tip of the adjustment knob 27. The adjustment knob 27 is inserted into the collimator base 26 via the screw surface.

When the outer peripheral portion of the adjusting knob 27 is rotated, the adjusting knob 27 moves back and forth by δ relative to the collimator base 26. At this time, with the protrusion 28 as a fulcrum,
Since the collimator lever 24 acts as a lever,
The collimator lens barrel 22 moves by Δ = δ · a / b. However, a is the distance from the protrusion 28 to the contact portion with the outer peripheral groove 29 of the collimator barrel 22, and b is the distance from the protrusion 28 to the contact portion with the adjustment knob 27. That is, a slight displacement can be given to the collimator barrel 22 with respect to the pitch of the screw provided on the adjustment knob, and the distance between the collimator lens 21 and the semiconductor laser 11 can be precisely adjusted in the optical axis direction. .

After the adjustment, it is desirable to fix the adjusting knob 27 so that it will not be displaced due to an external impact. Another screw hole is provided in the collimator base 26 in a direction orthogonal to the adjustment knob 27, and the adjustment knob 27 is set with a set screw.
If is fixed, it can be readjusted by loosening the set screw. When the readjustment is not necessary, the adjustment knob 27 may be adhered to the collimator base 26.

Alternatively, the adjusting knob 27 and the collimator lever 24 are not provided, and the collimator lens barrel 22 is directly moved in the optical axis direction by an external jig to directly move the collimator lens barrel 22 at a predetermined position. You may adhere to 26. At this time, if the contact surface between the collimator barrel 22 and the collimator base 26 is large, the adhesive will penetrate into the entire surface. When the collimator lens barrel 22 and the collimator base 26 are made of members having different linear expansion coefficients due to temperature, distortion may occur and the state of precise adjustment may be impaired. In addition, since the criterion for coupling the two members is not clear, when the difference in linear expansion coefficient is positively used to compensate for various temperature characteristics, the correction effect as designed cannot be obtained. Things can happen. Therefore, as shown in FIG. 3, it is desirable to limit the bonding surface by dividing the surface of the collimator base 26 that supports the collimator barrel 22 into two or providing a clearance.

The semiconductor laser 11 is generally housed in a package with a circular flange having an emission window.
A laser chip that emits laser light from both sides of the end face of the device and a photodiode that receives one of the emitted beams are fixed in the package. Each element is electrically a diode, and one terminal of each is connected to common (common), so that three terminals are provided. Since one of the terminals is connected to the package itself, the collimator base 26 to which the semiconductor laser 11 is fixed should be electrically insulated. That is, it is possible to integrally form it with resin or the like. Since the optical scanning device according to the present invention is intended for a relatively small-sized and low-speed device, the light output is small and therefore the current flowing through the semiconductor laser 11 is small. Thus, even if the device is directly attached to the resin, the heat radiation of the element is sufficient. Secured in.

The semiconductor laser 11 is a collimator base 2
It is screwed to 6 using a laser pressing metal fitting (not shown). This is taken into consideration for removal in case of emergency, but if there is not such a need,
The semiconductor laser 11 may be directly press-fitted or adhered to the collimator base 26. The laser drive substrate 12 is
It is fixed to the collimator base 26 with screws, and the terminals of the semiconductor laser 11 described above are soldered. The synchronization detector 71 is also mounted on the same substrate. For the synchronization detector 71, a photodiode or an element in which a photodiode, an amplifier and a comparator are integrated is used. In recent years, many of these elements have a surface mount type package, but according to the arrangement of the optical scanning device of the present invention, the synchronization detector is provided on the side where the terminals of the semiconductor laser 11 are soldered on the laser driving substrate. 71 can be mounted, and it is easy to use a substrate having a conductor only on one surface.

The semiconductor laser 11 and the synchronous detector 71 must be electrically connected to a control device provided outside the optical scanning device by some method. Wiring means such as a covered wire or a flexible printed circuit board is used for connection. When these elements are mounted on independent boards, independent wiring means are naturally required. However, by placing the semiconductor laser 11 and the synchronization detector 71 on the same circuit board as described above, the wiring means to the control device can be integrated into one, for example, a common signal line such as a power line or a ground line. It is also possible to aggregate. Therefore, not only the cost but also the space for the connector and the like can be saved, and the number of connection points of the wiring can be reduced to improve the reliability. Further, the wiring of the scanner motor 35, which will be described later, is also integrated into the laser driving substrate 12 in the optical scanning device and then connected to the control device together with the wiring of the semiconductor laser 11 and the synchronization detector 71 by the same wiring means. By doing so, this effect is further enhanced.

Further, by mounting the semiconductor laser and the synchronization detector 71 on the same circuit board, the number of circuit boards is of course reduced as compared with the case where individual circuit boards are provided and mounted. It is possible to make the area much smaller than the combined area of the two circuit boards.

The deflection unit 30 uses a lens mirror scanner proposed in Japanese Patent Application No. 5-121995 previously filed by the applicant of this patent. Lens mirror 31 attached to the rotating part of scanner motor 35 shown in FIG.
As shown in FIG. 4, it has three optical surfaces, an entrance surface 32, a reflecting surface 33, and an exit surface 34, and deflects by internal reflection.
The entrance surface 32 and the exit surface 34 are the imaging lens 5 described later.
1 has a function of scanning the spot on the surface to be scanned at a constant linear velocity and a planar image forming function (correction of field curvature and astigmatism in optical characteristics).

In many cases, the lens mirror scanner can obtain the best optical characteristics when the rotation axis O is positioned within the reflecting surface. Therefore, two lens mirrors can be attached to the scanner motor 35 back to back with the reflecting surface 33.

Since such a lens mirror 31 can have a smaller outer shape than an ordinary rotary polygon mirror, it has a small moment of inertia and is less susceptible to air resistance (wind loss) due to rotation. Especially when rotating in the direction shown in FIG. 4, wind loss can be reduced. Therefore, the load on the scanner motor can be reduced, and the rotation speed can be increased and the power consumption can be reduced. Further, since the second moment of inertia is small, it is possible to reach a high rotation speed in a short time, and the time from when the scanner motor 35 starts rotating to when scanning becomes possible is short.

An optical element having a shape like the lens mirror 31 can be integrally formed of plastic, which is preferable in terms of cost. Further, since the density of the plastic is small, the mass of the lens mirror is small and it is less likely to be affected by unbalance due to an error in the mounting position of the lens mirror. Also, the second moment of inertia is small.

In comparison with the general rotary polygon mirror scanner, which is capable of scanning by the number of reflection surfaces (usually 2 to 6 surfaces) in one rotation, as described above, the lens mirror scanner,
Since only two lens mirrors are used, the number of scans for one rotation is small, and it is necessary to rotate the scanner motor 35 at high speed correspondingly. However, in the lens mirror scanner, as described above, the moment of inertia is small, and the windage loss and unbalance are small, so that the disadvantage of the small number of scanning can be sufficiently compensated.

On the other hand, even when the rotary polygon mirror scanner as described above is used in the present invention, the effect of the present invention can be exerted by designing such that the moment of inertia is small and the rotation speed is not large. . Further, even if a vibrating mirror such as a galvanometer mirror is used for the deflection unit, the same effect can be obtained.

A slight change in the number of rotations of the rotary type optical deflector causes "jitter", that is, a phenomenon in which the position of the image in the scanning direction changes slightly when an optical scanning device is used in a laser beam printer. , Not preferable. Since the lens mirror scanner has a large number of rotations, a large amount of energy is stored in the rotating system, and minute fluctuations in the rotation are smaller than those when the number of rotations is small.

Since the lens mirror 31 has optical power, the deflection angular velocity of the beam emitted from the emission surface 34 has a characteristic that it is fast in the vicinity of the scanning center and slow in the peripheral portion. This is preferable because the imaged spot finally moves at a constant linear velocity on the surface to be scanned.

The beam deflected by the deflection unit 30 is
Then, the light enters the imaging lens 51 shown in FIG. even here,
When the lens mirror scanner is used, the lens mirror 31 has optical power and shares a large part of the function of the scanning optical system. The image lens 51 can be arranged near the deflection unit 30, and the size can inevitably be reduced. In general, making the scan lens from plastic has a great cost advantage, but it becomes easy to make the scan lens plastic by reducing the size of the imaging lens 51. Needless to say, productivity is increased even when the glass is made by polishing.

Since the image forming lens 51 can be arranged near the deflection unit 30 or the lens mirror 31, it can be mounted on the scanner motor 35 in an overhanging manner. By adopting such a mounting method, the space in the optical scanning device can be used without waste. Further, the imaging lens 51 can be attached to the base portion of the scanner motor 35.

Generally, when a plurality of deflection surfaces are rotated to scan a light beam, the inclinations of the deflection surfaces with respect to the rotation axis are slightly different from each other due to processing errors and the like. Therefore, the scanning line drawn by the deflected light beam on the surface to be scanned is also displaced in the sub-scanning direction depending on the deflection surface used. If an image is recorded or read in this state, a scanning line pitch error occurs, which is not preferable for recording or reading the image. Therefore, when the optical system is viewed in the sub-scanning section, the deflecting surface and the surface to be scanned are designed to have an optical conjugate relationship or a state close thereto so that the deflection surface tilt error causes the deviation of the light beam in the sub-scanning direction. The angular displacement can be corrected. Such an optical system is generally called a “tilt correction optical system”.

When the shapes of the entrance surface and the exit surface of the imaging lens 51 are designed so as to have a tilt correction effect, a shape including a so-called anamorphic surface is formed such that the cross section in the scanning direction and the cross section in the sub-scanning have different shapes.

In this embodiment, both the entrance surface and the exit surface of the imaging lens 51 are toric surfaces. Also,
Depending on the configuration of the optical system, a plurality of lenses may be arranged between the deflection unit and the surface to be scanned. In that case, one of the surfaces of the constituent lens is anamorphic.

As an anamorphic surface, I mentioned above,
There are various types such as the one in which the curvature of the rotating arc gradually changes even on a toric surface, and the one in which the arc is rotated along the trajectory on the arc. Further, a cylindrical surface and the like are also included in the anamorphic surface described here.

In the case of such a scanning optical system, the astigmatic difference of the semiconductor laser 11, the shape accuracy of each lens and the deflecting element (the reflecting surface of the polygon mirror or the lens mirror in this embodiment), and the optical element made of plastic are used. Due to the precision of the refractive index distribution in the manufacturing process, the relative position adjustment between the collimator lens 21 and the semiconductor laser 11 as described above can satisfactorily form a spot on a predetermined scan surface in both the main scanning direction and the sub scanning direction. I can't make you image. In other words, the astigmatism amount of the scanning optical system does not reach a predetermined value, and the position where a predetermined image spot size is obtained in both the scanning direction and the sub-scanning direction is
Different in the optical axis direction.

In order to avoid this, for example, in a tilt correction optical system having a cylindrical lens between the semiconductor laser 11 and the deflection unit 30, by adjusting the position of this cylindrical lens in the optical axis direction, the above-mentioned astigmatism is obtained. The amount of aberration can be corrected. For example, with a cylindrical lens having power only in the sub-scanning direction, the position of the image point in the sub-scanning direction can be adjusted independently of the scanning direction.

However, in such a case, in order to make the deflecting surface and the surface to be scanned optically conjugate with each other, an image is often once formed in the sub-scanning direction by the cylindrical lens in the vicinity of the deflecting surface. Therefore, if the cylindrical lens is adjusted with reference to the image forming position of the main scanning / sub scanning surface on the surface to be scanned, the image forming point may be separated from the deflecting surface and the tilt correction effect may be impaired. .

When no anamorphic optical element other than the imaging lens 51 exists in the scanning optical system as in this embodiment, the main scanning / sub-scanning is performed except that the imaging lens 51 is adjusted in the optical axis direction. There is no means for adjusting the image forming position on the surface to be scanned in the direction.

When the image forming lens is composed of a plurality of lenses as described above or when another optical element is interposed between the deflection unit and the surface to be scanned, those lenses (optical element) are used. Among them, it is necessary to move and adjust the lens having an anamorphic surface such as a toric surface or a cylindrical surface in the optical axis direction.

In this embodiment, the imaging lens 51 is moved in the optical axis direction for adjustment. The adjusting mechanism of the imaging lens will be described with reference to the perspective view of FIG. The imaging lens 51 is attached to the imaging lens holder 53. The imaging lens holder 53 is provided with an elongated hole, and a pin having a diameter slightly smaller than the width of the elongated hole is provided on the optical base (not shown in this figure). Therefore, the imaging lens holder 5
Numeral 3 is movable only in the optical axis direction with respect to the optical base 91 by the linear guide mechanism constituted by the elongated hole and the pin. This imaging lens holder is adjusted from the outside with a minute feeding jig or the like while observing the imaging state on the surface to be scanned, and fixed at a predetermined position to the optical base by screwing or bonding.

Further, as shown in FIG. 6, the tilting of the imaging lens 51 in the scanning direction can be adjusted by separately providing the imaging lens holder 53 and adjusting the left and right independently. Recently, it is also possible to manufacture such an imaging lens by injection molding of resin. Therefore, by forming the adjusting member at the same time as the imaging lens, the number of parts can be reduced and the accuracy can be improved. Such an embodiment is shown in FIG.

In the previous embodiment, the guide mechanism for moving the imaging lens 51 in the optical axis direction is provided in the imaging lens holder 53 or the imaging lens 51 itself. On the other hand, the linear guide mechanism may be provided in a jig outside the device. FIG. 8 shows an image forming lens having such an adjusting hole. Holes for inserting the pins of the jig are provided at the left and right of the imaging lens 51 at the time of molding, and one hole has a long hole shape in order to absorb an error in the interval between the pins. At the time of adjustment, similarly to the previous case, the imaging lens is slightly moved in the optical axis direction while being pressed against the optical base 91. When reaching a predetermined position, the imaging lens 51 is adhesively fixed to the optical base 91. Further, if an adhesive reservoir 54 for accumulating a certain amount of adhesive is provided, highly reliable bonding is possible.

Further, when the mounting accuracy of the imaging lens is required, in this method as well, the pins of the jigs inserted into the left and right holes are independently moved to the left and right, so that any desired position in the scanning plane can be obtained. It is also possible to move the imaging lens in directions and angles.

The linear guide mechanism for the imaging lens 51 is
The combination of the pin and the groove is not limited to the above, and for example, the V groove or the U groove may be fitted to the corresponding projection portion, or the light of the imaging lens holder 53 (or the imaging lens 51 itself) may be simply used. You may use the end surface which exists in parallel to an axial direction. Furthermore, the same effect can be achieved with a mechanism that does not rely on sliding such as a rigid link mechanism. In the above-mentioned embodiment, the imaging optical system is composed of a single imaging lens. However, even when the imaging optical system is composed of a plurality of imaging lenses, a toric surface, a cylindrical surface, etc. By providing only the imaging lens including the anamorphic surface with the linear guide mechanism that is movable in the optical axis direction or having the movable structure, the same effect as described above can be achieved. Alternatively, by attaching a plurality of imaging lenses to the same imaging lens holder, the entire imaging optical system may be moved simultaneously.

As described above, by moving the imaging lens 51 having an anamorphic optical surface in the optical axis direction,
It is possible to correct variations in the amount of astigmatism due to various manufacturing errors and mounting errors of each optical element, including variations in the astigmatic difference of the semiconductor laser 11.

On the other hand, the imaging lens 51 and the semiconductor laser 1
Optical element including 1 and optical base 91 to which it is attached
Needless to say, such adjustment is not necessary when is accurate.

In general, when performing optical scanning to record (or read or reproduce) an image, the light is forcibly turned on at a certain fixed position in order to obtain a time reference in the scanning direction of the image data. The reference timing is obtained by detecting the passage of the beam with a detector placed in the optical path. Also in the present invention, the beam deflected by the deflection unit 30 and focused by the imaging lens 51 is reflected by the synchronous detection mirrors (a) 62 and (b) 63, and is provided on the laser drive substrate 12 already described. To the synchronized detector 71.

If the optical magnification from the imaging lens 51 to the synchronous detector 71 is equal to the optical magnification from the imaging lens 51 to the scanned surface, the speed of the beam that crosses the synchronous detector 71 is the same as the scanned surface. is there. In order to increase the detection accuracy of the sync signal, it is necessary to reduce the size of the spot that crosses the sync detector, or to increase the speed of crossing. Adding an element having negative power in the optical system leading to the detector increases the optical magnification and the scanning speed. Conversely, if an element having a positive power is added, the optical magnification becomes smaller and the spot size also becomes smaller. When the accuracy of the image to be recorded, read, or reproduced is not so high, it is preferable that the arrangement of such an element in the optical path increases the cost of the scanning device and complicates the structure. Absent. Therefore, in the embodiment of the present invention,
The synchronization detecting mirrors (a) 62 and (b) 63 are plane mirrors.

When the synchronization detecting mirror has an error with respect to a predetermined angle in the scanning direction, an error also occurs in the processing timing of image data based on the synchronization signal. Since the device has some means for electrically adjusting and correcting this error, mechanical adjustment of the mirror is unnecessary. Further, when the synchronization detection mirror tilts in the sub-scanning direction, the photodetector section of the synchronization detector 71 usually has a sufficient length in the sub-scanning direction. No need.

The scanning beam that has passed through the imaging lens 51 is directed to the surface to be scanned, but the distance from the imaging lens 51 to the surface to be scanned, that is, the working distance, is about the same as the effective scanning width, so that the effective scanning is performed at the shortest. About half the length is required.
It is often difficult to secure such a length in a device using an optical scanning device. Therefore, a plane mirror for folding the beam is required. When the space of the device is small, a plurality of folding mirrors are used to push the space for scanning the beam into a smaller volume.
However, the most commonly used glass flat plate on which aluminum is vapor-deposited has a reflectance of about 85% with respect to the wavelength of the near infrared semiconductor laser. Therefore, when a large number of folding mirrors are used, the mirrors may be provided with a reflection enhancing coating. Various places can be considered for attaching the folding mirror 61 depending on the structure of the device.

FIG. 9 shows a sectional view of a laser beam printer incorporating the optical scanning device according to the present invention. In this application example, the folding mirror 61 is attached to the optical base 91, and the cylindrical photosensitive member 102 is arranged on the surface to be scanned. That is, the sub-scanning is performed by rotating the photoconductor 102. The photoconductor 102 is housed inside the process unit 100. The photoconductor 102 is charged to an initial potential by the charger 103, and then selectively erased by a laser beam modulated with image data. The developer adheres to the photosensitive member 102 and is developed only in the selectively neutralized portion of the developing device 104 due to the potential difference between the potential applied to the developing roller and the exposed portion. The developer on the photoconductor 102 is transferred onto the transfer material by the transfer device 105. The developer transferred onto the transfer material is melted and fixed onto the transfer material by a heating roller and a pressure roller arranged in the fixing device 108 so as to sandwich the transfer material.

The position of the imaging spot on the surface to be scanned varies due to the relative position error of each optical element. In particular, the image forming position is displaced due to a positional error between the semiconductor laser 11 and the collimator lens 21 in a direction orthogonal to the optical axis direction. Therefore, it suffices to increase the processing accuracy of the related portion so that the relative position of the semiconductor laser and the collimator lens 21 has a required accuracy, but extremely high accuracy is required, which is not realistic. In addition, the semiconductor laser 11
The collimator lens 21 may be adjusted in a direction orthogonal to the optical axis direction. However, making the collimator part adjustable also complicates the structure and reduces reliability. Therefore, if the above-mentioned field curvature characteristics are not a problem and the position of the image forming spot is simply a problem, the accuracy of this collimator part should be kept to a feasible level and the image forming spot position should be adjusted by another method. Is a good idea.

Among the deviations of the image forming spot positions, in the main scanning direction, as described above, the timing from the synchronization signal generated by the synchronization detector 71 to the start of writing the image data is electrically variable. By doing so, it is possible to make an adjustment, so that no mechanical adjustment is necessary. On the other hand, the first problem caused by the position shift of the image forming spot in the sub-scanning direction is that the position of the image transferred on the transfer material varies in the transfer material conveying direction. This error can be adjusted by changing the transfer start timing of the transfer material. The second problem is the process unit 100.
That is, the scanning beam does not enter the width of the entrance window 106, and the beam does not reach the photoconductor 102. To avoid this, the mechanical accuracy of each part may be improved, but it is not preferable in terms of cost to unnecessarily request the parts with high accuracy, and it is difficult to manufacture the parts. Therefore, the position of the imaging spot in the sub-scanning direction can be adjusted by rotating the folding mirror 61 around an axis including the scanning surface and orthogonal to the optical axis.

In order to keep the position of the image forming spot within a predetermined error on the surface to be scanned as described above, the optical base 91 is used.
Although the required accuracy of the relative position of the optical element attached to the optical base 91 is very strict (within several μm in some cases), the positional error between the optical base 91 and the equipment to which it is attached is not so large. Therefore, the position of the imaging spot in the sub-scanning direction due to the relative position error of each optical element is adjusted by rotating the folding mirror 61 as described above with the optical base as a reference. With such a structure, the adjustment can be completed by the optical scanning device alone, and thus the optical scanning device can be handled as a compatible unit.

On the other hand, the folding mirror 61 is attached to the optical base 9
It is also possible to provide it on the side of the device in which the optical scanning device is incorporated without mounting it on the device 1. In addition, there may be a case where the space for the device is large and the folding mirror 61 is not necessary. In such a case, it is not necessary to attach the folding mirror 61 to the optical base of the optical scanning device. FIG. 10 shows a perspective view of an embodiment of such an optical scanning device. In this case, the optical base 91 can be made very small, the manufacturing cost can be reduced, and the device itself incorporating the optical scanning device can be made compact.

As described above, various optical parts and mechanical parts are attached to the optical base 91. To maintain the optical characteristics of these optical components in the initial state,
It is necessary to avoid dust and oils from attaching to the optical parts as much as possible. Therefore, an optical base cover 92 that is attached to the optical base 91 to form a semi-closed space is attached. The optical base cover 92 has an emission port 93 through which the scanned light beam is emitted. In order to completely prevent the intrusion of dust and oils and fats, it is desirable to provide a transparent member at the injection port 93 and seal it. On the other hand, when the cleanliness is not so required, or when the environment in which the optical scanning device is incorporated is relatively clean, it may be simply an opening. Also in this case, it is preferable in view of dust prevention that the size of the exit port 93 is set to the minimum necessary aperture through which the deflected beam can pass.

Although the emission port 93 is provided in the optical base cover 92 in the present embodiment, it is projected onto the optical base 91 because of the arrangement of the optical system constituting the optical scanning device and the positional relationship in the equipment to be attached. An outlet 93 may be provided.

When applied to a laser beam printer as shown in FIG. 9 as an application of the optical scanning device of the present invention, the deflected beam is folded back by the folding mirror 61. Therefore, by providing the exit 93 so as to have an opening downward, it is possible to prevent dust floating in the air from settling and entering the optical scanning device.

Since the scanner motor 35 rotates at a high speed, even if the rotational portion is precisely balanced and the shape of the portion that rotates and crosses the air is paid close attention, some vibrations and noises are inevitably generated. Absent. However, on the other hand, in the laser beam printer, which is one of the main application products of the optical scanning device, its use environment is spreading to ordinary offices and homes, and the generation of noise must be suppressed as much as possible.

Since the so-called "wind noise" generated when the rotating portion of the deflection unit crosses air is composed of a relatively high frequency component, by placing the deflection unit in the space formed by the optical base and the optical base cover, It is possible to reduce the sound pressure leaking to the.

However, the vibration due to the imbalance of the rotating portion, the rolling noise of the rolling bearing of the scanner motor, or the driving noise generated from the coil or magnet has a relatively low frequency component and its energy is large, so that it is simply sealed. Even so, the optical base or the optical base cover itself is vibrated to emit sound. Therefore, it is necessary to sufficiently secure the rigidity of the optical base and the optical base cover. Further, it is also effective to attach it to the optical base via a vibration-proof member such as a rubber bush so that the vibration of the scanner motor is not transmitted to the optical base. Alternatively, attaching a damping material such as a rubber sheet to a portion of the optical base or the optical base cover where vibration easily occurs is also effective for reducing the sound pressure.

When the optical scanning device is mounted on a device such as a laser beam printer as described above, distortion occurs due to the accuracy of the mounting surface of the other side and the difference in the coefficient of thermal expansion of the member due to the temperature change, so that the optical base 91 is distorted. The relative positions of the attached optical elements are displaced. In order to prevent this, it is desirable to increase the rigidity of the optical base 91. When the optical base 91 is made of a resin molded product, it is necessary to secure sufficient rigidity by providing reinforcing ribs.

In order to avoid such mounting distortion, it is very effective to reduce the rigidity of only the mounting portion so that the entire optical base is not distorted. 11, 12 and 13 show examples in which the rigidity of the mounting portion of the optical base is intentionally reduced. In this figure, the thickness of the low-rigidity portion 94 of the optical base 91 is formed thinner than the other portions, and absorbs the distortion due to the error in the mounting position with the main chassis 101 of the device and the difference in the linear expansion coefficient due to temperature. It is like this. In FIG. 11 and FIG. 13, a low-rigidity portion is integrally formed of resin on the outside of the outer wall portion of the optical base 91. Further, in FIG. 12, the wall thickness of a part of the outer wall to which the attachment part is connected is made thinner than that of the other part to reduce the rigidity. By doing so, compared to the case shown in FIGS. 11 and 13, the space around the mounting portion is not occupied.

The rigidity of the low-rigidity portion is set so that the accuracy required for the optical base 91 can be guaranteed while keeping the following items in balance.

(1) Shape accuracy of the optical base 91 and the main chassis 101 to which it is attached. (2) Similarly, a difference in thermal expansion due to temperature fluctuations of the optical base 91 and the main chassis 101. (3) Rigidity of the main chassis 101. (4) The magnitude, direction and rigidity of the load applied to the low rigidity portion 94. (5) Load and rigidity applied to the optical base 91 except for the low-rigidity portion 94. In addition, the mass of the optical base 91 supported by the low-rigidity portion 94 and the components attached thereto. Also, if the rigidity of the mounting part is reduced by mistake, the mounting position of the optical scanning device may cause an error due to the bending of the mounting part, or it may cause resonance with respect to external vibration. There is.

As a structure for lowering the rigidity as described above, in addition to the structure shown above, for example, when the optical base 91 is manufactured by pressing a metal plate, a hole is provided around the mounting portion. There is also a method. Alternatively, a similar effect can be obtained by providing such a relatively low-rigidity portion in the mounting portion on the main chassis side.

Further, as shown in FIG. 14, the rubber bush 9
The same applies when attached via 5, etc. In particular, if the material used for the rubber bush is a material with good damping characteristics (for example, low repulsion rubber), it will not
It is effective against shock. It is also useful to shut off the vibration of the scanner motor to the device side, and conversely,
It is also effective to block the vibration of the device side, for example, the vibration of the motor and other parts that drive the process in the laser beam printer so as not to be transmitted to the optical scanning device.

Since the optical base is made of resin, a free shape can be molded in one step, and thus it is a suitable manufacturing method for mounting various components on one optical base. On the other hand, since resin has a low thermal conductivity, it is not suitable for releasing heat from the inside, especially from the scanner motor and its drive circuit. Also, if electromagnetic noise coming from the outside of the optical scanning device jumps into the sync detector, an incorrect sync signal is generated. However, if the optical base is made of a conductive material, the effect of shielding external electromagnetic noise is higher. .

Similarly, from the viewpoint of resistance to electromagnetic noise, the optical base cover 92 is also preferably made of a conductive material.
When the optical base 91 and the optical base cover 92 are made of a conductive material and electromagnetic noise resistance is to be obtained, it is desirable to combine the two so as to obtain an electrically reliable contact.

As described above, depending on the specifications of the optical scanning device, it may be preferable that the optical base 91 is made of a metal material rather than resin. A casting method such as die casting is often used to manufacture a metal material, but the cost is high and the weight of the apparatus is increased. Therefore, it is preferable to press and manufacture a metal plate such as a plated steel plate. In this case, since sufficient rigidity cannot be obtained simply by arranging the optical elements on a simple flat plate member, a bent portion may be provided in the periphery,
Providing an overhanging rib in the central portion can increase the rigidity of bending or twisting. Further, when rigidity is required, it is effective to attach a reinforcing member as a separate member by welding or the like.

Further, as described above, the rigidity of the mounting portion for mounting the optical base on the device is preferably smaller than that of the other portion where the optical element is mounted.

The deflection unit 30 can be integrated with the optical base 91 instead of being an independent unit. FIG. 15 shows a sectional view of an optical scanning device in which the deflection unit 30 is integrated with the optical base 91. Even if the optical base 91 is made of resin, the merit of integrating the deflection unit 30 is great, but particularly when a metal plate is used, a part of the magnetic circuit of the scanner motor 35 that drives the deflection unit 30 by the optical base 91. Therefore, the number of parts cost can be reduced, and at the same time, the device can be downsized.

As another method for shielding external electromagnetic noise, an optical base or an optical base cover is made of a resin, and a conductive (for example, copper) metal is plated or coated on the surface or the inner surface. Is also effective. Alternatively, a conductive resin in which a conductive material is mixed with resin is also effective.

[0076]

As described above, according to the optical scanning device of the present invention, the rigidity of the mounting portion for mounting the optical scanning device on the device is made lower than the rigidity of the entire optical base, and the optical scanning device Due to the error in the mounting dimensions between the base mounting part and the equipment, and the difference in the linear expansion coefficient of each member due to temperature changes,
By absorbing the distortion, it is possible to reduce the change in the relative position of the optical element attached to the optical base due to the deformation of the optical base, which is good even when the optical base is attached to the equipment and the environmental temperature fluctuates. Imaging performance can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of an optical scanning device according to the present invention.

FIG. 2 is a sectional view of an embodiment of a collimator unit of the optical scanning device of the present invention.

FIG. 3 is a sectional view of another embodiment of the collimator unit of the optical scanning device of the present invention.

FIG. 4 is an operation diagram of a lens mirror scanner used in an embodiment of the optical scanning device of the present invention.

FIG. 5 is a perspective view of the first embodiment of the adjusting mechanism of the imaging lens of the optical scanning device of the present invention.

FIG. 6 is a perspective view of a second embodiment of the adjusting mechanism of the imaging lens of the optical scanning device of the present invention.

FIG. 7 is a perspective view of a third embodiment of the adjusting mechanism of the imaging lens of the optical scanning device of the present invention.

FIG. 8 is a conceptual diagram showing an embodiment of a method for fixing an imaging lens of an optical scanning device of the present invention.

FIG. 9 is a sectional view of a laser beam printer incorporating the optical scanning device according to the present invention.

FIG. 10 is a perspective view of another embodiment of the optical scanning device according to the present invention.

FIG. 11 is a perspective view showing a first embodiment of a mounting portion of the optical scanning device of the present invention.

FIG. 12 is a sectional view showing a second embodiment of the mounting portion of the optical scanning device of the present invention.

FIG. 13 is a perspective view showing a third embodiment of the mounting portion of the optical scanning device of the present invention.

FIG. 14 is a sectional view showing a fourth embodiment of the mounting portion of the optical scanning device of the present invention.

FIG. 15 is a cross-sectional view of still another embodiment of the optical scanning device of the present invention.

FIG. 16 is a perspective view showing an example of a conventional optical scanning device.

[Explanation of symbols]

 10 Collimator Unit 11 Semiconductor Laser 21 Collimator Lens 30 Deflection Unit 31 Lens Mirror 35 Scanner Motor 51 Imaging Lens 61 Folding Mirror 61 62 Sync Detection Mirror (a) 63 Sync Detection Mirror (b) 71 Sync Detector 91 Optical Base 92 Optical base cover 93 Injection port 94 Low rigidity part 100 Process unit 101 Main chassis

Claims (5)

[Claims] 1. A light source, a deflector for deflecting a light beam emitted from the light source, and an image forming optical system for forming an image of the light beam deflected by the deflector into a spot having a predetermined shape on a surface to be scanned. A light source, the deflector, and an optical base to which at least one of the imaging optical system is mounted, the rigidity of the mounting portion for mounting the optical base on a device is determined by the mounting portion. An optical scanning device characterized in that it is made lower than other parts. 2. The optical scanning device according to claim 1, wherein the optical base and the mounting portion are integrally formed of the same material. 3. The optical scanning device according to claim 2, wherein the optical base is made of a resin material. 4. The optical scanning device according to claim 2, wherein the optical base is formed by pressing a metal sheet metal. 5. The optical scanning device according to claim 1, wherein a rubber material is interposed in the mounting portion.