JPH0820131A - Optical device - Google Patents

Abstract

(57) [Abstract] [Purpose] An electrostatic latent image is formed by exposing a photosensitive drum by passing a light beam through a light transmissive cover plate 24 that closes a window hole 34 of a housing case 30 in a scanner unit. In this case, a means for attaching the cover plate 24 is provided at a low cost so that the toner does not enter the housing case 30. [Structure] An elongated window hole 34 is formed in an inclined portion 50 formed on the top plate 30a side of a lower surface open box type housing case 30, and the cover plate is covered at both longitudinal ends of the cover plate 24 covering the window hole 34. In order to contact and press the outer corners of the pair of substantially parallel side edges along the longitudinal direction of 24,
The locking claw block 52 and the elastic locking piece 53 are made to face each other and are integrally formed in the housing case 30 made of synthetic resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device, and more particularly to a mounting structure for a light-transmitting cover plate at a window hole portion of a housing case through which a light beam passes in the optical device.

[0002]

2. Description of the Related Art Conventionally, a scanning optical apparatus applied to an electrophotographic image forming apparatus such as a laser printer, a copying machine, a facsimile apparatus or the like has an upper surface open as disclosed in Japanese Utility Model Laid-Open No. 2-64959. In a box-shaped housing case, a rotary polygonal mirror having a hexagonal shape in plan view as a deflector that is rotated by a motor attached to the bottom surface thereof and a lens group as a scanning optical system such as an fθ lens are fixedly provided. A laser unit including a semiconductor laser element as a light source and a collimating lens is attached to one side wall surface of the housing case, and a light beam emitted from the laser unit is modulated in accordance with image data and is rotated by a rotating polygon mirror. The light beam that has been irradiated onto and is reflected here passes through a window hole formed in one side of the housing case through a lens group such as an fθ lens and is rotated. It is known that light is condensed (imaged) on the surface of the photosensitive drum.

In this case, in the scanning optical device described in the above publication, toner and dust are prevented from entering from the photosensitive drum or the like.
Since a cover plate made of a light-transmitting synthetic resin that also serves as a lens is attached to the window hole with one touch, a plurality of snap fit projections are integrally formed on the synthetic resin cover plate,
On the housing case side, there is disclosed a configuration in which a locking hole with which the plurality of snap fit projections are engaged is formed.

[0004]

However, in the above scanning optical device, since a complicated snap fit projection is integrally formed with the cover plate, a separate molding die is required,
Manufacturing cost is high. Moreover, there is a problem that the material of the cover plate and the like is limited to the synthetic resin material. Further, in the case of the engagement by the snap fit protrusion and the locking hole on the housing case side, when the cover plate is elongated, unless a number of snap fit protrusions are provided along the longitudinal direction of the cover plate, the cover plate is halfway in the longitudinal direction. Since the part floats from the surface of the housing case and toner and dust easily enter the housing case through the gap, there is a problem that a separate sealing material needs to be inserted.

The present invention has been made to solve these technical problems, and an object of the present invention is to provide an optical device which can reduce the manufacturing cost and which is difficult for toner and dust to enter the housing case. It is what

[0006]

In order to achieve the above object, the optical device according to the present invention comprises a housing case, a window hole through which a light beam passes, and a light-transmissive cover for covering the window hole. An optical device comprising a plate, wherein a locking claw block having a locking surface projecting at an acute angle with respect to the surface is formed on a surface of the housing case at an outer peripheral position of the window. The locking surface of the stop claw block is brought into contact with the outer corner of one side edge of the cover plate, while the outer corner of the other side edge of the cover plate is provided on the side facing the locking claw block. An elastic locking piece for pressing the surface of the case is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the window hole and the cover plate are formed in an elongated shape, and the housing case has the longitudinal ends of the cover plate at both ends thereof. The locking claw block and the elastic locking piece are integrally provided so as to face each other so as to contact the outer corners of a pair of substantially parallel side edges along the longitudinal direction of the cover plate.

An optical device according to a third aspect is the optical device according to the second aspect, wherein the surface of the housing case is
A restriction portion is formed to bend both end portions in the longitudinal direction of the cover plate outward from a midway portion in the longitudinal direction of the cover plate. An optical device according to a fourth aspect is the optical device according to the second aspect, wherein the surface of the outer periphery of the window hole in the housing case is convex so that a midway portion thereof projects outward along the longitudinal direction of the cover plate. It is curved.

[0009]

Next, an embodiment of the present invention will be described. FIG. 1 is a schematic side sectional view of a laser beam printer 1 as an image forming apparatus, and FIG. 2 is a side sectional view of a scanning optical apparatus. Main body case 2 in the printer 1 of this embodiment
A paper feed cassette 3 as a paper feed unit is detachably attached to the upper side of one side, and the paper P as a recording medium stacked in the paper feed cassette 3 is removed by the paper feed roller 4 and the separation pad 5. The sheets are separated one by one and sent to the image forming unit 9 via the pair of feeding rollers 6.

The image forming unit 9 includes a rotating photosensitive drum 7 as a photosensitive member and a transfer roller 8 as a transfer means.
In the case, a developing device unit 12 including a toner cartridge 10 and a developing roller 11 located near the paper feed cassette 3 side, a charging device 13 on the lower surface side of the photosensitive drum 7, a cleaning device 14 and the like are included in a kit. Stored in a single unit.

A fixing device 17 including a heating roller 16 and a pressing roller 15 is arranged on the discharge side of the image forming unit 9. Below the image forming unit 9, a scanner unit 18 as a scanning optical device for scanning a laser beam toward the lower surface of the photosensitive drum 7 has a top plate 30a of a housing case 30 which is open downward and is located above. Then, the main body case 2 is detachably mounted on the upper surface of the flat plate portion 2b of the main frame 2a.

A laser emitted from a scanner unit 18, which will be described later, according to image data transmitted from an external device such as a host computer (not shown) on the surface of the photosensitive drum 7 which has been precharged by the charging device 13. Irradiate light to form an electrostatic latent image on the surface of the photosensitive drum 7,
Then, the developing roller 11 is rotated to perform the development in which the latent image is visualized by supplying the charged powdery toner, and then the transfer between the photosensitive drum 7 and the transfer roller 8 is performed. The toner image is transferred onto the sheet P supplied to the portion, and then the toner image is passed between the heating roller 16 and the pressing roller 15 in the fixing device 17 to apply heat and pressure to the transferred toner image. To fix the toner image on the sheet P. After that, the paper output tray 63 is connected via the paper output roller pair 62.
It is what is discharged to.

A high voltage substrate 61 for applying a high voltage to the control substrate 60, the charging device 13 and the transfer roller 8 is arranged below the main frame 2a.
Next, the configuration of the scanner unit 18 will be described with reference to FIGS. FIG. 3 is a view taken along the line III-III in FIG. 2 and shows a downward open box type housing case 3
0 is a bottom view of the inside of FIG. 4, and FIG. 4 is IV-IV of FIG.
It is a line arrow view, and is a top view which looked at the housing case 30 downwards (the top plate 30a was turned up).

In the scanner unit 18, the laser emitting unit 20 and the rotary polygon mirror 27, f as a deflector.
The components including the θ lens 21, the cylindrical lens 22, the folding mirror 23, the writing signal (BD) mirror 25, the writing signal (BD) detection sensor 26, and the like are mounted on the top plate in the downward open box type housing case 30. 30a
Is fixed to the inner surface (lower surface) of the.

Then, the lens group and the folding mirror 23
A glass plate for covering the outer surface of the window hole 34 through which the light beam radiated toward the photosensitive drum 7 through the glass plate, or a light-transmissive cover plate 2 made of a transparent synthetic resin plate material.
Numeral 4 is detachably fixed to the top surface (outer surface) of the top plate 30a by means described later. A laser light emitting unit 20 in which a semiconductor laser as a light source and a collimating lens (both not shown) are built in a block body 28.
Is arranged on one side farther from the photoconductor drum 7 and fixed to the lower surface of the top plate 30a with screws. A printed wiring board 29 is attached to the back surface of the block body 28.

A rotary polygonal mirror 27 such as a six-sided mirror that rotates in a substantially horizontal direction by a drive motor 31 fixed to the inner surface of the top plate 30a is incident from the laser emitting unit 20 toward this mirror surface. The optical axis of the light beam is the photosensitive drum 7.
Is arranged so as to be substantially parallel to the rotation axis of the. The light beam reflected by the mirror surface of the rotary polygon mirror 27 has mounting members 32a, 32b, 33 made of leaf springs at both ends.
The light is reflected by the folding mirror 23 toward the lower surface of the photosensitive drum 7 through the fθ lens 21 and the cylindrical lens 22 which are fixed to a mounting slit (not shown) of the top plate 30a via a and 33b. Top plate 3 of housing case 30
0a is provided with a long window hole 34 in a portion close to the lower surface of the photoconductor drum 7 in parallel with the axis of the photoconductor drum 7, and through the cover plate 24 covering the window hole 34,
The deflected light beam scans the lower surface of the photoconductor drum 7 along the axial direction of the photoconductor drum 7.

In the fθ lens 21, the distance from the optical axis of the lens 21 to the image spot on the surface of the photosensitive drum 7 is the principal ray reflected by the reflecting surface of the rotary polygon mirror 27 which is a deflector. Deflection angle θ formed by the optical axis of fθ lens 21
It has the characteristic of being proportional to. A BD (Beam Detector) mirror 25, which is also fixed by a leaf spring (not shown), is arranged near one end in the longitudinal direction of the folding mirror 23, and the light emitted from the laser emitting unit 20 is emitted. A write start position signal (B for detecting the write start position in the horizontal direction of the photosensitive drum 7 of the beam).
(D signal) via the rotary polygon mirror 27, the fθ lens 21, the cylindrical lens 22, the BD mirror 25, the slit body 35, and the condenser lens 36, and the BD detection sensor 26.
To be input to. A laser drive board (printed wiring board) 37 for processing the signal input to the BD detection sensor 26 and driving the laser emission unit 20 is abutted against the end surface of a rib protruding downward from the inner surface of the top plate 30a. They are in contact with each other and fixed with screws 38.

Next, the first embodiment of the structure of the means for mounting the cover plate 24 will be described in detail with reference to FIGS. The window hole 34 is located on the front side of the top plate 30a of the housing case 30 made of glass reinforced plastic mixed with short glass fibers (the side close to the photosensitive drum 7).
In the inclined portion 50, the left and right sides are formed along the axis of the photoconductor drum 7 in a range that does not extend outside the peripheral side wall 30b of the housing case 30. A pair of left and right locking claw blocks 52, 52 are formed from the left and right long ribs 51 projecting upward from the inclined portion 50, and the locking surfaces (lower surfaces) thereof are approximately 60 degrees with respect to the surface of the inclined portion 50. Longitudinal direction of the cover plate 24, which is formed in an acute angle with an angle θ1 and integrally protrudes (see FIG. 9), and is attached to the surface of the inclined portion 50 at the engagement surface of each engagement claw block 52. The one side edge is brought into contact with the outer corner portion (corner portion on the side away from the surface of the inclined portion 50).

The left and right locking claw blocks 52 and 5 are also provided.
The peripheral side wall 30 is provided at a position facing each other (facing each other).
The proximal end 53a side of the substantially U-shaped elastic locking pieces 53, 53 is fixedly provided on the outer surface of b (see FIGS. 6 to 8). At this time, the outer surface of each elastic locking piece 53 on the side of the free end 53b is elastically moved toward the surface of the inclined portion 50 at the outer corner portion of the other side edge in the longitudinal direction parallel to the one longitudinal edge of the cover plate 24. The free end 53b is formed so as to extend in an acute angle with an angle θ2 of about 60 degrees or the like with respect to the surface of the inclined portion 50 (see FIG. 9).

With this configuration, the elongated cover plate 24 is arranged on the outer surface (front surface) of the inclined portion 50 so as to cover the window holes 34, and both free ends 53b of the elastic locking pieces 53, 53 on the left and right sides. , 53b are bent by fingers so as to approach the base ends 53a, 53a against elasticity, and the free ends 53
When the cover plate 24 is inserted between the locking claw blocks 52, 52 and the locking claw blocks 52, 52 and the fingers are released from the free ends 53b, 53b, the free ends 53b of the elastic locking pieces 53 are covered with the cover plate 24. By pressing the outer corner of the other side edge in the longitudinal direction, a force that presses the cover plate 24 in the width direction acts, so that the outer corner of the one side edge in the longitudinal direction of the cover plate 24 acts on each of the above-mentioned members. Since the pressing plate is pressed so as to come into contact with the locking surface which is the lower surface side of the pawl block 52, the cover plate 24 can be mounted so as not to separate from the surface of the inclined portion 50.

As shown in FIGS. 7 and 8, stopper pieces 5 are provided at both left and right ends of the inclined portion 50 to prevent the cover plate 24 from shifting in the longitudinal direction and falling off.
4 and 54 are integrally molded, and the locking claw block 52 and the elastic locking piece 53 at the opposite positions are integrally molded when the housing case 30 is injection molded. Die cutting spaces 55a and 55b are formed between the end of the portion 50 and the stopper piece 54.

Further, on both right and left end surfaces of the inclined portion 50, both longitudinal end portions of the cover plate 24 are curved outward from a longitudinal midway portion of the cover plate 24, resulting in an inner surface of the cover plate 24. A restricting portion is formed so as to closely contact the surface of the inclined portion 50 with no space. In the first embodiment, as shown in FIG. 10, the cover plate 2 including the locking claw blocks 52 and the elastic locking pieces 53 at the positions facing each other.
The surface of the inclined portion 50 on the side closer to the stopper pieces 54, 54 than the pressing portions of the both outer corner portions in the width direction of 4 approaches the stopper pieces 54 in the longitudinal direction of the inclined portion 50 (the middle portion on the left and right). The slanted restricting portions 56, 56 are provided at a position higher than the height position of the surface of the.

With this structure, the cover plate 24 is supported at a position where both ends in the longitudinal direction are supported at a position higher than the middle part, and the part closer to the middle part than the both ends is locked. Inclined portion 50 with block 52 and elastic locking piece 53
The pressing force acts on the surface of the cover plate 24, so that the elastic deformation of the cover plate 24 causes it to curve downward in FIG. 10 so that its midway portion in the longitudinal direction is pressed against the surface of the inclined portion 50, and as a result, The cover plate 24 can be attached to the surface of the inclined portion 50 without any gaps.

FIG. 11 shows a second embodiment of the present invention, in which the locking claw blocks 52 and the elastic locking pieces 53 located at the positions opposite to each other are more pressed than the pressing points at both outer corners in the width direction of the cover plate 24.
On the surface of the inclined portion 50 on the side closer to the stopper pieces 54, 54, there are provided ridge-shaped or protrusion-shaped restriction portions 57, 57. Even with this structure, the same operation and effect as those of the first embodiment can be obtained.

FIG. 12 shows a third embodiment, in which the inclined portion 5
1 so that the middle part of the surface of the outer periphery of the window hole 34 of 0 extends outward along the longitudinal direction of the cover plate 24.
2 is formed in a convex curve upward. According to this structure, opposite to the first embodiment shown in FIG. 10 and the second embodiment shown in FIG. 11, both end portions of the cover plate 24 have locking claw blocks 52.
Also, since a force is applied to the surface of the inclined portion 50 by the elastic locking piece 53, the cover plate 24 is pressed by the elastic deformation of the cover plate 24 so that the middle portion in the longitudinal direction is pressed against the surface of the inclined portion 50. In FIG. 12, the cover plate 24 is curved so as to be convex upward, and as a result, the cover plate 24 can be attached to the surface of the inclined portion 50 without any gap.

In the fourth embodiment shown in FIG. 13, elastic locking pieces 53, 5 which are U-shaped in a side view are formed on the outer surfaces of the left and right peripheral side walls 30b, 30b of the housing case 30 as in the previous embodiments.
3 is provided, while the slanted portion 5 on the outer peripheral side of the elongated window hole 34
One locking claw block 58 whose locking surface protrudes at an acute angle with respect to the surface of the inclined portion 50 is formed at the middle portion in the longitudinal direction of the window hole 34, which is the outer surface (front surface) of 0. .

Also according to this structure, the free ends 53b, 53b of the pair of left and right elastic locking pieces 53, 53 press the cover plate 24 in the width direction, so that the cover plate 24 is closed.
The outer corner of the one side edge in the longitudinal direction comes into contact with the locking surface of the locking claw block 58 and is irremovably pressed. In any case, since the locking claw blocks 52 and 58 and the elastic locking piece 53 can be integrally formed when the housing case 30 made of synthetic resin is molded, the locking claws are provided as separate parts together with the cover plate 24. The manufacturing cost is cheaper than molding the same. Further, the cover plate 24 may be made of glass or synthetic resin as long as it has optical transparency,
This also reduces the manufacturing cost because the material is not limited.

To assemble the scanner unit 18 as the scanning optical device to the printer 1,
A pair of front and rear tie bars 40, 41 are previously attached to the top surface (outer surface) of the top plate 30a of the housing case 30 with screws 42, 43, 4 respectively.
4, 45, and the housing case 30 is turned upside down and arranged so that the inner surface of the top plate 30a faces upward (see FIG. 3). The wiring board 37 is fixed.

Next, the pair of tie bars 40 and 41 are set on a predetermined performance inspection jig to set the intensity of the light beam emitted from the laser emitting unit 20, and then the fθ lens 21 and the cylindrical. The fixing posture and the like of the lens 22 and the like are inspected, and further, the position of the slit body 35 is adjusted so that the BD signal is received by the BD detection sensor 26, and then the slit body 35 is fixed with an adhesive.

Thereafter, a sealing material 46 such as a sponge material made of synthetic resin is placed over the free end edge of the peripheral side wall 30b of the housing case 30, and the housing case 3
0 downward (top plate 30a up) (see FIGS. 4 and 5), and placed on the upper surface of the flat plate portion 2b of the main frame 2a in the main body case 2 made of synthetic resin, and the pair of tie bars 40 , 41 are fixed to the predetermined portions such as the stepped portion 2c of the main frame 2a with screws 47 and 48.

With this structure, the optical system including the laser light emitting unit 20, the rotary polygon mirror 27, the fθ lens 21, and the like, which are the respective components of the scanning optical device, are all mounted on the lower open box type housing case 30. The window hole 34, through which the light beam passes, is covered by the cover plate 24 that is brought into close contact with the surface of the inclined portion 50 by the locking claw blocks 52 and 58 and the elastic locking piece 53, and Since the sealing material 46 is inserted and fixed between the lower end of the peripheral side wall 30b of the housing case 30 and the upper surface of the flat plate portion 2b of the main frame 2a, the upper surface of the conventional upward open box type housing case. The toner leaking from above the housing case 30 may enter the inside of the housing case 30 while saving the trouble of attaching a separate lid to the inside of the housing case 30. Completely prevented, there is no soiling of the components of the scanning optical device of the housing case 30.

It should be noted that the optical components such as the semiconductor laser, each lens, and the mirror may cause a positional shift with the passage of time, which may hinder the operation of the scanning optical device. In such a case, it is possible to replace only the defective optical component, but since the mounting accuracy of the optical component is required at the time of replacement, the entire unit of the scanning optical device is usually replaced. At this time, the top plate 3 of the housing case 30 is previously
If a plurality of tie bars 40 and 41 are attached to the upper surface of the main frame 2a,
The housing case 30 can be attached by simply fixing the housing case 30 to a proper place with a small number of screws, which has the remarkable effect of simplifying the attachment work.

As another embodiment, the housing case 30
It goes without saying that the laser light emitting unit 20 may be fixed to one outer side of the peripheral side wall. Also,
The window hole 34 defines the side wall 30b of the housing case 30.
The cover plate 24 for covering that portion is formed by the locking claw block 52 or the base plate 57 and the elastic locking piece 53 that can be integrally molded when the housing case 30 is molded. Needless to say, the present invention can be applied to the case where the cover plate 24 is arranged inside the housing case 30 and can be brought into close contact with the surface of the peripheral side wall 30b.

Further, it goes without saying that the present invention can also be applied to a scanning optical device in an electrophotographic image forming apparatus such as a facsimile or a copying machine, and other optical devices used for image processing and the like. In this case, when the light-transmitting cover plate 24 having a short length such as a rectangular shape or a square shape in plan view is used, the cover plate is formed by a set of one locking claw block 52 and one elastic locking piece 53. It goes without saying that 24 can be detachably attached to the housing case 30.

[0035]

As described above, the optical device of the present invention is an optical device having a housing case having a window hole through which a light beam passes and a light-transmissive cover plate covering the window hole. A device, wherein the surface of the housing case is
A locking claw block whose locking surface projects at an acute angle with respect to the surface is formed at an outer peripheral position of the window hole, and the locking surface of the locking claw block forms an outer corner portion at one side edge of the cover plate. On the side facing the locking claw block, an elastic locking piece for pressing the outer corner of the other side edge of the cover plate toward the surface of the housing case is provided on the side facing the locking claw block. is there.

Therefore, it is not necessary to integrally form the locking claw block and the elastic locking piece with the cover plate, and the cover plate may be made of glass or synthetic resin as long as it is light-transmissive. Since it is eliminated, this also brings about an effect that the manufacturing cost can be reduced. According to a second aspect of the present invention, in the optical device according to the first aspect, the window hole and the cover plate are formed in an elongated shape, and the housing case has the cover plate at both ends in the longitudinal direction of the cover plate. The locking claw block and the elastic locking piece are integrally provided so as to face each other so as to come into contact with the outer corners of a pair of substantially parallel side edges along the longitudinal direction. Therefore, the locking claw block and the elastic locking piece,
Since the housing case made of synthetic resin can be integrally formed at the time of molding, the manufacturing cost is lower than that when the locking claw and the like are formed together with the cover plate as a separate component.

Further, the invention according to claim 3 is the same as claim 2
In the optical device described above, the housing case is formed with a restricting portion for bending both longitudinal end portions of the cover plate outward from a longitudinal midway portion of the cover plate, so that it is elongated. The cover plate is supported by so-called two-points at the restriction portions near the left and right ends thereof, and the portion closer to the center in the longitudinal direction is opposed to the acting direction of the supporting reaction force by the combination of the locking claw block and the elastic locking piece. By pressing in the direction, the cover plate can be elastically curved so that the longitudinal midway side thereof comes into close contact with the surface of the housing case.

Therefore, according to the present invention, it is possible to prevent dust and the like from entering through the window hole of the housing case with a simple structure without inserting a sealing material between the cover plate and the surface of the housing case. Play. Similarly, in the invention according to claim 4, in the optical device according to claim 2, a midway portion of the surface of the outer periphery of the window hole in the housing case projects outward along the longitudinal direction of the cover plate. Since the cover plate is formed in a convex curve like this, if a pressing force is applied to the elongated cover plate at the left and right end parts by a pair of the locking claw block and the elastic locking piece, the cover plate is elastically deformed by itself. Due to the force, it is curved and deformed along the surface of the housing case so that they can come into close contact with each other. Therefore, according to the present invention as well, it is possible to prevent dust and the like from entering through the window hole of the housing case with a simple structure without inserting a sealing material between the cover plate and the surface of the housing case.

Therefore, according to all the inventions described above, it is possible to provide an optical device which can simplify the assembling work and reduce the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of a laser printer.

FIG. 2 is a side sectional view of a scanning optical device.

FIG. 3 is a view taken along the line III-III in FIG.

4 is a view taken along the line IV-IV of FIG.

5 is a cross-sectional view taken along the line VV of FIG.

6 is a sectional view taken along the line VI-VI of FIG.

FIG. 7 is a perspective view showing a locking claw block and an elastic locking piece of the first embodiment.

FIG. 8 is a plan view of an essential part of the first embodiment.

9 is an enlarged sectional view taken along the line IX-IX of FIG.

10 is a sectional view taken along line XX of FIG.

FIG. 11 is a sectional view of the second embodiment.

FIG. 12 is a sectional view of the third embodiment.

FIG. 13 is a plan view of the fourth embodiment.

[Explanation of symbols]

 1 Printer 2 Main Body Case 7 Photosensitive Drum 9 Image Forming Unit 18 Scanner Unit 20 Laser Emitting Unit 21 fθ Lens 22 Cylindrical Lens 23 Folding Mirror 24 Cover Plate 25 Writing Signal Mirror 26 BD Detection Sensor 27 Rotating Polyhedral Mirror 30 Housing Case 30a Top plate 30b Peripheral side wall 34 Window hole 50 Inclined part 52,58 Locking claw block 53 Elastic locking piece 56,57 Restricting part

Claims (4)

[Claims] 1. An optical device comprising a housing case having a window hole through which a light beam passes, and a light-transmissive cover plate covering the window hole. A locking claw block having a locking surface protruding in an acute angle with respect to the surface is formed, and the locking surface of the locking claw block is brought into contact with an outer corner of one side edge of the cover plate. An optical device is provided on the side facing the locking claw block, and an elastic locking piece for pressing an outer corner portion of the other side edge of the cover plate toward the surface of the housing case. . 2. The window hole and the cover plate are formed in an elongated shape,
At the housing case, at both ends of the cover plate in the longitudinal direction, the locking claw block and the elastic engagement member are elastically engaged with the outer corner portions of a pair of substantially parallel side edges along the longitudinal direction of the cover plate. The optical device according to claim 1, wherein the stopper and the stopper are integrally provided so as to face each other. 3. A restricting portion is formed on a surface of the housing case for bending both end portions in the longitudinal direction of the cover plate outward from a midway portion in the longitudinal direction of the cover plate. 2. The optical device according to item 2. 4. The surface of the outer periphery of the window hole portion of the housing case is formed in a convex curve so that a midway portion thereof projects outward along the longitudinal direction of the cover plate. Optical device.