JPH04237012A - Optical scanner - Google Patents

Abstract

PURPOSE:To prevent the intrusion of dust into an optical case even at the time of exchanging a photodetecting element by using an auxiliary lens to hermetically close the optical case and disposing the photodetecting element on the outside thereof. CONSTITUTION:Light beam polarization scanning means 23 to 26 are provided in the optical case 21 and the photodetecting element 32 is irradiated via the auxiliary lens 30 with a part of the deflected light beams to obtain a synchronizing signal. The auxiliary lens 30 constitutes a part of the hermetic structure of the optical case 21 and the photodetecting element 32 is disposed on the outer side of the optical case 21. Then, the mounting and exchanging of the photodetecting element 32 are possible without opening the optical case 21.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device used in image forming apparatuses and the like.

0002

[Prior Art] In a scanning optical device in which a light beam emitted from a light source is deflected and scanned by a rotating polygon mirror, there is a surface division error on each surface of the rotating polygon mirror, so a photodetector device that obtains a horizontal synchronization signal in the scanning direction Is required.

FIG. 4 shows a configuration diagram of a scanning optical device. A light beam L emitted from a light source unit 2 fixed to an optical case 1 and containing a semiconductor laser light source is a rotating polygon that is rotated at high speed in the direction of the arrow by a drive motor. It is converted into scanning light by a mirror 3, passes through an imaging lens group 4 having f/θ characteristics, and is focused onto a photoreceptor drum 6 via an optical glass plate 5.
A recorded image is formed in the direction of the arrow. In addition to the light source unit 2, rotating polygon mirror 3, and imaging lens group 4, members for detecting horizontal synchronization signals are fixed to the optical case 1. That is, a part of the light beam L' in the non-image area and on the image writing side is made to enter the reflection mirror 7, and the light reflected by the reflection mirror 7 passes through the auxiliary lens 8 and the slit 9 and reaches the photoelectric conversion element 10. Upon incidence, a horizontal synchronization signal is generated from the photoelectric conversion element 10. All of these members, except for the light source unit 2 and the photoreceptor drum 6, are hermetically housed in the optical case 1 to prevent abrasion powder, dust, etc. from entering. The output of the photoelectric conversion element 10 is connected to a DC controller 12 via a signal line 11.

0004

However, in the conventional example described above, in order to draw out the signal line 11 of the photoelectric conversion element 10 to the outside of the optical case 1, it is necessary to prevent dust from entering through the gap between the signal line 11 and the extraction hole. A rubber bush 13 is required, and its installation is not easy. Also, when replacing the photoelectric conversion element 10 due to failure or end of life, the inside of the optical case 1 must be opened, and developer and dust may get inside. There is a high possibility that something like this will be included.

The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a scanning optical device that prevents dust from entering an optical case even when a photodetecting element is replaced.

[0006]

[Means for Solving the Problems] In order to achieve the above object, in the scanning optical device according to the present invention, a light beam deflecting and scanning means is provided in the optical case, and a part of the deflected light beam is directed to the auxiliary lens. in order to obtain a synchronization signal by irradiating the light onto a photodetection element through a auxiliary lens, the auxiliary lens constitutes a part of the sealed structure of the optical case, and the photodetection element is arranged outside the optical case. It is something to do.

[0007]

[Operation] In the scanning optical device having the above-described structure, a portion of the deflected light beam passes through the auxiliary lens that seals the optical case, enters the photodetecting element outside the optical case, and generates a synchronization signal.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the embodiments shown in FIGS. 1 to 3.

FIG. 1 shows a configuration diagram of a scanning optical device, in which a light source unit 22 is attached facing inward to the side surface of an optical case 21 integrated with an optical frame, and inside the optical case 21 are a cylindrical lens 23 and a rotating polygon mirror 24. is placed,
A spherical lens 25 composed of an fθ lens and a toric lens 26 are arranged in sequence in the direction of reflection by the rotating polygon mirror 24, and the side surface of the optical case 21 on the extension thereof is made of a transparent optical glass plate 27 that transmits the laser beam. , a photosensitive drum 28 is arranged on the outer front side thereof. The rotating polygon mirror 24 is rotated in the direction of the arrow by a drive source (not shown), and is located on the optical path immediately before the scanning of the light beam by this rotation and between the toric lens 26 and the optical glass plate 27. A reflecting mirror 29 is installed between them, and an auxiliary lens 30 fitted near the through hole 21a on the side surface of the optical case 21, a slit 31, and a photoelectric conversion element 32 are sequentially arranged in the direction of reflection. Photoelectric conversion element 32
is connected to a DC controller 33 via a signal line 34, and the DC controller 33 sends a signal to a modulation circuit 35 to generate a signal to start modulating the light beam of the light source unit 22.

The auxiliary lens 30 is made of a synthetic resin material, and has a fixed portion 20a protruding left and right as shown in FIG.
This fixing part 30a is a through hole 21a on the inner surface of the optical case 21.
The optical case 21 is hermetically held between a collar 21b provided near the optical case 21. Through hole 21a of optical case 21
A protrusion 21c is formed around the periphery of the substrate 21c, and a substrate 36 having a slit 31 and a photoelectric conversion element 32 attached thereto is removably fixed to the protrusion 21c. Then, the auxiliary lens 30 closes the through hole 21a, and the optical case 21 is sealed by closing with a lid.

The light beam emitted from the light source unit 22 is focused in the sub-scanning direction by a cylindrical lens 23, deflected by a rotating polygon mirror 24, and then passed through a spherical lens 25 and a toric lens 26 to an optical case 21.
The light is emitted from the photosensitive drum 28, which rotates in the sub-scanning direction, and is scanned at a constant speed in the horizontal direction, which is the main scanning direction. Immediately before the start of this horizontal scanning, a part of the light beam emitted from the toric lens 26 is reflected by the reflection mirror 29, passes through the auxiliary lens 30 and the slit 31, enters the photoelectric conversion element 32, and the light beam generated in the photoelectric conversion element 32 The electric signal is received by the DC controller 33, and after a certain period of time, the modulation circuit 3
5 generates a signal to start modulating the light beam. Here, the photoelectric conversion element 32 disposed outside the optical case 21 can be attached and replaced if necessary by removing the substrate 36 while remaining in a sealed state with the auxiliary lens 30.

In the above-described embodiment, the auxiliary lens 30 is press-fitted into the optical case 21, but the two may be integrally molded or the auxiliary lens 30 may be insert molded into the optical case 21.

FIG. 3 shows a perspective view of the second embodiment, in which thermoplastic resin is used as the material for the auxiliary lens 37, which is integrally molded with the optical case 21. By integrally molding in this manner, ease of assembly is improved, and failures due to the auxiliary lens 37 coming off or being misaligned are less likely to occur.

[0014]

Effects of the Invention As explained above, the scanning optical device according to the present invention uses an auxiliary lens to seal the optical case and arranges the photodetection element outside of the optical case, thereby detecting light without opening the optical case. Elements can be installed and replaced, and there is almost no risk of dust entering the optical case.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a perspective view of the main parts of the first embodiment.

FIG. 3 is a perspective view of the main parts of the second embodiment.

FIG. 4 is a configuration diagram of a conventional example.

[Explanation of symbols]

21 Optical case 22 Light source unit 24 Rotating polygon mirror 28 Photosensitive drum 29 Reflection mirror 30, 37 Auxiliary lens 31 Slit 32 Photoelectric conversion element 36 Board

Claims (1)

[Claims] 1. In the case where a light beam deflection and scanning means is provided in an optical case and a part of the deflected light beam is irradiated onto a photodetecting element through an auxiliary lens to obtain a synchronization signal, the auxiliary lens is attached to the optical case. 1. A scanning optical device comprising a part of a sealed structure of the optical scanning device, wherein the photodetecting element is disposed outside the optical case.