JP2011221417A - Optical-scanning optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optical-scanning optical apparatus capable of causing, to be substantially equal to each other, the difference between volumes of light incident to two pieces of optical detection means, the incident light being the basis of synchronous signals, to cause the accuracy of the generated synchronous signals to be substantially the same.SOLUTION: The optical-scanning optical apparatus includes: first and second laser diodes 1A and 1B for emitting first and second luminous fluxes; first and second light source optical systems 2A and 2B for shaping the first and second luminous fluxes respectively; a single polygon mirror 5 for deflecting the first and second luminous fluxes in a main scanning direction Y; first and second scanning optical systems 6A and 6B for image-forming, onto different photoreceptors, the first and second luminous fluxes deflected by the polygon mirror 5; and first and second optical detection means 10A and 10B for detecting first and second luminous fluxes deflected by the polygon mirror 5 in order to obtain synchronous signals in the main scanning direction Y. The first and second luminous fluxes are incident to the polygon mirror 5 at different angles. The synthetic reflectance of the reflectance of the polygon mirror 5 and the reflectance of the mirror 12A against the first luminous flux is set to be substantially equal to the reflectance of the polygon mirror 5 against the second luminous flux.

Description

  The present invention relates to an optical scanning optical device, and more particularly to an optical scanning optical device mounted as an image writing unit in an image forming apparatus such as an electrophotographic copying machine or printer.

  In recent years, in full-color image forming apparatuses such as laser printers, an electrostatic latent image is formed by scanning light beams modulated based on image data on a plurality of photoconductors arranged side by side. A tandem method is employed in which the toner image developed in step 4 is finally synthesized and transferred onto a recording sheet.

  2. Description of the Related Art Conventionally, as an optical scanning optical device mounted on a tandem printer, there is an optical scanning device that deflects and scans a plurality of light beams in a reverse direction by a single deflector, as described in Japanese Patent Application Laid-Open No. 2003-133260. In this type of optical scanning optical device, a light detection sensor for controlling the synchronization signal in the main scanning direction on one deflection scanning side and a light detection for controlling the synchronization signal in the main scanning direction on the other deflection scanning side. The sensor is arranged.

  By the way, if the reflection angle of the optical element is different, the reflectance is different, and the reflectance affects the energy of the reflected light beam. Therefore, if there is a difference in light energy between the light detection sensor arranged on one deflection scanning side and the light detection sensor arranged on the other deflection scanning side, a difference occurs in the detection accuracy of the synchronization signal, and consequently It becomes difficult to form a high-quality image.

  That is, as shown in FIGS. 6 and 7, the light detection sensor 50 is a photodiode 52 provided on a substrate 51, and a current I and a voltage E are generated when a light beam crosses the light receiving region 53. When the reference voltage L is exceeded, the synchronization signal M is generated. After a predetermined time T has elapsed from the synchronization signal M, light source modulation is started (image writing is started). If there is a difference in the light energy incident on the light detection sensor 50, the rise of the detection voltage E varies, so that a difference occurs in the reference timing T1 of the synchronization signal M, and consequently the image writing start timing SOI varies.

JP 2002-137450 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning optical device that can substantially equalize the difference in the amount of incident light with respect to two photodetecting means that is the basis of a synchronization signal, and can substantially equalize the accuracy of generation of the synchronization signal. is there.

An optical scanning optical device according to an aspect of the present invention is
A first light source that emits a first light flux and a second light source that emits a second light flux;
First and second light source optical systems for shaping the first and second light beams, respectively;
A single deflector for deflecting each of the first and second light beams in the main scanning direction;
First and second scanning optical systems for forming images of the first and second light beams deflected by the deflector on different photoreceptors;
First and second light detecting means for detecting first and second light beams deflected by the deflector to obtain a synchronization signal in the main scanning direction;
In an optical scanning optical device comprising:
The first and second light beams are incident on the deflector at different angles,
The combined reflectivity of the reflectivity of the deflector with respect to the first light flux and the reflectivity of the reflective optical element disposed in the optical path from the first light source to the first light detection means, and the deflector of the deflector with respect to the second light flux. The total reflectance of the reflectance or the reflectance of the deflector and the reflectance of the reflective optical element arranged in the optical path from the second light source to the second light detection means is substantially equal;
It is characterized by.

  In the optical scanning optical device, a combined reflectance of the reflectivity of the deflector with respect to the first light flux and the reflectivity of the reflective optical element disposed in the optical path from the first light source to the first light detection unit; The reflectance of the deflector with respect to the second light flux or the total reflectance of the reflectance of the deflector and the reflectance of the reflective optical element disposed in the optical path from the second light source to the second light detection means, It is set approximately equal. Therefore, the energies of the light beams incident on the first and second light detection means are substantially equal, and the synchronization signal generation accuracy is substantially equal.

  According to the present invention, the difference in the amount of incident light with respect to the first and second photodetecting means that is the basis of the synchronization signal can be made substantially equal, the accuracy of the synchronization signal generation can be made substantially equal, and the image quality is improved.

1 is a schematic plan view showing an optical scanning optical device according to a first embodiment. It is a schematic plan view which shows the optical scanning optical apparatus which is 2nd Example. It is a graph which shows the reflectance with respect to the incident angle in a 1st reflective surface (Al single layer coating). It is a graph showing the reflection of the incident angle at the second reflecting surface (Al + SiO ₂ coating). Is a graph showing the reflection of the incident angle of the third reflecting surface (Al + SiO ₂ + TiO ₂ coating). It is explanatory drawing of a photon detection sensor. It is a chart figure which shows the production | generation process of a synchronizing signal.

  Embodiments of an optical scanning optical device according to the present invention will be described below with reference to the accompanying drawings. In each figure, common parts and portions are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 1, the optical scanning optical apparatus according to the first embodiment includes first and second laser diodes 1A and 1B as light sources that emit first and second light beams, and first and second light beams. First and second light source optical systems 2A and 2B for shaping, a single polygon mirror 5 for deflecting the first and second light beams in the main scanning direction Y, respectively, and first and first deflected by the polygon mirror 5 First and second scanning optical systems 6A and 6B for imaging two light beams on a photoconductor (not shown), and first and second light beams deflected by the polygon mirror 5 to obtain a synchronization signal in the main scanning direction Y The first and second light detection sensors 10A and 10B to detect.

  The first and second light source optical systems 2A and 2B are configured by collimator lenses 3A and 3B and cylindrical lenses 4A and 4B. The first and second scanning optical systems 6A and 6B are composed of first scanning lenses 7A and 7B, second scanning lenses 8A and 8B, and an optical path bending mirror (not shown). In addition, condenser lenses 11A and 11B are disposed immediately before the first and second light detection sensors 10A and 10B, and a mirror 12A is disposed in the optical path leading to the first light detection sensor 10A.

  The optical scanning optical apparatus according to the second embodiment has the same basic components as those of the first embodiment except that the arrangement of the first light detection sensor 10A and the second light detection sensor 10B are different. The provision of the mirror 12B and the reflection angles of the respective reflective optical elements are described in detail below.

  In the first and second embodiments, the first light beam (diverging light) emitted from the first laser diode 1A is shaped into parallel light by the collimator lens 3A and condensed in the sub-scanning direction Z by the cylindrical lens 4A. Then, the light enters the polygon mirror 5 and is deflected at a constant angular velocity in the main scanning direction Y. The deflected first light beam is exposed / scanned in a state of being imaged on a first photoconductor (not shown) via the first and second scanning lenses 7A and 8A. Further, the first light beam on the start end side in the main scanning direction Y that is incident on the polygon mirror 5 at the angle α1 and reflected at the angle α1 is reflected by the mirror 12A (incident angle and reflection angle is α2), and the condenser lens 11A. Through the first light detection sensor 10A.

  The second light beam (diverged light) emitted from the second laser diode 1B is shaped into parallel light by the collimator lens 3B, condensed in the sub-scanning direction Z by the cylindrical lens 4B, and incident on the polygon mirror 5. Deflection is performed at a constant angular velocity in the main scanning direction Y. The deflected second light beam is exposed / scanned in a state of being imaged on a second photoconductor (not shown) via the first and second scanning lenses 7B and 8B. The second light beam incident on the polygon mirror 5 at an angle β1 and reflected at the angle β1 on the start end side in the main scanning direction Y enters the second light detection sensor 10B via the condenser lens 11B in the first embodiment. In the second embodiment, the light is reflected by the mirror 12B (the incident angle and the reflection angle are β2) and enters the second light detection sensor 10B via the condenser lens 11B.

  In the first embodiment, the combined reflectance of the reflectance of the polygon mirror 5 with respect to the first light flux and the reflectance of the mirror 12A and the reflectance of the polygon mirror 5 with respect to the second light flux are set to be approximately equal. In the second embodiment, the combined reflectance of the reflectance of the polygon mirror 5 and the reflectance of the mirror 12A with respect to the first light flux, and the reflectance of the polygon mirror 5 and the reflectance of the mirror 12B with respect to the second light flux. The total reflectance is set to be approximately equal.

Here, with respect to the reflective optical element, the simulation results of the reflectance with respect to the incident angle are shown in FIG. 3, FIG. 4, and FIG. In the simulation, the reflectance with respect to the incident angle was calculated for each polarization component (S-polarized light and P-polarized light) having a wavelength of 780 nm. The average value of both polarization components was also calculated. Figure 3 is a simulation result of the reflection surface that is a single layer coated with Al, FIG. 4 is a simulation result of the reflection surface two layers coated with the Al and SiO _2, in FIG. 5 is Al and SiO ₂ and the TiO ₂ It is a simulation result in the reflective surface which carried out 3 layer coating.

  As apparent from FIGS. 3, 4 and 5, on each reflecting surface, the reflectance tends to increase with an increase in the incident angle in the S-polarized light, and decreases 80 ° in the P-polarized light (70 in FIG. 4). It tends to rise when it exceeds (°). In a general reflective optical system, the S-polarized light and the P-polarized light are determined by the angle of the polarization direction with respect to the incident surface. If the polarization direction is parallel to the incident surface, the S-polarized light and P-polarized light are P-polarized light. In the first and second embodiments, the polarization component of the light beam is only S-polarized light depending on the tilt angles of the laser diodes 1A and 1B. Therefore, the specific numerical values described below refer to the value of the S-polarized light component. The reflective surface refers to the value of the Al single layer coating.

  In the first embodiment, the incident angle α1 is 70 ° and the reflectance is 0.953. The incident angle α2 is 60 ° and the reflectance is 0.932. Therefore, the combined reflectance is 0.953 × 0.932 = 0.888. On the other hand, the incident angle β1 is 30 ° and the reflectance is 0.870. Both reflectivities are 0.888 and 0.870, which are substantially equal. Therefore, the energies of the light beams incident on the first and second photodetection sensors are substantially equal, and the synchronization signal generation accuracy is substantially equal.

  In the second embodiment, the incident angle α1 is 60 ° and the reflectance is 0.932. The incident angle α2 is 10 ° and the reflectance is 0.870. Therefore, the combined reflectance is 0.932 × 0.870 = 0.711. On the other hand, the incident angle β1 is 10 ° and the reflectance is 0.870. The incident angle β2 is 60 ° and the reflectance is 0.932. Therefore, the total reflectance is 0.870 × 0.932 = 0.711. Both reflectivities are 0.888 and 0.870, which are substantially equal. Therefore, the energy of the light beams incident on the first and second light detection sensors 10A and 10B are equal, and the accuracy of the synchronization signal generation is equal.

  By the way, in the second embodiment, the first and second sides are divided into one side C1 and the other side C2 with respect to the central optical axis C of the first and second light beams deflected by the polygon mirror 5. The two diodes 1A and 1B and the first and second light detection sensors 10A and 10B are disposed on one side C1. Thus, in the second embodiment, the planar exclusive area of the optical scanning optical device can be reduced.

(Other examples)
The optical scanning optical device according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  For example, the configuration and arrangement of the first and second light source optical systems and the first and second scanning optical systems are arbitrary. In the tandem image forming apparatus, four light beams are scanned simultaneously. In this case, two laser beams may be radiated from each laser diode, or two laser diodes may be arranged and the two light beams may be combined in the traveling direction and incident on the polygon mirror. . Further, one photoconductor may be exposed / scanned simultaneously with a plurality of light beams. In this case, one of a plurality of light beams scanned at the same time may be used to detect the synchronization signal.

  As described above, the present invention is useful for an optical scanning optical apparatus, and is particularly excellent in that the accuracy of synchronization signal generation can be made substantially equal.

DESCRIPTION OF SYMBOLS 1A, 1B ... Laser diode 2A, 2B ... Light source optical system 5 ... Polygon mirror 6A, 6B ... Scanning optical system 10A, 10B ... Photodetection sensor 12A, 12B ... Mirror α1, α2, β1, β2 ... Reflection angle Y ... Main scanning direction

Claims (3)

A first light source that emits a first light flux and a second light source that emits a second light flux;
First and second light source optical systems for shaping the first and second light beams, respectively;
A single deflector for deflecting each of the first and second light beams in the main scanning direction;
First and second scanning optical systems for forming images of the first and second light beams deflected by the deflector on different photoreceptors;
First and second light detecting means for detecting first and second light beams deflected by the deflector to obtain a synchronization signal in the main scanning direction;
In an optical scanning optical device comprising:
The first and second light beams are incident on the deflector at different angles,
The combined reflectivity of the reflectivity of the deflector with respect to the first light flux and the reflectivity of the reflective optical element disposed in the optical path from the first light source to the first light detection means, and the deflector of the deflector with respect to the second light flux. The total reflectance of the reflectance or the reflectance of the deflector and the reflectance of the reflective optical element arranged in the optical path from the second light source to the second light detection means is substantially equal;
An optical scanning optical device.   The optical scanning optical apparatus according to claim 1, wherein the first and second light beams are deflected and scanned in opposite directions by the deflector.   The first and second light sources and the first and second light detecting means are arranged on one side with respect to the central optical axes of the first and second light beams deflected by the deflector. The optical scanning optical device according to claim 1 or 2.

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