JPH04130410A - Scanning optical system - Google Patents

Abstract

PURPOSE:To accomplish accurate position detection by returning reflected light from a reflection mirror disposed in a position detection means to a semiconductor laser light beam source. CONSTITUTION:Incident light 11 on the reflection mirror 12a out of laser light beam which scans a photosensitive body 1 is vertically reflected, advances in a reverse direction through a path which it traces hitherto, and is returned to a semiconductor laser 9. Since the laser 9 and the reflection mirror 12a are located at optically conjugate positions, special accuracy other than the accuracy of an angle around an axis vertical to the scanning plane of the reflection mirror is not needed. In the case that the light which is emitted by the laser 9 itself is returned to the laser 9 in the middle of exciting and emitting light, the interference phenomenon of the light is caused in the laser 9 and the fluctuation of optical output occurs. When the optical output is to be kept constant, the change of a driving current occurs. By grasping this change, it is detected when the light of its own is returned. Thus, the accurate position detection is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a scanning optical system, and more particularly to an isotram surface scanning optical system used in a laser printer.

[Conventional technology]

Conventionally, this type of scanning optical system has had a configuration as shown in FIG. That is, one of the laser beams emitted from both ends of the semiconductor laser 9 enters the optical power sensor 10, is input as an electrical signal to the optical power detection circuit 8, and is converted into a signal for controlling the laser drive circuit 7. The laser drive circuit controls the current that drives the semiconductor laser 9, and performs feedback control to obtain a constant optical output when the semiconductor laser 9 emits light.

The other laser beam emitted from the semiconductor laser 9 enters a collimating lens 6 and is converted into parallel light, then passes through a cylinder lens 5 and is deflected and scanned by a polygon mirror 3 rotated at high speed by a motor 4. be done. Then, the deflected laser light becomes plane imaging light that is scanned at a constant speed by the f-theta lens 2 and is irradiated onto the photoreceptor 1. At this time,
Among the scanning laser beams, incident light 11 on the reflecting mirror 12
Yes! It is reflected in the direction of the detection slit 13.

When the laser beam enters from the slit 13 for a short time, an electrical signal is sent from the optical power sensor 14 to the scanning timing detection circuit 15, and the scanning timing detection circuit 15 outputs a timing pulse 16. and a control unit (not shown)
In synchronization with this timing pulse 16, a laser ○N10FF signal 17 is applied to the laser drive circuit 7 to form an electrostatic latent image on the photoreceptor 1.

[Problem to be solved by the invention]

In conventional scanning optics, special position detection slits,
It was impossible to detect the scanning position without providing an optical power sensor, a timing detection circuit, etc. Furthermore, the optical positional relationship between the reflecting mirror and the slit must be maintained with high precision, resulting in an increase in cost. Also,
If this accuracy is low, there is a drawback that light may not enter the optical power sensor, or timing pulses may not be generated due to temperature distortion, changes over time, etc., and the timing may change.

[Means to solve the problem]

The present invention includes a semiconductor laser light source, a detection means for detecting the intensity of the laser light emitted from the laser light source, a lens for converting the laser light into parallel light, a scanning means for deflecting the parallel light, and the scanning means. An optical scanning system comprising a position detecting means for detecting the position of a scanned light beam, wherein the position detecting means is provided with a reflecting mirror, and the reflected light from the reflecting mirror is returned to the semiconductor laser light source. It is characterized by what it did.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the invention.

In FIG. 1, one of the laser beams emitted from both ends of the semiconductor laser 9 enters the optical power sensor 10, is inputted as an electrical signal to the optical power detection circuit 8, and is converted into a signal for controlling the laser drive circuit 7. Ru. The laser drive circuit 7 controls the current that drives the semiconductor laser 9, and performs feedback control to obtain a constant optical output when the semiconductor laser 9 emits light.

The other laser beam emitted from the semiconductor laser 9 enters a collimating lens 6 and is converted into parallel light, then passes through a cylinder lens 5 and is deflected and scanned by a polygon mirror 3 rotated at high speed by a motor 4. be done. Then, the deflected laser light becomes plane imaging light that is scanned at a constant speed by the f-theta lens 2 and is irradiated onto the photoreceptor 1. Further, a reflection mirror 12a for position detection is installed on the same image plane as the photoreceptor 1. Here, among the laser beams scanning the photoreceptor 1, the incident light 11 on the reflecting mirror 12a is vertically reflected and travels in the opposite direction along the path that has been followed thus far and returns to the semiconductor laser 9. Here, the semiconductor laser 9 and the reflection mirror 12
Since the position is optically conjugate with a, no special accuracy is required except for the angular accuracy around the axis perpendicular to the scanning plane of the reflecting mirror. Furthermore, if two mutually orthogonal opposed corner mirrors are used instead of the reflecting mirror 12, the angles around the axis perpendicular to the scanning plane do not require high precision. The laser beam scanned by such means is returned to the semiconductor laser 9 only while the reflecting mirror 12a is irradiated with the laser beam.

By the way, when the semiconductor laser 9 returns its own emitted light during excitation emission, a light interference phenomenon occurs and the optical output fluctuates. Then, when trying to keep the optical output constant, a change occurs in the drive current. By capturing this change, it is possible to detect when its own light is returned. Alternatively, it is also possible to detect changes in the returned light by the optical power sensor 10, and this change can be used as a scanning position detection signal.The optical power detection circuit 8a also functions as a scanning position detection means and generates timing pulses. Outputs 18. Then, the control section (not shown) provides a laser ○N/○FF signal 17 to the laser drive circuit 7 in synchronization with this timing 18 to form an electrostatic latent image on the photoreceptor 1.

〔Effect of the invention〕

According to the present invention, highly accurate position detection is possible without providing a special optical sensor, slit, etc. for position detection, and cost reduction is possible. Further, there is an effect that it is possible to achieve highly stable position detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional example. 1... Photoreceptor, 2... f-theta lens, 3.1. Polygon mirror, 4...Motor, 5...Cylinder lens, 6...Collimating lens, 7...Laser drive circuit,
8゜8a... Optical power detection circuit, 9... Semiconductor laser, 10.14... Optical power sensor, 11... Incident light,
12.12a...Reflection mirror, 13...Slit,
15...Scanning timing detection circuit, 16.18...
Timing pulse, 17...Laser 0N10FF signal.

Claims (1)

[Claims] A semiconductor laser light source, a detection means for detecting the intensity of the laser light emitted from the laser light source, a lens for converting the laser light into parallel light, a scanning means for deflecting the parallel light, and a light beam scanned by the scanning means. and a position detection means for detecting the position of the optical scanning system, characterized in that a reflecting mirror is disposed in the position detection means, and the reflected light from the reflection mirror is returned to the semiconductor laser light source. scanning optical system.