JPH0415613A - Laser beam scanning position detection structure - Google Patents

Abstract

PURPOSE:To decrease the number of components and simplify the structure, to facilitate the assembling operation, and to reduce the cost by arranging a photodetecting element in a laser beam scanning range and detecting a scanning laser beam directly. CONSTITUTION:A laser oscillator 10 is arranged in the laser beam scanning range of a reflecting and deflecting means 1 and a laser beam scanning position detection sensor 6 which detects the scanning laser beam is arranged in the laser beam scanning range on a scanning start side about a utilization scanning range across the laser oscillator 10. Consequently, the number of components can be decreased, the constitution is simplified, and the cost is reducible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser scanning optical system that scans a laser beam from a laser oscillator used in a laser beam printer or the like over a predetermined angle range by moving a reflecting means. The present invention relates to a laser beam scanning position detection structure that detects the scanning position of a laser beam in order to use it as a reference for starting laser beam modulation.

[Prior Art] Recently, a laser beam modulated based on image information such as a single graphic character is used to expose and scan a charged photoreceptor (photoreceptor drum) to form an electrostatic latent image, which is then developed (photoreceptor). Copying processes such as imaging), transfer, and fixing (so-called electrophotographic copying processes)
Image forming devices such as laser printers, which obtain a hard copy of image information on recording paper through photosensitive printing, and laser photoplotters, which scan the surface of a photosensitive material with a laser beam to draw a pattern on an original plate such as a printed circuit board, are becoming popular. .

Various methods have been considered for deflecting and scanning the laser beam, and the most common method is to move (change the angle) a mirror surface that reflects the laser beam, such as a rotating polygon mirror or a galvanometer.

An example of a deflection scanning optical system for deflecting and scanning such a laser beam is shown in FIGS. 4 and 5.

The illustrated deflection scanning optical system is used in a laser printer, and reflects the laser beam LB emitted from the semiconductor laser 10 by a plurality of reflective surfaces IA formed on the side peripheral surface of the polygon mirror 1. The laser beam LB changes due to the angle change of the reflecting surface IA due to the rotation of the polygon mirror 1.
This is to scan.

In a laser printer, it is necessary to modulate the laser beam LB in synchronization with the scanning, so the laser beam LB at the end of the scanning range, which does not contribute to image formation, is sent to the light receiving element 6.
The laser beam detection signal from the light receiving element 6 is used as a horizontal synchronization signal. In other words,
The scanning position of the laser beam LB is grasped by the laser beam detection by the light receiving element 6, and based on this, the photosensitive tram 3
Drawing starts from a predetermined position above.

In order to detect the scanning position of the laser beam LB with high precision, it is desirable to arrange the light receiving element 6 at a position optically equivalent to the laser beam scanning surface (the surface of the photosensitive drum 3), and the scanning optical system shown in FIG. , a reflective member (
A laser beam position detection mirror 5) is disposed, and the mirror 5 reflects the scanning laser beam LB and guides it to the light receiving element 6. The optical path length of the laser beam is set to be approximately equal to the optical path length of the laser beam.

The semiconductor laser 10 and the light receiving element 6 are respectively mounted on substrates 13 and 61.
The substrate 1 is fixed to a base member (not shown) of the scanning optical system while being attached to the substrate 1, and a semiconductor laser IO is attached thereto.
3 includes a drive circuit 21 for driving the semiconductor laser IO and a light emission stabilization circuit 22 for feedback controlling the laser output, and a synchronization signal detection circuit 23 for the substrate 61 on which the light receiving element 6 is mounted. It is something that

In the scanning optical system shown in FIG. 5, a light receiving element 6 is provided on a substrate 20 of a control device that controls the operation of the scanning optical system, and a laser beam at a predetermined scanning position is guided to the light receiving element 6 by an optical fiber half. It is composed of According to this configuration, the synchronization signal detection circuit is connected to the board 2 of the control device.
Compared to the configuration shown in FIG. 4, there is no need for a dedicated board for the light receiving element 6 (it comes together with the control device board), and its installation is also easier. It has the advantage of becoming a cost town.

Note that 2 in Figure 1 is the laser beam LB produced by the polygon mirror 1.
An fθ lens is provided to correct the scanning speed of the laser beam LB so that the surface of the photosensitive drum 3 is scanned at a speed proportional to the deflection angle of This is a cylindrical lens that focuses the laser beam LB into a line perpendicular to the rotation axis of the polygon mirror 1.

[Problems to be Solved by the Invention] However, the laser beam scanning position detection configuration shown in $41 above has a structure with a large number of parts because the mirror for laser beam position detection and the light receiving element are provided independently. It is also complicated, and the parts must be installed with high precision, resulting in high parts and assembly costs.

In addition, compared to the configuration shown in FIG. 4, the configuration shown in FIG. There was a problem in that the laser beam detection accuracy deteriorated due to the decrease in the amount of light caused by the introduction of the laser beam.

[Purpose of the Invention] This invention has been made in view of the above-mentioned background, and an object thereof is to provide a laser beam scanning position detection structure that can simplify the configuration and reduce costs. .

[Means for Solving the Problems] Therefore, in the laser beam scanning position detection device according to the present invention, the laser oscillator is placed within the laser beam scanning range by the reflective deflection means, and the laser beam scanning position detecting device detects the scanning laser beam. The position detection sensor is arranged within a laser beam scannable range on the scanning start side, which is separated from the laser oscillator with respect to the usable scanning range.

Further, a semiconductor laser and a laser beam scanning position detection sensor are mounted and arranged on the same substrate.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a diagram schematically showing the configuration of a scanning optical system used in a laser printer device to which an embodiment of the laser beam scanning position detection configuration according to the present invention is applied. A laser printer device is used as an external output device for a computer, etc., and prints the surface of a cylindrical photosensitive drum in the axial direction of the photosensitive drum using a laser beam that is turned on and off based on drawing information separated into dots. scan (main scan)
At the same time, the photosensitive tram 1 is rotated (sub-scanning), and toner is transferred (drawn) onto recording paper by electrophotography and output.

The illustrated scanning optical system includes a polygon mirror 1, which is a reflective deflection means, to scan a photosensitive tram 3 with a laser beam LB from a semiconductor laser 10. fθ lens 2. It is constructed by arranging a cylindrical lens 4 and a semiconductor laser 10 at a predetermined positional relationship. That is, the semiconductor laser IO is arranged so as to emit the laser beam LB at a predetermined angle toward the polygon mirror 1, and a direction perpendicular to the rotation axis of the polygon mirror 1 is arranged between the semiconductor laser IO and the polygon mirror 1. A cylinder lens 4 is arranged in the direction of the cylinder axis, and a polygon mirror 1
An fθ lens 2 is installed between the photosensitive tram 3 and the photosensitive tram 3.

Here, the semiconductor laser 10 can scan a predetermined range on the photosensitive tram 3 with respect to the polygon mirror 1 by changing the angle of the reflection surface IA due to the rotation of the polygon mirror 1 or the laser beam LB emitted from the semiconductor laser IO. and is arranged on the scanning start side, and the laser beam LB scanning range is set to extend from the semiconductor laser 10 arrangement position to the scanning start side. In other words, the scanning range of the laser beam LB is a range that includes a predetermined range on the photosensitive tram 3 from before the position of the semiconductor laser 10 through the position of the semiconductor laser IO.

As shown in FIG. 2, which is a cross-sectional view corresponding to II-II in FIG. It is positioned and fixed to a base member (not shown) of the scanning optical system by a provided Holter 14, and a light receiving element 6 for detecting the laser beam is also mounted on the substrate 13 on which the semiconductor laser IO is mounted. ing.

The light-receiving element 6 is placed on the substrate 13 so that when the semiconductor laser 10 (substrate 13) is positioned and fixed, the laser beam LB on the scanning start side from the semiconductor laser 10 position is scanned.
is installed on.

Therefore, the light-receiving element 6 is scanned by the laser beam LB on the scanning start side from the position of the semiconductor laser 10, or the light-receiving element 6 is scanned by the laser beam LB in the optical path along the mm-m cross section in FIG. As shown in FIG. 3, a correction sensor 8 for laser beam detection is provided.

The laser beam detection correction sensor 8 has a predetermined positive power in the laser beam scanning direction, and also has a predetermined positive power in the sub-scanning direction orthogonal to the main scanning direction, which is different from the main scanning direction. It is a lens molded from optical plastic that focuses the laser beam in the main scanning direction and sub-scanning direction to satisfy the power density necessary for detection by the light receiving element, and also detects by tilting the reflective surface IA of the polygon mirror l. It functions to eliminate any influence on accuracy.

The substrate 13 includes a laser drive circuit 21. Output stabilization circuit (
APC circuit) 22 and horizontal synchronization detection circuit 23 are constructed. The APC circuit 22 stably controls the emission output of the semiconductor laser 10, which is highly temperature dependent, and is a monitor that detects the laser beam from one side (the rear side) of the laser tie-out 11 that emits a laser beam in two directions, front and rear. This circuit performs feedback control of the output of the phototype autograph 12 to the laser drive circuit.

According to the above configuration, the laser beam LB emitted from the semiconductor laser 1O and scanned by the polygon mirror 1 or the light receiving element 6 at a predetermined position on the photosensitive tram 3 prior to scanning a predetermined range. is scanned, and a horizontal synchronization signal is obtained by a horizontal synchronization detection circuit based on a laser beam detection signal from the light receiving element 6.

In this embodiment, the semiconductor laser 10 and the light receiving element 6 are mounted on the same substrate 13, and the light receiving element 6 is placed at a position where the scanning laser beam scans (in other words, the position of the light receiving element 6 is scanned). By setting the laser beam to scan), the semiconductor laser 10 and the light-receiving element 6, which were conventionally required to each have separate substrates, can be constructed in one piece, and the mirror that guides the laser to the light-receiving element 6 is no longer necessary. Further, since the semiconductor laser 10 and the light receiving element 6 must be mounted on the heath member (not shown) once, which requires assembly precision, the reduction in the number of parts and the ease of assembly result in increased costs.

In the above embodiment, the semiconductor laser IO and the light receiving element 6 may be mounted on the same substrate, or may be constructed by mounting them on separate substrates. Although this increases the number of substrates, it is also possible to set the optical path length of the laser beam reaching the light receiving element 6 to be approximately equal to the optical path length of the laser beam reaching the surface of the photosensitive drum 3.

[Effects of the Invention] As explained above, according to the laser beam scanning position detection device according to the present invention, the light receiving element is arranged within the laser beam scanning range to directly detect the scanning laser beam, thereby achieving the following effects. There is no need for a mirror for detecting the position of the laser beam that guides the scanning laser beam at the end of the scanning range to the light receiving element, and costs can be reduced by reducing the number of parts, simplifying the structure, and facilitating assembly work.

In addition, stable and highly accurate detection is possible without a decrease in the amount of light.

Furthermore, according to the invention according to claim (2), the circuits related to driving the semiconductor laser and detecting the laser beam position can be configured on the same substrate, and the cost can be further reduced by reducing the number of parts and simplifying the circuit. It is something that can be planned around town.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the configuration of a scanning optical system to which an embodiment of the laser beam scanning position detection structure according to the present invention is applied, and FIG. 2 is a cross-sectional view corresponding to II-II in FIG. 1, W43I
2I is a cross-sectional view taken along line mm in FIG. 1, and FIGS. 4 and 5 are diagrams schematically showing the configuration of a conventional scanning optical system. l... Polygon mirror (reflection deflection means) lO... Semiconductor laser (laser oscillator) 13... Substrate

Claims (2)

[Claims] (1) In a laser scanning optical system that scans a laser beam from a laser oscillator in a predetermined angular range by moving a reflective deflection means, the laser oscillator is disposed within a range in which the laser beam can be scanned by the reflective deflection means, and the laser beam is scanned by the reflective deflection means. Laser beam scanning position detection characterized in that a laser beam scanning position detection sensor for detecting the laser beam is arranged within the laser beam scanning possible range on the scanning start side, which is separated from the laser oscillator with respect to the usable scanning range. structure. (2) The laser beam scanning position detection structure according to claim 1, wherein the laser oscillator and the laser beam scanning position detection sensor are mounted on the same substrate.