JP2001324687A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of restraining generation of electric noise and improving the adjusting accuracy of the focal position of a light beam on a surface to be scanned. SOLUTION: A detection part 8 detects the formed image state of the light beam formed into an image by an image forming element 6, and a control part 10 arithmetically calculates the moving amount of correction lenses 3 and 4 in an optical axis direction based on a signal from the detection part 8. The control part 10 is equipped with a detecting element part 30, a counter 31, an amplifier circuit part 32 amplifying the signal from the detection part 8, a differentiation circuit 33, an A/D(analog/digital) conversion part 34 converting an analog signal into a digital signal, a CPU(central processing unit) 40 performing arithmetic processing and a driving part 41 for driving the correction lens. The detection part 8 and the control part 10 are formed adjacently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical scanning device, and more particularly, to an optical scanning device used for a writing optical system such as a digital PPC and a laser printer.

[0002]

2. Description of the Related Art In recent years, optical scanning apparatuses have been widely used in image forming apparatuses such as measuring instruments, inspection apparatuses, digital copiers and laser printers. With the increase in the density of the optical scanning device, it is desired to reduce the beam spot diameter on the surface to be scanned (photoconductor). However, when the beam spot diameter is 30μ
If it is narrowed down to the m level, the depth of the focus store can only be about 1 mm, and the precision of parts and assembly is severe. Therefore, conventionally, various methods have been proposed for adjusting the focal position by detecting the imaging state of the laser beam.

[0003] By the way, Japanese Patent No. 2761723 discloses that
When a laser beam that blinks according to an image signal is received, an appropriate spot diameter is obtained according to a difference between a maximum output value and a minimum output value of an output value output by the photoelectric conversion element receiving the laser beam. Thus, a scanning optical device that adjusts the position of a collimator lens is described. In addition, Japanese Patent Application Laid-Open
Japanese Patent Application Publication No. 20225 describes a laser beam scanning optical device that drives an optical element based on a result of a detection unit that detects that a scanned laser beam has passed, and adjusts a focusing position of the laser beam. .

[0004]

However, the above-mentioned Japanese Patent No. 2761723 and Japanese Patent Application Laid-Open No. 10-20225 are not disclosed.
In the optical scanning device proposed in Japanese Patent Application Laid-Open Publication No. H11-270, electrical noise is likely to occur because the detection unit and the control unit are spatially separated. In addition, when detecting the imaging state of the light beam, since the scanning light beam is detected, if the scanning frequency is increased by increasing the printing speed, the response speed of the detection means is increased accordingly, and the scanning frequency is increased. At higher frequencies, detection accuracy was liable to deteriorate due to noise and the like. Furthermore, when the scanning pitch is detected by the optical scanning device when the light source emits a plurality of light beams, the light beam being scanned is detected. The response speed of the means must be increased, and when the scanning frequency is high and the frequency is high, the detection accuracy tends to deteriorate due to the influence of noise and the like.

Therefore, a first object of the present invention is to provide an optical scanning device capable of suppressing the generation of electrical noise and improving the accuracy of adjusting the focal position of a light beam on a surface to be scanned. It is to be. A second object of the present invention is to provide an optical scanning device capable of forming a light source with an LD array that emits a plurality of light beams or a multi-beam obtained by combining a plurality of LDs.

[0006]

According to the present invention, a light source for emitting a light beam, scanning means for deflecting the light beam emitted from the light source and condensing it on a surface to be scanned, A focus position detecting means for detecting a focus position of the light beam scanned by the scanning means on the surface to be scanned on the surface to be scanned; and a signal relating to the focus position detected by the focus position detecting means. Adjusting means for adjusting the focal position of the light beam based on the result, wherein the focal point detecting means and the adjusting means are formed adjacent to each other, thereby achieving the first object.

According to a second aspect of the present invention, in the first aspect of the invention, the light source emits a plurality of light beams to achieve the second object.

According to the third aspect of the present invention, a light source that emits a plurality of light beams, scanning means for deflecting the light beam emitted from the light source and condensing it on a surface to be scanned, and scanning by the scanning means Scanning pitch detecting means for detecting a scanning pitch of the plurality of light beams on the surface to be scanned, and a signal relating to the scanning pitch detected by the scanning pitch detecting means. The first object is achieved by providing an adjusting unit for adjusting the scanning pitch, wherein the scanning pitch detecting unit and the adjusting unit are formed adjacent to each other.

According to a fourth aspect of the present invention, a light source for emitting a plurality of light beams, scanning means for deflecting a light beam emitted from the light source and condensing it on a surface to be scanned, and scanning by the scanning means Detecting means for detecting a focal position of an imaged state of the light beam on the surface to be scanned and a scanning pitch of the light beam scanned by the scanning means on the surface to be scanned; and Adjusting means for processing the signal relating to the focal position and the signal relating to the scanning pitch, and adjusting the focal position and the scanning pitch of the light beam based on the computation result, wherein the detecting means and the adjusting means are adjacent to each other. The first object is achieved by being formed as described above.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a diagram illustrating an overall configuration of the optical scanning device according to the first embodiment, and FIG. 2 is a diagram illustrating an overall configuration of the optical scanning device according to the second embodiment. The optical scanning device according to the first embodiment includes a deflector 5, an imaging element 6, a surface to be scanned 7, a detection unit 8, an LD (semiconductor laser) unit 9, and a control unit 10. The LD unit 9 includes a light source 1, a coupling lens 2, correction lenses 3, 4, and moving mechanisms 11, 12. The correction lens 3 is an element that has power only in the main scanning direction and adjusts a focal position in the main scanning direction. The correction lens 4 is an element that has power only in the sub-scanning direction and adjusts the focal position in the sub-scanning direction. Moving mechanism 11, 12
Moves the correction lenses 3 and 4 in the optical axis direction.

The detecting section 8 detects the image forming state of the light beam formed by the image forming element 6, and the control section 10 controls each of the correction lenses 3 and 4 based on the signal from the detecting section 8. Calculate the amount of movement in the axial direction. The control unit 10 omits details of each unit in FIG. 1, but the amplification circuit unit 3 amplifies signals from the detection element unit 30, the counter 31, and the detection unit 8.
2. A differentiation circuit 33, an A / D (analog / digital) conversion unit 34 for converting an analog signal into a digital signal, a CPU (central processing unit) 40 for performing arithmetic processing, and a driver unit 41 for driving a correction lens. (See FIG. 2). Thus, the detection unit 8 and the control unit 10
Are formed adjacent to each other or on the same circuit board, the occurrence of electrical noise can be suppressed.

In the optical scanning device according to the second embodiment, FIG.
As shown in the figure, a detection element section 30, a counter 31, an amplification circuit section 32, a differentiation circuit 33, and an A / D conversion section 34 are provided in the beam detection unit 28, and the CPU 40 and the driver section 41 are mounted on the main body base. The configuration is provided. As described above, the control unit 10 includes the detection element unit 30 as the detection unit 8, the counter 31, the amplification circuit unit 32, the differentiation circuit 33, the A / D conversion unit 34, and the CPU as the control unit 10.
The components of the driver 40 and the driver 41 are not limited to those integrated as shown in FIG. 1, but only the amplifier circuit 32 and the differentiating circuit 33, which are likely to generate noise, are provided on the main body base separately. You may. Further, it is also possible to incorporate the function of the CPU 40 for performing the arithmetic processing so as to be performed by the CPU of the machine main body.

FIG. 3 is a block diagram showing the configuration of the optical scanning device shown in FIG. The portions indicated by broken lines in FIG. 3 are the sensing element unit 30, the counter 31, the amplification circuit unit 32, and the differentiation circuit 3.
3 is a block diagram illustrating a configuration of an optical scanning device according to a second embodiment in which the A / D converter 3 and the A / D converter 34 are integrated.
In FIG. 3, the CPU 40 and the driver unit 41 are provided on the main body base as in FIG. As shown in FIG. 3, the counter 31 outputs the scanning pitch signal to the differentiating circuit 33 and A
The / D converter 34 detects a beam detection signal. As shown in FIG. 1 or FIG. 2, a detection unit 8 and a control unit 10 for calculating the amount of movement of the correction lenses 3 and 4 in the optical axis direction based on a signal from the detection unit 8 are adjacent to each other, or a circuit board. By forming them integrally on top, generation of electrical noise can be suppressed.

Next, a method of detecting a light beam in the detection unit and the control unit will be described. FIG. 4 is a diagram illustrating detection of a light beam. When the light beam B0 passes over the slit (detection element) 15 and scans by tilting the opening on the slit formed on the PD (optical disk), an output waveform as shown in FIG. 4A is observed. . FIG.
(A) to (c) show the result that the focal point of the light beam B0 on the photoconductor 7 is gradually narrowed. Here, it is assumed that a time interval when a certain threshold is cut is t1, and a peak light amount is P1. FIG. 4 shows the detection in the case where the number of light beams from the light source 1 is one (single). FIG. 5 is a graph showing the amount of movement of the correction lens. The time interval t1 or the peak light amount P1 as shown in FIG. 4 is monitored, and based on the monitoring result, t or 1 / P with respect to the movement amount of the correction lens as shown in FIG.
It is possible to detect the imaging state of the light beam by graphing.

Next, a method of detecting the scanning pitch of the light beam in the detection unit and the control unit when the light source is an LD array that emits a plurality of light beams or a multi-beam obtained by combining a plurality of LDs will be described. FIG. 6 is a diagram illustrating scanning pitch detection when there are a plurality of light beams. FIG.
(A) shows scanning pitch detection by the vertical slit 20 and the inclined slit 21. FIG.
(B) shows scanning pitch detection by the triangular slit 22. The time when the light beam B1 passes through the slits 20 and 21 is T1, and the light beam B2 is
The time of passing through 1 is T2, the scanning speed of the light beam is v, and the inclination angle of the slit 21 is θ. The scanning pitch of the light beam at this time is (T1 × v−T2 × v) × tan
θ. In addition to the above description, the scanning pitch detection may be implemented by a line CCD or the like.

The slit 2 shown in FIG.
By integrally forming a detection unit 8 for detecting a scanning pitch of a light beam using 0, 21 or 22 and a control unit 10 for calculating a scanning pitch correction amount based on a signal from the detection unit, Generation of electrical noise can be suppressed. Also, the light beam imaging state detector 8 detects the light beam imaging state in the main scanning direction with a slit 20 as shown in FIG. 6, and the slit 21 detects the light beam imaging state in the sub-scanning direction. Thus, the scanning pitch can be detected. In the case of an LD array, a mechanism for rotating the LD array around the optical axis is provided, or the LD unit 9 is moved in the optical axis direction (see FIG. 2).
This is possible. In the case of a multi-beam obtained by combining a plurality of LDs, adjustment can be performed by moving the entire LD unit in the optical axis direction.

[0017]

According to the first aspect of the present invention, the focus position detecting means for detecting the focus position of the light beam scanned by the scanning means on the surface to be scanned, and the focus position detecting means detect the focus position. The signal relating to the focal position is subjected to arithmetic processing, and the adjusting means for adjusting the focal position of the light beam based on the result of the arithmetic operation is formed adjacently, so that the occurrence of electrical noise can be suppressed, and The adjustment accuracy for adjusting the focal position of the light beam on the surface can be improved.

According to the second aspect of the present invention, since the light source emits a plurality of light beams, the light source can be constituted by an LD array emitting a plurality of light beams or a multi-beam obtained by combining a plurality of LDs.

According to a third aspect of the present invention, there is provided a scanning pitch detecting means for detecting a scanning pitch of a plurality of light beams scanned by a scanning means on a surface to be scanned, and a scanning pitch detected by the scanning pitch detecting means. An adjusting means for processing the signal and adjusting the scanning pitch based on the result of the calculation is formed adjacently, so that it is possible to suppress the occurrence of electrical noise and to reduce the light beam on the surface to be scanned. Adjustment accuracy for adjusting the focal position can be improved.

According to the fourth aspect of the present invention, the focus position of the light beam scanned by the scanning means on the surface to be scanned and the light beam scanned by the scanning means on the surface to be scanned. A detecting means for detecting the pitch, and an adjusting means for performing arithmetic processing on a signal relating to the focal position and a signal relating to the scanning pitch detected by the detecting means, and adjusting the focal position and the scanning pitch of the light beam based on the computation result. Since they are formed adjacent to each other, the cost can be reduced, the generation of electrical noise can be suppressed, and the adjustment accuracy for adjusting the focal position of the light beam on the surface to be scanned can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of an optical scanning device according to a first embodiment.

FIG. 2 is a diagram illustrating an overall configuration of an optical scanning device according to a second embodiment.

FIG. 3 is a block diagram illustrating a configuration of the optical scanning device in FIG. 2;

FIG. 4 is a diagram showing detection of a light beam.

FIG. 5 is a graph showing a movement amount of a correction lens.

FIG. 6 is a diagram showing scanning pitch detection when there are a plurality of light beams.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Coupling lens 3, 4 Correction lens 5 Deflector 6 Imaging element 7 Scanned surface 8 Detection part 9 LD (semiconductor laser) unit 10 Control part 11, 12 Moving mechanism 30 Detection element part 31 Counter 32 Amplification circuit part 33 Differentiating circuit 34 A / D (analog / digital) conversion unit 40 CPU (central processing unit) 41 Driver unit

Claims (4)

[Claims] A light source that emits a light beam; a scanning unit that deflects the light beam emitted from the light source and condenses the light beam on a surface to be scanned; A focus position detecting means for detecting the focus position in the above-mentioned image forming state; and a signal relating to the focus position detected by the focus position detecting means is arithmetically processed, and the focal position of the light beam is adjusted based on the arithmetic result. An optical scanning device, comprising: an adjusting unit, wherein the focus position detecting unit and the adjusting unit are formed adjacent to each other. 2. The optical scanning device according to claim 1, wherein the light source emits a plurality of light beams. A light source that emits a plurality of light beams; a scanning unit that deflects the light beam emitted from the light source to converge on a surface to be scanned; and a plurality of light beams that are scanned by the scanning unit. Scanning pitch detecting means for detecting a scanning pitch on the surface to be scanned, an adjusting means for performing arithmetic processing on a signal relating to the scanning pitch detected by the scanning pitch detecting means, and adjusting the scanning pitch based on the calculation result; An optical scanning device, comprising: the scanning pitch detecting means and the adjusting means are formed adjacent to each other. 4. A light source that emits a plurality of light beams, a scanning unit that deflects the light beam emitted from the light source and condenses the light beam on a surface to be scanned, and a light beam that is scanned by the scanning unit. Detecting means for detecting a focal position of an image-formed state on a scanning surface and a scanning pitch of the light beam scanned by the scanning means on the surface to be scanned; and a signal relating to the focal position detected by the detecting means. Adjusting means for calculating a signal related to the scanning pitch and adjusting the focal position and the scanning pitch of the light beam based on the calculation result, wherein the detecting means and the adjusting means are formed adjacent to each other. An optical scanning device, comprising: