JPS61171273A - Photoscanner - Google Patents

Abstract

PURPOSE:To set the output luminous energy constant and to correct shading by giving to a semiconductor laser an injected current which is corrected previously so that the center of a scan position can be lower. CONSTITUTION:After light generated by the semiconductor laser 1 is collimated by a collimating lens 2, it is converged by a cylindrical lens 3 and scanned in one direction of a scan surface 6 corresponding to the hologram lens 5 of a rotating hologram scanner 4. Shading information on the scan line is previously calculated or analyzed experimentally, and stored in a memory 23 corresponding to the scan position. A position detector 21 jointed to the scanner 4 detects the position with respect to the rotation of the scanner 4. Shading information on the corresponding lens 5 is accessed to an arithmetic circuit 22 from the memory 23. A voltage set in the memory 23 is supplied to an electric power source 11, and the injected current to a laser source 1 positioned at the center of the scan position is so controlled to be dropped, thereby correcting the shading.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical scanning device that makes the intensity of a reflected light signal from a scanning object constant.

(Prior Art) Laser beam scanning devices used in laser printers and laser facsimiles are generally those that combine a rotating polygon mirror and an f-theta lens, or those that use a holographic or liner lens. In these devices, the light intensity decreases at the scanning end due to the directivity of the scanning surface, etc., resulting in light intensity angle dependence called shading as shown in the characteristic diagram of FIG.

When this shading occurs, the signal-to-noise ratio decreases,
If the amount of shading is large, it must be corrected. In particular, in holography and scanners, the amount of shading increases due to the angular dependence of diffraction efficiency. Traditionally, to correct shading,
Many methods have been used to correct the received light signal, but these methods have the drawback of decreasing the signal-to-noise ratio at the scanning end.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve these drawbacks, and by adjusting the current injected into the semiconductor laser, the oscillation light intensity can be changed and shading can be corrected. An object of the present invention is to provide an optical scanning device.

(Means for Solving the Problems) An optical scanning device according to a first aspect of the present invention includes a semiconductor laser, a laser power source that supplies an injection current for driving the semiconductor laser, and scans output light from the semiconductor laser. a hologram scanner; a memory means for measuring and storing shading information corresponding to the scanning position of the hologram scanner; a position detecting means for detecting the scanning position of the hologram scanner; and control means for controlling the injection current of the laser power source so as to correct the shape ink information of the memory means read out correspondingly.

An optical scanning device according to a second aspect of the present invention includes a semiconductor laser, a laser power source that supplies an injection current to drive the semiconductor laser, a hologram scanner that scans the output light from the semiconductor laser, and a hologram scanner that scans the output light from the hologram scanner. A light branching means for branching part of the output light, a light detection means for detecting the intensity of the output light from the light branching means, and a current injected into the laser power source so that the level of light detected by the light detection means is constant. and a control means for controlling.

(Principle of the invention) Combining a rotating polygon mirror and fJvyx, the amount of light
In holography and laser beam scanning devices, such as J-scanning devices and hologram scanners, the amount of light at the scanning end decreases due to (1) the directivity of reflected light on the paper surface, and (2) a decrease in the viewing angle of the lens.

The rate of decrease in lens viewing angle is as follows. The distance α between the rotating polygon mirror or hologram disk and the scanning surface, and the scanning length! , the lens radius is r.

If the or-axis angle is θ, at the center of scanning, f-
1) The solid angle ω0 that the lens or hologram lens extends with respect to the scanning position is K as follows.

Further, the solid angle ω at the scanning end is expressed by the following equation.

Therefore, from each of these equations, the light amount ratio ω between the scanning edge and the scanning center is
/ω0 is expressed as follows.

......(3) For example, CL = 150 m m l = 100
rnxr *θ=10′ ding fK, and when the first factor is taken into account, the total 7-ating amount reaches 20− or more.

Furthermore, in holographic laser scanners,
Since the angular dependence of the hologram's diffraction wheel is added to these 7 edging amounts, the total shading amount is 30
%. In this case, shading correction becomes an even more important factor.

As shown in the characteristic diagram in Figure 3, this shading exhibits a characteristic in which the amount of light decreases around the scanning position, so as shown in the characteristic diagram in Figure 4, the amount of light injected into the laser light source at the center of the scanning position is If the current is controlled to be lower, the amount of output light can be constant regardless of the scanning position.

The method for correcting this shading is to store previously measured shading information in memory,
A method of controlling the injection current so that this shading is corrected, and a method of detecting the amount of output light and injecting it so that the intensity of the output light is constant (Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention.

In the figure, 1 is a semiconductor laser serving as a light source, 2 is a collimating lens, 3 is a cylindrical lens, 4 is a hologram scanner, 5 is a hologram lens, 6 is a scanning surface, 11 is a power source for the semiconductor laser 1, 21 is a position detector, 22 is an arithmetic circuit, 2
3 is memory. In this embodiment, correction information for the current injected into the semiconductor laser as shown in FIG. 4 for the shading shown in FIG. This is to read the data in and control the voltage of the power supply 11. The light emitted from the semiconductor laser 1 is collimated by the collimating lens 2, then converged by the cylindrical lens 3, and scans in one direction on the scanning surface 6 of the rotating hologram scanner 4 in correspondence with the hologram lens 5 of the scanner 4. do.

The shading information of this scanning break is calculated or experimentally analyzed in advance and stored in the memory 23 in correspondence with the scanning position. The position detection with respect to the rotation of the hologram scanner 4 is performed, for example, by using the hologram scanner 4.
This is done by a position detector 21, such as an encoder, coupled to a position detector 21, such as an encoder. The shading information of the corresponding hologram lens 5 is accessed from the memory 23 to an arithmetic circuit 22 such as a microcomputer, and the oscillation output of the semiconductor laser 1 is controlled by supplying the voltage determined in the memory 23 to the power supply 11. . At this time, since there is no need to correct the light reception signal, a complicated circuit as in the prior art is not required.

FIG. 2 is a block diagram of a second embodiment of the present invention.

In the figure, the same numbers as in Figure 1 indicate the same-configuration pseudotrees,
7 is a beam splitter, 8 is a cylindrical lens, 9 is a one-dimensional array photodetector, IO is a control device, and 11 is a power source. The light emitted from the semiconductor laser 1 is collimated by the collimator lens 2, then converged by the J cylindrical lens 3, and scanned on the scanning surface 6 by the hologram lens 5 of the hologram scanner 4. In this case, the scanning surface 6 is scanned in one direction corresponding to the rotation of the hologram scanner 40. A beam splitter 7 is placed between the hologram lens 5 and the scanning surface 60, a part of the scanning beam is extracted, and the extracted beam is focused by the cylindrical lens 8 to provide light for measuring the light intensity in the scanning direction. Input to detector 9. The voltage of the power source 11 is controlled by a control device 10 including an arithmetic circuit such as a microcomputer, so that the intensity signal from the photodetector 9 is always constant. Therefore, since the received light signal level is always constant, this method has the advantage that the signal-to-noise ratio is always constant compared to the conventional method.

(Effects of the Invention) As explained above, according to the present invention, by applying an injection current to the semiconductor laser that has been corrected in advance to lower the center of the scanning position, changes in the light amount can be reduced as shown in FIG. Since the light output is increased at the scan end where shading is large and the light output is reduced at the scan center where the amount of light is large, the output light amount is corrected to one foot as shown in FIG. It is also possible to detect the output of the output light and control the power supply of the semiconductor laser so that the intensity of the output light is constant. Therefore, by using the optical scanning device of the present invention, the intensity of the reflected light signal from the scanning object can be made constant.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a first embodiment of this invention, Fig. 2 is a block diagram of a second embodiment of this invention, Fig. 3 is a characteristic diagram of an example of general shading, and Fig. 4 is a diagram of a company's FIG. 7 is a characteristic diagram of an example of an injection current for shading correction. In the figure, 1°-°°-semiconductor laser, 2... collimating lens, 3... cylindrical lens, 4 old ° hologram scanner, 5... hologram lens, 6.
・−・Scanning plane, 7・Beam splitter, 8・
... Cylindrical lens, 9゛°°/°° one-dimensional array photodetector, 10... Control device, 11... Power supply, 21...Position detector, 22...
Arithmetic circuit, 23...- Memo change, Sai, Loghumski Y de, etc. 2I! lI Kaya 4F! ! J

Claims (2)

[Claims] (1) Measure in advance a semiconductor laser, a laser power source that supplies injection current to drive the semiconductor laser, a hologram scanner that scans the output light from the semiconductor laser, and shading information corresponding to the scanning position of the hologram scanner. a position detecting means for detecting the scanning position of the hologram scanner; and a position detecting means for detecting the scanning position of the hologram scanner; An optical scanning device comprising: control means for controlling injection current of a laser power source. (2) A semiconductor laser, a laser power supply that supplies an injection current to drive the semiconductor laser, a hologram scanner that scans the output light from the semiconductor laser, and a light that partially branches the output light from the hologram scanner. A branching means, a light detection means for detecting the intensity of the output light from the light branching means, and a control means for controlling the injection current of the laser power source so that the level of light detected by the light detection means is constant. Optical scanning device.