JPH02125764A - Quantity-of-light stabilizing light source device - Google Patents

Abstract

PURPOSE:To obtain a compact light source unit stable in the quantity of light by providing a quantity-of-light detection means for controlling the quantity of laser beam so as to make the quantity of light detected by the quantity-of- light detection means constant. CONSTITUTION:When the level of zero order beam is detected by a photosensor 13, said level is compared with a reference level in an AOM(acousto-optical modulation element) driver 15. When the level of zero order beam detected by the photosensor 13 is high, the AOM driver 15 increases ultrasonic output to raise diffraction efficiency and, contrarily, when the level of zero order beam is lower than the reference level, said driver 15 decreases ultrasonic output to lower diffraction efficiency and, by this method, laser beam of constant quantity is always outputted from an SHG(second higher harmonic generator) 8. The reference level can be adjusted by a level adjusting means 16.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optically stabilized light source unit used as a light source for laser printers and the like.

(Prior Art) A color laser printer using a silver halide photosensitive material as a recording medium requires three colors, red, green, and blue, as a light source. Conventionally, these laser light sources have been He-Ne (λ=
632.8nm), He-Ne (λ=547nm) for line use.
nm), A for blue (entering = 458 nm)
A gas laser was used. As is well known, these gas lasers, especially blue A-lasers, are large, consume a lot of power, and are expensive. Therefore, color laser printers using such gas lasers have become increasingly large and expensive, and therefore, although color laser printers can produce high-quality color images, they have not become widespread.

On the other hand, laser printers that use semiconductor lasers as light sources are also on the market, but these generally record binary images, and the amount of light is not sufficiently stabilized, so this type of laser uses analog modulation to It is not possible to obtain a toned image.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to provide a light source unit that is compact and has a stable light amount. A wavelength converter that converts the wavelength of laser light output from a semiconductor laser.

A light source unit is configured by a light amount detection means for detecting the amount of laser light whose wavelength has been converted by the wavelength conversion means, and a light amount control means for controlling the amount of laser light so that the amount of light detected by the light amount detection means is a constant amount. Configured.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 is a schematic diagram of a line light source unit as an embodiment of a light amount stabilizing light source unit according to the present invention.

In the figure, 1 surrounded by a chain line is a light source unit, 2 is a semiconductor laser that emits a laser beam with a wavelength of 830 nm, and 3 is a semiconductor laser that emits a laser beam with a wavelength of 830 nm.
The LD driver 4 that drives the semiconductor laser 2 is a photodiode that feeds back the output of the semiconductor laser 2 to the LD driver 3 to adjust the amount of light from the semiconductor laser 2.

The laser beam from the semiconductor laser 2 passes through the collimator lens group 5.
The light is made into parallel light beams by the laser beam, and is incident on a YAG rod 6 having a diameter of several millimeters, which is a laser medium. YAG lot 6 uses light with a wavelength of 830 nm as bon pink light to generate 110
Laser light output from the YAG lot 6, which performs laser oscillation with a wavelength of 60n, is focused by a focusing lens 7 and converted into an SHG (5 ecan
) larmonic Generation: Second harmonic generator) Injected into the waveguide 8a of the element 8.

Consisting of SHG Ninko 8 Lithium Obate, etc., 110
The wavelength is converted to a wavelength of 60 nm (ie, 530 nm) to generate green light. AOM is installed at the output end of SHG element 8.
(Acousto-optic modulation element) 9 is provided integrally. 9
a is an ultrasonic transducer that outputs ultrasonic waves into the crystal of AOM9. The AOM 9 may be provided separately from the SHG element 8, or may be provided integrally, which has the advantage of eliminating the need for optical axis adjustment.

Further, 10 is a cylindrical lens that shapes the beam emitted from the SHG element 8, and 11 is a filter that cuts the laser beam having a wavelength component of 11060n out of the light emitted from the SHG element 8 and passes only the light with a wavelength of 530nm. It is. This filter 11 is not necessarily necessary unless the recording medium or the foot sensor 13 (described later) is sensitive to light with a wavelength of 11060n, and is intended to prevent the 11060n laser light from leaking outside and causing harm to human eyes. It is preferable to provide 12 is a beam splitter that samples a part of the light modulated by the AOM 9 and guides it to the photosensor 13; 14 is a slit placed in front of the photosensor 13 to exclude light other than the θ-order light; and 15 is an AOM driver.

Reference numeral 16 denotes a level adjusting means (for example, a variable resistor) for adjusting the level of the amount of light.

Now, when the level of the zero-order light is detected by the photosensor 13, it is compared with a reference level in the AOM driver 15. The AOM driver 15 increases the ultrasonic output to increase the diffraction efficiency when the level of the 0th order light detected by the photosensor 13 is high, and conversely decreases the ultrasonic output when the level of the 0th order light is lower than the reference level. This lowers the diffraction efficiency, and thus the 5HG8 always outputs a constant amount of laser light.

Note that the reference level mentioned above can be adjusted by the level adjustment means 16. By operating the level adjusting means 16, for example, color balance can be adjusted.

The laser beam output from the light source unit l passes through the beam expander 17, 18 and is emitted to the fθ lens.
An image is formed on a recording medium 20 such as a silver halide photosensitive material. In the process, the laser beam is modulated by the AOM 21 placed between the beam expanders 17 and 18 according to the image signal.

FIG. 2 shows another embodiment of the present invention, in which a wavelength of 415
Blue light source unit 3 that outputs a nm blue laser beam
0 is a schematic configuration diagram of 0. In the figure, the same components as in FIG. 1 are designated by the same component numbers.

Since this unit outputs a blue laser beam, except for the YAG lot 6 in the line light source unit 1 shown in FIG. 415n
The aim is to obtain a blue laser beam of m. The configuration for stabilizing the amount of light is the same as that of the unit shown in FIG.

In the above embodiment, an AOM is used as the light amount control means, but the present invention is not limited to this, and for example, an EOM (electro-optic modulation element) may be used.

(Effects of the Invention) As explained above, according to the present invention, the light amount of the laser beam is controlled so that the light amount detected by the light amount detection means is a constant amount, so it is compact and the light amount is stable. It is possible to provide a light source unit with

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing one embodiment of a light amount stabilizing light source unit according to the present invention, and FIG. 2 is a schematic block diagram showing another embodiment of the present invention. ■... Green light source unit, 2... Semiconductor laser,
8...SHG element, 9...AOM, 12...beam splitter, 13...photo sensor, 15...A
OM driver, 16...level adjustment means, 30...
・Blue light source unit

Claims (4)

[Claims] (1) A semiconductor laser, a wavelength conversion means for converting the wavelength of the laser light output from the semiconductor laser, a light amount detection means for detecting the amount of the laser light wavelength-converted by the wavelength conversion means, and the light amount detection means A light amount stabilizing light source unit comprising: a light amount control means for controlling the amount of laser light so that the amount of light detected by the laser beam becomes a constant amount. (2) Claim 1 further comprising adjusting means for adjusting the certain amount.
The light amount stabilizing light source unit described in . (3) The light amount stabilized light source unit according to claim 1, wherein the light amount control means is an AOM or an EOM. (4) The light amount stabilized light source unit according to claim 3, wherein the AOM is provided integrally with the wavelength conversion means.