JPS6021032A - Angle amplifier of laser beam - Google Patents

Abstract

PURPOSE:To expand the separation angle of laser beams by arranging two reflectors so that the incident and separation angles of two laser beams made incident with a fixed separation angle is expanded and projected. CONSTITUTION:Out of two laser beams B1, B2 separated and projected from an ultrasonic wave polarizer 17, one beam B1 goes straight on the optical axis without polarization and the other beam B2 is polarized and projected with a certain separation angle theta1 from the beam B1. In an angle amplifier 30, the beam B1 goes straight on the optical axis and the beam B2 is reflected and refracted by the reflectors 31, 32 to obtain a projection angle theta4 larger than the incident angle theta1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser beam angle amplifier used for expanding the separation angle of two laser beams.

Figures 1 and 2 show a laser beam angle amplifier 3 of the present invention.
This shows an example of an optical system using zero. This optical system enables color printing in a beam scanning device that scans the photoreceptor of a laser printer while turning the laser beam on and off. First, we will explain the overall image of this optical system, and then The necessity of the laser beam angle amplifier of the present invention will be explained. The laser beam exiting the H,eNe laser light source 11 enters the ultrasonic optical modulator 13 via a condensing lens 12 . FIG. 3 is a diagram showing the principle of the ultrasonic optical modulator 13. When an ultrasonic wave 15 is applied to the crystal 14 of the optical modulating element from a specific direction, the laser beam is directed at an angle (2θ) twice the incident direction θ. Bragg diffraction. This diffraction angle 2θ is determined by the ultrasound speed V, the ultrasound frequency f, and the wavelength of the laser beam (2θ=input f/V).
Therefore, when the ultrasonic waves are turned on and off, the laser beam emitted from the ultrasonic optical modulator 13 is turned on and off. The condenser lens 12 is used to reduce the laser beam diameter d to a diameter that realizes a desired response time (γd/v).

The laser beam exiting the ultrasonic optical modulator 13 passes through a collimator lens 16 to become a parallel beam again, and then passes through an ultrasonic optical deflector 17 and a laser beam angle amplifier 30, which is a feature of the present invention. expander 18
Its diameter is expanded by The beam expander 18 consists of two lenses 18a and 18b, and in principle is equivalent to using a telescope in reverse. The laser beam exiting the beam expander 18 is reflected by the reflecting surface 20 of the rotating polygon mirror 19, and then reflected by the fO lens 21.
According to the on/off generated by the ultrasonic light modulator 13, a row of on/off spots, that is, a scanning line 23 is drawn on the photosensitive drum 22. This scanning line 23 is, for example, , which causes the distribution of charging and non-charging of the photoreceptor constituting the photoreceptor drum 22.
One scanning line 23 is generated in the axial direction of the photosensitive drum 22 for each reflecting surface 20 of the rotating polygon mirror 19. As a result of the continuous rotation of the polygon mirror 19 and the rotation of the photoreceptor drum 22, a latent image pattern of continuous scanning lines 23 is formed on the photoreceptor drum 22.

For example, a charged developer is then supplied to the photoreceptor drum 22, and printing is performed according to a conventional printing method utilizing charging and uncharging of the photoreceptor. Unlike a normal photographic lens or a Fourier transform lens, the fθ lens 21 has a focal length f,
There is a characteristic that the image height y is y=fθ with respect to the incident angle θ, and therefore the laser beam reflected by the polygon mirror 19 can be linearly reproduced on the photoreceptor drum 22. Widely used in optical systems for printing.

Note that the reference numeral 24 in FIG. 1 indicates a mirror for bending the optical path of the laser beam.

The ultrasonic light deflector 17 is installed in the optical system of the laser beam printer based on the above principle to enable 5f color printing. The optical deflector 17 has the same structure as the ultrasonic optical modulator 13 in principle, but the response speed for diffracting the laser beam is much slower than that of the ultrasonic optical modulator 13. Therefore, it differs from the ultrasonic optical modulator 13 in that the diffraction angle is large. Specifically, such properties are obtained by changing the crystal axis direction of the elements constituting the polarizer. Another difference between the ultrasonic light deflector 17 and the ultrasonic light modulator 13 is that the laser beam diffracted from the plug is also irradiated onto the photoreceptor drum 22 . In the ultrasonic light modulator 13, the plug-diffracted laser beam is removed from the optical path and does not reach the photosensitive drum 22. The plug diffraction in the ultrasonic light deflector 17 is timed so that it occurs every time one scanning line 23 is drawn on the photosensitive drum 22. This timing is
The number of rotations of the polygon fi 19, the number of reflective surfaces 20, etc.
A beam sensor may be provided on the incident side in the axial direction, and the ultrasonic waves applied to the ultrasonic light deflector 17 may be controlled so that diffraction occurs when the beam is incident on this sensor.

When the laser beam is deflected at a predetermined period by the ultrasonic optical deflector 17 in this way, a second
As shown in the figure, two tree scan lines 2 are separated by a distance sentence.
3 is drawn. Therefore, for example, if one of these two beams is used for red and the other for blue, and this two-beam scanning device is also provided as a color base to draw scanning lines 23 for black and white, color printing can be achieved by combining the two. can.

On the other hand, the reason why the diameter of the laser beam is expanded by the beam expander 18 is to make the diameter of the beam that reaches the photoreceptor drum 22 an appropriate size according to the photoreceptor drum 22. That is, if the diameter of the laser spot on the photosensitive drum 22 is d, the diameter of the incident beam on the f0 lens 21 is D, the focal length is f, and the wavelength of the laser beam is input, then there is a relationship of D = 1.27 f/d. It's true. Now on = 0. [1328gm,
f = 500 mrn, d = 0. Irmm φt
61:, D'#4mm, and if the laser beam diameter is normally around 0.81, it is necessary to expand the beam diameter approximately five times with the beam expander 18.

However, when the beam diameter is increased, the separation angle of the laser beam separated by the ultrasonic optical deflector 17 tends to become smaller. That is, in FIG. 4, two beams B1. The separation angle of B2.

Cow, 2 beams Bl emitted from beam expander 18
, B2's separation angle is 02, beam expander 1
There is a relationship of θ4γ(1/m)·o2, where m is the magnification of 8.

Furthermore, if the distance on the photoreceptor drum 22 of the two laser beams separated by 1 by the ultrasonic optical deflector 17 is defined as ΔI, then the separation angle of the beams incident on the fθ lens 21 is 2*:. θ2 must be as follows, where f is the focal length of the fθ lens 21. θ2==Δ/f. In other words, in order to increase the amount of separation, do you need an fθ lens? (2) The angle of separation of the two laser beams incident on the beam must be increased. If we try to enlarge the beam diameter in this way, the separation angle will be reduced. Therefore, even if the beam diameter is enlarged and the separation angle is reduced, the beam separation angle θ2 can still be obtained.
1 must be increased. Specifically, θ2 needs to be several degrees, whereas θ1 can only be a few degrees at most in the ultrasonic light deflector 17.

The present invention solves these problems of laser beam printers that directly enable color printing, and the separation angle of two laser beams separated by an ultrasonic optical deflector is transferred to the beam expander 18. This was done for the purpose of enlarging (increasing) the beam separation angle before the beam is incident.

In order to achieve this purpose, the laser beam angle amplifier according to the present invention is provided with a passing optical path through which one of the two laser beams incident with a certain separation angle passes through as is, and also with the upper and lower sides of this passing optical path. are provided with first and second reflecting mirrors that respectively reflect and refract the other laser beam in turn, and use the first and second anti-Q4 mirrors to enlarge the incident separation angle of the two laser beams and emit the laser beams. It is characterized by being arranged in such a way that it

The present invention will now be described with reference to the illustrated embodiments. As shown in FIG. 5, the two laser beams Bl and B2 that are separated and emitted from the ultrasonic optical deflector 17 are arranged so that the negative beam B1 is not deflected by the optical deflector 17 and the optical axis is The other beam B2 is a beam that is deflected by the optical deflector 17 and exits at a certain separation angle θ1 with respect to the optical axis, that is, beam 1\Bl. The angle amplifier 30 of the present invention allows this one beam Bl to proceed straight on the optical axis as it is, and reflects the other beam B2 by first and second reflecting mirrors 31 and 32 located above and below the beam B1 in the figure. It refracts the beam to obtain an output angle θ4 larger than the incident angle θ1, and the beam Bl is refracted between the first and second reflecting mirrors 31 and 32.
A passage space 33 is formed to allow the passage of.

The first reflecting mirror 31 has its reflecting surface tilted slightly downward in the figure (inclination angle α) from a plane perpendicular to the beam Bl toward the ultrasonic optical deflector 17 side, and is fixed to the base 34. ing. On the other hand, the second reflecting mirror 32 has its reflecting surface as the beam Bl.
It is tilted slightly upward in the figure (angle of inclination β) toward the beam expander 18 from a plane perpendicular to the plane, and is fixed to a tilting plate 36 that can swing around a fulcrum shaft 35 of a base 34. . As shown in FIG. 6, the tilting plate 36 is provided with a vertically long adjustment hole 37 at a position away from the fulcrum shaft 35. The eccentric portion 38a of the pin 38 is fitted. Therefore, when the eccentric pin 38 is rotated, the tilting plate 36, that is, the reflecting mirror 32 swings about the fulcrum shaft 35 due to the action of the eccentric portion 38a, and the angle of the reflecting surface changes.

-1- The present angle amplifier having the configuration described above has the above-mentioned angle θ1.04,
The following relationship holds true for α and β.

β-α-(04-01)/2 - Force, 04=MO, (M is the separation distance Δ of the two beams on the bipedal drum, the focal length of the fO lens 1Iif, the magnification of the beam expander 18 In , and ultrasonic optical deflector 1
(a constant determined from the separation angle 01 of 7), β-α= (M-1)0. /2 Therefore, for example, if 01 and α are determined, β will be a circle.

Now, when the incident angle 01 is 2.7°, if the exit angle θ is required to be 15°, then if the above α is fixed at If (, 35”, the above β should be set to 22.5’. According to the above embodiment, since the tilting plate 36 is rotated by rotating the eccentric pin 38, the angle β of the reflecting surface of the reflecting mirror 32 changes, and therefore the output angle θ is adjusted. Therefore, the photosensitive drum 22
You can freely adjust the spacing between the two wooden beams at the top.

Of course, even if the angle of the first reflecting mirror 31 is adjustable, the output angle β
However, in this case, the reflector 32
There is a problem that the position of the beam incident on the beam becomes unstable. If the first reflecting mirror 31 is fixed and the angle of the second reflecting mirror 32 is adjustable as in this embodiment, the beam B2 is incident on the reflecting mirror 32 at a fixed position, so the output angle adjustment mechanism It has the advantage of being easier.

In the above embodiment, the beam angle amplifier of the present invention is applied to the optical system of a laser beam printer that enables color printing. Applicable to all.

As described above, according to the laser beam angle amplifier of the present invention, the separation angle of two laser beams can be increased. Therefore, by using it together with an ultrasonic optical deflector that can separate laser beams only at a small angle, it is possible to obtain the laser beam separation angle necessary for colorizing laser printers.

[Brief explanation of drawings]

Fig. 1 is a plan view of a two-beam scanning device showing an example of an optical system using the laser beam angle amplifier of the present invention, Fig. 2 is a perspective view of the same, and Fig. 3 shows the action of the ultrasonic optical modulator. A schematic diagram, FIG. 4 is an optical path diagram explaining the phenomenon of reducing the beam separation angle by a beam expander, FIG. 5 is a side view showing an embodiment of the laser beam angle amplifier of the present invention, and FIG. 6 is the main part of the same. A breakdown of the homeland. 11... HeNe laser light source, 12... Condensing lens, 13... Ultrasonic light modulator, 16... Collimating lens, 17... Ultrasonic light deflector, 18... Beam expander , 19... Rotating polygon mirror, 20... Reflecting surface, 21... fO lens, 22... Photosensitive tram, 23... Scanning line, 30... Laser beam angle amplifier, 31... ...First reflecting mirror, 32... Second reflecting mirror, 33... Passing space, 34... Base, 35...
・Fulcrum shaft, 36...Tilt plate, 37...Adjustment hole, 38
...Eccentric bottle. Patent Applicant Asahi Optical Co., Ltd. Agent Kunio Miura' - Senko 7 City - 1F 1'' (Spontaneous) II/) March 28, 1982 Special Order No. 128934 2, Name of the invention - Square Claw Amplifier 3 by Zabi J. Relationship with the person making the amendment Patent No. 51 Applicant Address 2-36-9 Maeno-cho, Itabashi-ku, Tokyo Name (0
52) Asahi Optical Co., Ltd. Representative Toru Matsuki 4, Agent 102 6 Contents of amendment (1) [Outgoing laser beam] on page 3, line 4 of the specification
The description ``is corrected to ``If the outgoing laser beat is switched between the 0th order direction and the 1st order direction, and masked to cut off the 0th order light, the laser beam''. (2) Ibid. Correct "2 sheets" in the 13th line of the page to "2 sets". (3) "Polarizer" in lines 9 and 10 of page 5 of the same book is corrected to "deflector." (4) In lines 15 and 16 of the same page of the same book, the statement ``plug diffracted...removed'' was replaced with ``one of the 0th-order light and 1st-order light separated by plug diffraction, for example, the 0th-order light is masked. "Because it has been done," he added. (5) Change “04” to “02” on page 7, line 17 of the same book, “
θ2'' to ``θ4'', respectively. (6) In the 13th line of page 8 of the same book, the statement ``The number of degrees is necessary, and in contrast,'' has been changed to ``It is necessary to have a degree of success, and when this is multiplied by the magnification m of the heem expander 18, 04 However, it requires a certain degree of skill,'' he added. that's all

Claims (1)

[Claims] (1) A passing optical path through which one of the two laser beams incident with a certain separation angle passes through as it is, and a passing optical path located above and below this passing optical path and transmitting the other laser beam. 11" includes a first and second reflecting mirror that reflects and refract the two laser beams, and the first and second reflecting mirrors are arranged so as to enlarge the incident separation angle of the two laser beams and emit them (2. In claim 1, the first reflecting mirror is fixed, and the second reflecting mirror adjusts the direction of its reflecting surface.
An angular amplifier of the laser beam with ff function. (3) In claim 2, the second reflecting mirror is fixed to a tilting plate that is rotatable around a fulcrum shaft, and the second reflecting mirror is fixed to the fixed part through an adjustment hole drilled in the tilting plate. The angle amplifier of the laser beam is fitted with an eccentric part of an eccentric pin that can be supported.