JPH06265817A - Laser pointer - Google Patents

Abstract

PURPOSE:To reduce the difference in the brightness of a projected straight line, etc., even when a moving speed is changed by providing a reflection mirror being displaced by a piezoelectric actuater and controlling the output of a semiconductor laser by the driving voltage of the piezoelectric actuater. CONSTITUTION:When voltage is impressed on a piezoelectric bimorph cell 14, a displacement is generated on a piezoelectric ceramic plate. As a result, the reflection mirror is rotated, a change in a reflecting angle of a laser beam is generated. A semiconductor laser 11 is driven by a laser driving circuit 16, however, the output of the laser 11 is controlled by a control circuit 17. The piezoelectric bimorph cell 14 is driven by a piezoelectric bimorph cell driving circuit 19 according to the signal of a sine wave or a rectangular wave, etc., having a prescribed frequency of an oscillator 18. A prescribed voltage level is set in a comparater 20, which performs a comparison with the output of the oscillator 18 and outputs a result to the control circuit 17. Thus, the output of the semiconductor laser is changed and the brightness of a laser pointer displaying a straight line, etc., is made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser pointer, and more particularly, to a laser pointer capable of projecting a straight line or the like by changing a reflection angle of laser light by using a piezoelectric actuator.

[0002]

2. Description of the Related Art Use of a laser pointer has been considered in order to focus laser light from a semiconductor laser by an optical system (lens) to form a light beam, which is projected on a projection surface to display a predetermined position. . On the projection surface such as a screen,
It is common to project a continuous light beam to display one spot.

It has been considered to display a line or a simple figure using this laser pointer. For that purpose, it is necessary to change the direction of the light beam to a predetermined direction and distance and repeat this for a short time. For the polarization of the light beam, a method of moving a reflection mirror can be considered, and it is possible to use electromagnetic or piezoelectric displacement.

It has been proposed to use a piezoelectric actuator, particularly a piezoelectric bimorph element, which is advantageous in terms of downsizing and low power consumption, as a means for obtaining the displacement of the reflection mirror for the above polarized light.

[0005]

When a reflecting mirror is moved by using the above piezoelectric actuator (piezoelectric bimorph), when a voltage such as a sine wave or a square wave is applied to drive the mirror,
The lines projected on the projection surface are bright at both ends and dark at the center, and the difference is fairly clear. This is because the moving speed of the light beam is low at both ends and the amount of the irradiated beam is large, whereas the amount of the beam irradiated at a high speed is small in the center.

FIG. 3 is a diagram for explaining the above phenomenon.
In (a), the vertical axis represents voltage and the horizontal axis represents time. (B)
Indicates the brightness of the projection surface at that time. For convenience of explanation, it is displayed in two stages of light and dark. In reality, the brightness changes gradually, with the brightest at both ends and the darkest at the center.

When a straight line is projected from the center to the left and right (up and down), point A (corresponding to the center) is the darkest and point C (corresponding to the end) is the brightest. This is because the point A has the fastest moving speed and the point C has the slowest moving speed.
The point B has an intermediate brightness.

When a piezoelectric bimorph is used, the amount of displacement at its free end is proportional to the applied voltage, but in the case of sinusoidal drive, the applied voltage does not increase or decrease temporarily, so the movement speed changes. This change in the moving speed directly affects the displacement of the reflection mirror, resulting in a difference in the moving speed of the light beam.

The present invention provides a laser pointer capable of reducing the difference in brightness of projected straight lines even if the moving speed changes.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above problems by controlling the output of a semiconductor laser according to changes in the moving speed.

That is, in a laser pointer for displaying a spot by converging a laser beam generated by a semiconductor laser by an optical system into a light beam and projecting the light beam on a projection surface, a reflecting mirror displaced by a piezoelectric actuator. It is characterized in that it comprises means for controlling the output of the semiconductor laser by the output of the detection means of the drive voltage of the piezoelectric actuator, and the output of the semiconductor laser is variable.

More specifically, the laser beam generated by a semiconductor laser is condensed by an optical system to form a light beam, and the light beam is projected by a laser pointer for projecting a spot on the projection surface. At least one of the reflecting mirrors that reflects is supported so as to change the angle at which the laser light is reflected by the bending of the piezoelectric actuator caused by the applied voltage, and compares the drive voltage of the piezoelectric actuator with a predetermined voltage that has been set. And a control circuit for controlling the current applied to the semiconductor laser according to the output of the comparator.

[0013]

As described above, the change of the irradiation amount caused by the moving speed of the light beam irradiated on the projection surface is adjusted by the amount of irradiation energy at each point, that is, the output of the semiconductor laser. Therefore, when the voltage applied to the piezoelectric actuator reaches a predetermined value, the switching element or the like is operated to control the current flowing through the semiconductor laser.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

Before describing an embodiment of the present invention, a reflective mirror driven by a piezoelectric bimorph will be described.
This will be described with reference to FIG. Laser light generated by the semiconductor laser 41 is condensed by an optical system (lens) not shown, and reflected by the reflection mirror 42 in a predetermined direction. The reflection mirror 42 is fixed to the support base 43,
A shaft is inserted through 43 and attached to a housing (not shown). The free end of the metal plate of the piezoelectric bimorph 44 in which electrodes are formed by attaching piezoelectric ceramic plates to both sides of the metal plate is fitted to one side of the support base 43, and the other end of the metal plate is fixed to the housing.

When a voltage is applied to the piezoelectric bimorph 44, the piezoelectric ceramic plate is displaced. This displacement is the displacement of the metal plate, and the free end moves up and down. As a result, the support base 43 rotates about the axis, and at the same time, the reflection mirror 42 also rotates. This rotation changes the angle at which the reflection mirror 42 reflects the laser light. The present invention is based on this reflection mirror 42.
It controls the rotation speed of.

FIG. 1 is a block diagram showing an embodiment of the present invention. Laser light is generated from the semiconductor laser 11 and the reflecting mirror 12 is moved by the piezoelectric bimorph 14, as in the above.

The semiconductor laser 11 is driven by a laser drive circuit 16 by a current supplied from a power source 15, and its output is controlled by a control circuit 17. Piezoelectric bimorph
The oscillator 18 drives the piezoelectric bimorph drive circuit 19 in response to a signal such as a sine wave or a square wave having a predetermined frequency. That is, a voltage as shown in FIG. 3 is applied, and the piezoelectric ceramic plate is displaced according to this voltage.

In the laser pointer according to the present invention, the oscillator
It comprises a comparator 20 which inputs 18 outputs. This comparator
A predetermined voltage level is set in 20, the output voltage of the oscillator 18 is compared, and the result is output to the control circuit 17. The control circuit 17 controls the current applied to the semiconductor laser 11 according to the output of the comparator 20. As a result, the output of the semiconductor laser changes.

At point A shown in FIG. 3, the beam is moved at a high speed and the emitted light becomes dark. Therefore, in this portion, the current is increased in order to increase the output of the semiconductor laser. On the contrary, at point C in FIG. 3, the moving speed of the beam becomes slower and the emitted light becomes brighter. Therefore, in this portion, the current is reduced in order to reduce the output of the semiconductor laser. For example, in FIG.
If the current is switched at the point corresponding to point B, the voltage corresponding to point B is set in the comparator 20 so that the current is switched in two steps.

FIG. 2 shows an example of a circuit for switching the current applied to the semiconductor laser by the control circuit. If resistors R1 and R2 are made equal, the switching element SW is turned on / off to change the current. Can be switched. A current that is twice as large as that when it is off flows when it is on. This switching element can realize a circuit having a sufficient switching speed by a switching circuit including a transistor.

In the above example, the current is switched in two stages, but it is also possible to set the voltage level more finely and switch in multiple stages. Further, the present invention can be applied to a device that moves the reflection mirror by another piezoelectric actuator, and can also be applied to a driving method in which the movement of the reflection mirror is not constant, such as an electromagnetic driving device.

[0023]

According to the present invention, it is possible to make the brightness of the laser pointer that displays a straight line or the like uniform. Moreover, it can be realized only by adding a comparator, and a compact and inexpensive laser point can be obtained.

Further, the stage of switching can be arbitrarily set by the circuit configuration.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram of an example of a switching circuit used in the present invention.

FIG. 3 is an explanatory diagram of a relationship between an applied voltage and a speed and brightness of a light beam.

FIG. 4 is a front view of a driving portion of a reflecting mirror that is moved by a piezoelectric bimorph.

[Explanation of symbols]

 11: Semiconductor laser 12: Reflecting mirror 14: Piezoelectric bimorph 17: Control circuit 18: Oscillator 20: Comparator

Claims (2)

[Claims] 1. A reflection mirror that is displaced by a piezoelectric actuator in a laser pointer that performs spot display by condensing laser light generated by a semiconductor laser with an optical system into a light beam and projecting the light beam onto a projection surface. A laser pointer, characterized by comprising means for controlling the output of the semiconductor laser according to the output of the detection means for detecting the drive voltage of the piezoelectric actuator, wherein the output of the semiconductor laser is variable. 2. A reflection mirror for reflecting a light beam in a laser pointer for spot display by converging a laser beam generated by a semiconductor laser by an optical system into a light beam and projecting the light beam on a projection surface. At least one of which is supported so as to change the angle at which the laser light is reflected by the bending of the piezoelectric actuator caused by the applied voltage, and comprises a comparator for comparing the drive voltage of the piezoelectric actuator with a set predetermined voltage, A laser pointer comprising a control circuit for controlling a current applied to a semiconductor laser by an output of the comparator.