JPH04220535A - Monitor device for laser output - Google Patents

Abstract

PURPOSE:To prevent polarization dependence of reflectance of a beam splitter in monitoring laser light to improve linearity in monitored values. CONSTITUTION:Linear polarization light 17 emitted from a laser oscillator 11 is converted into circular polarization light 18 by a first 1/4 wavelength plate 13 attached on the rear of a polarizer 12. Then the laser light is incident to a beam splitter 15 having particular polarization characteristics, and a part of it is reflected to a light receiving sensor 16 as monitoring light. Thus in whichever angle the polarizer 12 has rotated, the laser light is converted into the circular polarization light 18, so that reflectance of the beam splitter 15 is constant.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a laser output monitoring device, and in particular, a linearly polarized laser beam is attenuated using a rotating polarizer, and a portion of the laser beam is detected by a subsequent beam splitter. The present invention relates to a laser output monitoring device.

0002

[Prior Art] A conventional laser output monitoring device is shown in Fig. 6.
, as shown in FIG. 7, a laser oscillator 2 that emits a linearly polarized laser beam in one direction of the optical axis, a rotary polarizer 3 that can continuously attenuate the laser beam using polarization, and an attenuator. a beam splitter 5 that takes out (reflects) a part of the laser light as monitor light 4;
and a light receiving sensor 6 that detects the amount of light. Note that in FIG. 7, arrow A indicates the rotation direction of the polarizer 3, and the monitor light 4, beam splitter 5, and light receiving sensor 6 are omitted in FIG.

Next, the operation will be explained. The laser beam emitted from the laser oscillator 2 onto the optical axis 1 passes only the P-polarized component by the polarizer 3 (attenuation effect). A portion of the laser light that has passed through the polarizer 3 is reflected by the beam splitter 5 as monitor light 4 and enters the light receiving sensor 6 . On the other hand, the laser light transmitted through the beam splitter 5 is used for the original purpose of the laser light (for example, processing, etc.).

In the above operation, as shown in FIG.
The laser beam from the laser oscillator 2 is linearly polarized light 7 in the Y direction.
In this case, the laser light that passes when the rotation angle of the polarizer 3 is α° is attenuated, and becomes linearly polarized light tilted by α° from the Y direction. Then, as shown in FIG. 9, at a position where the polarizer 3 is rotated by 2α degrees, the passing light is further attenuated and becomes linearly polarized light 8 tilted by 2α degrees from the Y direction.

[0005] The beam splitter 5 also has P in the Y direction.
It has a polarized component and has the property of reflecting a part of the S-polarized component (X direction) of the incident light to the light receiving sensor 6 side as monitor light 4. Now, as shown in Figure 10, the rotation angle of polarizer 3 is α
Let Eαt be the combined vector of the light passing through the polarizer 3 (light incident on the beam splitter 5) when the rotation angle of the polarizer 3 is 2α°, and E2αt be the combined vector of the light passing through the polarizer 3 when the rotation angle of the polarizer 3 is 2α°. Then, the laser light reflected as the monitor light 4 has Eαt as E
The αs component, E2 αt becomes part of the E2αs component, and the actual laser output value becomes Eαs <E2 αs, whereas Eαt >E2αt. Therefore, the reflectance of the beam splitter 5 varies depending on the rotation angle of the polarizer 3 as shown in FIG. 4, and the values monitored by the light receiving sensor 6 lack linearity.

[0006]

[Problems to be Solved by the Invention] As described above, in this conventional laser output monitoring device, the polarization direction of linearly polarized light changes depending on the rotation angle of the polarizer 3; 5 is fixed. For this reason, the reflectance changes depending on the polarization direction of the laser beam incident on the beam splitter 5, as shown in FIG. Therefore, there is a problem that the laser light reflected as the monitor light 4 has no linearity, and the power of the laser light attenuated by the polarizer 3 cannot be accurately measured.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above-mentioned problems, and is to provide a laser output monitoring device that can accurately monitor laser output.

[0008]

[Means for Solving the Problems] The invention as claimed in claim 1 includes a rotating polarizer that continuously attenuates linearly polarized laser light using polarization characteristics, and a beam splitter that is disposed after the polarizer. A laser output monitoring device comprising: reflecting a part of the laser beam using the beam splitter and detecting the output using an optical sensor;
The feature is that a quarter-wave plate that rotates in synchronization with the polarizer is inserted between the polarizer and the beam splitter.

The invention according to claim 2 is characterized in that, in addition to the above configuration, a quarter wavelength plate is disposed on the downstream side of the beam splitter.

0010

[Operation] According to the present invention, there is provided a beam splitter between the polarizer and the beam splitter, which rotates in synchronization with the polarizer.
By inserting the /4 wavelength plate, it becomes possible to always convert the linearly polarized laser light that has passed through the polarizer into circularly polarized light and make it incident on the beam splitter. As a result, the reflectance of the beam splitter is kept constant and the laser output can be accurately monitored.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic side view showing an embodiment of a laser output monitoring device according to the present invention, FIG. 2 is a schematic front view of the laser output monitoring device, and FIG. 3 is an operation of the laser output monitoring device. It is an explanatory diagram. This laser output monitoring device includes a laser oscillator 11 that emits linearly polarized laser light in the direction of the optical axis 10, and can continuously attenuate the laser light using polarized light, as shown by arrow A in FIG. a polarizer 12 that rotates in a direction; a first quarter-wave plate 13 that is disposed at the rear of the polarizer 12 and that is attached and aligned with its axis so that linearly polarized light that has passed through the polarizer 12 can be converted into circularly polarized light; , a beam splitter 15 that reflects a portion of the attenuated laser light as monitor light 14, and a light receiving sensor 16 that detects the amount of monitor light 14. Note that in FIG. 2, the monitor light 14, beam splitter 15, and light receiving sensor 16 are omitted.

In the above configuration, when the linearly polarized light 17 is emitted from the laser oscillator 11 in the direction of the optical axis 10, as shown in FIG.
3, the laser beam is converted from linearly polarized light 17 to circularly polarized light 18 and enters beam splitter 15.

Further, the circularly polarized light 18 is partially reflected by the beam splitter 15 and is incident on the light receiving sensor 16 as monitor light 14 . The circularly polarized light 18 that has passed through the beam splitter 15 is used for the original purpose of laser light, but in this case it is circularly polarized light. Therefore, when the linearly polarized light 17 is required, as shown in FIG. is converted into linearly polarized light 17. Note that if circularly polarized light 18 can also be used, this second quarter-wave plate 19 is unnecessary.

As described above, in this embodiment, no matter what polarization angle the laser beam has after passing through the polarizer 12 from 0° to 90°, the first polarizer installed on the subsequent stage side The /4 wavelength plate 13 converts the light into circularly polarized light. Therefore, as shown in FIG. 5, the reflectance of the beam splitter 15 is constant and the monitor light 14 has linearity, so there is an advantage that accurate laser output measurement can be performed.

[0016]

[Effects of the Invention] As explained above, according to the laser output monitoring device according to the present invention, a quarter wavelength plate that rotates in synchronization with the polarizer is installed between the polarizer and the beam splitter, and a quarter-wave plate that rotates in synchronization with the polarizer is installed between the polarizer and the beam splitter. Since the structure is configured so that linearly polarized light can be converted into circularly polarized light at any angle and incident on the beam splitter, the reflectance of the beam splitter can be maintained constant, allowing accurate monitoring of laser output. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an embodiment of a laser output monitoring device according to the present invention.

FIG. 2 is a schematic front view of the laser output monitoring device.

FIG. 3 is an explanatory diagram of the operation of the laser output monitoring device.

FIG. 4 is a diagram showing a change in reflectance of a beam splitter with respect to a polarization angle after passing through a polarizer in a conventional laser output monitoring device.

FIG. 5 is a diagram showing a change in reflectance of a beam splitter with respect to a polarization angle after passing through a polarizer in a laser output monitoring device of the present invention.

FIG. 6 is a schematic side view showing an example of a conventional laser output monitoring device.

FIG. 7 is a schematic front view of the laser output monitoring device.

FIG. 8 is an operation explanatory diagram showing the polarization direction of laser light when the polarizer rotation angle is 2° in a conventional laser output monitoring device.

9 is an operation explanatory diagram showing the polarization direction of laser light when the polarizer rotation angle is 2α° in FIG. 8; FIG.

FIG. 10 is a diagram showing the polarization direction of the laser beam after passing through the polarizer of FIGS. 8 and 9 as a vector.

[Explanation of symbols]

11 Laser oscillator 12 Polarizer 13 First 1/4 wavelength plate 14 Monitor light 15 Beam splitter 16 Light receiving sensor 17 Linearly polarized light 18 Circularly polarized light 19 Second 1/4 wavelength plate

Claims (2)

[Claims] [Claim 1] It comprises a rotating polarizer that continuously attenuates linearly polarized laser light using polarization characteristics, and a beam splitter placed after the polarizer. In a laser output monitoring device that reflects a portion of laser light and detects its output with an optical sensor, a quarter-wave plate that rotates in synchronization with the polarizer is inserted between the polarizer and the beam splitter. A laser output monitor device featuring: 2. The laser output monitoring device according to claim 1, further comprising a quarter wavelength plate disposed downstream of the beam splitter.