JP2007309678A - Optical power measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical power measuring instrument that does not require alignment for measurements, when measuring optical power, and capable of enhancing measurement accuracy, using a simple constitution. <P>SOLUTION: This optical power measuring instrument for measuring the power of a light beam emitted from a light-emitting element 1 in a light-receiving element 2 side is provided with an annular half-mirror 3, provided in between the light-emitting element and the light-receiving element, a CCD camera 6 for detecting light reflected by the half-mirror, an image processor 7 for comparing an output from the CCD camera with a reference output for detecting the deviation of the optical axis and shift in the focus, and a driving unit 9 for regulating the positions of the half-mirror, the CCD camera and the light-receiving element, based on a detection result from the image processor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical power measuring apparatus, and more particularly to an apparatus for measuring the optical power of a light emitting element propagating in free space.

  When measuring the light power of a light emitting element propagating in free space on the light receiving element side, a light beam emitted from the bright spot of the light emitting element propagates in the air with a large spread. ) And the like, and the light receiving element surface and the light emitting element are placed close to each other for measurement.

  When laser light is used as a light emitting element, it is transmitted from a laser oscillator through a plurality of transmission mirrors and guided to an object, but part of the laser light is extracted from the optical path axis by a transmission mirror during transmission. It is received by the screen and converted into visible light. A cross section of the laser light appears as visible light on the screen and is captured as an image by the CCD camera, and then processed by an image processing technique by an arithmetic processing means to calculate a deviation from the target position and as a deviation correction signal. The oscillation device corrects the deviation on the optical axis by three-dimensionally oscillating the transmission mirror via the multi-axis controller. (For example, refer to Patent Document 1).

JP-A-8-103881 (paragraphs 0003 and 0004, FIG. 1)

  Since the conventional optical power measuring device is configured as described above, the positional accuracy between the light emitting element and the light receiving element surface is important. However, the light beam received on the light receiving element surface due to the influence of the positional deviation of the light emitting element. However, there is a case where the position of the light beam protrudes out of the surface of the light receiving element and the power of the light beam cannot be measured correctly. Therefore, it is necessary to perform measurement after aligning the light emitting element and the light receiving element.

  Furthermore, there is a problem that the structure becomes complicated because a plurality of lenses are used for detecting the positional deviation. In addition, as described above, there has been a method of extracting a part of light with a transmission mirror or the like in the prior art for correcting misalignment. However, the extracted light is lost when measuring the optical power, and the measurement is accurate. Could affect sex.

  The present invention has been made in order to address the above-described problems, and it is not necessary to perform measurement after alignment when measuring optical power, and can improve measurement accuracy with a simple configuration. It aims at providing a power measuring device.

  An optical power measurement device according to the present invention is an optical power measurement device that measures the power of a light beam emitted from a light emitting element on the light receiving element side, and is an annular half provided between the light emitting element and the light receiving element. A mirror, a CCD camera that detects light reflected by the half mirror, an image processing device that detects an optical axis shift and a focus shift by comparing the output of the CCD camera with a reference output, and the image processing And a driving device for adjusting the positions of the half mirror, the CCD camera, and the light receiving element based on the detection result of the device.

  The optical power measuring device according to the present invention is configured as described above, and by using an annular half mirror, the attenuation amount of the main beam power can be reduced and the amount of incident light to the light receiving element can be increased. Can be improved. Another feature is that the mechanism for detecting the optical axis shift and the focus shift between the light receiving element, the half mirror, and the CCD camera is configured without using a lens and is simplified.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the optical power measurement apparatus according to the first embodiment.

  The measuring device receives the light beam emitted from the light emitting element 1 by the light receiving element 2 and measures the power at the light receiving surface. Examples of the light emitting element 1 include an LD (Laser Diode) and an LED (Light Emitting Diode). In this embodiment, the LD is exemplified.

  In the measurement, the optical axes of the light-emitting element 1 and the light-receiving element 2 need to coincide with each other, but an annular half mirror 3 is provided between the light-emitting element 1 and the light-receiving element 2 to confirm whether or not they coincide. Based on the output of the half mirror 3, the optical axis is adjusted by detecting the shift of the focus in addition to the shift of the optical axis by the method described below.

  The annular half mirror 3 has a hollow half (transmittance 100%) at the center of the half mirror and an annular peripheral part, forming a half mirror (transmittance 50%). The beam intensity at the light receiving surface of the light receiving element 2 is shown in FIG. 2 by forming the center of the light beam that has the most influence on the measurement of the optical power of the light emitting element 1 through the hollow part of the half mirror 3. As shown in the image diagram, the power 2A at the center of the light beam is propagated to the surface of the light receiving element 2 without being attenuated, and high-precision measurement can be performed.

  On the other hand, as shown by 2B in FIG. 2, 50% of the light at the periphery of the light beam, which has a small intensity at the light receiving surface of the light receiving element 2 and hardly affects the measurement of the optical power, is reflected by the half mirror 3. As a result, a reflected beam image 5 is formed on the screen 4 and reaches the area sensor (not shown) of the CCD camera 6 to be used as position information for detecting the deviation of the optical axis.

  FIG. 3 shows the state of the reflected beam image 5 reflected on the screen 4. FIG. 3A shows a reference when the optical axes of the light receiving element 2, the half mirror 3, and the CCD camera 6 coincide. A signal 6A showing the image 5A and shown below the reference image 5A indicates the output of the CCD camera 6 in the case of the reference image 5A.

  Further, (b) shows an axis misalignment image 5B when the optical axis of the light receiving element 2, the half mirror 3, and the CCD camera 6 is misaligned, and a signal 6B shown below the axis misalignment image 5B is The output of the CCD camera 6 in the case of the off-axis image 5B is shown. Further, the signal 6A shown below the signal 6B is a reference signal in the case of the reference image 5A shown in FIG. 3A, and the signals 6A and 6B are compared at the time of axis misalignment detection, as will be described later. Therefore, it is shown here. Note that the broken line signal shown on the signal 6B is the reference signal 6A, which is also shown for easy comparison with the signal 6B.

  When an axis deviation occurs, as in the axis deviation image 5B, on the one hand, the width of the waveform is widened, and on the other hand, the waveform width is narrowed, or a dark portion is generated in a part of the captured image. Change occurs.

  Further, (c) shows a focus shift image 5C when a focus shift occurs between the light emitting element and the light receiving element, and a signal 6C shown below the focus shift image 5C is a CCD camera 6 in the case of the focus shift image 5C. Output. A signal 6A shown below the signal 6C indicates the reference signal 6A with the same purpose as in the case of (b).

  When out-of-focus occurs, the profile changes, such as the width of the waveform as a whole, or the captured image as a whole, as in the out-of-focus image 5C.

  The reflected beam image 5 and the signal corresponding thereto are taken into the image processing device 7 and image processing is performed, and the personal computer 8 and the positional information for detecting the axis deviation are calculated. That is, as shown in FIG. 3A, when no axis deviation occurs, the reference image 5 and the reference signal 6A are input, so it is determined that there is no axis deviation, and the optical axis adjustment is not performed.

Next, as shown in FIG. 3B, when an axis deviation occurs, an axis deviation image 5B and an axis deviation signal 6B are input.
The axis deviation signal 6B is compared with the reference signal 6A inputted in advance, the density difference is confirmed by the difference X between the peaks of both signals, the axis deviation is confirmed by the difference Y between the widths of both signals, and each position is determined. Information is input to the drive unit 9.

  The drive device 9 adjusts the optical axis by moving a measurement unit, which will be described later, to the left and right in FIG. 1 in accordance with the magnitude of the input signal, for position correction so that the output 2A of the light receiving element 2 becomes maximum, After that, the image profile is again taken into the CCD camera 6 and the optimum position is searched.

The measurement unit is a collection of the light receiving element 2, the annular half mirror 3, and the CCD camera 6, and these three positions are simultaneously moved by the driving device 9 to adjust the optical axis.
In the measuring unit, the optical axes of the three devices are adjusted in advance with each other, and the optical axes of the measuring unit and the light emitting element 1 are aligned based on signals from the image processing device 7 and the personal computer 8.

  Also, as shown in FIG. 3C, when a focus shift occurs between the light emitting element 1 and the light receiving element 2, a focus shift signal 6C shown in FIG. 3C is generated. The signal and the reference signal 6 </ b> A are compared, and the focus shift is confirmed by the difference Z between the widths of the two signals.

  The drive device 9 moves the above-described measurement unit up and down in FIG. 1, for example, to perform focus correction, and again takes the image profile into the CCD camera 6 and searches for the just focus position.

  The first embodiment is configured as described above, and the annular half mirror 3 is provided between the light emitting element 1 and the light receiving element 2 so that the main beam that has the most influence on the measurement is not attenuated in the light receiving element 2. Therefore, the measurement accuracy can be improved.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic diagram showing the configuration of the optical power measurement apparatus according to the second embodiment. In this figure, the same or corresponding parts as in FIG.

  The difference from FIG. 1 is that a band pass filter 10 is provided between the half mirror 3 and the light receiving element 2. The band pass filter 10 transmits light in the vicinity of the wavelength of the light emitting element 1 and makes it difficult to transmit light of other wavelengths.

  Since the second embodiment is configured as described above, the influence of background light at the time of optical power measurement can be reduced, and the measurement accuracy can be further improved.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. In this embodiment, an ND filter (Neutral Density Filter) having a small wavelength dependency is mounted instead of the bandpass filter 10 in the second embodiment. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Since the third embodiment is configured as described above, even when the output from the light-emitting element 1 is high, the attenuation is uniform regardless of the wavelength, and thus the light intensity that can be input to the light-receiving element 2 is outside the allowable range. Even high output optical power can be measured.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described. In this embodiment, when the light-emitting element 1 is a light-emitting element that emits light having a wavelength in the ultraviolet region, a fluorescent plate (not shown) is used for the screen 4 shown in FIG.

In this way, the light from the light emitting element 1 can be photographed with the CCD camera 6.
Therefore, since the CCD camera can be used as it is without using a detector for detecting light having a wavelength in the ultraviolet region, image processing is simplified.

Embodiment 5
Next, a fifth embodiment of the present invention will be described. In this embodiment, when the light-emitting element 1 is a light-emitting element that emits light having a wavelength in the near infrared (ultraviolet) region, a cooled CCD camera (not shown) is used instead of the CCD camera 6 for imaging. It is what I did.

  Cooling the CCD camera has the effect of broadening the wavelength characteristics, so it can be measured using a cooled CCD camera without using a detector that detects light in the near-infrared (ultraviolet) region. Processing is simplified.

It is the schematic which shows the structure of the optical power measuring device by Embodiment 1 of this invention. In Embodiment 1, it is an image figure which shows the beam intensity in the light-receiving surface of a light receiving element. In Embodiment 1, the state of the reflected beam image reflected on the screen is shown. (A) is a reference image when the optical axes coincide with each other, and (b) is an axis deviation when an axis deviation occurs. Image (c) shows an out-of-focus image when out-of-focus occurs. It is the schematic which shows the structure of the optical power measuring apparatus by Embodiment 2 of this invention.

Explanation of symbols

1 light emitting element, 2 light receiving element, 2A center power, 2B peripheral light,
3 annular half mirror, 4 screen, 5 reflected beam image,
5A reference image, 5B off-axis image, 5C out-of-focus image,
6 CCD camera, 6A reference signal, 6B, 6C signal, 7 image processing device,
8 PC, 9 drive, 10 band pass filter.

Claims (6)

  In the optical power measurement device for measuring the power of the light beam emitted from the light emitting element on the light receiving element side, an annular half mirror provided between the light emitting element and the light receiving element, and the half mirror reflected by the half mirror A CCD camera that detects light, an image processing device that detects an optical axis shift and a focus shift by comparing the output of the CCD camera and a reference output, and the half mirror based on a detection result of the image processing device An optical power measuring device comprising a CCD camera and a driving device for adjusting the position of the light receiving element.   2. The optical power measuring device according to claim 1, wherein a filter is provided between the half mirror and the light receiving element.   3. The optical power measuring apparatus according to claim 2, wherein the filter is a band-pass filter that transmits light having a predetermined wavelength or a wavelength in the vicinity thereof.   3. The optical power measuring device according to claim 2, wherein the filter is an ND filter having a small wavelength dependency.   2. The optical power measuring apparatus according to claim 1, wherein the light reflected by the half mirror reaches the CCD camera via a screen and a fluorescent plate is used for the screen.   2. The optical power measuring apparatus according to claim 1, wherein the CCD camera is a cooled CCD camera.

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