JPH01178832A - Apparatus for measuring light spot - Google Patents

Abstract

PURPOSE:To quantitatively and rapidly measure the intensity distribution of a light spot by extremely simple operation, by projecting and cumulating the taken image of the light spot to form a histogram and detecting the intensity distribution characteristic of the light spot from the histogram. CONSTITUTION:The original image data stored in the original image memory region ORAR of an image memory 6 is subjected to sub-scanning in a longitudinal direction and images are projected and cumulated in an X-axis direction at every respective sub-scanning lines to obtain an X-axis histogram 10. The original image data is subjected to sub-scanning in a Y-axis direction and images are projected and cumulated in a Y-axis direction at every respective sub- scanning lines to obtain a Y-axis histogram. The histograms 10, 11 are ones wherein the light spot intensity distribution of semiconductor laser is projected in the respective X- and Y-axis directions. The half-value width W1(theta, i) and half-value width W2(theta, i) of a light spot 58 and the max. intensity MS(theta, i) of the light spot 58 are detected from the histograms 10, 11. By this method, the intensity distribution of the light spot 58 is measured quantitatively and rapidly.

Description

[Detailed Description of the Invention] Industrial Field of Use] The present invention relates to a light spot measuring device used to measure the light intensity distribution of a semiconductor laser, and in particular to a light spot measuring device used for measuring the light intensity distribution of a semiconductor laser etc. The present invention relates to a light spot measuring device that captures and analyzes images using a television camera.

[Conventional technology]

Generally, laser light output from a semiconductor laser is emitted as a laser beam with a large divergence angle from a small oscillation region.

Figure 7 is a schematic configuration diagram of a double heterojunction semiconductor laser, and Figures 8 (a) and (b) explain the laser beam emitted from the semiconductor laser as shown in Figure 7. This is a diagram for

In FIG. 7, laser light from the oscillation region 56 of the semiconductor laser 60 is diffracted from the reflective surface 57 and becomes a light spot 58 at an external position P. This light spot 58 is shown in FIG.
), the maximum strength MS is
The light intensity distribution has a width of half width W and W2 in the axial direction, respectively. Note that these light intensity distributions are Gaussian distributions. The spread of the light spot 58 in the X-axis direction is due to diffraction in the horizontal transverse mode, and the spread of the light spot 58 in the Y-axis direction is due to diffraction in the vertical transverse mode.

To explain the spread of the horizontal transverse mode due to diffraction with reference to FIG. The wavefront H1 of the laser beam gradually curves due to diffraction as it advances to the reflecting surface 57, becoming wavefronts H2 and H3, and is outputted from the reflecting surface 57 to the outside as a wavefront H4.

At the external position P where this laser light is irradiated,
The wavefront H4 is further diffracted and expanded to become a wavefront H5.

This wavefront H5 is actually output from the reflecting surface 57, but due to spreading due to diffraction within the oscillation region 56, the center of the spreading appears to be 1/[[D inside of the 1 reflecting surface 57. It is shaped like there is.

On the other hand, the vertical transverse mode laser beam has a flat wavefront within the oscillation frequency region 56, and is therefore output as a plane wave from the reflecting surface 57 and is then diffracted. The origin coincides with the reflective surface 57.

As described above, laser light output from a semiconductor laser generally has a so-called astigmatism difference between the horizontal transverse mode and the vertical transverse mode, which differs by the apparent position or distance of the light source. This astigmatism difference is detected based on the intensity distribution of the light spot at the external position P, that is, the half-width W1 of the light spot 58 in the X-axis direction and the half-width W2 of the light spot 58 in the Y-axis direction.

The intensity distribution characteristic of the light spot of such a semiconductor laser, that is, the half-width W1. A light spot measuring device that measures W2, maximum intensity + HMS, and astigmatism difference is conventionally known.

Figure 9 shows the conventional light point measuring device shown in the literature 1: Semiconductor lasers and applied technology'' published on September 10, 1986 (by Hiroo Yonezu, Kogakusha), pages 192 to 193. FIG. A conventional light spot measuring device includes an industrial television camera 61 that images a light spot 58 from a semiconductor laser 60.
, a line selector 62 , a monitor television 63 , and a synchroscope 64 .

In the light spot measuring device having such a configuration, the light spot 58 from the semiconductor laser 60 that is imaged by the commercial television camera 61 is sequentially scanned by the line selector 62 and displayed on the screen of the monitor television 63. , This allows the intensity distribution of the light spot 58 to be observed.

In addition, the intensity distribution on any scanning line on the screen of the monitor television 63 is determined by the line selector 62 on the synchroscope 6.
4 will be displayed on top. Therefore, by directing the scanning line direction M, it is possible to obtain the intensity distribution of the light spot 58 in the Y-axis direction, and from this it is possible to measure the half-width W2 and the maximum intensity MS. On the other hand, if the scanning line direction is set in the willow direction, the intensity distribution of the light spot 58 in the X-axis direction can be obtained, and the half-width W1 and the maximum intensity MS can be measured from this.

Problems to be Solved by the Invention] However, in the conventional device as shown in FIG.
is only displayed with a brightness proportional to the intensity, so although it is possible to know the approximate intensity distribution of the light spot 58,
Half width W, W2.

The maximum intensity MS cannot be measured accurately.

Further, the intensity distribution on a desired scanning line is displayed on the synchroscope 64-F using the line selector 62, and the half-width W,
When measuring W, . Since the width W2 had to be determined, there were problems in that the operation was troublesome and the measurement took a considerable amount of time.

In addition, in the past, before starting measurement, the light spot was focused,
I had to perform operations such as adjusting the angle.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light spot measuring device that can quantitatively and quickly measure the intensity distribution characteristics of a light spot with extremely simple operations.

Means for Solving the Problem] The present invention provides an imaging means for imaging a light spot, and a histogram for creating a histogram by projecting and accumulating images of the light spot taken by the imaging means in a predetermined axis direction. The problems of the prior art described in "" are improved by a light spot measuring device characterized in that a creating means and a detecting means for detecting the intensity distribution characteristics of the light spot from the created histogram are provided. .

[Effect]

In the present invention, a light spot of a semiconductor laser or the like is imaged by an imaging means, and an image of the light spot taken by the imaging means is projected in a predetermined axial direction, for example, an X-axis direction or a Y-axis direction, and accumulated. Then, a histogram such as an X-axis histogram and a Y-axis histogram is created. The X-axis histogram and Y-axis histogram are
Since the intensity distribution of the light spot in the axial direction I\ is a projection, it is possible to detect the intensity distribution characteristics of the light spot, such as half-width, maximum intensity, and astigmatism difference, from these histograms using a detection means. Can be done.

[Solid line example]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic configuration diagram of a light spot measuring device of the present invention, and FIG. 2 is a flowchart showing the processing flow of the light spot measuring device shown in FIG.

In FIG. 1, a light spot measuring device 1 of the present invention is controlled by a processor 3. As shown in FIG. The processor 3 operates according to a control program stored in a read only memory (ROM) 2. Connected to the processor 3 are an industrial television camera 5 that performs a TM image of the light spot 58, an A/D converter 4, an image memory 6, a result memory 7, and a display device 8.

As shown in FIG. 3, the industrial television camera 5 can be moved to a predetermined position along the incident direction of the light spot 58 by a stepping motor (not shown), thereby enabling automatic focusing. It becomes. Further, the industrial television camera 5 is rotated by an angle θ by a stepping motor, and automatic angle adjustment is possible to image the light spot 58 at the correct position with respect to the entire screen.

The A/D converter 4 is, for example, a 16-bit one, and converts the analog image signal captured by the industrial television camera 5 into 216 bits.
This converts it into a digital image signal with gradations of .

The image memory 6 contains 216 gradations of digital data [1lii
The original image storage area 0RAt stores the original image information converted to the f-image signal, and the X-axis histogram and Y-axis L stogram obtained by sub-examining the original image @ information in the vertical and horizontal directions and cumulatively processing them are stored. X-axis histogram storage area XHAR,
A Y-axis histogram storage area YHAR is provided.

The result memory 7 also stores the half width W1 (θ, ■, W2 (θ, i),
The maximum intensity MS (θ, 1) of the light spot is stored.

The display device 8 displays not only the original image information but also the X-axis histogram, the Y-axis histogram, or the measured half-width w, w2 . i High intensity MS and astigmatic difference can also be displayed.

The operation of the light spot measuring device 1 having such a configuration will be explained using the flowchart shown in FIG. 2.

In FIG. 2, in step S1, the position i and the angle θ are set to the initial flilNT1. A flag FLG is initially set to INT2 and used for automatic focusing processing and automatic angle adjustment processing of the industrial television camera 5.

FLGI, PL, G2. GLG3. Initialize FLG4 to "0".

Next, in step S2, the half width W (
θ, l), storage area of W2(θ, 1), maximum strength MS(
Clear the storage area of θ,i).

In addition, each storage area 0RAR, XHAR, Y of the image memory 6
) Clear TAR at the same time.

After initializing the entire light spot measuring device 1 in step St, 32, in step S3, the industrial television camera 5 is positioned by a stepping motor (not shown).
affii+angle θ, and the light spot 58 from the semiconductor laser is imaged in step S4. The captured analog image signal is converted into a digital image signal with 216 gradations by the A/D converter 4 and stored in the image memory 6.
4 (a) as original image information in the original image storage area ORAR of
) is stored as shown.

At this time, a predetermined threshold value is set for the analog image signal captured by the industrial television camera 5, and the analog image signal from which signal components having a magnitude less than or equal to this threshold value is removed is converted to A/A. Improve the S/N ratio by sending it to the D converter.
The digital image signal output from the A/D converter 4 is subjected to pre-processing such as stain removal by performing predetermined matrix calculation processing on the digital image signal output from the A/D converter 4.
Good to improve the ratio.

Next, in step S5, the original image information stored in the original image storage area 0IjAFK as shown in FIG. As a result, an X-axis histogram 10 as shown in the fourth section 1(b) is obtained. Similarly, in step S6, the original image information is sub-scanned in the horizontal direction and the image is projected and accumulated in the Y-axis direction for each sub-scanning line to obtain a Y-axis histogram 11 as shown in FIG. 4(C). Such an X-axis histogram 10
．． The Y-axis histogram 11 is a projection of the light spot intensity distribution of the semiconductor laser as described above in the X-axis direction and the Y11ilt1 direction, respectively. Therefore, step S7
Now, the X-axis histogram 10. From the Y-axis histogram 11, the half-width W1 (θ.

1), the half-width W2 (θ, i>) and the maximum intensity MS (θ, i) of the light spot 58 can be detected.

That is, the maximum intensity IMs (θ, i) is determined from the maximum height of the XI-based histogram 10 or the Y-axis histogram 11, and this becomes the brightness peak of the light spot. Also, the half width W1 (θ, t), W2 (θ.

In is determined as the width of the X-axis histogram 10 and the width of the Y+Ii histogram 10 at the maximum intensity MS (1./2 of θ, i>).

By the way, in this case, in step S1, the position W 1 + angle θ of the industrial television camera 5 is set to the initial position [NT1.
The initial angle is set to INT2, ] - Wl+ of the focal point of the industrial television camera 5 and the position relative to the original image information screen.
The placement is not accurate as shown in FIGS. 4(a) to 4(C).

Therefore, as shown in FIGS. 5(a) to 5(C), the focus of the industrial television camera 5 is accurately focused (when the maximum intensity MS or the drum is large) and the original image ti? The industrial television camera 5 must be positioned so that the information is at the correct angle.

Steps S8 to S29 include such automatic focusing,
This is a process for performing automatic angle adjustment, and in particular steps S9 to S18 are automatic focusing processes, and step S2
0 to S20 are automatic focusing processing.

In step S8, it is checked whether the flag FLG is "1" to determine whether automatic focusing processing or automatic angle adjustment processing is to be performed. Flag F L G
If it is 1', the process advances to step S20 to perform automatic angle adjustment processing. In this case, since the flag FLG is "O", the process first advances to automatic focus processing in steps S9 to S18.

In the automatic focusing process, the focus or maximum intensity MS (θ, i)
Focusing on matching at the position where the maximum intensity of (θ, i) is detected.

In order to perform such automatic focusing processing, step S
In steps S10 to 314, as shown in FIG. 6(a), the position i is gradually increased to move the industrial television camera 5 forward, and in steps S15 to S18, as shown in FIG. 6(b), As shown, a backward process is performed in which the industrial television camera 5 is moved backward by gradually decreasing the position Mi.

First, in step S9, the maximum intensity MS detected at position i is
It is determined whether or not (θ, +) is greater than the maximum intensity (θ, 1-1) detected at the previous position (i-1). M.S.
When (θ, i) is larger than MS (θ, 1-1), the process advances from step S10, and MS (θ, i>
or MS(θ.

1-1), the process proceeds to step 81.5. Note that initially, MS (θ, 1-1) is “0”
Therefore, the process advances to step S10 to perform forward processing.

In step S10, the current MS (θ, i) is stored in the result memory 7, since it has a large maximum intensity at this point.

Next, in step Sll, it is determined whether the position i is the initial position glNTI. At the initial position lNT1, it cannot yet be determined that the maximum intensity is the highest, so move the position i of the industrial television camera 5 forward by one position and calculate M(θ, i) and M( θ, 1-1)
Proceed to step S14 to compare the position i with
Increase by ゛1''. On the other hand, if it is determined in step Sll that the position i is not the initial position I I NT 1, as shown in FIG.
) or MS (θ, 1-1) in the directions of arrows B and W, and the process proceeds to step SL2 to determine whether or not the state shown by LPI has been reached for the first time.

In step 312, in order to make the above judgment, it is checked whether a flag FLG2, which will be described later, is "0". Flag F
1. , when G2 is not 0'', Fig. 6(b)
This means that the backward processing has continued in the direction of the arrow BW and the LPI state position yti has been reached, so that the MS (θ, i) currently stored in the result memory 7 has the highest maximum intensity. It is determined that the MS is in focus at this position i, and the process proceeds to automatic angle adjustment processing from step 319.

On the other hand, in step 312, flag FLG2 is “0”.
When , the forward processing continues in the direction of arrow PR as shown in FIG. 6(a), and position yt is in the state of LP4, which means that the largest maximum intensity has not been detected yet. Therefore, the process advances to step S13 to continue the forward processing. In step 313, the flag FLGI is set to "1" to identify that forward processing is being performed.
″.

Then, in step S14, the position 111 is increased by 1'' to bring the industrial television camera 5 to the next forward position, and the process returns to step S3.

Further, in step S9, MS(θ, 1) is changed to MS(
θ, 1-1), the process proceeds to step 315, and in step 315, the maximum intensity MS (θ, i) currently stored in the result memory 7 is moved to the previous position (i-1). The broadside strength MS (θ, i-1>
Replace with

Thereafter, in step 316, it is determined whether it is the current position i, the position in the state shown by LP2 in FIG. 6(a), or the position in the state shown by LP3 in FIG. 6(11). In order to determine whether
Check whether 1 is "0" or not. Flag F L G 1 is “
When it is 0'°, it means that the forward processing of steps SIO to S1'4 has not been performed, so as shown in Fig. 6 (b).
), it is determined that the vehicle is in the position shown by LP3, and the process proceeds to step S17 to continue the backward process.
In step 317, the flag FLG2 is set to 1'' to identify that the backward process is being performed, and then in step 318, the position i is decreased by 1, and the process returns to step S3.

On the other hand, in step S16, flag FLGI is set to "0".
If it is determined that this is not the case, it means that the forward processing has already been performed, and the current position i is shown in FIG. 6(a) as LP2.
Since the MS (θ+1) stored in the result memory 7 has a large maximum strength MS, the next automatic angle adjustment process is performed in step S.
Proceed to step 19.

In step 319, the flag FLG is set to "l" to identify that the automatic focusing process has ended.

Next, the process proceeds to automatic angle adjustment processing in steps S20 to S29.

In the automatic angle adjustment process, if the angle of the original image information of the light spot on the screen is not correct as shown in Figure 4(a), it is adjusted to the correct angle as shown in Figure 5(a). The industrial television camera 5 is rotated clockwise or counterclockwise so that In other words, in this automatic angle adjustment process, we focused on the fact that when the angle is correct as shown in FIG. 5(a), the half-width W1(θ+i) obtained from the The rotation of the industrial television camera 5 is controlled so that the half width W1 (θ, i) is maximized.

In order to perform such automatic angle adjustment processing, step 3
In steps 21 to S25, the industrial television camera 5 is rotated clockwise by gradually increasing the angle θ in the same manner as steps 310 to 314 of automatic focusing. In steps 326 to 329, automatic focusing is performed. Similarly to steps S15 to S18 of the focusing process, a counterclockwise rotation process is performed in which the industrial television camera 5 is rotated counterclockwise by gradually decreasing the angle θ.

First, in step S20, the half width w1 detected at the angle θ
<θ, i) is larger than the half-width W1 (θ-1.i) detected at the angle (θ-1) of one song. When Wi (θ, i) is larger than Wl (θ−1, i), the process proceeds to right rotation processing from step S21,
When Wl (θ, ■) is smaller than Wl (θ-1.i), the process proceeds to the left rotation process from step S26. Note that since Wl(θ-1.i) is “0” at first, step S
The process proceeds to step 21, where a clockwise rotation process is performed.

In step S21, since the current Wi (θ, i) has the largest half-width at the moment, Wl (θ,
1) and W2(θ, 1) are stored in the result memory 7.

Next, in step S22, it is determined whether the angle is the initial angle INT2. When the initial angle I N T is 2, it cannot yet be determined whether it is the largest half g3 width, so the angle θ of the industrial television camera 5 is rotated one step clockwise and the current Wl ( θ+1)
In order to compare Wl (θ-1, 1), the process proceeds to step S25 and the angle θ is increased by 1". On the other hand, if it is determined in step S22 that the angle θ is not the initial angle INT2, then Wl (θ, i) is Wl (
θ-1. It is smaller than i) and rotates counterclockwise, and for the first time Wl (θ, i) becomes Wl (θ−1゜i
), the process advances to step 323 to determine whether or not it is larger than .

In step 323, in order to make the above judgment, it is checked whether a flag FLG4, which will be described later, is "0". Flag F
If LG4 is not "0", it means that the left rotation process has continued until now, so the current memory 7 is
Wl(θ+1) stored in is the largest half width W1, and when this angle θ, it is determined that the original image information is at the correct angle with respect to the screen, and the automatic angle adjustment process is terminated.
The process proceeds to step 330, which is an astigmatism difference detection process.

On the other hand, if the flag FLG4 is "0" in step 323, it means that the clockwise rotation process has been continued and the largest half width has not yet been detected, so the process advances to step S24 to further continue the clockwise rotation process. . At step 324, the flag FLG3 is set to 1'° to identify that the clockwise rotation process is being performed. Next, in step 325, the industrial television camera 5 is
The angle θ is increased by "1'' to make it a clockwise angle, and the process returns to step S3 again.

Also, in step 320, Wl (θ, i) is W
l (θ-1.i), the process proceeds to step 326 of left rotation processing, and in step S26, the half-width W1 currently stored in the result memory 7
(θ, 1), W2 (θ, i) is the previous angle (θ-1
) at half-value width W1 (θ-i, 1), W2 (θ-
1. Replace with i).

Thereafter, in step 327, it is checked whether the flag FLG3 is "0" in order to determine whether the clockwise rotation process has been performed until the current angle θ is reached.

When the flag FLG3 is “0”, step S
This means that the clockwise rotation processing of 22 to 325 has not been performed, so the largest half-width has not yet been detected and the process advances to step S28 to continue the counterclockwise rotation processing. In step S28, the flag FLG4 is set to ``1'' to identify that the counterclockwise rotation process is being performed, and then the corner eave θ is decreased by 1, and the process returns to step S3.

On the other hand, in step S27, the flag FLG3 is “0”.
'', it means that the right rotation process has already been performed, so the current angle θ is the angle that gives the largest half width W1, and the original image information is at the correct angle with respect to the screen. Therefore, the automatic angle matching process is ended and the process proceeds to astigmatism difference detection process in step S30.

When automatic focus sharpening processing and automatic angle alignment processing are performed in this way, the original image storage area OI'b of the image memory 6 is
Original image information is stored in AR as shown in FIG. 5(a), and in this case, as shown in FIG. 5(fb).

The X-axis histogram to' and the y-axis histogram 11' as shown in (C) are obtained, and these are shown in Fig.
X-axis histogram in 10. Y-axis histogram 11
As can be seen from the comparison, when the industrial television camera 5 is accurately focused and angularly adjusted, the maximum intensity MS and the half-width W1 are the largest, and the half-width W2 is the smallest.

In step S30, the astigmatism difference is determined from the half-width W1°W2 in this state. Then, in step S31, the astigmatism difference obtained in step S30 and the final maximum intensity MS, half-width W, and W2 stored in the result memory 7 are displayed on the screen of the display. It is assumed that the original image information obtained in step S4, the X-axis histogram 10 and the Y-axis histogram 11 obtained in steps S5 and S36, etc. are displayed on the display device 8 each time these processes are performed.

As described above, according to this embodiment, the original image storage V40
An X-axis histogram 10' and a Y-axis histogram 11' are created from the original image information stored in RA R, and the maximum intensity MS, half-width W1°W2. Since the astigmatism difference is detected at the same time and the result is displayed on the display device 8, the operator can easily scan the furnace temperature in a short time and without any need for X selection operations. It is also possible to measure the intensity distribution characteristics of a light spot.

Furthermore, the X-axis histogram 10. The maximum intensity MS (θ) detected each time from the Y-axis histogram 11.

1) If automatic focusing and automatic angle adjustment of the light spot of the industrial television camera 5 are performed based on + half width W1 (θ, i), the astigmatism can be achieved without requiring operator operation. Since the distance difference, the half width W2, W2, and the maximum intensity MS are accurately detected, it becomes possible to significantly improve the operability and the measurement accuracy of the intensity distribution characteristics of the light spot.

Note that if the industrial television camera 5 is accurately positioned in advance with respect to the light spot to be measured, it is not necessary to perform the automatic focus processing and automatic angle adjustment processing by the Stellar Pink motor.

Furthermore, even if automatic angle adjustment processing is performed by rotating the industrial television camera 5, affine transformation is performed by applying a rotation operator to the original image information at an incorrect angle as shown in FIG. 4(a). Information on the original image at the correct angle as shown in FIG. 5(a) may be obtained through software processing.

[Effects of the Invention] As explained in 1- below, according to the present invention, a histogram is created by projecting and accumulating captured images of a light spot in a predetermined axis direction, and the intensity distribution characteristics of the light spot are determined from this histogram. Since the light spot is detected, the intensity distribution of the light spot can be measured stationarily and quickly with extremely simple operations.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the light spot measuring device of the present invention, and Fig. 2 is a block diagram of the light spot measuring device of the present invention.
A flowchart (not shown) showing the processing flow of the light point measuring device, Figure 3 is a diagram to explain the movement and rotation of an industrial television camera, and Figure 4 is a diagram for explaining the focus, alignment, and angle adjustment of an industrial television camera. FIG. 4(a) is a diagram showing original image information, and FIG. 4(b) and (C) are X-axis histograms and Y-axis histograms, respectively. FIG. 5 is a diagram showing an axial histogram, and is a diagram for explaining the light spot intensity distribution characteristics of an industrial television camera when the focus and angle are adjusted. Diagram showing information, Figure 5 (#)
. (C) is a diagram showing an X-axis histogram and a Y-axis histogram, respectively, FIG. 6 is a diagram for explaining focusing of an industrial television camera, and FIG. 6(a) is a diagram for explaining forward processing. Figure 6(b) is a diagram for explaining the retreat process, Figure 7 is a diagram showing a general semiconductor laser, and Figure 8(a) is the light output from the semiconductor laser shown in Figure 7. Figure 8 (kl) is a diagram showing the wavefront of the horizontal transverse mode light output from the semiconductor laser shown in Figure 7. Figure 9 is a diagram showing the conventional light spot measurement. It is a block diagram of a device. Agent for patent use Hamamatsu Potonics Co., Ltd.
Patent Attorney Masa Tomari Uemoto Figure 3 Figure 4 Figure 12 Figure 5 Figure 6 Figure 7 Figure 8 (a) (b)

Claims (1)

[Claims] an imaging means for imaging a light spot; a histogram creation means for creating a histogram by projecting and accumulating images of the light spot taken by the imaging means in a predetermined axis direction; and an intensity distribution characteristic of the light spot based on the created histogram. A light spot measuring device comprising: a detection means for detecting.