JP2004128027A - Semiconductor laser radiation angle measuring device and radiation angle measuring method - Google Patents

Abstract

An object of the present invention is to provide a semiconductor laser radiation angle measuring system which can be measured at a high speed without an operating section, has a higher resolution, does not use a lens, and can easily calibrate an optical axis center.
The length of the one-dimensional sensor 102 light receiving section in the longitudinal direction is L, the size of the minimum pixel 103 of the one-dimensional sensor 102 light receiving section is S, the light emitting point of the semiconductor laser element 101 and the one-dimensional sensor 102 light receiving section. Where D is the vertical distance from
450 × S ≦ D ≦ 0.5 × L and L ≧ 900 × S
1 is a radiation angle measuring device for a semiconductor laser having a configuration in which the following relationship is established.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for evaluating characteristics of a semiconductor laser used in fields such as optical information processing, optical measurement, and optical communication.
[0002]
[Prior art]
2. Description of the Related Art A semiconductor laser device (hereinafter, referred to as an LD) is used as an optical disk recording device such as a compact disk (CD) or a signal light source for a laser printer or the like. Since the emitted light of the semiconductor laser is diffused light, it is generally condensed and used by an optical system such as a lens. Since the radiation angle and the tilt angle of the center of the optical axis are the basis of the design of a lens and an optical system, reproducibility and stability are required, and are one of the important basic characteristics of a laser. Further, due to the improvement in the design accuracy of the optical system, the measurement accuracy is required to have a resolution of 0.1 ° or less.
[0003]
As a method for measuring the radiation angle, a method in which a sensor scans a light receiving surface of a laser beam (for example, see Patent Document 1), and a method of collectively measuring the light intensity distribution of the light receiving surface using a CCD (for example, see Patent Document 2) ), A method of inspecting the lateral spread of a beam using a divided light receiving element or a CCD (for example, see Patent Document 3).
[0004]
FIG. 7 shows a configuration diagram of a conventional scanning-type radiation angle measuring apparatus. The light emitted from the LD 701 spreads upward. An arm having the light receiving element 703 fixed at the tip moves an angle of about 60 ° (± 30 °) about the axis, and measures the light intensity from the LD 701. When the light intensity is plotted against the angle θ at which the arm moves, the light intensity profile of the LD 701 is obtained. The origin of the angle (0 °) is an angle perpendicular to the reference plane including the light emitting point.
[0005]
FIG. 8 shows an example of this measurement result. The emitted light of the LD has an intensity profile that can be approximated by a Gaussian distribution, the full width at half maximum of the emission angle when the intensity becomes half the peak value (hereinafter referred to as the emission angle), and the optical axis deviated from the origin. (Hereinafter, referred to as an optical axis tilt angle). Since the emission angle of the LD has a vertical direction and a horizontal direction, measurement is performed using two such scanning devices. Further, as the light receiving surface of the light receiving element is smaller, the intensity of the received light is lower, but the angular resolution can be improved. Therefore, a slit is provided in front of the light receiving element to increase the resolution. However, in a measurement system having such an operating section, a time for moving the light receiving element is required, and thus there is a disadvantage that the measurement time is long.
[0006]
FIG. 9 shows the configuration of a radiation angle measuring device using a CCD. The size of the CCD 902 is as small as about 1/2 inch (about 1.8 cm) to about 1/3 inch, even if it has several million pixels. Therefore, the light emitted from the LD 901 is condensed by condensing means such as a lens 911 and then is irradiated on the CCD 902. The output signal from the CCD 902 is converted into an intensity distribution on the xy plane by a computer, and the radiation angles in the x and y directions are obtained.
[0007]
However, in this example, light emission characteristics can be measured, but simultaneous measurement of the optical axis tilt angle is not performed.
[0008]
In addition, a method of inspecting the lateral spread of a beam using a divided light receiving element or a CCD is a method for easily inspecting that the lateral mode of an LD changes depending on an injection current using a three-part light receiving element. Things. In other words, when the output signal of the left and right light receiving elements has a larger change amount than the output signal of the central light receiving element divided into three, it is determined that the lateral mode has changed.
[0009]
[Patent Document 1]
JP-A-2001-85783 (FIG. 7 on page 2-3)
[Patent Document 2]
JP-A-6-94515 (FIG. 1 on page 3)
[Patent Document 3]
JP-A-2001-50859 (FIG. 1 on page 8)
[0010]
[Problems to be solved by the invention]
However, in order to measure the inclination of the optical axis from the origin with the configuration shown in Patent Document 2, an optical element such as a lens is aligned in a direction perpendicular to the light emitting point of the LD, and each optical element Must bend the optical axis. FIG. 9 shows the shift of the optical axis when the axis of the LD and the lens is shifted by a broken line. A similar shift occurs when the position where the LD 901 is fixed is shifted and the relative position with respect to the lens 911 is changed. Due to this shift, it is difficult to obtain an accurate optical axis tilt angle.
[0011]
Further, according to the configuration disclosed in Patent Document 3, the excitation intensity dependence of the difference or ratio of the output signals of the divided light receiving elements is obtained, and no method for obtaining the absolute value of the divergence angle of light is disclosed. Further, since it is assumed that a specific light receiving element coincides with the optical axis, it is impossible to measure the optical axis shift at the same time.
[0012]
Further, depending on the configuration of the LD package, light emitted from the LD may be vignetted at the exit window of the package, interference due to reflected light, and lack of profile may occur. An example of the waveform in this case is shown in FIGS. It is difficult to observe these waveforms with a three-division light receiving element, and when measuring with a CCD, a large number of pixels is required, but the CCD itself is expensive.
[0013]
Further, in a radiation angle measurement system using a CCD or the like, since a plurality of optical components such as lenses are used in the optical system, it is difficult to adjust and manage all the optical axes in order to calibrate the optical axis tilt. Occurs.
[0014]
SUMMARY OF THE INVENTION An object of the present invention is to provide a measurement system which can perform high-speed measurement without an operation unit, has a high resolution, does not use a lens, and can easily calibrate an optical axis center.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a semiconductor laser radiation angle measuring apparatus according to the present invention comprises a one-dimensional sensor light-receiving unit having a longitudinal length of L, a minimum pixel size of the one-dimensional sensor light-receiving unit of S, When the vertical distance between the laser emission point and the one-dimensional sensor light receiving unit is D,
450 × S ≦ D ≦ 0.5 × L and L ≧ 900 × S
The following relationship is established, and the radiation angle and the tilt of the optical axis are measured simultaneously in a very short time without complicated optical axis adjustment.
[0016]
In addition, the method for measuring the radiation angle of a semiconductor laser according to the present invention is to measure the intensity distribution of a laser beam a plurality of times at different time widths and combine the measurement results to obtain the light intensity distribution.
[0017]
In another radiation angle measuring method for a semiconductor laser according to the present invention, the one-dimensional sensor is moved by a half pixel in the long side direction of the sensor, and the light intensity distribution is measured to improve the resolution of the measuring system.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
FIG. 1 shows a configuration of a semiconductor laser radiation angle measuring apparatus according to a first embodiment of the present invention.
[0019]
Light emitted from the LD 101 contained in the package 106 having the sealing glass plate 107 is reflected by the reflection mirror 105 on the silicon submount 104, and is emitted to the outside through the sealing glass plate 107. . The emitted light is incident on a sensor 102 in which pixels 103 having a size S are arranged one-dimensionally in a light receiving portion having a length L in a longitudinal direction, which is arranged on an upper part of a package 106. The sensor 102 is arranged such that the longitudinal direction of the sensor 102 and the installation surface of the LD 101 are substantially parallel. In this sensor, a CCD is used as a pixel, and the capacitance changes in proportion to the amount of incident light, and an electric signal proportional to the capacitance is output.
[0020]
Unlike a two-dimensional CCD, the pixels are arranged one-dimensionally, so that the number of pixels in one direction can be increased and a high resolution can be realized.
[0021]
Next, the relationship between the LD 101 and the one-dimensional sensor 102 and the pixels 103 in the one-dimensional sensor will be described with reference to FIG. In the present embodiment, it is assumed that the optical axis of the laser beam is perpendicular to the light receiving surface of the one-dimensional sensor 102.
[0022]
The vertical distance between the LD 101 and the one-dimensional sensor 102 is D, and the point at which the optical axis of the laser beam intersects the one-dimensional sensor 102 is half the point at which the light intensity on the one-dimensional sensor 102 corresponds to the optical axis of the laser beam. Assuming that the distance to the point is X and the emission angle of the light emitted from the LD 101 is θ, these relationships are:
tan θ = X / D (Equation 1)
Is represented by The condition under which the one-dimensional sensor 102 can measure the radiation angle is as follows, assuming that the length of the light receiving unit is L
L ≧ 2X = 2tan θ × D (Equation 2)
It is. On the other hand, in order to measure with an angular resolution of 0.1 ° or less,
S ≦ 0.1X / θ = 0.1 × tan θ × D / θ (Equation 3)
Need to be Therefore, from (Equation 2) and (Equation 3), the range of D is determined as follows.
[0023]
10θ × (1 / tan θ) × S ≦ D ≦ L / 2tan θ (Equation 4)
The emission angle of the light emitted from the LD 101 normally falls within a range of ± 30 °, and thus is often measured in this range as described above. However, when the LD is housed in a package or the like, light that spreads beyond this range is scattered in the package, returning light to the laser and causing noise. Therefore, measurement in a wider range is required. Further, as described above, since the emitted light from the LD is vignetted by the emission window of the package, the detected light has many noise components, and the resolution may be reduced. Considering these facts, the configuration must be capable of measuring up to the range of ± 45 °. Therefore, in Equation (4), θ = 45 ° and 450 × S ≦ D ≦ 0.5 × L (Equation 5)
The following relationship must be established. From the definition of resolution, L ≧ 900 × S (Equation 6)
Must also be established at the same time.
[0024]
According to the present embodiment, when the distance between the LD and the one-dimensional sensor, the length of the light receiving portion of the one-dimensional sensor, and the size of the pixel are defined as described above, the case where the LD is housed in the package As described above, even when the measurement light itself is greatly affected by disturbance, the radiation angle can be measured sufficiently and a high resolution can be secured. In addition, the tilt angle of the optical axis can be measured in one measurement simultaneously with the emission angle.
[0025]
Further, in this embodiment, about 10,000 CCDs are arranged one-dimensionally, a sensor having a light receiving portion having a length of about 50 mm is used, and the vertical distance D between the one-dimensional sensor and the LD is set to 25 mm or less. . According to the present embodiment, since the one-dimensional sensor is sufficiently long, the light emitted from the LD can be detected without being collected by the lens. This eliminates the need for a precise optical axis of the measurement system.
[0026]
In general, the optical axis of the laser beam does not coincide with a virtual straight line extending from the light emitting point to the one-dimensional sensor perpendicularly. In this case, from the light intensity distribution collectively measured by the one-dimensional sensor 102, the peak value of the light intensity, the coordinates x0 on the one-dimensional sensor, and the coordinates x1 and x2 at which the light intensity becomes a half value are obtained, and the distance D is calculated. Is obtained in advance, in the range where the inclination of the optical axis is small, the radiation angle θ and the optical axis inclination angle Δθ can be calculated by the following equations.
[0027]
θ = tan ⁻¹ {(x1 + x2) / 2D} (Expression 7)
Δθ = tan ⁻¹ (Δθ / D) (Expression 8)
According to the present embodiment, the radiation angle can be measured in a very short time because there is no moving part such as an arm as compared with the conventional embodiment. As an example, in the conventional scanning method, it took 15 seconds for each of the vertical and horizontal radiation angle measurement, but in the present method, the measurement can be completed in 1 second or less.
[0028]
Moreover, the vertical radiation angle and the horizontal radiation angle of the LD can be measured using two one-dimensional sensors. In this case, the measurement time can be shortened by moving the rail on which the LD is mounted and measuring the vertical and horizontal simultaneously.
[0029]
FIG. 2 shows another configuration of the semiconductor laser radiation angle measuring apparatus according to the first embodiment of the present invention. As shown in FIG. 2, the LD 201 is mounted on the rail 208, and the horizontal and vertical radiation angles are determined by the first one-dimensional sensor 202 and the second one-dimensional sensor 202a which are spaced apart from each other and arranged orthogonally. The radiation angles are measured separately.
[0030]
According to this configuration, the measurement time is increased because two measurements are performed for one LD, but the radiation angle in the orthogonal direction can be measured without rotating the LD, so that the rotation error is reduced. Measurement with high accuracy not including Further, by mounting a plurality of LDs on the rail and moving the rail, measurement can be performed continuously, and it is possible to suppress an increase in the overall measurement time.
[0031]
Also, as shown in FIG. 3, the beam splitter 309 divides the light emitted from the LD 301 into a traveling direction of the original emitted light and a direction orthogonal thereto, and separates the divided lights from each other. The measurement can also be performed simultaneously using the first one-dimensional sensor 302 and the second one-dimensional sensor 302a arranged orthogonally.
[0032]
According to this configuration, although the amount of light incident on each one-dimensional sensor decreases, the radiation angles in orthogonal directions can be measured at the same time, so that highly accurate measurement can be performed without increasing the measurement time.
[0033]
The LD shown in FIGS. 2 and 3 may be contained in a package.
[0034]
(Second embodiment)
FIG. 4 is a diagram illustrating a relationship between a measurement time and an electric signal intensity in the one-dimensional sensor according to the second embodiment of the present invention.
[0035]
The relationship between the one-dimensional sensor and its pixels, the LD, and the one-dimensional sensor in the present embodiment is the same as that in the first embodiment.
[0036]
The dynamic range of a one-dimensional sensor is generally small, up to about 32 gradations as in the present embodiment. When the incident light exceeds a certain level, the output signal is saturated. Therefore, a quantization error of about 3% occurs, and it is impossible to measure a detailed radiation angle. The limit level at which the output signal with respect to the incident signal light becomes non-linear is referred to as a saturation level Vsat.
[0037]
As a method of expanding the dynamic range, in the present embodiment, a signal is detected by a two-stage capturing method. First, the capturing is performed for a short time T1 so as not to saturate even strong light. Next, in the second time, data is taken in a longer time T2 so that sensitivity can be obtained even for minute light. Then, the output signal V2 is compared with the saturation level Vsat for each pixel.
[0038]
In the present embodiment, T2 is set to be twice as long as T1, and a saturated signal (V2> Vsat) of the pixel output signal V2 is replaced with V1, and a non-saturated signal (V2 ≦ Vsat). ) Is 0.5 × V2 and data is synthesized (FIG. 5). By performing such processing, the dynamic range of the one-dimensional sensor can be substantially improved to measure the radiation angle, and the measurement accuracy does not deteriorate.
[0039]
In particular, when the LD is housed in a package, the one-dimensional sensor and its minimum pixel, the relationship between the LD and the one-dimensional sensor are defined as in the first embodiment, and the radiation angle measurement is performed by the method according to the present embodiment. Is effective because the influence of noise can be suppressed.
[0040]
In the present embodiment, two-stage data acquisition is performed, but a higher dynamic range can be realized by synthesizing data by measuring at three or more stages.
[0041]
(Third embodiment)
FIG. 6 shows a configuration of a semiconductor laser radiation angle measuring apparatus according to the third embodiment of the present invention.
[0042]
The light emitted from the LD 601 contained in the package 606 having the sealing glass plate 607 is reflected by the reflection mirror 605 on the silicon submount 604, passes through the sealing glass plate 607, and is emitted to the outside. . The emitted light enters a sensor 602 in which pixels 603 having a size S are arranged one-dimensionally in a light receiving portion having a length L in a longitudinal direction, which is arranged on an upper part of a package 606. Here, the one-dimensional sensor is the same as that shown in the first embodiment, and the one-dimensional sensor and its pixels, and the relationship between the LD and the one-dimensional sensor are also the same as in the first embodiment.
[0043]
Once the intensity of the emitted light is measured, the fine movement device 610 provided on the one-dimensional sensor 602 is operated to move the sensor in the longitudinal direction by half the size of one pixel of the one-dimensional sensor 602. In this state, the output light intensity is measured again.
[0044]
In the case of this embodiment, since the size of one pixel is 5 μm, the sensor is moved by 2.5 μm.
[0045]
Next, the first measurement data and the second measurement data are alternately arranged for each pixel to synthesize data. By such pixel shifting, the number of effective sensor pixels can be doubled, that is, the angular resolution can be halved. According to the one configuration shown in the first embodiment, the angular resolution is about 0.01 °, and according to the present embodiment, it is possible to improve the angular resolution to 0.005 °.
[0046]
In the present embodiment, a piezoelectric element that moves in sub-micron units by applying a voltage is used as the fine movement device, but a motor that is driven by electricity may be used.
[0047]
Further, in the first to third embodiments, the package in which the sealing glass plate is provided on the upper portion is described, but the entire package may be made of a light transmitting material such as plastic.
[0048]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the radiation angle measuring device of the semiconductor laser of this invention, by defining the one-dimensional sensor and its minimum pixel, and the relationship between LD and the one-dimensional sensor, it is possible to measure a wide range of radiation light without passing through a lens. Since there are few optical axis adjustment points and no moving parts, measurement can be performed in a short time.
[0049]
According to the method for measuring the radiation angle of a semiconductor laser of the present invention, the intensity distribution of strong light is extracted from data measured in a short time, and the intensity distribution of weak light is extracted from data measured in a long time, and the two are combined. By doing so, it is possible to obtain substantially the same effect as using a sensor having a wide dynamic range.
[0050]
Further, by measuring the light intensity distribution twice by shifting the one-dimensional sensor by half the length of one pixel and combining the two alternately, the effect of substantially doubling the angular resolution of the measurement system can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a semiconductor laser radiation angle measuring device according to a first embodiment of the present invention; FIG. 2 is another configuration diagram of a semiconductor laser radiation angle measuring device according to the first embodiment of the present invention; 3 is still another configuration diagram of the semiconductor laser radiation angle measuring device according to the first embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the measuring time and the electric signal intensity in the second embodiment of the present invention. FIG. 5 is a flowchart for converting and synthesizing electric signal intensity according to a second embodiment of the present invention. FIG. 6 is a configuration diagram of a semiconductor laser radiation angle measuring apparatus according to a third embodiment of the present invention. FIG. 8 is a configuration diagram of a scan-type semiconductor laser radiation angle measuring device according to the related art. FIG. 8 is a diagram illustrating a radiation angle measurement result of the semiconductor laser according to the related art. Radiation angle measurement A radiation angle measurement results when the block diagram Figure 10. The semiconductor laser of location is housed in a package,
(A) A diagram showing a result when interference noise occurs due to reflected light inside the package. (B) A diagram showing a result when data loss occurs due to reflected light inside the package.
101, 201, 301, 601, 701, 901 Semiconductor laser element 102, 602, 702, 902 One-dimensional sensor 103 One-dimensional sensor pixel (CCD)
104, 604 Silicon submount 105, 605 Reflecting mirror 106, 606 Package 107, 607 Sealing glass plate 202, 302 First one-dimensional sensor 202a, 302a Second one-dimensional sensor 208, 708 Rail 309 Beam splitter 610 Primary Original sensor fine movement device 911 Condensing lens

Claims (8)

A one-dimensional sensor that receives light emitted from the semiconductor laser and converts the light into an electric signal,
The length in the longitudinal direction of the one-dimensional sensor light receiving unit is L, the size of the pixel of the one-dimensional sensor light receiving unit is S, and the vertical distance between the light emitting point of the semiconductor laser and the one-dimensional sensor light receiving unit is D. When
450 × S ≦ D ≦ 0.5 × L and L ≧ 900 × S
A radiation angle measuring device for a semiconductor laser, wherein the following relationship is established. A first one-dimensional sensor and a second one-dimensional sensor spaced apart from each other and arranged orthogonally;
A moving mechanism having a semiconductor laser mounted on a plane parallel to a light receiving surface of the first and second one-dimensional sensors,
The length in the longitudinal direction of the first one-dimensional sensor light receiving portion is L1, the size of the pixel of the first one-dimensional sensor light receiving portion is S1, the light emitting point of the semiconductor laser and the first one-dimensional sensor light receiving portion. When the vertical distance to the part is D1,
450 × S1 ≦ D1 ≦ 0.5 × L1 and L1 ≧ 900 × S1
And the length in the longitudinal direction of the second one-dimensional sensor light receiving portion is L2, the size of the pixel of the second one-dimensional sensor light receiving portion is S2, and the light emitting point of the semiconductor laser is When the vertical distance from the second one-dimensional sensor light receiving unit is D2,
450 × S2 ≦ D2 ≦ 0.5 × L2 and L2 ≧ 900 × S2
A radiation angle measuring device for a semiconductor laser, wherein the following relationship is established. A first one-dimensional sensor and a second one-dimensional sensor spaced apart from each other and arranged orthogonally;
A beam splitter that splits light emitted from the semiconductor laser and guides the light to the first one-dimensional sensor and the second one-dimensional sensor, respectively.
The length in the longitudinal direction of the first one-dimensional sensor light receiving portion is L1, the size of the pixel of the first one-dimensional sensor light receiving portion is S1, the light emitting point of the semiconductor laser and the first one-dimensional sensor light receiving portion. When the vertical distance to the part is D1,
450 × S1 ≦ D1 ≦ 0.5 × L1 and L1 ≧ 900 × S1
And the length in the longitudinal direction of the second one-dimensional sensor light receiving portion is L2, the size of the pixel of the second one-dimensional sensor light receiving portion is S2, and the light emitting point of the semiconductor laser is When the vertical distance from the second one-dimensional sensor light receiving unit is D2,
450 × S2 ≦ D2 ≦ 0.5 × L2 and L2 ≧ 900 × S2
A radiation angle measuring device for a semiconductor laser, wherein the following relationship is established. The radiation angle of the semiconductor laser according to claim 1, wherein a light condensing unit is not provided on an optical path until the light emitted from the semiconductor laser is incident on the one-dimensional sensor. measuring device. The semiconductor laser is housed in a package, the package includes a member that transmits light emitted from the semiconductor laser, and light emitted from the semiconductor laser is emitted to the outside of the package through the member. 5. An apparatus for measuring a radiation angle of a semiconductor laser according to claim 1, wherein: 6. The semiconductor according to claim 1, further comprising: a mechanism for moving the one-dimensional sensor along a direction perpendicular to a direction perpendicular to the light-emitting point of the one-dimensional sensor and the semiconductor laser. Laser radiation angle measuring device. A method for measuring a radiation angle of a semiconductor laser using the radiation angle measuring device according to claim 1,
Measuring a first light intensity distribution of the semiconductor laser at a first measurement time T1,
Measuring a second light intensity distribution of the semiconductor laser at a second measurement time T2 longer than the measurement time T1,
In the information of the second light intensity distribution, the information exceeding the saturation level of the one-dimensional sensor includes information of the first light intensity distribution at the position in the one-dimensional sensor in T1 with respect to the measurement time T2. Substituting the information multiplied by the ratio;
Simultaneously calculating a radiation angle and a tilt of an optical axis of the semiconductor laser from information of the second light intensity distribution in which information exceeding a saturation level of the one-dimensional sensor is replaced. Measuring method. A method for measuring a radiation angle of a semiconductor laser using the radiation angle measuring device according to claim 6,
Measuring a first light intensity distribution of the semiconductor laser,
Moving the one-dimensional sensor a distance of half the size of the pixel;
Measuring a second light intensity distribution of the semiconductor laser,
Arranging the position information of the first light intensity distribution and the position information of the second light intensity distribution alternately, and calculating a third light intensity distribution from these information,
Calculating a radiation angle of the semiconductor laser and a tilt of the optical axis simultaneously from the information on the third light intensity distribution.

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