JPH04315926A - Radiative property measuring device of laser diode - Google Patents

Abstract

PURPOSE:To obtain a radiative property measuring device of a laser diode of a high accuracy of measuring position even though its optical path is made longer. CONSTITUTION:A reflecting mirror 2 to reflect the radiating light of a laser diode 1 is attached to an arm 4, the arm 4 is rotated around a rotation axis 5, and the reflected light of the reflecting mirror 2 is received by a receiving element 3. The extension 11 of the rotation axis 5 and a normal 12 passing through the center 3A of the luminous surface of the receiving element 3 are made coincident, while a normal 13 passing through the center 1A of the luminous surface of the laser diode 1 and the extension 11 of the rotation axis 5 are crossed square, the arm 4 is provided parallel to the normal 13, the normal 13 is reflected at the reflection point 2A of the reflecting mirror 2, it is crossed with the normal 12 by a normal 14 passing through the reflection point 2A, and the angle alpha composed by the point 3A-the point 2A-the point 1A is divided into two equal angles.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a laser diode (
Hereinafter referred to as LD. ) concerning the radiation characteristic measuring device.

0002

2. Description of the Related Art Next, the configuration of a conventional LD radiation characteristic measuring apparatus will be explained with reference to FIG. In FIG. 4, 1 is an LD to be tested, 3 is a light receiving element (hereinafter referred to as PD), 4 is an arm, 5 is a rotating shaft, and 6 is a drive device. The radiation characteristic of the LD 1 is called FFP, and can be expressed by the light intensity on a concentric circle centered on the center of the light emitting surface on a plane including the normal to the light emitting surface of the LD 1. FFP is usually the vertical axis F
It is evaluated using two parameters: FP and horizontal axis FFP.

In FIG. 4, the PD 3 is attached to the arm 4,
The arm 4 is rotated by the drive device 6, and the light intensity on a concentric circle centered on the LD1 is measured. For switching between vertical axis FFP measurement and horizontal axis FFP measurement, for example, actual fairness 2-
It is described in No. 49556.

0004

[Problems to be Solved by the Invention] FIG. 4 has the following problems. A. Since the positional accuracy of the arm 4 is the measurement accuracy, the rotation mechanism of the arm 4 is required to have high accuracy and stability. (a) Especially when the light emitting area of LD1 is large due to high output, it is necessary to lengthen the optical path length, rotate PD3, and lengthen the radius of the concentric circles for measurement. C. Measurement takes time because the arm 4, which has a large shape, is rotated and stopped while being measured. D. Since the PD3 is mounted on the rotating arm 4, it becomes difficult to connect the PD3 and the measuring section.

[0005] This invention places the PD 3 on an extension of the rotation axis, attaches a reflector to the arm 4 that rotates with the rotation of the rotation axis, reflects the output light of the LD 1 on the reflector, and converts the reflected light from the reflector. It is an object of the present invention to provide an LD radiation characteristic measuring device in which light is received by a PD 3 and the measurement position accuracy is high even if the optical path length becomes long.

[0006]

[Means for Solving the Problems] In order to achieve this object, in the present invention, a reflector 2 that reflects light emitted from a laser diode 1 is attached to an arm 4, and the arm 4 is rotated about a rotation axis 5 to reflect the light emitted from the laser diode 1. The reflected light of the mirror 2 is received by the light receiving element 3, and the extension line 11 of the rotation axis 5 and the normal line 12 passing through the center point 3A of the light receiving surface of the light receiving element 3 are aligned, and the center 1A of the light emitting surface of the laser diode 1 is aligned. The normal line 13 passing through and the extension line 11 of the rotation axis 5 are made orthogonal, and the arm 4 is arranged parallel to the normal line 13. The normal line 13 is reflected at the reflection point 2A of the reflecting mirror 2, and the
Normal line 14 passing through A intersects normal line 12 to point 3A-2A-
Divide the angle α composed of 1A into two equal parts.

Next, the configuration of an LD radiation characteristic measuring apparatus according to the present invention will be explained with reference to FIG. Reference numeral 2 in FIG. 1 is a reflecting mirror, and the other parts are the same as in FIG. 4. That is, Figure 1
The PD3 attached to the arm 4 in FIG. 4 is removed from the arm 4 and placed on the extension line 11 of the rotation axis 5, the reflector 2 is attached to the arm 4, and the output light of the LD1 is reflected by the reflector 2. , the reflected light from the reflecting mirror 2 is received by the PD 3.

Next, the front view of FIG. 1 will be explained with reference to FIG. 2. In FIG. 2, the LD1, reflecting mirror 2, PD3, and arm 4 are arranged in the following relationship. FIG. 3 is a side view of FIG. 1. A. Align the extension line 11 of the rotation axis 5 with the normal line 12 passing through the center 3A of the light receiving surface of the PD 3. B The extension line 11 of the rotation axis 5 is the center 1 of the light emitting surface of the LD 1
A and the normal line 13 passing through the center 1A and the extension line 11 are made perpendicular to each other. C. The arm 4 is made parallel to the normal line 13, the normal line 13 is reflected at the reflection point 2B of the reflecting mirror 2, and the normal line 14 passing through the reflection point 2B
intersects the normal line 12 and bisects the angle α formed by angles 3A-2A-1A.

[0009]

[Operation] When viewed from the center point 1A of the light emitting surface of LD1, PD
A center point 3A of the light-receiving surface of No. 3 appears as a virtual image of the reflecting mirror 2 at a point where the normal line 13 and the optical path 15 are extended. Therefore, the reflector 2
When the arm 4 to which the PD 3 is attached is rotated, the light emitted from the LD 1 in each direction is selectively reflected at the position of the reflecting mirror 2 and reaches the light receiving surface of the PD 3. The optical path length from LD1 to PD3 is the sum of the normal line 13 and the optical path 15, and a small arm 4 can be used for the required optical path length 15. Furthermore, since only the reflector 2 is attached to the arm 4, the arm 4 can be rotated or stopped with high precision and high speed. In principle, the optical path length 15 can be set regardless of the length of the arm 4 as long as it is twice or more the length of the arm 4. Therefore, it is possible to easily realize an apparatus for measuring radiation characteristics of the LD 1 in which the optical path length 15 is set to be long.

In FIG. 2, the arm 4 is made perpendicular to the extension line 11, and the radiation characteristics on a plane including the normal line 13 passing through the center 1A of the light emitting surface of the LD 1 are measured. The light emitted from the LD 1 in the normal direction 13 is reflected by the reflecting mirror 2 in the direction of the center 3A of the PD 3 and reaches the light receiving surface of the PD 3. At this time, the optical path is point 1
A-point 2A-point 3A, and the length is constant regardless of the angle of the arm 4 (that is, the position of the reflecting mirror 2).

Next, the line between point 1A and point 2A is P, point 2
The line between A and point 3A is Q, and the line between point 1A and point 3A is R.
It will be explained that when P+Q=constant. Line P
Since the length is the length of the arm 4 from the rotating shaft 5 to the reflecting mirror 2, it remains constant unless the arm 4 is deformed. Line R is always constant unless the position of PD3 changes. Since the arm 4 rotates on a plane perpendicular to the rotation axis 5, the lines P and R are perpendicular and always constant. Since the two sides and their narrow angles are constant, triangle PQR always remains congruent regardless of the angle of arm 4. Therefore, P+Q=constant. Like this LD
Since the optical path length from PD1 to PD3 is always constant, there is no need for correction, and the light intensity measured by PD3 can be directly used as the radiation characteristic value of LD1.

Next, the relationship between the rotation angle of the arm 4 and the light intensity of the LD 1 will be explained. When the normal line 13 is parallel to a straight line that is orthogonal to the extension line 11 and passes through the reflection point 2A of the reflecting mirror 2, the angle of the arm 4 is 0°, passes through the center point 1A of the LD 1, and is orthogonal to the rotation axis 5. It is on a plane, and the direction of normal line 13 is LD
Let the angle of light emitted from 1 be 0°. When viewed from the PD3 side, the clockwise direction is the positive direction of the angle. Arm 4 is shown in Figure 3.
At the angle θa, only the light emitted from the LD1 at an angle θh=θa is reflected by the reflecting mirror 2 and reaches the PD3. When the arm 4 is fixed at each angle, the light intensity received by the PD 3 becomes the radiation characteristic value of the LD 1.

[0013]

Effects of the Invention According to the present invention, a PD is placed on an extension of a rotating shaft, a reflecting mirror is attached to an arm on which the rotating shaft rotates, the output light of the LD is reflected by the reflecting mirror, and the reflected light of the reflecting mirror is Since the light is received by the PD, it is possible to obtain an LD radiation characteristic measuring device with high measurement position (angle) accuracy even when the optical path length is increased.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a laser diode radiation characteristic measuring device according to the present invention.

FIG. 2 is a front view of FIG. 1.

FIG. 3 is a side view of FIG. 1;

FIG. 4 is a configuration diagram of a laser diode radiation characteristic measuring device according to the prior art.

[Explanation of symbols]

1 LD (laser diode) 1A　Center point of the light emitting surface of LD1 2 Reflector 2A Reflection point of reflecting mirror 2 3 PD (light receiving element) 3A Center point of PD3 light receiving surface 4 Arm 5 Rotation axis of arm 4 6 Drive device 7 Reference angle sensor 11 Extension line of rotating shaft 5 12 Normal line passing through center 3A of PD3 13 Normal line passing through center 1A of LD1 14 Normal line 15 Optical path passing through the center 2A of the reflecting mirror 2

Claims (1)

[Claims] [Claim 1] A reflector (2) that reflects the light emitted from the laser diode (1) is attached to the arm (4), and the arm (4) is rotated about the rotation axis (5) to reflect the light emitted by the laser diode (1). The reflected light is received by the light receiving element (3), and the extension line (11) of the rotation axis (5) is aligned with the first normal line (12) passing through the center point (3A) of the light receiving surface of the light receiving element (3). Center of the light emitting surface (1A) of the laser diode (1)
The extension line of the second normal (13) passing through and the axis of rotation (5) (
11) are orthogonal to each other, and the arm (4) is orthogonal to the second normal (13
), and the second normal (13) is the reflector (2).
is reflected at the reflection point (2A), and the third normal (14) passing through the reflection point (2A) intersects the first normal (12) to form the point (
3A) - point (2A) - point (1A) is 2
A radiation characteristic measuring device for a laser diode, which is characterized by dividing the laser diode into equal parts.