JP4061009B2 - Semiconductor laser characteristic measurement device - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a characteristic measuring apparatus for a semiconductor laser that receives light emitted from a semiconductor laser or a semiconductor laser unit in which the semiconductor laser and an adjustment lens are integrated.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an apparatus for measuring a semiconductor laser, an apparatus for measuring a current-light output characteristic which is a basic characteristic thereof is commercially available. In this type of measuring apparatus, a device that measures the intensity of emitted light by receiving light emitted from the semiconductor laser with a light receiving element while changing the current applied to the semiconductor laser fixed to the measuring head is well known. In general, a light receiving element that has been retracted at the time of non-measurement with respect to a measurement head for fixing a semiconductor laser is moved directly above the semiconductor laser at the time of measurement.
[0003]
On the other hand, semiconductor lasers are also used in light sources used in scanning optical systems and the like that are widely known for various image forming apparatuses such as laser printers and digital copying machines. In general, a so-called semiconductor laser unit in which a semiconductor laser is integrated with an adjustment lens, an aperture, or the like is used for this type of light source. The light emitted from the semiconductor laser is made parallel or slightly divergent or slightly convergent by a coupling lens and shaped by an aperture. Here, the ratio between the amount of light emitted from the semiconductor laser alone and the amount of light emitted from the aperture of the semiconductor laser unit is called coupling efficiency, which is one of the basic characteristics to be evaluated in a system light source such as a scanning optical system. In order to perform accurate evaluation, it is desirable that the measurement of the single semiconductor laser and the measurement of the semiconductor laser unit be performed under the same conditions.
[0004]
[Problems to be solved by the invention]
However, in the conventional measuring apparatus for measuring the current-optical output characteristics of the semiconductor laser, the measurement object is limited to a single semiconductor laser. That is, in the conventional measuring apparatus, the light receiving element can be close to the position of the emission light of the semiconductor laser, but in this case, there is no function to adjust to the position of emission from the aperture of the semiconductor laser unit having a different height. The amount of light emitted from the semiconductor laser unit could not be measured under the same conditions as in the case of a single laser.
[0005]
Therefore, the present invention has been made in view of the current situation as described above, and the object of the present invention is to be able to measure a measurement object having different emission positions, such as a semiconductor laser and a semiconductor laser unit, with the same measurement device. Another object of the present invention is to provide a semiconductor laser characteristic measuring apparatus capable of measuring light emitted from a semiconductor laser and a semiconductor laser unit under the same conditions, and particularly capable of measuring current-light output characteristics and coupling efficiency with high accuracy.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a semiconductor laser characteristic measuring device of the present invention is a device for measuring a characteristic of a semiconductor laser by receiving a light emitted from the measuring target as a single semiconductor laser or a semiconductor laser unit. A measuring head to which the measuring object can be attached; a light receiving element for receiving the emitted light from the measuring object attached to the measuring head; and a direction in which the light receiving element intersects the optical axis of the emitted light. A light receiving stage means for moving back and forth to a measurement position on the optical axis; and an optical axis direction displacing means for changing a relative positional relationship between the measurement object and the light receiving element at least in the optical axis direction. The stage means includes a plurality of light receiving elements, and is characterized in that each light receiving element is held so as to freely advance and retract to different positions in the optical axis direction.
2. The semiconductor laser characteristic measuring apparatus according to claim 1, wherein the light receiving stage means or the optical axis direction displacing means is in the direction perpendicular to both the advancing / retreating direction of the light receiving element and the optical axis direction. The positional relationship between the object and the light receiving element is variable.
3. The semiconductor laser characteristic measuring apparatus according to claim 1, wherein the light receiving stage means includes interference preventing means for detecting whether there is an obstacle in the advancing / retreating direction of the light receiving element. And
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a semiconductor laser characteristic measuring apparatus to which the present invention is applied will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a configuration of a first embodiment of a measuring apparatus according to the present invention. In these drawings, reference numeral 1 denotes a measuring head to which a measuring object is attached, 2 denotes a light receiving element such as a SiPIN photodiode, 3 denotes a light receiving stage as light receiving stage means, 4 denotes a single semiconductor laser as a measuring object, and 5 denotes a semiconductor laser. 4 is a semiconductor laser unit as a measuring object including 4, and 8 is an optical axis direction displacement means. The semiconductor laser unit 5 is obtained by integrating a coupling lens and an aperture with a single semiconductor laser 4. FIG. 1A shows the measurement of the single semiconductor laser 4, and FIG. 1B shows the measurement of the semiconductor laser unit 5.
[0011]
Further, as shown in FIG. 2, a drive power supply 7 and a light receiving element 2 for applying current / voltage to a measurement target such as the semiconductor laser 4 are connected to the control calculation means 6. In addition to injecting charges into the semiconductor to be measured via the power source 7, the light intensity output from the light receiving element 2 is captured, and various arithmetic processes and drive control of each driving means (for example, the light receiving stage 3) are performed. It is like that.
[0012]
The light receiving stage 3 is composed of a holding unit 3a installed on a surface plate (not shown) so as to hold a certain positional relationship with the measurement head 1 side, and an arm 3b held by the holding unit 3a. The light receiving element 2 is fixed to the tip in a direction facing the measurement target. The arm 3b can move forward and backward in the direction Y perpendicular to the optical axis from the holding portion 3a, and at the time of measurement, by increasing the protruding amount of the arm 3b, a light receiving element is placed on the laser optical axis of the emitted light on the measurement target. When 2 is arranged and measurement is not performed, the light projecting element 2 can be retracted from the optical axis by reducing the protruding amount of the arm 3b.
[0013]
A single semiconductor laser 4 or a semiconductor laser unit 5 can be installed on the measurement head 1 as the measurement object, and the optical axis direction of each emitted light is aligned regardless of which one is installed. In the first embodiment shown in FIG. 1, the measuring head 1 can be divided into upper and lower units 1a and 2a. It is movable in the Z direction along the axial direction. Thus, in the first embodiment, the measuring head 1 is provided with the “optical axis direction displacement means 8”.
[0014]
The measurement procedure by the measuring apparatus having the above configuration is as follows. Since light emitted from the semiconductor laser 4 is divergent light, the light receiving element 2 needs to be positioned in the vicinity of the semiconductor laser 4 in order for the light receiving element 2 to capture all the light. For this reason, when the semiconductor laser 4 is measured alone, the light receiving element 2 is moved to a position just above the semiconductor laser 4 fixed on the measuring head 1 to receive light as shown in FIG. Subsequently, when a semiconductor laser unit 5 larger than this is fixed instead of the semiconductor laser 4, the light receiving element 2 and the semiconductor laser unit 5 interfere with each other in the positional relationship of FIG. Therefore, as shown in FIG. 1B, the optical axis direction displacement means 8 of the measuring head 1 is driven to lower the upper unit 1a in the Z direction. At this time, even if the semiconductor laser unit 5 is fixed, the upper unit 1a is lowered to a position where the light receiving element 2 does not interfere with it. From the viewpoint of measurement under the same conditions, the aperture of the semiconductor laser unit 5, that is, the emission position is set to the semiconductor laser. It is desirable to set the displacement amount of the upper unit 1a so as to be equal to the emission position relationship in the case of a single unit. Then, the semiconductor laser unit 5 is fixed to the upper unit 1a lowered to a predetermined position, and the emitted light from the semiconductor laser unit 5 is received. The light receiving stage 3 and the optical axis direction displacement means 8 may be driven and controlled by the control calculation means 6 using a stepping motor or the like, or may be manually operated.
[0015]
FIG. 3 is a diagram showing current-light output characteristics measured by the measuring apparatus. Here, the ratio of the emitted light amount L2 from the aperture of the semiconductor laser unit 5 to the emitted light amount L1 from the semiconductor laser 4 alone, that is, L2 / L1, is called coupling efficiency, and is one of the important basic characteristics to be obtained in this measurement. One. In this measurement result, the light receiving process is performed under the same conditions in which a certain positional relationship is formed between the light receiving element 2 and the emission position of each measurement object as described above. Accurate characteristics such as L2 / L1 can be calculated.
[0016]
FIG. 4 is a perspective view showing a second embodiment of the present invention. FIG. 4A shows the measurement of the single semiconductor laser 4 and FIG. 4B shows the measurement of the semiconductor laser unit 5. In the second embodiment, the optical axis direction displacing means 8 is provided not on the measuring head 1 but on the light receiving stage 3 side. By driving the optical axis direction displacement means 8, the holding portion 3a of the light receiving stage 3 holding the light receiving element 2 is displaced in the Z direction. As a result, the advance / retreat position of the arm 3 b rises in the optical axis direction, and the light receiving element 2 can be disposed at the emission position of the semiconductor laser unit 5. As described above, the optical axis direction displacing means 8 is not limited to the measurement head 1 and may be provided on the light receiving stage 3. It is only necessary to adjust the positional relationship.
[0017]
FIG. 5 is a perspective view showing the configuration of the third embodiment of the present invention. In the third embodiment, the optical axis direction displacement means 8 is not provided, but the light receiving stage 3 is provided with a plurality of arms 3 a and the light receiving element 2. The light receiving elements 2, 2 of the arms 3b, 3b are separated by a predetermined distance in the optical axis direction, and correspond to a plurality of different measurement positions in the optical axis direction, that is, the heights of the emission positions of the measurement objects. From the light receiving stage 3, one arm 3b at a height required for the measurement object is moved in the Y direction, and one light receiving element 2 is selectively placed on the optical axis. In the illustrated example, the lower light receiving element 2 is used for measuring a single semiconductor laser 4, and the upper light receiving element 2 is used for measuring a semiconductor laser unit 5.
[0018]
FIG. 6 is a perspective view showing a fourth embodiment of the present invention. In the fourth embodiment, the light receiving stage 3 is installed on an X direction stage (not shown). The X direction is a direction perpendicular to the Y direction and the Z direction, and the light receiving element 2 can be displaced in the X direction together with the light receiving stage 3 by driving the X direction stage. Such a configuration corresponds to different optical axis positions, such as when the semiconductor laser unit 5 is a multi-beam and the optical axis is bent by a prism or the like. For example, as shown in FIG. 6, the light receiving element 2 is displaced in the X direction with respect to a plurality of optical axis directions of one measurement object, and moved on the respective optical axes to capture the entire emitted light. Measurement is possible. Further, in the case of being displaceable in three orthogonal directions (X, Y, Z) as in the present embodiment, the arrangement of the light receiving elements 2 in space is advantageous because of their combined movement. It is a form. The X-direction stage may be one that displaces the measuring head 1 side.
[0019]
FIG. 7 is a perspective view showing a fifth embodiment of the present invention. In this fifth embodiment, a position detector 9 is attached as an interference preventing means on the opposite end of the arm 3b, for example, as shown in FIG. As indicated by the chain line in FIG. 7, the position detector 9 obstructs the forward / backward direction of the light receiving element 2, that is, when the arm 3b is extended, on the tip of the arm 3b and the optical axis that the light receiving element 2 reaches. Light detection is performed to determine whether an object exists. The position detector 9 can be a photo sensor that combines a light projecting unit and a light receiving unit. Such a position detector 9 is connected to the control calculation means 6 so that a signal from the position detector 9 is used for controlling the light receiving stage 3, the optical axis direction displacement means 8, and the like. Further, when an obstacle is detected, a warning may be issued via the control calculation means 6.
[0020]
The operation of the fifth embodiment is as follows. After measuring the semiconductor laser 4, the light receiving element 2 is temporarily retracted from the optical axis by moving in the Y direction from the height corresponding to the semiconductor laser 4. Next, the semiconductor laser unit 5 is installed on the measuring head 1 and measurement is performed. When the light receiving element 2 is moved again on the optical axis without driving the optical axis direction displacement means 8, the semiconductor laser unit 5 There is a risk of damaging the measuring device and the semiconductor laser unit 5 due to interference.
[0021]
Therefore, the position detector 9 always detects whether or not there is an obstructing object at the movement destination of the light receiving element 2, and stops the movement of the light receiving element 2 in the Y direction. Further, even when the light receiving element 2 moves in the Z direction or the X direction, when an obstacle such as the semiconductor laser unit 5 is detected in the moving range, the movement is similarly stopped. Furthermore, in this example, the signal obtained from the position detector 9 can be fed back to the drive control of the optical axis direction displacement means 8 so that the light receiving element 2 can be reliably moved to a position where it does not interfere with the measurement object. As described above, the provision of the position detector 9 not only prevents a collision with the semiconductor laser unit 5 which is a large unit, but also provides a constant distance from each measurement target so as to match each outgoing light position. It is also possible to automatically control the position of the light receiving element 2 such that the light receiving element 2 is arranged at a position above the distance.
[0022]
【The invention's effect】
As is apparent from the above description, the semiconductor laser characteristic measuring apparatus according to the present invention includes an optical axis direction displacement unit that varies at least the relative positional relationship between the measurement target and the light receiving element in the optical axis direction. Because of the configuration, measurement objects with different emission positions such as semiconductor laser and semiconductor laser unit can be measured with the same measuring device, and the emitted light from the semiconductor laser and semiconductor laser unit can be measured under the same conditions. -It is possible to provide a semiconductor laser characteristic measuring apparatus capable of measuring optical output characteristics and coupling efficiency with high accuracy.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of a first embodiment of a measuring apparatus according to the present invention, in which FIG. 1 (a) shows a measurement with a semiconductor laser alone, and FIG. 1 (b) shows a measurement with a semiconductor laser unit. FIG.
FIG. 2 is a block diagram showing a control configuration of a measuring apparatus according to the present invention.
FIG. 3 is a diagram showing current-light output characteristics measured by a measuring apparatus according to the present invention.
FIGS. 4A and 4B are perspective views showing a second embodiment of the present invention, in which FIG. 4A is a diagram showing a measurement with a single semiconductor laser, and FIG. 4B is a diagram showing a measurement with a semiconductor laser unit.
FIG. 5 is a perspective view showing a configuration of a third embodiment of the present invention.
FIG. 6 is a perspective view showing a configuration of a fourth embodiment of the present invention.
FIG. 7 is a perspective view showing a configuration of a fifth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Measuring head 2 Light receiving element 3 Light receiving stage 4 Semiconductor laser 5 Semiconductor laser unit 8 Optical axis direction displacement means 9 Position detector 9 (interference prevention means)
Y Advancing and retracting direction of light receiving element X A direction perpendicular to both the advancing and retracting direction of the light receiving element and the optical axis

Claims (3)

An apparatus for measuring a characteristic of a semiconductor laser by taking a semiconductor laser unit or a semiconductor laser unit as a measurement target and receiving light emitted from the measurement target,
A measurement head to which the measurement object can be attached;
A light receiving element for receiving emitted light from the measurement object attached to the measurement head;
A light receiving stage means for moving the light receiving element forward and backward from a direction intersecting the optical axis of the emitted light to a measurement position on the optical axis;
An optical axis direction displacing means for varying a relative positional relationship between at least the measurement object in the optical axis direction and the light receiving element,
The above-mentioned light receiving stage means comprises a plurality of light receiving elements, and holds each light receiving element so as to freely advance and retreat to different positions in the optical axis direction. The light receiving stage means or the optical axis direction displacement means is characterized in that the positional relationship between the measurement object and the light receiving element is variable in a direction perpendicular to both the advancing / retreating direction of the light receiving element and the optical axis direction. The semiconductor laser characteristic measuring apparatus according to claim 1 . 3. The semiconductor laser characteristic measuring apparatus according to claim 1 , wherein the light receiving stage means includes interference preventing means for detecting whether or not there is an obstacle in the advancing / retreating direction of the light receiving element.

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