JP2006134957A - Manufacturing method of optical instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of optical instruments capable of precisely detecting inclination of the emission pattern of a semiconductor laser element with no use of a complicated algorithm, when adjusting angular position of a semiconductor laser in a manufacturing process of optical instruments. <P>SOLUTION: The end face of a semiconductor laser element 20 is made to illuminate linearly in natural emission mode by driving the semiconductor laser element 20 at the current less than oscillation threshold value, in an angular position detecting process of the semiconductor laser element 20 when manufacturing optical instruments such as an optical head device. Based on the observation result of the linear illumination pattern, the angular position around the optical axis of the semiconductor laser element 20 is detected. Here, the linear illumination pattern may be image-processed to acquire a linear approximation pattern of the illumination pattern, to detect the angular position around the optical axis of the semiconductor laser element 20 based on the linear approximation pattern. The detection result can be used for adjusting angular position or the like of the semiconductor laser element 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical apparatus provided with a semiconductor laser element. More specifically, the present invention relates to a technique for supplying power to a semiconductor laser to emit light and detecting an angular position around the optical axis of the semiconductor laser element based on the light emission pattern.

  As shown in FIG. 2A, the semiconductor laser device has a rectangular cross-sectional shape of the optical resonator formed of a waveguide, the dimension of the long side 21 (direction parallel to the horizontal plane of the semiconductor laser chip), and the short side 22. In general, dimensions in a direction perpendicular to the horizontal plane of the semiconductor laser chip are different by one digit or more. Here, the dimension of the short side 22 is the thickness of the active layer, which is determined by the layer thickness of the heterojunction compound semiconductor layer such as a multiple quantum well structure formed by epitaxial crystal growth, and is on the order of a so-called sub-μm order of about 100 nm. Dimensions. On the other hand, the dimension of the long side 21 is determined by the width of a rigid stripe formed by a semiconductor process such as etching for current confinement, and is a dimension on the order of several μm.

  In such a semiconductor laser element 20, the above-mentioned waveguide cross section at the emission end face formed of a cleavage plane becomes an opening 25 that determines the shape of the emission spot of the semiconductor laser element 20. Here, the light passing through the opening 25 propagates with a spread (radiation angle) due to diffraction, and the radiation angle (diffraction angle) increases as the size of the opening 25 decreases, and decreases as the size of the opening 25 increases. Therefore, the laser beam L emitted forward from the horizontally long rectangular opening 25 has a longer vertical radiation angle than a horizontal radiation angle, and the far field pattern has a vertically long elliptical shape. The same applies to laser light emitted backward.

  As a typical optical apparatus provided with such a semiconductor laser element 20, there is an optical head device for reproducing CDs and DVDs. In this optical head device, an image is formed on an optical recording disk by an objective lens. The spot shape is a real image of the opening 25 on the emission end face of the semiconductor laser element 20. Here, the spot shape is ideally a horizontally long rectangular shape, but in reality, from the ideal state of leakage of light from the waveguide inside the semiconductor laser element 20 or Fourier transform by the optical system. Due to such a shift, a horizontally long elliptical shape is formed. Therefore, the shape of the light spot that is collected on the optical recording disk and reads the recording signal is an ellipse, not a perfect circle. For this reason, the reproducing / recording characteristics of the optical head device differ depending on the inclination of the spot with respect to the signal track (the direction of the ellipse). Therefore, in the manufacturing process of the optical head device, the direction of the elliptical spot is as designed. Assembling is performed while adjusting the angular position by rotating the semiconductor laser element 20 around the optical axis. In addition, inspection sorting is performed according to the direction of the elliptical spot.

  Conventionally, when adjusting or inspecting the direction of an elliptical spot, the semiconductor laser element 20 is oscillated to emit laser light L, and a far field pattern or a light spot image on the disk surface (near field However, since such a pattern is elliptical and has various power distributions, it is difficult to accurately detect the angular position around the optical axis of the semiconductor laser element 20. .

  That is, when the semiconductor laser element 20 is driven with a current equal to or higher than the oscillation threshold value to cause laser oscillation, the stimulated emission light energy is concentrated in the active region. When this is observed with an imaging device such as a CCD, FIG. As shown in FIG. 4, an elliptical light emission spot (near field pattern) should be recognized, but since the luminance is extremely high, it is monitored as shown in FIG. 4. Therefore, it is difficult to accurately determine the orientation of the ellipse even when visually confirming the orientation of the ellipse. Also, since such patterns have various power distributions, a complicated algorithm is required to detect the orientation of the elliptic pattern (angle position around the optical axis of the semiconductor laser element) by image processing, and It is difficult to improve measurement accuracy. When the semiconductor laser element 20 is driven with a current equal to or higher than the oscillation threshold value to cause laser oscillation, the active region (actuated emission light) and the active region (actuated emission light) as shown in FIG. There is also a spontaneously emitted light component that shines in a linear shape by leaching up to the active layer on both sides centering on the laser oscillation region), and based on this, the direction of the emission pattern may be detected. Since the component has an order of magnitude lower intensity than the laser light component, it is impossible to observe the spontaneous emission light component from the viewpoint of the dynamic lens of the image sensor.

  In view of the above problems, an object of the present invention is to accurately adjust the inclination of the light emission pattern of a semiconductor laser element without using a complicated algorithm when adjusting the angular position of the semiconductor laser in the manufacturing process of an optical device. An object of the present invention is to provide a method of manufacturing an optical device that can be detected well.

  In order to solve the above problems, in the method for manufacturing an optical apparatus of the present invention, the semiconductor laser element is driven with a current less than an oscillation threshold value, and the end surface of the semiconductor laser element is emitted linearly in a spontaneous emission mode, An angular position detecting step of detecting an angular position around the optical axis of the semiconductor laser element based on the observation result of the linear light emission pattern is provided.

  In the present invention, in the angular position detection step of detecting the angular position around the optical axis of the semiconductor laser element, the semiconductor laser element is driven with a current less than the oscillation threshold value, so that the end face of the semiconductor laser element is in a spontaneous emission mode. Light is emitted linearly. For this reason, when detecting the angular position of the semiconductor laser element, the light emission pattern on the end face of the semiconductor laser element is linear as shown in FIG. 3, so that the inclination of the light emission pattern can be obtained without using a complicated algorithm. That is, the tilt of the semiconductor laser element can be detected easily and accurately.

  In the present invention, when detecting the inclination of the semiconductor laser element based on the inclination of the light emission pattern, the light emission pattern may be observed visually, or image processing may be used. That is, when observing a linear light emission pattern as shown in FIG. 3 in the angular position detection step, the linear light emission pattern is image-processed to obtain a linear approximation pattern of the light emission pattern, and the linear approximation pattern It is preferable to detect the angular position around the optical axis of the semiconductor laser element based on the above.

  In the present invention, it is preferable to adjust a relative angular position between the semiconductor laser element and another optical element based on a detection result of the angular position of the semiconductor laser element.

  In the present invention, in the angular position detection step of detecting the angular position around the optical axis of the semiconductor laser element, the semiconductor laser element is driven with a current less than the oscillation threshold value, so that the end face of the semiconductor laser element is in a spontaneous emission mode. Light is emitted linearly. For this reason, when detecting the angular position of the semiconductor laser element, since the light emission pattern at the end face of the semiconductor laser element is linear, the inclination of the light emission pattern, that is, the inclination of the semiconductor laser element has to be used without using a complicated algorithm. Can be easily and accurately detected.

  Embodiments of the present invention will be described with reference to the drawings.

(Description of optical system of optical head device)
FIGS. 1A and 1B are explanatory views showing an optical system of an optical head device (optical apparatus) to which the present invention is applied, and when this optical system is viewed from the front monitor light receiving element side. It is explanatory drawing. Since many of the optical elements can be seen well from below the base, FIG. 1A shows the optical system as viewed from the bottom. For this reason, in FIG. 1B, the objective lens is shown below the drawing, but since the optical head device is usually arranged below the optical recording medium, the optical system in the vertical direction of the optical system is shown. The position is actually upside down from the position shown in FIG.

  An optical head device 1 shown in FIGS. 1A and 1B is an optical head device that records and reproduces CDs, CD-Rs, and DVDs, and optical elements described below each have a base (not shown). ). The optical head device 1 shown here has a first laser diode 4 (semiconductor laser element) for DVD that emits a first laser beam having a wavelength of 650 nm or 635 nm (short wavelength) as a light source unit, and a wavelength of 760 to 800 nm. And a second laser diode 5 (semiconductor laser element) for CD that emits a second laser beam having a long wavelength.

  Further, the optical head device 1 combines the first laser beam emitted from the first laser diode 4 and the second laser beam emitted from the second laser diode 5 by another optical system. A prism 6 as an optical element is guided to a common optical path 10 toward the optical recording medium. On the common optical path 10, a rising mirror 11, a collimating lens 12, and an objective lens 13 are arranged in this order. ing. Further, in the optical head device 1 of this embodiment, in guiding the first laser light emitted from the first laser diode 4 and the second laser light emitted from the second laser diode 5 to the prism 6, On the optical path from the first laser diode 4 to the optical recording medium, the first laser light is partially reflected toward the prism 6 and the return light from the optical recording medium is partially transmitted to the light receiving element 9. A half mirror 7 is arranged as an optical element for returning light separation to be avoided. A grating lens 14 and a relay lens 15 are disposed on the optical path from the second laser diode 5 to the prism 6. Further, a sensor lens 17 as an astigmatism generating element is disposed between the half mirror 7 and the light receiving element 9. The sensor lens 17 is a lens for generating astigmatism with respect to the return light of the laser light. Further, a light receiving element 16 for front monitor is disposed on the opposite side of the prism 6 from the half mirror 7.

(Manufacturing method of optical head device)
2A, 2B, and 2C are respectively an explanatory diagram of laser light emitted from the semiconductor laser device and an explanatory diagram when the semiconductor laser device emits light in a spontaneous emission mode. FIG. 3 is an explanatory diagram when the end face of the semiconductor laser device is observed at a magnification of 1300 times when the semiconductor laser device emits light in the spontaneous emission mode.

  In the manufacturing process of the optical head device 1 of the present embodiment, the first laser diode 4 or the second laser diode 5 shown in FIGS. 1A and 1B (hereinafter referred to as a semiconductor laser element 20 without distinguishing them). ) Is turned on, and the far field pattern or the light spot image (near field pattern) on the disk surface is observed to detect the orientation of the elliptic pattern (the angular position around the optical axis of the semiconductor laser device). An angular position detection step is performed. Further, based on the result obtained in such a process, the relative position around the optical axis between the semiconductor laser element 20 and the other optical components is adjusted, and the quality of the optical head device 1 is determined.

  In performing this angular position detection step, in this embodiment, the semiconductor laser element 20 is driven with a current less than the oscillation threshold value, and the end surface of the semiconductor laser element 20 is naturally moved as shown in FIG. Light is emitted linearly in an emission mode (LED (Light Emitting Diode) mode), and the angular position around the optical axis of the semiconductor laser element is detected based on the observation result of the linear light emission pattern.

  That is, when the semiconductor laser device 20 is driven with a current less than the oscillation threshold, concentration of stimulated emission light energy in the active region and an elliptical light emission pattern as shown in FIGS. 2A and 2B are recognized. However, as shown in FIG. 2C, the end face of the semiconductor laser device 20 only emits light linearly in the spontaneous emission mode. Such a linear light emission pattern emits light to the active layers on both sides centering on the active region (laser oscillation region), and a part of the linear active layer itself emerges as LED light. . Therefore, if the sensitivity of an image pickup device such as a CCD is increased, a linear light emission pattern as shown in FIG. 3 can be observed. With such a light emission pattern, the inclination can be easily observed visually. Therefore, the tilt of the semiconductor laser element 20 can be detected easily and accurately.

  Also, with such a linear light emission pattern, the linear light emission pattern is subjected to image processing to obtain a linear approximate pattern of the light emission pattern, and based on this linear approximate pattern, the optical axis around the optical axis of the semiconductor laser device 20 is obtained. The angular position can be detected. At this time, since the light emission pattern is linear, a complicated algorithm is not required when performing image processing, and the measurement accuracy is high.

(Other embodiments)
In the above embodiment, the optical head device is described as an example of the optical device using the semiconductor laser element. However, the present invention may be applied to a laser printer, an inter-vehicle distance measuring device using laser light, and the like.

(A), (b) is each explanatory drawing which extracts and shows the optical system of the optical head apparatus with which this invention is applied, and explanatory drawing when this optical system is seen from the light receiving element side for front monitors. (A), (b), (c) is explanatory drawing of the laser beam radiate | emitted from a semiconductor laser element, respectively, and explanatory drawing when a semiconductor laser element is made to light-emit in spontaneous emission mode. It is explanatory drawing when the end surface of a semiconductor laser element when making a semiconductor laser element light-emit in spontaneous emission mode is expanded and observed 1300 times. It is explanatory drawing when the end surface of a semiconductor laser element when light-emitting a semiconductor laser element in a laser oscillation state is magnified 1300 times and observed.

Explanation of symbols

1 Optical head device 4, 5 Laser diode (semiconductor laser element)
20 Semiconductor laser device 25 Opening of semiconductor laser device

Claims (3)

  The semiconductor laser element is driven with a current less than the oscillation threshold value to cause the end face of the semiconductor laser element to emit light linearly in a spontaneous emission mode, and based on the observation result of the linear light emission pattern, An optical apparatus manufacturing method comprising an angular position detection step of detecting an angular position around an optical axis.   In Claim 1, in the said angle position detection process, when observing the said linear light emission pattern, the said linear light emission pattern is image-processed, the linear approximation pattern of the said light emission pattern is calculated | required, and based on the said linear approximation pattern And detecting an angular position around the optical axis of the semiconductor laser element.   3. The method of manufacturing an optical apparatus according to claim 1, wherein a relative angular position between the semiconductor laser element and another optical element is adjusted based on a detection result of the angular position of the semiconductor laser element. .

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