JPH0334129A - Lens displacement measuring instrument - Google Patents

Abstract

PURPOSE:To always keep an optical axis from a light source to a photoelectric detector constant, to detect the displaced state of a convergence lens, and to make a lens holder light weight by providing the light source, the lens, a half mirror, and the photoelectric detector outside the lens holder. CONSTITUTION:Light irradiating from the light source 5 is formed as parallel beams with the lens 7, and is deflected by 90 deg. with the half mirror 4, and passes a transmission optical path 3, and is received with the photoelectric detector 6. At this time, when the lens holder 1 is displaced in a direction of X or Y, or the synthesized direction of X and Y, the optical path 3 is deviated against the optical axis from the center of the half mirror 4 to that of the photoelectric detector 6, then, the light receiving state of the detector 6 is changed. A displacement quantity in the direction of Y is detected with the output of a comparator 13, and that in the direction of X with that of a comparator 14, respectively. The optical axis from the light source 5 to the detector 6 can be always kept constant, thereby, the displaced state of the convergence lens 2 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for measuring lens displacement of a pickup in an optical disk drive.

Conventional technology In optical disk drives, it is necessary to accurately position the condenser lens facing the recording medium in the focusing direction and the tracking direction, and for this purpose, the amount of displacement of the optical axis of the condenser lens is detected. There are various detection devices.For example, as described in Japanese Patent Application Laid-Open No. 105905/1982, a part of the laser beam is focused by a parabolic reflecting mirror portion of an aperture lens, and this focused light is There is an invention in which surface runout and center runout are measured by detecting the detected light using a difference signal of a four-split light receiving sensor. In addition, as described in Japanese Utility Model Application Publication No. 62-76608, the light passing through the window of the light shielding plate can be
There is an idea to measure the eccentricity and deflection of the condenser lens by detecting it with a split light receiving sensor. moreover,
As described in Japanese Utility Model Application Publication No. 62-98023, a spectroscope is used to irradiate a part of the laser beam onto a light shielding plate, and the light passing through the light shielding plate is detected by a four-split light receiving sensor. Therefore, there is an idea to measure the amount of displacement of a condensing lens. Furthermore, as described in Japanese Utility Model Application Publication No. 63-159709, a light beam from a light source is irradiated onto a mirror placed on the outer periphery of a lens barrel holding a condensing lens, and the reflected light from this mirror is There is an idea to measure the amount of displacement of the condenser lens by receiving the light with a four-part light receiving sensor.

Furthermore, as described in Japanese Utility Model Application No. 63-159712, four
There is an idea to provide a divided light receiving sensor and to measure the displacement amount of a condenser lens by irradiating a rectangular spot light onto the four divided light receiving sensor.

Problems to be Solved by the Invention The invention or idea described in the above publication includes a light path member such as a light shielding plate or a mirror that guides light from a light source to a four-split light receiving sensor;
Alternatively, since the four-split light receiving sensor is attached to the support member that holds the condenser lens, the weight of the support member increases due to the increase in the number of attached parts. Therefore, it is necessary to increase the driving force for moving the support member in the tracking direction and the focusing direction, and there are also problems such as increased vibration of the support member.

Means for Solving the Problems A lens support holding a condensing lens facing a recording medium is connected to a drive unit and provided movably in a tracking direction and a focusing direction, and a A light source that forms a transmitted optical path orthogonal to the focusing direction and irradiates one end of the transmitted optical path with a beam having a diameter larger than the cross-sectional area of both ends of the transmitted optical path, and faces the other end of the transmitted optical path. A photoelectric detector was provided outside the lens support.

Since the optical axis from the working light source to the photoelectric detector is always constant,
When the lens support is displaced, the transmitted optical path is displaced with respect to the optical axis from the light source to the photoelectric detector, and as a result, the state of reception of light from the light source by the photoelectric detector changes, resulting in displacement of the condensing lens. In addition, it is only necessary to provide a photoelectric detector and a light source outside the lens support, and form only a transmitted optical path in the lens support holding the condensing lens. It is possible to reduce the weight of the support.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 6. Reference numeral 1 denotes a lens support body, and this lens support body l is connected to a driving section (not shown) and driven in a focusing direction Y and a tracking direction X. Further, this lens support 1 holds a condenser lens 2 that faces an optical disk (not shown) as a recording medium. Furthermore, a transmission optical path 3 with openings at both ends perpendicular to the Y direction and the X direction is formed in this lens support l. A light source 5 irradiates one end of the transmitted optical path 3 with a light beam via a half mirror 4, and a photoelectric detector 6 facing the other end of the transmitted optical path 3.
are fixedly provided outside the lens support l. The light beam from the light source 5 is collimated by the lens 7, and the diameter of the beam of this light beam is set to be larger than the cross-sectional area of both ends of the transmitted optical path 3. Furthermore, the half mirror
A light receiving element 8 is fixed to the end of the light receiving element 4 for detecting the light beam traveling straight from the light source 5 and compensating the amount of light from the light source 5 to a constant value. Furthermore, the photoelectric detector 6 is a CC
Although a D sensor may be used, in this embodiment, a 4-split light receiving sensor having four light receiving elements A, B, C, and D is used. As shown in FIG. 4, these light receiving elements A, B, and C.

D are connected to amplifiers 9, 10, 11.12, respectively. Also, if the outputs of light receiving elements A, B, C, and D are respectively A', B', C', and D', then A' +
A comparator 13 that compares B' and C' + D';
A comparator 14 is provided to compare '+C' and B'+D'.

In such a configuration, the light emitted from the light source 5 is collimated by the lens 7, and is parallelized by the half mirror 4 at 90 degrees.
This deflected light passes through the transmission optical path 3 and is received by the photoelectric detector 6.

At this time, if the lens support 1 is displaced in the X direction, Y direction, or their combined direction, the transmitted optical path 3 is shifted from the optical axis from the center of the half mirror 4 to the center of the photoelectric detector 6, so the photoelectric The light receiving state of the detector 6 changes. Figure 2 (a
) is a normal state in which light is irradiated to the center of the photoelectric detector 6, and the center of the irradiated light is at point a in FIG. 3.

The state shown in FIG. 2(b) is a state in which light is irradiated upward (in the Y direction) from the center of the photoelectric detector 6, and the center of the irradiated light is at point b in FIG. 3.

The state shown in FIG. 2(c) is a state in which light is irradiated from the center of the photoelectric detector 6 to the left (in the X direction), and the center of the irradiated light is at point C in FIG.

The state shown in FIG. 2(d) is a state in which light is irradiated from the center of the photoelectric detector 6 toward the upper left (Y and X directions).
The center of the irradiated light is point d in FIG. 3. At this time, the amount of displacement in the Y direction is detected by the output of the comparator 13, and the amount of displacement in the X direction is detected by the output of the comparator 14.

Furthermore, FIG. 5(a) shows a normal state in which the optical axis of the condenser lens 2 coincides with the Y-axis which is the focusing direction, and although the amount of incident light and the amount of outgoing light of the transmitted optical path 3 are exclusive, FIG. b)
As shown in the figure, the condenser lens 2 is tilted by the lens support l.
When the optical axis of is tilted, the amount of emitted light decreases relative to the amount of light incident on the transmitted optical path 3. That is, the amount of light received by the photoelectric detector 6 decreases. The change in the amount of light received by the photoelectric detector 6 and the change in the inclination angle of the lens support 1 are inversely proportional to each other, as shown in FIG.
The angle of inclination increases. At this time, the light receiving elements A, B, C,
Since the output of D changes, the amount of decrease and the direction of inclination can also be known.

As described above, the light source 5, the lens 7, the half mirror 4, and the photoelectric detector 6 are provided outside the lens support 1, and only the transmitted optical path 3 is formed in the lens support l holding the condenser lens 2. This makes it possible to reduce the weight of the lens support 1, which allows the lens support 1 to be driven with a small driving force.
It is also possible to reduce vibrations.

Note that by directing the light source 5 to one end of the transmitted optical path 3,
The half mirror 8 may be omitted, and as shown in FIG. In this case, it is desirable to lower the reflectance of the inner peripheral surface 17. Furthermore, as shown in FIG. 8, light receiving elements 15 and 16 may be arranged above and below the photoelectric detector 6. .

As a result, the normal state shown in FIG.
When the lens support 1 is tilted as shown in Figure (b), the amount of light received by the photoelectric detector 6 decreases as described above. Since it is brighter than the surrounding area, the inclination direction of the lens support l can also be determined from the difference in output between the light receiving elements 15 and 16. When the lens support 1 is tilted in the opposite direction, the output of the light receiving element 15 is greater than that of the light receiving element 16, and the tilting direction is recognized.

Effects of the Invention Since the present invention is configured as described above, the optical axis from the light source to the photoelectric detector is always constant, so when the lens support is displaced, the transmitted optical path changes from the light source to the photoelectric detector. Since the light receiving state of the light source by the photoelectric detector changes accordingly, it is possible to detect the displacement state of the condensing lens. It is necessary to form only a transmission optical path in the lens support which is provided externally to the lens support and holds the condensing lens.This makes it possible to reduce the weight of the lens support and, therefore, to move the lens support with a small driving force. Furthermore, it has the advantage of being able to reduce vibrations of the lens support.

[Brief explanation of drawings]

1 to 6 show an embodiment of the present invention,
Figure 1 is a perspective view, Figure 2 is a front view showing changes in the light receiving state of the photoelectric detector, Figure 3 is an explanatory diagram showing the light receiving point of the photoelectric detector with coordinates, and fjS4 diagram is an electronic diagram including the photoelectric detector. The circuit diagram, Fig. 5 is a longitudinal side view showing the state in which the amount of displacement in the inclination direction of the lens support is detected, and Fig. 6 shows the relationship between the change in the inclination angle of the lens support and the change in the amount of light received by the photoelectric detector. 7 is a longitudinal sectional side view of the lens support showing a modified example of the transmitted optical path, and FIG. 8 is a longitudinal sectional side view showing a modified example of the means for detecting the displacement of the lens support in the inclination direction. .

Claims (1)

[Claims] A lens support holding a condensing lens facing the recording medium is connected to a drive unit so as to be movable in a tracking direction and a focusing direction, and the lens support is provided in a direction perpendicular to the tracking direction and the focusing direction. A light source that forms a transmitted optical path and irradiates one end of the transmitted optical path with a beam having a diameter larger than the cross-sectional area of both ends of the transmitted optical path, and a photoelectric detector that faces the other end of the transmitted optical path, is connected to the lens. A lens displacement measuring device characterized in that it is provided outside a support.