JPH0743108A - Optical displacement gauge - Google Patents

Abstract

PURPOSE:To maintain stability during a motion at high speed and acceleration by keeping the center of gravity of a whole moving section including a focusing lens, on the line of force of a drive system. CONSTITUTION:A moving section 40 has an approximately rectangular frame 41 and a focusing lens 20 is fixed to the lower end thereof. In addition, the section 40 is held, so as to be freely movable along a displacement measurement direction with a pair of parallel leaf springs 60, relative to a displacement gauge body 8. The center of gravity G of the whole of the section 40 is virtually positioned on the line of force WL of a drive system formed out of a drive coil 62 and a magnet 64 as a pair. According to this construction, an actuator when driven at high acceleration, is not dislocated due to moment around the center of gravity G of the moving section 40. The actuator can thus be controlled with high accuracy at the time of measuring a measurement object under displacement at high speed. Furthermore, the optical axis OA of the lens 20 is kept within a plane including the flexed section of the parallel leaf springs 60 at the side of the moving section 40, thereby enabling the dislocation of the lens 20 from the optical axis OA due to disturbances, to be kept approximately at zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement meter,
In particular, the present invention relates to an optical displacement meter that is suitable for use in the follow-up control of a pickup of a floppy disk driver and a movable head including a focusing lens, which is suitable for use in a measurement head of a surface roughness meter. Is.

[0002]

2. Description of the Related Art For example, the applicant of the present invention has a utility model of Japanese Utility Model Application No. 5-34512
As disclosed in 1), the laser light source 10 fixed to the displacement meter main body 8 and the light from the laser light source 10 are focused on the measurement target 12, for example, a polarization beam splitter 14,
A focusing optical system including the collimator lens 16 and the focusing lens 20 and reflected light from the measurement target 12 are used to detect a deviation from the reference distance between the focusing lens 20 and the measurement target 12, For example, a quarter wave plate 24, an imaging lens 2
6, a beam splitter 28, a detection optical system including the light receiving elements 32A and 32B, a focusing lens 20, a driving coil 46 (or a magnet 44), and a linear encoder 48.
A movable part 40 integrally attached with a scale 50 of
Based on the signal from the detection optical system, the movable portion 40,
2. Description of the Related Art There is known an optical displacement meter including a drive circuit that drives a focusing lens 20 and a measurement object 12 so that the distance between them becomes a reference distance.

Further, Japanese Patent Laid-Open No. 4-366711 and Japanese Patent Laid-Open No. 5-36611.
89480 discloses an optical axis of a focusing lens and a linear scale which are coaxially arranged so that an Abbe error does not occur.

[0004]

However, Japanese Patent Laid-Open No. 4-366711 emphasizes static accuracy, and in order to follow the high-speed movement of the measuring object, high-speed and high-acceleration of the movable part. It is necessary to consider stability during exercise.

When the actuator is moved at a high speed, if the line of action of the driving force (line of force) and the center of gravity of the movable portion are deviated, a moment around the center of gravity is generated, which makes control uncontrollable or unstable. It had a problem that it would become.

The present invention has been made to solve the above-mentioned conventional problems, and provides an optical displacement gauge provided with an actuator mechanism capable of ensuring stability during high-speed and high-acceleration movements. Is the first purpose.

The present invention also provides an optical displacement gauge having an actuator mechanism capable of preventing a measurement error when the movable portion of the actuator is held by the parallel leaf spring mechanism. The purpose is 2.

[0008]

According to the present invention, in an optical displacement meter, a focusing lens arranged to face a surface of an object to be measured, a movable portion holding the focusing lens, and the movable portion. A parallel leaf spring mechanism for movably holding the movable part in the displacement measuring direction, a drive system for driving the movable part in a non-contact manner, and an encoder for detecting the displacement of the movable part in the measuring direction. The position of the center of gravity of the entire movable part, including the lens,
Substantially so that it exists on the line of force of the drive system,
The first object is achieved.

According to the present invention, in a similar optical displacement gauge, the optical axis of the focusing lens is substantially in the plane including the inflection part on the movable part side of the parallel leaf spring. Thus, the second object is achieved.

[0010]

In the first aspect of the present invention, as illustrated in FIG.
Since the position of the center of gravity G of the entire movable portion 40 including the focusing lens 20 is substantially on the force line WL of the drive system including the pair of drive coils 62 and the magnet 64, for example. Since the displacement due to the moment around the center of gravity G of the movable portion does not occur when the actuator is driven, it is possible to control the actuator with high accuracy when measuring an object to be measured that is displaced at high speed.

It should be noted that, as shown in FIG.
When the plate is held by using the parallel leaf spring mechanism constituted by the leaf springs 60 parallel to each other, when the inflection portion I of the leaf spring and the optical axis OA of the focusing lens 20 are deviated as shown in FIG. When a disturbance is applied to, a moment around the inflection portion I is generated. At this time, if the deviation between the inflection portion I and the optical axis OA is l and the rotation amount due to the moment is Δθ, as shown in FIG.
When θ is close to 0, the surface position of the object to be measured and the optical axis of the focusing lens deviate by l Δθ as shown in the following equation, and this may cause a measurement error.

[0012]

[Equation 1]

Therefore, in the second aspect of the present invention, as illustrated in FIG. 8, the optical axis OA of the focusing lens 20 is substantially in the plane including the movable portion side inflection portion IM of the parallel leaf spring 70. As a result, the amount of deviation of the focusing lens from the optical axis due to the disturbance is reduced to a negligible level, and the error in the measurement data due to the disturbance is suppressed.

[0014]

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

In the first embodiment of the present invention, as shown in FIGS. 2 to 4, the focusing lens 20 is arranged to face the surface of the object to be measured, and the lens barrel 22 for holding the focusing lens 20. And a pair of parallel leaf springs 6 for holding the movable portion 40 movably in the displacement measuring direction (vertical direction in FIG. 2).
A parallel leaf spring mechanism including 0, a drive system including a rectangular ring-shaped drive coil 62 and a magnet 64 for driving the movable portion 40 in a non-contact manner, and for detecting a measured displacement of the movable portion 40, The linear scale 50 fixed to the movable portion 40 is provided so that the position of the center of gravity G of the entire movable portion including the focusing lens 20 is on the force line WL of the drive system.

The movable portion 40 is a frame 4 having a substantially rectangular shape.
1, and the focusing lens 2 is provided at the lower end of the frame 41.
0 is fixed, and the scale 50 is fixed to the upper end. The movable portion 40 further includes a pair of parallel leaf springs 60.
Thus, it is held movably in the displacement measuring direction (vertical direction in FIG. 2) with respect to the displacement meter main body 8.

A beam splitter (not shown) is arranged immediately after the focusing lens 20, and the focusing lens 20 is provided.
Part of the light that has passed through is extracted laterally from the light extraction window 42 (FIG. 4) provided in the lens barrel 22, and the deviation from the reference distance between the focusing lens 20 and the measurement target 12 is detected. To a detection optical system (not shown).

The scale 50 has a center of gravity G of the movable portion 40.
In order to reduce the moment of inertia of rotation, the frame 41
It is offset and fixed to the movable portion center of gravity G side.

The parallel leaf spring 60 has a developed shape as shown in FIG. 6, and the notch 60A for forming the bent portion and the bent portion 60B on the side surface enhance the rigidity of the central portion and also bend the bent portion. The part I is arranged so as to come close to both ends of the effective length of the leaf spring. In the figure, 60C is a screwing hole.

The right end of a rectangular ring-shaped drive coil 62 of the drive system is fixed to the left side of the movable part frame 41 (the side opposite to the focusing lens 20).

On the other hand, as shown in FIG. 7, the magnets 64 are fixed inside the both ends of the E-shaped core 66 fixed to the displacement meter body 8 so as to be close to the drive coil 62. Further, the central portion 66C of the core 66 is adapted to be inserted through the inside of the drive coil 62.

When the drive coil 62 is fixed to the movable part 40 as in this embodiment, the mass of the movable part can be reduced, and high-speed movement is possible, which is convenient. On the contrary, it is obvious that the magnet may be attached to the movable portion 40.

In the present embodiment, the position of the center of gravity G of the entire movable portion 40 including the focusing lens 20 is determined by the force line W of the drive system.
Since it exists on L, the actuator is controlled with high accuracy when measuring the object to be displaced at a high speed without causing displacement due to the moment around the center of gravity of the movable part when the actuator is driven at high acceleration. can do.

Next, the second embodiment of the present invention will be described in detail.

The second embodiment is an optical displacement meter similar to the first embodiment, as shown in FIGS. 8 to 10.
The optical axis OA of the focusing lens 20 exists in the plane including the movable portion side inflection portion IM of the parallel leaf spring 70.

Therefore, as shown in FIG. 11, the parallel leaf spring 70 has a notch 70 for forming an inflection portion similar to that of the first embodiment.
In addition to A and the bent portion 70B, a circular opening 70C for inserting the lens barrel 22 of the focusing lens 20 is formed near the movable portion side inflection portion IM. In this embodiment, a circular opening 70D is also formed in the fixed side inflection portion IF to improve the bending performance of the leaf spring, but the opening 70B on the fixed side inflection portion IF side is omitted. Alternatively, other shapes are possible. In the figure, 70E is an opening 70C,
It is a notch for forming an inflection portion formed in 70D.

Since the other points are the same as those of the first embodiment, the description thereof will be omitted.

In the present embodiment, the optical axis 0A of the focusing lens 20 exists in the plane including the movable portion side inflection portion IM of the parallel leaf spring 70, so that FIG. As shown in the equation, the amount of deviation from the optical axis of the focusing lens due to disturbance can be made almost zero.

[0029]

[Equation 2]

In the present embodiment, not only the optical axis OA of the focusing lens 20 exists within the plane including the movable portion side inflection portion IM of the parallel leaf spring 70, but also the focusing lens 20 is movable. Since the position of the center of gravity G of the entire portion 40 exists on the force line WL of the drive system, the deviation amount of the focusing lens 20 due to the disturbance is set to almost 0, and the error in the measurement data due to the disturbance is suppressed. Not only is it possible to suppress the occurrence of a moment around the center of gravity during driving, but vibration characteristics are also improved.

In addition, in the second embodiment, the line of action WL of the driving force and the center of gravity G of the actuator movable portion do not necessarily have to coincide with each other.

In each of the above embodiments,
Although the objective lens is supposed to be movable, if it is desired to widen the measuring range, for example, a large aperture objective lens may be fixed and a small relay lens may be moved for focusing.

[0033]

As described above, according to the first invention,
Generation of a moment around the center of gravity during driving can be suppressed, vibration characteristics can be improved, and stability of the actuator during high-speed, high-acceleration motion can be improved.

According to the second aspect of the invention, the amount of deviation of the optical axis between the object to be measured and the focusing lens when a disturbance is applied can be reduced to a negligible level, and the measurement data of the disturbance can be obtained. The error can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an example of a conventional optical displacement meter.

FIG. 2 is a cross-sectional view showing a main part configuration of a first embodiment of an optical displacement meter according to the present invention.

3 is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 is a right side view of FIG.

FIG. 5 is a diagram for explaining the problems of the first embodiment.

FIG. 6 is a development view showing the shape of a leaf spring used in the first embodiment.

FIG. 7 is a sectional view showing a structure of a drive system of the same.

FIG. 8 is a cross-sectional view showing the main configuration of a second embodiment of the optical displacement meter according to the present invention.

9 is a bottom view of FIG.

FIG. 10 is a vertical sectional view taken along line XX of FIG.

FIG. 11 is a development view showing the shape of a leaf spring used in the second embodiment.

FIG. 12 is a diagram for explaining the effect of the second embodiment.

[Explanation of symbols]

 12 ... Object to be measured 20 ... Focusing lens 40 ... Movable part 50 ... Scale G ... Movable part center of gravity WL ... Driving system force line OA ... Optical axis 60, 70 ... Parallel leaf spring I ... Leaf spring inflection part IM ... Plate Spring flexible part side inflection part 62 ... Drive coil 64 ... Magnet 66 ... Core

Claims (2)

[Claims] 1. A focusing lens arranged to face the surface of an object to be measured, a movable part for holding the focusing lens, and a parallel leaf spring mechanism for movably holding the movable part in a displacement measuring direction. A driving system for driving the movable part in a non-contact manner, and an encoder for detecting a displacement in the measurement direction of the movable part, wherein the center of gravity of the entire movable part including the focusing lens is substantially An optical displacement meter, which is present on the line of force of the drive system. 2. A focusing lens arranged to face the surface of an object to be measured, a movable part for holding the focusing lens, and a parallel leaf spring mechanism for movably holding the movable part in a displacement measuring direction. A driving system for driving the movable portion in a non-contact manner, and an encoder for detecting a displacement in the measurement direction of the movable portion, wherein the optical axis of the focusing lens is substantially the parallel leaf spring. An optical displacement meter characterized by being present in a plane including an inflection part on the movable part side.