JPH03216512A - Method of detecting quantity of displacement of micro-object - Google Patents

Abstract

PURPOSE:To measure the quantity of the displacement of a micro-object to be measured with a high accuracy by holding an objective lens in a focusing position with respect to the micro-object to be measured and optically measuring the position of the objective lens in the focusing position. CONSTITUTION:A CD pickup 4 is rockably supported by a support member 2 via a parallel link 3 on one side of a substrate 1. An objective lens 5 with a reflecting plate 6 is mounted to the CD pickup 4. An optical displacement sensor 7 is provided on the other side of the substrate 1. When the eccentricity or the like of a drill 9, a micro-object to be measured, is measured, a master with the known eccentricity and a known diameter is first located in a V-shaped groove 11. The objective lens 5 is held in a focusing position by driving the CD pickup 4 and the focusing position is measured by the sensor 7. Then, the drill 9 is located in the groove 11 and a lens position is similarly measured. By comparing both measured values with each other, a displacement quantity with respect to the master can be accurately measured without being affected by the hysteresis of a focus coil.

Description

DETAILED DESCRIPTION OF THE INVENTION Fields of Industrial Application The present invention not only precisely measures the amount of displacement of a minute object, but also precisely measures the thickness, width, diameter, etc. of the minute object from this amount of displacement. The present invention relates to a method for detecting the amount of displacement of a minute object, which is effective when measuring the amount of displacement of a minute object.

[Prior Art] Conventionally, as a device for measuring the diameter, etc. of a minute object, an application proposed by the inventors of the present invention has already been filed (Utility Application No. 1-2126). This device includes a focus shift detection circuit that detects focus shift from the object to be measured, and drive control to bring the objective lens into focus according to the focus shift signal output from the focus shift detection circuit. The objective lens drive control circuit includes an objective lens drive control circuit and a drive mechanism, and a conversion means that converts an electric signal emitted from the objective lens drive control circuit into a length and takes it out. It is composed of a focus coil that drives the objective lens accordingly.

In this configuration, the out-of-focus signal emitted from the out-of-focus detection circuit is input to an objective lens drive control circuit, and the objective lens is always kept in focus by a control voltage applied from the control circuit to the focus coil. Movement controlled. At the same time, the control voltage generated from the objective lens drive control circuit is converted into a displacement amount by the conversion means, and the diameter of the object to be measured is obtained from the displacement amount.

Problems to be Solved by the Invention However, in the above device, the objective lens is driven to be in focus by applying a control voltage to the focus coil, and the control voltage at this time is Since the focus coil is converted into a displacement amount, an error occurs in the measured value, which is the unique relationship between the control voltage and the displacement amount in the focused state, due to the hysteresis of the focus coil.

Also, is it possible to directly detect the amount of displacement of the object using a commercially available triangulation method and an optical displacement sensor? ) Therefore, the micro object (10 μm
) could not be directly detected.

The present invention has been made in view of such conventional problems, and provides a method for detecting displacement of a minute object, which makes it possible to precisely measure the amount of displacement of a minute object using the optical displacement sensor. The purpose is to provide the following.

Means for Solving the Problems] In order to solve the above problems, the method for detecting the amount of displacement of a minute object according to the present invention includes: holding an objective lens at a focused position with respect to the object; It is configured to measure the position of an objective lens held in a non-contact state.

[Operation] In the above configuration, since the position where the objective lens focuses on the object is always constant, the objective lens is held at the in-focus position with respect to the object, so that the object is not displaced. The objective lens will be displaced by the same amount of displacement as that of the first lens. Therefore, if the position of the objective lens is measured, the value will match the amount of displacement of the object.

At this time, since the position of the objective lens is detected in a non-contact state, there is no influence on the holding force of the objective lens, and no errors occur in the position of the objective lens itself. Moreover, since the position of the target is indirectly measured by measuring the position of the objective lens without directly measuring the position of the target, even if the target is minute, the beam diameter is large. Triangulation optical displacement sensors may be used.

[Example] An example of the present invention will be described below with reference to the drawings. That is, FIGS. 1 and 2 show the apparatus used in this embodiment, in which a support member 2 is erected and fixed at one end of a base 1, and a contact spring is attached to the support member 2. A CD Vinocqua knob 4 is supported so as to be swingable in the horizontal direction via a parallel link 3 . The CD pinoquanopter 4 is a known pinoquanopter used in CD players, and has an objective lens 5 and is driven in the horizontal direction by a focus coil (not shown). A reflecting plate 6 is provided.

On the other hand, an optical displacement sensor 7 using triangulation is fixed to the other end of the base 1, and the optical displacement sensor 7 transmits light from a built-in LED to the reflector 6. It is provided with an output section O that emits light toward the light beam and an input section I that includes a built-in PSD that detects the incident angle of the light reflected on the reflection plate 6.

Furthermore, on the base 1, a drill 9 as a target object is placed.
A mounting table 10 that supports the objective lens 5 is erected and fixed in front of the objective lens 5. The drill 9 is placed in a V-shaped groove ll provided at the upper end of the mounting table 10 for radial positioning, and is also axially positioned by a stopper 12 abutting the rear end. It has been accomplished.

In the above configuration, when measuring the eccentricity and diameter of the drill 9, a mask whose eccentricity and diameter are known in advance is placed in the V-shaped groove 11, and the mask is placed on the V-shaped groove 11. On the other hand, the focus coil drives the CD pinometer 4 so that the objective lens 5 is in focus, and the CD pinometer 4 provided with the objective lens 5 is held at this in-focus position. Then, the optical displacement sensor 7 measures the position of the objective lens 5 held at the focused position, and the measured position is stored or recorded.

Next, the mask is removed from the V-shaped groove 11, and then the trill 9, which is the object to be measured, is placed in the V-shaped groove l1, and the objective lens 5 is focused on the drill 9 in the same manner as described above. The objective lens 5 is held at this position, and the position is measured by the optical displacement sensor 7.

Here, since the position where the objective lens 5 focuses on the object is always constant, the distance between the mask and the objective lens 5 and the distance between the trill 9 and the objective lens 5 are equally constant. . Therefore, by comparing the position measurement value of the objective lens 5 when measuring the mask with the position measurement value of the objective lens 5 when measuring the trill 9, the amount of displacement of the I-rill 9 with respect to the mask can be obtained, and the displacement Based on the amount, the eccentricity and diameter (twice the maximum radius) of the trill 9 can be calculated.

That is, instead of converting the voltage and current of the focus coil when holding the objective lens at the in-focus position into the amount of displacement, the amount of displacement of the objective lens 5 is directly determined. The amount of displacement of the trill 9 can be precisely measured without any error caused by the hysteresis of the focus coil that drives the trill 5.

Moreover, the position of the objective lens 5 is determined by the optical displacement sensor 7.
Since the measurement is performed in a non-contact manner, the objective lens 5
There is no influence on the holding force of the objective lens 5, and no errors occur in the position of the objective lens 5 itself.

Furthermore, the optical displacement sensor 7 indirectly detects the displacement amount of the drill 9 by measuring the position of the objective lens 5 without directly measuring the position of the drill 9. Even if an optical displacement sensor 7 with a beam diameter of 50 μm or more is used, the displacement of a minute object having a diameter smaller than the beam diameter can be measured, and the measurement can be carried out at low cost using off-the-shelf equipment. It becomes possible to make it possible.

[Effects of the Invention] As explained above, the present invention holds an objective lens at a focused position with respect to an object, and measures the position of the objective lens held at this focused position. , there is no error in the measured value due to the hysteresis of the focus coil that holds the objective lens, and it is possible to accurately detect the amount of displacement. Since it is possible to use a sensor, it is possible to put it into practical use at low cost.

In addition, since the position of the objective lens is measured in a non-contact manner, the objective lens can be positioned at the in-focus position during measurement without affecting the holding force of the objective lens. This makes it possible to accurately detect the amount of displacement of a minute object.

[Brief explanation of drawings]

FIG. 1 is a plan view of a device used in an embodiment of the present invention, and FIG. 2 is a front view of the device. 3...Parallel link, 4...CD big up, 5.
... Objective lens, 6... Reflection plate, 7... Optical displacement sensor, 9... Trill (object).

Claims (1)

[Claims] (1) Micro object displacement detection characterized by holding an objective lens at a focused position relative to the object and measuring the position of the objective lens held at this focused position in a non-contact state. Method.