JPH0791925A - Device for measuring thickness - Google Patents

Abstract

PURPOSE:To carry out very accurate measurement, by emitting a beam toward an object to be measured in a constant direction by disposing an end of an optical fiber near the reflection side of a virtual reflecting point of the beam, and by leading the beam reflected on the object therethrough into the other end to receive the beam. CONSTITUTION:Respective ends 27, 34 of optical fibers 25, 32 are disposed near reflection sides of virtual reflecting points at which laser beams from light emitting elements 21, 31 of respective detecting units 6, 7 are reflected. In a measuring time, when respective units 6, 7 are moved to a lens 3 and beams from elements 21, 31 are reflected on the respective top and bottom faces of the lens 3, reflected beams are certainly led through ends 27, 34 into photodetectors 26, 33. Therefore, even if photodetectors 26, 33 are kept apart from reflecting points of the lens 3, reflected beams can correctly be detected without the influence of peripheral environment of ambient temperature, atmosphere, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thickness measuring device for measuring the thickness of an object to be measured such as a lens.

[0002]

2. Description of the Related Art Generally, a dial gauge is widely used as a thickness measuring device for measuring the thickness of an object to be measured such as a lens. The dial gauge is made by contacting the contact point with the upper surface of the measured object placed on the reference surface,
The small displacement of the probe with respect to the reference plane is magnified by a gear mechanism to measure the thickness of the object to be measured.

[0003]

However, in such a dial gauge, there is a problem that the surface of the object to be measured is scratched because the probe directly contacts the object to be measured. Therefore, it is not suitable for soft objects such as plastic lenses. Therefore, recently, a measuring device has been developed which measures the thickness of an object to be measured in a non-contact state by utilizing ultrasonic waves or air pressure. However, since such a thickness measuring device is easily affected by the surrounding environment such as temperature, humidity, and atmospheric pressure, there is a problem that accurate measurement cannot be performed unless measurement is performed in a measurement room where the environment is constant.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a thickness measuring device which is not easily affected by the surrounding environment and which can perform highly accurate measurement without performing measurement in a special measuring chamber. To aim.

[0005]

In order to achieve the above object, the present invention provides a mounting table on which an object to be measured is mounted, and a detection unit arranged above the mounting table so as to be vertically movable. The detecting unit is provided with a light emitting element that irradiates a light beam in a certain direction toward the object to be measured, and a tip portion is disposed in the vicinity of the reflection side at a virtual reflection point where the light beam from this light emitting element is reflected. It is characterized in that it has an optical fiber that introduces the light beam reflected by the object to be measured from the tip part and guides it to the other end part, and a light receiving element that receives the light beam guided by this optical fiber. As an example of the thickness measurement by the thickness measuring device, as described in claim 2, the upper surface of the mounting table is used as a reference plane, and the origin of the detection unit is set with respect to the reference surface, and then the object is placed on the mounting table. By placing the measurement object and lowering the detection unit toward the measurement object, the light beam from the light emitting element is reflected by the measurement object, and the reflected light beam is received by the light receiving element via the optical fiber. The distance from the origin of the detection unit to the reflection point on the upper surface of the measured object is measured, and the thickness of the measured object is calculated based on this measurement data.

[0006]

According to the present invention, since the tip of the optical fiber is arranged near the reflection side at the virtual reflection point where the light beam from the light emitting element is reflected, the light beam from the light emitting element is reflected by the object to be measured during measurement. Then, this reflected light beam can be reliably introduced from the tip of the optical fiber,
The introduced light beam can be reliably guided to the light receiving element by the optical fiber. Therefore, even if the light receiving element is far from the reflection point, the reflected light beam can be accurately sensed without being affected by the surrounding environment, and thus the environment does not have to be measured in a special measurement room. Highly accurate measurement is possible. In this case, as described in claim 3, the upper detection unit is arranged above the mounting table so as to be vertically movable, and
A lower detection unit is arranged below the mounting table so as to be movable in the vertical direction, and a through hole for the lower detection unit to detect the lower surface of the measured object is provided at a place on the mounting table where the measured object is mounted. If the upper detection unit measures the distance from the origin to the upper surface of the object to be measured, and the lower detection unit measures the distance from the origin to the lower surface of the object to be measured, the front and back surfaces such as a meniscus lens can be measured. Highly accurate measurement is possible even on a non-parallel curved object.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an external front view of the thickness measuring device. This thickness measuring device includes a measuring unit 1 and a control unit 2. The measuring unit 1 is, as shown in FIGS. 2 and 3,
A plate-shaped mounting table 4 on which a lens (measurement object) 3 is mounted,
An elevating device 5 arranged on the back side (right side in FIG. 2) of the mounting table 4, an upper detection unit 6 attached to the elevating device 5 and located above the mounting table 4, and an elevating device 5. And a lower detection unit 7 located below the mounting table 4. In the mounting table 4, a through hole 8 is formed at a position where the lens 3 is mounted so that the lower detection unit 7 can measure the lower surface of the lens 3, and the vertical height of the measuring unit body can be adjusted. Is fixed as. The lifting device 5 has bearings 9a at the upper and lower ends in a vertical state.
A ball screw 9 rotatably held by 9b, a pulse motor 10 for rotating the ball screw 9, and a ball screw 9 that is screwed to the ball screw 9 and is vertically moved according to the rotation of the ball screw 9. It consists of body 11.

In this case, the vertical movement distance of the lifting / lowering body 11 is determined by the number of revolutions of the pulse motor 10, that is, the number of pulses given to the pulse motor 10. A limit disk 12 is provided on the rotary shaft 10a of the pulse motor 10, and one slit hole 12a is formed in the peripheral edge of the limit disk 12. In addition, in the vicinity of the peripheral edge of the limit disk 12, a "U" -shaped rotational position detecting element 13 is arranged when viewed from the side. The rotational position detecting element 13 detects a specific position on the rotation surface of the limit disk 12 when the slit hole 12a of the limit disk 12 corresponds, and thereby determines the rotation start position of the pulse motor 10. There is. A measurement start position detecting element 14 for detecting the measurement start positions of the upper detection unit 6 and the lower detection unit 7 is arranged at a predetermined position laterally of the ball screw 9. Above the measurement start position detecting element 14, an upper limit position detecting element 15 for detecting the upper limit position of the lift 11 is provided.
And the measurement start position detecting element 14
A lower limit position detecting element 16 for detecting the lower limit position of the lifting body 11 is arranged below the. Each of these detection elements 14 to
Similar to the rotational position detection element 13, each of the reference numerals 16 has a U-shape when viewed from a plane, and outputs an OFF signal when one limit plate 11a protruding from the lifting body 11 is inserted. Thus, the measurement start position, the upper limit position, and the lower limit position of the lifting body 11 are detected. It should be noted that the limit plate 11a provided on the lifting body 11 moves in the up-down direction together with the lifting body 11 between the upper limit position detection element 15 and the lower limit position detection element 16.

The upper detection unit 6 is equipped with a unit case 20 which is attached to the upper front surface of the lifting body 11 and moves in the vertical direction as the lifting body 11 moves. Inside the unit case 20, a light emitting element 21 is fixed by a fixing member 22 as shown in FIG. The light emitting element 21 is composed of a semiconductor laser or the like, and irradiates a laser beam having a laser spot (laser beam irradiation region) with a diameter of about 0.03 mm in a diagonally downward direction. In addition, inside the unit case 20,
A mounting member 23 is rotatably mounted by a support shaft 24 at a position substantially symmetrical with respect to the light emitting element 21. In this case, the tip of the mounting member 23 is
The laser beam emitted from the light emitting element 21 is located in the vicinity thereof without blocking the laser beam emitted from the light emitting element 21.

The mounting member 23 is provided with an optical fiber 25 extending from the front end to the rear end side, and a light receiving element 26 is provided at the rear end thereof. The optical fiber 25 is a linear body having a diameter of about 2.2 mm, and the tip portion 27 is attached near the reflection side at a virtual reflection point (indicated by the origin P1 in FIG. 3) where the laser beam from the light emitting element 21 is reflected. It is arranged with the tip of the member 23 slightly protruding,
At the time of measurement, the laser beam reflected by the lens 3 is introduced from the tip portion 27 and guided to the other end portion. In this case, in order to accurately introduce the laser beam reflected by the lens 3, the tip portion 27 of the optical fiber 25 has the upper half on the light emitting element 21 side in a plane parallel to the laser beam, as shown in FIG. It is formed, and the lower half is cut out to the inclined surface and covered with the light shielding mask 27a. In addition, the light receiving element 2
Reference numeral 6 receives the laser beam guided by the optical fiber 25 and outputs an electric signal (detection signal) to the control unit 2 described later. The mounting member 23 is a coil spring 28.
4 is urged in the counterclockwise direction in FIG. 4, and the stopper pin 20a provided on the unit case 20 is brought into contact with the stopper pin 20a to regulate the position thereof to a predetermined position. When they come into contact with each other, they rotate clockwise around the support shaft 24 against the spring force of the coil spring 28, turning on the micro switch 29 arranged in the vicinity thereof. The micro switch 29 outputs an ON signal to the control unit 2 to promptly stop the pulse motor 10.

On the other hand, the lower detection unit 7 includes an elevating body 11
The unit case 30 is attached to the lower front surface of the unit and moves in the vertical direction as the lifting body 11 moves.
Like the upper detection unit 6, the light emitting element 31 is fixed inside the unit case 30, and the optical fiber 32 and the light receiving element 33 are attached by a mounting member (not shown).
It is provided through. In this case, the light emitting element 31 irradiates the laser beam in a fixed direction obliquely upward. Further, the tip portion 34 of the optical fiber 32 is configured similarly to the optical fiber 25 of the upper detection unit 6,
It is arranged near the reflection side at a virtual reflection point (origin P2 in FIG. 3) where the laser beam from the light emitting element 31 is reflected. It should be noted that the upper detection unit 6 is also provided near the mounting member.
Similarly to, a micro switch (not shown) is provided.

As shown in FIG. 1, the control unit 2 includes a display unit 35, a power switch 36, a measurement start switch 37, a CPU, an arithmetic circuit (not shown), etc.
It controls the entire measuring device. That is, when the power switch 36 is turned on and the measurement start switch 37 is turned on, the control unit 2 gives an operation command to the light emitting elements 21 and 31 of the upper and lower detection units 6 and 7 and drives the pulse motor 10. , When each electric signal from each light receiving element 26, 33 and each micro switch 29 is given,
When the drive of the pulse motor 10 is controlled based on these signals and the respective detection signals detected by the upper and lower detection units 6 and 7 are given, the detection data (the number of pulses of the pulse motor 10) based on this Is calculated, and the thickness of the lens 3 is calculated by a calculation circuit based on the detected data.

Next, the measurement flow of this thickness measuring device will be described with reference to FIG. Before starting measurement, calibrate using a reference object (not shown) in advance.
Do the work. That is, the reference object is placed on the mounting table 4, and the thickness data of the reference object is input to the control unit 2. Then, the upper detection unit 6 and the lower detection unit 7 are arranged at the respective origins P1 and P2. Origin P here
1 and P2 are measurement start positions, and the lifting body 11
The limit plate 11a corresponds to the measurement start position detecting element 14, and the slit hole 12a of the limit disc 12 corresponds to the rotational position detecting element 13. In addition, each origin P
The distance L between 1 and P2 is always constant. In such a state, the pulse motor 10 is driven to move the lifting / lowering body 11 in the vertical direction, so that the upper detection unit 6 detects the distance from the origin P1 to the upper surface of the reference object as the number of pulses of the pulse motor 10. At the same time, the lower detection unit 7 detects the distance from the origin P2 to the lower surface of the reference object as the number of pulses of the pulse motor 10. And
The detection data is calculated by the control unit 2 to calculate measurement data, and the measurement data is compared with the thickness data of the reference object input in advance to perform the calibration process. After that, the thickness of the measured object is calculated by proportional calculation based on the thickness data of the reference object.

After the calibration process is performed in this way, the lens 3 is carried in at step S1, and step S2.
When the lens 3 is positioned on the mounting table 4 with, the measurement start switch 37 is turned on to start the measurement. Then, in step S3, the origins P1 and P2 of the upper and lower detection units 6 and 7 are confirmed. That is, in step S3, the limit plate 11a of the lifting body 11 is moved to the measurement start position detecting element 1
4 and slit holes 12a of the limit disk 12
Check whether or not corresponds to the rotational position detecting element 13. If these are not confirmed, the pulse motor 10 is driven until they are confirmed. When it is confirmed, the process proceeds to step S4 to drive the pulse motor 10 in the normal direction to lower the lifting body 11, and the process proceeds to step S5.

In step S5, it is determined whether or not the upper detection unit 6 has sensed the upper surface of the lens 3. That is,
The upper detection unit 6 descends together with the lifting / lowering body 11, the laser beam from the light emitting element 21 is reflected on the upper surface of the lens 3, and the reflected laser beam is introduced from the tip portion 27 of the optical fiber 25 to receive the light receiving element 26. Then, it is judged whether or not the light receiving element 26 receives this laser beam. When the upper detection unit 6 detects the upper surface of the lens 3 in step S5, the distance a from the origin P1 of the upper detection unit 6 to the reflection point on the upper surface of the lens 3 is measured as the number of pulses of the pulse motor 10, In step S6, the detection operation of the upper detection unit 6 is stopped.

Then, in step S7, the pulse motor 10 is driven in the reverse direction to raise the elevating body 11, and the process proceeds to step S8. In step S8, it is determined whether or not the lower detection unit 7 has detected the lower surface of the lens 3. That is, similarly to the above, the lower detection unit 7 rises together with the lifting body 11, the laser beam from the light emitting element 31 is reflected on the lower surface of the lens 3, and the reflected laser beam is directed to the tip portion 34 of the optical fiber 32. Is introduced into the light receiving element 33, and it is determined whether or not this laser beam is received by the light receiving element 33. Then, in step S8, the lower detection unit 7
When the lower surface of the lens 3 is sensed, the distance b from the origin P2 of the lower detection unit 7 to the reflection point on the lower surface of the lens 3
Is measured as the number of pulses of the pulse motor 10, the detection operation of the lower detection unit 7 is stopped in step S9, and the pulse motor 10 is driven to rotate in the forward direction to lower the elevating body 11 to detect the upper and lower detection units 6 respectively. , 7 as origin P
1. Return to P2.

After that, the process proceeds to step S10 to perform arithmetic processing. That is, in step S10, from the distance L between the origins P1 and P2 of the detection units 6 and 7, the distance a between the origin P1 of the upper detection unit 6 and the reflection point on the upper surface of the lens 3 and the lower detection unit 7 of the lower detection unit 7. By subtracting the distance b between the origin P2 and the reflection point on the lower surface of the lens 3, the thickness T {= L- (a + b)} of the lens 3 is calculated by proportional calculation based on the thickness data of the reference object. The thickness data calculated in this manner is displayed on the display unit 35 in step S11, and the measurement ends in step S12. Then, the lens 3 is removed from the mounting table 4 in step S13, and the lens 3 is unloaded in step S14.

When the detection units 6 and 7 do not sense the upper and lower surfaces of the lens 3 in steps S5 and S8, the process proceeds to step S15 to return the detection units 6 and 7 to the origins P1 and P2. In step S16, the measurement error is displayed on the display unit 35, and the process proceeds to step S17. In this step S17, for example, in step S5, the upper detection unit 6 cannot detect the upper surface of the lens 3 and descends too much, and the tip end portion 27 of the optical fiber 25 comes into contact with the upper surface of the lens 3, whereby the mounting member 23 is removed. Coil spring 2
When the micro switch 29 is turned on by rotating clockwise against the spring force of 8, and the pulse motor 10 is stopped by the micro switch 29, an error condition such as the stop of the pulse motor 10 is detected. To release. After that, the process returns to step S3, and stands by until the measurement start switch 37 is turned on.

As described above, in this thickness measuring device, the tips of the optical fibers 25 and 32 are located near the reflection side at the virtual reflection point where the laser beams from the light emitting elements 21 and 31 of the detection units 6 and 7 are reflected. Since the parts 27 and 34 are arranged,
When the detection units 6 and 7 move toward the lens 3 at the time of measurement and the laser beams from the light emitting elements 21 and 31 are reflected by the upper and lower surfaces of the lens 3, the reflected laser beams are reliably emitted. It can be introduced from the respective tip portions 27, 34 of the fibers 25, 32, and the introduced laser beam can be reliably guided to the light receiving elements 26, 33 by the optical fibers 25, 32. Therefore, even if the light receiving elements 26 and 33 are apart from the reflection point of the lens 3, the reflected laser light can be accurately sensed without being affected by the surrounding environment such as the temperature and the atmospheric pressure, and therefore the environment is constant. Highly accurate measurement is possible without having to measure in a special measurement room. In this case, in particular, in the tip end portions 27 and 34 of the optical fibers 25 and 32, half of the light emitting elements 21 and 31 side is formed in a plane parallel to the laser beam, and the other half is formed in an inclined surface so that the light shielding mask 27 is formed.
Since it is covered with a, unnecessary laser beams among the laser beams reflected by the lens 3 are shielded by the light shielding mask 2 having an inclined surface.
It can be blocked by 7a, so that the reflection position of the laser beam can be detected extremely accurately. By the way, when the ball screw 9 has a screw pitch of 2 mm, the pulse motor 10
Is the resolution of one revolution with 1000 pulses, the origin P
The measurement accuracy of the distances a and b from P1, P2 to each surface of the lens 3 is about ± 2 μm, and the diameter of the laser spot (0.
(03 mm) and the like, the measurement accuracy is as high as about ± 5 μm. Further, in this thickness measuring device, the upper detection unit 6 is arranged above the mounting table 4, and the lower detection unit 7 is arranged below the mounting table 4, and the upper detection unit 6 moves from the origin P1 to the upper surface of the lens 3. To the lower surface of the lens 3 from the origin P2 by the lower detection unit 7, the accuracy of even a curved surface-shaped object such as a meniscus lens whose front and back surfaces are not parallel is measured. High measurement is possible.

In the above embodiment, in order to set the origins P1 and P2 of the upper and lower detection units 6 and 7, the measurement start position detecting element 14, the upper limit position detecting element 15, and the upper limit position detecting element 15 are provided on the side of the ball screw 9. Although the lower limit position detection element 16 is arranged, the number of pulses of the pulse motor 10 is set in advance when the upper detection unit 6 is lifted from the reference plane, for example, with the upper surface of the mounting table 4 as the reference plane. The origins P1 and P of the upper and lower detection units 6 and 7, respectively.
2 may be set. By doing so, the number of detecting elements 14 to 16 can be reduced, and the structure can be simplified. Further, in the above embodiment, the mounting table 4
Although the detection units 6 and 7 are arranged in the up and down direction, respectively, the present invention is not limited to this, and when measuring only an object to be measured having at least one flat surface such as a plano-convex lens, the mounting table 4 is A structure in which the detection unit 6 is arranged only above may be used.

[0021]

As described above, according to the invention described in claim 1, since the tip of the optical fiber is arranged near the reflection side at the virtual reflection point where the light beam from the light emitting element is reflected, at the time of measurement. When the light beam from the light emitting element is reflected by the object to be measured, this reflected light beam can be reliably introduced from the tip of the optical fiber, and the introduced light beam can be reliably guided to the light receiving element by the optical fiber. it can. Therefore, even if the light receiving element is far from the reflection point, the reflected light beam can be accurately sensed without being affected by the surrounding environment, and the accuracy can be improved even if the measurement is not performed in a special measurement room where the environment is constant. High measurement is possible. According to the third aspect of the present invention, the upper detection unit is movably arranged in the vertical direction above the mounting table, and the lower detection unit is movably arranged in the vertical direction below the mounting table. A through hole is provided on the stand to allow the lower detection unit to detect the object to be measured.The distance from the origin to the upper surface of the object to be measured by the upper detection unit and the object from the origin to the object to be measured by the lower detection unit. Since the distance to the lower surface is measured, highly accurate measurement can be performed even on an object to be measured having a curved surface whose front and back surfaces are not parallel, such as a meniscus lens.

[Brief description of drawings]

FIG. 1 is an external front view of a thickness measuring device of the present invention.

FIG. 2 is a schematic configuration diagram of a measurement unit in FIG.

FIG. 3 is a front view of FIG.

FIG. 4 is a diagram showing an internal structure of the upper detection unit of FIG.

5 is an enlarged view showing a tip portion of the optical fiber shown in FIG.

6 is a diagram showing a measurement flow of the thickness measuring device of FIG.

[Explanation of symbols]

 1 Measuring Section 2 Control Section 3 Lens 4 Mounting Table 5 Lifting Device 6 Upper Detection Unit 7 Lower Detection Unit 8 Through Hole 21, 31 Light Emitting Element 25, 32 Optical Fiber 26, 33 Light Receiving Element

Claims (3)

[Claims] 1. A mounting table on which an object to be measured is mounted, and a detection unit arranged above the mounting table so as to be movable in the vertical direction, the detection unit facing the object to be measured. A light emitting element that irradiates a light beam in a fixed direction, and a tip portion is disposed near the reflection side at a virtual reflection point where a light ray from this light emitting element is reflected, and a light ray reflected by the DUT from the tip portion during measurement. A thickness measuring device, comprising: an optical fiber that introduces and guides the light to the other end, and a light receiving element that receives the light beam guided by the optical fiber. 2. The method according to claim 1, wherein the upper surface of the mounting table is used as a reference surface, and the origin of the detection unit is set with respect to the reference surface, and then the object to be measured is mounted on the mounting table and the detection is performed. Lower the unit toward the DUT,
When the light beam from the light emitting element is reflected by the object to be measured, the light receiving element receives the reflected light beam through the optical fiber, so that the object to be measured is detected from the origin of the detection unit. A thickness measuring device characterized by measuring the distance to a reflection point on the upper surface and calculating the thickness of the object to be measured based on this measurement data. 3. The upper detection unit according to claim 1, wherein the upper detection unit is vertically movable above the mounting table, and the lower detection unit is vertically movable below the mounting table. A through hole for the lower detection unit to detect the lower surface of the measured object is provided at a position where the measured object is placed on the mounting table, the upper detection unit and the lower detection unit. Is placed at the measurement start position which is each origin, by placing the object to be measured on the mounting table and moving the upper detection unit and the lower detection unit in the vertical direction, the upper detection unit Then, the distance from the origin to the upper surface of the object to be measured and the distance from the origin to the lower surface of the object to be measured are measured by the lower detection unit. The thickness measuring device and calculates the thickness of the object to be measured based.