JPS6271803A - Displacement transducer - Google Patents

Abstract

PURPOSE:To measure the quantity of displacement of a surface to be measured from the quantity of movement of a lens by irradiating the object surface with light through a lens and moving the lens so that the lens is put in focus on the object surface all the time. CONSTITUTION:When a position sensor 8 is placed at equivalently the same position with a spot light source 7, reflected light shifts in incidence position on the sensor 8 according to the position of the object surface 3, so as in-focus state is known from the output of the sensor 8 and an automatic focus mechanism is so constituted that the output is fed back. Consequently, the lens 2, etc., is so moved that luminous flux emitted by the light source 7 is focused on the object surface 3 all the time, and the quantity of displacement of the object surface 3 is measured from the current quantity of movement. Further, reflected light shifts in incidence position on the 2nd position sensor 9 according to the inclination of the object surface 3, so the inclination of the object surface 3 is measured from the output of the sensor 9.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical displacement transducer.

More specifically, light is irradiated onto the measurement target surface through a lens, and the position of the lens is moved so that it is always focused on the 1I11 constant target surface, and the measurement target surface is determined from the amount of movement of the lens at this time. The present invention relates to a displacement converter in which the displacement amount of 11111 is fixed.

[Conventional technology]

Conventionally, as an example of an optical displacement converter, a device δ as shown in FIG. 9 has been put into practical use. The displacement converter shown in the figure irradiates parallel light beams emitted from a light source 1 onto a surface to be measured 3 via a lens 2, and also irradiates a parallel light beam emitted from a light source 1 to a surface to be measured 3 through a lens 2. The position is moved, and the amount of displacement of the surface to be measured 3 is measured from the amount of movement of the lens 2 at this time. Here, a cylindrical lens 4 and a 4-split sensor 5 are used to detect whether or not the focus is on the measurement target surface 3, and a half mirror placed on the opposite side of the lens 2 directs the reflected light from the measurement target surface 3. -6 guides the light spot to the cylindrical lens 4, and a four-division sensor 5 detects changes in the shape of the light spot obtained by the cylindrical lens 4.

In other words, the shape of the light spot projected onto the four-division space 5 is as shown in Fig.
When the upper focus is below 2, this is called the focus state (on state), the light beam incident on the cylindrical lens 4 is a parallel light beam, so the shape of the light spot on the 4-split sensor 5 is , as shown by the solid line a in the figure, is circular. In addition, when the poem is out of focus, the light beam that enters the cylindrical lens 4 is no longer parallel, so the light spot becomes an elliptical shape whose inclination direction changes depending on the focus shift, as shown by dashed lines C and C. Become. Therefore, by performing Jγ processing on the outputs 51 to S4 from the 4-split sensor 5, for example, as (S1+S3)-C52+S4), the shape of the light spot can be detected and the position of the focal point can be determined. Note that the output of this 4-split sensor 5 is used as a feedback signal for an automatic focusing mechanism that moves the lens 2 to always focus on the surface 3 to be measured.

(Problem to be solved by the invention) However, the above-mentioned cylindrical lens 4
In the displacement transducer using the 4-split sensor 5, if the measurement target surface 3 has an inclination, as shown in FIG.
Since the position of the light spot projected onto the 4-split sensor 5 is shifted from the center, the outputs S1 to S4 of the 4-split sensor 5 are not balanced even in the focused state, making it impossible to perform accurate autofocus operation. I become unable to do so. For this reason, the inclination of the surface 3 to be measured must be suppressed to within ±1°.

The present invention eliminates the drawbacks of conventional devices as described above, and realizes a displacement transducer with a simple configuration that can accurately measure the amount of displacement even when the surface to be measured has a relatively large inclination. It is intended to.

Another object of the present invention is to realize a displacement transducer that can simultaneously measure the amount of displacement and the inclination of a surface to be measured.

Means for Solving Problem c] The displacement converter of the present invention irradiates light onto the measurement target through a lens, and also positions the lens so that the measurement target is always focused on the surface. In displacement conversion 5, in which the amount of displacement of the surface to be measured is measured from the movement value of the lens at the time of step 2, a luminous flux emitted from a point light source is irradiated onto the surface to be measured 9 through the lens. Along with that, light comes in! I
J (A position sensor capable of detecting the position of the performer is placed at the same position as the point light source and at a certain distance from the point light source, and the output of the position sensor of the performer is transferred to the lens, the point light source, etc.) The sensor is used as a feedback signal for an automatic focusing mechanism that moves the position of the sensor, and the difference in output from the two position sensors is used to measure the inclination of the surface to be measured.

(Function) If a point light source is used as the light source and the first position sensor is placed equivalently at the same position as the point light source as in 2, in the focused state, the distance from the surface to be measured is The reflected light forms a real image at the position of the first position sensor (point light source), and since the incident position of the reflected light at this time on the first position sensor is always constant, the first position It is possible to detect whether or not the focus is on the surface to be measured from the output state of the sensor, and by using the output of the first position sensor as feedback No. 11 of the self-focus and ζ point mechanism, measurement can be performed. The amount of displacement of the target surface can be automatically measured.In addition, the position where the reflected light from the target surface forms a real image is the position of the point light source) regardless of the path of the light beam, so the measurement Even if the target surface is tilted, the amount of displacement can be accurately measured as long as the reflected light enters the lens.Furthermore, as described above, the first f at a certain interval to the position sensor of
Since the second position sensor is arranged δ, the output of the second position sensor corresponds to the inclination of the surface to be measured, and by detecting the difference between the outputs of these position sensors, the slope of the surface to be measured can be determined. Tilt can also be measured at the same time.

〔Example〕

FIG. 1 is a configuration diagram showing an embodiment of a displacement transducer of the present invention. In the figure, the same parts as in FIG. 9 are designated by the same reference numerals. For example, 7 is a point light source arranged on the axis of the lens 2, and 8 is equivalently focused light rA via the half mirror 6.
a first position sensor located at the same position as 7;
is the first position sensor 8 via the half mirror 10.
This is a second position sensor placed at a position spaced apart from the second position sensor. The light beam emitted from the point light source 7 has a fixed angle with respect to the axis of the lens 2, and is irradiated onto the measurement target surface 3 via the lens 2.

Further, the light reflected by the target surface 3 enters the ffs 1 and the second position sensors 8, 9 via the lens 2 and half mirrors 6, 10.

Furthermore, lens 2. Half mirrors 6, 10, point light source 7 and position sensor 8. S is integrally supported and moved by an automatic focusing mechanism (not shown), and 71I! The distance from the I constant target surface 3 is arbitrarily adjusted.

FIG. 2 is a configuration diagram showing an example of position sensors 8 and 9 that detect the incident position of reflected light incident through the lens 2. As shown in FIG. In the figure, the first position sensor 8 is illustrated. As shown in the figure, the position sensor 8 has a uniform p-type resistance layer 82 on one or both sides of a high-resistance silicon 81 (i-layer), and a PN junction with a photoelectric effect is formed on the surface layer. A pair of electrodes A and B for taking out No. 13 are provided at both ends of the layer. In the position sensor 8 having such a configuration, the distance between the electrodes A and B is determined, the 4ff stake is set as RL, and the electric
If the distance from A to the light incident position is X, and the resistance of that part is Rx, then the photogenerated charge generated at the light incident position is:
A charging current of 1° is proportional to the incident energy of the light, is divided according to the near resistance ωRx and (RL-Rx), and is taken out from the electrodes A and B at both ends as a current ＾, IB.

Therefore, these currents IA and IB are ■＾−+o (RL
-Rx) /RL-To (L-x)/Lra
m Io -RX/RL@To -x/L, and the ratio IA/IB of each current IA and IB is +A/IB-(
L - x) / x, so by finding the values of currents IA and IB,
The incident position of the light can be determined regardless of the magnitude of the incident energy.

FIG. 3 shows a two-dimensional structure of the position sensor 8 having the operating principle as described above.

As shown in the figure, each electrode Ax, Ay, Bx,
The ratio of the current extracted from By includes positional information in the X-axis direction and the Y-axis direction at the light incident position,
By processing these, it is possible to know the two-dimensional incident position.

Now, returning to Fig. 1, when the focus is on the measurement target surface 3 (in-focus state), the distance between the point light source 7 and the lens 2 is Ql, and the distance between the lens 2 and the measurement target surface 3 is Ql. The distance is Q2. If the focal length of the lens 2 is f, then the relational expression 1/Ql + 1/Q2 - 1/f holds true, and after the reflected light from the measurement plane 3 passes through the lens 2, it returns to the position of the point light source 7. It becomes two that return so as to form a real image at δ. At this time, since the first position sensor 8 is equivalently placed at the position of the focused light Fi7, the reflected light is incident on this position sensor 8, and the position sensor 8 detects the incident position.

Hereinafter, the description will proceed with reference to the incident state of the reflected light on the first position sensor 8.

Now, if the surface to be measured 3 is displaced to a position of 3° in the figure, the direction of the beam of light irradiated on the surface to be measured 3 will deviate from the point position, so the path of the reflected light will be as shown by the broken line. Along with this, the position sensor 8 in the reflected light
The incident position will also move. Furthermore, at this time, since the imaging position of the reflected light is also shifted from the position sensor 8, a spot with a certain degree of spread comes to be incident on the position sensor 8.

FIG. 4 shows the relationship between the incident position of the reflected light and the spot size on the position sensor 8.

In the figure, if the incident of the reflected light at the focused state (1?1 is PO), the spot diameter at this time is the smallest, and as the measurement target surface 3 deviates from the focal position, the incident position δ also changes to P.
l, move in the P2 direction or P3°F4 force direction,
The spot diameter also gradually increases. For example, if the incident position oscillates in the P1 direction when the measurement image plane 3 becomes closer than the focal position, then when the measurement image plane 3 becomes farther away from the focal position, the incidence position changes in the P3 direction. move to.

In this way, if the position sensor 8 is placed equivalently at the same position as the point light source 7, the incident position of the reflected light on the position sensor 8 will change depending on the C position of the measurement target surface 3, so the position The in-focus state can be known from the output of the sensor 8, and if an automatic focusing mechanism is configured using this output as a feedback signal, the light beam emitted from the point light source 7 will always be focused on the measurement target surface 3. The lens 2 and the like can be moved at this time, and the amount of displacement of the surface to be measured 3 can be automatically measured from the amount of movement at this time.

Let's consider the case where the measurement plane 3 has an inclination in 22. In the case of :, the path of the light reflected from the measurement target surface 391 will be different from that in the case of FIG. 1, but due to the nature of the lens 2, if the focal position is on the measurement target surface 3, Since the position where the reflected light forms an image does not change, the incident position of the reflected light on the position sensor 8 also does not change, and the in-focus state is accurately detected from the output of the position sensor 8, as in the case of the upper ME. be able to. Note that when the measurement target surface 3 is tilted, the incident position of the reflected light on the position sensor 8 changes as shown in FIG. 5, for example, and the measurement target surface 3
moves with the displacement of . As is clear from the figure, when the surface to be measured 3 is at the focal point a, the incident position r! Since the iPO is at the same position as shown in FIG. 4, the output of the position sensor 8 at this time is also the same value, and the amount of displacement can be measured without being affected by the inclination of the surface 3 to be measured.

Next, the operation of measuring the inclination of the measurement target surface 3 using the output of the second position sensor 9 will be explained.

ffi! +iL As shown in FIG. 1, the second position sensor 9 is arranged at an equivalent distance from the first position sensor 8.

For this reason, an automatic focusing mechanism is provided, and a focus is placed on the measurement target surface 3.
, near, are correct, the reflected light that returns via the lens 2 is focused on the first position sensor 8, where it forms an image, and enters the local position δ [PO]. f, a light beam that is deviated from the imaging state is incident on the second position sensor 9.

FIG. 6 shows an example of the incident state of reflected light on the first and second position sensors 8 and 9, with their optical axes aligned. As shown in the figure, in the focused state, the first position sensor 8 is at the home position (PO).
The transmitted light enters the second position sensor 9, and this localization ε(PO) does not change. Therefore, when the path of the reflected light changes according to the inclination of the measurement target surface 3, the second position sensor 9
Only the incident position on the position sensor 9 changes.

FIG. 7 shows the incident position of the reflected light on the second position sensor 9. For example, when the measurement target surface 3 is tilted around the X-axis, the incident position δ moves in the direction of the arrow X. Assuming this, when the surface to be measured 3 is tilted around the Y-axis, it moves in the direction of the arrow y.

In this way, since the incident position of the reflected light on the second position sensor 9 changes according to the inclination of the measurement target surface 3, the position of incidence of the reflected light on the measurement target surface 3 is
It is possible to measure the slope of In the displacement transducer of the present invention, the inclination of the surface to be measured 3 is measured by determining the difference between the outputs of the first and second position sensors 8.9 and comparing this with data measured in advance. are doing. Note that, as described above, since the output (incidence position) of the first position sensor 8 is always constant, it is also possible to determine the inclination of the measurement target surface 3 only from the output of the second position sensor 9.

In addition, as described above, the path of the reflected light can be detected from the difference in the outputs of the first and second position sensors 8 and 9, so if this information is used, the reflected light can be directed to the lens 2 during measurement. Since it is possible to know which part of the lens 2 is passing through, measurement errors due to aberrations of the lens 2 can be corrected. Generally, in lens 2,
Since the influence of aberrations differs depending on the position through which the reflected light passes, if the path of the reflected light is known, the 2P5E results can be corrected accordingly, making it possible to perform more accurate measurements.

FIG. 8 is a configuration diagram showing an example of an automatic focusing mechanism used in the displacement converter of the present invention. In the figure, 8 is the first position sensor, and as mentioned above, it generates an output signal S (X, Y) corresponding to the position of the reflected light to J.
is a servo amplifier that outputs the target value SET and the feedback signal S (X, Y
), a drive signal Sd for moving the lens 2, etc. is generated. 12 is a power amplifier,
13 is a motor for moving the lens 2 and the like.

In the automatic focus m side configured as above, the target side SET is set equal to the output S (X, Y) of the position sensor 8 in the focused state, and the servo amplifier 1
1 drives the motor 13 so that the deviation ΔS becomes ambiance, so the focal point of the light beam irradiated by the lens 2 etc. is always 2+111
It is moved so that it is above the fixed object. Therefore, since the amount of drive of the motor 13 is proportional to the displacement of the surface to be measured 3, the amount of displacement of the surface to be measured 3 can be measured by detecting this amount of drive or the 8 degrees of movement of the lens 2, etc. can do.

In addition, as described in 11'i1, when the surface to be measured 3 has an inclination, the angle of incidence of the reflected light on the position sensor 8 changes, so the displacement of the surface to be measured 3 changes when the position sensor The rate (gain) at which the output of 8 changes will change according to the inclination of the surface 3 to be measured. Therefore, based on the inclination of the measurement target surface 3 measured as described above, the position sensor 8
If the servo gain of the servo amplifier 11 is changed according to the data obtained in advance,
Controllability in automatic focusing can be improved.

In addition, in the above explanation, there is a difference between 27 is placed on the axis of the lens 2, and the position sensor 8 is placed isometrically at the same position as the point light source 7 using the half mirror 6.
The arrangement relationship with is not limited to this. In addition, the means for changing the path of the light emitted from the focused light fi 7 and the reflected light from the measurement target surface 3 is not limited to the half mirrors 6 and 10, but is, for example, a prism or a polarizing beam splitter. It may be. Furthermore, a lens 2 that irradiates the measurement target 4 with a light flux and forms an image of the anti-p light from the measurement target surface 3 on the position sensor 8.
is not limited to a single lens, but may be a combination of independent partial lenses. In particular, since the position at which the light emitted from the focal beam rA7 enters the lens 2 does not always change, the surrounding lens portions are often not required.

In addition, in the above explanation, the case where the inclination of the measurement target surface 3 is measured using the two position sensors 8 and 9 was illustrated, but when the lens 2 is moved by a certain amount and the first position sensor 8 is By creating an incident state equivalent to that of the second position sensor 9, the inclination of the measurement target surface 3 can be measured using only one position sensor 8. In other words, if you displace the lens 2 etc. by a certain amount from the focused state and measure the change in the output of the position sensor 8 at this time, the amount of change and direction of the change in the incident position of the reflected light at this time will be determined by the reflected light. Since the angle corresponds to the path of 9, the inclination of the measured surface 3 can be determined by comparing it with data measured in advance.

[Effect of invention■]

As explained above, in the displacement converter of the present invention, light is irradiated onto the surface to be measured through the lens, and the position of the lens is moved so that the surface is always focused on the surface to be measured.
In a displacement converter that measures the amount of displacement of the surface to be measured from the amount of movement of the lens at this time, a beam of light emitted from a point light source is irradiated onto the surface to be measured through the lens, and the light beam is A position sensor capable of detecting the incident position T is placed isometrically at the same position as the point light source and at a position spaced apart from it, and the output of the former position sensor is connected to the lens and the point light source. Automatic focus that moves the position of the light source, etc. l! In addition to using it as a horizontal feedback signal, the difference in output from the two position sensors is used to measure the inclination of the surface to be measured.
In the focused state, the reflected light from the surface to be measured forms a real image at the position sensor (point light source).
Moreover, since the incident position of the reflected light on the position sensor at this time is always constant, it is possible to detect whether or not the focus is on the measurement target surface from the output state of the position sensor. Relatively big! 1111
It is possible to realize a displacement transducer with a simple configuration that can accurately measure the amount of displacement even if there is a movement, and can also measure the inclination of the surface to be measured at the same time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the displacement transducer of the present invention,
FIGS. 2 and 3 are configuration diagrams showing an example of a position sensor used in the displacement converter of the present invention, and FIGS. 4 and 5 show the incident position and spot state of reflected light on the position sensor. Explanatory diagrams, FIGS. 6 and 7 are explanatory diagrams showing the incident state of reflected light at the first and second position sensors 8 and 9, and FIG. 8 is an automatic focusing mechanism used in the displacement converter of the present invention. FIG. 9 is a configuration diagram showing an example of a conventional displacement converter. FIGS. This is an explanation X showing the spot shape. 1...Light source, 2...Lens, 3...Measurement target surface,
4... Cylindrical lens, 5... 4-split sensor, 6.10... Half mirror 17... Point light source, 8°9... Position sensor, 11... Servo amplifier,
12...Power amplifier, 13...Motor, SW...
·switch. Figure I Figure 2 Figure 3 Figure 4 Figure 5 Figure 5

Claims (1)

[Claims] Light is irradiated onto the surface to be measured through a lens, and the position of the lens is moved so that it is always focused on the surface to be measured, and the amount of displacement of the surface to be measured is measured from the amount of movement of the lens at this time. In the displacement converter, a point light source that moves together with the lens, a first position sensor that is equivalently arranged at the same position as the point light source and moves together with the lens, and a point light source that moves together with the lens; a second position sensor disposed equivalently at a constant interval; and an automatic focus that receives an output from the first position sensor and moves the position of the lens so that the output becomes a constant value. and a mechanism for measuring the amount of displacement of the surface to be measured from the amount of movement of the lens, and measuring the inclination of the surface to be measured from the difference between the outputs of the first and second position sensors. A displacement transducer.