JP3329950B2 - Optical displacement measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement measuring device represented by, for example, an optical micro (registered trademark of the applicant). That is, an optical displacement measurement device that irradiates light from a light source onto a measurement object, receives the reflected light with a photodetector, detects a displacement, and measures the displacement of the measurement object. The present invention relates to an optical displacement measuring device that receives light at a large incident angle with an optical position detector.

[0002]

2. Description of the Related Art As a method of measuring a displacement of a measurement object, there is a method conventionally known as a triangulation method. Japanese Patent Application No. 5-109885 filed by the applicant includes:
As a conventional example, a technique as shown in FIG. 5 is disclosed.
The light emitted from the light source 13 is condensed by the condenser lens 16,
The collected light is transmitted from the light projecting lens 14 to the object 18 to be measured.
To form a light spot on the surface to be measured. The light reflected and scattered from the light spot is reflected by the light receiving lens 15.
To guide the light to the light position detector 17 to form an image of the light spot on the light position detector.

Further, Japanese Patent Application No. 5-109885 discloses a technique in which the light projecting lens 14 and the light receiving lens 15 in FIG. 5 of the conventional example are replaced with one objective lens 21 as shown in FIG. . Here, the light emitted from the light source 19 is condensed by the emission lens 20, and the condensed light is irradiated from the objective lens 21 to the measurement object 18 to form a light spot on the measurement object surface. The reflected light scattered and reflected from this light spot is condensed by an objective lens 18 to be converted into a parallel light flux and guided to an imaging lens 23, and a light position detector 17 disposed obliquely with respect to the optical axis from the imaging lens 23. Make an image of the light spot on top.

The light position detector 17 is a position sensitive detector (PSD) as shown in FIG.
The light detection element 9 called is used. The light detecting element 9 outputs an electric signal that can determine the position of the light spot formed on the light receiving surface. According to this, when the measuring object 18 is displaced in the direction indicated by the arrow in FIG. 5, the position of the light spot on the photodetector changes with this displacement, and the ratio of the relative position of the light spot is changed. A proportional electric signal is output from output terminals at both ends of the photodetector. By calculating and correcting this electric signal, the position of the object to be measured can be determined, and the displacement can be obtained. Specifically, as shown in FIG.
With the displacement from 1 to a2, the position of the light spot on the light position detector 17 arranged obliquely with respect to the optical axis (center of the light beam) from the imaging lens 23 moves from b1 to b2. I do.

It should be noted that there is a technique for obtaining a focused image known as the Scheimpflug condition in the technical field of photo measurement (photo measurement method, November 1, 1977). , Published by Kyoritsu Publishing Co., Ltd.).
As is clear from this condition, in the optical displacement measuring device of the present invention, the angle of incidence of light on the light receiving surface of the optical position detector decreases as the angle of incidence of light on the object to be measured decreases. Must be bigger. In particular, as a condition for appropriately maintaining the amount of light incident on the photodetector and obtaining a state in which the aberration of the imaging optical system is reduced, the optical displacement measuring apparatus employing the optical system as shown in FIG. The incident angle of the light incident on the disposed light position detector was approximately 60 degrees or less.

However, when an optical system as shown in FIG. 6 disclosed in Japanese Patent Application No. 5-109885 is adopted, in other words, when an optical system that shares the functions of a light projecting lens and a light receiving lens is adopted, the numerical aperture of the lens is reduced. Due to the limitation, the incident angle of light incident on the optical position detector is about 80 degrees.

[0007]

As described above, the incidence angle of light incident on the optical position detector is set to about 80 degrees due to the necessity of the optical system.
The aberration of the optical system when transmitting through the surface of the light-receiving element 7, that is, the coating material 11 covering the light-detecting element 9, was increased, and it was difficult to focus on the whole, and the detection accuracy was poor in the part where the light was not focused. In addition, when the incident angle increases, most of the light is emitted from the light position detector 17 as shown in FIG.
Then, the light was reflected on the surface of the photodetector 9 and the light quantity for forming a light spot on the photodetector 9 could not be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an optical displacement measuring device capable of measuring displacement of an object to be measured with high accuracy.

[0009]

According to the optical displacement measuring apparatus of the present invention, a light source irradiates a measuring object with light, and reflected light from the illuminated measuring object is received by a light detecting element. The displacement of the measurement object is measured by calculating the output value from the detection element. At this time, in order to achieve the above object, a point to be noted is that the incident angle is large (for example, 80 degrees).
Light was allowed to form a spot on the photodetector.
That is, a light-transmitting member is provided so as to cover the light-receiving surface of the light-detecting element, and the light-transmitting member has at least an incident surface for receiving reflected light forming a part of a spherical shape centering on the light-detecting element. In this configuration, substantially all of the reflected light that is perpendicularly incident on the incident surface of the light transmitting member is incident on the photodetector.

[0010]

The light from the light source is collimated by a collimating lens, condensed through an objective lens, and radiated onto a measurement object. The light condensed by the objective lens irradiates the measurement object at an angle with the optical axis of the lens. The irradiated light is reflected from the object to be measured, and the reflected light is guided to the imaging lens as a parallel light beam through the objective lens. The parallel light beam is condensed by the imaging lens and forms an image of a spot on the light detection element via a light transmitting member covering the light detection element. Since the light incident surface of the light transmitting member is formed as a spherical surface centering on the light detecting element of the light position detector, substantially all light incident from the normal direction to the incident surface is light. The light is focused on the detection element. Therefore, light having a large incident angle with respect to the light detecting element can reach the light detecting element without being reflected by the surface.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. The light emitted from the light source 1 is converted into a parallel light beam by the collimating lens 2, the direction is changed by the partial mirror 3, and the energy center of the light is incident off the optical axis (center axis) of the objective lens 4. . An alternate long and short dash line indicates the optical axis of the objective lens 4, and an alternate long and two short dash line indicates the energy center of the incident light beam. As a result, the light beam traveling from the objective lens 4 toward the measurement object 5 is emitted at an angle θ with the optical axis of the objective lens 4. When the surface of the object to be measured is placed in accordance with the light spot of the irradiated light, the reflected light is
The light is emitted as a parallel light beam from the lens and guided to the imaging lens 6.

The reflected light is condensed by the imaging lens 6,
An image of the light spot is formed on the light detecting element 9 of the light position detector 7. In the light position detector 7, a light transmissive member 8 is formed so as to cover the light detection element 9 (for example, a material is integrally formed so as to cover and cover the light detection element 9 with an acrylic resin). The light incident surface of the light transmissive member 8 is formed into a spherical surface centered on the light detecting element 9 of the light position detector 7 (strictly speaking, centered on the center of the light receiving surface of the light detecting element 9). Therefore, substantially all the light incident on the incident surface from the normal direction is converged on the photodetector 9. Therefore, light having a large incident angle with respect to the light detecting element 9 can reach the light detecting element 9 without being reflected by the member covering the light detecting element 9, that is, the surface of the light transmitting member 8.

Next, FIGS. 2 and 3 show a second embodiment of the optical position detector 7. FIG. The shape of the light transmissive member 8 covering the light detecting element 9 of the light position detector 7 is formed in a spherical shape with the light detecting element 9 as a center, but formed only in a range where light from the imaging lens 6 is incident. It is sufficient that the unnecessary portions are cut as shown in FIGS. 2 and 3, and the function is sufficiently satisfied.

FIG. 4 shows another embodiment of the optical position detector 7. In this embodiment, a commercially available optical position detector 7 is modified and used. In general, the configuration of the light position detector 7 is such that a light detecting element 9 is mounted on a base 10 and is fixed by a light transmitting coating material 11 also serving as a protective material. On the upper surface of the coating material 11, a light-transmitting member 8 formed in a spherical shape centering on the light detecting element 9 is bonded to an adhesive 1 made of a material having substantially the same refractive index as the coating material 11.
Fix using 2. Thereby, it has the same performance as the case where the light transmitting member 8 formed of the same material is used, and light having a large incident angle with respect to the light detecting element 9 is not reflected on the surface. The light detection element 9 can be reached. The spherical light-transmissive member 8 is formed by molding or cutting, but may be a material that is cleaved from a massive material.

[0015]

According to the present invention, the light receiving surface of the light detecting element of the light position detector is covered with the light transmitting member, and the light (reflected light from the object to be measured for measuring the displacement) is reflected on the light transmitting member. )
Of the light position detector forms a spherical surface centered on the light detecting element of the light position detector, so that substantially all light incident from the normal direction to the incident surface is collected on the light detecting element. I made it. Accordingly, light having a large incident angle with respect to the light detecting element can reach the light detecting element without being reflected by the surface.
5. It has a configuration in which the light projecting lens and the light receiving lens are integrated into one objective lens as disclosed in No. 5, and enables image formation without aberration even in a light displacement measuring device that requires a high incident angle with respect to the light detecting element. This made it possible to measure displacement with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical system of an optical displacement measuring device.

FIG. 2 is a plan view showing an optical position detector.

FIG. 3 is a front view showing an optical position detector.

FIG. 4 is a diagram showing another embodiment of the optical position detector.

FIG. 5 is a diagram showing a conventional example of an optical displacement measuring device.

FIG. 6 is a diagram showing a conventional example of an optical displacement measuring device.

FIG. 7 is a diagram showing a conventional example of an optical position detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Collimating lens, 3 ... Partial mirror, 4 ... Objective lens, 5 ... Measurement object, 6 ... Imaging lens, 7 ... Optical position detector, 8 ... Light transmissive member, 9 ... Light detection element , 10 ... Base, 11 ... Coating material, 12 ... Adhesive,

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-57914 (JP, A) JP-A-62-126376 (JP, A) JP-A-61-265744 (JP, A) JP-A-62 69111 (JP, A) JP-A-7-208918 (JP, A) JP-A-6-300519 (JP, A) JP-A-2-17708 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01C 3/00-3/32 G02B 7/28-7/40 G03B 13/32-13/36

Claims (1)

(57) [Claims] 1. A light source (1) for irradiating light to a measurement object (5), and reflected light from the measurement object irradiated with light is obliquely reflected.
And a PSD (9) arranged to receive the PS.
An optical displacement measuring device for measuring an amount of displacement of the object to be measured by calculating an output value from D , comprising: a light transmitting member (8) covering a light receiving surface of the PSD ;
The light transmitting member forms a part of a spherical incident surface for receiving at least a reflected light is centered on the center of the PSD, the any of the reflected light incident perpendicular to the incidence plane An optical displacement measuring device , wherein a spot is formed on a PSD .