JPS63263411A - Optical distance detector - Google Patents

Abstract

PURPOSE:To reduce the size of an image formation optical system for observation by using a mirror for the image formation optical system and forming an image of a light beam from a bright point formed by light beam projection on the mirror for image formation on the same side with the bright point. CONSTITUTION:The light beam B from a light beam projecting means S form the bright point T on the surface of an object O. The light from this bright point T forms its image on the observation surface through the mirror M for image formation. When the object moves in an optical axis direction Z', i.e. toward and object O', the image of the bright point T' is formed at I' through the mirror M. An image position detecting means P arranged on the observation surface detects the image position of the bright point to detect the distance in the optical axis direction. Consequently, the bright point and image are on the same side about the mirror M, so the degree of freedom of the constitution of a detection optical system is increased and the optical distance detector is reduced in size.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical distance detection device that non-contactly measures distance information in the projection direction of a light beam, and is particularly applicable to a three-dimensional shape measuring machine. The present invention relates to an optical distance detection device for realizing a small tip stylus that detects the distance to the surface of an object with high accuracy in a non-contact manner.

[Conventional technology]

As a distance detection device for a three-dimensional shape measuring machine, a contact type distance detection device is mostly used.

In order to improve the shape measurement and measurement speed of objects that would otherwise be deformed or destroyed with contact-type distance detection devices,
In recent years, a bright spot is generated by projecting a light beam onto the surface of an object, which is observed from different directions using an observation system using an imaging lens, and based on the principle of triangulation, researchers have been able to determine the direction in which the light beam is projected. Optical distance detection devices that determine distance have been attempted.

FIG. 3 shows a typical configuration example of this conventional optical distance detection device using light beam projection. The light beam B from the light beam projection means S produces a bright spot T on the surface of the object O. The light from this bright spot is projected by the observation lens L onto the image position detection means P disposed on the observation surface, forming an image (2). When the position Z of the object in the direction of the light beam projection axis moves to Z', the bright spot T also moves to T'
The image I on the observation surface also moves to T'.

The position of the image l on the observation surface corresponds to the distance Z of the object in the direction of the light beam projection axis. Therefore, by detecting the position of the image I on the observation surface using the image position detection element P, the distance to the object surface can be determined.

[Problem that the invention seeks to solve]

In this configuration, the bright spot and the image are on opposite sides of the lens, and the optical distance detection using this method is difficult because the image position detection optical system becomes long in the lens optical axis direction. This has been one of the difficulties in miniaturizing the device. Furthermore, in an imaging system using a lens, it is necessary to use a combination lens or the like in order to eliminate chromatic aberration of the lens, which is disadvantageous in terms of miniaturizing the device. In order to avoid the effects of chromatic aberration, attempts have been made to use monochromatic light from a laser diode or the like, but in that case, it is also necessary to consider the effects of speckles and the like.

[Means for solving problems]

In order to solve the above problems, the present invention is characterized in that a mirror is used in the imaging system of the imaging optical system so that the object and its image are on the same side with respect to the imaging system. shall be.

[For production]

Since a mirror is used in the imaging optical system for observation, the light rays from the bright spot generated by the light beam projection are reflected by the imaging mirror, and the light rays from the bright spot are reflected on the same side of the imaging mirror as the bright spot. is imaged.

The image formation condition is exactly the same as in the case of a lens. By arranging an image position detection element at this position and detecting the image position of the bright spot, the light beam can be The distance in the projection direction can be determined.

C Effects of the invention] According to the invention, since the object and the image can be placed on the same side with respect to the imaging system, the length of the imaging system in the optical axis direction can basically be shortened. , which is advantageous for downsizing the optical system. In addition, since image formation is determined only by reflection on the surface of the mirror, there is basically no need to consider spatial refraction like with lenses, and its design is easy, and there is no need to consider chromatic aberration etc. do not have. Moreover, the space it occupies can be made into a significantly limited area, which increases the degree of freedom in designing the optical distance detector and facilitates miniaturization.

〔Example〕

FIG. 1 shows the basic configuration of an optical distance detection device based on the present invention. Light beam B from light beam projection means S
generates a bright spot T on the surface of object 0. This bright spot T
The light from the mirror forms a bright spot image I on the observation surface by an imaging mirror M. When the object moves in the optical axis direction Z', a bright spot T
The image of ' is focused on T' by an imaging mirror M. The distance in the optical axis direction can be detected by detecting the image position of the bright spot by the image position detecting means P arranged on the observation surface.

Since the bright spot and the image can be on the same side with respect to the imaging mirror, there is a degree of freedom in the configuration of the detection optical system that is different from when using a conventional imaging lens, and it is especially useful for optical distance detection devices. This is effective in downsizing. Furthermore, since the problem of chromatic aberration in the imaging system is eliminated, the imaging conditions do not change even if projection lights of different wavelengths are used. Therefore, no problem occurs even if the measurement is performed using white light or by varying the wavelength of the light source.

There is a possibility that the speckle problem that occurs when a monochromatic laser diode is used in the Ju-To method can be avoided by varying the wavelength of the light source.

FIG. 2 shows an embodiment in which the imaging mirror has a rotationally symmetrical shape. In this case, a bright spot T generated on the surface of the object 0 by the light beam B projected in the rotationally symmetrical axis direction is imaged onto the observation surface by the rotationally symmetrical imaging mirror M, forming an annular image I. do. The position I of this toric image I! (radius) corresponds to the distance in the light beam projection direction, and by detecting the radial position of the annular image I with the image position detection element P on the observation surface, the light beam projection on the surface of the target object 0 is detected. You can find the distance in the opposite direction. Note that by arranging a plurality of image position detection elements on the observation plane as shown in the figure, the influence of speckles and the inclination of the object plane can be avoided. It becomes possible to reduce measurement errors.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of the configuration of an optical distance detection device using a one-zoom mirror according to the present invention, and FIG.
FIG. 3 is a perspective view showing a configuration example of an optical distance detection device using a rotationally symmetrical imaging mirror; FIG. 3 is a plan view showing a typical configuration example of an optical distance detection device using a conventional lens imaging system. figure. S...Light source, B...Light beam, 0. o'...symmetrical object, T, T'... bright spot generated on the object surface,
z, z'...distance in the light beam projection direction, L...imaging lens, M...imaging mirror, 1.1'...bright spot image on observation surface, P...・Image position detection element

Claims (3)

[Claims] (1) Project a light beam onto the surface of the target object to generate a bright spot, project and image the generated bright spot onto an observation surface using an imaging optical system, and create a bright spot image on this observation surface. An optical distance detection device of the type that detects a position and acquires distance information to a target object surface based on the principle of triangulation, characterized in that an imaging mirror is used in the imaging optical system. Optical distance detection device. (2) The optical distance detection device according to claim (1), wherein the imaging mirror has a conic section. (3) The optical distance detection device according to claim (1), wherein the imaging mirror has a rotationally symmetrical shape.