JPH0575050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical distance detection device that optically detects the distance to an object.

(Prior art) A marker on an object, which is generated by attaching a light emitter to the object or projecting a light beam, is projected onto the observation surface using an observation lens, and the marker on the observation surface is Optical distance detection devices that detect the position of an image and obtain distance information to an object are often used. An example of this type of optical distance detection device is shown in FIG. The illustrated equipment is RORS (Riken
This is a compact distance sensing device based on a method called Optical Range Sensing Method, in which a mirror M is placed between the observation lens L and the target object O, expanding the equivalent reference length in triangulation. It is extremely suitable for The operation of this device will be briefly explained as follows. A light beam B is projected in the optical axis direction of the observation lens to generate a marker T on the object O. By detecting the radial position of the marker image reflected by the cylindrical mirror M and projected onto the observation surface by the observation lens L using the image position detection sensor P,
The distance in the optical axis direction of the observation lens is detected. Since this device is of a fixed focus type, it has the disadvantage that the marker image on the observation surface is blurred at a distance other than a certain certain distance. In the configuration where the imaging position is uniquely determined with respect to the distance, by matching the shape of the observation surface to a surface that satisfies the optimal imaging conditions,
A good marker image can be obtained regardless of the distance to the target object. FIG. 5 is a plan view of another conventional optical distance detection device, and this FIG. 5 shows an optimal imaging plane P _F that satisfies the optimal imaging conditions. In the configurations shown in FIGS. 4 and 5, the optimal imaging plane is a conical surface, and especially in the detection device shown in FIG. 5, the optimal imaging plane P _F is given by the following equation.

a=f((1-tan ² φ)r+2d)/2(d+f.tan
φ) (1) Therefore, if the image position detection sensor is placed on this surface, the optimum imaging conditions should be satisfied.

(Problem to be Solved by the Invention) However, from the viewpoint of miniaturization and manufacturing of the distance sensor, it is not possible to form the image position detection sensor into a conical shape or arrange it on a conical surface or a polygonal pyramidal surface. It's not always easy, nor is it a good idea. Further, the optical sensor section is expected to be integrated with an amplification section, a calculation section, etc., and it is desirable that the optical sensor section be arranged in series as much as possible so that it can be used in common in several distance sensors. That is, from the viewpoint of manufacturing and serialization (versatility), it is preferable that the image position detection sensor be planar.

An object of the present invention is to provide an optical distance detection device that realizes a better imaging state while using a planarly arranged image position detection sensor in the distance sensor as described above.

(Means for Solving the Problems) The above object, as shown in Fig. 1, is a rotationally symmetrical conical surface that reflects the light from the marker T that has passed through the observation lens L before reaching the observation surface. The mirror M _C is arranged so that its axis of rotational symmetry coincides with the optical axis of the observation lens, and the image position detection sensor P is placed on a plane perpendicular to the optical axis of the observation lens L, facing in the opposite direction to the conical mirror M _C. This is achieved by placing the

Note that if the sign has a certain size, blurring may occur due to oblique incidence on the observation surface, and it is not necessarily possible to obtain an image with the least blur on the optimal imaging surface as shown by equation (1) or the like. Therefore, usually a conical mirror is placed at an angle intermediate between the angle that provides the optimum imaging condition and the plane.

Furthermore, the planar sensor or planar image position detection sensor in this specification includes both a sensor in which a plurality of sensors are arranged on a plane and a plate-like integrated sensor.

(Operations and Effects) In the present invention, even though a flat image position detection sensor is used, when the distance from the observation lens to the object becomes longer, the distance from the observation lens to the image position detection sensor increases. is configured so that the distance is shorter. Therefore, a good marker image can be obtained regardless of the distance to the target object. Further, since a flat sensor can be used as the image position detection sensor, there are no manufacturing problems, and it is also advantageous from the viewpoint of serialization (versatility).

(Example) Examples of the present invention will be described in detail below. Second
The figure is a plan view showing a preferred embodiment of the present invention. In this embodiment, a mark T is formed on the object O by the irradiation of the light beam B. The image of this marker T is reflected by a cylindrical mirror M and then passes through a lens L. The image of the marker T that has passed through the lens L is once reflected by the conical mirror M _C and then projected onto the flat image position detection sensor P. The radial position of the marker image projected on this sensor P is detected,
In this way, the distance from the observation lens L to the object is measured. In the illustrated arrangement, it is exactly the same as the image position detection sensor P being located at the optimum imaging plane P _F. In this embodiment, since the mark T is dot-shaped, the mark image on the image position detection sensor P does not become blurred regardless of the distance to the object.

Note that as the angle of the mirror approaches a plane, it approaches the case of a fixed focal point, and when it is a plane, it matches the case of a fixed focal point. In this case, although the imaging conditions are not improved, the length of the optical system in the optical axis direction can be shortened.

Figure 3 shows optical distance detection method for surface tracking.
RORST (Riken Optical Range Sensing)
FIG. 2 is a plan view when the present invention is applied to an optical distance detection device based on the Scheme for Surface Trasing. RORST is to form annular patterns T (θ ₁ ) and T (θ ₂ ) on the object surface, project this pattern onto the observation surface using an observation lens, and calculate the radial position of the image in each direction. This method detects distance information to the target object surface for each direction. Therefore, since the inclination information of the object surface can be obtained, it is extremely suitable for surface tracking in shape measurement and the like. Now, the optimal imaging plane P _F is given by equation (2), and has a conical shape as shown in FIG.

a=f(R ₀ +r(θ))/R ₀ +f・tanα(2) Here, R ₀ is the observation lens L of the projected light beam B
The passing position radius at the position α is the projection angle of the projection light beam B with respect to the optical axis of the observation lens L.

The conical mirror M _C installed according to the invention serves to bring the image position detection sensor P closer to the optimum imaging plane P _F even if the sensor P is planar.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the basic configuration of the present invention, Figure 2 is a perspective view showing the basic configuration of the present invention;
Figure 3 is a plan view representing a preferred embodiment of the invention;
The figures are a plan view showing another embodiment of the present invention, FIG. 4 is a perspective view of a conventional optical distance detection device, and FIG. 5 is a plan view of another conventional optical distance detection device. O...Object, T...Sign, L...Observation lens,
P... Image position detection sensor, M _C ... Conical mirror, B
...Light beam.

Claims (1)

[Claims] 1. The distance to the object is determined by projecting a mark on the object onto an image position detection sensor through an observation lens, and detecting the position of the mark projected onto the optical sensor. In an optical distance detection device for detecting, a rotationally symmetrical conical mirror that reflects light that has passed through the observation lens is provided, with the axis of rotational symmetry of the conical mirror coinciding with the optical axis of the observation lens, An optical distance detection device characterized in that a planar sensor is used as the image position detection sensor, and a plane on which the planar sensor is arranged is perpendicular to the optical axis of the observation lens.