JPH0410569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical triangulation distance sensor used as an industrial high-precision visual sensor.

[Background technology]

In general, this type of optical triangulation type distance sensor projects light emitted from a light source 1 made of an LED, semiconductor laser, etc. onto an object to be measured X as a projection beam P, as shown in Fig. 1. A light projecting lens 2 that receives the reflected light R from the object to be measured X and a light receiving lens 3 that forms a projected light spot image S on the light receiving element 4 are arranged at a predetermined distance _l0 . death,
By detecting the position of the projected spot image S formed on the light receiving element 4, the distance l to the object to be measured X is measured. Here, the light receiving element 4 is formed by a position detection element PSD or a plurality of photodiodes, and detects the position of the projected spot image S that moves in the direction of the arrow A according to a change in the distance l of the object to be measured. The distance l to the object to be measured X is calculated based on the detection output. By the way, in this distance measurement method, the surface of the object to be measured Although the position of the spot image is detected, there is a problem in that a distance measurement error occurs depending on the reflection state of the surface of the object to be measured. In other words, as shown in Figure 2, for surface reflection of an object,
Surfaces that are close to perfect diffusion, such as paper and wood surfaces (a), surfaces with strong specular reflection components, such as metal and acrylic surfaces (b), and surfaces with only specular reflection components, such as perfect mirror surfaces (a). c), and the specular reflection component makes distance measurement impossible or increases the distance measurement error. For example, a perfect mirror surface with no diffuse reflection component as shown in Figure 2c will make distance measurement impossible, while a mirror surface with a strong specular reflection component as shown in Figure 2b will receive the specular reflection component. However, as shown in Figure 3, if the object to be measured A problem arises in that the distance error increases. Therefore, in order to solve this problem, it is sufficient to increase the distance l ₀ between the light emitting lens 2 and the light receiving lens 3, that is, the base line _length . However, there was a drawback that the overall shape of the distance sensor became large. That is, FIG. 4 is an operation explanatory diagram showing whether or not the specular reflection component R _b is received. If the specular reflection angle β (=2α) due to the inclination angle α is small, it is possible to avoid the influence of the specular reflection component. Here, in order to increase the permissible range of the inclination angle α of the object to be measured X, it is sufficient to increase the angle γ by increasing the distance l ₀ between the projection and reception lenses 2 and 3. However, if the distance l ₀ between the projection and light reception lenses 2 and 3 is increased, the case that houses the projection and light reception lenses 2 and 3 and other parts becomes larger.

[Purpose of the invention]

The present invention has been made in view of the above points, and its object is to provide a compact distance sensor that has a wide allowable range of the inclination angle of an object to be measured.

[Disclosure of the invention]

Embodiment 1 FIG. 5 shows an embodiment of the present invention. In the figure, 5 is a light shielding plate having apertures 6a and 6b made of square holes, and the inner half of the projecting and receiving lenses 2 and 3 made of convex lenses. The parts 2a and 3a, that is, the half part of the light-emitting lens 2 on the light-receiving lens 3 side and the half part of the light-receiving lens 3 on the light-emitting lens 2 side are shielded, and the outer parts 2b and 3b are used to shield the light-emitting lens 3 side. , and is adapted to receive light, and the other configurations are exactly the same as the conventional example. Note that Fig. 6a shows the case where round convex lenses are used as the projection and reception lenses 2 and 3, Fig. 6b and c show the case when square convex lenses are used, and Fig. 6c shows the case when the projection and reception lenses 2 and 3 are used. A case is shown in which light receiving means are provided on both sides of the means to detect the moving direction of the object to be measured X in a direction perpendicular to the projected light beam P.

Now, the light from the light source 1 is projected through the outer part 2b of the projection lens 2 and the aperture 6a of the light shielding plate 5, and the reflected light R of the projected beam P is reflected by the object to be measured X through the light shielding plate 5. The light is received through the aperture 6b of No. 5 and the outer portion 3b of the light receiving lens 3,
An image is formed on the light receiving element 4. At this time, since the inner parts 2a and 3a of the projection and reception lenses 2 and 3 are masked by the light shielding plate 5, the angle at which the regular reflection component enters through the light reception lens 3 (i.e., corresponds to γ)
becomes larger. Therefore, the object to _be measured
This means that the allowable range of the inclination angle α can be increased. In this case, the amount of light emitted and received is reduced by the amount masked by the light shielding plate 5, but by using a rectangular convex lens as shown in FIGS. can. In addition, in FIG. 5, the component of the light projected from the light emitting element 1 through the light projecting lens 2 that is not parallel to the optical axis of the light projecting lens 2 is caused by the holder of the optical system, the mounting part of the light source, etc. This is a stray light component that is different from the ideal light beam that is generated by reflection, and if the object to be measured is close to a mirror surface, even if this stray light component is small, it will cause a measurement error. The present invention makes it possible to reduce measurement errors caused by such stray light components.

Embodiment 2 FIG. 7 shows another embodiment, in which 7 is a case which also serves as a light shielding plate 5, and a light emitting element 1 and a light receiving element 4 are arranged inside the case 7. Reference numerals 2' and 3' designate projecting and light-receiving lenses made of convex lens halves obtained by cutting out the inner half of the convex lenses, and are fitted into apertures 6a and 6b, respectively. 8a to 8c show examples of the projecting and receiving lenses 2' and 3'. Note that the operation is the same as that of the previous embodiment, so a description thereof will be omitted.

〔Effect of the invention〕

As described above, the present invention includes a light projecting lens that projects light emitted from a light source as a projecting beam onto an object to be measured, and a light projecting spot that receives reflected light from the object to be measured and projects the light onto a light receiving element. A light-receiving lens for forming an image is placed a predetermined distance apart, and the distance to the object to be measured is measured by detecting the position of the projected light spot image formed on the light-receiving element. In the distance sensor, a convex lens with a part removed from the light receiving lens side is used as the light emitting lens, and a convex lens with a part removed from the light emitting lens side is used as the light receiving lens, This has the advantage that the allowable range of the tilt angle of the object to be measured can be increased without changing the distance between the projection and reception lenses, that is, the base line length, and a compact distance sensor can be provided.

[Brief explanation of drawings]

FIG. 1a is a schematic configuration diagram of a conventional example, FIG. 1b is a front view of the main parts of the same as above, FIGS. 2 to 4 are explanatory diagrams of the same as above, and FIG. figure,
FIGS. 6a, b, and c are front views of essential parts of the same as above, FIG. 7 is a schematic configuration diagram of another embodiment, and FIGS. 8a, b, and c are front views of essential parts of the same as above. 1 is a light source, 2 is a light projecting lens, 3 is a light receiving lens, and 4 is a light receiving element.

Claims (1)

[Claims] 1. A light projecting lens that projects the light emitted from the light source as a projecting beam onto the object to be measured, and a light receiving lens that receives the reflected light from the object to be measured and forms a projected light spot image on the light receiving element. A distance sensor that measures the distance to an object by disposing a lens at a predetermined distance and detecting the position of a projected light spot image formed on a light receiving element. A distance sensor characterized in that a convex lens with a part on the light receiving lens side removed is used as the light receiving lens, and a convex lens with a part on the light projecting lens side removed as the light receiving lens.