JPH0643893B2 - Distance measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distance measuring device, and in particular, can measure a distance to an arbitrary position of an object by an active method and is also applicable to measurement of a three-dimensional shape of the object. The present invention relates to a distance measuring device.

[Prior art]

Conventionally, as a method of acquiring distance information and information about a three-dimensional shape using an image sensor or the like, a light cutting method (slit method), a stereo method, and the like are known.

The light-section method is to obtain slit light on the surface of an object, observe a projection line on the surface of the object from a direction different from the projection direction, and obtain information such as the cross-sectional shape and distance of the object. In this method, the imaging side is fixed, and the three-dimensional information is acquired by imaging a plurality of images for each slit while changing the slit projection direction little by little.

In addition, the stereo method in Japanese Patent Application No. 59-44920 proposed by the applicant is such that two-dimensional image pickup elements combined with an optical system having the same image magnification are arranged apart from each other by a predetermined base line length and viewed from different directions. A three-dimensional image is obtained, and the height of each position of the object (distance to the image pickup system) is calculated from the deviation of the image information of the two images.

However, the optical cutting method has a problem that the control of the slit projection direction at the time of image capturing is troublesome and the image capturing takes time. Also,
Since three-dimensional information is obtained from a plurality of slit images, the amount of information to be processed is large, and it takes a long time to obtain the final information.

In addition, the stereo method does not require control such as slit scanning, but since the conventional method is generally the passive method, it is 2 when the object surface is smooth and has uniform brightness.
The contrast of the image obtained by one image sensor decreases,
There is a problem that distance measurement cannot be performed by comparing two images. In the case where such measurement becomes impossible, the appearance frequency is high at a short distance where the image magnification becomes large, and thus the shape, color, size, distance, etc. of the object are limited. .

[Outline of Invention]

In view of the problems of the above-mentioned conventional example, an object of the present invention is to perform accurate measurement regardless of the type of the object, and to measure the distance to an arbitrary position of the object or the three-dimensional shape of the object in a relatively short time. An object of the present invention is to provide a distance measuring device capable of obtaining information and having a wide distance measuring range.

In order to achieve the above object, a distance measuring device according to a first invention of the present application includes a plurality of optical systems arranged in parallel with an optical axis and separated by a baseline distance, and a plurality of optical systems through one of the optical systems. A light source means for irradiating the object with the pattern light flux and an image sensor for receiving an image of the pattern light flux on the object through an optical system different from the above are provided, and the pattern light flux on the object detected by the image sensor. Is a device for measuring the distance from the position of the optical image to a predetermined position of the object, wherein the light source means forms a pattern light flux by receiving light from the light source and the light source, and the light from the light source. An elliptical reflecting mirror directed to the mask, the light source is arranged outside the optical path of a light beam directed from the elliptical reflecting mirror to the mask, and the optical system is provided at a focal position of one of the elliptical reflecting mirrors. Entrance pupil The light source in the other focal position, characterized in that are respectively distribution.

Further features of the present invention will be described in the following embodiments.

〔Example〕

FIG. 1 is a schematic view of an optical system showing an embodiment of the distance measuring device according to the present invention. In the figure, reference numerals 1 and 2 denote lenses arranged at a distance of a base line, optical axes thereof are parallel to each other, and the object-side main planes of the lenses 1 and 2 are on the same plane. In this embodiment, the lenses 1 and 2 have the same focal length. 3 is a light source, and it is preferable that the light emitting portion 3'is relatively small. Image sensor comprising a CCD or the like 4, 5 objects ranging, 6 a plurality of light-transmitting portions ₆₁ in the light-shielding member the mask for pattern projection, 6 _2, ... 6 ₅ from the opening pattern is provided comprising Yes, it is arranged near the focal point of the lens 1. Further, 7 is an elliptical reflecting mirror which reflects a part of the light from the light source 3. FIG. 2 shows an example of the opening pattern of the mask 6, and as described above, a plurality of thin rectangular slit-shaped light transmitting portions 6 ₁ , 6 ₂ , 6 ₃ , ... Are arranged on the mask 6. There is. In the figure, the translucent portions 6 ₁ , 6 ₂ , ... Have an arrangement pattern that is sparse in the horizontal direction and relatively dense in the vertical direction, as indicated by the thin line AX in the horizontal direction, and as a result, in the diagonal direction. It forms a row of slits that extend. The density and arrangement of the light-transmitting parts 6 ₁ , 6 ₂ , ... May be determined according to the required measurement accuracy and the vertical and horizontal resolution of the image sensor used, and thus the structure is not limited to the above. Various patterns can be used. The density in the horizontal direction of the translucent portions 6 ₁ , 6 ₂ ... Of the mask 6 is made relatively low as shown in FIG. 2 because the optical image on the image sensor 4 depends on the distance of the object 5 as described later. This is because the position moves in the horizontal direction, so that the distance range in which detection can be performed is wide.

In the configuration shown in FIGS. 1 and 2, the light flux illuminated by the light source 3 and passing through the light transmitting portions 6 ₁ and 6 ₅ passes through the lens 1 and the object 5
The optical images are formed at the positions indicated by the symbols P ₁ and P ₂ on the target object 5 in accordance with the position of. Then, the light images on P ₁ and P ₂ pass through the lens 2 to form light images on the positions D ₁ and D ₂ on the image sensor 4, respectively.

As can be seen from the principle of the stereo method, the optical image Dn (n = 1,2 ...)
Is the distance of the reflection point, that is, the positions P ₁ and P _{2 of the} object 5.
Depending on the distance, the lens moves on a straight line (baseline direction) parallel to the arrangement direction of the lenses 1 and 2. Therefore, the distance distribution of the surface of the object 5 from the measuring device can be calculated by using the optical image Dn
It is possible to detect as the horizontal density distribution of (...). That is, by observing the output waveform of the image sensor 4 with an image processing device using a computer system or the like, the distance to the light image position (beam projection point) on the surface of the object 5 can be easily obtained by the principle of triangulation. be able to.

Now, in this embodiment, in order to expand the distance range in which distance measurement is possible, not only the depth of field of the lenses 1 and 2 is increased,
The pattern light flux with which the object 5 is irradiated is devised.
That is, in FIG. ₁ , the translucent portions 6 ₁ , 6 ₂ , 6, ₃ , 6, ₄ , 6 _{5 of the} mask 6 are shown.
Can be regarded as a point light source, and when illuminating the opening pattern of the mask 6 by a normal illumination method, the respective translucent portions 61, 62 are
The light emitted from 65 is diffused, passes through the entire pupil of the lens 1, and is directed to the object 5 via the lens 1. When the object 5 is irradiated with the pattern light flux by such a method, there is a limit to the distance measurement range that can be obtained even if the lens 1 has a large depth of field, and the aperture pattern is formed on the image sensor 4. A blurred image of the optical image is formed, which makes it difficult to detect the optical image position.

However, in the present embodiment, the light source 3 is arranged at a position away from the mask 6 and outside the optical path of the light flux reflected by the elliptical reflecting mirror 7 for directing the light from the light source 3 to the mask 6. Thus, only the light flux coming from a predetermined direction is made incident on the light transmitting portions 6 ₁ , 6 ₂ , ... 6 ₅ of the mask 6. Further, in this embodiment, the light source 3 (microscopic light emitting portion 3 ') is arranged at the first focal point of the elliptical reflecting mirror 7, and the second focal point of the elliptic reflecting mirror 7 is substantially aligned with the center of the entrance pupil of the lens 1. By
All of the plurality of pattern light fluxes obtained by the mask 6 are applied to the object 5 via the lens 1.

Further, in the conventional illumination method using an elliptical reflecting mirror used in a projector or the like, a method of increasing the amount of light hitting the mask surface by illuminating the mask with both direct light and reflected light from a light source is adopted. There is. In this case, there is a difference between the reflected light and the direct light incident on the mask. Therefore, when the object 5 is at a position deviated from the in-focus position as shown by P ₂ , there is a difference in the position where the reflected light and the direct light irradiate the object, and two points are irradiated. A difference also occurs in the light image position received by the sensor 4, which is an obstacle to detecting the light image position and measuring the object distance. Also, when the reflected light passes through the glass tube that seals the light source and illuminates the mask 6, the spread (NA) of the light flux that illuminates the opening pattern of the mask on the object 5 becomes large, and the focused point is increased. As described above, the blur amount of the opening pattern of the mask 6 that irradiates the object at the position away from the position becomes large.

On the other hand, in the arrangement shown in FIG. 1 according to the present invention, the light emitted from the light source 3 and directly illuminating the mask 6 does not enter the lens 1. Therefore, the light flux that irradiates the object with the opening pattern of the mask 6 is emitted from the light source 3 and is reflected by the elliptical reflecting mirror 7 to be only the light collected near the center of the entrance pupil of the irradiation lens 1, and the transparent portion 6 _{1 of the} mask 6 , 6 ₂ ... spread of the light beam transmitted through a point becomes its size visual angle of when a weak light emission portion of the light source 3 3 'viewed from this point was reflected in the reflecting mirror, the light transmitting unit ₃ as shown The light passing through one point becomes a light flux with a small divergence angle as shown by the solid line. The size of the blur on the position P ₂ away from the uniting focus position is d ′, which can be reduced. The small diameter of the ellipse reflector from nature to the edge of the mask 6 transparent window 5 ₅ lenses without causing the eclipse by the lens 1 so light is also directed toward the center of the entrance pupil of the lens 1 passes through the It becomes possible to do. In addition, it is possible to remove the holding member of the light source 3 and the glass sealing body from the optical path of the light beam reflected by the elliptical reflecting mirror 7 and incident on the lens 1, and it is possible to reduce unevenness in the amount of light transmitted through the light transmitting window of the mask 6. it can.

FIG. 3 shows a two-dimensional CC for a TV camera as the image sensor 4.
One scanning line when using the D sensor (fine line A in FIG. 2)
3 shows an output waveform O (corresponding to X). Here, the horizontal direction of the figure corresponds to the horizontal distance of the image sensor 4. As is apparent from the above, the output value shows the maximum value M corresponding to the light transmitting portion 6n (n = 1, 2, ...) Of the mask plate 6 which is on the same straight line as this scanning line. One translucent part 6n (n =
1,2, ...) The left and right positions of the maximum value of the output waveform appearing corresponding to (1), (2) ... are limited, and are separated from the maximum value appearance range by other light transmitting parts. (N = 1,2,
...) and the incident position of the light flux passing therethrough on the image sensor 4 can be easily associated with each other. Therefore, unlike the conventional stereo method, it is possible to reliably acquire the distance to the arbitrary position of the object 5 and the three-dimensional information without causing the inconvenience such as the inability to measure due to the contrast reduction at a short distance. Further, unlike the conventional stereo system, since the active system in which the light source is used for illumination is adopted, there is an advantage that the light amount of the light source can be small when measuring an object at a short distance. It is also possible to estimate the inclination angle of the light source position of the object from the maximum value of the image sensor output.

As described above, the distance of the surface of the object 5 from the measurement system can be measured via the two-dimensional image sensor 4.
According to the above configuration, it is possible to extract the three-dimensional information of the entire surface of the object 5 with one image reading without the need for performing mechanical scanning as in the light cutting method.

Further, since the subsequent image processing may be performed only on the distribution of the light image in the left-right direction, simple and luminous flux processing is possible.
Furthermore, according to the present embodiment, the image of the structure on the image sensor 4 can be binarized as it is, and can be output to a CRT display or a hard copy device for visual three-dimensional expression.

The distance measuring method or the 3 o'clock information processing method according to the present embodiment is a method in which a large number of stylus are pressed against an object and the object shape is perceived by a change in the amount of protrusion of the stylus from the reference plane. Since it can be performed at high speed and accurately, it can be used as a visual sensor such as a robot that requires real-time processing. In particular, this is effective in the case of perceiving the shape, posture, and the like of an object placed at a relatively short distance and performing an action such as grasping or avoiding the object.

Further, in the above description, for simplification, only the main part of the device is illustrated, and the illustration of the signal processing system, the case for blocking, etc. is omitted, but these members may be used by those skilled in the art as necessary. In the above, a suitable one may be provided as usual. Although only a single lens is shown in the optical system, an optical system including a plurality of elements or an optical system including a mirror may be used.

Furthermore, in each of the above-described embodiments, a configuration using two optical systems having the same focal length has been shown, but it is also possible to use three or more optical systems having different focal lengths if necessary. However, it is the simplest to use the same optical system having the same focal length with various aberrations.

Further, in the embodiment described above, the method of detecting and measuring the optical image of the aperture pattern having the plurality of light-transmitting portions arranged two-dimensionally by the two-dimensional image sensor such as CCD has been described. , For example, projecting an aperture pattern in which a plurality of light-transmitting portions are arranged one-dimensionally at predetermined intervals on an object, and an optical image of the aperture pattern is received by an image sensor having a sensor array in the longitudinal direction and is directed in a specific direction You may detect the shape of the target object along.

In addition, the second optical system that receives the pattern light flux from the object is
It is also possible to widen the field of view for distance measurement, and it is also possible to widen the field of view for distance measurement by translating the second optical system in parallel using a predetermined driving device.
On the contrary, the same function can be obtained even if the first optical system for irradiating the object with a plurality of pattern light beams and the light source means are moved in parallel by using a predetermined driving device.

According to the present invention, it is preferable that the pattern light flux with which the object is irradiated is a thin light beam with a spread angle as small as possible. However, since the limit mainly depends on the sensitivity of the image sensor, the sensitivity of the usable sensor And light source output, required measurement accuracy, and specifications.

Further, the magnification of the optical system and the length of the base line, that is, the distance between the first optical system and the second optical system in FIG. 1, the pitch of the transparent portion of the mask, etc., are the distance measuring ranges to be measured. It should be decided in consideration of.

The image sensor referred to in the present invention is a photodiode or CC.
All photoelectric conversion elements represented by D etc. are included.
There is no limitation on the arrangement state such as a two-dimensional array or a two-dimensional array.

Further, as shown in FIG. 1, the elliptical mirror used in the present invention may be formed by a part of the elliptic mirror, or may be formed by arranging the entire elliptic mirror as it is, and at least the second elliptic mirror may be formed. By arranging the first optical system, preferably the entrance pupil thereof, in the vicinity of the focal point, it is possible to obtain a thin light beam that is less affected by aberration. That is, it is preferable that most of the light flux emitted from the mask passes in the vicinity of the optical axis of the first optical system.

〔The invention's effect〕

As described above, the distance measuring device according to the present invention achieves short and highly accurate distance measurement by adopting the active method regardless of the type and position of the object, and uses a mask, a minute light emitting source, a mirror, or the like. A wide measuring range is provided by making the pattern light beam diameter for irradiating the object a narrow light beam.

Further, according to the present invention, it is possible to acquire three-dimensional information from a target object in a short time and with high accuracy, and it is a device suitable as a visual sensor such as a robot.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical system showing an embodiment of a distance measuring device according to the present invention. FIG. 2 is a diagram showing an example of an opening pattern of a mask. FIG. 3 is a diagram showing an output waveform of one scanning line when a CDD is used as an image sensor. 1,2 ...... lens, 3 ...... light source device, 3 _1, 3 ₂ ..., 3n ...... small emission sources, 4 ...... image sensor, 5 ...... object 6 ...... mask, 6 _1, 6 _2, …, 6n …… Transparent part, 7 …… Elliptic mirror.

Claims (1)

[Claims] 1. A plurality of optical systems arranged parallel to an optical axis and spaced from each other by a base line, a light source means for irradiating a plurality of pattern light fluxes to the object through one of the optical systems, and on the object. An image sensor for receiving an image of the patterned light flux through an optical system different from the above, and the distance from the position of the optical image of the patterned light flux on the object detected by the image sensor to a predetermined position of the object. Wherein the light source means has a light source, a mask that receives light from the light source to form a pattern light flux, and an elliptical reflecting mirror that directs the light from the light source to the mask. It is arranged outside the optical path of the light flux directed from the elliptical reflecting mirror to the mask, the entrance pupil of the optical system is located at substantially one focal position of the elliptic reflecting mirror, and the light source is located at the other focal position.
A distance measuring device characterized by being arranged respectively.