JPH0457983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a laser visual sensor that obtains a distance image of an object using laser light.

BACKGROUND OF THE INVENTION Measuring the absolute distance to an object using a laser has recently attracted attention as a visual information source for remote control of robots. Such laser distance measuring devices are broadly divided into those that use trigonometry and those that measure the round trip time of light, and the latter are further divided into those that use pulsed lasers and those that modulate the intensity of continuous wave oscillation. . Continuous wave laser intensity modulation is suitable for relatively short-distance measurements such as robot vision, and for example, David Nitzan et al. 65, No. 206, 1977 (Proc. IEEE
Vol. 65, p. 206, 197). Hereinafter, a conventional intensity modulation type laser visual sensor will be explained with reference to FIG.

In FIG. 2, the output light from a laser 1 is intensity-modulated by an optical modulator 2 driven by an oscillator 3. In FIG. The intensity-modulated laser light passes through the hole in the perforated mirror 4 and is irradiated onto the object 6 by the scanner 5. Scattered light from the object 6 passes through the scanner 5, is reflected by the perforated mirror 4, and is reflected by the condenser lens 7.
The light is focused on the photodetector 8 by the . Photodetector 8 generates an information signal i. At this time, since the amplitude of the information signal i varies depending on the reflectance of the object 6 with respect to the laser beam and the distance to the object 6, the intensity of the information signal i is detected by the intensity detector 9,
If the scanner 5 scans the laser beam,
A brightness image similar to that measured by a television camera is obtained. Further, the phase of the information signal i is delayed in proportion to the distance to the object 6. Therefore, the phase detector 10
The reference signal r and information signal i from the oscillator 3 are
By measuring the phase difference between the two objects, the distance to the object can be measured. To measure the distance from the phase difference, for example, the calculation disclosed in Japanese Patent Laid-Open No. 60-216285 may be performed. A distance image can be obtained by scanning the scanner 5 with laser light.

Problems to be Solved by the Invention In the above configuration, the brightness image and the distance image are recorded and displayed separately. Generally, when displaying a distance image, a method is used in which brightness is given so that pixels closer to each other are brighter. The intensity of the information signal i detected by the photodetector 8 varies greatly depending on the material, surface condition, shape, etc. of the object 6. Accurate phase detection may not be possible for pixels with weak scattered light intensity, and random brightness will be given to these pixels. If this distance image is used as it is, it will be an image containing noise, and is not suitable for use as vision for remote control of a robot.

The present invention solves the above problem and provides a laser visual sensor that obtains a distance image that clearly displays areas where accurate position detection has not been performed.

Means for Solving the Problems In order to solve the above questions and answers, the present invention provides: a laser oscillator that emits an infrared laser beam; an optical modulator that modulates the intensity of the infrared laser beam that is emitted from the laser oscillator; A scanner that irradiates an object with an infrared laser beam whose intensity is modulated by this optical modulator in two dimensions, and receives the scattered light that is reflected from the object, and the scanner receives the light through the scanner. a photodetector for photoelectrically converting the scattered light from the target object; and a photodetector for photoelectrically converting the scattered light from the target object; a phase detector that outputs a phase delay as distance information to the object; an intensity detector that detects the intensity of the scattered light from the output of the photodetector; and a phase detector that accurately detects the phase. a level determiner that determines whether or not the phase detector has accurately detected the phase by comparing a threshold value set according to whether the intensity detector has detected the phase accurately; distance image display means for displaying distance information to the target object based on the output of the phase detector while clearly indicating the area in which the phase detector could not accurately detect the phase based on the determination result. It is something.

Effect The above structure of the present invention acts as follows. This area is determined by a region level determiner with a low optical signal intensity that allows accurate phase detection, and this region is displayed superimposed on the distance image by a display device. According to this method, areas where accurate phase detection cannot be performed can be clearly displayed,
It is useful as a visual sensor for remote control of robots.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a laser vision sensor of the present invention. The same parts as in the conventional example shown in FIG. 2 are given the same numbers, and detailed explanations will be omitted. The feature of this embodiment is that a level determiner 11 and a distance image display device 12 are installed. In the case of a pixel where the scattered light is weak, the intensity of the information signal i output from the photodetector 8 is small. The lowest level of the intensity of the information signal i at which phase detection can be accurately performed by the phase detector 10 is set, and the level judger 11 judges whether the intensity of the information signal i is below this reference level. However, in the case of a pixel with low intensity, a signal is sent to the distance image display device 12. The following several examples can be considered as display methods on the distance image display device 12.

Decrease the brightness of pixels below the reference level.

Display pixels below the reference level in color. In this case, the area is displayed as, for example, a red area in the black and white image.

A region of pixels below the reference level is surrounded by a broken line.

As described above, according to the present invention, it is possible to clearly indicate an area where accurate phase detection cannot be performed, and the present invention is useful as a visual sensor for a robot.

Effects of the Invention As described above, the present invention provides a laser visual sensor that uses a level determiner to clearly display pixels for which accurate phase detection cannot be performed because the intensity of the optical signal is small.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a laser vision sensor according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional laser vision sensor. DESCRIPTION OF SYMBOLS 1... Laser, 2... Optical modulator, 3... Oscillator, 4... Hole mirror, 5... Scanner, 6... Target, 7... Condensing lens, 8... Photodetector, 9 …
...Intensity detector, 10... Phase detector, 11... Level determiner, 12... Distance image display device.

Claims (1)

[Claims] 1. A laser oscillator that emits an infrared laser beam, an optical modulator that modulates the intensity of the infrared laser beam emitted from the laser oscillator, and an infrared laser beam that is intensity-modulated by the optical modulator. A scanner that irradiates an object two-dimensionally and receives scattered light reflected from the object by the infrared laser beam, and a light that photoelectrically converts the scattered light from the object received via the scanner. a detector; a phase detector that detects a phase lag in the output of the photodetector with respect to the output of the infrared laser beam intensity-modulated by the optical modulator, and outputs the phase lag as distance information to the object; a detector; an intensity detector that detects the intensity of the scattered light from the output of the photodetector; a threshold value set depending on whether or not the phase detector can accurately detect the phase; a level determiner that determines whether or not the phase detector has accurately detected the phase by comparing the output level; and a level determiner that determines whether or not the phase detector has accurately detected the phase by comparing the output level; A laser visual sensor comprising distance image display means for displaying distance information to the object based on the output of the phase detector while clearly indicating a region where the detection was not possible.