JPS6137563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that irradiates an object with light and detects the reflected light to measure the distance to the object.

Most conventional distance measuring devices install optical parts such as corner cubes and mirrors on the target, and then irradiate light onto the target and measure the time it takes for it to be reflected, or use interference. It was hot. Therefore, it is limited to measurement at one point on the target, and is not suitable for multi-point measurement such as obtaining a profile of the target.It is also suitable for relatively long-distance measurements of 50 m or more or relatively short distances of 5 m or less. It is commonly used.

An object of the present invention is to provide a new distance measuring device that can be used for measuring medium distances of about 5 m to 50 m and does not require any additions to the object.

For this purpose, in the present invention, as shown in FIG.
It consists of a light projector A, a light modulator B, an imager C, an image difference circuit D, and an optical image position detection circuit E. The principle is, for example, using a laser beam, a laser beam from a projector A is turned on and off by an optical modulator B and projected onto a target 4, and an image of the light turning on and off on the target is captured by an imager C. Then, from this video signal, a video difference circuit D calculates the amount of change due to the on/off of the optical image, and from this change position, the position of the optical image is determined by the optical image position detection circuit E.
It is detected by Furthermore, the video differential circuit D
As shown in Figure 2, or a memory circuit using memory, shift registers, delay lines, etc.
d ₁ and an arithmetic circuit d ₂ , which outputs the current video signal 201.
and the past video signal 2 stored in the memory circuit _d1
02 is determined by the arithmetic circuit _d2 in synchronization with the light on/off control signal 200.

According to the present invention, even if the light reflectance of the target is low, it can be configured to integrate the changing light amount, and the distance to the target can be measured relatively stably. Furthermore, by moving this device, the profile of the distance to the target can be determined, so it can be used, for example, when mounted on a crane to determine the number of stacks of containers or the like, or for crane positioning.

The present invention will be explained in detail below with reference to the drawings. FIG. 3 schematically shows an embodiment of the present invention. In the figure, beads 2 from laser light source 1
is projected onto an object 4 via an optical shutter 3, forming an optical image 5 thereon. This light image 5 is captured by a plurality of photoelectric conversion elements (sensors) 8 via an optical filter 6 and lens 7 that selectively transmit the light in accordance with the wavelength characteristics of the laser light source. This sensor 8
Although an imaging device capable of two-dimensional scanning such as a TV camera may be used, a one-dimensional scanning sensor array using a CCD or a photodiode array can also produce sufficient effects.

When configured in this way, depending on the opening and closing of the optical shutter 3, the sensor 8 captures target images when the beam is irradiated and when the beam is not irradiated. Although this optical shutter 3 can be realized mechanically, a solid-state optical shutter using crystals such as cadrinium molybdate is more suitable. For example, by electrically controlling the opening and closing of this optical shutter alternately, it is possible to capture target images with and without the beam, and by subtracting them, the irradiated area of the beam is emphasized. By repeating this several times, the area of the beam irradiated onto the sensor 8 becomes clear. If this is added multiple times, it will be further emphasized by the integral effect and the beam image will become clearer. This beam image position is
Since it is measured as a position on the sensor 8, the distance to the target can be calculated based on the principle of triangulation by taking into account the direction of the laser beam and the direction of the sensor optical system.

FIG. 4 shows an example of the configuration of a detection circuit system according to the present invention. The video signal 9 from the one-dimensional sensor 8 is
The signal 11 is sequentially converted from analog to digital by an AD converter 10, and the resulting signal 11 is led to a subtracter 12 and sequentially stored in a memory 13 configured, for example, in a shift register type. The subtracter 12 successively subtracts the signal 11 and the previously stored output signal 14 from the memory 13.

On the other hand, the timing oscillator 15 generates a scanning clock a ₁ for the sensor array, and based on this signal, generates a pulse signal a ₂ that turns on and off in units of scanning time of the sensor array, which opens and closes the aforementioned optical shutter 3. A video signal containing the beam image and a video signal not containing the beam image are alternately generated. Therefore, these two types of video signals appear alternately in the digitized video signals 11 and 14 in accordance with the scanning of the optical sensor. Therefore, when the output 16 of the subtracter 12 is inverted by the sign inverter 17 using the pulse signal a ₂ , the output 18 always outputs an image obtained by subtracting the image with the beam image. Therefore, this signal is led to the adder 19, where it is added to the contents stored in another shift register type memory 20, and the result is stored in the memory 20 again, and the number of additions is determined by the pulse signal _a2 . If the counter 21 is controlled via the gate 22, the output up to the predetermined number of additions can be obtained as the output 23. Control signal a ₃ at this time
is a pulse signal that is output every predetermined number of times,
This saves the contents of the memory 20 to the initial difference image 18.
Update to. At this time, if the output 18 is divided into a noise component and a signal component due to the irradiated light, the Gaussian noise that follows the Gaussian distribution is the largest among the noise components.For example, after M times of simple addition and integration, this noise component is multiplied by √ However, the signal component is multiplied by M, and the signal-to-noise ratio (S/N) is improved by a factor of √. The added video signal 23 is compared with a predetermined threshold value 24 by a comparator 25, and when the output 23 is greater than the threshold value 24, the logical output from the comparator becomes "1". Therefore, the final scanning signal _A4 is used to control the gate 26 so that this pattern of "1" and "0" is output only when adding a predetermined number of times, and the output is led to the arithmetic circuit 27 and connected. By performing processing such as determining the center position of the "1" pattern, the position of the beam image on the sensor can be determined, and if necessary, the distance to the target can be determined from that position information using the principle of triangulation. It can also be converted to . Therefore, it is more convenient to implement this arithmetic circuit 27 with a microcomputer. In some cases, the above-mentioned shift register type memories 13, 20, subtracter 1
2. Functions such as adder 19 and comparator 25 can also be replaced by this microcomputer.

FIG. 5 shows a time chart of the control signals explained above. The scan clock _a1 is the scan clock of the sensor array and repeats one scan of the sensor.
In addition, the scanning signal _a2 is a signal that repeats on and off for each scanning period of the sensor, the initial scanning signal _a3 is a signal that is turned on during the first scanning period, and the final scanning signal _a4 is a signal that is turned on during the last scanning period. This is the signal that turns on.

As described above, the present invention does not install any additional objects on the object, and instead irradiates light directly onto the object to create a light image and capture the image. It is characterized by the fact that it can be reasonably determined from the difference between the captured images.

If the position of the light image on the imaging surface is known in this way, the position of the object in three-dimensional space can be calculated from the relationship with the previously known irradiation angle of light. Furthermore, since the present invention is a method that integrates the difference between images and improves the S/N to emphasize only the reflected light at the irradiated position, even if the reflectance of the target object is low or the irradiated light is weak, This makes it easier to detect the position of the sensor, making it possible to perform measurements even in harsh environments, such as outdoors in all weather conditions, where the illuminance changes rapidly, or in complex spaces with unknown objects. Therefore, in the automatic picking and unloading of a container crane, the number of stacks can be obtained using the distance measuring device of the present invention, which is extremely useful for industrial use, as it is useful for automating and speeding up cranes.

Note that the circuit used to explain the present invention is one embodiment, and the circuit used in the analog-to-digital converter 10 in FIG.
is for performing subsequent processing with digital signals, and is unnecessary in the case of analog signal processing, and the storage circuits 13 and 20 are analog signal memories or shift registers, the subtracter 17, and the adder 19 are analog signals. It is sufficient to use a subtractor and an adder for signals. Furthermore, as can be easily imagined, an equivalent function can be obtained by using a two-dimensional imaging device such as a TV camera in place of the one-dimensional sensor array 8. In this case, for example, the laser beam is split and projected as three beams with slightly different angles, and each reflected beam is reflected on the TV.
By separately capturing images on three scanning lines of the camera and processing the video signals on each scanning line in a similar manner to the method described above, it is also possible to obtain a measuring device with a deep distance to the target. Become.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the present invention, Figure 2 is a diagram of the principle of a video differential circuit, Figure 3 is a schematic diagram of the principle of a specific example, Figure 4 is a detailed circuit configuration diagram, and Figure 5 is circuit control. This is a time chart of the signal.

Claims (1)

[Scope of Claims] 1. Irradiation means that irradiates a target object with laser light intermittently at a predetermined period, and a plurality of photoelectric conversion elements captures reflected light from the target object at the predetermined period to generate an image. an imaging means for sequentially transmitting signals, and an image for detecting an image area of the reflected light imaged by the plurality of photoelectric conversion elements by detecting a change in the image signal due to the intermittent irradiation of the laser beam. A distance measuring device comprising an area detecting means and a means for determining a center position of the image area, and determining a distance to the target object from the center position. 2. The distance measuring device according to claim 1, wherein the video area detection means includes an integrating means for integrating changes in the video signal.