FI86112B - FOERFARANDE FOER MAETNING AV AVSTAONDSBILD. - Google Patents

Description

1 86112

METHOD OF MEASURING THE DISTANCE IMAGE

The invention relates to a method for measuring a distance image 5 as defined in the preamble of claim 1.

Distance images covering the entire image area can be taken from different objects using structured light, either by scanning the image area point by point or line by line, or by projecting the entire point or 10 line pattern as a whole at once.

When scanning, the synchronization of the reflection and measurement of each point or line ensures that the reflection angle required for the distance information is consistent with the measurement. In practice, this means that there is no risk of difficulties in interpreting the points or lines, but the angle of reflection of each point or line is reliably known. The length of the measurement time due to the scanning principle remains a problem. On the other hand, the reflection mechanism may include moving me-20 mechanisms (mirror deflection), which impairs the reliability of the equipment in demanding conditions.

Another option, reflecting the entire light pattern at a time, e.g. with the help of a lattice, eliminates the problems caused by the measurement speed. However, the problem remains the interpretation of the correspondence of the pis-25 paths or lines, i.e., which measured point or line corresponds to which reflected point or line. In complex cases, this can be an overwhelming task. On the other hand, without the correspondence information, the exact absolute distance information cannot be determined. The significance of the problem increases the farther the optical axis of the measuring camera is placed from the optical axis of the reflecting device, i.e. the more accurate the system is made and the larger the surface gradients in the object.

The object of the invention is to eliminate the above-mentioned drawbacks. In particular, it is an object of the invention to provide a measurement method which is both more accurate and faster than the current 2 86112 methods at the same time.

With regard to the features characteristic of the invention, reference is made to the claims.

The distance image measurement method 5 according to the invention uses at least two, but preferably a larger number of cameras or other similar recording devices, the optical axes of which gradually differ from the optical axis of the light source. The cameras register the reflections of the light-10 pattern reflected on the surface to be imaged at different angles in succession, i.e. the measurement takes place step by step from the recording device to the optical axis of the light source, always taking into account the image of the imaging surface given by the previous recording device.

That is, when the system includes a conventional, e.g., lattice-structured, light-reflecting mechanism and 20 cameras deviating from the optical axis of the step-reflecting device, the basic idea of the invention is to maintain dot or line pattern consistency with .

25 Since the camera on the optical axis of the reflecting device sees the reflection pattern completely unchanged, regardless of the distances of the target area, the reflection pattern appears only slightly different from the optical axis of the reflecting device to the slightly different camera. This means that depending on the distance of the reflective surface portion of each reflected point or line, the point or line will appear in the camera image within a certain cropped image area (window). Because the window is cropped, the location of a point or line in the 35 image areas can be quickly determined. Since the presence of dots or ~ Floats in their windows is also independent of each other, the calculation can also be parallelized.

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Using one camera results in a distance image with poor depth resolution due to the proximity of the optical axes of the camera and the reflecting device.

According to the invention, when a second camera different from the optical axis of the reflecting device is added to the system next to the first camera, the depth resolution can be improved. On the other hand, the distance image provided by the first camera can be used to predict which image area 10 each point or line hits. The size of this visibility window depends on the depth resolution produced by the first camera, but in any case it is again a limited image area to which the image processing algorithm can be targeted. By adding more and more cameras to the system 15 according to the invention, the depth resolution can be further improved. However, point or line consistency can be maintained at all times and no computational slowdown routines are required. The result of the method is an accurate distance image, which is determined by 20 step-by-step refinements.

The speed of computing is affected by the number of processors used. If each point or line has its own processor, a distance image is consumed. . *. for counting operations only as many counting cycles 25 as there is number of cameras.

The smaller the distance between adjacent cameras, the steeper objects with steeper surface gradients can be reliably analyzed. The controllable maximum steepness can be determined from the camera geometry and pixel resolution.

On the other hand, the properties of the surface to be analyzed can be used to determine what kind of measurement configuration is necessary. Thus, the number of cameras used and their distance from each other, i.e. the angles of their optical axes relative to each other, can always be varied as needed according to the desired image resolution and the quality of the surface to be examined.

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The invention will now be described in detail with reference to the accompanying drawing, in which Figure 1 schematically shows a measuring arrangement according to the invention, Figure 2 shows predicted calculation windows and Figure 3 shows a system diagram according to the invention.

One of the measuring arrangements according to the invention shown in Figure 1 comprises an object or surface 2 to be imaged, to which a light beam 10 is directed by a reflecting device 3. The reflecting device 3 is formed by a light source 1, which is e.g. a laser light source and the optics 5 and the lattice 6 in front thereof, whereby depending on the lattice the surface 2 to be imaged is subjected to a structured light pattern, dots, lines, etc. for cameras in corners 4.

The first camera A, whose optical axis differs least from the optical axis of the reflecting device, sees the reflection pattern only slightly changed, the second camera B slightly more changed, etc. Thus, depending on the distance of the reflecting surface of each reflective line, the line appears in the camera image 7 (Figure 2) inside. Thus, when the window is delimited, the position of the line can be · - ·. 25 image areas to set quickly.

Thus, the light pattern reflected according to the invention is measured first by camera A, then by camera B, then by camera C and thus continuing to the last camera N. Since the image given by the previous camera ·. · * 30 can always be used to interpret the image of the next camera and the angle between the optical · / · ,: axes of adjacent cameras is relatively small and thus the images given by adjacent cameras differ. relatively few from each other, there are no problems or confusion in the interpretation of the different lines of the light pattern, which would be probable if the image were taken with only one camera in the N-position of the last camera.

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Figure 3 shows a system diagram related to the invention. Cameras A, B ... N include suitable optics and a light-sensitive cell. After these, there is a vi-deomultiplexer VM, which is needed if there are fewer image memories 5 in use than cameras. After this, there are image memories KM in which the image data is stored. Processors PR1, PR2, ... PRm process the image data provided by the windows. The parent processor PR controls the operation of the entire system and contains a global memory where the necessary advance information and the resulting distance map of the object to be imaged are stored in the house. The structured light reflecting device 3 consists of a laser light source, a light structuring device such as a lattice or the like, and the necessary optics. The system-15 also has a controller KONT, which starts and stops the reflection. In addition, the above-mentioned processors are connected to each other by a communication bus, the so-called high-speed bus.

The invention has been described above by way of example with the accompanying drawings, however, various embodiments of the invention are possible within the scope of the inventive idea defined by the claims.

Claims (7)

A method of measuring a distance image, in which a light pattern project is projected from a light source (1) onto a surface (2) to be imaged, the reflected light pattern is recorded at a certain reflection angle from the reflecting device (3). optical axis and at least two, advantageously, multiple cameras or corresponding recording devices (4) 10, the optical axes of which are gradually different from the optical axis of the light source, characterized in that the interpretation of each recording device recorded in the light pattern is effected by means of the light pattern. of the preceding recording device recorded the light pattern by preserving the point or line of the new light pattern with the preceding light pattern by performing the measurement stepwise from the optical axis of the light source away in turn from one recording device to another. 20 2. A method according to claim 1, characterized in that, as projected light pattern, a dot pattern is used. 3. A method according to claim 1, characterized in that, as projected light pattern, a line pattern is used. Method according to any one of claims 1 -: 3, characterized in that the image recorded by the ·· preceding recording device (4) is used to predict the image detected by the following recording device. Method according to any of claims 1 - *: 4, characterized in that the number of the recording devices (4) and their mutual between them: *. the angles of the optical axis change according to the desired angle. 35 bought in Id's pen. Method according to any one of claims 1 to 5, characterized in that the angles between the optical axes of the recording devices (4) are changed according to the nature of the surface examined.