JPS59173707A - Tracking method of photodetector - Google Patents

Abstract

PURPOSE:To use a photodetector of a high resolution of a narrow field of view by projecting a light to the surface of an object to be measured of an unknown position, scanning the photodetector at a constant angular velocity, and detecting an optical spot of the surface of the object to be measured of the unknown position by the photodetector. CONSTITUTION:The surface of a change 2 is unknown until an optical spot is photodetected, therefore, first of all, one point is detected. Subsequently, an angle of projection is fixed to a prescribed angle alpha, and a laser light 7 is projected to the surface of the charge 2 of an unknown position. Next, the whole field of view (the whole diameter in case of an embodiment) is scanned at the prescribed angle by a photodetector 8 of a narrow field of view. In this way, when a tracking method of a photodetector of a narrow field of view of this invention is applied, a photodetector of a high resolution of a narrow field of view can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a light projector and a light receiver, and uses a triangulation method to determine the surface shape of the object to be measured by sequentially changing the light projection angle and the light reception angle. In a method of scanning and measuring, the present invention relates to a method of tracking a light receiver so that the projected light point on the surface of an object to be measured is within the field of view of the light receiver having a narrow field of view.

Conventionally, there have been few methods of accurately tracking the light receiver due to the movement of the measuring point of the light receiver with a narrow field of view. The reasons for this are (1) Accurate tracking of the photoreceiver cannot be achieved due to many technically difficult elements. (2) If the field of view of the light receiver is made wide rather than narrow, there is no need to perform difficult tracking. This is because of the following reasons.

However, with a wide field of view receiver, if the resolution per field of view is 1/100 of the total field of view, then 1/1 of the total field of view.
Although it has only a resolution of 0'O, it is assumed that the viewing angle of the narrow field receiver is 1/1O of the total field, and the resolution of the field within the narrow field is 1/100, which is the same as above. If so, it has a resolution of 7, which is 1/l 000 of the entire field of view. Therefore, when high resolution is required for the photodetector, there is a strong demand for the development of a method for Z-tracking the photodetector as the measurement point of the photodetector with a narrow field of view is moved.

Is this narrow-field optical receiver the present invention? This was done with the aim of providing a tracking method and realizing it with a high-resolution photoreceiver.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

This embodiment is applied to a blast furnace equipped with a so-called laser-type profile meter 7 that uses a laser 7 to detect the cross-sectional shape of the surface of a charge.

FIG. 1 is a schematic configuration diagram of a blast furnace equipped with the above-mentioned laser type profile meter 7, and numeral 1 in the figure shows the interior of the furnace body 1, which is filled with materials such as coke and ore. The upper part of the furnace wall 3 of the melting furnace body 1 is narrowed into a square to form an inclined surface, and a light projection window 5 is provided on this inclined surface, for example, facing each other through the blast furnace interior 7.

At this time, the distance between the light emitting window 4 and the light receiving window 5 is
It is determined by L. The light projection window 4 is for projecting laser light 7 from a laser device #6 provided outside the steel melting furnace main body 1 into the smelting furnace. On the other hand, the light-receiving window 5 is comprised of a light-receiving lens, and focuses the laser beam 7, which is diffusely reflected on the surface of the charge 2 in the steel melting furnace body 1, and guides it to a single photodetector.

A melting furnace equipped with such a laser type profile meter passes the laser beam 7 from the laser device 6 through an optical system such as a collimator (not shown), and then reflects it on a reflector 9 to irradiate the inside of the melting furnace main body l. The diffusely reflected light 7a of the laser beam 7 from the surface of the charge 2 is focused by the light receiving lens of the light receiving window 5 and detected by the light receiver 8. And said laser light? Based on the projection angle α of the diffusely reflected light 7a, the reception angle β of the diffusely reflected light 7a, and the distance @L between the light projection window 4 and the light reception window 5, a so-called triangulation method is calculated. In other words, the surface cross-sectional shape (profile) 7 of the charge is obtained.

By the way, in the case of detecting the reflected light 7a'l with the light receiver 8, in the conventional system, the entire field of view required for measuring the field of view of the light receiver 8, for example, the entire diameter in the example shown in FIG. 1, is used. Therefore, since the entire diameter is 6500 mrn in this example, if the resolution of the photodetector is 1/100, the horizontal resolution is 65 rna, which is not sufficient resolution.

On the other hand, when implementing the tracking method of a narrow-field optical receiver of the present invention, if the narrow-field of the optical receiver is 1/10 of the diameter,
The narrow field of view of the receiver is 650mm. If the receiver has the same resolution of 1/100 as above, the resolution of the horizontal position is 6.
5 mm, providing high resolution.

Furthermore, other advantages obtained by narrowing the field of view of the light receiver 8 will also be listed.

In the signal processing process of extracting effective reflected light from the signal obtained by the photoreceiver 8, the amount of signals that must be judged is large in a wide field of view, and less in a narrow field of view, and the narrow field of view is advantageous from the viewpoint of signal processing. . Particularly when correlation processing is required, the amount of processing increases in proportion to the square of the field of view, so narrowing the field of view is extremely advantageous. Furthermore, when the field of view of the light receiver 8 is made wider, the strong scattered light of the laser beam 7 described above is often captured within the χ field of view, and as a result, it is necessary to increase the dynamic range of the light receiver 8, and the effective diffused reflection light is The signal level of 7a becomes relatively small, and the S/N often deteriorates. Therefore, it is desirable that the optical receiver 8 has a narrow field of view.

In addition, when the optical receiver 8 is made to have a wide field of view, it is necessary to have a wide field of view of the entire charge 2, and the optical system of the optical receiver 8)
It is practically impossible to match the entire field of view. When narrowing the field of view of the light receiver by 8, it is possible to adjust the field of view of each bintobe to the optimum value. Therefore, not narrowing the field of view of the light receiver 8 is an extremely effective means for optimizing the optical system of the light receiver 5.

As explained above, narrowing the field of view of the optical receiver by 8
This is an indispensable technology for creating a practical photodetector7.

The method for tracking a narrow field of view optical receiver according to the present invention will be explained in order below.

The laser beam 7 shown in FIG. 1 can be projected into the blast furnace body 1 at an arbitrary projection angle α by a mirror 9, but for convenience of explanation, a mirror 9 with the rotation center A as shown in FIG. Assume that the light is projected onto the surface of the charge 2 in the furnace. It is also assumed that the light receiver 8 has a narrow field of view and performs angular tracking with point B in FIG. 2 as the center of rotation.

Note that the rotational tracking of the light receiver 8 referred to here may involve rotating the light receiver 8 around the point p'=B, but in the example in which the light is reflected once by a light receiving mirror provided inside the light receiver 8,
In some cases, the light receiving mirror performs angular tracking around point B.

Since the surface of the charge 2 in FIG. 2 is unknown until a light spot is received, it is first necessary to detect one point. In FIG. 2, the projection angle is fixed at a constant angle α, and the laser beam 7 is projected onto the surface of the charge 2 at an unknown position. Next, the narrow field of view receiver is applied at a constant angular velocity to the entire field of view (in the example, the entire diameter).
scan. At this time, the light receiver 8 having a narrow field of view can receive light at a light receiving angle β. From the projection angle α, the reception angle β, and the distance between AB (corresponding to the above), one of the 21 points is first found by triangulation.

Next, P21 to P3 and below on the surface of the charge 2 shown in Fig. 2 are measured, but using the same method used to obtain the 21 points,
Is it necessary to scan the entire field of view to measure one point?
Therefore, it is practically impossible to measure a large number of points YP in the same way.

Next, assuming that the light spot P2 on the charge 2 which is deflected by the projection angle α2 and the small angle Δα is the same as the known angle of light P1, the light spot P2 on the top of the charge 2 is the point 14 of P2' in FIG. - It can be assumed that there is.

A small angle Δα is set so that the laser beam 7 hits this 227 points.
A laser beam is projected in the direction of a projection angle α that is deflected by 7 times,
The light receiver 8 performs angle tracking so as to deflect the center of the field of view of the light receiver in the direction of the light receiving angle β of the 21 known points.

The point P2 that the laser beam 7 actually hits on the surface of the charge 2 is P2
', the light receiver 8 detects the light spot Y at a location away from the center 1 within the field of view. The true light receiving angle β is calculated based on the distance of this light spot from the center. 22 points are determined from the projection angle α, the true reception angle β, and the distance between AB by the same triangulation method as described above.

Next, when 22 points are found, P3 and below are found in the same way. Therefore, all the points to be measured can be determined using the Snake method.

Here, the size of the narrow field of view of the light receiver is indicated by the viewing angle B as shown in the third figure, and the minute angle polarization amount Δβ of the receiving angle when the projection angle is deflected by a minute angle Δα. Then, Δ
Generally, it is appropriate to select the small angle Δα so as to satisfy the relationship β×T.

It is necessary to appropriately determine Δβ, and therefore dα, depending on the degree of unevenness on the surface of the charge 2. If Δβ (and by extension Δα) is sufficiently small, the light spot will not miss the field of view of the photoreceiver 8 and tracking of the receiver will not fail, but if Δβ (and by extension Δα) is large, the surface of the charge 2 will not Depending on the degree of unevenness, tracking of the light receiver may fail and the light spot may not enter the field of view of the light receiver 8.

In this case, if the same method used to find P1 is applied, the surface of charge 2 will definitely be found, and recovery from the tracking failure of the photoreceiver will be possible.

As described above, by applying the narrow field of view optical receiver tracking method of the present invention, it is possible to use a narrow field of view and high resolution optical receiver.1. Moreover, even if tracking fails, it can be reliably recovered.

In particular, in the example applied to the laser grophylmeter described in Figure 1, the receiver could be used at a level of high resolution that was previously unachievable, and the amount of signal processing was extremely small. There were many benefits, such as being able to achieve an extremely high S/N '4 and optimizing the focus adjustment of the optical system.

Furthermore, in the present invention, the projection angle is incremented or decremented by a minute angle Δα (only the increment case was explained above, but the case of decrement is essentially the same), and the received spot is Tracking can be performed by correcting the amount of deviation from the center of the field of view of the light receiver next time, so the next measurement point is predicted and the projection angle α is calculated from the X-Y coordinates of the measurement point.

Since there is no need to calculate the light receiving angle β, it has the advantage of being able to be tracked quickly and with a simple device.

[Brief explanation of the drawing]

Is the figure an example of the present invention? To explain, FIG. 1 is a schematic configuration diagram of a blast furnace equipped with a laser type profile meter 7;
FIGS. 2 and 3 are explanatory diagrams of the photoreceiver tracking method. ■・・・Blast furnace body 2・・Charging material 3・・・
・Furnace wall 4... Light emitting window 5... Light receiving window 6... Laser device 7... Laser light 7a... Diffuse reflected light 8... Light receiver
9...Reflector A...Rotation center B of the laser beam 7...Rotation center P of the light receiver 8, , , P2. P3...-Light spot P2' l P3' + P4' on the surface of charge 2
- Predicted position α of the light spot on the surface of charge 2 - Projection angle β... Receipt angle Δα -
...Small deflection amount Δβ of the projection angle ...Small deflection amount B of the reception angle caused by the small deflection of the projection angle ...Size of the field of view of the receiver

Claims (1)

[Claims] A method that consists of a light emitter and a light receiver, and uses a triangulation method or the like to scan the surface of the object to be measured while sequentially changing the light projection angle to determine the surface shape of the object. The light angle is fixed in a certain direction, the light is projected onto the surface of the object to be measured at an unknown position, the light receiver scans at a constant angular velocity, and the light spot Y on the surface of the object to be measured at an unknown position is detected by the receiver. Then, the position of one point on the surface of the object to be measured at an unknown position is actually measured, and the unknown position of the point whose emission angle is deflected by a small angle from that one point at the known position is the same as the direction of light reception at the known position. The light spot is estimated to exist in the light receiving direction, and the light receiver is set at the center of the field of view of the light receiver in the light receiving direction of the known position. From the angle of light emission and the angle of light reception,
A photoreceptor tracking method characterized by detecting the position of a point that is a minute distance away, and sequentially detecting the position of an unknown point that is further a minute distance away from the newly detected known position.