DE2232289B2

DE2232289B2 - Optical speed measuring device

Info

Publication number: DE2232289B2
Application number: DE19722232289
Authority: DE
Inventors: Ivor Renton Brentwood Essex Baxter (Grossbritannien)
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1971-07-01
Filing date: 1972-06-30
Publication date: 1974-04-18
Also published as: DE2232289A1; FR2143950A1; FR2143950B1; AU464686B2; CH558942A; GB1348050A; SE376661B; AU4397072A

Description

Fig. 1 den prinzipiellen Aufhau einer erfindungsgemäßen Vorrichtung mit einer nur einen einzigen Schlitz enthaltenden Blende,Fig. 1 shows the basic structure of an inventive Device with a diaphragm containing only a single slit,

Fig.2 den Aufbau mit einer Blende, die mehrere Schlitze enthält,Fig.2 shows the structure with a diaphragm, the several Contains slots,

F i g. 3 den Aufbau mit einem zusätzlichen kollimierenden Spiegel.F i g. 3 the structure with an additional collimating Mirrors.

In F i g. 1 ist eine Abbildungslinse 1 dargestellt, die eine sidi bewegende Oberfläche! auf ein optisches Gitter 3 abbildet. Zwischen der Linse 1 und dem Gitter3 befindet sich eine Blende 4, die sich in der Brennebene der Linse i erstreckt. Die Blende 4 hat einen senkrecht zur Zeichenebene verlaufenden Schlitz 5, dessen größere Achse sich parallel zu den Linien des optischen Gitters 3 erstreckt. Die kleinere Achse des Schlitzes 5 liegt symmetrisch zum Brennpunkt der Linse 1.In Fig. 1 shows an imaging lens 1 which a moving surface! on an optical one Lattice 3 maps. Between lens 1 and grating 3 there is a diaphragm 4 which extends in the focal plane of the lens i. The aperture 4 has a perpendicular to the plane of the drawing slot 5, the major axis of which is parallel to the Lines of the optical grating 3 extends. The minor axis of the slot 5 is symmetrical about the focal point the lens 1.

Bei dem in F i g. 1 dargestellten optischen System liegen alle an der Abbildung beteiligten Strahlen in einem symmetrischen Bereich um den Hauptstrahl, der durch den Brennpunkt der Linse 1 vorläuft. Der vom Objekt, d. h. von der sich bc ,vegenden Oberfläche 2, kommende Hauptstrahl ist bis zur vorderen Linsenfläche per Definition parallel zu der optischen Achse. Ein in der Objektebene B (in der Zeichnung rechts von der Linse) gelegener Objektpunkt wird in der Bildebene B (links von der Linse) abgebildet. Im dargestellten Fall liegt die Bildebene B genau in der Ebene des Gitters 3. Wenn sich der Objektpunkt nun in eine neue Objektebene A verlagert, dann wird er in einer hinter dem Gitter 3 liegenden Bildebene A abgebildet. Der Hauptstrahl läuft jedoch durch den gleichen Punkt des Gitters 3 wie vorher, und infolge der Schlitzblende 4 entsteht an dieser Stelle ein unscharfes »Bild« des Objektpunkts bzw. ein endlicher Fleck. Dieser Fleck ist jedoch symmetrisch um den Punkt, den im vorhergehenden Fall das scharfe Bild d^as Obiektpunkts eingenommen hatte, Der Fleck hat siso dieselbe Position auf dem Gitter 3 wie vorher der scharfe Bildpunkt, d. h., die eSektive Vergrößerung ist die gleiche geblieben, obwohl ein gewisser Schärfeverlust eingetreten ist. Da keine Geschwindigkeitskoniponeme in derjenigen Ebene gemessen wird, die rechtwinklig zur Bewegungsebene der Oberfläche! liegt kann der Schlitz so lang wie möglich gemacht werden, um möglichst viel Licht aufzunehmen.In the case of the FIG. 1, all of the rays involved in the image lie in a symmetrical area around the main ray which passes through the focal point of the lens 1. The main ray coming from the object, ie from the moving surface 2, is by definition parallel to the optical axis up to the front lens surface. An object point located in the object plane B (to the right of the lens in the drawing) is imaged in the image plane B (to the left of the lens). In the case shown, the image plane B lies exactly in the plane of the grid 3. If the object point is now shifted into a new object plane A , then it is imaged in an image plane A located behind the grid 3. The main ray, however, runs through the same point of the grating 3 as before, and as a result of the slit diaphragm 4, a blurred "image" of the object point or a finite spot is created at this point. This patch is, however, had taken symmetrically around the point that in the preceding case the sharp image d ^a s Obiektpunkts, the spot has siso the same position on the grid 3 as before the sharp image point, that is, the eSektive magnification has remained the same, even though a certain loss of sharpness has occurred. Since no speed constructions are measured in the plane that is perpendicular to the plane of movement of the surface! the slot can be made as long as possible to take in as much light as possible.

Das in F i g. 2 veranschaulichte optische System unterscheidet sich von demjenigen der F i g. 1 lediglich dadurch, daß die Blende 4 eine Vielzahl von oleich ausgebildeten parallelen Schlitzen 5 a, 5 b, Sc und 5 d in der Brennebene der Linse aufweist. Dadurch werden mehrere (im vorliegenden Fall 4) einzeln korrigierte Abbildungssysteme mit verschiedenen Winkeln zu der optischen Hauptachse geschaffen, wobei drei dieser Abbildungssysteme in Fig. 2 mit C. C, D. D. und E. E. gezeigt sind. Auf diese Weise entsteht ein Gesamtsystem mit größerem Gesichtsfeld als es die Anordnung r.^h F i g. 1 erlaubt. Somit können von der Preßvorrichtung vorbeiwandernde unregelmäßig helle Bereiche der beweglichen Fläche über eine längere Zeit betrachtet werden, und die Lichtausbeute wird erhöht, so daß die Signalstärke vergrößert wird.The in Fig. The optical system illustrated in FIG. 2 differs from that of FIG. 1 only in that the diaphragm 4 has a plurality of parallel slots 5 a, 5 b, Sc and 5 d in the focal plane of the lens. As a result, several (in the present case 4) individually corrected imaging systems with different angles to the main optical axis are created, three of these imaging systems being shown in FIG. 2 with C. C, DD and EE . This creates an overall system with a larger field of view than the arrangement r. ^ H F i g. 1 allowed. Thus, irregularly bright areas of the movable surface wandering past by the pressing device can be viewed for a longer period of time, and the light yield is increased, so that the signal strength is increased.

Das in F ie. 3 veranschaulichte Abbildungssystem unterscheidet'sich von demjenigen nach F i g. 2 durch die zusätzliche Verwendung eines kollimierenden Spiegels 6. Infolge dieses Spiegels werden diejenigen Oberflächenbereiche, die sich außerhalb des durch die Linse allein bestimmten Gesichtsfeldes befinden, kollimiert sesehen, wodurch eine ähnliche Wirkung erzielt wird" wie man sie bei Vergrößerung der Linsenöffnung um ein Vielfaches (beispielsweise um das Dreifache oder möglicherweisv bis um das Fünffache) erhalten würde.That in F ie. The imaging system illustrated in FIG. 3 differs from that of FIG. 2 through the additional use of a collimating mirror 6. As a result of this mirror, those Surface areas that are outside the field of view determined by the lens alone, collimated, producing an effect similar to that obtained when the lens opening is enlarged by a multiple (for example three times or possibly up to five times) would receive.

Hierzu 1 Blatt Zeichnungen1 sheet of drawings

Claims

1 2 is used. It consists of two consecutive patent claims: switched converging lenses with a common focal point, in the plane of which the diaphragm appears as a smile

1. Optical speedometer aperture is located. In the other focal plane of the dem with an optical imaging system, the lens facing away from the light 5 object is a screen, of a moving surface on which the moving surface is mapped, surface via a diaphragm onto an optical grating In order to achieve satisfactory results, must steers, behind which the moving surface through the grating is about the focal length The photodetector, which detects the amount of light, is located on the other side of the lens facing it. When the ordered is characterized, i ° movable surface is far away, then must that only one lens (1) which is outside the focal point inevitably also makes the imaging system very long wide lying moving surface (2), which is a disadvantage in many cases. Therefore by one in its opposite fuel the realization of such a system occurs point arranged slit diaphragm (4) with to the difficulties, we.m z. B. the device for Ver-grid lines parallel slot (5) in a 15 turning measurement or for speed measurement Depicts level in or near the grid level (3). Aircraft intended to be used.

2. Device according to claim 1, characterized in that the object of the invention is to provide an op that the slit diaphragm (4) is only a table speed measuring device of the introduction Contains slot (5), the center of which is to be created with the type described, in which the burn-off point the lens (1) collapses. 2o education system a broad range of ob-

3. Device according to claim 1, characterized in that object distance provides independent magnification, indicates that the slit diaphragm (4) has a multiple without the lens focal length to the distance number having parallel slots (5 Λ to 5 D). area of the object must be adapted.

4. Device according to claim 1 to 3, characterized in that this object is achieved according to the invention characterized in that at least one collimate = 5 that only one lens that is outside the focal length Heder Mirror (6) is provided. low moving surface by one arranged in its opposite focal point Slit diaphragm with parallel to the grid surfaces

Cut the slot in a plane in or near the lattice plane.

30 forms.

This principle according to the invention has the advantage that even with small focal lengths of the lens and there-

The invention relates to an optical speed with a short and easily transportable Abbilkeitsmeßvorrichtung with an optical imaging system speeds an area measurement system. the light from one moving up relative to it 35 can be sen which is at a greater distance moving surface via a diaphragm on an op- is located. In addition, the imaging system is special The grille directs, behind the one through the grille, because it only contains one lens. In the end The photodetector that detects the amount of light does not need the focal length of the lens to be related to the object distance is. to be adapted, rather the inven-

When operating such a device, the device according to the invention is still accurate The total amount of light falling on the photodetector results when the object distance is far subject to modulation, and the output limit fluctuates. When the object distance changes of the photo detector has a corresponding mo- the frequency of the projected image in relation to the relative plane, but not the magnification the moving surface. It has been found that even with improper of the optical grating is proportional. These sharp images still have a frequency at the photo frequency follows the equation: detector output can be felt, which is proportional to the speed of the object.

F = VMS, In one embodiment of the invention, the

5 ° slit diaphragm only one slit, its center with

where F is the output frequency, V the surface coincides with the focal point of the lens,
Schwmdigkeit, M the optical magnification and S to expand the field of view of the measuring device

is the spatial frequency of the grating. direction can, however, according to another orientation

The spatial frequency of the grating is a slotted diaphragm construction through the implementation of the invention fixed constant. When the 55 turn, the multiple parallel slots on output frequency in any case proportional to the points. In this embodiment too, the photo surface speed is on should be, then the detector output must be one of the speed of the beoptical Enlargement, even with changing depressed surface, proportional frequency sensations of the object (i.e., the moving bar.

Surface) remain constant. With simple optics 6o it can also be favorable if one, according to a however, this is not the case. Further development of the invention is a collimating

Under the name "telecentric systems" are always provided for mirrors. With this mirror one gets involved but optics are known in which the enlargement achieve a result similar to that obtained with enlargement With changing object distances, the lens opening can be enlarged many times over remain. From the German Auslegeschrift 65 would be.

I 523 218 is also an optical speed.

Meli device of the type described at the outset, explained by way of example with reference to drawings. There-I know in which such a telecentric system shows at