NL1040756B1 - Instrument to measure the thickness and position of contact wires. - Google Patents

Description

Title: Instrument to measure the thickness and position of contact wires.

Field of the invention

The invention refers to an instrument to measure the thickness in one dimension (y) of at least one contact wire positioned within an area extending along a second dimension (x). The instrument comprises a sensor. The instrument is exclusively used for measuring the thickness and position of contact wires of trains etc.

There are some problems to solve when looking for an instrument as indicated above: - Preferably, several contact wires lying behind each other (spread over the x-axis) have to be measured individually; - Preferably, a near by and a far off contact wire (or an wire moving along the x-axis) has to be projected to the sensor with the same magnification, so that their projections to the sensor reflect their real sizes (in the direction of the y-axis) without any need for scaling; - Preferably, the projection of the contact wire to the sensor is sharp at any position of the contact wire on the x-axis without any need for adjusting the projection; - Preferably, if the contact wires to be measured are illuminated, solely light which is reflected by the contact wires must be detected, excluding light which is reflected by e.g. the contact wire's background; - Preferably, in operation the relevant instrument components are mounted underneath a pantograph (used in trains etc.).

Summary of the invention

The present invention aims to fill the needs as outlined above. According to the invention an instrument is presented for measuring the size in one direction (y) of at least one contact wire located at or moving along a predetermined straight line (x), using optical transfer means and a sensor which is sensitive for light which is reflected by said at least one contact wire, comprises one or any combination of next provisions: - To be capable to detect several contact wires lying behind each other (spread over the x-axis) individually it is preferred that the optical path between the contact wire (or wires) and the sensor is provided such that, in the plane through the x-axis, the y-axis and the sensor, the (collimated) chief rays between the contact wire and the sensor extend under an angle to the y-axis which is substantially unequal to zero: in other words, the chief rays from the contact wire diverge from the x-axis. - To provide that a near by and a far off contact wire (or a contact wire moving along the x-axis) will be projected to the sensor always having the same magnification, so that their projections to the sensor reflect their real sizes (in the direction of the y-axis) without any need for scaling, it is preferred that optical path between the sensor and the contact wire is a telecentric optical path. Such a telecentric optical path is defined as a path, comprising one or more lenses and/or mirrors, causing that the chief rays for all points across the contact wire or image are collimated. For example, telecentricity occurs when the chief rays are parallel to the optical axis, in object and/or image space. Another way of describing telecentricity is to state that the entrance pupil and/or exit pupil of the system is located at infinity. - To provide that the projection of the contact wire to the sensor is sharp at any position of the contact wire on the x-axis, it is preferred to apply the "Scheimpflug"-principle. The Scheimpflug principle is a geometric rule that describes the orientation of the plane of focus of an optical system (such as a camera) when the lens plane is not parallel to the image plane. It is commonly applied to the use of camera movements on a view camera. The principle is named after Austrian army captain Theodor Scheimpflug, who used it in devising a systematic method and apparatus for correcting perspective distortion in aerial photographs (GB Patent No. 1196 and GB Patent No. 1139). - It may be preferred that the contact wire the thickness of which has to be measured, is illuminated by a source of visible or invisible (e.g. infrared or ultraviolet) light. To achieve that solely the light reflected by the contact wire(s) is detected by the sensor, excluding light which may reflected by e.g. the contact wire's background or environment, the illumination is transferred via an optical path exclusively lying within a first plane, while the reflected light is transferred via a path which exclusively lies within a second plane, where both planes are placed such that their intersection line coincides with said predetermined straight line (x) at which said at least one contact wire is located or moving along. - It may be preferred that in operation the instrument is mounted underneath a pantograph (used in trains etc.) which has a contact strip on which the contact wires move.

Below an illustrated exemplary embodiment of the invention will be discussed.

Exemplary Embodiment

Figure 1 shows schematically an exemplary embodiment of a preferred instrument according to the invention.

Figure 2 shows schematically the application of the configuration shown in figure 1 for measuring the thickness of contact wires of trains etc.

In figure 1 an instrument is presented for measuring the size in one direction y of at least one object 1 located at any position of or moving along a predetermined straight line x, using optical transfer means and a sensor 2 which is sensitive for light which is reflected by object 1. Figure 1 shows schematically the preferred provisions as outlined above.

To provide that a near by object 1 and a far off object 1' (or an object 1 moving along the x-axis) will be projected to the sensor 2 always having the same magnification, so that their projections to the sensor 2 reflect their real sizes (in the direction of the y-axis) without any need for scaling (e.g. in additional processing means), in figure 1 the optical path between the sensor 2 and the object 1 is a telecentric optical path. Such a telecentric optical path is defined as a path, comprising one or more lenses and/or mirrors, causing that the chief rays for all points across the object or image are collimated. As can be seen in figure 1, the telecentricity is achieved by providing, by means of the curved shape of a mirror 4 and/or the features of an objective 5, that the chief rays 6 are parallel to each other and the optical axis 7.

To be capable to detect several objects (e.g. 1 and 1') lying behind each other (spread over the x-axis) individually in figure 1 the optical path between the objects 1, 1' and the sensor 2 is provided such that, in the (detection) plane 3 through the x-axis, the y-axis and the sensor 2, the (collimated) chief rays 6 between the objects 1, 1' and the sensor extend under angles a, a' to the x-axis which angles a, a' are substantially unequal to zero: in other words, the chief rays from the object diverge under an angle (viz. angels a, a') from the x-axis.

To provide that the projection of the object 1 to the sensor 2 is sharp at any position of the object on the x-axis, the "Scheimpflug"-principle has been applied in the configuration of figure 1: the detection plane of sensor 2 is not perpendicular to the optical axis 7.

In figure 1 the objects 1, 1' the height of which has to be measured, is illuminated by a source of visible or invisible (e.g. infrared or ultraviolet) light, formed by a laser 8. To achieve that solely the light reflected by the object(s) is detected by the sensor, thereby excluding light which may reflected by e.g. the object's background or environment, the illumination is transferred via an optical path 9, provided by the laser 8 and on optical slit 10, exclusively lying within an illumination plane 11. The reflected light - reflected by the illuminated object(s) 1, 1' - is transferred via a path which exclusively lies within a detection plane 3: stated more precisely, only reflections which are transferred via the (narrow) optical path lying within plane 3, will be detected by sensor 2. Both planes 3 and 11 are placed such that their intersection line coincides with the straight line x at which the objects 1, 1' are located or moving along.

By the configuration shown in figure 1 the first four aims of this invention are met: - Several objects 1, 1' lying behind each other can be measured individually; - Nearby and far-off objects 1, 1' are projected to the sensor with the same magnification; - The projections of the objects 1, 1' to the sensor are sharp at any position of the objects on the x-axis; - Solely light which is reflected by the (illuminated) objects is detected, excluding any other light.

Figure 2 shows schematically an instrument for measuring the thickness and position of contact wires of trains etc., based on the configuration as outlined in figure 1. In figure 2 the diameter of contact wires 12, 12' can be measured using the same configuration as outlined in figure 1. The complete configuration shown in figure 2 may be mounted underneath a measuring pantograph 13, mounted on an measuring rail vehicle. The (double) contact wires 12 are supported and guided by a contact strip of the instrument or pantograph 13, keeping the wires in any position along the x-axis. By the configuration shown in figure 2 - in the form of a well constructed and well accommodated measuring instrument - all aims of this invention are met.

As an example the contact wires 12 may have a square cross-section. The size Y, which is measured via the sensor 2, has a vertical component (the wire's height) and a horizontal component (the wire's width). When using rectangular or square wires, the wire wear manifests itself by a decrease of the height, which will influence directly the value of Y. When using wires having e.g. a more or less round cross-section, the value of Y may not very much, but the war mainly will influence the horizontal component: wear will flatten the underside of the wire, resulting in an increase of the horizontal surface, which - due to color and/or luminance differences compared with the remaining of the detected image.

The diameters of both contact wires 12, 12' - lying side by side (spread over the x-axis) - can be measured simultaneously due to the fact that the rays 6 from both objects diverge under an angle (a, a') from the x-axis, as has been explained in the preceding.

Claims (5)

An instrument for measuring the dimension in one direction (y) of at least one object (1,1 ') located on or displaced along a predetermined straight line (x), the instrument consisting of an image sensor (2) and a light source (8) for illuminating at least a portion of at least one object (1,1 ') in a manner that provides that the light is transmitted from the light source via a first optical path lying exclusively in a first plane ( 11), while the light reflected from at least one object (1,1 ') is transmitted through a second optical path lying exclusively in a second plane (3), with both planes (3, 11) positioned such that the common line of both planes coincides with the predetermined straight line (x) on which at least one object is located or moves along. The instrument of claim 1, wherein the second optical path, between the sensor (2) and at least one object (1,1 '), is a telecentric optical path. The instrument of claim 1, wherein the second optical path between the sensor (2) and at least one object (1,1 ') is such that the optical axis of the path from at least one object (1,1') ) deviates from the aforementioned predetermined straight line (x). The instrument of claim 1, wherein the orientation of the photosensitive face of the sensor (2) in the direction of the optical path is in accordance with the "Scheimpflug" rule. Instrument for measuring the thickness of the contact wire (12) of trains, etc. According to at least one of claims 1 to 4, wherein said contact wires are guided by a pantograph (13) and the relevant instrument components are built and assembled together under the pantograph.