NL2015307B1

NL2015307B1 - Optoelectronic Linear Position Sensor and wheel truing indicating instrument.

Info

Publication number: NL2015307B1
Application number: NL2015307A
Authority: NL
Inventors: Maria Jacobus Meeks Johannes
Original assignee: Maria Jacobus Meeks Johannes
Priority date: 2015-08-17
Filing date: 2015-08-17
Publication date: 2017-03-07

Abstract

A position sensor (3) has a housing, preferably substantially being light tight, containing a light source (16), an aperture stop (15) defining an effective aperture and a first light detector (18) arranged to receive light from the light source (16) through the aperture of the aperture stop (15). The effective aperture of the aperture stop is adjustable as a function of a deformation of a part of the position sensor (3), in particular deformation of the housing. The position sensor comprises a second light detector (17) arranged to receive light from the light source (16) substantially independent from the effective aperture of the aperture stop.

Description

Optoelectronic Linear Position Sensor and wheel truing indicating instrument

Field of the invention

This invention relates to position sensors and to the measurement of misalignment of spoked wheels for effective and accurate repair of radial or laterally un-true wheel rims resulting from damage to the wheel.

Background

Wheel truing of spoked wheels is a repetitive process in which spoke tension is gradually increased while alignment and axle centering are improved. Since the wheel is a pre-stressed elastic structure, changing tension in one spoke will cause tension changes in others. Alignment changes may occur not only at the place where the adjustment is made, but at other places as well.

Wheel truing devices are equipped with reference probes or gauge pointers to indicate the radial or lateral errors when rotating the wheel. For truing the reference probe on the truing fixture has to be adjusted so that it barely touches the side of the rim. To distinguish between left and right wobbles with respect to the average position of the rim the gap of probe to the rim must be visually observed.

Some common drawbacks of these mechanical gauge pointers are: • Changes in the distances between the pointer and the rim have to be observed visually. Very small deviations in wheel alignment are difficult to recognize and small corrections are difficult to make. • A fixed gauge pointer next to the wheel rim, being rigidly affixed to the truing stand or bicycle frame, should be set so that the pointer just barely contacts the rim. If it is prone to frequent shock from contacting an untrue section of a rotating wheel rim, than it will push on the gauge and move it inadvertently out of alignment, causing inaccurate gauging and frustrating the truing procedure. • When in physical contact with the wheel rim, these gauge pointers will damage (scratch or mar) the surface finish of wheel rims.

Some deluxe versions of truing stands may have dial indicators for measuring radial and lateral alignment. The dial indicator is a mechanical device that consists of a spindle, gears and a pointer on a dial. The gears drive the pointer on the dial and the dial is indicated by numerical readings. Although these dial gauges have a precision that exceeds the requirements of wheel truing, they can measure misalignment errors only when the wheel rotates slowly. Mechanical dial gauges are expensive instruments and susceptible to wear and tear.

Instead of a mechanical dial indicators, linear position sensors could be used. There are various other methods to measure linear position, such as: magnetostrictive, inductive, capacitive, potentiometric or incremental optical encoder sensors. Many are rotating and some are direct linear. Linear position sensors are often costly or are not entirely sustainable for rapid variations in a small range. Cheap sensors like potentiometers suffer from wear and tear. Other systems, such as LVDT's (linear speed transformers), are very accurate, but also quite costly.

Optical linear position or displacement sensors are based on the principle that an obstacle, like a plate or a vane that makes contact with the target to be measured, moves between a light source and a light detector and forms an aperture stop that controls the amount of light reaching the light detector. The amount of incident light on the light detector (e.g. photodiode or photovoltaic cell in practice) relates to the position or the displacement of the target.

For example, such position or displacement sensors are known from the patents DE202005012193-U1, DE102007012270-A1, or JPH0798210. These optical position or displacement sensors have the disadvantage that they cannot use feedback for stabilizing the light source. Their measurement principle must be independent of the intensity of the light. The irradiated surface is a measure of the position or the displacement and is measured with light sensors that are equipped with a large amount of photosensitive pixels. The number of pixels that are irradiated is a measure of the position or displacement. This type of position sensors uses photodiodes arrays or CCD-image-sensors, which deliver an output signal through comprehensive signal-conditioning electronics. This makes these position sensors complex and expensive. The designs of the patents DE202005012193 and JPH0798210 have the further disadvantage that the light source is perpendicular to the displacement direction of target. This makes the dimensions of these sensors in the execution large.

Summary

An objective of the present invention is to provide an electronic wheel truing indicating instrument that can measure and indicate the misalignment error of a spoked wheel accurately and in a cost effective manner in comparison with other alignment indicators like gauge pointers or dial gauges. By quantifying errors, a better picture of the truing task emerges, and the mean centerline can be found more easily. Displaying the error on a numerical or bar/dot graph enables the mechanic operator to know when the tolerance has been met. Another objective is a position sensor for such tool.

In view of the foregoing, an improved position sensor and an improved wheel truing instrument are provided herewith.

In an aspect, the position sensor has a housing, preferably substantially being light tight, containing a light source, an aperture stop defining an effective aperture and a first light detector arranged to receive light from the light source through the aperture of the aperture stop. The effective aperture of the aperture stop is adjustable, in particular being reversibly adjustable, as a function of a deformation of at least part of the position sensor. The position sensor comprises a second light detector arranged to receive light from the light source substantially independent from the effective aperture of the aperture stop. The first light detector serves for providing the desired position signal. The second light detector serves for providing a reference value for the first light detector signal.

The effective aperture of the aperture stop may be linearly adjustable as a function of a linear deformation of the at least part of the position sensor. However, a continuous nonlinear relation may also be suitably employed, e.g. a power-law relation, e.g. parabolic, or trigonometric relation, which facilitate analogue and analytic determining of the position to be determined, preventing digitalisation errors and -artefacts.

The second light detector may be positioned remote from the light source and between the light source and the aperture stop. A remote detector, in particular being separate objects individually mounted to or on different circuit board portions and/or wall portions of the housing, may reduce thermal influences, measurement offsets and/or other artefacts from close proximity to the light source. The housing may be divided in a first and a second compartment separated by the aperture stop, the light source and the second light detector being arranged in the first compartment and the first light detector being arranged in the second compartment.

The deformation may comprise deformation of a portion of the housing and/or shifting with respect to the housing a follower element coupled with the housing and/or the aperture stop, e.g. pressing the follower element at least partly into the housing.

The deformation may retain the relative positions of the light source, the first and second light detectors and the aperture stop.

The deformation may comprise deformation of a portion of the housing, e.g. shifting a first housing part with respect to a second housing part such as by sliding the first housing part into the second housing part. A follower element and/or a lever may be coupled with the housing for deforming said portion of the housing. The lever and/or the follower element may comprise a rotary portion, e.g. a wheel.

In an embodiment the housing comprises a first housing part slidably arranged in a second housing part, wherein the aperture stop comprises opposing movable and/or deformable portions connected to both the first housing part and second housing part and configured to deform as a function of a shift of the relative positions of the first and second housing parts. The movable and/or deformable portions may comprise deformable wall elements and/or wall segments movably interconnected, e.g. with a hinge and/or a fold.

In an embodiment, the light source, the aperture stop and the first light detector are aligned along an optical axis and the aperture of the aperture stop is adjustable symmetrically about the optical axis.

The position sensor may comprise a controller connected with the light source and the second light detector, and being configured to control operation of the light source, in particular light emission from the light source, as a function of a detection signal from the second light detector.

The position sensor may comprise a controller, connected with the first light detector and the second light detector and being configured to provide a sensor signal based on a detection signal of the first light detector as a function of a detector signal of the second light detector.

The position sensor may comprise an indicator connected with at least the first light detector configured for indicating signals as a function of a detector signal of the first light detector, wherein the indicator may be a graphical indicator.

An aspect comprises a wheel truing indicating instrument comprising one or more embodiments of the position sensor provided herewith.

In an embodiment, the wheel truing indicating instrument can be brought in contact with the rim of a wheel by a guide wheel, or other rotary contact member e.g. a rotary ball contact, that may be mounted on top of a pick-up lever. The guide wheel is e.g. made of hard plastic and it generally prevents damage the rim, compared to a sliding contact. The guide wheel may be on a swiveling axis to align the axis of rotation of the guide wheel proper in accordance with the position and orientation of (the rim of) the wheel to be trued. A follower pin or other element connects the lever to a moving part of the position sensor. For measuring small misalignment errors an electrical signal, e.g. the voltage signal, indicative of a value measured by the sensor can be amplified. The amplification factor may be set by a user interface, e.g. an adjusting knob, that may be provided on the housing. The truing indicating instrument can be mounted by means of a holder on a truing stand, bicycle frame or fork. The sensor and the wheel truing indicating instrument are fast reacting and resistant to shock and vibrations. An additional object of the invention is to provide a wheel truing indicating instrument that does not require the removal of the tire for its use and for alignment of the wheel and rim.

An optoelectronic linear position sensor as provided herewith contains an adjustable aperture stop of which the adjustment, which may comprise a movement of one or more portions, does not substantially hinder the illumination of a feedback photosensor (second light detector) provided in the sensor. The amount of light emitted by the light source of the position sensor can be stabilized by means of this feedback photosensor. The feedback may be used for compensation for temperature influences and/or degradation of the light source. The amount of light on a light detector (first light detector) can then be related to the aperture and the radiation pattern of the light source.

The light source may emit a light beam or a light cone in a direction of propagation along an optical axis. The movement of the aperture stop is preferably parallel or perpendicular to the optical axis, preventing angular dependencies.

In an aspect, a measuring instrument for wheel truing of a spoked wheel, e.g. a bicycle wheel is provided, with which radial and/or lateral errors in the wheel rim may be determined with respect to a predefined zero position and may be presented in analogue or digital form. The measuring instrument may comprise an opto-electronic linear position sensor which converts the position of an object (the rim) by means of an adjustable aperture (diaphragm) to an amount of light related to the position and detected by a photosensitive detector.

The diaphragm of the opto-electronic linear position sensor may comprise a feedback arrangement. By this, the amount of emitted light may be maintained substantially constant. The amount of light incident of the feed-back photodetector (e.g. photodiode) may thus not be hindered by changes in, e.g. movement of, the diaphragm.

An opto-electronic linear position sensor and a measuring device as provided herewith may contain a feedback system, that can control the amount of light emitted by a light source and thereby may be kept constant and/or used for determining a reference value. The amount of incident light on a feedback photosensor (second light detector) may not be hindered by changes in the movement of the diaphragm, increasing reliability. A measuring signal of the opto-electronic linear position sensor can be linearized, at least to a high degree, by applying a mask on the first light detector and/or optionally using a lens and/or mirror reflector at or near the light source.

In an embodiment, the aperture may comprise a pair of deformable triangles opposite each other and a relationship between the effective aperture and a measured position may be determined as the relationship Δ-[effective aperture]/A-position (Ad/Az). The relation may correlate to the sensitivity of the opto-electronic linear position sensor, and it can be determined by the length of the base of the two triangles at closed aperture.

In an embodiment, the aperture may comprise a pair of deformable triangles opposite each other of which one of the legs of at least one of the triangles is prolonged, extending beyond the apex of that triangle. By prolonging one leg of the triangle(s) at the side of the light source, a small change of the position of the target to be measured may be translated into a big change of the light that falls on the first light detector (photosensor), with the result that the measuring signal can be amplified.

The aperture stop can be created by one metal or plastic strip, wherein an end may be bent or folded into any form or shape. By moving the strip in line with the light beam an adjustable aperture can be created. The amount of incident light on the surface of the first light detector depends on the adjustment of the aperture and thus is a measure of the position of the target to be measured.

For creating the aperture a U-shaped curved strip can be used, wherein the end of one leg or the ends of two parallel legs of the strip may be bent or folded in any form or shape. By moving the strip in line with the light beam an adjustable aperture can be created by which the amount of incident light on the surface of the first light detector is a measure of the position of a target to be measured.

Brief description of the drawings

The advantages of the presently provided concepts and aspects will be better understood with reference to the following detailed description of a preferred embodiment thereof, which is illustrated in the accompanying drawings, in which:

Figure 1 is a transparent top view (cutaway drawing) of an embodiment of the electronic wheel truing indicating instrument, showing the optoelectronic linear position sensor and electronic components on a printed circuit board (PCB) in a housing, together with a lever and a guide wheel in contact with the rim of a wheel;

Figure 2 shows a front-view of two of the electronic wheel truing indicating instruments of Fig. 1 mounted on the front fork of a bicycle, for measuring a radial or lateral misalignment error;

Figure 3 is a perspective and transparent view of the inside of the optoelectronic linear position sensor indicated in Fig. 1;

Figure 4 is a drawing that shows the principle of operation of the aperture-stop of the sensor of Fig. 3;

Figure 5 shows characteristic curves of operation of the sensor of Figs. 3-4 in different configurations;

Figure 6 is a drawing that shows the top view of figure 3;

Figure 7 shows an alternative embodiment of the optoelectronic linear position sensor, in particular for accurately measuring small position changes or relocations;

Figure 8 shows a simplification of the schematic electrical diagram of the measuring circuit;

Figure 9 is a drawing that shows two examples of linear guide mechanisms to keep the movement of the legs of the U-shaped strip until the first fold or hinge of the aperture stop in a straight line with and parallel to the optical axis;

Figure 10 is a cross-sectional view C-C of figure 9, showing guidance of the first fold or hinge of the aperture stop by a groove at the bottom and top side of the diaphragm strip following a rail;

Figure 11 is a cross-sectional view D-D of figure 9, showing guidance of the U-shaped strip of the aperture stop by an oblong slot in the leg until the first fold or hinge of aperture stop and a knob-ended guide pin mounted on the inner walls on both sides of the housing.

Detailed description of the exemplary embodiment

Figure 1 is a transparent top view of an electronic wheel truing indication instrument G, that can measure accurate the misalignment of a bicycle wheel or other (spoked) wheel when in contact with a rotating wheel rim (1) that is more or less severely bent out of the (intended) plane of the rim. The electronic wheel truing indicating instrument can be mounted by means of a holder on a truing stand or even on the bicycle frame for centering and alignment of the rim. A housing (2) comprises the optoelectronic linear position sensor (3) provided herewith as sensing element, that in this embodiment is mounted on a printed circuit board ("PCB") (4), and which is configured for converting the position of the rim with respect to a pre-established zero position ("0"-value) or another reference value in a digital or analogic measure. The measured value that may be indicative of a misalignment error of the wheel and that can be positive and/or negative is shown on an optional display e.g. a bar graph array (5). Displaying can be done even when the wheel rotates fast. The tool can preferably be turned on and off by means of a slide switch (6) or some other switch.

The position of the rim relative to the sensor is transmitted as a linear travel to the position sensing element (3) by a guide wheel (7) that is mounted on top of a pick-up lever (8). The guide wheel may be made of hard plastic and/or another substantially incompressible material that prevents damage to the rim and provide accurate position determination. The pick-up lever (8) is pivotally mounted to the housing (2), here on a base plate (9) connected to the latter. The lever (8) is connected to a moving part of the position sensor (3), here by means of a follower pin (10). A spiral spring (11) as part of the position sensor pushes the guide wheel against the rim, but another resilient element in the sensor (3) and/or elsewhere in the instrument may be suitably provided as well. The stroke of the lever may be limited by a mechanical stop (12) in one or both directions of travel (see dashed arrows), here realised by two pins (12). A zero position can be established by fixing the truing indicating instrument in the holder at a distance to the rim associated with a predetermined value, e.g. "0", on the display (5).

Figure 2 shows suitable mounting positions of the electronic truing indicating instrument G on a bicycle fork (13) for measuring the misalignment for radial and lateral errors in the wheel rim (1). Here, two instruments G are shown but they may be integrated in a single device and/or be mounted on the same side of the wheel. A bar graph array (5) indicates the value of the misalignment error, positive or negative, with respect to a "0" position which is previously established. For a better readability of small misalignment errors the measured signal can be amplified. With the knob (14) on top of the housing the measurement sensitivity can be adjusted, e.g. by changing the gain of an amplifier, but other adjustment controllers may be provided.

Figure 3 is a perspective and transparent view of the optoelectronic linear position sensor (3) showing the inside of the sensor. The sensor (3) comprises an aperture stop (15), an IR-LED as a light source (16) and two light detectors (photodiodes in practice). One photodiode (17) serves as a feedback for the control of the light intensity, the other (18) serves as a transducer for measuring the amount of incident light through the aperture which is a measure of the position of a target object. These components are shown mounted in an exemplary small oblong closed box B. The aperture stop (15) is flexible, here being created by a thin metal or plastic strip that is bent in a square or curved U-shape (23) extending out of the box B and forming a target (19). The ends of the legs of the U-shape (23) are each provided with three creases (24) at a defined distance. By folding the strips at the creases (24) in a V-form, two opposite and symmetrical moving isosceles triangles (25) are formed, forming the aperture stop (15) proper. The end-side (26) of each triangle is fixed to the sides (27) of the box. In order to prevent distortion of the measurement by ambient light entering the box, the legs of the U-shape are passing the front side through fitting openings, here narrow slots, possibly provided with resilient lips or the like to prevent light leaking in. One or more sections of the walls and the parts of the aperture stop inside the box B may be covered with a matte, absorbing and/or nonreflecting dark paint to reduce or prevent reflection and scattering of the light beam of the light source in an undesired direction, which might lead to a distortion of the amount of light that falls on the first light detector and cause a measurement error.

Figure 4 is a drawing that shows the principle of operation of the aperture stop (15). The legs of the U-shape (23) are shifted by a change of position of the target (19) relative to the end-sides (26) of the U-shape (23) parallel to the direction of propagation of the light indicated with arrow L, resulting in a deformation of the triangles (25) at the folds (24): a change of the length a of the base and consequently also the height h of the triangles (25). Between the tops of both triangles (25) an effective aperture (15) is created. The amount of incident light through aperture (15) on the light detector (18) is a measure of the open area (A) of the aperture, thus of the configuration of the aperture stop and thus of the relative positions of the target (19) and the box B. The measuring range of the optical sensor of the invention is basically determined by the width of the light detector (photocell) and the length of the base "a0" of the triangles at closed aperture.

Figure 5 shows the characteristic curves of the relation between the effective aperture meaning the open area (A) of the aperture (15) and the position (P) of the target (19) at three different lengths (31, 32, 33) of the triangles' bases (and thus at three different heights of the triangles), when the aperture is closed (= aO). Thus, by the change of position of the target (19) the length of the base (a) of a triangle (25) changes accordingly and the height varies according to the formula:

where

The effective aperture is determined by

wherein W = the maximum width of the aperture (e.g. triangles maximally flat), hi and h2 are the heights of the triangles on opposite sides of the aperture (15), in all shown embodiments being chosen equal such that hi = h2 = h, and T being the transverse width of the aperture perpendicular to the direction of movement of the triangle apices. Note that the above equations hold for a rectangular aperture, but similar equations are readily found for non-rectangular shaped effective apertures.

In the shown embodiment, the triangles are isosceles which means that the legs c and b have equal length. The figure shows that the length of the base at closed aperture (aO) determines the relationship ΔΑ /ΔΡ (Ad/Az). The lager the hypotenuse, the lager this ratio. The length of base at closed aperture determines the sensitivity of the sensor. Applying scalene triangles is also possible. In comparison with isosceles triangles the relationship Ad/Δζ is smaller at an equal base length of aO and thereby the sensitivity of the sensor is less.

Figure 6 is a drawing that shows the top view of the optoelectronic linear position sensor in opened state (full lines) providing the aperture (15) and in a closed state (dashed lines) wherein the opening is closed and the triangles (23) may touch each other (indicated at position 20). By applying a mask to the light detector (18) or placing an optical lens (21) or a specular reflector (22) at the light source or a combination of these correction measures, linearity of the measuring signal can be improved.

Figure 7 shows an alternative embodiment of the optoelectronic linear position sensor for accurately measuring small position changes or relocations. By prolonging one leg of the (isosceles) triangles, a small change in the position of the target (19) translates into a big change of the aperture and as a consequence a big change of the amount in light that is incident on the light detector (18). The position sensor is therefore very sensitive and suitable for detecting very small movements or relocations of a target.

Figure 8 shows a simplification of a schematic electrical diagram for the translation of the amount of light incident on the light detector into an electrical signal. E.g. to make sure that the output current of the photo-electric sensor (18) is independent of the temperature and the aging of the LED, the separate feedback photodiode (17) is provided. Amplifier A1 regulates a constant quantity of light emitted by the LED (16). The resistor R3 of amplifier A2 determines the gain of the measuring signal and the height of the output signal V-out. However, other circuits may be suitably employed.

Figure 9 is a drawing that shows two examples of linear guide mechanisms to keep the movement of the legs of the U-shaped strip until the first fold (28) of the aperture stop (23) in a straight line with and parallel to the optical axis. A (curved) movement of the first fold (28) of the aperture stop (23) from sidewall (27) to the inner part of the housing (B) may lead to a measurement error. In the present embodiment the movement of the aperture stop (23) (diaphragm) can be supported by a groove (35) following a rail (34) (Fig. 10, see also below) and/or by an oblong slot (30) following a knob-ended guide pin (29) (Fig. 11, see also below). These guide means are preferably disposed on both sides of the housing. Linear guide mechanisms are in no way limited to this features. Other suitable guide mechanisms, securing the movement of the legs until the first fold of the aperture stop in a straight line with and parallel to the optical axis, may be provided.

Figure 10 is a cross-sectional view C-C of figure 9, showing guidance of the first fold (28) of aperture stop (23) by a groove (35) at the bottom and top side of the diaphragm strip following a rail (34). The rails (34) are disposed on the bottom and top and on both side of the box (B).

Figure 11 is a cross-sectional view D-D of figure 9, showing guidance of the U-shaped strip of the aperture stop (23) by an oblong slot (30) in the leg until the first fold of the aperture stop and a knob-ended guide pin disposed on the inside of the walls on both sides of the box (B). By this guide mechanism the movement the aperture stop in a straight line and parallel to the optical axis is secured.

The presented position sensor may use an IR-LED as the light source. Encapsulated LEDs may emit a parabolic radiation pattern. The polynomial opening curve of the aperture in relation to the position is compensated by the parabolic radiation pattern of such LED and gives an approximate linear measured signal as a result. The non-linearity of the measuring signal can be additionally reduced by using a mask on the light detector or an optical lens or mirror reflector at the light source, or a combination of these methods. The application of electronic components for signal-conditioning is in principle not necessary. When a linearity error should be minimized more, then further (digital) signalconditioning can be applied.

The moving parts of the sensor (in particular the aperture stop) do not make physical contact with the stationary parts (e.g. light detector). For this reason, the position sensor is a non-contact type and barely or not susceptible to wear.

Due to the optical measuring principle and the low force needed to move the aperture arrangement, the position sensor of the invention can measure the lateral or radial movement of a fast rotating wheel.

The disclosure is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims. E.g., the U-shape (23) and (one or both sides of the aperture stop (15) may be formed separate instead of being integrated. Further, one side of the aperture stop (15) may be fixed and the other side (15) movable and/or deformable. Instead of creases (24), hinges may be used; this may increase the wear resistance and the robustness of the sensordetails, elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with details, elements and aspects of other embodiments, unless explicitly stated otherwise. The sensor may also be used for measuring other positions and movements than wheels, e.g. for or as valve feedback position, servo feedback control for loudspeaker movement, throttle position sensing, pedal position sensing, dynamic motion measurement, vibration measurement, lens position sensor, float-Level sensor, etc.

Claims

1. A position sensor (3) having a housing, preferably substantially being light tight, containing a light source (16), an aperture stop (15) defining an effective aperture (A) and a first light detector (18) arranged to receive light from the light source (16) through the aperture of the aperture stop (15), wherein the effective aperture of the aperture stop is adjustable as a function of a deformation of a part of the position sensor (3), in particular deformation of the housing, wherein the position sensor comprises a second light detector (17) arranged to receive light from the light source (16) substantially independent from the effective aperture of the aperture stop.

2. The position sensor according to claim 1, wherein the effective aperture of the aperture stop is linearly adjustable as a function of a linear deformation of the at least part of the position sensor.

3. The position sensor according to any preceding claim, wherein the second light detector is positioned between the light source and the aperture stop and/or wherein the housing is divided in a first and a second compartment separated by the aperture stop, the light source and the second light detector being arranged in the first compartment and the first light detector being arranged in the second compartment.

4. The position sensor according to any preceding claim, wherein the deformation retains the relative positions of the light source, the first and second light detectors and the aperture stop.

5. The position sensor according to any preceding claim, wherein the deformation comprises deformation of a portion of the housing, e.g. shifting a first housing part with respect to a second housing part such as by sliding the first housing part into the second housing part.

6. The position sensor according to claim 5, comprising a follower element and/or a lever coupled with the housing for deforming said portion of the housing.

7. The position sensor according to claim 6, wherein the lever and/or the follower element comprises a rotary portion, e.g. a wheel.

8. The position sensor according to any one of claims 5-7, wherein the housing comprises a first housing part slidably arranged in a second housing part, wherein the aperture stop comprises opposing movable and/or deformable portions connected to both the first housing part and second housing part and configured to deform as a function of a shift of the relative positions of the first and second housing parts.

9. The position sensor according to claim 8, wherein the movable and/or deformable portions comprise deformable wall elements and/or wall segments movably interconnected, e.g. with a hinge and/or a fold.

10. The position sensor according to any preceding claim, wherein the light source, the aperture stop and the first light detector are aligned along an optical axis and the aperture of the aperture stop is adjustable symmetrically about the optical axis.

11. The position sensor according to any preceding claim, wherein the position sensor comprises a controller connected with the light source and the second light detector, and being configured to control operation of the light source as a function of a detection signal from the second light detector.

12. The position sensor according to any preceding claim, wherein the position sensor comprises a controller, connected with the first light detector and the second light detector and being configured to provide a sensor signal based on a detection signal of the first light detector as a function of a detector signal of the second light detector.

13. The position sensor according to any preceding claim, comprising an indicator connected with at least the first light detector and/or the controller or controllers in case of a position sensor according to claim 11 and/or claim 12, configured for indicating signals as a function of a detector signal of the first light detector, wherein the indicator may be a graphical indicator.

14. Wheel truing indicating instrument comprising the position sensor according to any preceding claim.

15. The wheel truing indicating instrument according to claim 14, comprising plural position sensors according to any one of the claims 1-13.