Patent Application
20220091626
The invention relates to a reading device and a method for reading a positional relationship between two components.
The challenge that one is faced with when a position reading is to be done on a movable part relative to a static part is how to make a device that is robust in relation to mechanical wear. In addition, it is a challenge to achieve high accuracy and repeatability in the position readings, and to find a solution that does not give erroneous readings caused by external influences.
Prior art for position reading in a joystick, for example, is using a potentiometer. A potentiometer is an adjustable voltage divider which is a mechanical device that is subjected to mechanical wear, and thereby, over time, subject to a change in characteristic and, thus, liable to give erroneous readings, and a potentiometer has a limited life.
An advancement of the technique which is used to a great extent in a joystick is the use of a Hall-effect sensor, which is an electronic component whose signal level changes with a change in magnetic fields to which it is exposed. The movable part of a joystick may then be equipped with magnets which change the signal level in the Hall-effect sensors that are mounted on the static part of the device when the movable part changes position. A drawback is that the device may be influenced by external magnetic fields which may then give erroneous readings. A variation in temperature may also give erroneous readings.
A known technique is using one or more light sources, and by changing the position of the joystick, one or more photodiodes or optical sensors are lit to indicate the joystick position. There are several variants and solutions here, but a drawback is that they have a certain drift by temperature changes and need electronic solutions that, to a certain extent, compensate for erroneous readings caused by temperature drift.
U.S. Pat. No. 4,587,510 discloses an analogue joystick which uses potentiometers to read the position. A drawback of using potentiometers is that a potentiometer is a mechanical structure that is subjected to wear and has a limited life. Another drawback is that, with respect to linearity of the signal, the characteristic may change over time, the device give erroneous readings and need repeated calibrations.
U.S. Pat. No. 4,459,578 discloses a variant of a joystick that makes use of Hall-effect sensors to read the position. This is an advancement in relation to using potentiometers which involves using components for position reading that are not liable to mechanical wear. A drawback of the method is that the device is prone to erroneous readings and drift of the signal if influenced by temperature changes or by magnetic fields that are not part of the device.
US20020080050A1 discloses an inductive joystick. An advantage of this type of joystick is that it does not have components that contributes to a drift of the signal. A drawback is that, in such a joystick, the signal may be disturbed by radio waves. Another drawback is that the device can detect movements only in the x- and y-direction.
EP1696300A1 discloses an optical joystick which has a light source that generates a conical light beam with an increasing diameter out from the light source, and that illuminates a major number of optical sensors simultaneously. A drawback of the solution is that one cannot make use of the possibility of resolution that modern sensors can give as they can have a distance between the optical sensors in the μm range, and a conical light beam will illuminate an increasing number of sensors the further out from the neutral position the light beam gets. The light source is arranged at a considerable distance from the pivotal point of the joystick and towards the optical sensors and will thus not be suitable for making use of modern sensors because of the large movement that the light beam will have when the handle of the joystick is being moved.
U.S. Pat. No. 6,232,959 discloses an optical mouse or joystick which uses a laser to carry out a position determination on an array of optical sensors. In a mouse or joystick, one will be restricted to using miniature lasers in which a typical diameter of the light beam is in the region of 1 mm. Such a large diameter of the light beam will not be able to make use of the resolution that current optical sensors may give, which may be of a magnitude of under 2 μm. Methods for focusing the laser beam by using focusing coils and light-directing lenses are also disclosed. The drawback of using a focusing coil is that the light beam gets a focal point in which the minimal diameter is obtained, and in which the light beam will be more out of focus, and will get an enlarged diameter when the joystick moves the light out of the focal point. This will then apply to devices in which the manoeuvring lever pivots around a pivotal point. Another drawback is that the beam-directors described, which may contain lasers, focusing coils and light reflectors, are built between the pivotal point of the joystick and the optical array. If the distance from the pivotal point of the joystick to the optical array gets to be too large, even slight movements of the manoeuvring part of the joystick will result in the movements of the light spots becoming too large for most standard optical sensors to be usable. The entire optical array of an image sensor is typically in the order of 5-3 mm.
WO1997005567 discloses an optical joystick which is designed for use opposite a PSD (position sensitive detector) or a photodiode quadrant, and which uses an aperture plate which is fixed in the housing of the joystick between the light source and the optical sensor. The light spot that is formed is described as larger than the aperture of the aperture plate. When the light source that is part of the movable part of the joystick is moved, the light spot formed by the light passing through the aperture plate will change its position on the optical sensor. A drawback of using a PSD is that it may give erroneous readings by temperature changes. A quadrant of photodiodes has primarily been developed to detect a centre point between the four photodiodes and is not very accurate for determining the position of the light spot outside the centre point. Thus, a quadrant of photodiodes is not the ideal component to be used for determining the position of a joystick that needs accurate positioning over the entire moving area of the joystick. Such a component will thus be able to give just 4 absolute position points and must use varying analogue values on the four photodiodes to calculate the position of the light spot. Then, when the analogue values may change by a temperature change, such a solution will give relatively poor accuracy in relation to using, for example, an image sensor with 16 million absolute position points.
US20070126700A1 discloses a device which uses light from, for example, a light emitting diode or a laser which is reflected from a plate with an uneven surface attached to the movable part of, for example, a joystick, in which the light falls on a PSD. This may detect in which direction the joystick is moving and thus, by means of software, calculate a position of the joystick. A drawback of using PSDs is that they do not have high accuracy with respect to erroneous readings or so-called drift by temperature changes, for example. To compensate for this, it has been suggested to include reference points in the plate with the uneven surface in order to be able to detect a zero every time the joystick is in this position and use this to continuously calibrate the joystick and reduce drift. Another drawback is that the solution thus requires software which is continuously to correct errors created by the components.
U.S. Pat. No. 6,081,257 discloses another reading device.
The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.
An object of the invention is to provide a device for position reading, in which the position transmitter is not subject to mechanical wear. An object is also to provide a device for position reading which can make use of current optical sensors to utilize the possibility that these give for a higher resolution in the position signal than what can be offered by the technology today. A further object is to provide a device for position reading which is not affected by external elements such as temperature, magnetic fields or radio waves. Another object is to provide a device which has an absolute position determination with 100% repeatability. An object is to provide a device which does not require extra software to maintain calibration or need a start-up calibration or calibration after a power failure.
The object is achieved through the features that are specified in the description below and in the claims that follow.
The invention is defined by the independent claims. The dependent claims define advantageous embodiments of the invention.
The invention relates, more specifically, to a reading device for reading a positional relationship between a first component and a second component, the first component comprising an optical sensor and the second component comprising a collimator configured for directing a light beam at the optical sensor by the collimator comprising a collimator housing with two openings opposite each other, each in a respective end part of the collimator housing. The optical sensor must be able to detect a change in the position of the light beam. A change in the positional relationship between the two components may thereby result in a change in the position of the light beam on the optical sensor. For example, if the second component is movable around a pivotal point which is fixed relative to the first component, a relative change in the angle between the first and second components may be read from the position of the light beam on the optical sensor. Alternatively, if the angle is kept constant, a change in the translational position of the second component parallel to the plane of the optical sensor may be read from the position of the light beam on the optical sensor. Herein, the plane of the optical sensor is called the x-y plane, whereas the direction parallel to the normal to the optical sensor is called the z-axis.
A collimator will, in this connection, indicate a device which gives a mainly unidirectional light beam from a light source. The collimator may, for example, comprise a collimator housing with two small openings opposite each other, each in a respective end part of the housing. The collimator housing may be closed, apart from the two openings. Light from one side of the collimator may enter through the first opening in different directions, whereas the light exiting through the opposite opening will essentially be a light beam that comes directly from the first opening. The degree of collimation of the light beam may be increased by having smaller openings, a larger distance between the openings, and by the collimator having a surface that absorbs light on its inside. Alternatively, the collimator may include a long and thin opening, for example an almost solid cylinder with only a narrow axial opening. The light source may be a lamp on the opposite side of the collimator to the optical sensor, for example an LED, it may be light existing outside the collimator, or light that is carried to the collimator via optical fibres.
Using a collimator has the advantage of allowing the light beam easily to be made very narrow, having substantially the same cross section after the collimator independently of the distance therefrom. This will have the advantage of the area on the optical sensor that is illuminated by the light beam not changing in size if the angle or distance between the two components changes. The light beam after the collimator may, for example, be arranged to have a cross section of an extent smaller than 50 μm, smaller than 25 μm or smaller than 10 μm, for example in the order of 1 μm. A narrow light beam may enable a high position resolution and make the reading device small.
The optical sensor may, for example, be an optical array of small individual sensors, for example an image sensor similar to those used in digital cameras. Each individual sensor is called a pixel. An optical array, for example an image sensor, may have small pixel sizes, each pixel being able to detect light. For example, the optical sensor may have a pixel size of an extent smaller than 50 μm, smaller than 25 μm or smaller than 10 μm, for example in the order of 1 μm. Such optical sensors with a small pixel size may also enable a high position resolution and make the reading device small.
The combination of a collimator with a microscopic light beam and an image sensor with a microscopic pixel size may therefore give a particularly high position resolution; the reading device may be made very small at the same time, and it is not affected by external factors such as magnetic fields or radio waves. This may open up new areas of application in relation to existing reading devices.
The collimator may further be configured for directing a second light beam at the optical sensor, whereby a relative rotation between the first and second components may be calculated. Alternatively, reading a relative rotation may be enabled if the cross section of the light beam is not circular but, for example, elongated.
The collimator may further be so configured that at least two light beams hit the optical sensor at different angles. In this way, a change in the distance between the two components will result in a change in the distance between the two light spots on the optical sensor. When the angles of the light beams are known, the distance between the two light spots can therefore be converted to a distance between the two components if the angle between these components is known.
In a second aspect, the invention relates to a method for reading a positional relationship between two components, the method comprising the steps of: passing light through a collimator in a second component towards an optical sensor in a first component, the collimator comprising a collimator housing with two openings opposite each other, each in a respective end part of the collimator housing; reading the position of the light beam from the collimator on the optical sensor; and calculating the positional relationship between the first and second components from the position of the light beam on the optical sensor. The positional relationship between the two components may, for example, be read by using the reading device according to the first aspect of the invention.
The reading device may, for example, be used in a joystick or an inclinometer.
In one embodiment, the invention relates to a reading device in the form of a joystick in which the handle element, which may be of various designs, has one or more light sources which receive energy via the shaft element of the joystick, wherein, according to the prior art, the light source may be provided with a battery and control circuits to ensure a stable supply to the light source to maintain a constant light intensity. The joystick may also use batteries of replaceable types, or rechargeable batteries in the handle element receiving energy by the batteries being charged, when required, when the joystick is not in use. As an alternative to a built-in light source, it is possible to use light existing outside the device and carry the light into the device through an aperture which may be a material of a translucent material or prisms. An alternative to letting the light in through an aperture may be letting the light into the device via one or more optical fibres. Here, a variant which continuously supplies the light source with energy via the shaft element and the pivotal point of the shaft element will be explained. As an extension of the lower end of the handle element, a preferably tubular extension rotatable relative to a shaft element continues. The tubular extension may also be fitted to the handle element as a separate part. The shaft element surrounding the tubular extension functions as a link between the handle element and the ball joint and is adapted for functioning also as a support for the rotation of the tubular extension. The support of the tubular extension may also be free-standing supports. The shaft element is attached to the handle element in a way that enables rotation of the handle element and the tubular extension relative to the shaft element. The shaft element and the tubular extension are preferably made from an electrically nonconductive material. The shaft element is attached to the ball in a ball joint which functions as a pivotal point for moving the joystick in the x-y plane. To achieve continuous energy supply to the light source, the ball may consist of two parts and be made of an electrically conductive material, the two halves of the ball having an insulating material between each half. The ball is held in place by two halves joined together, which, together with the ball, form a ball joint. In one or both of the halves holding the ball in place, electrical brushes are arranged, which will each be in electrical contact with a respective half of the ball. An electrical connection is arranged via the electrical brushes, the material of the ball, the shaft element to the control circuit of the light source, which may contain voltage regulation and current-limiting electronics for adaptation to a possible light emitting diode as the light source. The control circuit may also contain control circuits for charge control of a battery to further make the supply of power to the light source more stable. Continuous power supply to the light source may also be provided by there being an electrical coil arranged in the halves holding the ball of the ball joint, and by the ball of the ball joint having a built-in coil and the light source receiving its charging voltage by inductive transmission of power from the static part to the movable part. In the ball joint, a guiding groove is arranged, there being guide pins arranged in the halves of the ball joint, extending into the guiding groove. The ball may thus be moved freely in the ball joint, but a rotation of the ball is impossible. The bottom half of the ball joint is attached to a base in which the optical sensors and, possibly, electronic circuits for processing signals from the optical sensors are installed. Circuits for processing signals from the optical sensors may also be placed outside the reading device. The optical sensors are shielded from influence from external light by a casing having been installed between the base and the ball-joint arrangement. The casing may also be in one piece and consist of side walls and a bottom, which function as a base for mounting the optical sensors and possibly associated electronic circuits. In the rotatable tubular extension, there is a device which has one or more microscopic apertures. The device with the microscopic apertures may consist of a circular plate with one or more microscopic openings, and a device with apertures is installed at either end of the tubular extension. The device with the microscopic apertures may consist of a piece in which the ratio of the diameter of the microscopic passage to the length of the passage makes the light beam that exits the tubular extension not have any significant diffusion of light, but be an approximately 100% collimated light beam. The devices having the microscopic apertures may preferably be covered by a glass plate or some other transparent material to avoid blocking of the apertures by possible impurities, and make it easier to clean such contamination, if any. This device is a collimator. The light beams may be of varying shapes, but preferably have a circular shape. The lower part of the collimator, where the collimated light exits, has a positioning preferably at the centre of the ball, also called the pivotal point of the movable part. In this way, the point where the light exits the collimator will not have any movement in the horizontal plane relative to the static part of the device, but when the handle element is moved, only the angle of the collimated light will change. The result of this is that even if the movements of the handle element of a joystick are large, it is possible to use even the smallest optical arrays which may have a length and a width of just 4-5 mm. The invention may thus be used on even the smallest joysticks or computer mice.
When the handle element is being moved, the collimated light beam will move across an array of optical sensors, and the optical array may thus give an absolute position indication of the position of the joystick with a degree of resolution determined by the number of optical sensors that the optical array has, also called number of pixels. The resolution will not be limited just to how many pixels the optical array has. An optical array may have a 14-bit resolution which will correspond to values from 0-16383. This means that, from no light influence to light influence giving a maximum signal, a pixel will give a signal that varies with values from 0-16383. By using this possibility, the device may be given a further increased degree of resolution. A person skilled in the art may use a known position on the optical array generated by the collimated light to convert the signal to a desired output signal adapted for the control system of the user equipment. The output signal may be transmitted from the reading device to the control system of the user equipment via a cabled connection or via prior-art wireless data-transmission systems. By removing the handle element from the ball of the ball joint, the light source and collimator may be moved from the handle element to the ball, and by equipping the device with mouse buttons, the device may be used as a computer mouse of the trackball type with an absolute position indication. A joystick of this type will also be well suited as a mouse for computers where high precision is essential.
In a second embodiment, the invention relates to a reading device in the form of an inclinometer in which a pendulum is suspended from a frame structure, and in which a light source and a collimator are arranged in the pendulum. The collimated light is directed at an optical array which is mounted on the bottom frame of the structure. The bottom frame may be fixed to the supporting surface which is to be monitored for angular changes. The bottom frame may have adjustments so that, after having been installed on the supporting surface, it may be adjusted in such a way that the collimated light will have a starting point that is at the centre of the optical array. An angular change in the supporting surface will result in the pendulum with the collimated light moving on the optical array, and the amount of angular change and also the direction of the angular change may be read. The bottom frame and the frame structure will be made lightproof so that only light from the collimator illuminates the optical array. The inclinometer may be installed in varying forms of frame structures, such as in a pipe. With advantage, for constructing the inclinometer, materials that are stable with respect to temperature changes may be used to minimize erroneous readings. Where a great degree of accuracy is to be monitored over time, the inclinometer may, for example, be installed in a habitat having a stable temperature. Such inclinometers may, for example, be used for monitoring the stability of structures over time or be used in geological monitoring or in adjusting installations into a desired angle. The inclinometer may have control electronics which make measurements continuously or at desired intervals, wherein data may be read directly from the inclinometer or be stored on a built-in storing medium. Data may also be transmitted by way of prior-art wireless data-transmission methods. A person skilled in the art may use a known position on the optical array generated by the collimated light to adapt the output signal from the optical array to a desired customized reading from the inclinometer.
Today, high-quality inclinometers can theoretically detect angular changes of 1 microrad.
Pixel sizes of standard image sensors may, for example, be in the order of 2.4 μm and have a resolution of 14 bits. This is to say that, from no light influence to light influence giving a maximum signal, an optical sensor that represents one pixel may give values between 0-16383. By using the technique described by the invention and using an image sensor having a pixel size of 2.4 μm and a pixel resolution of 14 bits, it is possible to have a position resolution of 2.4/16383 μm=0.00015 μm. With a pendulum having a length from the point of suspension to the image sensor of 1 m, this may detect angular changes of 0.000349 microrad, which is several thousand times better than what current solutions can offer. The pixel size of image sensors is becoming constantly smaller, and a size of 1 μm is common today.
The invention could also be used as a reading device for position determination and control of machines, wherein the light source and collimator are preferably built into the movable part of the machine, and wherein an optical array of a suitable type may be used on the static part of the machine in order thus to be able to indicate a position determination for the movable part relative to the static part so that the control system of the machine may perform the desired tasks with great precision.
In what follows, examples of preferred embodiments are described, which are visualized in the accompanying drawings, in which:
In the drawings, the reference numeral 100 indicates a reading device.
In
In
A person skilled in the art may use data from the optical array 14 generated by the collimated light from the collimator of the reading device 100 and provide for the output signal to user equipment to be of the desired standard. This may be done by necessary control electronics being located in the reading device 100 or being located separately from the reading device. Data from the optical array 14 may also be coupled directly to a computer and by means of the necessary software generate control signals to units that are to be controlled by the reading device 100.
It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.
The use of the verb “to comprise” and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article “a” or “an” before an element does not exclude the presence of several such elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20190108 | Jan 2019 | NO | national |
This application is the U.S. national stage application of International Application PCT/NO2020/050016, filed Jan. 28, 2020, which international application was published on Aug. 6, 2020, as International Publication WO 2020/159378 in the English language. The International Application claims priority of Norwegian Patent Application No. 20190108, filed Jan. 30, 2019. The international application and Norwegian application are both incorporated herein by reference, in entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NO2020/050016 | 1/28/2020 | WO | 00 |
