Position detection system for light points on surfaces and in space

Abstract

The invention relates to a position detection system, having at least one position detection device (1) and at least one light source device (20 to 2N), which differs from the position detection device (1). Every light source device (20 to 20N) is designed to generate a light point at a distance from the at least one position detection device (1). The at least one position detection device (1) comprises at least two line scan image sensors (11, 11'), wherein directions of extent of sensor surfaces (12, 12') of the two line scan image sensors (11, 11') together enclose an angle greater than 0° and preferably 90°. Above each line scan image sensor (11, 11'), a slot aperture (13, 13') is provided such that the slot aperture (13, 13') and the associated sensor surface (12, 12') enclose an angle greater than 0° and preferably 90°. The at least one position detection device (1) and the at least one light source device (20 to 2N) each have interfaces for wireless communication via which the at least one position detection device (1) and the at least one light source device (20 to 2N) are temporally synchronised in order to enable the position of a light point generated by a respective light source device (20 to 2N) to be detected by a time-multiplex method during the emission of light by the at least one light source device (20 to 2N).

Description

[0001] Position detection system for light points on surfaces and in space

[0002] Systems that can detect the position of a light point (usually the light point of a laser beam) on a projection surface (e.g., a screen or wall) have been known for more than 20 years. The detected position is then sent in the form of X and Y coordinates to a computer, which further processes these X and Y coordinates. For example, the computer can set the position of a mouse cursor to these X and Y coordinates. If keystrokes are also transmitted, these can also be received and taken into account by the computer.

[0003] These systems, as described in WO 00 / 38102, for example, generally work as follows: A digital camera for generating spatially resolved images (e.g. a webcam) with, for example, a resolution of 1920 x 1080 pixels (picture elements) is aimed at a projection surface, and the image data output by the camera is searched for the pixel with the highest brightness value. This is usually the desired point of light, as the point of light is brighter than the rest of the projection surface (otherwise the point of light in the projection surface would not be visible to a user). The position of the pixel found in this way within a receiving surface (e.g. a CCD sensor) of the camera is determined by its design and is therefore known. Subsequently, the position of the point of light on the projection surface can be deduced from the position of the pixel within the receiving surface of the camera.For this purpose, a calibration between the camera and the projection surface may have taken place beforehand. If a light source / light source device for the light point (e.g., a laser pointer) also has buttons, their status can also be transmitted (wired or wirelessly) to the camera or a computer connected to the camera. As a result, everything on the projection surface that can also be controlled with a computer mouse, for example, can be controlled with a laser pointer with a wireless module.

[0004] When using multiple light source devices and thus multiple light points at the same time, it is not sufficient to simply search for the pixel that outputs the highest brightness value.

[0005] To distinguish between different light points, one approach has been to use (laser) light with different wavelengths in combination with multiple cameras, each with adapted filters. However, this is a very expensive solution due to the use of multiple cameras.

[0006] It was further proposed to use a time-division multiplexing method in which the individual light source devices are switched on synchronously with the camera in predefined, different time windows on the time axis T, but switched off in the other time windows. This is illustrated in Figure 1.

[0007] In the example of Figure 1, the camera transmits a synchronization signal S at regular time intervals on the time axis T, which is received by the light source devices, so that all light source devices operate synchronously with the camera. The light source device with the number 0 emits light in the time window F00 (e.g., by switching on a laser) and interrupts the light output at the end of the time window (e.g., by switching off a laser). Then, the light source device with the number 1 emits light in the time window F01 and interrupts the light output again at the end of the time window, and so on. After the light output by the light source device 99, all light source devices wait for the next synchronization signal S, and this process is repeated endlessly (e.g.,20 times per second) so that the position of the light points on the projection surface attributable to the light source device 1 to 99 can be detected without excessive jumps.

[0008] Due to the short light output by the individual light source devices, the light points generated by the individual light source devices on the projection surface are generally not visually perceptible or only poorly perceptible to the user. To improve user orientation, a computer can display an individual cursor (e.g., in different colors) for each light source device on the projection surface, so that each user of a particular light source device knows where they are pointing. The synchronization signal S can be transmitted to the light source device using a cable or wireless method, electrically, light-based, or radio-based.

[0009] However, even these previously known systems have severe limitations with regard to the number of light source devices that can be used simultaneously (although due to the time-division multiplexing process, only one light source device emits light at a time). The reason for this is that (as with any camera) it is not only the brightness of the light point that determines whether the light point can still be detected by the camera, but also the time, because the light energy (power times time) determines which output voltage a sensor generates for each individual pixel. The more light source devices are used, the shorter the period of time during which a particular light source device emits light during a time window using the time-division multiplexing process.

[0010] To solve this problem, the camera's sensitivity could be increased to compensate for the shorter time during which the light spot is generated. Sensitivity is directly proportional to the area of ​​the camera's individual pixels. However, increasing the size of each pixel in the X and Y directions leads to a quadratic increase in the sensor area, thus significantly increasing manufacturing costs. Furthermore, there are technical limitations, as such a large sensor area must be feasible.

[0011] With regard to the transmission of the synchronization signal required for the time-division multiplexing process, cable-based synchronization methods, in which the light source devices are connected to the camera, are only very slightly susceptible to interference. However, they have the disadvantage that a user of the light source device cannot move freely. Light-based or radio-based synchronization methods, in which the synchronization signal is transmitted between the camera and the light source device via light or radio, do not have this disadvantage, but they are more susceptible to interference and are often affected by a back-and-forth wandering (jitter) of the synchronization signal S on the time axis T. This jitter results from the fact that the synchronization signal S must be encoded in such a way that no false detection can occur. As a result, for example,In the 2.4 GHz band, only bit rates of 1 million bits / second are achieved, although the carrier signal is considerably faster at 2.4 billion oscillations / second.

[0012] From document US 3,951,550, it is known to use two stripe radiation detectors (such detectors are also known as line image sensors) instead of a standard spatially resolving camera to detect the position of a light spot on a projection surface. These detectors are rotated 90 degrees relative to each other and spaced apart in a common plane. The two stripe radiation detectors are separated from each other in a light-tight manner by a partition. Above each stripe radiation detector, a slit diaphragm is provided in a common plane, which in turn is rotated 90 degrees relative to the associated stripe radiation detector. Light can only fall onto the respective stripe radiation detector through the respective slit diaphragm. The plane in which the stripe radiation detectors are arranged is spaced parallel to the plane in which the slit diaphragms are arranged.One fringe radiation detector determines the X position of the pixel, the other fringe radiation detector determines the Y position of the pixel.

[0013] The solution known from US 3,951,550 has the disadvantage that the slit diaphragms assigned to the stripe radiation detectors are spaced apart from one another, resulting in a different aperture angle in the X and Y directions, since the length of the slit influences the field of view in one direction and the length of the stripe radiation detector influences the field of view in the other direction. However, it is desirable to have the same aperture angle in both the X and Y directions. Furthermore, the solution known from US 3,951,550 has the disadvantage that the slit diaphragm for the X direction and the slit diaphragm for the Y direction are contained in a single diaphragm disk, so that a further spatial separation of the stripe radiation detectors is not possible.

[0014] A stripe radiation detector / line image sensor as used in US 3,951,550 is explained in more detail below with reference to Figure 2.

[0015] Although not disclosed in US 3,951,550, the solution proposed in US 3,951,550 using a stripe radiation detector / line image sensor has the advantage that the sensitivity can be increased by increasing the height (Height H) of the individual pixels transverse to the direction of extension of the stripe radiation detector / line image sensor, without changing the width (W) of the individual pixels and thus the spacing of the individual pixels in the direction of extension of the stripe radiation detector / line image sensor. The width of the individual pixels determines the resolution achievable using the stripe radiation detector / line image sensor (accuracy of position determination); the height of the individual pixels determines the sensitivity proportionally, given the same width. The line image sensor has a total width L (Length), which corresponds to the number of pixels multiplied by the width of the individual pixels.

[0016] It is an object of the present invention to provide a position detection system for light points on surfaces and in space, which overcomes the disadvantages of the above prior art and solves one or more of the following problems:

[0017] 1. Detection (i.e., determination of the position and discrimination) of extremely short-duration light spots (less than 100 microseconds) on a projection surface generated by light source devices; these short-duration light spots may also be referred to as flashes of light; for example, these light spots may be generated by a laser diode controlled by a microcontroller and radiating towards the projection surface.

[0018] 2. Detection (ie determination of the position and discrimination) of light flashes of extremely short duration (less than 100 microseconds) from light source devices moving in a plane (such as light-emitting diodes / LEDs moving on a surface controlled by a microcontroller).

[0019] 3. Detection (i.e., determination of the position and discrimination) of light flashes of extremely short duration (less than 100 microseconds) from light source devices moving in three-dimensional space (such as light-emitting diodes / LEDs controlled by a microcontroller moving in 3D space); the determination of the position in space is made possible by the use of several position detection devices described below, which "view" the space and thus the moving light source devices from different angles.

[0020] 4. Synchronization of a microcontroller control for the light source devices used to enable differentiation of the light source devices.

[0021] 5. Transmission of states of multiple buttons of the light source devices used or of other status information of the light source devices, wherein the transmission takes place in the form of a light / light signal emitted by the respective light source device; this light emitted by the respective light source device is primarily used to determine the position of the light source device or a light point produced by the light source device on a projection surface and to distinguish between different light source devices / light points.

[0022] These problems are solved by the combination of the features of independent claim 1. Preferred developments can be found in the dependent claims.

[0023] A position detection system comprises at least one position detection device and at least one light source device. The light source device contains a light source (according to one embodiment, an LED or a laser diode). The at least one light source device is different from the at least one position detection device and, in particular, is spaced apart. Each light source device is designed to generate a light spot spaced apart from the position detection device. This light spot can, for example, result from light emitted by the at least one light source device striking a projection surface and forming a light spot there; alternatively, however, it is also possible to directly detect the light emitted by the at least one light source device (which, according to one embodiment, then comprises a particularly non-directional point light source such as an LED) as a light spot.The at least one position detection device comprises at least two line image sensors, each with sensor surfaces arranged along a row. The extension directions of the rows of sensor surfaces of the two line image sensors form an angle of greater than 0° with one another. The extension directions must therefore not be parallel. According to one embodiment, an angle of 90° is provided. The "extension direction" is understood to mean the direction along which the sensor surfaces are arranged along the row of a line image sensor. A slit diaphragm is provided above each line image sensor such that the slit diaphragm forms an angle of greater than 0° with the associated sensor surface. The slit diaphragms must therefore not run parallel to the extension direction of the sensor surfaces. Here, too, the angle is 90° according to one embodiment.The at least one position detection device each has an interface for wireless communication, and the at least one light source device each has an interface for wireless communication. The at least one position detection device and the at least one light source device are synchronized in time via the wireless communication interfaces to enable position detection of a light spot generated by a respective light source device using a time-division multiplexing method when light is emitted by the at least one light source device. The sensor surfaces of the at least one position detection device serve to determine an XY position of the respective light spot, and the time-division multiplexing method serves to enable an association between detected light spots and the different light source devices that generated them.This is achieved by the light source devices emitting light one after the other, wherein the at least one position detection device knows in the time-multiplex method at which point in time a respective light source device emits light.

[0024] If two or more position detection devices are provided, which detect the light points from different angles, the position of the respective light point in 3D space can also be determined by combining the XY positions of a respective light point detected by the individual position detection devices. According to one embodiment, the light point directly generated by the at least one light source device is detected, and not its image on a projection surface. This determination indirectly allows the location of a person or object to which the light source device is attached.

[0025] If the at least one light source device has buttons, then according to one embodiment it is designed to transmit the state of the buttons and / or status information as data bits modulated on a light spot emitted by the at least one light source device. This information then does not need to be transmitted via the wireless communication interfaces. Then, according to one embodiment, the at least one position detection device has a photosensor (such as a photodiode) and is designed to receive the data bits transmitted by the at least one light source device in the modulated light spots, wherein the data bits are assigned to an individual light source device using the time-division multiplexing method. The photosensor can be the same as or different from the sensor surface of a respective position detection device.

[0026] To regulate a transmission power, the at least one position detection device is configured, according to one embodiment, to send data packets to the at least one light source device via the wireless communication interfaces. The data packets are initially sent with low transmission power and then repeatedly sent with increasing transmission power. Packet numbering of the data packets enables the at least one light source device to determine whether a data packet has already been received with low transmission power, and the at least one light source device is configured to discard duplicates after receiving a data packet. If the at least one light source device then sends a corresponding feedback signal to the at least one position detection device, regulation of the transmission power is possible.

[0027] Depending on the type of light source device, the light emitted by the light source of the light source device is harmful to the human eye if it is shone directly into the human eye. In order to improve the safety of the system in this regard, the at least one position detection device is designed, according to one embodiment, to regularly send a command to this light source device upon detection of a light point of a light source device via the wireless communication interfaces (according to one embodiment, at the same frequency as the light source device generates light points; alternatively, at a higher or lower frequency than the light source device generates light points), which command causes the light source device to set a number of light points per second to a maximum value, and the at least one light source device is designed,to regulate the frequency of light points generated per second by the respective light source device down from a maximum value, provided that no command is received from the at least one position detection device, to set the number of light points generated per second to a maximum value. Furthermore, the at least one position detection device is designed to stop the regular transmission of the command if no light point of the light source device could be detected for a certain period of time, which is longer than the time between two light points generated by the light source device. Since the number of light points generated per second is directly proportional to the emitted power at constant light intensity and duration of a respective light point, the (light) energy emitted by the respective light source device is automatically reduced to a minimum.as long as a light point originating from the light source device is not in the reception range of the position detection device anyway.

[0028] To enable feedback to a user, the at least one light source device according to one embodiment has at least one vibration motor and / or at least one loudspeaker and / or at least one display, and the at least one position detection device is configured to send commands for activating the at least one vibration motor and / or the at least one loudspeaker and / or the at least one display of a respective light source device via the wireless communication interfaces. These commands are then used by the at least one position detection device to activate the at least one vibration motor and / or the at least one loudspeaker and / or the at least one display.

[0029] The time-division multiplexing method requires that the at least one light source device and the at least one position detection device use the same time, for which synchronization takes place via the wireless communication interfaces. According to one embodiment, the wireless communication interfaces are designed for communication in the 2.4 GHz band. This band is also used by Bluetooth devices and is therefore available for use. However, there is a risk that individual channels in the band are or will be occupied by other Bluetooth devices. To avoid problems here, the at least one position detection device is designed to block a channel in the 2.4 GHz band by sending a first data packet, the transmission duration and thus end time of which is known in the at least one position detection device, via a first wireless communication interface.The transmission duration (time between the start and completion of transmission) can be determined in advance by measurement and depends in particular on the components used in the first wireless communication interface. The transmission duration can therefore be stored as a constant in the position detection device and the light source device. This first data packet is fully valid, identified as a Type 1 data packet, and contains the current time of the position detection device as the zero point to be used by the light source device in the time-division multiplexing process. If the first data packet is received by the light source device and it is recognized that the first data packet is valid, the time of the position detection device can be used by the light source device as the zero point in the time-division multiplexing process. Second and further data packets received later can thus be ignored by the light source device.However, the position detection device does not know whether the first data packet has been received by the light source device. Therefore, the at least one position detection device is further designed to send a second data packet directly after the end time of the first data packet. This second data packet is fully valid, identified as a Type 2 data packet, and again contains the current time of the position detection device; this time lies after the time transmitted in the first data packet by the transmission duration and thus after the zero point of the time-division multiplexing method by the transmission duration. If this second data is received by the light source device and it is detected that the second data packet is valid, the time of the position detection device minus the transmission duration by the light source device can be used as the zero point in the time-division multiplexing method.This process can be repeated with third and further data packets, each spaced apart in time by the transmission duration. The light source then recognizes, based on the communicated type of data packet, how often the transmission duration must be subtracted from the time contained in the data packet of the position detection device in order to arrive at the time to be used by the light source device as the zero point in the time-division multiplexing method. For technical reasons, it may be advantageous for the at least one position detection device to have a first and a second interface for wireless communication, which are used alternately to transmit data packets in immediate succession. However, this is not absolutely necessary.

[0030] According to one embodiment, the at least one light source device is configured to generate an internal clock signal, to determine a clock deviation by comparing it with a clock signal received from the at least one position detection device, and, upon detection of a deviation, to recalculate a time constant defined in the at least one light source device for switching the at least one light source device on and off based on the clock deviation, and to use this newly calculated time constant for switching the at least one light source device on and off. According to this embodiment, the received clock signal is therefore not used to directly change the internal clock signal of the light source device; rather, the adaptation takes place by means of an adapted time constant, which is used together with the internal clock signal to switch the light source device on and off.

[0031] With a very large number of light source devices to be distinguished, the clock rate in the time-division multiplexing method becomes very short. Accordingly, little time is available in each light source device for processing a synchronization data packet received from the at least one position detection device via the wireless communication interfaces. To solve this problem, according to one embodiment, the at least one wireless communication interface in the at least one position detection device is configured to modulate a synchronization pattern initiated by a controller of the position detection device after a data packet onto a carrier wave that is then still active without data.This synchronous pattern can, for example, be a shift-resistant binary pattern that is not mapped onto itself if shifted by fewer bits than the length of the binary pattern. Such a binary pattern allows reliable detection of the beginning of the respective pattern. The interface for wireless communication in the at least one light source device is then designed to wait a short time after each data packet to see whether such a synchronous pattern appears on the carrier wave and to immediately store an internal timer value at the end of the synchronous pattern. This timer value is read out after decoding and checking the actual data packet and used to synchronize the time-division multiplexing process.Since the synchronization pattern is a simple binary code distinct from the actual data packet, which can be recognized by pattern matching, it is not necessary to process a data packet for this type of synchronization. Rather, it is sufficient to determine that a valid synchronization pattern has been received. After processing the actual data packet, the stored timer value can be used for synchronization.

[0032] With the optics used according to the invention (combination of line scan sensor with slit diaphragm), the output signal from the sensor surfaces of the line scan sensor results in a bell-shaped curve when the signal is plotted across the linearly arranged sensor surfaces. The desired useful signal originating from a light point is then a narrowband local maximum on the bell-shaped curve. According to one embodiment, this local maximum is found by subtracting the output signal of the line scan sensor without detection of a light point from the output signal of the line scan sensor when a light point is detected. This output signal of the line scan sensors, which is obtained when none of the light source devices is active, is referred to below as the subtract signal or "second dark slice." The subtract signal can be obtained automatically at regular intervals and stored in a memory.Then, according to this embodiment, the at least one position detection device further comprises an (instrument) operational amplifier which is designed to subtract another signal from its input signal, wherein the (instrument) operational amplifier receives as input signal a signal output by the line image sensors of the at least one position detection device and as signal to be subtracted the subtract signal stored in a memory of the at least one position detection device.

[0033] Depending on their sensitivity, the sensor surfaces of the line image sensors require a certain minimum light incidence below which they cannot operate. To ensure that this minimum light incidence occurs on all sensor surfaces of the line image sensors, the at least one position detection device has internal light sources connected to a controller of the position detection device, which are configured to illuminate the sensor surfaces of the line image sensors of the at least one position detection device under the control of the controller. The internal light sources are different from the at least one light source device.

[0034] According to one embodiment, the controller of the at least one position detection device uses an output signal from the line image sensors to regulate the internal light sources. This output signal is obtained when the internal light sources are active, but none of the light source devices to be detected is active. Such an output signal is also referred to below as a "first dark slice." The controller then controls the internal light sources such that all sensor surfaces of the line image sensors output a signal that is above the dark voltage of the respective sensor surface. If the "first dark slice" is created at regular intervals, it is possible to dynamically account for fluctuating lighting situations due to reflections or cloud cover.

[0035] According to one embodiment, the at least one position detection device has a controller, and the line image sensors are connected to the controller via data lines. According to one embodiment, the sensor surfaces of the two line image sensors of the at least one position detection device are arranged in a common plane.

[0036] According to one embodiment, the slit diaphragms of the at least one position detection device provided above each line image sensor are arranged in a plane which is parallel to the plane in which the sensor surfaces are arranged.

[0037] According to one embodiment, the sensor surfaces of the two line image sensors of the at least one position detection device are shielded from one another by partition walls such that the light falling on one sensor surface does not reach the other sensor surface.

[0038] According to one embodiment, the length of a time window in the time-division multiplexing method is less than 100 microseconds.

[0039] According to one embodiment, the at least one position detection device is designed to emit an optical carrier wave or a radio signal for the purpose of synchronization in the multiplex method, and the at least one light source device has a corresponding receiver.

[0040] According to one embodiment, the light emitted by the light source device lies in the human-visible wavelength range between 400 nanometers and 780, and can thus be seen by humans. This is particularly helpful when the position of a light spot formed on a projection surface is to be detected. However, if the position of the light spot formed on the light source itself is to be detected, the light emitted by the light source device lies in the infrared range, according to one embodiment.

[0041] Embodiments of the invention are explained in more detail below with reference to the figures. Herein:

[0042] Figure 1 schematically shows a time-division multiplexing method from the prior art for distinguishing several light points on a projection surface;

[0043] Figure 2 shows schematically a stripe radiation detector / line image sensor as can be used in the prior art and the present invention;

[0044] Figure 3 schematically shows a position detection system which uses a position detection device according to the invention in combination with light source devices;

[0045] Figure 4 schematically shows the idealized output of a stripe detector / line image sensor when viewing a white surface; Figure 5 schematically shows a cross-section through a line image sensor perpendicular to the direction of extension of a slit diaphragm;

[0046] Figure 6 schematically shows the idealized output of a fringe radiation detector / line image sensor when viewing a flash of light;

[0047] Figure 7 schematically shows the idealized output of a fringe detector / line scan sensor when viewing a flash of light incident at a shallower angle than in Figure 6;

[0048] Figure 8 schematically shows the idealized output of a fringe detector / line scan sensor when viewing a flash of light incident at a shallower angle than in Figure 6, before and after signal boosting;

[0049] Figure 9 shows schematically the signal output by the position detection device according to the invention after processing, which signal is generated by an incident light flash;

[0050] Figure 10 schematically shows a time-division multiplexing method for distinguishing multiple light source devices according to the present invention;

[0051] Figure 11 schematically shows an alternative embodiment of the sensor surface of a line image sensor according to the present invention;

[0052] Figure 12 schematically shows a Fresnel lens that can be arranged in front of a line scan sensor in addition to a slit diaphragm or as an alternative to the slit diaphragm. Figure 3 schematically shows a position detection system that uses a position detection device according to the invention.

[0053] The position detection system comprises a position detection device 1 and a number of light source devices 20 to 2N. The light source devices can be, for example, laser pointers or LEDs.

[0054] The position detection device 1 comprises (at least) two line image sensors 11, 11', wherein the extension directions of sensor surfaces 12, 12' of the two line image sensors 11, 11' are rotated by 90° relative to each other and are arranged in a common plane.

[0055] It is emphasized that the present invention is not limited to an angle of 90° between the sensor surfaces of the line image sensors or to the use of only two line image sensors; rather, it is sufficient if the sensor surfaces of the line image sensors form an angle with each other (i.e., they are not all parallel to each other). Furthermore, the present invention is not limited to sensor surfaces located in a common plane.

[0056] In a plane parallel to the plane in which the sensor surfaces 12, 12' are arranged, a slit diaphragm 13, 13' is provided above each line image sensor 11, 11' such that the slit diaphragm 13, 13' forms an angle of 90° with the associated sensor surface 12, 12'. Figure 3 shows only the part of each slit diaphragm 13, 13' that transmits light (i.e., the rectangles designated by reference numerals 13, 13' are translucent, whereas the position detection device 1 is otherwise surrounded by an opaque housing into which the slit diaphragms 13, 13' are incorporated; the housing is otherwise not shown). Thus, light can only pass through each slit diaphragm 13, 13' onto the associated sensor surface 12, 12'. The sensor surfaces 12, 12' are shielded from each other by partition walls so that the light falling on one sensor surface does not reach the other sensor surface.

[0057] The line image sensors 11, 11' are connected to a controller 15 (for example, a microcontroller) via data lines (not shown). The controller 15 is further connected via data lines (not shown) to internal light sources 14, 14', a wired communication interface 16 for communication with a computer (which may be, for example, a USB interface), a wireless communication interface 17 for communication with the light source devices 20 to 2N, and a memory 18. The light source devices 20 to 2N each also have, in addition to light sources for emitting light, interfaces for wireless communication and controllers (for example, microcontrollers). These, however, are not specifically shown, since light source devices 20 to 2N with corresponding interfaces and controllers are known from the prior art.Even if only one controller 15 is shown above, several controllers can also be provided in the position detection device 1.

[0058] In Figure 3, it has also been omitted to show auxiliary systems such as energy sources and timers (timers) which are present in both the position detection device 1 and the light source devices 20 to 2N.

[0059] The output signal 1 of one of the line image sensors 11, 11', which results when a white surface is viewed with the line image sensor, is shown schematically in Figure 4. U indicates a voltage amplitude during the sequential readout of the N pixels of the line image sensor, which are arranged at a position P in the extension direction of the line image sensor (left pixel 0, right pixel N1):

[0060] The individual pixels (photoelements) of the line image sensor have the property that they only generate a signal above a certain dark voltage 2. For brightness values ​​below this dark voltage, there is therefore no change in the output signal 1, ie everything below line 2 generates the same minimum voltage (unlike what is shown in Figure 4).

[0061] Furthermore, Figure 4 is idealized because in practice the output signal 1 does not produce such a smooth curve, but contains all the light / dark values ​​of the observed white area. Furthermore, different values ​​arise due to the fact that the individual pixels of the line scan sensor are not 100% identical and there may be impurities on the top side of the line scan sensor. Every small shadow and every minimal difference in brightness of the white area is visible in the output signal and can change at any time, for example if the light in the room changes or if a window is opened or closed, thereby changing reflections in the room. This rather undesirable variation in the output signal 1 is referred to below as the "background image." The reason for the curve shape shown in Figure 4 is explained below with reference to Figure 5.

[0062] If one considers the arrangement, for example, of the line image sensor 11 assigned to the X-direction with the slit diaphragm 13 mounted above it in cross section transverse to the direction of extension of the slit diaphragm 13, the image shown schematically in Figure 5 results.

[0063] From Figure 5, it can be seen that a light point LL on the left of the projection surface (or light emitted by a light source device located on the left) is imaged onto a pixel SR on the right of the line image sensor S (reference numeral 11 in Figure 3), and a light point LR on the right of the projection surface (or light emitted by a light source device located on the right) is imaged onto a pixel SL on the left of the line image sensor S. A light point LM in the center of the projection surface (or light emitted by a light source device located in the center) is imaged onto the pixel SM in the center of the line image sensor S (this, of course, only applies if the position detection device is aligned exactly centrally with the projection surface). Part of the light is reflected by an upper (glass) layer of the line image sensor S as reflected light R, and the non-reflected remainder reaches a respective photoelement of the sensor surface below.The distance of the line image sensor S to the slit diaphragm of typically 1 cm is negligible compared to the distance between the position detection device 1 and a projection surface (not shown) of typically > 100 cm.

[0064] The curve shape shown in Figure 4 has three reasons:

[0065] 1. In the arrangement shown, the projection point LG hits the sensor surface of the line scan sensor S at an angle of approximately 45°. The distance from the sensor point SL to the projection point LR is therefore, in the example shown, 1.41 times (square root of 2) the distance from the sensor point SM to the projection point LM. Since the light energy decreases quadratically with the distance, the light energy at the outer points of the sensor surface of the line scan sensor S is only half as high as at the center of the sensor surface of the line scan sensor S.

[0066] 2. The effective slit width decreases with increasing angle (deviation from light incident perpendicularly on the slit and thus the sensor surface of the line image sensor S), the effective slit width in Figure 5 becomes increasingly narrower from the center outwards and thus lets through less light.

[0067] 3. With increasing angle (deviation from light incident perpendicularly on the slit and thus the sensor surface of the line image sensor S), more and more light is reflected from the surface of the line image sensor (referred to as "R" in Figure 5) instead of reaching photoelements (not shown) of the sensor surface of the line image sensor and becoming effective there.

[0068] If you now create a briefly flashing light point on the projection surface with a light source of the light source device (light flash) or if you let a light source of a light source device located there light up briefly (light flash), then the output signal 1 shown schematically in Figure 6 with a voltage amplitude U is created when the N pixels (left pixel 0, right pixel N-1) are read out sequentially.

[0069] The light flash, which in the example is located to the left of the center on the projection surface, generates an amplitude increase 3A (peak) at the output of the line image sensor S.

[0070] The further this flash of light moves to the left in the example, the further the amplitude increase 3B moves to the right, becoming smaller (for reasons explained above) and eventually falling below the dark voltage 2, so that the position of the flash of light can no longer be detected. This is shown schematically in Figure 7.

[0071] In order to be able to use all the pixels of the line image sensor S / 11, it is therefore necessary to raise the signal at the two edges of the line image sensor S / 11, as shown schematically in Figure 8. This is achieved according to the invention in such a way that internal light sources (preferably LEDs) 14, 14', which are controlled by the microcontroller and provided in the position detection device 1, are directed onto the sensor surfaces 12, 12' of the line image sensors 11, 11' in such a way that they generate an output signal 4 shown in Figure 8 without additional light incidence on the sensor surfaces 12, 12' of the line image sensors 11, 11'.

[0072] For this purpose, the internal light sources 14, 14' are provided between the sensor surfaces 12, 12' of the line image sensors 11, 11' and the associated slit diaphragms 13, 13'. The light falling from the internal light sources 14, 14' onto the sensor surfaces 12, 12' is added to the output signal 3B (which would result without the use of the internal light sources 14, 14') by the photoelements of the sensor surfaces 12, 12' of the line image sensors 11, 11' when additional light enters through the slit diaphragms 13, 13' from the outside, thus forming a raised output signal 3C which lies above the dark voltage 2 (this coincides with the X-axis in Figure 8), so that the position of the light flash can be detected, although the light flash is so far to the left that it would no longer be detected in the output signal 3B of Figure 7 without the use of the internal light sources 14, 14'.

[0073] By using the internal light sources 14, 14', light flashes located far outwards relative to a light incidence perpendicular to the sensor surfaces can also be detected and their positions can be determined.

[0074] It was described above that the internal light sources 14, 14' are provided between the sensor surfaces 12, 12' of the line image sensors 11, 11' and the associated slit diaphragms 13, 13'. An improved variant of irradiating the sensor surfaces 12, 12' of the line image sensors 11, 11' according to the invention is to arrange the internal light sources 14, 14' next to the line image sensors 11, 11' on a circuit board (not shown) supporting the line image sensors 11, 11'. The internal light sources 14, 14' then radiate from below onto a plate 13P (shown in Figure 5) in which the slit diaphragms 13, 13' are formed. This plate 13P is then provided on its side facing the sensor surfaces 12, 12' of the line image sensors 11, 11' with a white diffuse reflector (e.g., matte white plastic) 131, as shown in Figure 5. This reflector is located directly next to the respective slit diaphragm 13, 13' and diffusely reflects the light onto the underlying sensor surface.

[0075] The light emitted by the internal light sources 14, 14' preferably has the same wavelength as the light emitted by the light source devices 20 to 2N, because this light (or the output signal of the line image sensors 11, 11') must optionally also pass through an interference bandpass filter.

[0076] In the following, the signal processing according to the invention by the at least one controller 15 of the position detection device 1 is described.

[0077] At the output of the two line scan sensors 11, 11', there is a preamplifier (not shown) to significantly increase the signal-to-noise ratio. This is immediately followed by a so-called instrument operational amplifier (not shown). This is capable of subtracting another signal from its input signal and then further amplifying it.

[0078] The amplitude values ​​of the subtract signal for the two line image sensors 11, 11' assigned to the X position and the Y position are continuously recalculated by the at least one controller 15 based on the current output data of the two line image sensors 11, 11' and then sent to a digital-to-analog converter assigned to a respective one of the two line image sensors 11, 11' synchronously with the readout of the two line image sensors 11, 11' so that the instrument operational amplifier can subtract this signal. This first background image data is created by the position detection device 1 for both line image sensors 11, 11' in a first "dark image" (dark slice) in the memory 18.When creating this dark slice in memory 18, which, in the time-multiplexing process, preferably lies before the first used time window, no light source device 20 to 2N may be active, except for ambient light or light reflected from the projection surface. It serves to record a first background image. The image data of this dark slice also includes the brightness values ​​of the irradiation of the sensors (particularly from the internal light sources 14, 14'), which, of course, must also be subtracted.

[0079] Since the above measures lead to permanent corruption of the image data, these systems must be readjusted. This occurs within the framework of a second "dark image" (DarkSlice2), which the position detection device 1 creates for both line image sensors 11, 11' in the memory 18. In this DarkSlice2, which, in the time-multiplexing process, preferably lies before the first used time window but after the DarkSlice, no light source device 20 to 2N may be active, except for ambient light or light reflected from the projection surface. It serves to record another background image, the data for the line image sensors 11, 11' of which is stored in the microcontroller's memory and subtracted from the current data of the line image sensors 11, 11' in the respective used time window of the light source device 20 to 2N.

[0080] The second "dark image" (DarkSlice2) is also important because the individual pixels in the line image sensors 11, 11' do not have identical values ​​for the photoenergy to voltage ratio (pixel nonuniformity), and the top surface of the line image sensors 11, 11' may contain impurities. However, since these differences exist not only in the used time windows, but also in DarkSlice2, these errors are also removed by subtraction. Errors caused by subtracting the DarkSlice in the instrument operational amplifier and jumps in the digital-to-analog converter are also removed. The corrected data from the line image sensors 11, 11' of the used time windows then pass through a low-pass filter from left to right and then from right to left (or vice versa). A nice symmetrical curve is obtained for each of the two line image sensors 11, 11', which is shown in Figure 9.

[0081] Subsequently, the at least one controller 15 determines the mean value of the signal processed as above and shown in Figure 9 for each of the two line image sensors 11, 11'. This can be done, for example, by drawing a straight line at, for example, 80% of the maximum value of the signal and then determining the midpoint between the two intersection points between the straight line and the signal (and thus the curve shown in Figure 9). Due to the low-pass filter, a value averaged over several pixels is obtained for both line image sensors 11, 11'.

[0082] To distinguish between different light source devices 20 to 2N, a time-division multiplexing method can be used, as in the prior art. With all optimizations, this method, according to the invention, looks as shown in Figure 10.

[0083] The synchronous data packet S sent by position detection device 1 is followed by DarkSlice (DS1), followed by DarkSlice2 (DS2). In both cases, no light source device 20 to 2N is active. In time slot F00, light source device 20 transmits, and in the subsequent time slots, light source device 21 transmits up to light source device 299.

[0084] The final number 99 for the light source device is only an example; for shorter time windows, there can also be 1,000 light source devices or more. Figure 11 shows an alternative arrangement of the sensor surfaces 12, 12' of the two line image sensors 11, 11' according to the invention. This alternative arrangement allows the sensor surface of each line image sensor to be composed of several sub-sensor surfaces ZS0 to ZS3, wherein the sub-sensor surfaces ZS0 to ZS3 can be arranged in overlapping parallel rows.

[0085] The partial overlap prevents dark zones. After the completion of the position detection device 1, the overlaps can be determined by "running over" the entire distance L with an LED (not shown) for the two line image sensors assigned to the X-direction and the Y-direction and can be permanently stored in the (non-volatile) memory 18 of the position detection device 1. This step can be omitted if it is otherwise ensured that the output voltages of the individual (particularly overlapping) line image sensors are not added together. It may also be possible to omit determining the overlap by measuring by "running over" the entire distance L with an LED.

[0086] By changing the distance between the slit diaphragm and the line scan sensors, the aperture angle of each line scan sensor can also be individually adjusted. In the figures discussed above, this aperture angle was shown as + / - 45 degrees. The aperture angle also directly controls the resolution of the position detection device 1, as well as the length of the line scan sensors and the number of pixels per line scan sensor.

[0087] In the variant of Figure 11, several line image sensors can also be mounted at different angles according to the invention, so that the line image sensors located further out are mounted higher and higher on the outermost side. Such an effect could also be achieved with flexible line image sensors. Such an arrangement has the advantage that the incident light does not fall at an extremely steep angle (45 degrees) onto the surface of the line image sensor and / or a filter arranged above the line image sensor. Partial reflection can thus be reduced, and the interference bandpass filter can thus be implemented with a narrower band. However, the same effect can also be achieved using a linear Fresnel lens mounted on the line image sensors.

[0088] Detecting a respective light source device according to the time-division multiplexing method described above requires that the light flashes generated by the light source devices 20 to 2N be synchronized with the position detection device 1. In the case of multiple position detection devices 1, one position detection device is the timing transmitter, and the other position detection devices—like the light source devices 20 to 2N (or the microcontrollers contained therein)—are timing receivers. Position detection devices that are timing receivers can also be timing transmitters; however, in this case, each position detection device transmits at different times with specially marked data packets that identify the position detection device as an additional timing transmitter.The use of several position detection devices operating as time-lock transmitters can be advantageous if, in large installations, one position detection device cannot cover the entire space to be detected with radio.

[0089] In principle, it would be conceivable to use precision quartz crystals in both the position detection device and the microcontrollers of the light source devices 20 to 2N, which achieve an accuracy of, for example, 5 ppm. However, even these already run 5 microseconds outside the specified time window after 1 second. Since the inventive solution is intended to obtain at least 10,000 values ​​per second from the two line image sensors assigned to the X position and the Y position, a time window for one value is 100 microseconds long. To prevent overlap from one time window into the next adjacent time window, in one example the duration of a light flash emitted by the light source devices 20 to 2N can be set to 96 microseconds and a safety distance to 4 microseconds.The synchronization between the position detection device and the light source devices 20 to 2N as well as between the light source devices 20 to 2N must therefore be better than + / - 2 microseconds.

[0090] This problem could be solved with wired synchronization, but this is associated with the disadvantages mentioned above.

[0091] According to the invention, the following solutions are therefore proposed:

[0092] 1. Synchronization with light pulses

[0093] 2. Synchronization with radio signals

[0094] For synchronization with light pulses, the time of the end of an optical carrier wave, for example, at 455 kHz, can be detected. For this purpose, corresponding receivers are installed in the light source devices 20 to 2N and connected to the associated controllers. Furthermore, the position detection device has a corresponding emitter for the carrier wave.

[0095] For synchronization with radio signals, radio, and in particular the 2.4 GHz band (DECT, Wi-Fi, Bluetooth, etc.), can be used. However, any other permissible radio band can also be used. The problem with using conventional chips to provide synchronization with radio signals is that these systems have built-in functions designed to guarantee the error-free nature of the transmitted data and can even trigger and independently perform the repetition of data packets in the event of an error. However, this leads to an unpredictable, fluctuating time at which a data packet is deemed to be received and ready for pickup.

[0096] To solve this problem, the use of special transmit and receive controllers in the wireless communication interfaces 17 in the position detection device, as well as the corresponding interfaces of the light source devices, is proposed. After each data packet, a short synchronous pattern initiated by the controller 18 of the position detection device is modulated onto the carrier wave (e.g., 2.4 GHz), which is still active without data. The receive controller waits a short time after each data packet to see if such a synchronous pattern appears on the carrier wave. Immediately at the end of the synchronous pattern, a signal is generated that stores a timer value in the microcontroller or, preferably, stores a timer value internal to the receive controller, which can be read out after the data has been decoded and verified.This reduces the jitter (time fluctuations) of the synchronization to less than 100 nanoseconds.

[0097] As an alternative to the use of dedicated transmit and receive controllers, the invention proposes the use of an existing precursor to Bluetooth chips, in which all protocol functions such as CRC detection, etc., are disabled, and a "ready to pick up" signal is emitted immediately after the last bit transmitted on the carrier wave. This signal exhibits almost no jitter. The microcontroller remembers the time of the internal timer and only then decodes the received data, including error detection and verifying whether the data was actually sent by the associated position detection device. This verification is necessary because there are many other transmitters in the 2.4 GHz band.

[0098] Once the received radio signal has been verified to be error-free and the transmitter has been qualified, the transmission end time is compared with the time an internal timer should have (reference constant). If the measured time is behind the reference constant, the respective microcontroller (or its timer) is too fast; if the measured time is ahead of the reference constant, the respective microcontroller (or its timer) is too slow.

[0099] To adjust the speed, it would theoretically be possible to simply slow down or speed up the oscillator of the respective microcontroller or its timer. This is either not possible with quartz-based microcontrollers or is very complex. With RC oscillators, which are preferred for cost reasons, speed adjustment is possible, but in much too coarse steps. Furthermore, RC oscillators change their speed depending on voltage and temperature.

[0100] According to the invention, it is therefore proposed that, upon detection of a time discrepancy between the clock signal received via radio and an internal clock signal, not the speed of the oscillator be changed, but rather the time constants at which the microcontroller is to perform certain tasks, such as switching the light sources of the light source devices on or off. These constants are stored in a table in the internal memories of the light source devices and are recalculated by the controllers of the light source devices after each time comparison.

[0101] These constants also define a time window in which the position detection device controllers and the light source device controllers send the next synchronization packet including

[0102] Safety distance can be expected, which leads to an additional reduction of errors caused by “false transmitters” that are not part of the position detection system according to the invention.

[0103] A further improvement proposed according to the invention is the use of two or more wireless communication interfaces 17 in the position detection device. Since the 2.4 GHz band is used by many device types (DECT, WLAN, Bluetooth, etc.), it must be ensured that sufficient synchronous data packets can be transmitted error-free. Since each transmitter in the 2.4 GHz band first determines whether a channel (80 frequencies in the 2.4 GHz band) is free before it is allowed to transmit, a wireless communication interface blocks the channel with a single (first) data packet, the end time of which is known in the position detection device. For this data packet, it is irrelevant whether it is received by the light source devices or not; it is marked accordingly in the data and, if error-free, is evaluated at the receiving end as the first (synchronous) data packet and discarded in the event of an error.In any case, the second (synchronous) data packet is sent from the second wireless communication interface directly after the first (synchronous) data packet and marked as a second synchronous data packet. This will be received with a high probability by the light source devices, unless the channel is intentionally jammed, e.g., with a continuous transmitter. This improvement (the use of two wireless communication interfaces) can of course be implemented in a single module. Alternatively, two wireless communication interfaces can be used, the start signals of which are generated by one of the position detection device's controllers directly depending on its internal timer.

[0104] In addition, command packets are sent at predetermined times from the position detection device to the controllers (microcontrollers) of the light source devices 20 to 2N, so that users can, for example, feel different vibration patterns depending on the actions they have triggered. In addition to vibration, sound sequences, voice sequences, etc. are also possible. For this purpose, the light source devices 20 to 2N are equipped with corresponding vibration motors, loudspeakers, or displays (which are not shown).

[0105] In addition, the invention provides for commands from the position detection device to the light source devices that set the number of light flashes per second to a maximum value. If such commands are not received, the controllers (microcontrollers) of the light source devices 20 to 2N automatically reduce the flashing frequency of the light sources 20 to 2N. Only when the light source devices 20 to 2N generate light flashes in the projection area / viewing area are these commands regularly sent from the position detection device to the individual light source devices 20 to 2N, which results in a significant decrease in light energy when the light source devices 20 to 2N are pointed elsewhere.

[0106] According to the invention, all data packets are transmitted by the position detection device with different transmission powers, preferably initially with low transmission power and then repeatedly transmitted with increasing transmission power. Packet numbering allows the controllers (microcontrollers) of the light sources 20 to 2N to determine whether a data packet has not already been received with low transmission power. In this case, the controllers (microcontrollers) of the light source devices 20 to 2N discard the duplicates.

[0107] The different transmission powers are necessary because the distance between the position detection device and the controllers (microcontrollers) of the light source devices 20 to 2N is unknown. Controllers (microcontrollers) of the light source devices 20 to 2N whose receiver antennas are close to the position detection device will already receive the low-power data packets and may not even be able to receive the subsequent higher-power data packets at all because an amplifier in the receiver of the light source device is overdriven. Therefore, it is proposed to initially transmit with a low transmission power and then increase it.Controllers (microcontrollers) of the light source devices 20 to 2N, whose receiver antennas are further away from the position detection device, do not receive the low-power data packets at all, but do not override them either and wait for the higher-power data packets that match their distance.

[0108] According to the invention, the transmission of the status of buttons (not shown) or other status information of the light source devices 20 to 2N also occurs during the light flash, and with a larger number of bits, also shortly after the light flash, but at a high frequency and with short ON times and long OFF times, which have almost no influence on the line image sensors, since photoelements always integrate the light output over time. A special photosensor 19 in the position detection device 1, which can amplify this high frequency and filter it out from a mixture of interfering light pulses (remote controls, fluorescent lamps, etc.), "views" the entire projection surface or the entire 3D space. Since the time at which the position light flashes are generated is known to the position detection device, the times at which data bits must be transmitted to the position detection device are also known to within + / - 2 microseconds.

[0109] At these times, the amplifier's output signal is decoded, and the data is transmitted to a computer connected to the position detection device, individually for each light source device (20 to 2N). By using the same transmission method (modulated light flash) for the position and the button status, a 100% correlation between position and button press is achieved, which is only possible with a mixed variant (position light, button radio) with considerably greater effort.

[0110] To adapt the position detection system to daylight, appropriate filters can be mounted on the sensors. In particular, a so-called interference bandpass filter can be used, which allows an extremely narrow wavelength band to pass through while filtering out almost 100% of the rest of the light spectrum.

[0111] The wavelength band of the interference bandpass filter depends on the angle of incidence of the light. The interference bandpass filter is selected so that it transmits the wavelength of the transmitters used in the wireless communication interfaces, even with light incident at an angle of + / - 45 degrees (relative to 0 degrees perpendicular). The invention further proposes using a combination of a narrow interference bandpass filter and a lens, preferably a Fresnel lens or a nano-lens, which is simply considerably flatter and more precise and is mounted directly in front of the filter, directing the obliquely incident light almost straight.

[0112] Such a lens, preferably a Fresnel lens or a nanolens, can also be constructed to replace the slit aperture or to "collect" significantly larger amounts of light energy before the light is directed onto the slit aperture and to the line scan sensor behind it. In this case, the image is simply reduced in size, as in a light-sensitive telescope, where the front lens should have the largest possible diameter.

[0113] A corresponding Fresnel lens is shown schematically in Figure 12.

[0114] The Fresnel lens collects more light in one direction, but does not change the angle of the incident light in the other direction (the direction of the sensor). The line scan sensor is located along the focal line of the linear Fresnel lens and forms an angle of preferably 90° with the focal line.

[0115] The longitudinal extension of the Fresnel lens is oriented in the same way as the longitudinal extension of a slit diaphragm assigned to a respective line image sensor.

[0116] According to the invention, it is further proposed to use the position detection device to detect the position of light points in space and to identify the respective light points. In order to be able to use the position detection system for position detection in 3D space, at least two position detection devices, as described above, must detect a respective light flash generated by a light source device from different angles. For this purpose, the at least two position detection devices can be mounted, for example, on the ceiling of a room. Using simple linear equations in space, the position of the light source device emitting the light flash is calculated in 3D space from the two pairs of XY coordinates determined by the position detection devices.

[0117] When using laser pointers as a light source, an additional LED flash is attached to the laser pointer so that the position detection devices can detect the laser pointer's position in space. Combined with the X / Y coordinate on the projection surface, which results from the spot of light created by the laser pointer on the projection surface, and the position of the laser pointer in 3D space determined from the LED flash, the laser beam path in 3D space can be calculated using simple linear equations in space.

[0118] Preferably, more than two position detection devices are used to determine the position in space, so as to reduce the probability that other people or objects in the same space will block the "view" between a position detection device and a light source device whose position is to be detected. Since the position detection devices transmit an "offscreen" status, the pairs that are valid, i.e. those reported with a correspondingly high amplitude, can always be used. According to the invention, it is further proposed not to use a single light source (e.g. LED) in the light source device as the transmitter of an (LED) light flash, but preferably several light sources (e.g. LEDs) per light source device, which emit with a smaller aperture angle but thereby generate a considerably higher light energy per steradian.Furthermore, the invention proposes not to flash these different light sources in the light source device at the same time, but to assign different time windows to the light sources. Depending on which light sources are detected, the orientation of the light source device and the orientation of an object to which the light source device is attached can also be detected.

[0119] The proposed use of LEDs as a light source for the light source devices is also particularly advantageous because, since LEDs can transmit significantly higher pulse currents than laser diodes (for safety reasons), it is possible to increase the distance between LEDs and position detection devices and / or shorten the time windows, allowing significantly more light flashes from different light sources and thus different light source devices to be detected. This allows either more objects / people to be detected, or more tracking points per object / person.

Claims

Patent claims 1. A position detection system comprises: at least one position detection device (1); and at least one light source device (20 to 2N) which is different from the position detection device (1); wherein each light source device (20 to 20N) is designed to generate a light spot spaced from the at least one position detection device (1); the at least one position detection device (1) comprises at least two line image sensors (11, 11'), each with sensor surfaces (12, 12') arranged along a line, wherein the extension directions of the rows of sensor surfaces (12, 12') of the two line image sensors (11, 11') enclose an angle of greater than 0° and preferably 90° with one another; a slit diaphragm (13, 13') is provided above each line image sensor (11, 11') such that the slit diaphragm (13, 13') encloses an angle of greater than 0° and preferably 90° with the associated line of sensor surfaces (12, 12');the at least one position detection device (1) and the at least one light source device (20 to 2N) each have interfaces for wireless communication, via which the at least one position detection device (1) and the at least one light source device (20 to 2N) are synchronized in time in order to enable position detection of a light spot generated by a respective light source device (20 to 2N) by a time-multiplex method when light is emitted by the at least one light source device (20 to 2N); 2. Position detection system according to claim 1, comprising a plurality of position detection devices (1) which are designed to detect light points generated by the at least one light source device (20 to 2N) from different angles, wherein the position detection system is designed to calculate the position of the at least one light source device (20 to 2N) in 3D space based on XY coordinates for the position of the light points output by the respective position detection device (1).

3. Position detection system according to claim 1 or 2, wherein the at least one light source device (20 to 2N) has keys and is designed to transmit the state of each key and / or status information as data bits modulated onto at least one light spot emitted by the at least one light source device (20 to 2N), and wherein the at least one position detection device (1) has a photosensor (19) and is designed to receive the data bits sent by the at least one light source device (20 to 2N) in the at least one modulated light spot, wherein an assignment of the data bits to an individual light source device (20 to 2N) is carried out by the time-division multiplex method.

4. Position detection system according to one of claims 1 to 3, wherein the at least one position detection device (1) is designed to send data packets to the at least one light source device (20 to 2N) via the interfaces for wireless communication, wherein the data packets are initially sent with low transmission power and then repeatedly sent with increasing transmission power, wherein a packet numbering of the data packets allows the at least one Light source device (20 to 2N) enables to determine whether a data packet has already been received with low transmission power, and the at least one light source device (20 to 2N) is designed to discard duplicates after receiving a data packet.

5. Position detection system according to one of claims 1 to 4, wherein the at least one position detection device (1) is designed to regularly send a command to a light source device (20 to 2N) via the interfaces for wireless communication upon detection of a light spot of this light source device (20 to 2N), which command causes the light source device (20 to 2N) to set a number of light spots per second to a maximum value, wherein the at least one light source device (20 to 2N) is designed to regulate the frequency of light spots per second generated by the respective light source device (20 to 2N) down from a maximum value, provided that no further command is received from the at least one position detection device (1) to set the number of light spots generated per second to a maximum value.

6. Position detection system according to one of claims 1 to 5, wherein the at least one light source device (20 to 2N) has at least one vibration motor and / or at least one loudspeaker and / or at least one display, wherein the at least one position detection device (1) is designed to send commands for activating the at least one vibration motor and / or the at least one loudspeaker and / or the at least one display of a respective light source device (20 to 2N) via the interfaces for wireless communication, and wherein the at least one light source device (20 to 2N) is designed to receive commands received from the at least one position detection device (1) via the interfaces for wireless communication for activating the at least one vibration motor and / or the at least one loudspeaker and / or the at least one display and to activate the at least one vibration motor and / or the at least one loudspeaker and / or the at least one display accordingly.

7. Position detection system according to one of claims 1 to 6, wherein the at least one position detection device (1) is designed to block a channel by means of the wireless communication interface (17) by sending a first data packet, the transmission duration and thus the end time of which is known in the at least one position detection device (1) and the transmission duration of which is known in the at least one light source device (20 to 2N), and which first data packet contains a current time of the position detection device (1) and is identified as a first data packet, and to send a second data packet directly after the end time of the first data packet, which second data packet contains a current time of the position detection device (1) and is identified as a second data packet, wherein the at least one light source device (20 to 2N) is designed,to use the time of the position detection device (1) contained in the first data packet as the zero point for synchronization in the multiplex method, provided that the first data packet can be received, and the at least one light source device (20 to 2N) is designed to use the time of the position detection device (1) contained in the second data packet less the transmission duration as the zero point, to be used for synchronization in multiplex mode, provided that the second data packet can be received.

8. Position detection system according to one of claims 1 to 7, wherein the at least one light source device (20 to 2N) is designed to generate an internal clock signal, to determine a clock deviation by comparison with a clock signal received from the at least one position detection device (1), and upon detection of a deviation, to recalculate a time constant defined in the at least one light source device (20 to 2N) for switching the at least one light source device (20 to 2N) on and off based on the clock deviation and to use these newly calculated time constants for switching the at least one light source device (20 to 2N) on and off.

9. Position detection system according to one of claims 1 to 8, wherein the at least one interface for wireless communication (17) in the at least one position detection device (1) is designed to modulate a synchronous pattern started by a controller (18) of the position detection device (1) after a data packet on a carrier wave which is then still active without data, and wherein the interface for wireless communication (17) in the at least one light source device (20 to 2N) is designed to wait a short time after each data packet to see whether such a synchronous pattern appears on the carrier wave and to store an internal timer value immediately at the end of the synchronous pattern, which timer value is read out after the decoding and checking of the actual data packet and is used to synchronize the time-division multiplexing method.

10. Position detection system according to one of claims 1 to 9, wherein the sensor surface of each line image sensor of the at least one position detection device (1) is composed of a plurality of partial sensor surfaces (ZSO to ZS3), wherein the partial sensor surfaces (ZSO to ZS3) are arranged with overlap in mutually parallel rows.

11. Position detection system according to claim 10, wherein the overlaps of the line image sensors of the at least one position detection device (1) are determined by measuring by traveling over a total distance (L) of the respective line image sensor with an LED, are permanently stored in a non-volatile memory (18) of the at least one position detection device (1) and are taken into account in the position detection.

12. Position detection system according to one of claims 1 to 11, wherein a linear Fresnel lens is arranged above the line image sensors of the at least one position detection device (1).

13. Position detection system according to one of claims 1 to 12, wherein the position detection system comprises a plurality of position detection devices (1), and wherein, for the purpose of synchronization in the multiplex method, one position detection device of the plurality of position detection devices (1) is designed as a time clock transmitter and the other position detection devices are designed as time clock receivers.

14. Position detection system according to one of claims 1 to 12, wherein the position detection system comprises a plurality of position detection devices (1), and wherein, for the purpose of synchronization in the multiplexing process, each position detection device transmits at different times with specially marked data packets which allow the position detection device to be recognized as an additional clock transmitter.

15. Position detection system according to one of claims 1 to 14, wherein the at least one position detection device (1) further comprises an instrument operational amplifier which is designed to subtract another signal from its input signal, wherein the instrument operational amplifier receives as an input signal a signal output by the line image sensors (11, 11') of the at least one position detection device (1) and as a signal to be subtracted a subtract signal stored in a memory (18) of the at least one position detection device (1), wherein the subtract signal is obtained from an output signal of the line image sensors (11, 11') of the at least one position detection device (1) when none of the light source devices (20 to 2N) is active.

16. Position detection system according to one of claims 1 to 15, wherein the at least one position detection device (1) has internal light sources (14, 14') connected to a controller (15) of the position detection device (1), which are designed to irradiate the sensor surfaces (12, 12') of the line image sensors (11, 11') of the at least one position detection device (1) under the control of the controller (15).

17. Position detection system according to claim 16, wherein the internal light sources (14, 14') are designed, controlled by the controller (15), to cause a voltage amplitude of pixels of the line image sensors (11, 11') by irradiating the sensor surfaces (12, 12') of the line image sensors (11, 11'), the magnitude of which is lowest for pixels in the center of the line image sensors (11, 11') and highest for pixels at the outermost edges of the line image sensors (11, 11') when no additional light is incident on the line image sensors (11, 11') through the slit diaphragms (13, 13'), and / or wherein the internal light sources (14, 14') are designed, controlled by the controller (15), to cause a voltage amplitude of pixels of the line image sensors (11, 11') by irradiating the sensor surfaces (12, 12') of the line image sensors (11, 11 ') to cause a voltage amplitude of pixels of the line image sensors (11, 11'), which voltage amplitude has a U-shaped curve with the bottom of the U in the middle of the respective line image sensor (11,11 ') and the leg ends of the U at the outermost edges of the respective line image sensor (11, 11') when the pixels of the line image sensors (11, 11 ') are read out sequentially and the voltage values ​​are plotted over the arrangement of the pixels., 18. Position detection system according to one of claims 16 or 17, wherein the internal light sources (14, 14') are either provided between the sensor surfaces (12, 12') of the line image sensors (11, 11') and the associated slit diaphragms (13, 13') and are directed directly onto the sensor surfaces (12, 12') of the line image sensors (11, 11'), or are provided next to the line image sensors (11, 11') on a board carrying the line image sensors (11, 11') and are designed to radiate onto a plate (13P) in which the Slit diaphragms (13, 13') are formed, wherein the plate (13P) diffusely reflects the light emitted by the internal light sources (14, 14') onto the sensor surfaces (12, 12').

19. Position detection system according to claim 18, wherein the plate (13P) is provided with a white diffuse reflector (131) on its side facing the line image sensors (11, 11') next to the respective slit diaphragm (13, 13').

20. Position detection system according to one of claims 16 to 19, wherein the light emitted by the internal light sources (14, 14') has the same wavelength as the light emitted by the at least one light source device (20 to 2N).

21. Position detection system according to one of claims 16 to 20, wherein the controller (15) of the at least one position detection device (1) uses an output signal of the line image sensors (11, 11') for controlling the internal light sources (14, 14'), which output signal is obtained when the internal light sources (14, 14') are active but none of the light source devices (20 to 2N) is active, and the controller (15) controls the internal light sources (14, 14') such that all sensor surfaces (12, 12') of the line image sensors output a signal which is above the dark voltage of the respective sensor surface.

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