Data light barrier

Abstract

Data light barrier (1) with at least one light beam emitting transmitter (4) in a first unit (2) and at least one receiver (7) in a second unit (6) spaced apart from the first unit (2), wherein data is transmitted from the transmitter (4) to the receiver (7) by means of the light beams (3), characterized in that an electrically controllable attenuating device (14) is arranged upstream of the receiver (7), by means of which an adjustable attenuation of the light beams (3) is effected.

Description

[0001] The invention relates to a data light barrier.

[0002] Such a data light barrier represents a device for optical free-space data transmission.

[0003] In a minimal configuration, the data light barrier enables unidirectional data transmission. In this case, a light-emitting transmitter is located in the housing of a first unit. A laser diode is typically used as the transmitter. Furthermore, a receiver is located in a second unit, housed in a separate enclosure, at a distance from the first unit.

[0004] The light beams from the transmitter are imprinted with codes containing the data to be transmitted. These light beams are received by the receiver. The resulting received signals, which contain the codes from the light beams, are decoded to recover the data to be transmitted.

[0005] The data light barrier is advantageously extended to enable bidirectional data transmission. Each unit then integrates a transmitter and a receiver. The light beams from the transmitter of one unit are then transmitted to the receiver of the other unit.

[0006] In typical applications of optical free-space data transmission, the distances between units can vary considerably. This is particularly true when data transmission is required between vehicles, such as stacker cranes, and stationary units or other vehicles.

[0007] The highly varying distances between the units of the data light barrier result in a high signal dynamic, i.e., the amplitudes of the received signals fluctuate over a wide range.

[0008] To address this problem, it is known to adjust the transmission power of at least one transmitter to compensate for the signal dynamics at the receiver. However, this requires an additional communication device to transmit the current amplitude of the receiver to the second unit containing the transmitter, so that the transmitter's transmission power can then be adjusted to match the amplitude of the receiver in the opposite unit. In known data light barriers such as the DDLS 500 from Leuze electronic, a miniframe within an interframe gap is used as the communication device.

[0009] However, this requires a significant increase in the design effort of the data light barrier. In particular, a netX51 system is used for the aforementioned communication device, which is relatively expensive. If the additional communication uses standard Ethernet frames, this reduces the data throughput of the media converter.

[0010] Another disadvantage is that, during short-range data transmission, the laser diode forming the transmitter must be operated just above the laser threshold to prevent the amplitudes of the received signals from becoming so large that the receiver's amplifier is driven so hard that signal distortion occurs. Maintaining this operating point of the laser diode is difficult. Furthermore, even with this operating point, there is still a risk of the aforementioned overdriving.

[0011] The invention is based on the objective of providing a data light barrier of the type mentioned above, in which a secure optical free-space data transmission is ensured even with data transmission distances of greatly different lengths.

[0012] The features of claim 1 are provided to solve this problem. Advantageous embodiments and expedient further developments of the invention are described in the dependent claims.

[0013] The invention relates to a data light barrier with at least one light-beam emitting transmitter in a first unit and at least one receiver in a second unit spaced apart from the first unit, wherein data is transmitted from the transmitter to the receiver by means of the light beams. An electrically controllable attenuator is arranged upstream of the receiver, by means of which adjustable attenuation of the light beams is effected.

[0014] The basic idea of ​​the invention is therefore to counteract signal dynamics on the receiver side caused by application-specific variations in the distances between transmitter and receiver of the data light barrier by means of an electronically controllable damping device placed upstream of the receiver.

[0015] The electronically controlled damping device continuously adjusts the attenuation of the light beams so that even with highly varying distances between the transmitter and receiver of the data light barrier, a consistently safe and reliable optical free-space data transmission is maintained.

[0016] Data transmission is optimized solely by means of the electronically controlled attenuator. No variation in the transmitter's power is required. Instead, all settings are configured within the data light barrier unit containing the receiver. This eliminates the need for an additional communication device that would be required to control the transmitter's power based on receiver parameters, thus significantly reducing the design complexity of the data light barrier.

[0017] A key aspect of the invention is that the damping of the electronically controllable damping device is predetermined depending on the amplitude of a received signal present at the output of the receiver.

[0018] The electronically controlled attenuation device allows the amplitude of the received signal to be adjusted quickly and without delay in order to compensate for distance-dependent received signal dynamics.

[0019] In particular, the damping of the electronically controlled damping device is adjusted so that the receiver is operated at a favorable operating point.

[0020] The electronically controlled attenuator can be set to low attenuation values ​​even when the distance between transmitter and receiver is very large. This ensures that the amplitude of the received signal is still large enough to guarantee reliable data transmission.

[0021] Furthermore, the electronically controlled attenuator can be set to high attenuation values ​​when the distance between transmitter and receiver is small. This prevents overloading of the receiver or a downstream receiver amplifier and the resulting signal distortions that can lead to errors in data transmission.

[0022] A key advantage of the invention is that the compensation of the received signal dynamics can be performed solely with the receiving components of the data light barrier. Varying the transmitter's transmit power is not required.

[0023] This allows the transmitter to be operated with constant transmission power.

[0024] This significantly simplifies the operational control of the data light barrier.

[0025] If the transmitter is formed by a laser diode, it can be operated constantly at a stable, favorable operating point.

[0026] Advantageously, the damping of the electronically controlled damping device is specified via a control element.

[0027] In particular, the control element is used to regulate the amplitude of the received signals to a target value.

[0028] The control element can be formed by a separate component or assembly.

[0029] Alternatively, the control element can also be part of an evaluation unit that serves to evaluate the receiver's received signals.

[0030] Data transmission takes place in such a way that the data light barrier has a transmitter control unit assigned to the transmitter, by means of which data-containing encodings are imprinted on the light beams of the transmitter.

[0031] The decoding of received light rays, i.e., the received signals obtained thereby, then takes place in the evaluation unit assigned to the receiver.

[0032] According to a first advantageous embodiment, the electronically controllable damping device comprises a plastic film coated with electrically conductive material.

[0033] Alternatively, the electronically controlled damping device features a liquid crystal element.

[0034] In any case, it is advantageous if the electronically controlled damping device is located directly upstream of the receiver.

[0035] This means that the electronically controlled damping device acts directly on the light-sensitive surface of the receiver.

[0036] The electronically controlled damping device is advantageously arranged between the receiver and a receiving optic.

[0037] According to a structurally advantageous design, both units are integrated into one housing.

[0038] In a minimal configuration, the data light barrier enables unidirectional data transmission. In this configuration, the first unit contains only a transmitter and the second unit only a receiver as optoelectronic components.

[0039] The data light barrier according to the invention is particularly advantageously designed for bidirectional data transmission.

[0040] In this case, each unit contains a transmitter and a receiver. The light beams from one transmitter are sent from one unit to the receiver of the other unit.

[0041] Each receiver is assigned an electronically controlled damping device.

[0042] In principle, both units can be identical in construction.

[0043] To avoid mutual interference between the two data transmission paths, the units of the data light barrier can differ in that their transmitters emit light beams with different wavelengths.

[0044] Another disadvantage of identical data light barrier units is the so-called lens reflector effect. This effect arises because the receiving optics of one unit act as a lens reflector, reflecting the light rays from the other unit back towards it.

[0045] If the two units are positioned close to each other and one of the units is switched off, light rays reflected at the receiving optics of the switched-off unit are reflected back to the still switched-on unit and generate significant amounts of erroneous data there.

[0046] To prevent this, the data packets transmitted with the light beams can be provided with a preamble bit, which allows a distinction to be made as to which unit the data packets originate from.

[0047] The invention will be explained below with reference to the drawings. The drawings show: Fig. 1: First configuration of the data light barrier according to the invention. Fig. 2: Second configuration of the data light barrier according to the invention. Fig. 3: Block diagram of a data light barrier unit according to Fig. 2.

[0048] Fig. Figure 1 shows a highly schematic first configuration of the data light barrier 1 according to the invention. This data light barrier 1 is designed for unidirectional optical free-space data transmission, hereinafter referred to as data transmission.

[0049] The data light barrier 1 has a first unit 2 with a first housing 2a, in which a light beam 3 emitting transmitter 4 and a transmitter control unit 5 are integrated. The transmitter 4 is formed by a laser diode.

[0050] The data light barrier 1 further comprises a second unit 6, located remotely from the first unit 2, with a second housing 6a, in which a receiver 7 and an evaluation unit 8 are integrated. The receiver 7 is, for example, formed by a photodiode, and the evaluation unit 8 consists of a microcontroller or the like.

[0051] The transmitter control 5 imprints 3 codes on the light beams emitted by the transmitter 4, which contain data to be transmitted.

[0052] The receiver 7 receives the light beams 3 from the transmitter 4. The resulting received signals at the output of the receiver 7 contain the codes that are decoded in the evaluation unit 8, thereby obtaining the data.

[0053] Fig. Figure 2 shows a second configuration of the data light barrier 1 according to the invention. This data light barrier 1 is designed for bidirectional data transmission.

[0054] The data light barrier 1 according to Fig. 2 again features two remotely arranged units 2, 6, each with a housing 2a, 6a.

[0055] Each unit 2, 6 contains a light beam 3 emitting transmitter 4 and a receiver 7, which are connected to a control and evaluation unit 9. The control and evaluation unit 9 fulfills the functions of the transmitter control 5 and the evaluation unit 8 of the configuration according to Fig. 1.

[0056] The light rays 3 of the transmitter 4 of a unit 2 or 6 are each sent to the receiver 7 of the respective other unit 6 or 2.

[0057] Fig. Figure 3 shows a block diagram of the first unit 2 of the data light barrier 1 according to Fig. 2. The second unit 6 is identical in construction.

[0058] As from Fig. As can be seen in section 3, a connection unit 10 is connected to the control and evaluation unit 9, via which decoded data can be output to an external unit.

[0059] Transmitter 4 is preceded by a transmitter electronics unit 11, which is part of the transmitter control unit 5.

[0060] Transmitter 4 is associated with a transmitting optic 12, which serves to shape the emitted light rays 3. Receiver 7 is associated with a receiving optic 13, which serves to focus the light rays 3 emitted by the second unit 6.

[0061] According to the invention, an electronically controllable damping device 14 is arranged upstream of the receiver 7, by means of which an electrically adjustable damping of the incident light rays 3 can be effected.

[0062] The electronically controlled damping device 14 is located directly upstream of the receiver 7 and is situated between the receiver 7 and the receiving optics 13.

[0063] The electronically controllable damping device 14 consists of a plastic film coated with electrically conductive material or of a liquid crystal element.

[0064] The electronically controlled damping device 14 is controlled by a control element 15, i.e. the damping of the electronically controlled damping device 14 is specified via the control element 15.

[0065] An identical arrangement with the electronically controllable damping device 14 and the control element 15 is also used in the data light barrier 1 according to Fig. 1 available.

[0066] The operation of this arrangement is such that the attenuation of the electronically controllable attenuating device 14 is predetermined depending on the amplitude of a received signal present at the output of the receiver 7.

[0067] The damping of the electronically controlled damping device 14 is adjusted so that the receiver 7 is operated at a favorable operating point.

[0068] In particular, the amplitude of the received signals is regulated to a setpoint value by means of the control element 15.

[0069] This allows the signal dynamics of the received signals to be compensated for due to varying distances between the two units 2, 6.

[0070] A variation in the transmission power of transmitter 4 is not necessary. Rather, transmitter 4 can be operated with a constant transmission power. Reference symbol list 1 Data light barrier 2 units 2a Housing 3 light beam 4 transmitters 5 Transmitter control 6 units 6a Housing 7 recipients 8 evaluation units 9 Control and evaluation unit 10 connection unit 11 Transmitting electronics 12 transmitting optics 13 Reception optics 14 electronically controlled damping devices 15 Control element

Claims

Data light barrier (1) with at least one light beam emitting transmitter (4) in a first unit (2) and at least one receiver (7) in a second unit (6) spaced apart from the first unit (2), wherein data is transmitted from the transmitter (4) to the receiver (7) by means of the light beams (3), characterized in that an electrically controllable attenuating device (14) is arranged upstream of the receiver (7), by means of which an adjustable attenuation of the light beams (3) is effected. Data light barrier (1) according to claim 1 , characterized in that the electronically controllable damping device (14) has a plastic film coated with electrically conductive material. Data light barrier (1) according to claim 1 , characterized in that the electronically controllable damping device (14) has a liquid crystal element. Data light barrier (1) according to one of claims 1 to 3, characterized in that the electronically controllable damping device (14) is arranged directly upstream of the receiver (7). Data light barrier (1) according to claim 4, characterized in that the electronically controllable damping device (14) is arranged between the receiver (7) and a receiving optic (13). Data light barrier (1) according to one of claims 1 to 5, characterized in that the damping of the electronically controllable damping device (14) is specified via a control element (15). Data light barrier (1) according to one of claims 1 to 6, characterized in that the attenuation of the electronically controllable attenuation device (14) is predetermined depending on the amplitude of a received signal present at the output of the receiver (7). Data light barrier (1) according to one of claims 1 to 7, characterized in that the damping of the electronically controllable damping device (14) is adjusted so that the receiver (7) is operated at a favorable operating point. Data light barrier (1) according to claim 7, characterized in that the amplitude of the received signals is controlled to a setpoint by means of the control element (15). Data light barrier (1) according to one of claims 1 to 9, characterized in that it has a transmitter control (5) assigned to the transmitter (4), by means of which data-containing encodings are imprinted on the light beams (3) of the transmitter (4). Data light barrier (1) according to claim 10, characterized in that it has an evaluation unit (8) assigned to the receiver (7), in which received light beams (3) are decoded. Data light barrier (1) according to one of claims 6 and 11, characterized in that the control element (15) is part of the evaluation unit (8). Data light barrier (1) according to one of claims 1 to 12, characterized in that the transmitter (4) is operated with constant transmission power. Data light barrier (1) according to one of claims 1 to 13 , characterized in that both units (2, 6) are in a housing (2a, 6a). Data light barrier (1) according to one of claims 1 to 14, characterized in that bidirectional data transmission is carried out with it. Data light barrier (1) according to claim 15, characterized in that a transmitter (4) and a receiver (7) are provided in each unit (2, 6), wherein the light beams (3) of a transmitter (4) in one unit (2) are sent to the receiver (7) of the other unit (6). Data light barrier (1) according to claim 16, characterized in that each receiver (7) is assigned an electronically controllable damping device (14). Data light barrier (1) according to one of claims 16 or 17, characterized in that both units (2, 6) are identical in construction.

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