Object detection apparatus and method

Abstract

An object detection apparatus 1200 having a plurality of emitters to emit light, and a plurality of detectors to detect light; the emitters and detectors arranged such that the light to be detected cr

Description

14 06 24 Technical Field

[0001] The present invention is concerned with an apparatus and method for detecting a physical object. More specifically, the present invention is concerned with an apparatus for detection of an object by disruption of a beam of electromagnetic energy. Background Art

[0002] Detection of physical objects using beams of EM energy (specifically light, and more specifically infra red light) is well known. Such systems comprise an emitter and a receiver. The emitter is capable of emitting a focussed beam of IR light towards the receiver. Upon the emitted light hitting the receiver (which comprises a suitable photosensitive element) the detector can confirm the presence of the beam by altering an electrical signal. If the beam of light is interrupted or disturbed by an object, the detector no longer receives the light, and the signal is interrupted. This system is used for a variety of applications- for example detection of people or objects.

[0003] Figure 1 shows a prior art system 1100 for detection of an object within a space S. Three emitters 1102, 1104, 1106 are provided aligned in a linear fashion on a first side of the space S. Each is configured to emit a beam of IR light 1108, 1110, 1112 respectively towards a respective receiver 1114, 1116, 1118. Th beams 1108, 1110, 1112 are parallel and operated in a one-beam I one emitter / one receiver configuration. An object 1120 has moved into the space S, and interrupted the beam 1112 from reaching the receiver 1118. A suitable electrical detection circuit connected to the photosensitive receiver 1118 can therefore detect the presence of the object 1120.

[0004] A problem with this type of detector is that the presence of non-uniform objects becomes problematic. There are gaps between the beams, and as such the coverage is sub-optimal.

[0005] It is an aim of the present invention to mitigate the problems with the prior art. Summary of Invention

[0006] According to a first aspect of the present invention there is provided an object detection apparatus according to claim 1. 14 06 24

[0007] By "detection space" we mean either a volume (a three-dimensional space) or a plane (a two-dimensional space).

[0008] By "object" we mean any object including living things such as humans.

[0009] Advantageously, using the detectors to detect the light from multiple emitters allows the detection space to be covered more comprehensively for irregular shaped objects which may otherwise escape detection.

[0010] Further, because perfect alignment of the emitters and receivers is not required, such systems installation is made more straightforward in retrofit situations. For example, if the system needs to be installed in an existing detection space, it can be provided in two parts with the transmitter post and receiver post being separate. So, for example, an installation at a doorway may comprise two strips and a controller. There would be an amount of tolerance provided, and / or a calibration process. The lack of a requirement for perfect alignment means that installation is made much easier.

[0011] Preferably the controller is configured to cycle through at least two of the plurality of emitters whilst monitoring one of the plurality of detectors.

[0012] Preferably the controller is configured to cycle through at least two of the plurality of detectors whilst monitoring one of the plurality of emitters.

[0013] Preferably the plurality of detectors are mounted on a first member on a first side of the detection space, and the plurality of emitters are mounted on a second member on a second side of the detection space.

[0014] Preferably the first member and the second member are flat and parallel.

[0015] Preferably the distance between each detector and at least two closest emitters is the same. Preferably only the closest emitter / detector pairs are polled. [001 6] Preferably the emitters and detectors are arranged in a grid pattern viewed normal to the first and second members.

[0017] Preferably there is a third member positioned on the opposite side of the second member to the first member, wherein a further detection space is defined between the second member and the third member, and wherein a further plurality of emitters is located on the second member, and a further plurality of detectors is located on the third member, 14 06 24 and the controller is configured to detect the presence of an object in the further detection space by using each of the further plurality of detectors to detect light emitted by at least two of the further plurality of emitters.

[0018] Preferably the controller is configured to detect the presence of an object in the detection space by using each of the plurality of detectors to detect light emitted by adjacent emitters of the plurality of emitters. [001 9] The invention also provides a key storage apparatus comprising: a key mount for mounting a key such that the key hangs; an object detection apparatus according to the first aspect, the detection space positioned below the key mount such that the apparatus can detect the presence or absence of a key attached to the key mount.

[0020] Preferably the key mount is a key fob receptacle.

[0021] Preferably the key fob receptable comprises a fob detector for detecting the presence or absence of a key fob.

[0022] Preferably the presence of a key or set of keys is verified by both the fob detector and the object detection apparatus.

[0023] Preferably the key fob receptable comprises a fob lock for retaining the key fob in position in the key fob receptacle.

[0024] According to a second aspect there is provided a method of detecting the presence or absence of an object according to claim 15. Brief Description of Drawings

[0025] An embodiment of the present invention will now be described with reference to the following figure in which: FIGURE 1 is a side view of a prior art system; FIGURE 2 is a perspective view of a first apparatus in accordance with the present invention; FIGURES 3 to 5 are detail views of a part of the apparatus of Figure 2; FIGURE 6 is a system view of the apparatus of Figure 2; 14 06 24 FIGURE 7 is a view of a second embodiment incorporating the first embodiment of Figure 2; FIGURES 8a and 8b are views of a third embodiment. Description of the first embodiment

[0026] A first apparatus 1200 in accordance with the present invention is shown in Figure 2. Configuration

[0027] The apparatus 1200 comprises a frame 1202 having a base plate 1204 and three sensor panels 1206, 1208, 1210 mounted normal thereto. The panels 1206, 1208, 1210 are spaced-apart. A first detection space 1212 is defined as the volume between the panels 1206, 1208, and a second detection space 1214 is defined as the volume between the panels 1210, 1212.

[0028] The first panel 1206 has a first side 1206a and a second side 1206b. The second panel 1208 has a first side 1208a and a second side 1208b. The third panel 1210 has a first side 1210a and a second side 1210b.

[0029] On the first side 1206a of the first panel 1206 there is provided an array 1216 of receivers. On the first side 1208a of the second panel 1208 there is provided an array 1218 of transmitters. On the second side 1208b of the second panel 1208b there is provided an array 1220 of transmitters. On the first side 1210a of the third panel 1210 there is provided an array 1222 of receivers.

[0030] Figure 3 shows a side view of the first side 1206a of the panel 1206. The array 1216 comprises a plurality of receivers 1216a - 1216h. The receivers 1216a - 1216h are arranged in three columns (or rows if oriented at 90 degrees to that shown). The first column has three receivers, the second has two and the third, three. The receivers of the first and third columns are aligned. The receivers of the second column are positioned in between those of the first and third columns in a vertical sense. In other words, if the in-column spacing between the receivers is d, then the second column is offset by d / 2. In this embodiment, d = 20mm. There are eight receivers. In this embodiment, the receivers are Vishay VEMD2020X01 infrared photodiodes. 14 06 24

[0031] A 74HC4051 PW,118 8 channel multiplexer is used to enable each photodiode receiver as required. A 1OkQ sense resistor converts the current to a voltage which is then amplified. First stage amplification is using a common emitter bandpass amplifier, second stage is an op amp based bandpass filter, both centred on 20kHz.

[0032] Figure 4 shows a side view of the first side 1208a of the panel 1208. The array 1218 comprises a plurality of transmitters 121 8a - 121 6g. The transmitters 1218a - 1218g are arranged in three columns (or rows if oriented at 90 degrees to that shown). The first column has two transmitters, the second has three and the third, two. The transmitters of the first and third columns are aligned. The transmitters of the second column are positioned offset from those of the first and third columns in a vertical sense. In other words, if the incolumn spacing between the transmitters is d, then the second column is offset by d / 2. There are seven transmitters. In this embodiment, the transmitters are VSMB2943GX01 infrared LEDs.

[0033] Each LED is enabled using a BC847C transistor. Current flowing in the LED is controlled using 2x 1 kQ resistors in parallel (500Q). Current in each LED is: . _ (Vsupply Vf 'LED ~ n (12 - 1.35 - 0.15) 1 led — 21mA

[0034] The VSMB2943GX01 has an intensity of 20mW / sr @ 100mA. The gap between the two boards is 6.5cm and each receiver is optically offset from its closest transmitter by 10mm.

[0035] The transmission angle is 0 = tan' f—A = 9° \65 /

[0036] At 9°, the transmitted signal is reduced by approx. 7%. Transmitted intensity 21mA In =--20mW / sr ■ 0.93 0 100mA 7 k(rx) = MmW / sr

[0037] Reverse light current in the VEMD2020X01 photodiode is 12pA at 1 mW / cm2 intensity. Light intensity reduces with the square of distance. The sensitivity of the photodiode is further reduced by approximately 15% at an angle of 9°. The current flowing in the receiver will be 6.5cm2 = 940^ 14 06 24

[0038] Figure 5 shows the receivers (R) and transmitters (T) overlaid. It can be seen that rather than lying in line I parallel to each other, the transmitters and receivers are interdigitated on the XY plane (i.e., the planes of the panels). They form a regular grid of d / 2 x d / 2 in the XY plane. The boards are designed such that the optical axes of each transmitter / receiver extend parallel to one another but are offset from one another, either vertically or horizontally.

[0039] In this way, each of the receiverscan be designed to identify a "positive" receipt of the incident emitted light at the same level of intensity. If any of the receivers were positioned in the direct line of sight (opposite) the transmitters, they would receive light which has not been attenuated by the angle between transmitter and receiver. Therefore the receiver detection circuits (amplifiers and so on) would need to detect a positive across a broader range of amplitudes. This would make the circuits inherently more complex to implement. Therefore, by ensuring that each transmitter is the same distance / angle from multiple receivers (i.e. not directly opposite) provides for a simpler system.

[0040] Figure 6 shows the apparatus 1200 connected to a controller 1224. The controller is configured to provide control signals to each of the emitters on either side 1208a, 1208b of the panel, and to receive signals from the receivers on the panels 1206, 1210 as described above. The controller 1224 is configured to provide outputs 1224a, 1224b indicative of the presence of an object in either of the detection spaces 1212, 1214. Use [0041 ] In use, detectors and emitters are activated in turn. This provides a pattern of beams directed from the panel 1208, across the detection space 1212 to the receivers on the panel 1206. As each beam is emitted, the relevant detector is used to determine whether the corresponding signal has been received. If the signal is not received, an object is reported as detected in the space 1212 (OBSTRUCTED mode). As shown in the table below, the first pair is emitter TX2 with receiver RX1, and so on.. 14 06 24 Beam Transmitter Detector 1 TX2 RX1 2 TX1 RX1 3 TX1 RX2 4 TX2 RX2 5 TX2 RX3 6 TX4 RX3 7 TX1 RX3 8 TX3 RX3 9 TX3 RX4 10 TX6 RX4 11 TX4 RX4 12 TX4 RX5 13 TX2 RX5 14 TX5 RX5 15 TX5 RX6 16 TX7 RX6 17 TX4 RX6 18 TX6 RX6 19 TX6 RX7 20 TX7 RX7 21 TX7 RX8 22 TX5 RX8

[0042] The beam sequence can be modified using the following definitions

[0043]

[0044] TIMER0 is used to generate a 25psec tick. The relevant output pin is toggled to generate a 20kHz signal. This is disabled after (PULSECOUNT) cycles. The next TX / RX pair are enabled and after a delay (INTER_BEAM_DELAY), the next beam is generated. At the 14 06 24 end of the sequence (MAXBEAMS), after a delay (END_OF_SEQUENCE_DELAY), the sequence repeats.

[0045] BEAM DETECT THRESHOLD defines the number of pulses which indicate a beam has been received. In this case it is slightly less than the number transmitted to provide limited noise filtering. Should a beam be obstructed and fewer pulses are received, the processor goes into OBSTRUCTED mode and sets the relevant output to HIGH (i.e., an object is present).

[0046] In order to exit OBSTRUCED mode, the system needs to see (NUM CLEAN SWEEPS) unobstructed sweeps before it will change state. This hysteresis prevents flickering of the output under certain circumstances.

[0047] Each detector detects the light from more than one transmitter. Each transmitter emits light for detection between more than one detector. Viewed in the XY plane, the beams create a grid pattern. The beams also have a Z axis component between the arrays. The beams in bold are shown in Figure 5.

[0048] If, for example, the emitter TX4 is active (beams 6, 11 &12), if (when polled) the photoreceivers RX3, RX4 or RX5 show a signal below a predetermined threshold, the presence of an object in the detection space is confirmed by the controller. Description of the second embodiment

[0049] Referring to Figure 7, there is shown a further embodiment in which a key fob receiving apparatus 1300 is provided with the apparatus 1200 of the first embodiment. The apparatus 1300 is (for example) of the type disclosed in the applicant's prior application WO 2021 / 130346 (incorporated herein by reference where permitted). A plurality of key fob receptacles 1302 are provided with detection means configured to detect the presence of a key fob 1304. Locking means are also provided to lock the fob 1304 in position.

[0050] As well as the presence of the key fob 1304, it is also useful to detect the presence of a key 1306 or set of keys attached thereto. In this embodiment, the apparatus 1200 is positioned below the fob receptacle with the detection space 1212 located where the key 1306 hangs. Therefore, as well (or instead of) detection of the fob 1304, the system can be configured to detect the keys. This ensures, for example, that the system cannot be fooled by the presence of a fob without keys attached, or if the keys are removed after the fob is inserted. 14 06 24 Description of the third embodiment [0051 ] The firstand second embodiment are configured to detect the presence or absence of an object in a persistent manner. Referring to Figures 8a and 8b a system 1400 is configured to detect passage of an object passing through a 2D detection space, aperture or doorway 1402.

[0052] An emitter array 1404 and receiver array 1406 are provided on either side of the space. In the same manner as the previous embodiments each array comprises a plurality of emitters 1405 or receivers 1407. The emitters and receivers are not aligned but are offset (in a vertical sense) such that passage of light from one emitter can be detected at more than one receiver.

[0053] The system 1400 is linked to an access control system in which an indicator 1408 is provided above the doorway 1402. The system is active, and "armed" to detect the presence of an object in the detection space in Figure 8a. In this Figure the indicator 1408 is red and instructs that access is not permitted. If a person attempts to cross the detection space, the system produces a persistent alert (even if they then pass out of the detection space).

[0054] When a user 1410 is permitted (e.g. by providing access credentials), the system is "disarmed", the indicator 1408 indicates thatthe user can pass and the system is configured not to produce an alert. This may be achieved by e.g. deactivating the emitters and receivers, or simply changing the configuration to not produce an alert upon detection.

[0055] This solution is particularly useful where physical doors are a hindrance- e.g. in clinical settings. Variations

[0056] The invention is applicable to key systems, but may be used in other applications, for example: • Cabinets and locker systems to sense items, both upon entry / exit and whether the volume in question is occupied by an item. • Doorways, dock doors, entrances &lifts to sense people and / or items. 14 06 24 • Vehicles with or without doors and convertibles to sense unauthorised attempted access. • Home intruder systems. • Cabinets or storage spaces with or without doors. • Intelligent racking / smart storage bins. In one embodiment, a system may prevent human picking errors. Such a system would be applied to each of a plurality of picking areas or zones. In an accessible state, IR beams would turn off (or not produce an alert) to permit access, and a visible green light would turn on. In an inaccessible state, a visible red light would be on and the system would be configured to detect unauthorised picking activity to produce an alert should the IR beams be broken. • Access control systems without physical doors where red and green lights (or walls of light) are used to show a blanket of colour for areas where doors are a nuisance e.g. hospitals. Instead of locking doors, a light system could be used to grant or deny access. When a green lightis active access is permitted and the system would not prduce an alert. When a red light is active if anyone crosses the beams (passes through the doorway) an alert would be produced.

Claims

16 12241. An object detection apparatus comprising:a plurality of emitters configured to emit light;a plurality of detectors configured to detect light; and,a controller;wherein:the emitters and detectors arranged such that the light to be detected crosses a detection space;the emitters and detectors each have an optical axis, wherein the emitters and detectors are arranged such that their optical axes are parallel and offset;each emitter and detector is part of more than one emitter / detector pair; and,the controller is configured to detect the presence of an object in the detection space by activating the detectors and emitters in turn to cycle through emitter / detector pairs, and using each of the plurality of detectors to detect light emitted by at least two of the plurality of emitters.

2. An object detection apparatus according to claim 1, wherein the controller is configured to cycle through at least two of the plurality of emitters whilst monitoring one of the plurality of detectors.

3. An object detection apparatus according to claim 1 or 2, wherein the controller is configured to cycle through at least two of the plurality of detectors whilst using one of the plurality of emitters to emit light.

4. An object detection apparatus according to any preceding claim, wherein the plurality of detectors are mounted on a first member on a first side of the detection space, and the plurality of emitters are mounted on a second member on a second side of the detection space.

5. An object detection apparatus according to claim 4, wherein the first member and the second member are flat and parallel.

6. An object detection apparatus according to any preceding claim, wherein the distance between each detector and at least two closest emitters is the same.16 12247. An object detection apparatus according to claim 4 or 5, wherein the emitters and detectors are arranged in a grid pattern viewed normal to the firstand second members.

8. An object detection apparatus according to any preceding claim, comprising a third member positioned on the opposite side of the second member to the first member, wherein a further detection space is defined between the second member and the third member, and wherein a further plurality of emitters is located on the second member, and a further plurality of detectors is located on the third member, and the controller is configured to detect the presence of an object in the further detection space by using each of the further plurality of detectors to detect light emitted by at least two of the further plurality of emitters.

9. An object detection apparatus according to any preceding claim, wherein the controller is configured to detect the presence of an object in the detection space by using each of the plurality of detectors to detect light emitted by adjacent emitters of the plurality of emitters.

10. A key storage apparatus comprising:a key mount for mounting a key such that the key hangs;an object detection apparatus according to any preceding claim, the detection space positioned below the key mount such that the apparatus can detect the presence or absence of a key attached to the key mount.

11. A key storage apparatus according to claim 10, wherein the key mount is a key fob receptacle.

12. A key storage apparatus according to claim 11, wherein the key fob receptable comprises a fob detector for detecting the presence or absence of a key fob.

13. A key storage apparatus according to claim 12, comprising a controller, wherein the presence of a key or set of keys is verified by both the fob detector and the object detection apparatus.

14. A key storage apparatus according to claim 13, wherein the key fob receptable comprises a fob lock for retaining the key fob in position in the key fob receptacle.

15. A method of detecting the presence or absence of an object, the method comprising the steps of:providing a plurality of light emitters;providing a plurality of light detectors;the emitters and detectors provided such that:the light to be detected crosses a detection space;the emitters and detectors each have an optical axis, wherein the emitters and detectors are arranged such that their optical axes are parallel and offset;each emitter and detector is part of more than one emitter I detector pair;detecting the presence of an object in the detection space by activating the detectors and emitters in turn to cycle through emitter / detector pairs and using each of the plurality of detectors to detect light emitted by at least two of the plurality of light emitters by monitoring an output signal of the respective detector and using the at least two light emitters to emit light.16 1224

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