GB2526070A

GB2526070A - Method and testing apparatus for testing an optical sensor

Info

Publication number: GB2526070A
Application number: GB1407841.4A
Authority: GB
Inventors: Peter Collins; John Curzon
Original assignee: ENSOTA Ltd
Current assignee: ENSOTA Ltd
Priority date: 2014-05-02
Filing date: 2014-05-02
Publication date: 2015-11-18
Also published as: CN105035923B; CN105035923A; GB201407841D0

Abstract

A method of testing an optical door sensor 100 with an emitter 102 and a receiver 106 comprising deploying an optical attenuator 152 between the emitter 102 and the receiver 106 causing the light signals 104 from the emitter 102 to be attenuated by an attenuation amount and evaluating the operation of the sensor 100, which may be determining if a light signal is detected, observing whether the door moves and/or an audible or visual alert. The attenuation may be increased progressively over a succession of stages and the operation of the sensor 100 may be evaluated for each stage. This may continue until a light signal from the emitter 102 is not detected by the receiver 106. The test may be used to determine a threshold value at which the receiver 106 no longer receives the light emitted. The optical attenuator 152 may be a variable opacity window. This test may be used in an automatic door such as an elevator.

Description

METHOD AND TESTING APPARATUS FOR TESTING AN OPTICAL SENSOR

The invention relates to a method of testing an optical sensor, in particular an optical door sensor of an automatic door installation.

A known type of optical door sensor is a break beam sensor having an emitter for emitting a light signal and a receiver for detecting the emitted light signal. A typical use of a break beam sensor is determining whether an obstacle is present, which depends on whether an emitted light signal is detected by the receiver (i.e. whether the beam is broken).

Break beam sensors are often used in automatic door installations, such as elevator installations or entrance doors. For example, an elevator car of an elevator installation is typically provided with an optical door sensor for detecting the presence of an obstacle, such as a person or an object, in front of or between the elevator car doors.

Known optical door sensors include break beam sensors that form a light curtain of infrared light outside of the elevator car doors (i.e. between the elevator car doors and the shaft doors when the elevator car is at a stop). The optical door sensors may have an array of emitters for emitting light signals, and an array of receivers for detecting the light signals. The optical door sensor typically determines that there may be an obstacle in front of the elevator car doors when an emitted light signal is not detected by a receiver. On the other hand, it determines that no obstacle is present when an emitted light signal is detected by the receiver.

The operation of such an elevator installation depends on whether or not the optical door sensor determines that an obstacle is present. For example, confirmation that no obstacle is present is typically required before an elevator car can begin to move, and the elevator car doors may be prevented from closing if the optical door sensor determines that an obstacle is present.

However, the performance of the optical door sensor depends on its operating conditions, and it may erroneously determine that an obstacle is present if the operating conditions are poor. For example, in a dirty or dusty environment, material may build up on the optical door sensor that may partially or totally occlude light signals at the emitter and/or the receiver. A build-up of material may therefore prevent a light signal emitted by the emitter from being detected by the receiver, causing the optical door sensor to incorrectly determine that an obstacle is present, and thereby preventing the doors from closing and the elevator car from moving. Accordingly, poor operating conditions may result in the optical door sensor ceasing to function normally, with the result that the elevator installation is taken out of service, and access to a building is limited. Other operating conditions that can affect sensor performance include the physical alignment of the emitter and receiver, electronic noise and the condition of the components of the optical sensor itself, which can degrade over time.

An elevator installation is one example of an automatic door installation in which a gradual deterioration in the operating conditions of an optical door sensor can eventually cause the optical door sensor to cease functioning normally. However, the deterioration in the operating conditions that may lead to the optical door sensor ceasing to function normally is typically only detected once the optical door sensor has already failed, since an investigation as to the cause of failure may then be initiated.

It is therefore desirable to provide a method of testing an optical door sensor of an automatic door installation.

According to an aspect of the invention there is provided a method of testing an optical door sensor of an automatic door installation, the optical door sensor having an emitter for emitting a light signal and a receiver for detecting the light signal, the optical door sensor having a baseline state in which the receiver can detect a light signal from the emitter, the method comprising: deploying an optical attenuator between the emitter and the receiver to put the optical door sensor in an attenuation state in which light signals from the emitter are attenuated by an attenuation amount; and evaluating the operation of the optical door sensor with the optical attenuator in the attenuation state.

The attenuation amount may be predetermined.

The method may be a method of testing an operating margin of the optical door sensor.

The operating margin may relate to a level of deterioration of the operating conditions of the optical door sensor that can be sustained whilst the optical door sensor continues to function normally. An operating margin may relate to the level of deterioration of an operating condition that can be sustained, and may be indicative of other operating margins and/or the overall tolerance of the optical door sensor to deterioration of its operation conditions.

The operating conditions of the optical door sensor may include environmental operating conditions (i.e. operating conditions that cannot be or are not controlled), such as the level of optical occlusion of the sensor by accumulated material (e.g. dirt or dust), the level of electronic noise that affects the optical door sensor and the alignment of the emitter and receiver.

Deterioration of the operating conditions can cause the optical door sensor to cease functioning normally. For example, a light signal from the emitter may not be detected by the receiver, despite there being no obstacle between the emitter and the receiver.

Attenuating light signals from the emitter may simulate a deterioration in the operating conditions, in particular an operating condition relating to the level of optical occlusion between the emitter and receiver.

Evaluating the operation of the optical door sensor may comprise determining whether a light signal from the emitter is detected by the receiver. This may be done directly or indirectly. For example, evaluating the operation of the optical door sensor may comprise monitoring the automatic door installation for an indication of whether a light signal from the emitter is detected by the receiver.

The automatic door installation may periodically conduct a signal test comprising: emitting a light signal from the emitter, and determining whether the light signal is detected by the receiver. The signal test has a positive result if the light signal is detected by the receiver and a negative result if the light signal is not detected by the receiver. The operation of the automatic door installation may depend on the result of the signal test. A positive signal test may indicate that there is no obstacle, such as a person or an object, blocking the light path between the emitter and receiver. A negative signal test may indicate that there is an obstacle, such as a person or object, blocking the light path between the emitter and receiver.

For example, where automatic doors are provided to open when a person or object approaches, the automatic door installation may be configured to execute a door-opening operation when a light signal from the emitter is not detected by the receiver (i.e. a negative signal test result), as this may indicate that a person or object has broken the light beam between the emitter and the receiver.

The automatic door installation may be configured to prevent, interrupt or reverse a door-closing operation when a light signal from the emitter is not detected by the receiver (i.e. a negative signal test result), as this may indicate that a person or object has broken the light beam between the emitter and the receiver.

The automatic door installation may be configured to execute a door-closing operation only after a light signal from the emitter is detected by the receiver (i.e. a positive signal test result), as this may indicate that there is no person or object between the emitter and receiver.

The automatic door installation may be an elevator car installation, and the elevator car installation may be configured so that an elevator car journey can commence only after a positive signal test result.

Accordingly, the determination of whether a light signal from the emitter is detected by the receiver may be based on observing whether a door of the automatic door installation moves.

A positive signal test result may cause the automatic door installation to generate an audible and/or a visual alert. Alternatively or in addition, a negative test result may cause the automatic door installation to generate a different audible and/or visual alert.

For example, the automatic door installation may be configured to generate an audible or visual alert, such as a beep from a sounder or a flash from an LED, dependent on whether a light signal from the emitter is detected by the receiver. In particular, the automatic door installation may be configured to generate an audible alert or visual alert, such as a flash of red LED, when a light signal from the emitter is not detected by the receiver, to indicate that there is an obstacle between the emitter and receiver that could be impacted by a closing door. The automatic door installation may be configured to generate a visual alert, such as a flash of a green LED, when a light signal from the emitter is detected by the receiver, to indicate that there is no obstacle between the emitter and receiver. The visual alert may provide confirmation that the light signal from the emitter is detected by the receiver.

Accordingly, the determination of whether a light signal from the emitter is detected by the receiver may be based on an audible or visual alert from the automatic door installation that is indicative of whether a light signal from the emitter is detected by the receiver.

It may be determined whether a light signal from the emitter is detected by the receiver by manual inspection (i.e. by a person). Alternatively, a monitoring apparatus may determine whether a light signal from the emitter is detected by the receiver.

The method may further comprise generating an alert when it is determined that a light signal from the emitter is not detected by the receiver and the attenuation amount is less than or equal to a limit margin. The limit margin may be predetermined. The limit margin corresponds to a minimum attenuation amount at which it is desired for the optical door sensor to continue functioning normally, i.e. a minimum desired operating margin for the optical door sensor. Accordingly, the alert is generated if it is determined that the optical door sensor has ceased functioning normally when the attenuation amount is less than the limit margin.

The optical door sensor may be put in a succession of attenuation states having different attenuation amounts, and the operation of the optical door sensor may be evaluated for each of the attenuation states. The attenuation amount may be progressively increased over successive attenuation states. The operation of the optical door sensor may be evaluated for successive attenuation states until it is determined that a light signal from the emitter is not detected by the receiver.

The optical attenuator may be deployed to put the optical door sensor in two or more of the plurality of attenuation states. The optical attenuator may gradually attenuate light signals from the emitter, for example by continuously varying its opacity.

Alternatively, a plurality of optical attenuators may be deployed to put the optical door sensor in the plurality of attenuation states. Further, separate optical attenuators may be deployed for each one of the plurality of attenuation states. Two or more optical attenuators may be deployed in series to put the optical door sensor in an attenuation state.

According to a further aspect of the invention there is provided testing apparatus for an optical door sensor of an automatic door installation, the testing apparatus comprising: an optical attenuator arranged to be deployed between an emitter and a receiver of the optical door sensor to put the optical door sensor in an attenuation state, in which light signals from the emitter are attenuated by an attenuation amount; monitoring apparatus configured to determine whether a light signal from the emitter is detected by the receiver based on the operation of the optical door sensor with the optical attenuator in the attenuation state; and an indicator configured to generate an alert when it is determined that a light signal from the emitter is not detected by the receiver and the attenuation amount is less than or equal to a limit margin. The attenuation amount may be predetermined. The limit margin may be predetermined.

The monitoring apparatus may be coupled to the optical aftenuator and/or integral with the optical attenuator. Alternatively, the monitoring apparatus may be separate from the optical attenuator.

The optical attenuator may be configured to put the optical door sensor in a plurality of attenuation states, in which light signals from the emitter are attenuated by a corresponding plurality of attenuation amounts. Each of the attenuation amounts may be predetermined.

The testing apparatus may be configured to progressively increase the attenuation amount over successive attenuation states. The testing apparatus may be configured to put the optical door sensor in a succession of attenuation states and to monitor the operation of the optical door sensor for successive attenuation states until it is determined that a light signal from the emitter is not detected by the receiver.

The optical attenuator may be arranged to indicate an operating margin of the optical door sensor relating to the attenuation amount at which the operation of the optical door sensor changes from a functioning state, in which a light signal from the emitter is detected by the receiver, to a non-functioning state, in which a light signal from the emitter is not detected by the receiver. The operating margin may be indicated based on a maximum attenuation amount corresponding to the detection of a light signal from the emifter by the receiver, a minimum attenuation amount corresponding to the failure of the receiver to detect a light signal from the emitter, or the operating margin may be indicated based on a combination of these two attenuation amounts.

The testing apparatus may be provided with a report means for indicating the operating margin. The testing apparatus may be provided with a report means for indicating an attenuation state or a parameter relating to the operating margin. The report means may be a display.

The optical attenuator may be a variable-opacity window, often called a light valve, such as a glass or plastic panel incorporating a Suspended Particle Device (SPD) film.

The opacity of the variable-opacity window may be electrically controllable. The optical attenuator may contain a liquid crystal layer. The optical attenuator may comprise a film of the type described in International Patent Publication W093/09460. The optical attenuator may be continuously variable.

Alternatively, the optical attenuator may comprise one or more translucent foils. A plurality of translucent foils can be interchanged and/or deployed in series to attenuate light signals from the emitter. For example. the optical attenuator may comprise a translucent foil of variable thickness which can be moved relative to a light signal to vary the thickness of the foil through which the light signal passes, for example the foil can be wedge-shaped. The optical attenuator may comprise two such wedge-shaped foils that can be moved relative to one another to vary the total thickness of the optical attenuator through which the light signal passes.

The monitoring apparatus may be configured to monitor an audible or visual alert of the automatic door installation indicative of whether a light signal from the emitter is detected by the receiver. The monitoring apparatus may be configured to observe whether a door of the automatic door installation moves in a manner indicative of whether a light signal from the emitter is detected by the receiver.

The optical door sensor may comprise an emitter array having a plurality of emitters, and a receiver array having a plurality of receivers. Accordingly, the optical door sensor may be configured to control door-opening and door-closing operations dependent on whether light signals from the emitters are received by the emitters.

The invention will now be described, by way of example, with reference to the drawings, in which: Figure 1 schematically shows an elevator car of an elevator installation and a testing apparatus; Figure 2 schematically shows the optical door sensor and testing apparatus of Figure 1; Figure 3 shows a method of testing an optical door sensor according to an embodiment of the invention; Figure 4 shows a further method of testing an optical door sensor; Figure 5 shows a yet further method of testing an optical door sensor; Figure 6 shows a plot illustrative of deterioration of the operating conditions of an optical door sensor.

Figure 1 shows an elevator car 10, an optical door sensor 100 and a testing apparatus 150.

The elevator car 10 is moveable within a shaft (not shown) of an elevator installation and has a pair of elevator car doors 12 that can be controlled to open and close by an elevator controller.

The elevator car 10 is provided with an optical door sensor 100 attached to the elevator car 10 by sensor mounts 14. The optical door sensor 100 comprises an emitter array 101 for emitting infrared light signals and a receiver array 105 for detecting the light signals. The sensor mounts 14 are arranged to hold the emitter array 101 and the receiver array 105 in the space between the elevator car 10 and the walls of the shaft.

In particular, the sensor mounts 14 hold the emitter array 101 and the receiver array 105 opposite each other and aligned so that they can define a light curtain 103 between them, consisting of an array of individual infrared light signals 104 (or light beams), in the space between the elevator car doors 12 and the shaft doors installed at stop positions of the elevator installation. The emitter array 101 and the receiver array each comprise a plurality of individual emitters 102 and receivers 106 respectively.

The optical door sensor 100 further comprises a sounder 120 for emitting an audible alert when it is determined that a light signal from an emitter 102 is not detected by a receiver 106, as will be described in detail below.

The testing apparatus 150 comprises an optical attenuator 152 and a support arm 153 for manually holding the optical attenuator in place. In this embodiment, the optical attenuator 152 comprises a variable-opacity windowl54 of variable opacity. The variable-opacity window contains a homogenous liquid crystal layer. The window is frameless so as to avoid edge effects. In other embodiments, the optical attenuator may comprise a support window for holding one or more translucent foils, together with the required foils. The variable-opacity window 154 is sufficiently large for two or three individual light signals 104 of the light curtain to pass through it. However, it will be appreciated that the variable-opacity window 154 can be larger or smaller, and may be positioned so that only one light signal passes through it.

In this embodiment, the optical attenuator 150 is also provided with a display panel 156 and a controller for controlling the opacity of the variable-opacity window 154 and the output of the display 156.

The optical door sensor 100 is also shown schematically in Figure 2 including detail relating to a single emitter and receiver pair 102, 106 of the emitter array 101 and receiver array 105 respectively. The receiver 106 is provided with a photodiode 107 (which is common between the receivers 106 of the receiver array) for processing the output of the photodiode 107 and detecting the emitted light signal 104. The optical door sensor 100 further comprises a controller 110 which causes the emitters 102 to emit light signals 104, and determines whether the emitted light signals 104 are detected by the receivers 106.

The optical attenuator 152 is shown in a deployed position between the emitter 102 and the receiver 106, thereby putting the optical door sensor in an attenuation state in which light signals 104 from the emitter are attenuated by an attenuation amount. In this embodiment, the opacity of the variable-opacity window 154 of the optical attenuator 152 can be varied to define a plurality of different attenuation amounts, and so the optical attenuator 152 is arranged to put the optical door sensor 100 in any one of a plurality of attenuation states. The different attenuation amounts are predetermined, but in other embodiments the variable opacity panel may be continuously variable.

In use, the optical door sensor 100 is considered to be in a functioning state when the receivers 106 can detect the emitted light signals. The functioning state relates to the ability of the receivers 106 to detect emitted light signals 104 in the absence of an obstacle between the emitter 102 and the receiver 106. Accordingly, the optical door sensor can still be in a functioning state when, in use, an obstacle, such as a person or object, is present between the emitter 102 and the receiver 106.

The performance of the optical door sensor 100 is affected by its environmental operating conditions, which cannot be controlled by the optical door sensor. For example, the operating conditions include the accumulation of material, such as dust and dirt, on the emitters 102 of the emitter array 101 and/or the receivers 106 of the receiver array 105, and the level of electronic noise that affects the optical door sensor 100. For example, electronic noise affecting the sensor may be generated by equipment sharing the power supply of the optical door sensor, or other sources of electromagnetic interference.

The attenuation of light signals 104 between the emitter 102 and receiver 106 can be used to simulate deterioration of the environmental operating conditions of the sensor, and to test whether the optical door sensor 100 continues or ceases to function normally.

Figure 3 shows a method of testing an operating margin of the optical door sensor 100 according to a first embodiment of the invention. In this example, it is tested whether an operating margin corresponding to optical occlusion (i.e. attenuation) of light signals 104 from the emitters 102 is within a predetermined limit margin of 20%, as described in detail below.

The optical door sensor 100 is initially in a baseline state 100 (302) in which it is functioning normally in that light signals 104 from the emitters 102 can be detected by the receivers 106 (in the absence of an obstacle between the emitter 102 and the receiver 106).

The elevator car doors 12 are opened (304) and held open until the testing apparatus is deployed with the optical attenuator 152 in the deployed state (306), in which it is positioned to attenuate light signals 104 from at least one emitter 102. In this embodiment, only a single attenuation state of the optical door sensor is to be tested, and so the optical attenuator is set to attenuate the light signals by an attenuation amount corresponding to a limit margin of 20% (308). The limit margin corresponds to a minimum simulated deterioration of the operating conditions of the optical door sensor 100 that it is desirable for the optical door sensor 100 to tolerate whilst continuing to function normally, as will be described in detail below.

After a delay from the doors being opened, a controller for the elevator car doors 12 will determine whether a door-closing operation can be initiated, based on whether an obstacle is determined to be present between the emitter array 101 and the receiver array 105. This determination is based on the result of a signal test performed by the optical door sensor which determines whether light signals 104 emitted from the emitters 102 are detected by the receivers 106. Therefore, whether a door-closing operation occurs is indicative of whether the attenuated light signals 104 can still be detected by the corresponding receiver 106 with the optical door sensor 100 in the attenuated state.

The movement of the doors is therefore observed (310) and it is determined whether they close or remain open (312). In this embodiment, this is done manually by simply watching the doors. However, it will be appreciated that in other embodiments a motion sensor could be provided for detecting movement of the doors.

If the doors are observed to move in a door-closing operation, this indicates that the controller has determined that no obstacle is present, and therefore it can be concluded that the operating margin for optical occlusion of the optical door sensor is greater than 20% (314). This means that the optical door sensor is able to continue functioning normally despite the attenuation of a light signal by an attenuation amount of 20%.

If the doors are observed to remain open (allowing for a delay implemented by the elevator controller), then it can be concluded that the operating margin for optical occlusion of the optical door sensor is less than or equal to the margin limit of 20% (316). Accordingly, the operator can respond to this result (318) by logging the result in a maintenance record or alerting maintenance personnel of the result, so that corrective action may be taken. Corrective action would typically involve cleaning the emitter array 101 and the receiver array 105 of the optical door sensor 100 to remove any accumulation of dirt or dust. The testing method may then be repeated to confirm that the operating margin for optical occlusion is within an acceptable limit (i.e. within the limit margin of 20%).

Figure 4 shows a further testing method according to a second embodiment of the invention. This embodiment differs from the first embodiment described above in that it is suitable for an optical door sensor that is configured to emit an audible and/or visual alert when a light signal 104 from an emitter 102 is not detected by a respective receiver 106 (i.e. when it determines that an obstacle is present). In this embodiment, the optical door sensor has a sounder 120 (see Figure 2), which issues an audible alert.

Initially, the optical door sensor 100 is in a baseline state as described above (302). It is not necessary to set the elevator car doors 12 open, as the method relies on audible and visual alerts. The optical attenuator is deployed (304) to put the optical door sensor in an attenuation state in which light signals 104 from at least one emitter 102 are attenuated by the margin limit, which is 20% in this embodiment.

It is then determined whether the optical door sensor 100 issues a visual and/or an audible alert (402, 404) indicative of a receiver 106 failing to detect a light signal 104 from an emitter 102. If either one of a visual and audible alert is determined to have been issued, then it can be concluded that the operating margin for optical occlusion of the optical door sensor is less than or equal to the margin limit, as above (316).

Conversely, if neither a visual nor an audible alert is determined to have been issued, then it can be concluded that the operating margin for optical occlusion of the optical door sensor is greater than the margin limit, as above (314).

In this embodiment, the optical door sensor is only provided with a sounder, and so no visual alert will be determined.

In this example embodiment, the visual and or alert can be determined by manual inspection (i.e. by listening or watching for the respective alerts). However, in an alternative embodiment, the testing apparatus 150 can be provided with a monitoring apparatus, comprising a light sensor and/or an audio sensor (microphone), for automatically detecting the visual and/or audible alerts that the optical door sensor is configured to issue. Accordingly, the monitoring apparatus can be configured to detect the particular types of alerts issued by the optical door sensor.

A method of testing an operating margin of the optical door sensor 100 and of determining the operating margin according to a third embodiment of the invention is shown in Figure 5. In this example, the method determines an approximate value for an operating margin for optical occlusion of the optical door sensor.

The optical door sensor 100 is initially in a baseline state, as described above (302).

In this embodiment, the optical attenuator 152 is configured to progressively increase the attenuation amount so as to progressively attenuate light signals 104 emifted from the at least one emitter 102. In particular, the optical attenuator 152 is configured to gradually increase its opacity so as to incrementally increase the attenuation amount by which light signals 104 from the at least one emitter 102 are attenuated. The attenuation amount is set to increase by 1% at a predetermined frequency, which in this embodiment is once every 30 seconds. In other embodiments, a bufton could be provided to increase the attenuation amount on demand.

The attenuation amount is initially set to 1% (502) and the optical attenuator is deployed (504) to put the optical door sensor 100 in an attenuation state in which light signals 104 from the emitter 102 are attenuated by 1%. The attenuation amount is indicated on the display 156. In this embodiment, the actual attenuation amount is displayed, but in other embodiments an indication may be provided, for instance by a number of LED5.

As with the second embodiment of the invention, it is determined whether the optical door sensor issues a visual alert 402 or audible alert 404 indicative of a receiver 106 failing to detect a light signal 104 from an emitter 102.

If an audible or visual alert is determined to have been issued, then it can be determined (510) that the operating margin for optical occlusion lies between an attenuation amount of 0%, corresponding to previous state (the baseline state) of the optical door sensor, and 1%, corresponding to the current attenuation state. However, in this example, no audible or visual alerts are issued by the optical door sensor when the attenuation amount is 1%.

After a delay of 30 seconds, the optical attenuator increases the attenuation amount (506) by the 1% increment, whilst remaining in the deployed position (504). In other embodiments, for instance where the optical attenuator 152 comprises a number of interchangeable foils, the optical attenuator may be removed from the deployed state so that the attenuation amount can be increased. Alternatively, different optical attenuators can be used for successive attenuation states.

The method continues in this loop until it is determined that an audible or visual alert indicative of a receiver 106 failing to detect a light signal 104 from an emitter 102 has been issued. In this example, this occurs once when the attenuation of the optical door sensor has been increased to 13%. The operating margin is therefore determined (510) to be between 12%, which corresponds to the optical door sensor functioning normally, and 13%, which corresponds to the optical door sensor ceasing to function normally.

The operating margin can therefore be compared with a margin limit (512), which corresponds to a level of deterioration in the operating conditions of the optical door sensor that it is desired for the optical door sensor to tolerate whilst continuing to function normally. In this example embodiment, the margin limit is 20%, and the testing apparatus 150 is provided with a memory for storing the margin limit, and a processing unit for determining the operating margin based on the current attenuation amount and the attenuation increment. Accordingly, in this example, it will be determined that the operating margin (12-13%) is less than the margin limit (20%) (514). An alert is issued on the display 156 to indicate that the operating margin is less than the margin limit (518).

In an alternative example test, the operating margin may be determined to be greater than the margin limit (516), for example it may be 23%. In such an example test, the testing apparatus may display the operating margin and an indication that this is above the margin limit on the display 156.

An illustrative example of the tolerance of the optical door sensor is shown in Figure 6, which is a plot showing in general terms the deterioration in the performance of the optical door sensor 100 overtime, assuming that dirt or dust accumulates on the surfaces of the optical door sensor 100 at a constant rate, which serves to deteriorate the performance of the sensor. The performance is shown in relation to optimum operating conditions of the optical door sensor in which the environmental operating conditions are favourable (i.e. no accumulated dust or dirt on the optical door sensor 100, and no significant electronic noise affecting the sensor). The plot is a generalisation in that it assumes that deterioration of all operating conditions have the same linear effect on the performance of the optical door sensor.

The plot shows a service limit for the optical door sensor 100 of 75% of optimum operating conditions. This means that the optical door sensor 100 will fail to detect an emitted light signal at 75% of optimum operating conditions.

As shown in the plot, at 0 months, the baseline state of the sensor is only 95%, meaning that the real (as opposed to optimum) operating conditions results in a 5% reduction in the performance of the sensor. This could be due to an amount of material already accumulated on the sensor 100 or owing to poor alignment of the emitter array 101 and the receiver array 105. The baseline state of the sensor is shown to deteriorate over time as more material builds up on the sensor to occlude the light signals. Operating with the baseline settings, the sensor will reach the service limit after 4 months.

The plot also shows the results of testing the operating margin of the optical door sensor overtime, using three different margin limits corresponding to attenuation amounts of 5%, 10% and 15% respectively. Initially, each test would result in a determination that the operating margin is greater than the margin limit. After 1 month, a test using an margin limit of 15% would generate an alert. In contrast, a test using a margin limit of 5% would not cause an alert until 3 months have passed. Setting the limit margin to values of either 5%, 10% and 15% would therefore result in alerts being generated 1 month, 2 months and 3 months before failure of the optical door sensor respectively.

Accordingly, it can be seen that testing the operating margin according to the above described methods can allow a failure of the optical door sensor to be avoided.

Embodiments of an optical door sensor have been described in which there is an emitter array having a plurality of emitters and a receiver array having a plurality of receivers. It will be appreciated that the optical door sensor or a door controller may be configured so that an obstacle is determined to be present only when a minimum number of receivers, greater than one, fail to detect a light signal from respective emitters. In other words, a limited number of receivers may be able to fail to detect a light signal without causing the optical door sensor to operate as if the presence of an obstacle has been determined. Accordingly, a signal test for the optical door sensor may comprise emitting light signals from the plurality of emitters, and determining if a predetermined minimum number of receivers detect the light signals.

Accordingly, for optical door sensors that operate in this way, it will be appreciated that the optical attenuator can be deployed in a manner consistent with the configuration of the optical door sensor. For example, if a particular optical door sensor requires at least two receivers of the receiver array to fail to detect a light signal before determining that an obstacle may be present, then the optical attenuator can be deployed to attenuate light signals corresponding to at least two receivers.

Alternatively, a number of receivers equivalent to the number that are allowed to fail can be blocked, and the optical attenuator can be deployed to attenuate a light signals to be received by at least one further receiver.

Whilst an embodiment of the invention has been described in which an optical attenuator is used to progressively increase an attenuation amount until it is determined that an audible and/or visual alert indicative of a receiver failing to detect a light signal from an emitter, it will be appreciated that in other embodiments the method may monitor other indications of the operation of the optical door sensor. In particular, the method may be based on observing whether a door-closing operation occurs or is prevented from occurring when the optical door sensor is in an attenuation state.

It will be appreciated that the term light" means electromagnetic radiation including both visible light and non-visible light such as infrared and ultraviolet light.

Although embodiments of the invention have been described in which the optical attenuator is supported on a support arm that can be manually supported, it will be appreciated that in other embodiments it may be supported on a self-supporting stand, such as retort stand, tripod or monopod, or it may be coupled to the optical door sensor or surrounding equipment, such as by adhesion, by magnetic or other fasteners VThiIst embodiments of the invention have been described in which the automatic door installation is an elevator installation, it will be appreciated that in other embodiments the automatic door installation may a different type of door installation, such as an entrance or exit door for a building. Further, the optical door sensor may be an edge sensor.

Claims

CLAIMS: 1. A method of testing an optical door sensor of an automatic door installation, the optical door sensor having an emitter for emitting a light signal and a receiver for detecting the light signal, the optical door sensor having a baseline state in which the receiver can detect a light signal from the emitter, the method comprising: deploying an optical attenuator between the emitter and the receiver to put the optical door sensor in an attenuation state in which light signals from the emitter are attenuated by an attenuation amount; and evaluating the operation of the optical door sensor with the optical attenuator in the attenuation state.
2. A method according to claim 1, wherein evaluating the operation of the optical door sensor comprises determining whether a light signal from the emitter is detected by the receiver.
3. A method according to claim 1 or 2, wherein evaluating the operation of the optical door sensor comprises monitoring the automatic door installation for an indication of whether a light signal from the emitter is detected by the receiver.
4. A method according to claim 2 or 3, wherein the determination of whether a light signal from the emitter is detected by the receiver is based on observing whether a door of the automatic door installation moves.
5. A method according to claim 2 or 3, wherein the determination of whether a light signal from the emitter is detected by the receiver is based on an audible or visual alert from the automatic door installation that is indicative of whether a light signal from the emitter is detected by the receiver.
6. A method according to any one of claims 2 to 5, wherein a monitoring apparatus determines whether a light signal from the emitter is detected by the receiver.
7. A method according to claim 6, further comprising generating an alert when it is determined that a light signal from the emitter is not detected by the receiver and the attenuation amount is less than or equal to a limit margin.
8. A method according to any one of the preceding claims, wherein the optical door sensor is put in a succession of attenuation stages having different attenuation amounts, and wherein the operation of the optical door sensor is evaluated for each of the aftenuation states.
9. A method according to claim 8, wherein the attenuation amount is progressively increased over successive attenuation states.
10. A method according to claim 8 or 9, wherein the operation of the optical door sensor is evaluated for successive attenuation states until it is determined that a light signal from the emitter is not detected by the receiver.
11. A method according to any one of claims 8 to 10, wherein the optical attenuator is deployed to put the optical door sensor in two or more of the plurality of attenuation states.
12. A method according to any one of claims 8 to 11, wherein a plurality of optical attenuators is deployed to put the optical door sensor in the plurality of attenuation states.
13. Testing apparatus for an optical door sensor of an automatic door installation, the testing apparatus comprising: an optical attenuator arranged to be deployed between an emitter and a receiver of the optical door sensor to put the optical door sensor in an attenuation state, in which light signals from the emitter are attenuated by an aftenuation amount; monitoring apparatus configured to determine whether a light signal from the emitter is detected by the receiver based on the operation of the optical door sensor with the optical attenuator in the attenuation state; and an indicator configured to generate an alert when it is determined that a light signal from the emitter is not detected by the receiver and the attenuation amount is less than or equal to a limit margin.
14. Testing apparatus according to claim 13, wherein the optical aftenuator is configured to put the optical door sensor in a plurality of attenuation states, in which light signals from the emitter are attenuated by a corresponding plurality of attenuation amounts.
15. Testing apparatus according to claim 14, wherein the optical aftenuator is arranged to indicate an operating margin of the optical door sensor relating to the attenuation amount at which the operation of the optical door sensor changes from a functioning state, in which a light signal from the emitter is detected by the receiver, to a non-functioning state, in which a light signal from the emitter is not detected by the receiver.
16. Testing apparatus according to any one of claims 13 to 15, wherein the optical attenuator is a variable-opacity window.
17. Testing apparatus according to any one of claims 13 to 16, wherein the monitoring apparatus is configured to monitor an audible or visual alert of the automatic door installation indicative of whether a light signal from the emitter is detected by the receiver.
18. A method of testing an optical door sensor substantially as described herein with reference to the drawings.
19. A testing apparatus for an optical door sensor substantially as described herein with reference to the drawings.