Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2002-09-25
2004-11-02
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
Reexamination Certificate
active
06812466
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
N/A
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
Photodetectors allow monitoring of a volume of space without blocking the use of that space. Indoors, photodetectors have been used in security applications to detect the presence of unauthorized persons. The use of photodetectors outdoors has been somewhat limited because it can be difficult to distinguish a feature from the natural variations in ambient light caused by changes in sunlight or the orientation of the monitored volume to the sunlight. Ways to overcome the difficulties in using photodetectors outdoors have included filtering, use of regions of the electromagnetic spectrum not affected by sunlight, and imparting unique characteristics to the light being used in the system.
Infrared (IR) sensoring techniques offer many advantages for products that have automotive, industrial and retail applications. However, many of these systems must operate in the presence of sunlight, which has the potential to significantly reduce the performance of the IR sensor. Thus, there is a great need to identify the presence of sunlight or other interfering ambient light and provide corrective techniques to reduce or eliminate the impact of the sunlight on the performance of the IR sensor.
Closures for apertures such as vehicle windows, sunroofs and sliding doors are now commonly motor driven. As a convenience, power windows are frequently provided with control features for the automatic closing and opening of an aperture following a simple short command, commonly known as an “express close” feature. For instance, a driver's side window may be commanded to rise from any lowered position to a completely closed position simply by momentarily elevating a portion of a window control switch, then releasing the switch. Alternatively, automatic closing and opening of an aperture may be in response to input from a separate device, such as a rain or temperature sensor. Such automated aperture closing features may also be utilized in various other home or industrial settings.
While the features described above provide added convenience, they may also introduce a safety hazard. Body parts or inanimate objects may be present within an opening when a command is given to automatically close the window or door. For example, an automatic window-closing feature may be activated due to rain impinging on an interconnected rain sensor while a pet has its head thorough the window. A further example includes a child who has placed its head through the opening of a window or sunroof that is activated to close by the driver, another passenger or accidentally by the child.
Systems have been developed to avoid potentially tragic accidents or property damage involving intervening objects trapped by power windows or sunroofs. These systems, using contact methodologies, typically detect the circumstance in which a window has been commanded to express close when it should not. Complete closure is prevented whenever an intervening object such as a finger or arm extended through the opening contacts the safety system during closure. In further refinements of the closure safety system, the closure member, such as the window, is not required to come into contact with the intervening object for the object to be detected.
When sunlight can be disregarded, such contactless object detection systems typically measure the magnitude of a reflected signal to determine whether an intervening object is present. A photo-emitter emits a light beam, which an optical system directs across the opening that is being monitored. An unobstructed opening may result in the reflection of at least a portion of the emitted beam from the opposing side of the aperture. The reflection from the opposing side ordinarily results in a reflected signal of a well-defined intensity being returned to a receiver. A photo-receiver disposed in an appropriate location receives the reflected light beam and generates an output signal indicative of the intensity of the reflected beam. An intervening object located in the path of the light beam changes the intensity of the reflected light beam, a condition reflected in the receiver output signal. The receiver output signal therefore can be used to differentiate between the opening with an object through it and the opening unobstructed.
These optical systems, however, are vulnerable to interference by ambient light, especially sunlight. Prior art systems for coping with sunlight have included the use of synchronous detectors and “judgment circuits” consisting of a number of logic circuits coupled together. These judgment circuits, however, may still be susceptible to interfering sunlight and typically include several functional blocks, each of which contains several digital logic circuits. The large number of parts associated with the judgment circuits can increase both the power that is consumed and dissipated as heat and the cost associated with the object detection circuitry.
An improved way to cancel the portion of a signal that is associated with sunlight, while maintaining the intelligibility of the portion of the signal associated with an obstacle, is needed. Preferably, such an apparatus will provide enhanced accuracy by reducing the effect of the interfering ambient light while using fewer parts and consuming less power than the prior art.
BRIEF SUMMARY OF THE INVENTION
The present invention has particular application in systems providing an indication of the presence of an object within a pinch zone located in the path of an automated closure device such as a powered window, powered sunroof, or powered door or hatch. When an optical sensor incorporates a synchronous detection amplifier operating in the infrared (IR) range to selectively amplify the system light signal, the invention negates the effect of sunlight that could otherwise swamp the desired light or cause excess electronic noise.
The embodiments of the invention work in conjunction with methods and apparatus for sensing an object with an optical sensor. The optical sensor utilizes synchronous detection and an integrator to separate a desired optical signal from ambient light and electronic noise. Further, the system cancels modulated energy from features of the environment not associated with an object in the opening.
The sunlight compensating system functions with a system that includes a modulator driving a photo-emitter and a switched amplifier receiving first and second signals respectively. A photodetector receives a portion of light reflected from the pinch zone and/or an object therein and provides an optical detector signal to the switched amplifier.
The switched amplifier provides an output signal that includes a voltage that results from the difference between the optical detector signal and a reference signal multiplied by a gain that is dependent on the phase in the detection cycle. The gains and duration of the phases are selected to set the gain of the switched amplifier to an average value of zero when no modulated optical signal is present from the pinch zone and/or object therein.
The obstacle detection system further includes a means to electronically integrate the difference between the output of the switched amplifier and an adjustable reference voltage for a predetermined measurement time. A detector receives the integrator output signal and provides indicia of the presence or absence of an object within the pinch zone.
The obstacle detection system further includes a control element or controller that provides the means to monitor the degree of photodetector exposure to sunlight and then apply appropriate control signals that selectively optimize the system response and compensate for changes to the transfer function of some components.
In one embodiment the controller functionality may be implemented using a conventional microcontroller integrated circuit and the appropriate analog processing elements such as analog to digital converter (A/D), digital to analog converter (DAC)
Davis, Jr. James D.
Hawley Stephen A.
O'Connor Christopher J.
Vernaz Todd R.
Hannaher Constantine
Prospects Corp.
Weingarten Schurgin, Gagnebin & Lebovici LLP
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