Abstract: An electric hair dryer having a radiometer which remotely senses the infrared radiation emanating from the hair being dried and which contains a control means that causes the heating means in the dryer to turn off when the infrared radiation indicates the temperature of the hair is about 50.degree. C.

Abstract: Infrared detectors, such as thermistors, thermocouples, thermopiles, pyroelectric detectors, and the like, are rendered insensitive to short wave radiation, such as the visible or near infrared, but sensitive to longer wave infrared, for example, beyond 4.5.mu. by coating the active surface of the detector with a strong reflector of visible light but which absorbs infrared at least in the range from 7.mu. to somewhat beyond 10.mu.. A preferred example of the paint, which appears white to the eye, is titanium dioxide, but this is not the only material which can be used as any white or strongly diffuse reflecting coating which absorbs in the infrared from 7.mu. on can be used. The infrared instrument for which the detector is particularly useful is an intrusion detector or burglar alarm which is activated by the infrared radiation from the intruder, which is in the range from around 7.mu. to 10.mu. and beyond. The strongly diffuse reflecting action in the visible prevents false alarms from ambient light.

Abstract: This invention relates to intrusion detection devices, and in one embodiment includes an array of infra-red detectors with associated means for selectively increasing the number of scan zones which may be monitored by the same detector array, by providing an optical system with reflectors and/or lenses having a multiplicity of facets set at selected angles to direct primary impulses received from portions of the entire scanned field sequentially to the detector array.

Abstract: A simple optical system collects and applies radiation from a predetermined field of view onto a thermopile detector. The thermopile detector has a plurality of rows of thermocouples having all active junctions with alternate polarity which are aligned in columns of the same polarity, whereby in response to an object moving across the thermopile an output signal is produced of alternately changing polarity. Logic circuitry is provided for processing the signals from the thermopile in a predetermined polarity sequence to discriminate against false alarms and for indicating the presence of an intruder and sounding an alarm.