197 results about "Constant light" patented technology

A method and apparatus for non-invasively determining the blood oxygen saturation level within a subject's tissue is provided that utilizes a near infrared spectrophotometric (NIRS) sensor capable of transmitting a light signal into the tissue of a subject and sensing the light signal once it has passed through the tissue via transmittance or reflectance. The method includes the step of determining attenuation of the light signal as the sum of: (i) attenuation attributable to deoxyhemoglobin; (ii) attenuation attributable to oxyhemoglobin; and (iii) attenuation attributable to light scattering within the subject's tissue. The present method also makes it possible to account for attenuation attributable to fixed or constant light absorbing biological tissue components, and attenuation attributable to variable characteristics of the sensor. By determining differential attenuation as a function of wavelength, the attenuation attributable to tissue light scattering characteristics, fixed light absorbing components, and measuring apparatus characteristics are mathematically cancelled out or minimized relative to the attenuation attributable to deoxyhemoglobin, and attenuation attributable to oxyhemoglobin.

The inside surface of a cover for a skylight is molded to have a variable prism that directs low-angle light into the skylight tube and that reflects away some high-angle light, to achieve a more constant light output over the course of the day. The prism is established by a series of circular parallel grooves, with grooves nearer the apex of the cover having cross-sections that are different than the cross-sections of grooves nearer the periphery of the cover.

An LED light source drive includes an LED current generating circuit and an LED drive controller. The current generating circuit is operable to receive power from a power source and to generate a dc current that can be used to the drive an LED light source. The drive controller is operable to control the dc current to ensure that the light output of the light source remains approximately constant over its operating lifetime. In one embodiment, the drive controller ensures that the effective light output of the light source remains approximately constant by automatically increasing the dc current in predetermined amounts at predetermined times. In an alternative embodiment, the drive controller includes an LED light sensor that is operable to generate a light signal indicative of the effective light output of the light source and the controller uses this light signal to control the dc current output.

A controller 5 for a high intensity discharge lamp 4 includes a primary ballast for providing a primary current to the lamp 4, and a current injector which in the case shown comprises a control ballast 8 and a switch 9 (e.g. a triac) controlled by a control unit 12. The current injector injects a secondary current into the lamp 4 that is less than the primary current and can be varied by the control unit 12, e.g. by varying the amount of time within an a.c. cycle that the control ballast 8 is switched into the circuit. The controller 5 allows the lamp 4 to be controlled, for example, to operate at a constant power (variable light output) or at a constant light output (variable power).

An improved sighting device is provided. The sight may be used on a bow or other device which is typically sighted on an object during use. The sight includes at least one light-gathering fiber-optic fiber having at least one end from which absorbed light may be transmitted for viewing by a user. The fiber-optic fiber includes an associated element that regulates the amount of light absorbed in inverse proportion to the impinging light intensity in an automatic manner providing a more constant light intensity output.