摘要:
A method is disclosed of controlling a LED, comprising driving the LED with a DC current for a first time, interrupting the DC current for a second time such that the first time and the second time sum to a period, determining at least one characteristic of the LED while the DC current is interrupted, and controlling the DC current during a subsequent period in dependence on the at least one characteristic. The invention thus benefits from the simplicity of DC operation. By operating at the LED in a DC mode, rather than say in a PWM mode, the requirement to be able to adjust the duty cycle is avoided. By including interruptions to the DC current, it is possible to utilize the LED itself to act as a sensor in order to determine a characteristic of the LED. The need for additional sensors is thereby avoided.
摘要:
A light sensor device comprises a substrate (10) having a well (12) defined in one surface. At least one light sensor (14) is formed at the base of the well (12), and an optical light guide (18) in the form of a transparent tunnel (18) within an opaque body (20) extends from a top surface of the device down a sloped side wall of the well (12) to the location of the light sensor (14).
摘要:
A method of determining the dominant output wavelength of an LED, includes determining an electrical characteristic of the LED which is dependent on the voltage-capacitance characteristics, and analyzing the characteristic to determine the dominant output wavelength.
摘要:
A display device comprises a substrate which carries an array of pixels. Each pixel comprises an array of apertures in the substrate, each aperture of the array having a maximum opening dimension less than the wavelength of the light to be transmitted through the aperture. The effective dielectric constant of the aperture and/or the dielectric constant of the substrate is varied, thereby to vary the light transmission characteristics of the pixel between transmission of at least one frequency in the visible spectrum and transmission of substantially no frequency in the visible spectrum.
摘要:
A method of determining the dominant output wavelength of an LED, comprises determining an electrical characteristic of the LED which is dependent on the voltage-capacitance characteristics, and analysing the characteristic to determine the dominant output wavelength.
摘要:
A method of estimating the junction temperature of a light emitting diode comprises driving a forward bias current through the diode, the current comprising a square wave which toggles between high and low current values (Ihigh, llow), the high current value (lhigh) comprising an LED operation current, and the low current value (ILOW) comprising a non-zero measurement current. The forward bias voltage drop (Vf) is sampled and the forward bias voltage drop (Vflow) is determined at the measurement current (ILOW)—The temperature is derived from the determined forward bias voltage drop.
摘要:
A method of estimating the output light flux of a light emitting diode, comprises applying a drive current waveform to the LED over a period of time comprising a testing period. The forward voltage across the LED is monitored during the testing period, and the output light flux is estimated as a function of changes in the forward voltage.
摘要:
Apparatus for regulating the temperature of a light emitting diode (LED). The apparatus includes a heat sink, an LED mount, and an LED mounted on the LED mount. The LED mount is configured to change shape in response to a change in temperature. The change in shape alters the position of the LED relative to the heat sink, for adjusting heat transfer between the LED and the heat sink. The LED mount may include a laminated portion such as a bi-metallic strip.
摘要:
A method is disclosed of controlling a LED, comprising driving the LED with a DC current for a first time, interrupting the DC current for a second time such that the first time and the second time sum to a period, determining at least one characteristic of the LED whilst the DC current is interrupted, and controlling the DC current during a subsequent period in dependence on the at least one characteristic. The invention thus benefits from the simplicity of DC operation. By operating at the LED in a DC mode, rather than say in a PWM mode, the requirement to be able to adjust the duty cycle is avoided. By including interruptions to the DC current, it is possible to utilise the LED itself to act as a sensor in order to determine a characteristic of the LED. The need for additional sensors is thereby avoided.
摘要:
A display device comprises a substrate which carries an array of pixels. Each pixel comprises an array of apertures in the substrate, each aperture of the array having a maximum opening dimension less than the wavelength of the light to be transmitted through the aperture. The effective dielectric constant of the aperture and/or the dielectric constant of the substrate is varied, thereby to vary the light transmission characteristics of the pixel between transmission of at least one frequency in the visible spectrum and transmission of substantially no frequency in the visible spectrum.