Compact illumination system with variable beam direction and beam divergence (original) (raw)

UNIFORM LIGHT SOURCE WITH INTENSITY CONTROL USING LEDs

The main objective of this paper is to reduce the size and the power consumption of the backlight unit. This was realized by intensity control of LEDs, as dimming of LEDs saves power. The information display devices play a major role in the transition to information oriented societies. The global move toward information societies is causing a sharp increase in the demand for information display devices. The rapid development of light emitting diodes (LEDs) over the past few years has surpassed the characteristics of incandescent lamps in luminous efficiency, durability, reliability, safety and power requirements. Though modern high power LEDs which produces up to 120 lm per device, several individual LEDs must be mounted on panels to obtain practical power. Nevertheless, in many lighting application a uniform illumination distribution is desired, which is affected by both the packing density and the array configuration of LEDs.

Design of LED collimator for uniform illumination using two freeform lenses

Regulating the illuminance distribution of an LED collimator to produce a uniform illumination in both the near field and the far field is a challenge in illumination design. In this paper, we present an effective method for designing two separated freeform lenses to control the illuminance distribution and the direction of the rays from the LED. The first lens redistributes the ray energy, and the second one collimates them to obtain a uniform collimated illumination. According to the conservation law of energy, Snell's law, Fermat's law and tangent-plane iterative method, the two freeform surfaces could be calculated simultaneously. The simulation results show that the two freeform lenses can control most of rays into an angle within ±1.5° for an LED with 1 × 1 mm size. The illuminance uniformities are higher than 0.9 in both the near field and the far field.

A Simple Designed Lens for Human Centric Lighting Using LEDs

Applied Sciences

Light is generally important for human beings. Visible light supports vision and can modify circadian rhythm, and together with invisible light at longer or shorter wavelength can also make either a direct or indirect impact on human biological and mental health. For medical applications, several studies have shown success in using light to fasten the skin regeneration in burns and to cure diseases such as newborn jaundice. In daily life, an appropriate amount and time exposure to certain types of light can result in rising of alertness and mood improvement, which leads to noticeable growth in one’s productivity. Therefore, human centric lighting can modify lighting factors to make the best of the natural characteristics of light. The seek an ideal indoor lighting system is widely carried out not only by scientists but also by architects. A qualified luminaire is considered by many factors, including luminous productivity, visual comfort and expenses; meanwhile, the idealization of ...