Наткнулся после недолгих поисков на интересную статью:
Lexus First to Use White LED Headlight
http://techon.nikkeibp.co.jp/article/HO ... 25/136768/
потом понял что в новом примусе, который начали продавать с этого лета в европе тоже ближний на диодах !!!
суть наглядно на картинках:
c языком надеюсь дружите )Brightness, Power, Heat
Technological development is rapid in white LEDs, and already there are products boasting emission efficiencies of 100lm/W, surpassing that of florescent, HID and other lights. Many designs offer 100lm or more optical flux from a single white LED, accelerating application in lighting uses. The new Lexus headlight uses five white LEDs with optical fluxes of 400lm, providing sufficient brightness for the low beam (Fig 1a).
According to Koito Manufacturing, getting the idea to market was not a trivial task, thanks to problems like ensuring sufficient brightness, reducing power consumption and handling generated heat. They resolved them through joint development of a white LED with Nichia Corp of Japan.
Brightness needed to be at least 20Mcd/m2, equivalent to a halogen light. Existing white LEDs only output several Mcd/m2. The solution was to mount four large (about 1mm square) blue LED chips in a single package, with 2.5W (700mA input current) per chip, for a total of 10W (Fig 1b). This design pushed the brightness up to 25Mcd/m2 (Fig 1c).
When significant wattage is pushed to a single chip, however, emission efficiency drops. Compared to an HID light, the actual performance of the headlight was only 40lm/W, increasing power consumption. Koito Manufacturing improved optical utilization efficiency by providing each white LED light with different flux distribution characteristics to create a distribution pattern (Fig 2a). Optical loss is considerably less than when a complex distribution pattern is created using a single light.
The structure of white LEDs used for high beams was also reviewed. These headlights need a light distribution pattern slightly below the horizontal. Conventionally the light is partially blocked to create this distribution, but engineers instead use a mirror called a beam shaper to shift the light beam slightly above the horizontal (Fig 2b).
Through these and other measures, at least half of the total beam flux of the white LEDs is emitted from the headlights, which is dramatically higher than the efficiencies of HID or halogen headlights usually achieving only about a third. As a result,
power consumption is the same as the high-end HID headlights used in the Lexus LS460.
The service life of the white LEDs was also extended through innovations in handling heating. The LED headlight module had to fit into the same mounting space as the HID lights used in the LS460, which meant that only a limited volume was available to handle heat. First engineers improved the LED chips so that bond could withstand temperatures of 150*C. The chips are encapsulated on top with glass to minimize thermal degradation when in use. Compared to more commonly-used materials such as epoxy and silicone resins, this provides stable brightness for 8,000 hours of operation at a bond temperature of 115*C. Competing products are said to show a performance drop-off of at least 10% after only 5,000 hours.
To allow heat to escape from the white LED, headlight bodies are provided with radiation fins and heat pipes. Many LED headlight prototypes feature both fins and cooling fans to radiate heat, but the addition of a cooling fan requires a larger headlight module. The solution was to use a heat pipe full of distilled water, transferring the heat without the need for a cooling fan.
а то набивать влом )