Question 1. How to condense the light of the LED to a point?
Answer 1: This is not possible. There is a law in optics that the brightness of the image is never greater than the brightness of the light source.
The LED has a light-emitting area, so it has brightness. If all or most of the light is concentrated into a small area, the brightness will exceed the brightness of the LED itself, so it is impossible.
In order to converge as much as possible, the size of the reflector/condenser can only be increased. Combining lenses or other methods will not help.
Q2. If there is an electric light source that can convert all the electric power into white visible light, how high is the theoretical efficiency?
Answer 2: As mentioned above, it depends on the spectrum of white light. For sunlight, it's 94 lumens/watt. The light efficiency of the CIE1931 chromaticity system is very poor because the long wavelength of 700nm is chosen for red. In contrast, CRT TVs or LED TVs are much more efficient at 300 lumens/watt.
Question 3. What is the relationship between illuminance and the brightness of the illuminated object?
Answer 3: Brightness=Reflectivity*Illuminance/π
Q4. How to measure brightness with illuminance meter?
Answer 4: The luminance meter and the illuminance meter are two things and cannot be directly replaced. Luminance meters measure the brightness of illuminants, while illuminance meters measure the illuminance of the illuminated location. However, if you want to know the brightness of a luminous body with a larger area, such as a light box, and this object is at your fingertips, you can directly stick the probe of the illuminometer on the luminous body, read the lux value and multiply it by a coefficient, It is the nits value of brightness.
