Yes! certainly all three of the above mentioned units are used for expressing the brightness level of light sources in the projectors. The higher the number the better the light source. Lux tells you about the intensity of the light on the surface, Lumen on the other hand measures the total quantity of light emitted by the light source. Lastly, ANSI is also termed as ANSI lumen. It is the abbreviation for American National Standard Institute. Therefore, we can say that it is the total quantity of light emitted by light source. But in this case it is measured according to the American national standards, which is known to give more accurate results.