We develop fast ray-tracing methods for LCD backlight simulation. In general, the LCD backlight uses the light guide plate (LGP) to deliver the lights from the side of backlight to the viewing surface. The printed pattern, which consists of many scattering elements (dots), makes the uniform light distribution on the viewing surface. These dots are distributed in a certain regular array at the bottom of the LGP. Since there are too many dots to be handled, it takes a long time for nonsequential Monte Carlo ray-tracing simulations. To speed up the simulation of the backlight with a printed pattern we use a restricted condition and two fast calculation algorithms for the pattern. From the restricted condition, the ray tracing for pattern is performed only when the ray meets the pattern surface. We use two different fast calculation algorithms to verify whether or not a ray meets the pattern. In the first one, since the probability that a ray meets the pattern is the same as the pattern density at the meeting position, we use the pattern density function as a probability function of meeting. This method makes it possible to speed up the simulation and has another merit that the simulation can be processed without using the pattern data: positions, sizes, and the shape of the pattern elements. In the second one, instead of the great number of dots, we determine four dots that can possibly meet a ray. This method gives faster simulation speed and the same result as that from the calculation with all the dots. © 2005 Society of Photo-Optical Instrumentation Engineers.