Light source module, backlight module and display device

A light source module, comprising:

• a back plate, comprising a bottom plate and a sidewall standing on the bottom plate, wherein an included angle (θslope) is formed between an outer side surface of the sidewall and a horizontal plane where the bottom plate is located, and the included angle is an acute angle, and an optical distance (OD) is defined between a top end of the sidewall and the horizontal plane;
• a plurality of light-emitting units arranged in the back plate, wherein the light-emitting units which are closest to the sidewall are defined as a plurality of target light-emitting units, and each of the target light-emitting units has a radiation angle (θLED), and each of the target light-emitting units is separated from the sidewall by a distance (d);
• wherein the distance (d) is a difference between a first horizontal distance and a second horizontal distance, and the first horizontal distance is formed between each of the target light-emitting units and a predetermined location of the sidewall, and the second horizontal distance is formed between a bottom edge of the sidewall and the predetermined location of the sidewall;
• wherein the first horizontal distance is calculated according to a first function F1, and the first function F1 is determined by a tangent function of a complementary angle of the radiation angle (θLED), the second horizontal distance is calculated according to a second function F2, and the second function F2 is determined by a tangent function of the included angle (θslope).