The signal light enables other road users located at a certain distance to clearly recognize the light signal. The parameters of the lamp associated therewith are luminous intensity, illuminating area, beam spread angle, and light color. In order to easily recognize the light signal at night with a dark background, for a signal light that is only used at night, such as a position light, a position light, and a stop light, the luminous intensity is usually only between a few candelas and tens of candelas. For daylighting signal lights, such as turn signals, brake lights, etc., the required light intensity is typically up to hundreds of candelas. In order to make such signal lights do not produce glare when working at night, in addition to limiting the maximum luminous intensity, some also use the two conditions of day and night. For most of the car signal lights that are close-range, it is also necessary to consider the matching between the light-emitting area and the specified luminous intensity to prevent the brightness from being too large and causing glare. The beam spread angle of most signal lamps (the angle between the 10% maximum light intensity directions) is not less than 20° in the vertical direction and not less than 40° in the horizontal direction.