Abstract: A method is described. The method includes obtaining a relationship between a thickness of a contamination layer formed on a mask and an amount of compensation energy to remove the contamination layer, obtaining a first thickness of a first contamination layer formed on the mask from a thickness measuring device, and applying first compensation energy calculated from the relationship to a light directed to the mask.

Abstract: A drum pedal has a base, a pivoting assembly, a rotating element, a beater holder assembly, a chain assembly, and a foot board. The pivoting assembly is mounted in the base. The rotating element, the beater holder assembly and the chain assembly are mounted in the pivoting assembly. The foot board is mounted between the chain assembly and the base. The base has a resilient element mounted concentric with a shaft of the pivoting assembly. A rotating element receives the resilient element. A torque of the resilient element is evenly matched with a swing caused by the beater holder and the chain assembly. Therefore, the beater holder and the chain assembly return to the original position immediately after the swing. Two drum pedals are manipulated to play respectively, and are connected by a coupling assembly to compose a drum pedal unit.

Abstract: A drum pedal has a base, a pivoting assembly, a rotating element, a beater holder assembly, a chain assembly, and a foot board. The pivoting assembly is mounted in the base. The rotating element, the beater holder assembly and the chain assembly are mounted in the pivoting assembly. The foot board is mounted between the chain assembly and the base. The base has a resilient element mounted concentric with a shaft of the pivoting assembly. A rotating element receives the resilient element. A torque of the resilient element is evenly matched with a swing caused by the beater holder and the chain assembly. Therefore, the beater holder and the chain assembly return to the original position immediately after the swing. Two drum pedals are manipulated to play respectively, and are connected by a coupling assembly to compose a drum pedal unit.

Abstract: A beater for a bass drum includes a head having an adjustment hole, a shaft rotatably mounted in the head above the adjustment hole, and a stem fixedly connected to the shaft and extended out of the adjustment hole for connection to the pedal drive of a bass drum, wherein the stem can be turned in the adjustment hole within a limited angle to change the contained angle between the head and the stem so that the face of the head can positively fit the head of the bass drum.

Abstract: A snap-fastening structure of a drum comprises a fixing socket disposed laterally on a surface of a drum shell, a drum clasp snap-fastened at a counterhoop, and a link bolt penetrating the drum clasp to join the fixing socket. The drum clasp is a clamp body having a clamp-fastening portion extended downward and folded inward to form a clamping which provides, a firm retention of the drum clasp at the counterhoop and a buffer space for reducing influences to vibration of the batter head for thickening and solidifying the timbre of drumbeats.