A projection lens comprises, from a long conjugate side to a short conjugate side, a first lens unit with positive optical power, a second lens unit with negative optical power, and a third lens unit with negative optical power. Copies of the patent application publication with colored drawings will be provided by the Office upon request and payment of the necessary fee. This model is used to predict a feature’s location upon or within a PCB given the feature’s position on the layout. A vent line connects the valve actuators and provides fluid communication therebetween, such that the actuators are maintained at the same pressure state. When such a variation is great undesirably, the controller stops spraying the learning injection quantity.