Experimental Setup Diagram
The converging lens f1 focus the light into the pinhole. The pin hole and the "purification" is help to get a purified light spot on the grating, which makes the image better on the camera. The converging lens f2 helps to converge the light onto "purification".
From the grating to the camera, those form a 4f system.
f1=35.0mm; f2=150.0mm; f=200.0mm; diameter of pin hole=50ยตm.
P.S.: The polarizer is used for controlling light intensity.