Sony SAL20F28 Service Manual page 38

2) Attach the checking lens to the lens test projector, and set the equipments as shown in Fig.4-3-2.
3) Turn the fan switch of the lens test projector to ON, then turn the lamp switch to ON.
Screen
A-mount attachment
Checking lens
Plane mirror
Distance
4) Turn the focus ring of the checking lens until the chart image projected on the screen is the sharpest at the center (y'=0).
5) Set the plane mirror to the center of the projected image (y'= 0), and adjust the projector position so that the mirror reflects the light
to the center of the lens.
SAL20F28 (2.0/28) (20mm F2.8)
Chart
Lens test projector
Fig.4-3-2
4-10
Fan switch
F L
Lamp switch