lens and sensor setup

kdkdkd

im in a slight fix.
i am presently using a light sensor. i was asked to use a lens along with it recently. is it because the obect i am going to sense is magnified by the lens so that sensor can detect it easily?

but, lets take the situation where a real image is formed because of the lens. Dont we need a screen in this case to project the image, for the sensor to view it? or is it that the sensor doesnt need a projected image.


lets imagine my sensor is a transmitter-detector led pair at an acute angle.
can a light sensor detect the converging(or diverging) rays from the lens, or do i require a proper projected image for sensing.

waiting for a reply.