Multi-spot scanning collection optics

A system for inspecting or measuring a specimen, comprising:

• an illumination channel for generating and scanning a plurality of incident beams obliquely to form a plurality of spots that scan across a segmented line comprised of a plurality of scan portions of the specimen;
• and
• one or more detection channels for sensing light emanating from a specimen in response to the incident beams directed towards such specimen and collecting a detected image for each scan portion as each incident beam's spot is scanned over its scan portion, wherein the one or more detection channels comprises a longitudinal side channel for longitudinally collecting a plurality of detected images for the scan portions,
• wherein the longitudinal side channel comprises:
• a front lens arranged for receiving output beams that are scattered from the scan portions and directing such output beams through a Fourier plane towards a back lens,
• the back lens arranged for receiving and directing the output beams towards a sensor module, and
• the sensor module arranged for separately sensing the output beams from the back lens.

A method of inspecting a specimen, comprising:

• scanning multiple incident beams obliquely over separated scan lines of the specimen;
• receiving and separating output beams scattered from the separated scan lines of the specimen in response to the incident beams;
• longitudinally directing each separated output beam towards a sensor to longitudinally generate an image or signal, wherein each separated output beam is directed along an optical axis along which each scan line is imaged and which is also parallel and coincident with a plane of the specimen or an image plane of the specimen;
• and
• detecting defects or measuring a characteristic of the specimen based on the image or signal from each sensor.