Systems, circuits and methods for extending the detection range of an inspection system by avoiding circuit saturation

An inspection system, comprising:

• an illumination subsystem configured for directing light to a specimen;
• a single photodetector configured for detecting light scattered from the specimen and for converting the light into an electrical signal;
• an amplifier stage coupled for converting the electrical signal into a pair of analog signals, one having a comparatively higher gain than the other, wherein the pair of analog signals are representative of the same wavelengths of the light detected by the photodetector;
• and
• a pair of analog-to-digital converters (ADCs) coupled for converting the pair of analog signals into a pair of digital signals, one being larger in value than the other.

A method for inspecting a specimen, the method comprising:

• directing light to the specimen;
• detecting light scattered from the specimen, wherein said detecting comprises:
• utilizing only one photodetector for detecting the light scattered from the specimen and converting the light into an electrical signal;
• generating a first signal and a second signal in response to the electrical signal, the first signal having a higher resolution than the second signal for detecting substantially lower levels of the scattered light, wherein the first and second signals are generated without changing the gain of the photodetector, and wherein the first and second signals are representative of the same wavelengths of the light detected by the photodetector;
• and
• using the first signal for detecting features, defects or light scattering properties of the specimen until the first signal reaches a predetermined threshold value, and thereafter, using the second signal for said detecting.