Anomaloscope
An anomaloscope or Nagel's anomaloscope is an instrument used to test for color blindness and color anomaly. It is used to measure quantitative and qualitative anomalies in colour perception. It can be used to determine whether a person is a tritanope, dichromat or achromatope, although its primary use is in detecting and characteristing anomalous trichromacy. The apparatus was invented by the German ophthalmologist and physiologist Willibald A. Nagel (1870–1911) who named it "Anomaloskop" in 1907.