Product detector for a steady visual evoked potential stimulator and product detector

• US 5,052,401 A
• Filed: 03/22/1989
• Issued: 10/01/1991
• Est. Priority Date: 08/06/1986
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Sherwin, Gary W.
• Primary Examiner(s): JAWORSKI, FRANCIS J
• Application Number:
  US07/327,047
• Time in Patent Office: 923 Days
• Field of Search: 128/731, 128/745, 128/746, 310/110, 310/122, 310/125, 329/122, 329/124
• US Class Current: 600/558
• CPC Class Codes: A61B 3/02 Subjective types, i.e. testing apparatus requiring the active assistance of the patient
• CPC Class Codes: A61B 3/0325 provided with red and green targets
• CPC Class Codes: A61B 5/377 using evoked responses
• CPC Class Codes: A61B 5/398 Electrooculography [EOG], e.g. detecting nystagmus; Electroretinography [ERG]

Abstract

An automated visual testing system is disclosed which presents an alternating steady state visual stimulus to a patient through an optical system that modifies the stimulus image. As the image changes, the patient produces evoked potentials that change. The evoked potentials are detected by a product detector which produces the amplitude of the evoked potentials. The product detector includes filters which isolate the patient'"'"'s evoked potentials, a modulator which detects the response using the stimulus source frequency and a demodulator that determines the amplitude of the response. The product detector detects the level of the steady state evoked potential signals even in the presence of substantial background noise and extraneous electroencephalograhic signals. These detectors can be used to monitor the evoked potential produced by visual, aural or somatic steady state stimuli. The components described above can be used to produce a system that can determine to which of several different displays an observer is paying attention by providing images that blink at different frequencies and product detectors for each of the stimulus frequencies. The product detector producing the highest output indicates the display upon which the observer is focused.

Claims

1. A product detector, comprising:

narrow band filter means for removing noise from evoked potentials produced by a patient at a predetermined frequency;

modulation means for detecting the evoked potentials at the predetermined frequency, said modulation means comprising a programmable gain control amplifier connected to said narrow band filter means; and

demodulation means for producing an amplitude of the evoked potentials at the predetermined frequency.