This chapter provides the fundamental basis for noninvasively tapping into the mind's eye. The EyeTap principle pertains to replacing, in whole or in part, each ray of light that would otherwise pass through the lens of at least one eye of the wearer, with a synthetic ray of light responsive to the output of a processor. Fundamental concepts covered in this chapter include the EyeTap principle; analysis glass, synthesis glass, and the collinearity criterion; effective location of the camera in at least one eye of the wearer; practical embodiments of the EyeTap principle; the laser EyeTap camera; tapping the mind's eye with a computer-controlled laser (replacing each ray of light that would otherwise enter the eye with laser light); the author's fully functional laser EyeTap eyeglasses; infinite depth of focus EyeTap products and devices; and practical solutions for the visually challenged.