By A. Mark Smith
Someday among 1028 and 1038, Ibn al-Haytham accomplished his enormous optical synthesis, Kitab al-Manazir ("Book of Optics"). via no later than 1200, and maybe slightly prior, this treatise seemed in Latin below the identify De aspectibus. In that shape it used to be attributed to a definite "Alhacen." those alterations in identify and authorial designation are indicative of the profound adjustments among the 2 models, Arabic and Latin, of the treatise. in lots of methods, actually, they are often seemed now not easily as various models of an analogous paintings, yet as varied works of their personal correct. for that reason, the Arab writer, Ibn al-Haytham, and his Latin incarnation, Alhacen, symbolize specific, occasionally even conflicting, interpretive voices. And an identical holds for his or her respective texts. To complicate concerns, "Alhacen" doesn't signify a unmarried interpretive voice. there have been a minimum of translators at paintings at the Latin textual content, considered one of them adhering faithfully to the Arabic unique, the opposite content material with distilling, even paraphrasing, the Arabic unique. hence, the Latin textual content provides no longer one, yet a minimum of faces to the reader. quantity This two-volume severe variation represents fourteen years of labor on Dr. Smith's half. provided the 2001 J. F. Lewis Award. quantity Two--English Translation
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Extra info for Alhacen's Theory of Visual Perception (First Three Books of Alhacen's de Aspectibus), Volume Two--English Translation (Transactions of the American Philosophical Society)
And if the intervening air between that visible objectand the eye is continuous, if there is no opaque body interposedbetween that visible objectand the eye, and if that visible objectis somehow illuminated,the form of the light and color on the surfaceof thatvisible objectwill reachthe eye along a line containedby that cone. And the form of every point on the surfaceof that visible objectwill radiate along the straight line connecting that point and the vertex of the cone, which lies at the center of the eye.
And in addition to that, the form of one point is spread out upon an area of the surface of the glacialis ratherthan arrivingat a point, and this follows from the fact thatwhen the form of a right-handpoint with respect to the eye reaches a point on the surface of the eye, assuming that the line along which that form extends is oblique to the eye's surface,it will refractto the left of the normal dropped from the center of the eye to that point on its surface. And the form that is refractedin this way at the ex- 366 ALHACEN'SDE ASPECTIBUS tremityof the normal [at the point of refraction]reachesa point to the left of the point on the surfaceof the glacialiswhere that perpendicularintersects it.
And we shall show how to carryout this experimentalconfirmationproperlyin our section on refraction,72 and at that time everythingto do with refractionwill be revealed. But in that section we shall not avail ourselves of the discussion of matters that we have demonstrated in this book concerning such TRANSLATION:BOOKONE 367 phenomena. 37]Therefore,when the forms of two points on one side of a visible objectarriveobliquely at a single point on the surfaceof the eye, they will intersect [and continue] along two lines whose [relative]position with respect to the visible objectfrom the perspective of the viewer will be opposite to the [relative]position of the two lines along which the two forms originally reached the surface of the eye.