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Abstract:
The transfer properties of the optical system in the arthropod compound eye are determined by the interommatidial angle Δ ϕ, influencing the resolving power, and by the width of the visual fields of single ommatidia Δ ϱ, influencing the response at high spatial frequencies of brightness distributions in the object space. The energy transfer/ receptor is proportional to (Δϕ Δ ϱ)2 and decreases with in-inreasing approximation of the perfect-imaging condition: gDϕ → 0; Δϱ → 0. However, a value Δϕ Δϱ > 0 has to be maintained in order to overcome the threshold of nervous excitation at a certain minimum-brightness level. Theoretical treatment yields Δϱ/Δϕ=0.62 to 0.88 as the corresponding optimum-imaging relation. The actual ratio can be derived from measurements of the optomotor reactions to the movement of periodic brightness patterns. The approximate value 0.76 is obtained from the fruitfly Drosophila with normal and mutant eye pigmentation. As a result, the parameters of this imaging system are found to be established in a way that enables optimum performance at sufficient illumination. An dieser Stelle möchte ich Dr. W. Reichardt für sein eingehendes Interesse und manche anregende Diskussion über die Sehvorgänge im Komplexauge meinen Dank sagen. Dr. K. Kirschfeld verdanke ich ebenfalls wertvolle Hinweise. Herrn E. Freiberg bin ich für die Anfertigung der Abbildungen sehr verbunden.
