scholarly journals A cute and highly contrast-sensitive superposition eye - the diurnal owlfly Libelloides macaronius

2013 ◽  
Vol 216 (11) ◽  
pp. 2081-2088 ◽  
Author(s):  
G. Belusic ◽  
P. Pirih ◽  
D. G. Stavenga
Keyword(s):  
Superposition Eye

scholarly journals Artificial neural superposition eye

2007 ◽  
Vol 15 (19) ◽  
pp. 11922 ◽  
Author(s):  
Andreas Brückner ◽  
Jacques Duparré ◽  
Peter Dannberg ◽  
Andreas Bräuer ◽  
Andreas Tünnermann
Keyword(s):  
Superposition Eye ◽  
Neural Superposition ◽  
Artificial Neural

Physiological optics in the hummingbird hawkmoth: a compound eye without ommatidia

1999 ◽  
Vol 202 (5) ◽  
pp. 497-511 ◽  
Author(s):  
E. Warrant ◽  
K. Bartsch ◽  
C. Günther
Keyword(s):  
Spatial Resolution ◽  
Compound Eye ◽  
High Sensitivity ◽  
Diffraction Limit ◽  
Physiological Optics ◽  
Macroglossum Stellatarum ◽  
Superposition Eye ◽  
Eye Region

The fast-flying day-active hawkmoth Macroglossum stellatarum (Lepidoptera: Sphingidae) has a remarkable refracting superposition eye that departs radically from the classical principles of Exnerian superposition optics. Unlike its classical counterparts, this superposition eye is highly aspherical and contains extensive gradients of resolution and sensitivity. While such features are well known in apposition eyes, they were thought to be impossible in superposition eyes because of the imaging principle inherent in this design. We provide the first account of a superposition eye where these gradients are not only possible, but also produce superposition eyes of unsurpassed quality. Using goniometry and ophthalmoscopy, we find that superposition images formed in the eye are close to the diffraction limit. Moreover, the photoreceptors of the superposition eyes of M. stellatarum are organised to form local acute zones, one of which is frontal and slightly ventral, and another of which provides improved resolution along the equator of the eye. This angular packing of rhabdoms bears no resemblance to the angular packing of the overlying corneal facets. In fact, this eye has many more rhabdoms than facets, with up to four rhabdoms per facet in the frontal eye, a situation which means that M. stellatarum does not possess ommatidia in the accepted sense. The size of the facets and the area of the superposition aperture are both maximal at the frontal retinal acute zone. By having larger facets, a wider aperture and denser rhabdom packing, the frontal acute zone of M. stellatarum provides the eye with its sharpest and brightest image and samples the image with the densest photoreceptor matrix. It is this eye region that M. stellatarum uses to fixate flower entrances during hovering and feeding. This radical departure from classical Exnerian principles has resulted in a superposition eye which has not only high sensitivity but also outstanding spatial resolution.

The Influence of Pigment Migration on Vision of Higher Crustacea

1957 ◽  
Vol 34 (4) ◽  
pp. 447-463
Author(s):  
G. H. P. DE BRUIN ◽  
D. J. CRISP
Keyword(s):  
Visual Acuity ◽  
Refractive Index ◽  
Light Adaptation ◽  
Surrounding Medium ◽  
Light Sensitivity ◽  
Detectable Change ◽  
Corneal Surface ◽  
Pigment Migration ◽  
Wave Guides ◽  
Superposition Eye

1. Exner believed that the movement of the distal pigment during light-adaptation improved the visual acuity of the superposition eye. This hypothesis was tested by measurement of the visual acuity of Leander serratus, Pandalus montagui and Praunus flexuosus under different conditions. 2. When a dark-adapted animal is placed in the light the proximal pigment migrates into the light-adapted position more rapidly than the distal pigment. The distal pigment, but not the proximal pigment, undergoes diurnal rhythm and tends to migrate into the dark-adapted position at night, even when the animal is illuminated. The visual acuity may therefore be tested when the distal pigment is still in the dark-adapted position and the proximal pigment in the light-adapted position. 3. No difference in visual acuity could be detected as a result of changes in the position of the distal pigment. 4. Visual acuity increases and light sensitivity decreases when the dark proximal pigment migrates over the reflecting (tapetal) layer. 5. Eupagurus bernhardus, which lacks the typical tapetum, shows no detectable change in visual acuity or sensitivity after being kept in the dark. 6. These experiments do not support Exner's view of the function of the distal pigment. They indicate that visual acuity is improved by the presence of the dark proximal pigment at the base of the proximal retinulae, probably because this pigment reduces stray reflexions from the back of the eye (halation). 7. It is suggested that since the crystalline cones and crystalline tracts form optically continuous strands with a higher refractive index than that of the surrounding medium they may act as wave guides. If so they would retain light entering the corneal surface from sources close to the axis of the ommatidium, and so concentrate it on the rhabdomes and adjacent retinulae.

The Absolute Sensitivity of Lens and Compound Eyes

1974 ◽  
Vol 29 (9-10) ◽  
pp. 592-596 ◽  
Author(s):  
Kuno Kirschfeld
Keyword(s):  
Exceptional Case ◽  
Compound Eyes ◽  
Absolute Sensitivity ◽  
Human Eye ◽  
Light Quanta ◽  
Different Types ◽  
Superposition Eye ◽  
The Absolute

Abstract The numbers of light quanta available to photoreceptors of lens-and different types of com­ pound eyes are calculated on the basis of photometric considerations. It is shown that the results depend upon the situation in the optical environment: For point-like lightsources such as stars receptors in compound eyes generally receive considerably less numbers of light quanta compared n. g. with the human eye. This is due to the small sizes of the ommatidial facets. For extended optical surroundings, however, the numbers of quanta reaching the receptors in typical insect compound eyes of the apposition type are comparable to those in the human eye. In this respect the optical superposition eye of nocturnal insects like E ph estia is an exceptional case, where there is an improvement in the numbers of quanta reaching the receptors by a factor 100 to 1000 com­ pared to the eyes of bee or man

Investigation of the Screening Pigment System in the Compound Eye of the Moth Agrotis segetum (fam. Noctuidae) by Visible Reflectometry

1987 ◽  
Vol 42 (1-2) ◽  
pp. 152-156 ◽  
Author(s):  
Trond Nordtug ◽  
Thor Bernt Melø
Keyword(s):  
Light Adaptation ◽  
Compound Eye ◽  
Extinction Spectrum ◽  
Light Extinction ◽  
Agrotis Segetum ◽  
Lag Phase ◽  
Reflection Spectroscopy ◽  
Screening Pigment ◽  
Reflected Light ◽  
Superposition Eye

Abstract The functional properties of the light adaptation system in the superposition eye of the moth Agrotis segetum have been investigated by reflection spectroscopy. The spectrum of the reflected light from the tapetum of dark adapted eyes had a peak at about 580 nm corresponding to a spacing between the reflecting layers in the tapetum of 145 nm. During light adaptation of the eye the observed reflectance changes could be explained by light extinction in one screening pigment. The shape of the extinction spectrum of the screening was constant throughout the adaptation process and after a lag phase the optical density of the pigment in the light path increased linearly with time. The screening pigment caused light extinction both by absorption and to some degree also by scattering. The absorption spectrum of the screening pigment had a broad maximum about 590 nm and the scattering efficiency of the pigment particles seemed to be nearly independent of the wavelength.

Retinula cell responses in a moth superposition eye

1983 ◽  
Vol 220 (1218) ◽  
pp. 47-68 ◽  
Keyword(s):  
Dynamic Range ◽  
Spatial Interaction ◽  
Cell Movement ◽  
Polarization Sensitivity ◽  
Cell Responses ◽  
Temporal Properties ◽  
Intensity Range ◽  
Green Background ◽  
Superposition Eye ◽  
Temporal Interaction

The lack of photoreceptor cell movement upon stimulation in a group of moths made possible the direct electrophysiological measurement of the photoreceptor properties in a moth superposition eye. The 13–16 retinula cells of the ommatidium are usually coupled in twos or threes. There are strong antagonistic electrical interactions at the receptor level. The measured acceptance angles (Δ ρ ) of the best units are in the range 1.6-1.8°. Spectral sensitivity peaks lie near 380 and 520 nm. Some units have positive-going responses to some colours and negative-going responses to others. Polarization sensitivity is usually low, but is high if tested at a suitable wavelength in a unit showing colour opponency. The dynamic range (10-90%, length of slope) of the V /lg I curve is over 100-fold intensity range for purely ultraviolet or green-sensitive units; over 10 4 -fold for some units with responses in opposite directions to different wavelengths, and over a 10 6 -fold intensity range for units with negative-going responses at all wavelengths. The wide ranges are attributed to strong antagonistic interactons between receptors. Despite the superposition optics, the retinula cells are approximately the same sensitivity (in terms of millivolts per peak axial photon) as those of a diurnal apposition eye under the same conditions. The electrical interaction between different receptors has the effect of reducing the responses to light that is unpolarized, white, diffuse, or simultaneously applied, and of emphasizing responses to light that is polarized, coloured, localized or successively applied. Tests with a movable point source and a surround reveal several effects of the opponency between receptors by a single mechanism. Edges are emphasized by spatial interaction and differences between colours are emphasized by interaction within ommatidia. On a green background, small objects of a different colour will stand out. With certain wavelength combinations, the temporal properties are enhanced. The adaptive advantage of the diurnal superposition eye, from these measurements, is that it provides a higher intensity at the photoreceptors that in turn makes possible a greater degree of inhibitory spatial and temporal interaction at the primary photoreceptor level.

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