Aberration-Based Quality Metrics in Holographic Lenses

Abstract

Aberrations and the image quality of holographic lenses were evaluated by a Hartmann-Shack (HS) wavefront sensor. Two lenses, one recorded with a symmetrical configuration and the other with an asymmetrical one, were stored in a photopolymer called Biophotopol. Each was reconstructed with two different wavelengths, 473 nm and 633 nm. Different metrics were applied to determine and quantify the aberration of the lenses (Zernike coefficients, Seidel coefficients, Marechal tolerances, root-mean-square (RMS), peak to valley, critical fraction of the pupil), and the quality of the image they provided (Strehl ratio, entropy, cutoff frequency, modulation transfer function (MTF), and area under the MTF). Good agreement between the metrics related to optical quality was obtained. The negative asymmetric holographic lenses had less aberration than the positive symmetric ones.

Keywords: aberrations; holographic lenses; low toxicity photopolymer; optical quality.

Figure 1

Holographic storage recording process (488 nm) with symmetric (a) and (b), and asymmetric (c) and (d) recording beams; and with positive (a) and (c), and negative (b) and (d) focal points.

Figure 2

Holographic storage reconstruction (473 nm and 633 nm) of symmetric (a) and (b), and asymmetric (c) and (d) geometry; and with positive (a) and (c), and negative (b) and (d) focal points.

Figure 3

(a) Photography of a negative asymmetric volume phase transmission holographic lens observed by reflection illuminated with daylight. A single-color image is observed because it shows by reflection the area in which the evaluated holographic lens is located, (b) chromatic dispersion is watching in the same holographic lens working by transmission with a white conjugate collimated beam.

Figure 4

Experimental setup for the evaluation of the aberrated wavefront of holographic lenses. F: filter, SF: spatial filter, L: lens, D: diaphragm, HL: holographic lens, HS Sensor: Hartmann–Shack wavefront sensor.

Figure 5

Wavefront aberration ($W$) of positive symmetrical (a) and (b), and negative asymmetrical (c) and (d); HLs reconstructed at 633 nm (a) and (c), and at 473 nm (b) and (d).

Figure 6

Theoretical and experimental Seidel coefficient spherical aberration (S), coma (C), and astigmatism (A) (blue and red), and Marechal tolerances (green) of the positive symmetrical (a) and (b), and the negative asymmetrical (c) and (d); HLs recorded at 633 nm (a) and (c), and at 473 nm (b) and (d).

Figure 7

Simulated modulation transfer function (MTFs) for positive symmetrical (a) and (b), and negative asymmetrical (c) and (d); HLs reconstructed at 633 nm (a) and (c), and at 473 nm (b) and (d). A cut in x (red), cut in y (blue), and limited by diffraction (green). A zoom of these curves at a limiting resolution of 0.01 is included.