MOGO-Ocular is prismatic aspherical lens that used as conjugate pair and outperforms single lens biocular magnifiers. It is done from PMMA material. For high-end applications it could be machined, polished and coated with Anti-reflection layer, while for cost sensitive applications, Cinema2Go developed special injection molding process. The parameters and drawings of the Injection molded lens are concentrated in the table and figure below
The SDS/ROHS information about PMMA CM 205 is available on-line: http://www.chimeicorp.com/en-us/products/plastics/pmma/
The 3D files for mechanical integration and optical simulation files are available under NDA and cooperation contracting.
Distortions and aberrations due to singlet with strong prismatic element
The MOGO-V1B ocular is aspherical, prismatic singlet used as ocular in wide area, near eye biocular system. In the biocular system the center of the observed object should be shifted toward the temporal side of each eye by corresponding to eye ocular. This shift is done by strong prismatic element in the lens. The optimized aspheric, free form front surface keeps in focus all points of the wide area. The prismatic, apsherical design of lens provides sharp object view and biocular convergence into comfort zone distance. The singlet, however, creates geometrical distortions and chromatic aberrations as below:
In general oculars designed to minimize chromatic and other aberrations and distortions by means of number of lenses. However, for the MOGO-V1B ocular there are tight system constraints for the physical dimension and therefore it is based on singlet lens. Aspherical design minimizes spherical aberrations, however, prismatic element creates geometrical distortions and chromatic aberrations. Left eye ocular is presented on the figure above with its distortions characterization. The right half of the image is almost free of distortions and chromatic aberrations, in the center there are slight vertical distortion and chromatic aberrations that are progressing toward the left edge. The strongest effect happens at the temporal edge where the vertical line is bent in 2mm and the white pixel decomposed to rainbow colors for a strip of 6 pixels for pixel size of ~50μm.
The general use case for the MOGO-oculars is both-eyes enlarger. In both-eyes enlarger a conjugate pair of MOGO-oculars is used and therefore, optical performance is the same for each eye. The main goal of MOGO- oculars in the enlarger is to shift “Object Plane” located very close to the eyes to the distance of the eyes convergence comfort zone – “Virtual Image Plane” (VIP).
For MOGO-Oculars-V1B the VIP distance is 10” that corresponds to 7.8⁰ of inward rotation of each eye (in addition to kappa angle). Monocular power of each ocular corresponds to 12 Diopters, while Prismatic power equivalents to 19 Prismatic Diopters Base In – 12D/19PDBI.
If the Object of observation is 6” smartphone with 16:9 aspect ratio screen it will be perceived as 15” screen at the distance of 10”. The Field of View of such enlarging system is about 90⁰ in Horizontal axis and 45⁰ in Vertical axis. The reason that 16:9 aspect ratios is not preserved is because of stretching of temporal sides of the images.
In order to move further the Virtual Image Plane and release even more binocular convergence, stronger prismatic power is needed. For singlet design, this is a trade-off since that adds thickness to the lens aside with stronger distortions and chromatic aberrations. While in V2 of oculars the the VIP distance will be increased to 23", Cinema2Go performs advanced R&D to address the above issues to provide much better convergence distance while reducing distortions and aberrations, see GEN2.
For application where the object (e.g. movie on smartphone) could be observed for long time it is recommended to position the Object Plane at the focal distance of MOGO-Oculars-V1 in order to emulate monocular infinity and release the eyes accommodation. This distance is 78mm and it is not recommended to reduce that distance more than 10mm that is expected to stimulate 2 Diopters of each eye accommodation and also convergence distance could pass the threshold of convergence comfort zone.
The flat observed object is two-dimensional by definition. However, due to vertical lines distortion and their mirror symmetry between left and right oculars, part of people will notice Pseudo-3D effect, that could be pleasant, neutral or disturbing. Some people, reported disturbing perception of bulging/protruding image in the central area of the screen
The attention for distortions/chromatic aberrations is very application and content dependent. If static desktop of the phone will be observed, most of people will notice above mentioned distortions. However, with a movie running or Drone piloting application streaming live video, absolute majority of the users are just ignoring the distortions. Therefore, for MOGO-Oculars-V1 to be used as Smartphone Screen Enlarging, refer to use-cases of the Compatibility Table below: