=Paper=
{{Paper
|id=Vol-2744/short46
|storemode=property
|title=Development of Telescopic Glasses Optical System Based on Polymer Lens (short paper)
|pdfUrl=https://ceur-ws.org/Vol-2744/short46.pdf
|volume=Vol-2744
|authors=Alisa Ekimenkova,Anna Voznesenskaya
}}
==Development of Telescopic Glasses Optical System Based on Polymer Lens (short paper)==
https://ceur-ws.org/Vol-2744/short46.pdf
Development of Telescopic Glasses Optical System Based
on Polymer Lens*
Alisa Ekimenkova[0000-0001-5847-7918], Anna Voznesenskaya[0000-0002-4074-4341]
ITMO University, 197101, Russia, St. Petersburg, Kronverksky av., 49
asekimenkova@itmo.ru, voznesenskaya@itmo.ru
Abstract. Polymeric materials are actively used to upgrade existing optical de-
vices in order to improve their physical and optical properties. High-tech and
relatively cheap polymer optics is a means of solving technical problems related
to reduction of assembly labor intensity, improvement of design and reliability
of various optical systems. Currently, ophthalmology is the most advanced area
for polymer technology development. The defining trend of improving specta-
cle optics is gradual replacement of lenses made of silicate glass with lenses
made of polymer materials, the undoubted advantages of which are almost
twice lower density and significant impact resistance. This work is devoted to
the development of an optical system of telescopic glasses of small multiplicity,
made by the scheme Galileo using modern optical polymers. The device is de-
signed to improve the performance of the eye and can be used for medical oper-
ations. The calculation of the presented optical system is carried out by the Ze-
max program. The resulting optical system is characterized by high image qual-
ity, light weight and compactness.
Keywords: Optical Polymers, Medical Optics, Telescopic Glasses, Optimiza-
tion, Aspherical Lenses.
1 Introduction
In order to improve the eye performance, telescopic glasses with relatively small
magnification are used (Fig.1). Such systems have found wide application in medi-
cine, for manufacture of microelectronic schemes and jewels. The special requirement
at development of glasses is elimination of necessity for additional accommodation of
eyes at transition from observation with glasses and without them. This criterion is
achieved due to the location of the object and image in one plane [1-2]. Telescopic
glasses guarantee high image clarity without distortion and excessive strain on the
eyes, in view of manufacturing strictly in accordance with the individual characteris-
tics of the operator. Image transmission quality is achieved by using premium optics.
Copyright © 2020 for this paper by its authors. Use permitted under Creative Commons Li-
cense Attribution 4.0 International (CC BY 4.0).
* Publication financially supported by RFBR grant №20-01-00547
2 A. Ekimenkova, A. Voznesenskaya
However, traditional glass lenses have a considerable mass, which is a serious disad-
vantage when glasses are worn for a long time. Therefore, when calculating the opti-
cal system, it is necessary to ensure low weight and small size for efficient operation
[3].
To reduce the mass and dimensional characteristics, the calculation of telescopic
glasses optical system based on polymer lenses is proposed. Modern optical polymers
have high transparency and refractive power comparable to that of crown glasses. The
specific gravity of plastic is almost half that of glass, which allows the polymer lenses
to be much lighter. Currently, polymeric materials have many advantages over miner-
al glass: low weight, injury safety, high impact resistance and low cost. Besides, today
the technologies of production and processing of optical polymers enable to create
complex surfaces (diffraction, aspherical, "freeform"), providing compensation of
aberrations and transformation of the beam shape [4].
Fig. 1. Telescopic glasses
2 Ophthalmologic optical polymers
Ophthalmology is the most common field of application of polymer optics as a means
of vision correction and eye protection. The main task of eyeglass optics is to ensure
completely natural vision for their wearer. The materials used in the manufacture of
corrective lenses must comply with a number of requirements [5]:
• high indexes of refraction and dispersion;
• low reflection and light scattering coefficients for the visible range;
• low transmittance of ultraviolet and infrared radiation;
• small density;
• high hardness;
Development of Telescopic Glasses Optical System Based on Polymer Lens 3
• chemical resistance to humid atmospheres;
• low internal voltage;
• easy to handle.
It should be noted that some of these requirements contradict each other and the mate-
rial with the highest values for all these parameters has not yet been developed.
The fundamental characteristic of glasses is the refractive index n of material, as
the thickness of the lenses directly depends on this value. The greater the refractive
index, the finer optics can be manufactured. In addition, the value n also affects the
optical power of the lens.
The optical properties of polymer materials for glasses lenses are commensurate with
those of traditional glasses. However, the level of light dispersion of polymers is
higher and can be manifested by coloring the contour of the object when viewed
through the peripheral areas. Nevertheless, as a rule, this defect is not fundamental for
most eyeglass wearers. In order to improve functional and operational characteristics
of polymer lenses, special coatings are used: to increase wear resistance of polymer
material, as a protection, etc. The polymeric materials are used for spherical and as-
pherical lenses, astigmatic and astigmatic lenses, monofocal lenses, bifocal lenses and
lenses of various diameters (60-75 mm), which can be used for frames of any size [6].
In recent years, there has been a rapid development in the field of high molecular
chemical compounds, which has led to the development of optical polymer materials
with a refractive index above 1.7. At the same time, the increase of refractive index
does not indicate the growth of material density. Today, mineral lenses have the high-
est refractive index of 1.90, while polymer lenses have a refractive index of 1.74.
Organic materials with such refractive index are produced by the Japanese company
Mitsui Chemicals [7]. The line of optical polymers of this company MRTM is intended
for manufacturing of ophthalmic lenses. Due to its unique physical properties and
characteristics, it allows creating thin and aesthetic eyeglass lenses, even taking into
account the high optical power of components.
Table 1. Optical and mechanical properties of polymer materials
Material PMMA Polyester PS PC COC, MR-174 K8
COP
Refractive index 1,491 1,607 1,590 1,585 1,533 1,743 1,516
(λ = 633 nm)
Abbe number 57 27 31 30 58 32 64
Birefringence, 4 2 10 7 2 2 1
(on a scale of 1 to
10)
Transmission, % 96 94 90 89 92 97 92
Density, g/cm3 1,8 1,22 1,05 1,25 0,95 1,38 2,51
Maximum operat- 85 125 75 120 150 78 >400
ing temperature,
ºC
Water absorption, 0,3 0,15 0,1 0,2 <0,01 0,1 0
%
Thermal expan- 60 72 50 68 60 61 7,1
sion coefficient,
·10-4 /°C
4 A. Ekimenkova, A. Voznesenskaya
Table 1 shows the optical and mechanical properties of the most commonly used pol-
ymer materials: polymethylmethacrylate (PMMA), polyester, polystyrene (PS), cyclo-
olefin (co)polymers (COC & COP), MR-174 and K8 glass [8]. It should be noted that
thermal properties of polymers unfavorably differ from glass characteristics, however,
plastic density is almost 1.5 times lower, and optical properties of materials are com-
parable and not inferior to each other.
3 Telescope glasses calculation
Optical system of telescopic glasses is arranged according to Galileo's scheme that
does not require wrapping elements (Fig. 2).
Fig. 2. Principal optical circuit in thin components
The calculation principle for optical systems is based on the method of automatic
aberration correction. Initially, the system dimensional calculation is performed and
optimization parameters are formed. Then tracing rays in the initial scheme is realized
and, if necessary, optimization parameter limits are changed for the purpose of recep-
tion for the best quality of the image and observance of design requirements. Table 2
shows the original characteristics of the optical system, which were determined based
on the design features. The magnification β of similar systems is in the 1.5 - 3ˣ, the
distance from the main plane of the first component to the plane of objects and images
a usually take from 300 to 400 mm. The distance between the main planes of the
components d is determined for structural reasons. As this parameter increases, the
relative diameters of the lenses are reduced, making it easier to correct aberrations.
However, as d rises, the total system size also becomes larger. The focal distances of
f'1 and f'2 components are determined using the basic formulas of geometric optics [9].
Development of Telescopic Glasses Optical System Based on Polymer Lens 5
Table 2. Primary characteristics of the optical system
β, ˣ a, mm d, mm f’1, mm f’2, mm
3 350 30 41,45 -16.29
The original glasses system includes positive and negative elements. To minimize
chromatic aberrations, optical materials should be selected so that the dispersion coef-
ficients are varied as much as possible. In addition, the Abbe value of the positive
component should be higher than that of the negative component [10-11].
During the analysis of modern optical polymer materials and their optical and me-
chanical properties, the most beneficial components were determined. The final opti-
cal system has the following parameters: the first component is a pair of positive
lenses made of E48R polymer (ne = 1,531, νe = 56) of Zeonex commercial brand [12].
This material is a cycloolefin polymer and provides high optical performance. The
second component is a negative lens made of specialized ophthalmologic material
MR-174 (ne = 1,743, νe = 32) [7]. Table 3 shows the design parameters of the optical
system. Figure 3 illustrates the optical scheme of polymer telescopic glasses.
Table 3. Optical system design parameters
Surf. Curvature Axial distance, Material Refractive e2
№ radius, mm mm index
1 39,610 2,545 E48R 1,531
2 85,126 0,089 AIR 1
3 28,088 4,678 E48R 1,531
4 373,926 14,633 AIR 1
5 -62,670 3,566 MR-174 1,743 -10,416
6 25,949 1,030
β = 1,9ˣ
2ω’ = 7º
f’1 = 40,628 mm
f’2 = -24,102 mm
Fig. 3. Optical circuit of polymer telescopic glasses
6 A. Ekimenkova, A. Voznesenskaya
Optimization of the optical system has allowed correction of monochromatic aberra-
tions (spherical, coma, image curvature, distortion and astigmatism). Due to the small
aperture of the optical system (A = 0,01) the residual monochromatic axial aberrations
are insignificant, image quality is determined by the size of the diffraction circle (Fig.
4).
Fig. 4. Spot diagram of scattering
4 Conclusion
The resulting optical system has a high image quality, with the mass of polymer
glasses less than 50% of weight of glass analogues. The configuration includes lenses
made of modern optical polymers with high index of refraction and dispersion. The
technique of manufacturing lenses from optical plastics allows you to make surfaces
of complex shape, providing high quality components and low cost.
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Development of Telescopic Glasses Optical System Based on Polymer Lens 7
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Last accessed 21 June 2020
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