• Korean Journal of Optics and Photonics
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• v.29 no.4
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• pp.149-158
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• 2018

A generalized structural design equation can be used to simplify and systematize a telecentric lens system composed of multiple lenses, as a creative design method of the authors. Through this structural equation, we have investigated the feasibility and design methodology of a telecentric lens equipped with a conventional smartphone camera for machine vision. As a result, we could verify and present a useful, generalized structural equation termed the $f{\theta}$ formula, being able to divide and combine the whole telecentric lens system into two modularized lens groups.

• Korean Journal of Optics and Photonics
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• v.24 no.1
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• pp.9-16
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• 2013

We try to find the generalized structural equation that gives a perspective understanding for telecentric lenses through paraxial optical algebraic equations and preconditions from a highly experienced design sense. The equation is named the $f{\theta}$ formula and this formula is applied to single lenses, double Gauss lenses, Cooke triplet lenses and the compound lens composed of a Cooke triplet lens and a double Gauss lens step by step. And this formula is also applied to single fly-eye lenses plus a telecentric lens and double fly-eye lenses plus a telecentric lens in sequence. As a result, we can confirm that this $f{\theta}$ formula leads to intuitive optical design with a structural understanding for telecentric lens systems.

• Korean Journal of Optics and Photonics
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• v.26 no.4
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• pp.217-225
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• 2015

This paper shows the best selection and combination of glass in lens design, to correct a chromatic aberration using achromatic and apochromatic conditions. Using this research result, we have designed a telecentric lens for machine vision in the full range of visible light. We obtain good optical quality in the form of a quite small RMS wavefront error of $0.057{\lambda}$ in the super-broadband wavelength range 380 nm -780 nm. This result is better than that for a common telecentric lens in the visible wavelength range 486.1-656.2 nm.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.7-12
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• 2018

In the field of machine vision, a variety of lenses are used to inspect a product for defects. Only part of the appearance of an object can be photographed with a general lens. Optical components such as mirrors, multiple lenses and cameras are required to inspect the entire exterior. This increases the size of the optical system, and has the disadvantage of high cost. In this paper, we design a hypercentric lens, which can photograph the top and side of an object, and various sizes of objects while maintaining the image size. Also, the validity of the design is verified through the performance analysis of the product.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.63-71
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• 2021

Recently, high-resolution cameras in smartphones enable measurement of minute objects such as cracks in concrete using image processing techniques. The technology to investigate the crack width using an application at an adjacent distance of the close shot range has already been implemented, but the use is limited, so it is necessary to verify the usability of the high-resolution smartphone camera to measure cracks at a longer distance. This study focuses on recognizing the size of subdivided crack widths at a thickness within 1.0 mm of crack width at a distance of 2 m. In recent Android-based smartphones, an experiment was conducted focusing on the relationship between the unit pixel size, which is a measurement component, and the shooting distance, depending on the camera resolution. As a result, it was possible to confirm the necessity of a smartphone lens for the classification and quantification of microcrack widths of 0.3 mm to 1mm. The universal telecentric lens for smartphones needed to be installed in an accurate position to minimize the effect of distortion. In addition, as a result of applying a 64 MP high-resolution smartphone camera and double magnification lens, the crack width could be calculated within 2 m in pixel units, and crack widths of 0.3, 0.5, and 1mm could be distinguished.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.197-202
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• 2002

In this paper, we want to help understanding about telecentric as introducing the concept of the system and researching the optical properties after we choose the designed profile projection lens. An analyzed optical system is F-number=2.8 and the first lens is used negative lens. Accordingly, we can know this system is compacter, because the front focal position is to the inside of the system and aperture stop is designed to the inside of the optical system. The field is about $21^{\circ}$. Since the entrance pupil is located the front focal point, we can certify the exit pupil is -49404.1mm, located on the infinite toward the object space. Therefore, the optical system is the form of 'image space telecentricity'.

• Progress in Medical Physics
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• v.27 no.2
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• pp.72-78
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• 2016

A CCD camera and an LED light source were combined to fabricate a compact optical CT scanner for the therapeutic radiation dose evaluation of a polymer gel dosimeter. After the collimated beam emitted by the LED passed through aquarium, gel phantom, and telecentric lens, an image was collected by the CCD camera and reconstructed using MATLAB. By using a stepping motor and LabVIEW, the gel dosimeter was rotated at every $0.72^{\circ}$, and the time for collecting 500 slice images per a revolution was within 20 min. At a spatial frequency of 4.5 lp/mm of the optical CT scanner, the modulation transfer function value was 72%. The linear correlation coefficient of the optical CT scanner for the polymer gel dosimeter was 0.987.