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Optics of Refractometers for Refractive Power Measurement of the Human Eye
Ko, Dong-Seob,Lee, Byeong-Ha Optical Society of Korea 2006 Current Optics and Photonics Vol.10 No.4
In the field of ophthalmology, many diagnostic instruments based on optical technology have been developed, such as refractometer, keratometer, corneal mapper, tonometer, fundus camera, slit lamp, laser scan ophthalmoscope and optical coherence tomography. Among them, the refractometer that is used for measuring the refractive power of the human eye has the long research history and various types have been developed. However the efforts to realize more accurate and precise measurement are still in progress. The wavefront analyzer commercialized in recent years is an excellent outcome of such efforts. In this paper, a brief account of the developmental history of various refractometers including the wavefront analyzer is summarized, and the underlying measurement principle is introduced in the view of optics. Finally, the technical issues that should be solved for getting better performance are discussed.
Image Quality Evaluation and Tolerance Analysis for Camera Lenses with Diffractive Element
Lee, Sang-Hyuck,Jeong, Ho-Seop,Jin, Young-Su,Song, Seok-Ho,Park, Woo-Je Optical Society of Korea 2006 Current Optics and Photonics Vol.10 No.3
A novel image quality evaluation method, which is based on combination of the rigorous grating diffraction theory and the ray-optic method, is proposed. It is applied for design optimization and, tolerance analysis of optical imaging systems implementing diffractive optical elements (DOE). The evaluation method can predict the quality and resolution of the image on the image sensor plane through the optical imaging system. Especially, we can simulate the effect of diffraction efficiencies of DOE in the camera lenses module, which is very effective for predicting different color sense and MTF performance. Using this method, we can effectively determine the fabrication tolerances of diffractive and refractive optical elements such as the variations' in profile thickness, and the shoulder of the DOE, as well as conventional parameters such as decenter and tilt in optical-surface alignments. A DOE-based 2M-resolution camera lens module designed by the optimization process based on the proposed image quality evaluation method shows ${\sim}15%$ MTF improvement compared with a design without such an optimization.
Kim, Chul Han Optical Society of Korea 2019 Current Optics and Photonics Vol.3 No.3
The allowable path-deviation time of aircraft in a free-space optical communication system has been estimated from various trajectories, using different values of aircraft speeds and turn rates. We assumed the existence of a link between the aircraft and a ground base station. First, the transmitter beam's divergence angle was calculated through two different approaches, one based on a simple optical-link equation, and the other based on an attenuation coefficient. From the calculations, the discrepancy between the two approaches was negligible when the link distance was approximately 110 km, and was under 5% when the link distance ranged from 80 to 140 km. Subsequently, the allowable path-deviation time of the aircraft within the tracking-error tolerance of the system was estimated, using different aircraft speeds, turn rates, and link distances. The results indicated that the allowable path-deviation time was primarily determined by the aircraft's speed and turn rate. For example, the allowable path-deviation time was estimated to be ~3.5 s for an aircraft speed of 166.68 km/h, a turn rate of $90^{\circ}/min$, and a link distance of 100 km. Furthermore, for a constant aircraft speed and turn rate, the path-deviation time was observed to be almost unchanged when the link distance ranged from 80 to 140 km.
Kang DongKyun,Yoo HongKi,Lee SeungWoo,Gweon Dae-Gab Optical Society of Korea 2005 Current Optics and Photonics Vol.9 No.1
In light microscopy, spatial resolution is limited by diffraction effect. Confocal microscopy has improved resolutions in both lateral and axial directions, but these are still limited by diffraction effect. Confocal self-interference microscopy (CSIM) uses interference between two perpendicularly polarized beams to enhance lateral resolution. In previous research, we proposed a calcite plate with its optic-axis perpendicular to the propagation angle and one of the boundary surfaces of the plate. This type of plate is not widely used to our knowledge. In this paper, we change the calcite plate to more common one, which is commercially available. This calcite plate has its optic axis in the plane of incidence. We analyze the characteristics of this calcite plate and numerically compare the performances of CSIM in previous research and CSIM with the commercial calcite plate. Numerical results show improved performance when using the commercial calcite plate
Study of the Key Technology of Ghost Imaging Based on Rosette Scanning
Zhang, Leihong,Kang, Yi,Pan, Zilan,Liang, Dong,Li, Bei,Zhang, Dawei,Ma, Xiuhua Optical Society of Korea 2017 Current Optics and Photonics Vol.1 No.5
Ghost imaging offers great potential, with respect to standard imaging, for imaging objects in optically harsh or noisy environments. It can solve the problems that are difficult to solve by conventional imaging techniques. Recently, it has become a hot topic in quantum optics. In this paper, we propose a scheme for ghost imaging based on rosette scanning, named rosette ghost imaging. Sampling a small area sampling instead of the whole object, the instantaneous field of view of rosette scanning is used as the modulation light field in ghost imaging. This scheme reduces energy loss, the number of samples, and the sampling time, while improving the quality of the reconstructed image.
High Repetition Wavelength-locked 878.6 nm LD Dual-end-pumped Nd:YVO<sub>4</sub> 1064 nm Laser
Li, Yue,Yu, Yong-Ji,Wang, Yu-Heng,Liu, Hang,Liu, He-Yan,Jin, Guang-Yong Optical Society of Korea 2018 Current Optics and Photonics Vol.2 No.6
A $Nd:YVO_4$ laser dual-end-pumped by a wavelength-locked 878.6 nm laser diode is presented. At the repetition rate of 500 KHz, the absorbed pump power of 58 W, an output power of 26.1 W at 1064 nm is obtained, corresponding to an optical-optical efficiency of 45%. The pulse width is 44.2 ns. Meanwhile, the effects of traditional 808 nm pumping and 878.6 nm dual-end-pumping on the output laser beam quality and pulse width are compared and analyzed in an experiment.
Spectra of Optical-field Ionized Gases by a Femtosecond Ti:Sapphire Laser
Mock, Tomas,Shin, Hyun-Joon,Cha, Yong-Ho,Lee, Dong-Gun,Hong, Kyung-Han,Nam, Chang-Hee Optical Society of Korea 1998 Current Optics and Photonics Vol.2 No.2
We report on the spectroscopic investigation of optical-field ionized plasmas in the soft X-ray spectral region. The experiment was carried out by focusing pulses of the high-power Ti:Sapphire laser with an energy of ~ 40 mJ and time duration of ~30 fs into a gas jet of krypton, xenon, and argon from a pulsed nozzle. Strong soft X-ray emission on lines from ionic stages of $Kr^{7+} , Kr^{8+} , Xe^{7+} , Ar^{7+} , and Ar^{8+}$ is reported. The experimental result was found to be in good agreement with theoretical prediction.
Auto-focus Control by Chromatic Filtering in Laser Welding
Kim, Cheol-Jung,Baik, Sung-Hoon,Kim, Min-Suk,Chung, Chin-Man,Kim, Kwang-Jung Optical Society of Korea 2000 Current Optics and Photonics Vol.4 No.2
Optical monitoring using the chromatic aberration of focusing optics is applied to auto-focus control in laser welding. The spectral transmittance of thermal radiation from a weld pool through an aperture depends on the wavelength of the spectral band and on the distance of the weld pool from the focusing optics. Its dependence has been used to monitor the focus shift in laser welding by measuring the spectral band signals filtered by the aperture. The difference between pulsed and continuous laser welding is analyzed. Furthermore, the dependence of the focus shift monitoring on the weld pool size variation is optimized to monitor the focus shift independently from the laser power change at the weld pool. The performance of the auto-focus control with chromatic filtering is presented for pulsed laser welding.
Development of Prototype Stylus Prototype for Large Optics Testing
Yang, Ho-Soon,Walker, David Optical Society of Korea 2001 Current Optics and Photonics Vol.5 No.2
The authors discuss a prototype stylus profilometer designed to measure large optics. It consists of a low contact force type probe system, laser reference system, interferometric distance measurement system, and horizontal driving system. The probe contacts the surface ; the height and the horizontal distances of the measurement points are measured by the interferometer. The freely propagated laser beam provides the reference line during the measurement. The developed stylus profilometry shows only $\pm$60 nm of P-V error for the 157 mm diameter spherical mirror.
Coherent Optical Receiver for Real-time CO-ORMDM Systems
Jae Seung, Lee Optical Society of Korea 2023 Current Optics and Photonics Vol.7 No.1
We propose a new coherent optical receiver (COR) to detect optical receiver mode (ORM) subchannels selectively in coherent optical (CO) ORM division multiplexing (ORMDM) systems. In the CO-ORMDM systems, each optical channel is a linear sum of ORM subchannels, to obtain high spectral efficiencies (SEs). The COR uses an ORM subcarrier as its local oscillator (LO) and reads the transmitted data at the origin times of ORM signals. For example, if the m<sup>th</sup> ORM subcarrier is used as the LO, then the COR reads the data of the m<sup>th</sup> ORM subchannel. The proposed COR is fast and can make CO-ORMDM systems useful for real-time optical communication with high SE.