Computation of Analytical Zoom Locus Using Padé Approximation

Kim, Kang Min; Choe, Sun-Ho; Ryu, Jae Myung; Choi, Hojong

doi:10.3390/math8040581

Cited by 12 publications

(13 citation statements)

References 29 publications

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“…For this reason, we can con Figure 7 shows the MTF curve of the collimator designed and shown in Figure 5. The MTF graph must be utilized to verify the optical system performance because the MTF represents the optical aberrations and resolutions of the optical systems [30][31][32][33]. Figure 7 shows that the x-axis of each graph represents the movement of the image sensor assembled on the test lens, and this represents the defocus.…”

Section: Resultsmentioning

confidence: 99%

Optical Design of a Novel Collimator System with a Variable Virtual-Object Distance for an Inspection Instrument of Mobile Phone Camera Optics

2021

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The resolution performance of mobile phone camera optics was previously checked only near an infinite point. However, near-field performance is required because of reduced camera pixel sizes. Traditional optics are measured using a resolution chart located at a hyperfocal distance, which can only measure the resolution at a specific distance but not at close distances. We designed a new collimator system that can change the virtual image of the resolution chart from infinity to a short distance. Hence, some lenses inside the collimator systems must be moved. Currently, if the focusing lens is moved, chromatic aberration and field curvature occur. Additional lenses are required to correct this problem. However, the added lens must not change the characteristics of the proposed collimator. Therefore, an equivalent-lens conversion method was designed to maintain the first-order and Seidel aberrations. The collimator system proposed in this study does not move or change the resolution chart.

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Section: Resultsmentioning

confidence: 99%

Optical Design of a Novel Collimator System with a Variable Virtual-Object Distance for an Inspection Instrument of Mobile Phone Camera Optics

2021

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“…3a. Here, the singlet was designed by the method mentioned in [42][43][44]. In the optical system shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Fisheye lens design for solar-powered mobile ultrasound devices

Ryu

Choi

2022

THC

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BACKGROUND: Compared to benchtop ultrasound machines, mobile ultrasound machines require portable batteries when acquiring information regarding human tissues during outdoor activities. OBJECTIVE: A novel fisheye lens type was designed to address the charging issue where it is difficult to constantly track the sun. This method does not require the use of a mechanical motor that constantly tracks the sun to charge the portable batteries. METHODS: To obtain an optical solar power system, the numerical aperture (NA) and field angle must be increased. Therefore, we use the fisheye lens with the largest field angle. RESULTS: The NA of the designed fisheye lens system reaches 0.75, allowing light collection of approximately ± 48∘. Additionally, the efficiency ratio of the central and surrounding areas also satisfies more than 80% at a field angle of 85∘ and more than 70% at field angles of 85∘ to 90∘, respectively. CONCLUSIONS: We designed a novel fisheye lens for solar-powered mobile ultrasound machines used outdoors.

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“…The signal distortions that are present during the amplifier design in a high-voltage and high-current environment make it difficult to accurately predict the performance of the amplifiers [ 65 , 66 , 67 , 68 ]. In addition, the output performance of the amplifier in the experiments may fluctuate widely owing to external environmental factors such as the heat and power level parameters [ 41 , 57 , 69 ]. Consequently, the theoretical analysis of the amplifier and post-voltage-boost circuit should be verified using actual measurement data.…”

Section: Methodsmentioning

confidence: 99%

Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications

Kim

You

Choi

2020

Sensors

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Piezoelectric transducers are important devices that are triggered by amplifier circuits in mobile ultrasound systems. Therefore, amplifier performance is vital because it determines the acoustic piezoelectric transducer performances. Particularly, mobile ultrasound applications have strict battery performance and current consumption requirements; hence, amplifier devices should exhibit good efficiency because the direct current (DC) voltage in the battery are provided to the supply voltages of the amplifier, thus limiting the maximum DC drain voltages of the main transistors in the amplifier. The maximum DC drain voltages are related with maximum output power if the choke inductor in the amplifier is used. Therefore, a need to improve the amplifier performance of piezoelectric transducers exists for mobile ultrasound applications. In this study, a post-voltage-boost circuit-supported class-B amplifier used for mobile ultrasound applications was developed to increase the acoustic performance of piezoelectric transducers. The measured voltage of the post-voltage-boost circuit-supported class-B amplifier (62 VP-P) is higher than that of only a class-B amplifier (50 VP-P) at 15 MHz and 100 mVP-P input. By performing the pulse-echo measurement test, the echo signal with the post-voltage-boost circuit-supported class-B amplifier (10.39 mVP-P) was also noted to be higher than that with only a class-B amplifier (6.15 mVP-P). Therefore, this designed post-voltage-boost circuit can help improve the acoustic amplitude of piezoelectric transducers used for mobile ultrasound applications.

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Computation of Analytical Zoom Locus Using Padé Approximation

Cited by 12 publications

References 29 publications

Optical Design of a Novel Collimator System with a Variable Virtual-Object Distance for an Inspection Instrument of Mobile Phone Camera Optics

Optical Design of a Novel Collimator System with a Variable Virtual-Object Distance for an Inspection Instrument of Mobile Phone Camera Optics

Fisheye lens design for solar-powered mobile ultrasound devices

Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications

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