Design of Wide Angle and Large Aperture Optical System with Inner Focus for Compact System Camera Applications

Choi, Hojong; Ryu, Jae Myung

doi:10.3390/app10010179

Cited by 14 publications

(9 citation statements)

References 15 publications

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“…Equation (3) shows the equation of the THD of the limiters [40]. Low THD values indicates that the limiters have low signals distortions [36,[46][47][48][49]. Compared to the THD of the resistor-diode limiter (0.31%), the dual-resistor-diode limiters have slightly lower THDs (0.29 and 0.28%)…”

Section: Resultsmentioning

confidence: 99%

Novel dual-resistor-diode limiter circuit structures for high-voltage reliable ultrasound receiver systems

Choi¹

2022

THC

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BACKGROUND: The limiters have been used to protect the ultrasound receivers because of the inherent characteristic of the transducers which are required to use the high voltage excitation to obtain the reasonable echo signal amplitudes. OBJECTIVE: Among the variety of the limiters, the performances of discharge voltage degradation from the limiters gradually deteriorate the whole ultrasound systems according to the applied voltages of the ultrasonic transducers. This could cause the ultrasound systems to be unreliable for the long-term operations, resulting in possibly breaking the receiver systems. METHODS: Designed limiters were evaluated with insertion loss, total harmonic distortion, and pulse-echo responses with the ultrasound transducer devices. RESULTS: Designed new dual-resistor-diode limiters exhibited greater and faster suppression of the pulse width (1.15 V and 6.1 μs) for high-voltage signals. CONCLUSIONS: Our proposed dual-resistor-diode limiter could be one of the potential candidates for reliable ultrasound receiver system.

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Section: Resultsmentioning

confidence: 99%

Novel dual-resistor-diode limiter circuit structures for high-voltage reliable ultrasound receiver systems

Choi¹

2022

THC

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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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“…Figure 12e,f shows the pulse widths of the echo signals. The pulse width is related to the axial resolution of the ultrasonic systems [56][57][58]. The pulse width of the echo signal when using the class-S power amplifier (640 ns) is shorter than that when using the class-A power amplifier (670 ns) at 20 MHz.…”

Section: Pulse-echo Analysismentioning

confidence: 99%

Wide Bandwidth Class-S Power Amplifiers for Ultrasonic Devices

You

Choi

2020

Sensors

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Wide bandwidth ultrasonic devices are a necessity in high-resolution ultrasonic systems. Therefore, constant output voltages need to be produced across the wide bandwidths of a power amplifier. We present the first design of a wide bandwidth class-S power amplifier for ultrasonic devices. The −6 dB bandwidth of the developed class-S power amplifier was measured at 125.07% at 20 MHz, thus, offering a wide bandwidth for ultrasonic devices. Pulse-echo measurement is a performance measurement method used to evaluate the performance of ultrasonic transducers, components, or systems. The pulse-echo signals were obtained using an ultrasonic transducer with designed power amplifiers. In the pulse-echo measurements, time and frequency analyses were conducted to evaluate the bandwidth flatness of the power amplifiers. The frequency range of the ultrasonic transducer was measured and compared when using the developed class-S and commercial class-A power amplifiers with the same output voltages. The class-S power amplifiers had a relatively flat bandwidth (109.7 mV at 17 MHz, 112.0 mV at 20 MHz, and 109.5 mV at 23 MHz). When the commercial class-A power amplifier was evaluated under the same conditions, an uneven bandwidth was recorded (110.6 mV at 17 MHz, 111.5 mV at 20 MHz, and 85.0 mV at 23 MHz). Thus, we demonstrated that the designed class-S power amplifiers could prove useful for ultrasonic devices with a wide frequency range.

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Design of Wide Angle and Large Aperture Optical System with Inner Focus for Compact System Camera Applications

Cited by 14 publications

References 15 publications

Novel dual-resistor-diode limiter circuit structures for high-voltage reliable ultrasound receiver systems

Novel dual-resistor-diode limiter circuit structures for high-voltage reliable ultrasound receiver systems

Fisheye lens design for solar-powered mobile ultrasound devices

Wide Bandwidth Class-S Power Amplifiers for Ultrasonic Devices

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