Yoon-Chang Park

A High-speed Digital Laser Grating Projection System for the Measurement of 3-dimensional Shapes

In the non-contact 3-dimensional (3D) shape measurements, the fringe pattern projection method based on the phase-shifting technique has been considered very effective for its high speed and accuracy. The digital fringe projector in particular has great flexibility in generating fringe patterns since the patterns can be controlled easily by the computer program. In this work, we have developed a high-speed digital laser grating projection system using a laser diode and a polygon mirror, and evaluated its performance. It has been demonstrated that all the optical measurements required to find out the profile of a 3D object could be carried out within 31 ms, which confirmed the validity of our 3D measurement system. The result implies the more important fact that the speed in 3D measurement can be enhanced remarkably since, in our novel system, there is no device like a LCD or DMD whose response time limits the measurement speed.

Ultra High-speed 3-dimensional Profilometry Using a Laser Grating Projection System

The grating projection method with phase-shifting technique is very useful in measuring the 3-dimensional (3D) shape with high accuracy and speed. In this work, we have developed an ultra high-speed digital laser grating projection system using a high-power laser diode and a highsensitivity CMOS camera. With our system, the optical measurement required to find out the profile of a 3D object could be carried out within 2.6 ms, which is a significant (~10 times) improvement compared with those of the previous studies.

Phase error compensation for three-dimensional shape measurement based on a phase-shifting method

Abstract In this paper, a prediction and compensation method for the error in the phase measured by using the proportionality between two wavelengths in the TW-PMP (Two-wavelength Phase Measuring Profilometry) is proposed and experimental results are shown to verify the usefulness of the proposed method. For sample object, firstly, a phase-shifting with a quite large number of steps is adopted in measurement, compared with the conventional phase-shifting method, secondly, a 3-3 step phase-shifting method is used to measure the same object which is applied to high-speed 3D shape measurement, and then, measured results from these two phase-shifting methods are compared to calculate measurement noises. From the experimental results applying the proposed compensation method to the measured beat phase and absolute phase, it has proven that noises are decreased by 90% and 17.2% for each case.Key Words : 3D Shape Measurement, Error Compensation, Phase Shifting Technique, Two-wavelength, Phase Measuring Profilometry, Phase Error

Phase-height relationship by plane analysis in 3D shape measurement using fringe pattern projector

In a three-dimensional(3-D) measurement system based on a digital light processing (DLP) projector and a camera, a height estimating function is proposed based on geometric analysis. The proposed 3-D shape measurement method is a hybrid method that combines the geometric parameter measuring method and the least squares method. This method uses the phase-to-height relationship for one line by plane analysis, and the related parameters are estimated using the least squares method. Sinusoidal fringe patterns of the projector are projected on the object, and the phase of the measuring point is calculated from the camera image. Then, the relationship between the phase by fringe patterns and the height of the measuring point is described as a parameter of the horizontal coordinate on the image plane. Thus, the 3-D shape of the object can be obtained. Our experiments show that the modeling errors for the given x-z plane are within ±0.1 mm. The model for the entire working space can be represented by several plane models because all the x-z plane models along the y-axis are nearly the same. Therefore, the proposed method can dramatically reduce the number of mapping functions needed for 3-D measurement.

A FPGA-based Development of Ultrasonic Level Meter for Measuring Oil Levels of Vehicle Transmissions

Abstract In this paper a ultrasonic level meter for accurately and simply measuring oil levels of vehicle transmission is developed and its effectiveness is shown by experiments. By using a FPGA, all digital signal processes for the oil level calculation is fulfilled, and the programming on a FPGA project IDE enables very short developing time. And besides, analog circuits including a transmit/receive switch, multi-stage active filters and an envelope detect circuit are designed to process low-level ultrasonic echo signal. Under experiments, the designed level meter has proven to have the accuracy of about within 1[mm] scale. Key Words : Ultrasonic, Oil Level Meter, Vehicle Transmission, FPGA(Field Programmable Gate Array) * Corresponding Author : Moon-Ho KangTel: +82-10-8837-5349 email: mhkang64@gmail.com접수일 12년 07월 27일 수정일 (1차 12년 08월 30일, 2차 12년 10월 30일) 게재확정일 12년 11월 08일 1. 서론 차량의 누유, 변속충격 및 변속성능 이상의 일차적인 원인이 변속기 오일레벨의 변동 및 오염도에 기인하므로 변속기의 적정한 오일레벨과 상태는 매우 중요하다. 이를 위해 변속기 출하시 조립 라인에서 변속기내에 적정한 량의 오일이 있는지를 검사하는데, 현재는 변속기의 중량을 측정하는 방식을 사용하고 있다. 이 경우, 변속기 부품(하우징, 케이스, 기어류 등)들의 중량차이가 큼에도 불구하고, 일률적으로 기준 중량을 설정하여 전체 중량에서 기준 중량을 차감하는 방법을 사용하기 때문에 정확하게 오일레벨을 측정하기가 어렵다. 본 논문에서는 종래의 자동차 변속기 오일레벨 측정방식을 개선하여 오일레벨을 정확하고 손쉽게 측정하여, 차량의 품질을 향상시키고 효율적인 A/S에 기여할 수 있는 초음파 오일레벨 측정기를 개발하고 실험을 통해 유용성을 보인다. 종래의 초음파를 통한 비파괴 측정 사례들을 분석하여[1-3] 초음파 프로브를 변속기 오일 케이스 하부에 부착함으로서 변속기에 어떠한 변형도 없이 정밀한 오일레벨 측정이 가능하고, 저렴하여 기존의 변속기 조립라인이나 A/S에 신속히 적용할 수 있는FPGA(Field Programmable Gate Array)를 기반으로 한 새로운 오일레벨 측정기를 개발하였다. FPGA로는 Xilinx 사의 XC3S200을 사용하여[4] 오일

Experimental Study on Performance Comparison of Air-Conditioner with PF Heat Exchanger

In the present study, the heat transfer characteristics of the fin-tube and PF heat exchangers and the performances of the air-conditioner are experimentally investigated. Also, Cooling Seasonal Performance Factor(CSPF) of the air-conditioner is evaluated. For the heat exchanger experiment, the heat transfer and pressure drop are obtained. For the air-conditioner experiment, the cooling capacity, input power and COP are obtained. The air-enthalpy calorimeter and the constant temperature water bath are used. As the inlet air velocity increases, the heat transfer rate and pressure drop of the heat exchanger increased. PF heat exchanger has smaller refrigerant weight and larger capacity and COP than the fin-tube heat exchanger. The performance of PF-2 heat exchanger with the squarer fin is more excellent than that of PF-1 heat exchanger with the triangler fin. Also, CSPF of the fm -tube and PF heat exchanger is evaluated.