Hiromi Totani

PZT thin-film actuator driven micro optical scanning sensor by 3D integration of optical and mechanical devices

In this paper, a novel functional element integration method is proposed and demonstrated by highly miniaturized micro optical scanning sensor with dimensions of W2.0/spl times/L4.0/spl times/H2.8 mm/sup 3/. In the sensor as small as a wheat grain, the functional elements such as a laser diode (LD), photo detectors (PDs), a beam splitter, a ball lens, and a PZT thin-film actuator integrated optical scanner are integrated on separate substrates each consisting a functional module and the substrates are stacked. And the sensor is capable of multi-optical sensing: the 2D object shape recognition (+/- 10 degs scanning area for two direction) and the range measurement (50 mm +/- 10 mm with 0.5 mm resolution).

Sputtered high |d/sub 31/| coefficient PZT thin film for microactuators

High |d/sub 31/| coefficient PZT thin film for Si-based microactuators has been developed. Piezoelectric coefficient d/sub 31/ of around -100 pC/N was obtained and it is comparable to that of thick film or bulk PZT. The film was deposited on Pt/Ti/LTO/Si substrate by magnetron sputtering and annealed for obtaining perovskite structure. It was made clear that a <111> strongly oriented film has a higher |d/sub 31/| coefficient. Crystal orientation preference was controlled by ramp rate at post anneal process. Built-in stress and Youngs modulus of PZT thin film have also been evaluated. It was shown that post anneal process significantly increases both mechanical characteristics. 10 minutes-annealed PZT thin film which has d/sub 31/ of -100 pC/N has a built-in stress of 380 MPa and a Youngs modulus of 75 GPa.

Two-dimensional miniature optical-scanning sensor with silicon micromachined scanning mirror

For achieving higher performance and for miniaturizing the size of an optical scanning sensor, raising the scanning angle response, increasing the accuracy of detection of the scanning location independent from the environmental temperature, and miniaturizing an optical-scanning sensor were considered. And the silicon micromachined 2D optical scanner integrated with a piezoresistor for scanning location detection and a photodiode for optical intensity detection was newly designed and fabricated. The obtained results with the fabricated scanner are following. The scanner is capable of scanning a light beam more than 40 degrees 2D. The scanning angle sensitivities are 4.8 deg/V for horizontal direction and 10.5 deg/V for vertical direction. The scanning location detection sensitivity for each horizontal and vertical directions are 21 mV/deg and 26 mV/deg., respectively. The decrease of detection accuracy of scanning location has been reduced to less than 1 percent within +/- 10 degrees C temperature shift. And the photodetector has a photosensitivity of 0.33 A/W which allows the optical-scanning sensor to detect the reflected light intensity from an object which is 200 mm away from the sensor.

Miniature optical scanning range sensor utilizing a silicon micromachined scanner

This paper describes a miniature optical scanning range sensor based on a newly proposed detecting method using a Si micromachined optical scanner for detecting the range to a target plane. This sensor consists of the micro scanner, a light source and photodetector with a pinhole and features a higher resolution detection compared to the conventional method such as trigonometrical measurement using a Position Sensitive Detector (PSD). The sensor is capable of high resolution detection in the range 40 mm to 50 mm with an accuracy of less than 1 mm when the size of the sensor is 2 mm/spl times/4 mm. This sensor could be applied to the sensor for a micro maintenance robot.

Basic Characteristics Of A Piezoelectric Buckling Type Of Actuator

An actuator which utilizes buckling motion due to piezoelectric transverse stress is present. It will be a key part of Micro Focusing Device(MFD) which changes focal length of light from a light source. Sputtered PZT(Pb(Zr/sub x/ Ti/sub 1-x/)O3:x=0.54) was used as piezoelectric material and piezoelectric coefficient(d/sub 31/) of 45 pC/N was obtained. It was confirmed that the actuator can produce enough deflection for MFD application by non-linear elastic theory calculation with thin film mechanical characteristics and d/sub 31/ data.

Study on mechanical characteristics of PZT thin film for sensors and actuators

Piezoelectric thin films are very promising materials for MEMS applications because they have application flexibility and compatibility with semiconductor and micromachining processes. How to design MEMS devices with piezoelectric thin films, the mechanical characteristics, and how those characteristics can be controlled by process conditions is discussed in this paper. In addition, piezoelectric/electric characteristics must be understood. With this background, mechanical characteristics (Youngs modulus and built-in stress) measurements of sputtered Pb(Zrx, Ti1 - x) O3 thin film, one of piezoelectric materials, have been carried out using the load-deflection method. Relationships between post anneal conditions and those characteristics are discussed. It was shown from the experiment results that Youngs modulus increases as anneal temperature/time increases. The maximum value was 76.6 GPa(700 degrees C/3600 sec) which is more than three times larger than that of as-depo film. Built-in stress is also affected by post anneal process and ranges from 0.04 GPa(as-depo) to 0.41 GPa(700 degrees C/60 sec). SEM observation results made it clear that it was caused by film shrinkage due to grain enlargement during anneal process.

Miniature 3D optical scanning sensor for pipe-inspection robot

We have newly developed a miniature optical scanning sensor capable of 3D recognition for pipe-inspection. The sensor, the size of (phi) 23 - 18 mm, consists of a miniature 2D optical scanner integrated with photo detector and piezoresistor a laser diode with collimating lens and an amplifier circuit. The 2D optical scanner actuated by piezoelectric actuator was applied to the sensor for miniaturization of the scanning mechanism. In order to detect on surface in pipe 3D, circular scanning pattern with variable scanning range, such as spiral pattern, was adopted. Reflected beam intensity from surface in pipe at each scanning position is detected by the photo detector. When scratches or obstructions exist on surface in pipe, the detected signal is changed. Shape recognition of the surface in pipe can be realized by detecting the change signals and its each scanning position information. In the case, piezoresistor fabricated on the torsional spring of the scanner was applied for detection of scanning position. Sensing range of 100 to 200 mm and resolution of less than 1 mm was obtained in 1 inch diameter pipe. This sensor could be useful for recognition sensors of miniature mobile robot in many inspection fields.

Optical characteristics of PZT thin film actuator-driven micro-optical scanning sensor with multilayer stacked device structure

We developed a micro optical scanning sensor with the dimension of 2.0 mm X 4.0 mm X 3.0 mm for a micro inspection robot. In this sensor, the functional elements such as a laser diode (light source), photo diodes, pin-holes, a beam splitter, a ball lens, and a PZT thin film actuator driven micro optical scanner are integrated on separate substrates each consisting a functional modules and the substrates are stacked. Performance of the optical sensor depends on its optical characteristics. This sensor has spot size of output beam is 256 micrometer X 580 micrometer at 60 mm from the sensor, output power is 0.5 mW, optical scanning angles are plus or minus 10 deg. two-dimensionally, and detecting sensitivity of photo diodes are 0.3 A/W. The sensor is capable of distance measurement between the sensor and an object at 50 mm plus or minus 10 mm and the object shape recognition two-dimensionally based on the optical scanning method. By using these functions, the sensor can measure dimensions of the object and measuring resolution is less than 0.5 mm.