Optical Tilt Sensor Research Articles

Development of Fiber Bragg Grating-Based Temperature Insensitive Novel All Optical Tilt Sensor

Development of Fiber Bragg Grating-Based Temperature Insensitive Novel All Optical Tilt Sensor

Temperature-insensitive optical tilt sensor based on a single eccentric-core fiber Bragg grating.

This Letter presents a simple temperature-insensitive optical tilt sensor based on a single eccentric-core fiber Bragg grating (ECFBG). By partly inserting an ECFBG into a ceramic ferrule, the reflection spectrum of the ECFBG splits into two peaks as a result of the applied tilt angle. The magnitude and direction of inclination in one dimension can be determined by monitoring the wavelength separation between both peaks, which is inherently insensitive to temperature. The proposed tilt sensor has a good linear response within a wide dynamic range of ±45°, with a sensitivity of 0.012nm/°, with a resolution of 0.83°, and with an accuracy of 0.41°. Being free from any inherent mechanical joint/friction, along with the advantages of a compact structure, good repeatability, and low cost, the proposed sensor is highly suitable for practical engineering applications.

A liquid pendulum based optical tilt sensor

In this paper a simple, low-cost single axis optical tilt sensor is presented. The presented sensor body is a transparent, cube shaped container made of an acrylic sheet. Additionally, it is half filled with liquid (i.e. water) based on its inner volume. In order to sense the liquid column inclination during the tilting of the sensor body, two pairs of optical trans-receiver have been used and their unique orientation across the sensor body claims relatively high measuring range. The basic working principle of the sensor depends on Snell’s law of refraction and reflection. Experimentally, it is observed that the developed prototype is able to sense the tilt angle in the range of ±90°, but a significant linear range is found in ±20°. In this range, the sensor has a resolution of 0.02° and sensitivity of 225mV/°.

Micro-grating tilt sensor with self-calibration and direct intensity modulation

A micro-grating tilt sensor based on phase diffraction grating with self-calibration capability and direct intensity modulation is proposed. The optical tilt sensor consists of a coherent light source, gold gratings patterned on the transparent substrate, a silicon proof mass supported by the eight symmetrical Al cantilevers. Al membrane is sputtered on the bottom of the proof mass. Both Au and Al membrane serve as electrodes for electrostatic actuation. This can provide the sensitivity adjustment and self-calibration capabilities. Experiments show that the inclinometer provides the maximum incline sensitivity of 90mV/°, resolution of 0.00006°, a measurement range of±5° in the rotational plane that is parallel to the direction of the gravity, and good self-calibration ability with electrostatic actuation.

Optical tilt sensor with direct intensity-modulated scheme

An optical tilt sensor based on a phase-sensitive diffraction grating with direct intensity-modulated scheme is proposed in this paper. The tilt sensor consists of a coherent light source, an integrated grating, a mechanical sensing part, and an optical signal processing circuit. The mechanical sensing part consists of a bulk proof mass and two cantilevers that can be fabricated with a two-mask process on a silicon-on-insulator substrate. A phase-sensitive diffraction grating, which was formed with the integrated grating and the upper surface of the proof mass, acts as the sensing element for the tilt measurement. Experimental results show this tilt sensor provides the optimal tilt sensitivity of 1.15 V/° and resolution of about 0.0046°, and a measurement range of ±20° in a rotational plane that is perpendicular to the direction of the earth's gravity.

Development and investigation of an optical tilt sensor

An optical tilt sensor was developed and its performance was investigated. The tilt sensor set-up consisted of a laser light source, lenses and an image sensor. A precision reference tilt sensor was also installed on the same stage, and the measurement results of tilt angles using the optical and reference tilt sensors were correlated. The correlation coefficient (R-value) obtained under ideal conditions was 0.99454, indicating that the optical tilt sensor could produce as accurate measurements as the precision reference tilt sensor. The R-value decreased to 0.97714 and 0.93209 when the image sensor was shifted backwards and forwards from the focal plane by 1mm, respectively. The R-value decreased to 0.96840 when the tilt sensor was performed with the room light turned on. There were not significant differences in the measurement results obtained with air conditioners turned on and off, indicating that the optical tilt sensor was robust and was not sensitive to the surrounding air turbulence. These findings are useful for the final design of the optical tilt sensor.