The Oil Film Inspection Unit allows users to view and assess the application or leakage of oil-based fluids and lubricants. This technology can also estimate the thickness of the oil film using image data and statistical processing.
1. Technological Overview
Many petroleum-based oils such as mold release agents, lubricating oils, and cutting oils have the property of emitting fluorescence when exposed to ultraviolet rays.
Ultraviolet rays are emitted towards the surface of an object, and the fluorescence emitted by the oil-based liquid on object is detected by a camera. To isolate the florescence emitted by the oil agent wavelengths consistent with ambient light and ultraviolet light are removed.
No Filter
UV transmission filter
Filter Visible Light
Remove reflected light
Remove reflected light
Extract Fluorescent emission
Fig. 2 Fluorescence squeezing by two types of optical filters
Fluorescence
Reflected light
Ambient Light
Reflected UV light is removed through UV illumination and optical filters (Fig. 2). Ambient light is removed through comparison of the image with and without UV illumination (Fig. 3).
2. Estimating Film Thickness
The thickness of the oil film is estimated from the amount of fluorescence emitted from the camera image using the correlation equation that holds between the amount of fluorescence emitted from the oil film on the metal surface and the thickness of the oil film. This correlation formula needs to be obtained by statistically processing the film thickness actually measured using an optical interference type film thickness meter or the like and the fluorescence emission amount information obtained from the camera image for each type of oil in advance (Fig. 5).
Fig. 4 Correlation between film thickness and fluorescence emission detected by camera
Other than film thickness, several factors including distance, angle and angle affect the fluorescence emissions. These factors can be limited through standardizing the shooting conditions. Statistical correlation distance, tilt angle, position, and fluorescent emissions are tracked to allow estimation of oil thickness.
3. Uses of Oil Film Inspection Unit
The Oil Film, Inspection Unit can be used to inspect for oil residue on machine parts, leakage of engine oil, application of lubricants on molds, and more. A comparative image can also be generated to allow comparison of multiple results.
Example 1: Assessing application of Lubricants on Mold
Ideal Application
Thin
Thick
Example 2: Oil leak inspection
Inspection Results
Thin
Thick
Example 3: Lubricant
Inspection
Comparison
Lack
Excess
Example 4: Machined surface oil residue inspection
Fig. 1 Fluorescent emission of oil
Engine oil
Lubricant
Cutting Oil
Grease
UV Lighting ON
Oil film
Disturbed light
UV Lighting OFF
Difference
Fig. 3 Removal of ambient light with pulsed emission of UV lighting