Micro Molded Part Metrology Standards for Receiving Acceptance Inspections
Establishing rigorous non-contact metrology standards and ISO 14253-1 guardbanding protocols prevents defective micro-molded parts from entering production.
Optical Subsurface Bleed
Meaning
Imaging artifacts in translucent materials occur when light penetrates the surface and scatters before returning to the sensor. The presence of optical subsurface bleed can cause significant errors in vision-based metrology systems by blurring the edges of a part. This effect is common in white or light-colored plastics, ceramics and some biological materials.
Designers must account for this light behavior when selecting inspection methods for parts with high translucency.
Photon Scattering
Light that enters a material bounces off internal structures or pigments before it exits. In cases of optical subsurface bleed, the light appears to come from a wider area than the original point of impact. This creates a halo effect that hides the true physical boundary of the part from the camera.
Profile Distortion
Measuring the width of a translucent rib or the diameter of a hole becomes difficult when the edges are not sharply defined. Optical subsurface bleed makes features look larger or smaller than they actually are, depending on the lighting setup. Using polarized light or specific wavelengths can sometimes reduce the impact of this scattering on the measurement.
Surface Contrast
Successful machine vision relies on a clear difference between the part and its background. Because optical subsurface bleed softens the contrast at the edges, it can lead to false rejections or missed defects during automated inspection. Switching to tactile measurement or laser profiling is often necessary when material translucency is too high for standard cameras.