Shape Measurement Basics     Accurately Scan A Thin Object

Thin Object Measurement: How to Accurately Scan and Register Both Sides of a Thin Object

The Range7 utilizes two primary methods for aligning scans: geometry based alignment (best-fit), and marker alignment. Thin object measurement presents a challenge for both alignment methods. Geometry based alignment relies on unique geometry in the overlapping areas of adjacent scans. Thin objects do not have enough unique data along the edges for accurate registration of scans taken on opposite sides. Even objects that seem to have enough edge surface area often do not have enough unique geometry for the registration process to produce the proper thickness of the object. Marker alignment requires at least three common targets to exist in adjacent scans. On a thin object, targets would need to be applied to the edges in order to acquire common targets on scans taken on opposite sides. Usually targets do not fit on the edge of a thin object. If they do fit, they end up all in a straight line, which does not work either. Targets need to be placed in triangular patterns for accurate registration to occur. The Range7 can provide high-quality, accurate scans of thin objects. This document details the necessary steps to achieve optimal results. The example project shows how to scan a phone faceplate.

Details of Project
Total Project Duration (from setup to merged model) 2 Hours 40 Minutes
Setup Time 25 Minutes
Scanning Time (includes trimming out table from scans) 1 Hour 33 Minutes
Global Registration Time 4 Minutes
Merge Time 19 Minutes
Miscellaneous Time 9 Minutes
Cleanup Time (smoothing, trimming, hole fill, etc.) not performed
Number of Scans 38
Number of Poly-faces in Merged Model 8,086,434
Standard Deviation of Global Registration 8 microns

Thin Object Measurement Tools

The tele lens was used, because the object has very small features.

Scan Settings
Lens Tele
Standoff 466mm
Number of Passes 2
Exposure 25-65
Multi focus Enabled
Initial Registration Method Paired Points
Data Reduction Ratio 1/1

 

Object – Cordless Office Phone Faceplate

Phone Case Thin Object Measurement

Thin Object Measurement Tools

Tools Used

  • Range7 with Tripod
  • Needle-nose pliers or tweezers
  • Super glue
  • BBs – 0.177” [4.5mm] Diameter
  • Developer
  • Wood board 1”x4”x 8” (2)