New 3D scanning system

Confocal microscopy has been widely used for measurement of tiny objects and got the following distinct advantages:

1) The surface condition of the scanned object is not critical; no matter whether it is shiny, matted, tilted, or even a combination of them.

2) It is possible to reach to holes in depth.

3) When scanning with the conventional triangulation method, a second scanning at reverse side is necessary for some objects. Confocal scanning can eliminate this.

However, using such method for measurement of comparatively larger objects is seldom found due to hardware limitations. Utilizing the latest technology development, the patent pending "New 3D Scanning System" can measure 3D objects of small to medium size (say from 1-10mm variation in height), with a speed that can match the fastest triangulation scanning method, and pocesses all the benefits of confocal scanning method.

The illustrated diagram fig.2 at next page explains how the new system works for a single line of object profile.

As seen from the diagram, there are few critical areas that need to be mentioned:

1) The inlet laser line curtain is an oscillating laser curtain by means of reflection from an oscillating mirror attached to a motor and encoder, where the oscillating angle is recorded and input to computer, as explained by the diagram shown in fig.1 below. The oscillating angle of the laser curtain finally reflected to the depth scanning on the object as explained in fig.2.

2) A super high speed line scan camera is used to capture the reflected image projection on the object, and finally send data to computer related to the encoder position.

Fig. 2 Optical Part of the Structured Laser Scanning System

Figure 3 explains the intersection of the laser curtain and the viewing plane of the linescan camera, for ease of understanding, only one side of the laser curtain is shown.
As the laser curtain is oscillating, the intersection of this laser plane and the camera viewing plane moves up and down. Now we assume the intersection is moving from top to bottom, initally, the camera sees nothing since the intersection does not fall onto the object. As the intersection moves further down, in one instant it falls on the object as shown in the diagram. As the intersection moves further down, other area of the object is reflected and all laser movements are captured by the camera.

Figure 3 Intersection of planes falls onto object

By intergrating the captured lines, an image as shown in fig. 4 is formed.

Figure 4 Integrated Image

This captured image shows only one line of the object profile. In oredr to get the 3D profile of the scanned object, we have to move the object by steps in the direction perpendicular to the camera viewing plane and capture the object profile in various steps, then combine these object profile lines to form the 3D image.

Figure 5

In fig5, a 3D captured Hong Kong five dollar coin is shown, please note that all reflections are eliminated, unlike triangulation method, which may need to spray black non reflective paint onto the coin surface.

The figure 6 below is the same coin image with enlarged height to highlight the captured details. Again, the reflection poperties of the coin surfact has no adverse effect on the image capturing.