Basic Concepts
This chapter introduces the basic concepts involved in Mech-MSR, including coordinate systems, surface data, and 2D images.
Coordinate Systems
Mech-MSR uses the following two coordinate systems.
- Surface data coordinate system
-
The coordinate system used by a Mech-Eye 3D Laser Profiler during data acquisition. It is also the unified coordinate system used by Mech-MSR to process measurement data.
-
X-axis: Parallel to the laser line, that is, along the width direction of the profile.
-
Y-axis: Points from the laser emitter toward the receiver unit, generally along the object scanning direction in which profiles are stitched.
-
Z-axis: Along the height direction, with the positive direction pointing toward the camera.
The line or plane at Z = 0 corresponds to the reference distance position of the Mech-Eye 3D Laser Profiler. The Z value is positive when the object surface is above the reference distance, toward the camera, and negative when it is below the reference distance, away from the camera.
-
- Camera coordinate system
-
The coordinate system used by a Mech-Eye Industrial 3D Camera during data acquisition. It describes the position and orientation of objects in the camera field of view relative to the camera.
-
X-axis: Parallel to the imaging plane in the horizontal direction.
-
Y-axis: Parallel to the imaging plane in the vertical direction.
-
Z-axis: Coincides with the optical axis and is perpendicular to the imaging plane, with the positive direction pointing away from the camera.
The X-, Y-, and Z-axes form a right-handed coordinate system.
In Mech-MSR, data acquired by a structured-light 3D camera is converted to the surface data coordinate system before output.
-
Surface Data
Surface data is three-dimensional data containing spatial coordinate information. In Mech-MSR, it is generally presented as a depth map and an intensity image.
- Depth map
-
An image that records the height, or Z value, of each point on the target object’s surface. Its data format is
32FC1(32-bit floating-point, single-channel), and each pixel value represents the height of the corresponding point along the Z-axis. When saved as a PNG file, the8UC4format is used to prevent precision loss. - Intensity image
-
An image that represents the reflectivity of the target object’s surface. Its data format is
8UC1(8-bit unsigned integer, single-channel).
2D Images
A 2D image is an ordinary two-dimensional image that does not contain spatial coordinate information.
| Type | Description | Data Format |
|---|---|---|
Color image |
An image containing the red, green, and blue color channels |
|
Grayscale image |
A single-channel image containing only luminance information |
|
Binary image |
An image whose pixel values are only 0 (black) or 255 (white), generally obtained by thresholding a grayscale image |
|