N1 MULTISPECTRAL 3D SCANNER

Measurement principle

3D measurement​

The N1 measures the 3D coordinates by laser triangulation method. The 3D unit has a laser line generator projecting thin laser line on target. By measuring the laser line displacement on the 3D camera image, the N1 calculates the distance Z and the lateral coordinate X of the object along the laser line.

The laser triangulation method guarantees high precision of acquired 3D data and ease of integration into production lines.

Multispectral measurement

The multispectral unit measures near-normal reflectance of the target in visible (RGB) and NIR (730nm) spectral range. It has a high power LED flash unit, the collimating optics, the diffusor, and the multispectral camera. The LED light is shaped by the collimating optics and the diffusor into the narrow stripe pattern. The multispectral unit is aligned in a way that the projected light stripe overlaps the laser line. The reflected light intensity is measured by the multispectral camera. The multispectral camera takes images with LED flash ON and OFF for each color channel (R,G,B,NIR730). By substracting the reference images (LED flash OFF) from the signal images (flash ON), the effects of ambient light can be eliminated.

Data fusion

In order to calculate the RGB and NIR color coordinates, the corrected image intensities (R,G,B,NIR730) and the laser intensity (940nm) are assigned to the corresponding 3D points and normalized. The resulting point cloud has a format (X,Y,Z,R,G,B,NIR730,NIR940), where X,Y,Z are the point position in mm (float 32b) and color coordinates are 16 bit integers.

Measurement modes

The N1 supports FAST and HDR measurement modes. The FAST mode is designed for the applications where the highest scanning rate is required. It works best under moderate ambient light conditions (indoor, factory lighting, no strong reflections). The HDR (high dynamic range) mode should be applied at harsh ambient light conditions (direct sunlight) and when working with very inhomogeneous materials (high contrast, very reflective materials, glossy surfaces).

FAST mode

In FAST mode, one 3D camera image (laser ON) per profile is used. The background light in 3D image is subtracted by image processing algorithm. While delivering good results with low to moderate ambient light conditions, this method could potentially fail at strong ambient light, resulting in 3D noise and artifacts in the final point cloud. For multispectral measurements, one signal (flash ON) and one reference (flash OFF) image per each color channel are acquired. The exposure time is chosen to balance competing signal-to-noise and ambient light sensitivity considerations. The images can become overexposed when measuring glossy objects and/or under strong ambient light conditions.

HDR mode

In HDR mode, one signal and one reference 3D camera images per profile are used. The background light is removed by subtracting the reference from the signal image. Since the reference image is acquired directly, this methods provides the best possible background light rejection. For multispectral measurements, a sequence of two signal (flash ON) and two reference images (flash OFF) per each color channel is acquired. The images are taken at two different exposure settings. The shorter exposure time is chosen to prevent image overexposure at strong light conditions (highly reflective objects close to scanner, strong reflections, strong ambient light), while the images taken at longer exposure time provide excellent signal-to-noise ratio for darker areas. The best of the two background corrected images is taken for color calculation and normalized to its exposure time.

Setup

The N1 has powerful and easy to use tools for system parameterization, integration, test runs and troubleshooting:

  • Touchscreen: for easy initial setup of IP address, measurement mode, measurement range, exposure time, and synchronization mode. The changes can be applied on the fly without interrupting the measurement process. The 2D/3D visualization tool helps to setup the system correctly and identify the potential issues.
  • Web Interface: for full parameterization of the N1 including upload, logging and debugging of user applications.
  • REST API: for system integration.

On-board data processing

The N1 provides processing capacity and storage space for user applications. The user application controls the data acquisition process (START / STOP signals, profile synchronization, etc) via API. The user application has full access to DIOs and RS232 via API as well.

The user application can be uploaded to N1 via Web Interface.

The N1 provides a battery backup system that can buffer the input power interruptions without affecting the measurement process. When the power shortage sustains, the device leaves the measurement mode, sends the termination signal to the user application and shuts down the system (“graceful shutdown”). This reduces the risk of data lost and the risk of the system going into an uncontrolled state.

Interfaces

The N1 provides Gigabit Ethernet, RS232 and 4x high power digital in-/outputs for system integration.

The point cloud data can be stored on the device and retrieved via API, or sent out via GigE interface immediately for user side processing. Alternatively, the point cloud can be processed on the device by user application with an option to control the external actuators, PLCs or sensors via user programmable DIOs and/or RS232 interface directly.

Designed for conveyor systems

The N1 is designed for inline measurement of the parts moving on the conveyor. The measurement can be started by a photoelectric or proximity sensor, the measurement speed can be controlled by encoder. The measured 3D/ multispectral profiles can be processed directly on the integrated PC by user application. This reduces system complexity and costs!