The oscillating lens of the scanner determines precise thread position and thread density in a textile fabric. High power reflex light LEDs illuminate the fabric.
The oscillating lens of the scanner determines precise thread position and thread density in a textile fabric. The illumination for incident light is located in the lens housing. The opposite headlight provides transmitted light.
Scanning principle by light-dark modulation using Fast Fourier Transformation
Optoelectronic scanning according to the modulation principle
A photocell behind an oscillating lens registers the light-dark modulations generated by the weft position of the textile web passing by. Depending on requirements, the fabric is illuminated by incident light (reflected light) or transmitted light.
- Highest possible angular resolution through optimized optics
- Determines the distortion of the weft yarn contactless and continuously
- Up to 200 threads/cm possible
- Fixed focus (no product-specific adjustment necessary)
- Precise and continuous detection of fabric distortion
- Wide scanning spectrum
- Scanning on both sides possible
A number of scanners and lamps are spaced evenly across the product web. The product runs between scanner and lamp. The structure of the passing weft threads and courses modulates the light intensity measured by the scanners. The structures repeat regularly creating bright-dark patterns. These patterns generate a modulated signal in the scanner’s receiver system.
A centrally-pivoted, cylindrical lens in the scanner oscillates to a specific angle in relation to the desired direction of the weft thread. When the lens is parallel with the weft thread, signal modulation is at its maximum. It then decreases as the oscillating lens progressively cuts across the weft line.
Interfering signals not agreeing with the frequency of weft threads, courses or rows of tufting are filtered digitally. Only signals relevant to distortion are analysed and the web distortion is calculated automatically and precisely from this.
By using a lamp with infrared LEDs, the light shining onto each scanner can be controlled automatically and individually. The lamps have a longer working life and consume far less energy; two further attributes of the LED technology.
If textiles barely allow light to shine through them, or their surface texture has distinguishable characteristics, better results can be obtained using reflected light rather than transmitted light. The scanners are therefore equipped with integrated infrared sided light with automatic intensity control. It can be activated instead of the lamps for transmitted light.