AutoSync with Laser in Stroboscopes

Operating Principle and Measurement Advantages

Observing rapidly rotating or periodically moving objects with a stroboscope is based on the principle of apparent motion freeze through synchronized light flashes. Accurate visualization requires an exact match between the stroboscope flash frequency and the actual motion frequency of the object. The AutoSync laser function performs this synchronization automatically and with high precision. 

Basic Principle of Laser Synchronization

In the AutoSync method, a laser beam is directed at a rotating object marked with a reflective marker. Each time the reflective marker passes the measurement point, part of the laser light is reflected back to the device. This reflected signal is detected and serves as a precise timing marker for one complete revolution or motion cycle. 

The stroboscope uses this signal directly as a trigger for the flash. This creates a closed control loop:

1. The laser continuously emits light.
2. The reflective marker reflects the beam once per revolution.
3. The receiver detects the reflected signal.
4. The signal directly triggers the flash.
5. The flash occurs synchronously with the actual motion.

Technical Challenge: Superposition of Laser Light and Flash

Implementing this principle in practice is challenging because the laser beam and the stroboscope flash appear within the same field of view. During the flash, the reflected laser signal may be temporarily overwhelmed by the flash intensity. A robust system must therefore:

• Reliably detect reflected signals even under intense flash illumination.
• Suppress interference from ambient light.
• Maintain stable signal evaluation across different surface properties. 

This is achieved through coordinated transmitter and receiver systems as well as appropriate signal processing

Automatic Frequency Adjustment

A key advantage of the AutoSync function is that no manual adjustment of the flash frequency is required. Synchronization is performed directly from the measured return signal.
In addition, the system can track dynamic speed changes. If the rotational speed varies, for example due to load changes or control processes, the flash frequency is continuously adjusted accordingly. 

Elimination of Harmonic Multiples

A well known phenomenon in conventional stroboscopy is the occurrence of so called harmonic multiples. In such cases, apparently stable images may be produced even when the flash frequency is an integer multiple or a fraction of the actual motion frequency. 

Example:

• Actual rotational speed: 1,000 rpm
• Apparently stable image at 500 rpm or 2,000 rpm 

These ambiguities can make correct interpretation considerably more difficult. 

Laser synchronization inherently eliminates this problem. The flash is triggered exclusively by the actual event, namely the passage of the reflective marker. As a result, the flash frequency corresponds exactly to the true motion frequency, and alternative stable conditions cannot occur. 

• Without AutoSync:
  • Multiple apparently stable frequencies are possible.
• With AutoSync:
  • Only one stable condition exists
  • Actual frequency = Flash frequency.

For an even more detailed explanation, see here.
 

Measurement Accuracy and Redundancy

Because synchronization is derived directly from the motion itself, very high timing accuracy is achieved. In addition, the signal processing can evaluate multiple consecutive reflection events, enabling:

• Detection of outliers.
• Stabilization of measured values.
• Improved overall reliability. 

This redundant evaluation increases measurement confidence, particularly in industrial applications with varying operating conditions. 

Summary

The AutoSync laser function provides an efficient and robust method for synchronizing stroboscope flashes. Through direct coupling to the reflected laser signal, it offers the following advantages:

• Automatic adjustment of the flash frequency.
• Unambiguous determination of the correct motion frequency.
• Elimination of errors caused by harmonic multiples.
• Dynamic adaptation to speed fluctuations. 

This makes the method particularly suitable for applications requiring fast, precise, and unambiguous visual analysis of moving objects and processes.