One essential precondition of workflow analysis in minimally invasive surgery is a continuous data inflow in real time, in particular on the instruments in use. However, reliable identification systems are missing to date. We developed an automatic identification system which detects and registers the individual instrument during insertion into the trocar. The system is based on an opto-electronic object detection system using barcode 2/5 interleaved (printed out vs. lasered) which is detected by a micro endoscopic camera and light device. Evaluation was performed in vitro (laparoscopic training simulator) and in vivo (animal experiment) on 5 mm and 10 mm instruments with different insertion velocities into the trocar (20/10/1 cm/sec.). Furthermore, registration accuracy with a 1 - 5 sec. barcode retention period was evaluated. The best results were achieved with a 5 sec. static retention period of the barcode in the camera focus with a printed barcode. Retention periods of less than 5 sec. and dynamic insertions led to a significant decline of the detection rate. Opto-electronic barcode registration could be a promising technology for an automatic instrument registration. Although not yet mature for clinical application, the introduced system showed reliable results under static conditions.