EN 60856:1993/A1:1993

Overview

EN 60856:1993/A1:1993 (also published as IEC 60856 Amendment 1) updates the specification for pre-recorded optical reflective videodisk systems - the "Laser vision" 50 Hz / 625 lines PAL format. The amendment adds a formal specification for the push-pull radial differential (RD) tracking signal, describing signal definition, measurement conditions, pickup requirements and performance limits for manufacturing and test of reflective videodisks.

Key topics and technical requirements

• Push-pull radial differential (RD) signal
  • Defined as the difference between optical powers diffracted into the two halves (opposite sides of the track) of the objective lens aperture. A slightly off-track scanning spot produces an asymmetrical radial diffraction pattern; the RD error signal has a characteristic zero-crossing at correct radial position (see standard figures).
• Measuring pick-up requirements
  • Wavelength: 780 ± 10 nm
  • Polarization: circularly polarized light
  • Numerical aperture: 0.50 ± 0.01
  • Pupil intensity: > 50% of maximum at rim of objective lens pupil
  • Optical performance: diffraction-limited within the Marechal criterion
• Measurement and filtering
  • Time constant: t = 1.8 ps
  • Filtering: low-pass
• RD signal magnitude & stability
  • Magnitude defined as (P1 − P2) / P3 at 0.1 pm radial offset
  • Specified magnitude range: 0.04 – 0.11
  • Within-one-revolution variation: < ±15%
• Noise and tracking error
  • Noise measured on residual error signal with RD tracking in closed-loop, band 2.2 kHz–100 kHz, radial servo bandwidth 1.5 kHz
  • Tracking error requirement: ≤ 0.03 pm (r.m.s.)

Applications and users

This amendment is relevant to organizations involved in design, manufacture, test and quality control of pre-recorded optical reflective videodisks (Laser Vision) and associated playback/measurement equipment. Typical users include:

• Optical disk manufacturers and process engineers
• Video-disk playback system designers and test labs
• Equipment vendors producing optical pick-ups and servos
• Standards and compliance teams verifying PAL-format videodisk conformance

Related standards

• IEC 60856 (original publication) - base Laser Vision specification
• EN 60856:1993 - European adoption of IEC 60856
• This document: EN 60856:1993/A1:1993 (Amendment 1 aligning with IEC 60856:1986/A1:1991)

Keywords: pre-recorded optical reflective videodisk, Laser vision, push-pull radial differential signal, RD signal, 50 Hz 625 lines PAL, optical pick-up, numerical aperture, tracking error, videodisk measurement.