“…The diaphragm is less sensitive than the narrow strip or the knife edge but has nearly the same sensitivity in all directions. A schlieren system using two lenses, a knife edge and a He-Ne laser light source was used by BARANENKO et al (1974) in their investigation of degassing and pool boiling of water, benzene, butyl and isobutyl alcohols at atmospheric pressure. The use of a laser light gives closely spaced fringes instead of a continuous illumination distribution obtained in an ordinary schlieren record.…”