62 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 100 - 90- 80- 70- 60- 50- 30- 20- 10- I HC- RED 3 I HN- CH2-CH2-OH NH z 250 280 /90 I I ! 220 •10 /.00 500 600 •/AVE LENGTH in nm Figure 1. Absorbance spectrum of the direct dye HC-RED 3. dyestuff distribution of the cross section is visible. The embedding resin is transparent, resulting in a 100% transmission value. MICROSCOPE SPECTROPHOTOMETER SYSTEM The new Universal Microscope Scanning/Spectral Photometer (UMSP) from Carl Zeiss,

DYE DISTRIBUTION IN HAIR CROSS SECTIONS 63 Oberkochen, was used for the investigation. It is equipped with two monochromators allowing via special optics measurements in the spectral range from UV (240 nm) to IR (2100 nm). The motor-driven and computer-controlled scanning table has a resolution of 0.25 •m. It can be controlled by a joystick with display of x,y-coordinates. In Figure 2 the UMSP System with a monochromator on the illumination side (measurement of transmission) and on the imaging side is shown. The schematic diagram (Figure 3) shows the position of the essential components. This set-up is designed for UV-transmittance measurement and for fluorescence emission spectra recording with fixed wavelength excitation. Light from the monochromator (MONO I) for measurement or from the tungsten light source for general observation is focused via the hinged mirror (M 1) by the condensor onto the sample being positioned on the scanning stage. The image is projected into the plane of the measuring dia- phragm (MF) and from there back for observation or TV/photo-documentation. Light passing through the field diaphragm (MF) can either be detected directly or via the second monochromator (MONO II) by the photomultiplier (PMT). Fluorescence spectra are measured by inserting a dichroic mirror into the epi-condensor and by se- lecting the appropriate excitation filter. Automatic control of the amplifier, the mono- chromators, the scanning stage, the light shutters (SH), and the luminous field stop (LF) is done by a single electronic unit connected to the computer via a standardized IEC interface. The computer used with our system is an HP 9816 (floppy disc HP 9121). The soft- ware available is comprised of a package for complete spectra evaluation including han- -/. •,. -, • .-- • . : , ... Figure 2. Universal microscope scanning/spectral photometer (U•SP g0), •arl Zeiss, Oberkochen.