Completion of the VIMOS-IFU
The largest Integral Field Unit to date
22 May 2000
The VIMOS (VIsible Multi-Object Spectrograph) Integral Field Unit (IFU) assembly has been successfully completed on May 22, 2000 at the Laboratoire d'Astrophysique de Marseille.
This unit will offer astronomers the capability to obtain 6400 spectra simultaneously of a contiguous area on the sky 54x54 arcsec², with a spatial sampling of 0.67 arcsec/fiber, or 27x27 arcsec² at 0.33 arcsec/fiber.
To build this unit has been a considerable technical challenge, requiring a research and development phase with the manufacturing of several prototypes before the final technical solution could be identified. Several complex optical elements are present: large array of 2 cylindrical set of micro-lenses producing 6400 square elements used at the input, long arrays of micro lenses used at the output of fibers, more than 20 km of high-quality fibers, 300mmx25mm prisms and field lens as one single element, complex Invar mask supports to insert the fibers into the beam of the spectrograph. The total end-to-end efficiency of the VIMOS-IFU is 70%. The IFU will be transferred this week to Observatoire de Haute-Provence, where it will be integrated into the instrument.
This unit is the largest of this kind made to date.
More details can be found in Priéto et al., 2000, SPIE, Vol. 4008, p.510.
| Fig. 1: VIMOS-IFU head with micro-lens array glued onto fiber head with 6400 fibers |
Figs. 2: The complete VIMOS-IFU assembled at LAS-Marseille. The 6400 fibers are split in 4
masks each with 1600 fibers.
 | Fig. 3: View inside one of the VIMOS-IFU masks: 4 lines of 400 fibers are visible. The fiber output is fed into the VIMOS spectrograph, and 6400 spectra are produced on the CCD detectors. |
First light with the VIMOS IFU
16 June 2000
Light illuminating the VIMOS (VIsible Multi-Object Spectrograph) Integral Field Unit (IFU) has been injected through the VIMOS spectrograph on June 16, 2000. Images of the fiber+micro lens lines have been recorded on the detectors. The image quality appears to be as predicted.
Figure 4 shows the 4 lines of fibers/micro-lenses recorded in one of the 4 VIMOS channels. Figure 5 shows a close up on one of the lines with images of the fibers.
| Fig. 4: image of the 4 fiber lines of the VIMOS IFU as recorded on the detector of one channel. Separations between each module of 80 fibers can be seen in each of the fiber lines made of 5 such modules. |
| Fig. 5: close up of fiber images on one of the fiber lines. Fiber cores are imaged on 4.5 pixels as expected. |