ESO has a wide experience in the field of optical design, covering the wavelength range from UV to far infrared. Although most optical designs made for ESO instrumentation are not readily useable elsewhere, some ESO designs have been copied many fold for use at other observatories.

EFOSC (ESO Faint Object Spectrograph and Camera) was originally developed at ESO for the 3.6m telescope on La Silla. Since that time, some 15 copies of this design have been manufactured and put into service at other observatories around the world.

UVES (UV and Visual Echelle Spectrograph) was one of the first generation VLT instruments and was developed in-house at ESO. To date, about 10 additional copies of this design have since been produced for use at other observatories.

Apart from these specific examples, ESO has had a positive influence, through optical design proposals and design reviews, on the optical design of a very large number of instrumental developments in the ESO Member States over the last 30 years.

The control software developed by ESO for the VLT and its instruments has set new performance standards for large telescopes. Moreover, through the automisation of many of the processes that previously had to be carried out manually such as object acquisition, setting wind screens, finding guide stars, active optics correction, setting instrument parameters, etc, has also made the VLT the most efficient telescope of its class in the world. Many of the concepts developed for the VLT, such as observing templates and observation blocks, have been widely emulated elsewhere.

The VLT Common Control Software is currently distributed to some 26 external observatories and institutions. This has created pools of expertise within the ESO Member States that has allowed individual institutions to provide valuable contributions to the VLT observatory as well as other projects. The ideas and experience that accrued when developing the VLT CCS have also formed the basis for the ALMA Control Software.

With the advent of two-dimensional CCD image data and more powerful computers in the early 1980s, the IHAP interactive data reduction package was replaced by the ESO MIDAS system. MIDAS is conceptually similar to IHAP but is much more versatile and powerful. MIDAS is still in use today and is also included in SCISOFT package mentioned below. MIDAS is available to institutes and other users on the ESO web-site, and is currently downloaded about 400 times per year. Due to the availability of other similar packages and also commercial reduction software, its development today is essentially limited to VLT-related patches.

To support astronomers with data reduction in their home institutions, ESO has developed a software bundle known as SCISOFT. This is a unified collection of the major software packages for astronomical data-analysis packages currently in use today (including IRAF/STSDAS, MIDAS and IDL) as well as many smaller utilities.

In parallel to the VLT Control Software, the VLT Data Flow System was developed. This allowed, for the first time in a ground-based observatory, the complete end-to-end observing cycle to be condensed into a single homogeneous process. This process starts with the preparation of the observing programme, and continues through programme selection, observation simulation, programme execution (with or without the presence of the astronomer at the telescope), quality control, data archiving and finally the return of the calibrated data to the observer. Although at the outset it was difficult for many traditional astronomers to accept this revolutionary concept, it has today become a standard that has been copied by most of the world's major observatories.