  The emission line survey within the Calar Alto Deep Imaging Survey (CADIS)
detects emission line galaxies by a scan with an imaging Fabry-Perot
interferometer. It covers 5 fields of > 100 square arcmin each in three
wavelengths windows centered on lambda ~ 700, 820, and 920nm, and reaches to a
typical limiting line flux of 3 x 10^(-20) W m^(-2). This is the deepest
emission line survey covering a field of several 100 square arcmin. Galaxies
between z = 0.25 and z = 1.4 are detected by prominent emission lines (from
Halpha to [OII]372.7) falling into the FP scans. Additional observations with a
dozen medium band filters allow to establish the line identification and thus
the redshift of the galaxies to better than sigma(z) =0.001. On the basis of a
total of more than 400 emission line galaxies detected in Halpha (92 galaxies),
[OIII]500.7 (124 galaxies), or [OII]372.7 (222 galaxies) we measure the
instantaneous star formation rate (SFR) in the range 0.24 < z < 1.21. With this
purely emission line selected sample we are able to reach much fainter emission
line galaxies than previous, continuum-selected samples. Thus completeness
corrections are much less important. Our results substantiates the indications
from previous studies (based on small galaxy samples) that the SFR decreases by
a factor of ~20 between z = 1.2 and today. In fact, for a Omega(m) = 0.3,
Omega(Lambda) = 0.7 cosmology, we find an exponential decline rho(SFR)
proportional to exp(-lookback_time) / 2.6Gyr). The inferred SF density is in
perfect agreement with that deduced from the FIR emission of optically selected
galaxies which is explained by a large overlap between both populations. We
show that self-consistent extinction corrections of both our emission lines and
the UV continua lead to consistent results for the SF density.
