ENERGY a proposal for a Multi-channel Cmos Camera F. Pedichini, A. Di Paola, R. Speziali INAF Oss. Astr. Roma h e-

What is multi-channel imaging? The most standard duty of an astronomer simply : Multi Band Photometry How to do it?

The 3 most used technologies: 1- an old, but good, FILTER WHEEL + 1 CCD imager All of these items deserve a... deep comparative analisys ! 2- a MOSAIC FILTERED CCD imager 3- a DICROICH focal plane splitter + several CCD imagers

an old, but good, FILTER WHEEL + 1 CCD imager Has been used since the first digital imager, with great results, low cost, simple mechanics, user selectable bands and thx. to modern CCDs also a very good Q.E but different bands are exposed and acquired at different times due to detector readout time and filters set up time Imager

a MOSAIC FILTERED CCD imager widely used in low cost tv cameras, digital photography apparatus and amateur astronomy color imagers with all the bands taken during the same exposure.....but..... no user selectable bands, low Q.E. (quite impossible to be used with back illuminated detectors) and the bad MOIRE effect RGBRGB.... matrix filter

the MOIRE effect... the color of each pixel is function of the signals of the nearest ones producing nice on sharp edges....! astronomers dont’LIKE!

a DICROICH focal plane splitter + several CCD imagers sometime used in astronomy with the best Q.E. and time sincronicity in each channel.... but.... complex, expensive and polarization & f# sensitive Imager

polarization & f# sensitive dicroichs are made up by dielectric layers and partially polarize the reflected and transmitted beams best performances about field uniformity need collimated beams so a collimator and several camera optics must be added in the imager optical train often the weight and size of a “dicroich” imager make it impossible to fit some telescope focal planes as in the case of Schmidts or fast prime foci and now we go to a comparative table...

comparative table is the world of C-MOS helping us with a fourth chance?

in this detector each pixel outputs R,G and B signals with all the nice features of a CMOS “on chip camera” about 10Mpix in three layers low power on chip 12bit ADC windowing and binning 4 f.p.s. less than 30e- RON

foveon phisycs:on silicon “dicroich” red photons are deep penetrating the silicon green photons make photoelectrons midway blue photons interact early.....

foveon bands: bands are not user selectable how do they compare to Johnson filters what can we do with them in astronomy?

Black Bodies simulations: BB spectra from 2000 to K convolved with BVR Jhonson and BVR Foveon converted to magnitudes

reduction to Johnson.... it is possible using instr. color index Vf-Rf or Bf-Vf and a second order polinomya. error is 0.01 mag. V-Vf = (Vf-Rf)^ (Vf-Rf)

Energy camera: Uses Foveon M10 x3 CMOS 2200 x 1500, 9 micron pixels 3 bands, 4fps about 25 arcmin 12 m focal lenght 0.15 arcsec/pixel 30 e-RON 0.25 seconds read out time no shutter needed

LBC comparison on a mag 14 star: CCD: exp sec QE 90% 2e/adu RON 5 e- Energy: exp sec QE 30% 5e/adu RON 30 e- Time for 3 bands: exp. 3x0.013 sec filter 3x1 sec readout 3x1sec total ~3 sec Time for 3 bands: exp. 1x0.04 sec filter 0 sec readout 1x0.25sec total ~0.3 sec Target: star field BVR fast photometry at S/N = 100 to detect light transients SKY 1”seeing ~21mag/arcesc^2 Telescope: Mirror 8.2m. 1.4F# (prime focus camera) Both cameras: 9 micron pixels about 4Mpixel

LBC comparison on S/N 100: Mag CCD exp Energy exp 3.9Hz 3.5Hz 2Hz 0.5Hz 2.9Hz 1.1Hz

60/90/180 Schmidt: On a smaller telescope at the resolution of 1”/pixel the field is 1180 arcmin^2. Energy becomes a: multiband GRB Hunter on raw satellite triggers Mag Hz S/N=100 S/N=10

2 nd comparative table....

open discussions: 1) Is it useful in astronomy? 2) Can Foveon modify the shape of the bands? 3) Will we have more than 3 on-chip bands in the future? 4) Can Foveon technology used on back ill. detectors? 5) Can Foveon technology join CCDs?

the end..... Energy is a Multi channel camera or... Mc 2