图像信息原理_电荷耦合器件_v2.ppt

On-Chip Amplifier 1. OD OS RD R SW Output Node Output Transistor Reset Transistor Summing Well +5V 0V -5V +10V 0V R SW --end of serial register Vout Vout The on-chip amplifier measures each charge packet as it pops out the end of the serial register. The measurement process begins with a reset of the ‘reset node’. This removes the charge remaining from the previous pixel. The reset node is in fact a tiny capacitance ( 0.1pF) RD and OD are held at constant voltages (The graphs above show the signal waveforms) Eventually all the buckets have been measured, the CCD has been read out. Structure of a CCD 1. The image area of the CCD is positioned at the focal plane of the telescope. An image then builds up that consists of a pattern of electric charge. At the end of the exposure this pattern is then transferred, pixel at a time, by way of the serial register to the on-chip amplifier. Electrical connections are made to the outside world via a series of bond pads and thin gold wires positioned around the chip periphery. Connection pins Gold bond wires Bond pads Silicon chip Metal,ceramic or plastic package Image area Serial register On-chip amplifier Structure of a CCD 2. CCDs are are manufactured on silicon wafers using the same photo-lithographic techniques used to manufacture computer chips. Scientific CCDs are very big ,only a few can be fitted onto a wafer. This is one reason that they are so costly. The photo below shows a silicon wafer with three large CCDs and assorted smaller devices. A CCD has been produced by Philips that fills an entire 6 inch wafer! It is the worlds largest integrated circuit. Don Groom LBNL Structure of a CCD 3. One pixel Channel stops to define the columns of the image Transparent horizontal electrodes to define the pixels vertically. Also used to transfer the charge during readout Plan View Cross section The diagram shows a small section (a few pixels) of the image area of a CCD. This patte