CCD 181 Variable-Element High-Speed Linear Image Sensor FEATURES • • • • • • • • • • • • • 2592 x 1 photosite array µm photosites on 10µ µm pitch 10 µm x 10µ Anti-blooming and integration control Voltage-selectable array lengths: 2592 Elements 2048 elements 1728 elements 1024 elements Enhanced spectral response (particularly in the blue region) Excellent low-light-level performance Low dark signal High responsivity High speed operation Dynamic range typical: 7500:1 Over 1 V peak-to-peak outputs Dark references contained in sampled-andheld outputs Special selection available - consult factory Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 GENERAL DESCRIPTION intensity and the integration period. The output signal will vary in an analog manner from a thermally generated background level at zero illumination to a maximum at saturation under bright illumination. The CCD181 is a 2592-element line image sensor designed for industrial measurement, telecine, and document scanning applications which require high resolution, high sensitivity and high data rate. Incorporation of on-chip anti-blooming and integration controls allow the CCD181 to be extremely useful in an industrial measurement and control environment or in environments where lighting conditions are difficult to control. Two Transfer Gate — Gate structures adjacent to the row of image sensor elements. The charge packets accumulated in the photosites are transferred in parallel via the transfer gates (φX) to the transport shift registers whenever the transfer gate voltages go high. Alternate charge packets are transferred to the A and B transport registers. Two Analog Shift Registers — The transport shift registers are used to move the light generated charge packets delivered by the transfer gates. (φ1A, φ1B, φ2A, φ2B) serially to the charge detector/amplifier. The complementary phase relationship of the last elements of the two transport registers provides for alternate delivery of charge packets at the output amplifiers. The CCD181 is equipped with special gates which allow the user to select 4 effective array lengths: 2592 2048 1728 1024 elements: elements: elements: elements: 300-lines/inch 240-lines/inch 200-lines/inch 120-lines/inch across across across across 8.5 8.5 8.5 8.5 inch inch inch inch wide wide wide wide document document document document A Gated Charge Detector/Amplifier — Charge packets are transported to a precharge capacitor whose potential changes linearly in response to the quantity of the signal charge delivered. This potential is applied to the input gate of the two-stage NMOS amplifiers producing a signal at the output “VOUT” pin. Before each charge packet is sensed, a reset clock (φRA, φRB) recharges the input node capacitor to a fixed voltage (VRDA, VRDB) The CCD181 is a third generation device having an overall improved performance compared with first and second generation devices, including enhanced blue response and excellent low light level performance, and high-speed operation up to 20 MHz. The photoelement size is 10µm (0.39 mils) x 10µm (0.39 mils) on 10µm (0.39 mils) centers. The device is manufactured using Fairchild Imaging’s advanced charge-coupled device n-channel isoplanar buried-channel technology. Integration and Anti-Blooming Controls — In many applications the dynamic range in parts of the image is larger than the dynamic range of the CCD, which may cause more electrons to be generated in the photosite area than can be stored in the CCD shift register. This is particularly common in industrial inspection and satellite applications. The excess electrons generated by bright illumination tend to “bloom” or “spill over” to neighboring pixels along the shift register, thus “smearing” the information. This smearing can be eliminated using two methods: FUNCTIONAL DESCRIPTION The CCD191 consists of the following functional elements illustrated in the Block Diagram and Circuit Diagram (see Fig. 1A). Photosites — A row of 2592 image sensor elements separated by a diffused channel stop and covered by a silicon dioxide surface passivation layer. Image photons pass through the transparent silicon creating hole-electron pairs. The photon generated electrons are accumulated in the photosites. The amount of charge accumulated in each photosite is a linear function of the incident illumination Anti-Blooming Operation: A DC voltage applied to the integration control gate (approximately 5 to 7 volts) will cause excess charge generated in the photosites to be diverted to the anti-blooming sink (VSINK) instead of to the shift registers. This acts as a “clipping circuit” for the CCD output. (see Fig. 2) 2 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 Fig. 2 MAXIMUM OUTPUT VOLTAGE vs. φIC Voltage 3 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 Integration Control Operation: RMS Noise Equivalent Exposure — The exposure level that gives an output signal to the RMS noise level at the output in the dark. Variable integration times which are less than the CCD exposure time may be attained by supplying a clock to the integration control gate. Clocking φIC reduces the integration time from tEXPOSURE to tINT (Fig. 3). This reduces the photosite signal in all photosites by the ratio EXPOSURE to tINT. Greater than 10:1 reduction in average photosite signal can be achieved with integration control. Saturation Exposure — The minimum exposure level that will provide a saturation output signal. Exposure is equal to the light intensity times the photosites integration time. Charge Transfer Efficiency — Percentage of valid charge in- The integration-control and anti-blooming features can be implemented simultaneously. This is done by setting the φIC, clock-low level to approximately 5 to 7 volts. formation that is transferred between each successive stage of the transport registers. Responsivity — The output signal voltage per unit exposure for a DEFINITION OF TERMS specified spectral type of radiation. Responsivity equals output voltage divided by exposure. Charge-Coupled Device — A Charge-coupled device is a semiconductor device in which finite isolated charge-packets are transported from one position in the semiconductor to an adjacent position by sequential clocking of an array of gates. The charge-packets are minority carriers with respect to the semiconductor substrate. Total Photoresponse Non-uniformity — The difference of the Sample -and Hold Clock φSHA, φSHB) — The voltage waveform Dark Signal — The output signal in the dark caused by thermally applied to the sample-and-hold gates in the output amplifiers to create a continuous sampled video signal at the output. The sampleand-hold feature may be defeated by connecting φSHA and φSHB to VDD. generated electrons that is a linear function of the integration time and highly sensitive to temperature. response levels of the most and the least sensitive element under uniform illumination. Measurement of PRNU excludes first and last elements. Saturation Output Voltage — The maximum usable signal output voltage. Charge transfer efficiency decreases sharply when the saturation output voltage is exceeded. Dark Reference — Video output level generated from sensing elements covered with opaque metallization which provides a reference voltage equivalent to device operation in the dark. This permits use of external DC restoration circuitry. Integration Time — The time interval between the falling edge of Isolation Cell — This is a site on-chip producing an element in the Exposure Time - The time interval between the falling edge of the video output that serves as a buffer between valid video data and dark reference signals. The output from an isolation cell contains no valid information and should be ignored. two transfer pulses (φX) shown in the timing diagram. The exposure time is the time between transfers of signal charge from the photosites into the transport registers. any two successive transfer pulses (φX). The integration is the time allowed for the photosites to collect charge. Pixel - A picture element (photosite). Dynamic Range — The saturation exposure divided by the RMS temporal noise equivalent exposure. Dynamic range is sometimes defined in terms of peak-to-peak noise. To compare the two definitions a factor of four to six is generally appropriate in that peak-topeak noise is approximately equal to four to six times RMS noise. 4 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 5 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 6 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 7 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 8 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 9 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 10 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500 CCD181 DEVICE CARE AND OPERATION ORDER INFORMATION Glass may be cleaned by saturating a cotton swab in alcohol and lightly wiping the surface. Rinse off the alcohol with deionized water. Allow the glass to dry, preferably by blowing with filtered dry N2 or air. Order CCD181DC where “D” stands for a ceramic package and “C” for commercial temperature range. It is important to note in design and applications considerations that the devices are very sensitive to thermal conditions. The dark signal DC and low frequency components approximately double for every 5º C temperature increase and single-pixel dark signal nonuniformities approximately double for every 12º C temperature increase. The devices may be cooled to achieve very long integration times and very low light level capability. 11 Fairchild Imaging, Inc., 1801 McCarthy Blvd., Milpitas, CA 95035 • (800)325-6975 • (408) 433-2500