Sony XCST70 Product Brochure (Glossary of Camera Technology) - Page 2

Electronic shutter: CCD camera operating mode where the integration time can be shortened without any mechanical device. Used for blur reduction when capturing fast moving objects, and for camera sensitivity reduction in high levels of scene illumination. Exwave HAD technology: Technology with a nearly gapless OCL (On-chip-lens) located over each pixel of the CCD resulting in more than twice the sensitivity and 1/50 the smear compared to Hyper HAD technology. F Stop, F Number: Calibrated measure of lens iris aperture. Common F stops are F1.4, F2, F2.8, F4, F5.6, F8, F11, F16, F22. The higher the number, the smaller the iris aperture and the less light falling on the imager. Field: Half of a TV picture consisting of only the odd or only the even lines. NTSC/EIA features 60 fields of 262.5 lines / second. PAL/CCIR features 50 fields of 312.5 lines / second. Odd / even field pairs recombine on screen as frames due to picture tube and human eye memory. Field / frame integration: Two different pixel readout techniques in CCDs designed for interlaced output. Refers to the total integration time, field duration (16.6 ms NTSC/EIA or 20 ms PAL/CCIR) or frame duration (33.3 ms NTSC/EIA or 40 ms PAL/CCIR). Both modes give the same sensitivity. In field integration, pixels of two adjacent lines are read out together as one. The full CCD is read every field, achieving higher picture refresh rate but lower vertical resolution. Mostly used in current applications to achieve optimum capture of movement. Adjacent lines are combined differently for odd (1+2, 3+4, . . .) and even field (2+3, 4+5, . . .) outputs. In frame integration, pixels are read out separately. The complete CCD is read after two fields. Full vertical resolution is achieved. Progressive scan CCDs operate only in frame integration. Focal length: Distance between the optical center of a lens and the image focal point. Fixes the magnification and the angle of view of a lens. Vari-focal and zoom lenses have a variable focal length. Frame: One complete TV picture consisting of two sequential interlaced scanned fields. NTSC/EIA has 30 frames of 525 lines per second. PAL/CCIR has 25 frames of 625 lines per second. Gain: The electronic amplification factor of a signal. Gamma: Correction law introduced in the camera output signal to compensate for the non-linearity of the CRT (Cathode Ray Tube) in video monitors. A typical gamma value is 0.45, which results in the brightness component of the CRT picture appearing to be linear. Genlock: Circuitry that synchronizes one video signal to another video signal. There are three types of genlock: V-lock, HV-lock and full color. • V-lock is useful when simply switching from one B/W color source to another • HV-lock is used for full synchronization of B/W cameras, and requires a HD + VD input, composite sync input or composite VS video signal input. In the case of color cameras, this type of synchronization can be used when cutting between pictures, but not for mixing between them. • Full color genlock is used when pictures have to be mixed without color degradation. It needs VBS composite video input. HAC: Host Adapter Card. HAD (Hole Accumulated Diode): CCD technology with improved performance in spectral response, vertical smear and sensitivity. The HAD sensor also introduced a higher pixel count and electronic shuttering capability. HD (Horizontal Drive): Signal used to synchronize the line scan rate of the camera to an external source. Mostly used in B/W applications together with VD. High rate scanning: Capability of a camera to output less than its maximum number of horizontal lines, but at a higher rate. Unlike partial scanning, the lines output in high rate scanning are symmetrical about the optical sensor center. This means that there is normally no need to re-aim the camera when changing from normal to high rate scanning. Horizontal Resolution: Number of equally spaced vertical black-to-white or white-to-black transitions that the camera is able to reproduce, divided by the aspect ratio (usually 4:3) to make a comparison between horizontal and vertical resolution easier. Usually expressed as TV lines per picture height. Indicates the amount of horizontal details that can be perceived. Horizontal resolution is limited by the number of pixels in one line and by the type of color filter used, if any. Hyper HAD: A derivative of the HAD sensor that incorporates microscopic lenses mounted over each sensing pixel. Hyper HAD sensors have no perceptible smear and are nearly twice as sensitive as HAD sensors. ICR (IR Cut Removable): This function is useful in low light environments. With the IR cut filter removed, the sensitivity of the camera to IR illumination is increased. IEEE 1394: A digital networked serial interface for high-speed data transmission. Available speeds are 200 and 400 Mb/s, and 800 Mb/s speed is planned in the near future. IEEE 1394 is an ideal interface between a computer and audio/video products because of its ability to transfer a real-time data stream at low cost, with high reliability and ease of use. Interlaced scanning: Scanning method in which half of the lines are scanned in one field (odd-numbered lines), and the other half are scanned in the next field (even-numbered lines). Thus adjacent lines of a complete picture (one frame) belong to successive fields. Interlaced scanning doubles the screen refresh rate as seen by the viewer and reduces flicker. At screen refresh rates significantly higher than the 25/30 frames/second used in TV systems, interlaced scanning may not be necessary. Interval AF: AF (Auto Focus) mode is periodically switched ON, then OFF (fixed focus). The duration of the on and off intervals is separately adjustable. IT (Interline Transfer): In IT CCD technology, the charges on exposed pixels are transferred to light-shielded vertical readout zones embedded in the sensitive area. IT devices are simpler to manufacture and are therefore less costly than FT or FIT devices. Mostly used in industrial and consumer cameras. Iris: An adjustable sized aperture in a camera lens that controls the amount of light reaching the imager. Compensates for changing lighting conditions. Iris control may be either manual or automatic, depending on the application and the type of camera. When iris is fixed, a variable electronic shutter can be used instead (CCD Iris). Isochronous transmission mode: IEEE 1394 data transmission mode featuring guaranteed transmission timing and bandwidth. Appropriate for just-in-time transmission of video and audio and computer data. Long-term integration: Special camera mode similar to the 'B' setting of a photographic camera shutter. The CCD integrates over a long (userdefined) period, providing very high sensitivity. Object must be stationary, external camera control and a frame memory are needed. Luminance: The part of a composite video signal that expresses brightness. Also called Y. Separately transmitted in Y/C (S-video). Lux (lux): The SI measurement of light intensity taken at the surface which the light source is illuminating. The measure of the total lumens falling upon a unit of area. 1 lumen per square meter. One Foot-candle equals 10.76 lux. Minimum illumination: Minimum light level needed to achieve a 50% or 100% video output level when the camera is at maximum gain and the lens iris fully open. Can be computed from the nominal sensitivity, lens characteristics and maximum gain. MOD (Minimum Object Distance): A lens parameter that defines the minimum distance from a camera lens to the point where an object can still be in focus. MD (Motion Detector): Camera feature where a reference field is compared with current fields. If a difference is detected, the camera outputs a pulse. An ideal feature for security application. MTF (Modulation Transfer Function): Defines the resolution capability of a lens. Most lenses exhibit their best MTF when operated in the middle of their iris aperture range. ND Filter (Neutral Density Filter): A grey filter added in front of a lens to reduce the amount of incoming light into the camera lens. It has no influence on color. NF Mount: Type of camera mount in which there is 12 mm clearance between the lens rear mounting surface and the camera's CCD. NTSC (National Television System Committee): Color video standard, used mainly in the United States and Japan. NTSC uses 525 scanning lines per picture, 30 pictures (frames) per second, each frame is made up of two sequential fields containing respectively the even and the odd lines (interlace). One-push AF (One-push Auto Focus): Focus hold mode that can be automatically readjusted as required by the user (One-push AF Trigger) assuming that the required subject is within the focusing limits of the camera lens. Glossary