IEEE-208-1995-R2005.pdf
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1、The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright 2005 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 1995. Printed in the United States of America. IEEE is a registered trademark in the U.
2、S. Patent however, copies can be obtained from the IEEE, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA. IEEE RESOLUTION OF CAMERA SYSTEMS, 1993 TECHNIQUESStd 208-1995 3 4. Test and measuring equipment requirements 4.1 Test chart The essential tool for measurement of resolution is a su
3、itable test chart. The IEEE Resolution Chart, 1993 (gure B.1 in annex B) is recommended for this purpose. This chart may be used directly for measurement of television cameras. NOTEIf the measured amplitudes at numerous TV line numbers are plotted, the resulting graph is dened as the hori- zontal re
4、solution response characteristic. Horizontal resolution response is referenced to TV lines (square wave pat- terns), and is dened as a percentage of the referenced value, 100%. In addition to being used for the measurement of resolution, the IEEE Resolution Chart, 1993 may be employed as an aid in c
5、hecking scanning linearity, aspect ratio, interlacing, shading, streaking, and ringing. 4.2 Picture monitor When a picture monitor is used to measure the resolution of a camera system, a monochrome monitor is recommended, and it should have a resolution capability exceeding that of the camera system
6、 to avoid mea- surement errors. 4.3 Oscilloscope/wave form monitor For the measurement of the resolution response of a camera system, an oscilloscope or wave form monitor of sufciently wide bandwidth is required to avoid measurement errors. Frequency response should be uniform and equal to or greate
7、r than that required to accurately measure the system/circuit under test. The highest fundamental electronic signal frequency resulting from the IEEE Resolution Chart, 1993 (see gure B.1) when used with a television system conforming to system M (525 line, 59.94 eldsee table A.1), is 12.7 MHz. The e
8、lectronic signal frequency may be calculated for any value of TV lines on the resolution chart by the following formula: Frequency = (1/2) (TVL) (Width Height) (1 Horizontal Active Line Time) The oscilloscope/wave form monitor should be equipped with a line selector that will permit the selection, d
9、isplay, and identication of any desired horizontal scan interval once each frame time. -,-,- IEEE Std 208-1995IEEE STANDARD ON VIDEO TECHNIQUES: MEASUREMENT OF 4 5. Measurement procedure 5.1 Conditions Before a signicant measurement of resolution is made, it is essential that the television camera s
10、ystem under test be properly adjusted, and that the IEEE Resolution Chart, 1993 (see gure B.1) be oriented and aligned perpendicular to the optical axis to permit the camera to accurately reproduce its image. Care should be applied to assuring that the base of the camera and the edge of the chart re
11、st on, or be referenced to, the same level surface. Further, the geometric center of the chart must be aligned, and perpendicular with the optical axis (center line) of the camera lens and optical system. Finally, after adjusting lens focal length (if equipped) and other lens adjustments to their op
12、timum settings (see condition 5.1.7), the distance between the chart and the camera should be adjusted until the entire resolution chart is just completely reproduced by the camera. Two arrowheads located at each edge of the resolution chart are provided to aid in the correct orientation and the com
13、plete composition of the chart within the picture raster observed on the monitor. The test pattern on the chart is correctly oriented and composed when the camera is adjusted such that the point of every arrow just touches its corresponding edge of the picture monitor raster. After the test pattern
14、has been correctly oriented with respect to the camera, the following items are among those that shall be given attention: 5.1.1 Scanning and interlace For cameras that utilize imaging tubes, care should be taken to check and adjust for proper scanning size, scanning linearity, aspect ratio, and int
15、erlace. For measurement and adjustment of scanning size and linearity and aspect ratio, it is suggested that reference be made to IEEE Std 202-1954. 2 Interlace will affect vertical resolution; hence, any adjustments in the system that inuence interlace should be optimized. 5.1.2 Shading If the came
16、ra equipment employs signals for camera-shading correction, two methods for proper adjustment are suggested: a)Visual inspection of the picture monitor to determine if the background is an even gray b)Use of the wave form monitor to determine whether the average picture signal axis is parallel to th
17、e black level line, both at line and eld frequencies 5.1.3 Nonlinear video signal processing The inuence of nonlinear video signal processing such as gamma correction, white compression (knee), black compression, and expansion (stretch), should be avoided to assure accurate and uniform resolution me
18、asurement. 5.1.4 Image enhancement The inuence of image enhancing video signal processing such as aperture correction, contour correction (detail), and others, should be avoided to assure accurate and uniform resolution measurement. 2 Information on references can be found in clause 2. -,-,- IEEE RE
19、SOLUTION OF CAMERA SYSTEMS, 1993 TECHNIQUESStd 208-1995 5 5.1.5 Streaking and ringing Streaking following any one of the horizontal black or white bars is an indication of low-frequency distor- tion in the video processing circuits. Ringing, or multiple echoes following any single vertical line, is
20、a function of the high-frequency response of the system. These echoes may be confused with the multiple lines of the resolution wedge and hence lead to an inaccurate determination of resolution. 5.1.6 Focus All optical and electrical focusing at the camera should be optimized. 5.1.7 Light level The
21、desired light level value is that which permits all of the elements of the camera system to be adjusted to their optimum performance positions. For instance, lens settings for iris, focus, and focal length, are usually optimum at about the center of their adjustment ranges. 5.1.8 Signal component to
22、 be measured For color cameras, it is recommended that resolution be measured only for the luminance video signal. Color signal components contained in the output signal should be disabled or eliminated. The preferred point for measurement of resolution is the camera output connection that the camer
23、a manufacturer directs be con- nected to a principal program input of a video system. 5.2 Measurement technique 5.2.1 Measurement of limiting resolution After assuring that the conditions described in 5.1 are satised, limiting resolution may be determined by observing the reproduced resolution chart
24、 on a picture monitor. The limiting horizontal and vertical resolu- tion of the television camera chain and picture display combination is determined by observing the point at which the individual lines of the graduated wedges are no longer discernible as separately dened images. The resolution read
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