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Production Technologies The Central Role of the Lens in HDTV Imaging Laurence J. Thorpe Broadcast & Communications Canon U.S.A.

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Presentation on theme: "Production Technologies The Central Role of the Lens in HDTV Imaging Laurence J. Thorpe Broadcast & Communications Canon U.S.A."— Presentation transcript:

1 Production Technologies The Central Role of the Lens in HDTV Imaging Laurence J. Thorpe Broadcast & Communications Canon U.S.A.

2 Broadcast Transmission Systems > Signal Integrity > Quality of Service > Channel capacity > Transmission Impairments > Noise > Interference > Fading > Ghosts > Reflections > Bit Error Rates

3 The HDTV Lens as Transmission System > Optical Image Integrity > Quality of Service – namely, Quality of Image > “Channel” capacity – namely, Sensitivity > Transmission Impairments > Fundamental Optical Limitations > Distortions > Aberrations > Ghosts > Reflections

4 HDTV Lens as Transmission System

5 HDTV Production Creative Role of the HD Lens

6 Role of the HDTV Lens Represent In digital domain Capture on Digital Media Create The Optical Image Scene Lighting Lens Image is completely defined at this point Digital Camera Digital Recorder

7 Creation of the Optical Image Multidimensional Aspect of the Optical Image Shaping the Image > Angle of View > Framing of a chosen image segment from object scene > Zoom > Real-time dynamic adjustment to Angle of View > Depth of Field > Expressing a 3-D representation on a 2-D image > Perspective > Further creative adjustment to sense of picture depth

8 Creation of Optical Image Multidimensional Aspect of the Optical Image Qualifying the Picture > Contrast > Tonal Reproduction > Color Reproduction > Lens Transmittance Characteristic > Picture Sharpness > Resolution – what is this in the context of “distant” viewing ?

9 Quality Optics for HDTV TheLens-Camera Imaging System

10 Role of the Digital Camera Imaging System RGB Digital Processing Facilitates adjustments to meet the prescribed HDTV Production Standard RGB Digital Opto-Digital Transformation Digital Modification Digital Representation Of the Optical Image Detent Settings: ITU 709 High Def Standard Optical Representation Of the Object Scene Digital Representation According to ITU 709 Digital Representation According to ITU 709

11 Role of the Digital Camera Imaging System RGB Digital Processing Facilitates adjustments to: Tonal Reproduction (Gamma and Knee) Color Reproduction (Colorimetry) Picture Sharpness ( Image Enhancement) RGB Digital Opto-Digital Transformation Digital Modification Digital Representation Of the Optical Image Adjustable Settings: Creative Control Optical Representation Of the Object Scene Digital Representation According to Creative & Aesthetic Desires Digital Representation According to Creative & Aesthetic Desires

12 The Science of Optical Design > Is a Science of Optimization > Dealing with Multiple Variables > Multiple Picture Attributes > Multiple Aberrations > These Parameters are Dynamic – in that they vary with: > Zoom > Focus > Iris

13 HDTV Studio Zoom Lens

14 Variator Compensator

15 HDTV Zoom Lens Wide Angle Telephoto Mid Zoom Range

16 The Science of Optical Design Multiple Attributes Contributing to Overall Image Performance

17 Image Performance Parameters > Sensitivity > The inherent Optical Speed of the lens (the “channel” capacity) > Picture Contrast > Tonal Reproduction (integrity of the grey scale) > Reproduction of Dark portions of the scene > Handling of strong light sources > Color Reproduction > Color Gamut > Picture Sharpness > Horizontal and Vertical Resolution > Limiting Resolution > Resolving Power

18 The Science of Optical Design Multiple Impairments Attempting to Detract from Overall Image Performance

19 Lens Aberrations For a single Lens Element: There are FIVE aberrations for monochromatic light Mathematically predicted by a German scientist Seidel in 1856

20 Five Aberrations of Seidel 1. Spherical Aberration > Parallel light at lens edge converges to focal point nearer to lens than light passing through center 2. Coma > Comatic aberration is a phenomena visible in the periphery of an image – light rays entering the edge of the lens at an angle converge in the form of a comet 3. Astigmatism > Off-axis subject point appears as an ellipse 4. Curvature of Field > Focusing on a flat object field produces a bowl-shaped optical image 5. Distortion > Geometric distortions – of the pincushion and barrel form

21 Optical Limitations & Aberrations > Optical Physical Limitations > Diffraction – imposes a fundamental limitation to MTF > Relative Light Distribution – Light fall-off from picture center > Focus Breathing – Angle of view changes with focus control > Distortions & Aberrations > Spherical > Curvature of Field > Coma > Astigmatism > Geometric > Chromatic Aberrations (Lateral and Longitudinal) > Flare, Ghosting, and Veiling Glare > Unwanted stray rays – stimulated by highlights Focusing Distortions }

22 Quality Optics – Optimizing Multiple Variables Total Lens Performance Maximum Attributes Minimum Impairments Collective Technology Refinements Collective Manufacturing Processes PerfectLens SDTV Lens HDTV Lens Increasing Costs

23 HDTV Lens-Camera Resolution ConceptOf Modulation Transfer Function (MTF)

24 Modulation Transfer Function (MTF) The Contrast of these Spatial Frequencies Diminishes as the frequency increases The Behavior of that Contrast with Frequency Described by the Modulation Transfer Function

25 Image Resolution as Described by MTF Characteristic VideoTVL / ph Optical LP / mm MTF 100 % Modulation Transfer Function (MTF) Limiting Resolution Lens Contrast Lens Resolving Power

26 Concatenation of MTF (Provides System MTF) Lens Camera Sampling Display Human Visual System MTF #1 X MTF #2 X MTF #3 X MTF #4

27 HorizMTF 1080 TVL/ph Horizontal Carrier Nyquist Limit Nyquist Limit 50% TVL/ph 100% 800 Ref Measurement 30 MHz HD Camera 45% Lens Typical 1920 (H) x 1080(V) HD Camera and Lens 2160 SMPTE Specified Filter

28 HDTV Resolution PictureSharpness

29 Picture Sharpness Visual Picture Sharpness Is Proportional to the Square of the Area under the MTF Curve Otto Schade Snr RCA Research Labs

30 Picture Sharpness VideoTVL / ph Optical LP / mm ContrastLevel 100 % Modulation Transfer Function (MTF) Limiting Resolution Spatial Frequency MTF 2

31 Image Resolution Picture Definition TVL/ph Line Pairs/mm ContrastLevel 100 % PictureSharpness ImageTexture ResolvingPower Most important region of the MTF curve Least important region

32 HorizMTF 1080TVL/phHorizontal Carrier Nyquist Limit Nyquist Limit 50% TVL/ph 100% 800 Ref Measurement The Importance of In-Band MTF Lens-Camera Typical Spec 30 MHz 2160

33 HorizMTF 1080 TVL/ph Horizontal Carrier Nyquist Limit Nyquist Limit Fs 50% TVL/ph 100% 800 Ref Measurement The Importance of In-Band MTF Lens-Camera Typical Spec Unspecified – but Vitally important To Picture Sharpness 30 MHz 1920

34 The Studio Lens Optimization of Picture Sharpness High MTF Across Image Plane Minimum Defocusing Distortions High Contrast Flat Relative Illumination

35 LP/mm Line-Pairs per Millimeter 100 MTF % Relative MTF of HDTV and SDTV 2/3-Inch Studio Lens Measured at Picture Center F-4.0 SDTV 16:9 5.5 MHz SDTV Band-edge

36 LP/mm Line-Pairs per Millimeter 100 MTF % Relative MTF of HDTV and SDTV 2/3-Inch Studio Lens Measured at Picture Center F-4.0 SDTV 16:9 5.5 MHz SDTV Band-edge Bandpass Of Interest

37 LP/mm 100 MTF % MTF of 2/3-Inch HDTV Studio Lens Measured at Picture Center F-4.0 HDTV

38 LP/mm 100 MTF % MTF of 2/3-Inch HDTV Studio Lens Measured at Picture Center F-4.0 HDTV 1080/60i HDTV Band-edge

39 LP/mm Line-Pairs per Millimeter 100 MTF % Relative MTF of HDTV and SDTV 2/3-Inch Studio Lens Measured at Picture Center F-4.0 HDTV SDTV 16:9 5.5 MHz SDTV Band-edge 1080/60i HDTV Band-edge Bandpass Of Interest Bandpass Of Interest X 2.7

40 LP/mm 100 MTF % MTF of 2/3-Inch HDTV Studio Lens Measured at Picture Center F-4.0 HDTV 56 LP/mm 1080/60i HDTV Band-edge Optical Reference Camera Reference 74 LP/mm

41 LP/mm 100 MTF % MTF of 2/3-Inch HDTV Studio Lens Measured at Picture Center F-4.0 HDTV 56 LP/mm 720/60P HDTV Band-edge Optical Reference 720P Camera Reference 49 LP/mm

42 LP/mm Line-Pairs per Millimeter 100 MTF % Relative MTF of HDTV and SDTV 2/3-Inch Studio Lens Measured at Picture Center F-4.0 HDTV SDTV 16:9 5.5 MHz SDTV Band-edge 1080/60i HDTV Band-edge Optical Reference 56

43 Picture Sharpness and MTF MTF is Dynamic Across the Image Plane

44 16:9 HD Lens MTF Measurements 2.0 mm 3.9 mm 9.6 mm 3.5 mm 7.0 mm 5.4 mm Corner Middle Center

45 Lens MTF across Image Plane (Measured at 56 Lp/mm or 600 f-4.0) MTF % Center Middle Corner

46 Lens MTF across Image Plane Measured at 56 Lp/mm (or 600 F MTF % Center Middle Corner SDTV HDTV

47 Picture Sharpness and MTF MTF Varies with Focal Length

48 Variation of MTF with Zoom Measured at Picture Center 56 F MTF % Wide Tele HDTV SDTV Focal Length in mm

49 MTF Profile with Focal Length (Measured at 56 Lp/mm) Wide-angle Telephoto Mid-range MTF % Center Middle Corner

50

51

52 Picture Sharpness and MTF MTF Varies with Object Distance

53 Variation of MTF with Object Distance Measured at Picture Center at 56 F MTF % Infinity HDTV SDTV Object Distance in Meters

54 Picture Sharpness and MTF MTF Is Dynamic With Aperture Setting

55 MTF as a Function of Aperture MTF as a Function of Aperture The Perfect Lens (Diffraction Limited) F 2.0 F 4.0 F 8.0 F 16.0 Modulation Transfer Function (MTF) 100% TVL/ph 74 Lp/mm 800TVL/ph 56 Lp/mm 600 TVL/ph HD Reference 27.5MHz 800 TVL/ph (1080-Line System) Optical Reference 30MHz 872 TVL/ph Lp/mm SDTV 400 TVL/ph 30 Lp/mm HDTV Passband

56 MTF Profile with Focal Length (Measured at 56 Lp/mm) Wide-angle Telephoto Mid-range MTF % Center Middle Corner Iris Wide Open

57 MTF Profile with Focal Length (Measured at 56 Lp/mm) Wide-angle Telephoto Mid-range MTF % Center Middle Corner Aperture F- 4.0

58 HDTV Lens Light Management Within the Lens Transmission System

59 Light Management 1. Spectral Transmittance > Sensitivity > Color Reproduction 2. Relative Light Distribution 3. Chromatic Aberrations > Lateral > Longitudinal

60 HDTV Lens SpectralTransmission

61 Lens Spectral Transmittance

62

63 Spectral Transmittance Lens Color Reproduction

64 HDTV Color Reproduction A/D Sample & Hold Amplifier CCD Imager Lens Prism Imager Spectral Spectral Spectral Linear Matrix Transmittance Shaping Response Digital Processing Lens Beam Splitter X X X

65 Studio Tungsten 3200 degree IR Cut Filter Generic Camera Prism CCD Imager

66 Many Variables relating to Color Reproduction CAMERA PRISM IMAGER LENS Canon Fujinon Matsushita Sony Toshiba Angenieux Canon Fujinon Hitachi Ikegami Panasonic Sony Thomson

67 Testing the HDTV Lens Relative Light Distribution

68 Specification of Light Distribution 9.6 mm 5.4 mm 5.5mm 4.8mm 2.7mm Image Height

69 Lens Relative Light Distribution > The Lens F-Number > Indicates the Amount of Light collected at the Center of the Image 1. Natural Vignetting > Off-axis Points do not receive this same Amount of Light > Cosine 4 th Power Law – light reaching the image margins decreases as the 4 th power of the Cosine of angle of view 2. Optical Vignetting > Oblique light rays are presented with a lesser lens opening than on-axis rays 3. Mechanical or “Hard” Vignetting > Caused by extensions added to the lens – lens hoods, matte box holders etc

70 Lens Light Distribution

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