Over the last couple of weeks extra measurments were performed to better understand the working and limitations of the Phase Detection Auto Focus Pixels. The extra measurements focused on :
– the influence of the exposure time on the PDAF pixel signals and the possibility to extract useful focusing information from it,
– angular light dependency of the PDAF pixels.
The new measurements are included in an update version of the report. The full report is still available through info (at) harvestimaging (dot) com.
Below you find the table of contents of the updated version of the report.
15-01-2016.
Table of Contents
List of Figures
Introduction
Working principle of PDAF pixels
Theoretical implementation of PDAF pixels
Practical implementation of PDAF pixels
From the theory to the reality
Measurement 1 : influence of F-number
Measurement 2 : influence of the object distance
Measurement 3 : influence of the object angle
Measurement 4 : influence of the PDAF location on the sensor
Measurement 5 : influence of the object colour
Measurement 6 : Influence of exposure time
Conclusions
Appendix : angular dependency of the PDAF pixel sensitivity
Acknowledgement
References
List of Figures
Figure 1. Imaging with a positive lens
Figure 2. Requirement to have an image in-focus at the surface of the image sensor
Figure 3. illustration of rear focus, in-focus and front focus
Figure 4. Illustration of two different rear focus situations
Figure 5. Illustration of two different front focus situations
Figure 6. Optical ray formation from the object till the photodiode of an image sensor
Figure 7. Optical ray formation from the object till the partly optically-shielded photodiodes/pixels of an image sensor
Figure 8. Aptina’s MT9J007C1HS architecture with 9 rows containing auto-focus pixels based on phase detection
Figure 9. Microphotograph of one of the AF rows
Figure 10. Magnified view of an AF row
Figure 11. Microphotograph of an AF row
Figure 12. Sensor architecture indicating the various AF lines as well as the different zones used to read the sensor
Figure 13. Image taken from a random scenery with the AF option switched ON
Figure 14. Analysis of the signals of AF-line 5 in zone 5
Figure 15. Image taken from the same scenery as in Figure 13 with the AF option switched OFF and manually focused on the “macro” position
Figure 16. Analysis of the signal of AF-line 5 in zone 5 in the case the AF system is forced to “macro” position
Figure 17. Image taken from the same scenery as in Figure 13 with the AF option switched OFF, and manually focused on the “infinity” position
Figure 18. Analysis of the signals of AF-line 5 in zone 5 in the case the AF system is forced to “infinity” position
Figure 19. Odd and even PDAF signal for an object place 50 cm in front of the camera and the lens switched to auto-focus “ON”
Figure 20. Odd and even PDAF signal for an object placed 50 cm in front of the camera and the lens focusing on “infinity”
Figure 21. Odd and even PDAF signal for an object place 50 cm in front of the camera and the lens focusing on “macro”
Figure 22. Depth-of-field as a function of the object distance for 3 F-numbers, the dotted lines indicate the corresponding hyper-focal distances
Figure 23 PDAF pixel shift as a function of F-number for an object 50 cm in front of the camera and auto focusing
Figure 24 PDAF pixel shift as a function of F-number for an object 50 cm in front of the camera and focusing at “infinity”
Figure 25 PDAF pixel shift as a function of F-number for an object 50 cm in front of the camera and focusing at “macro”
Figure 26 Front-focus situation
Figure 27. PDAF pixel shift as a function of object distance and auto-focus setting of the camera, with F2.8
Figure 28. PDAF pixel shift as a function of object distance and auto-focus setting of the camera, with F5.6
Figure 29. PDAF pixel shift as a function of object distance and auto-focus setting of the camera, with F11
Figure 30. PDAF pixel shift as a function of object distance, lens auto-focus setting on “infinity” and with F2.8
Figure 31. PDAF pixel shift as a function of object distance, lens auto-focus setting on “infinity” and with F5.6
Figure 32. PDAF pixel shift as a function of object distance, lens auto-focus setting on “infinity” and with F11
Figure 33. PDAF pixel shift as a function of object distance, lens auto-focus setting on “macro” and with F2.8
Figure 34. PDAF pixel shift as a function of object distance, lens auto-focus setting on “macro” and with F5.6
Figure 35. PDAF pixel shift as a function of object distance, lens auto-focus setting on “macro” and with F11
Figure 36. PDAF pixel shift as a function of object distance, lens focusing fixed at 60 cm and F2.8
Figure 37. PDAF pixel shift as a function of object distance, lens focusing fixed at 60 cm and F5.6
Figure 38. PDAF pixel shift as a function of object distance, lens focusing fixed at 60 cm and F11
Figure 39. PDAF pixel shift as a function of object angle and auto-focus setting of the camera, with F2.8
Figure 40. PDAF pixel shift as a function of object angle and auto-focus setting of the camera, with F11
Figure 41. PDAF pixel shift as a function of object angle, lens focusing on “infinity” and with F2.8
Figure 42. PDAF pixel shift as a function of object angle, lens focusing on “infinity” and with F11
Figure 43. PDAF pixel shift as a function of object angle, lens focusing on “macro” and with F2.8
Figure 44. PDAF pixel shift as a function of object angle, lens focusing on “macro” and with F11
Figure 45. PDAF pixel shift as a function of the PDAF location in readout zone 5 and auto-focus setting of the camera, with F2.8
Figure 46. PDAF pixel shift as a function of the PDAF location in readout zone 5 and auto-focus setting of the camera, with F11
Figure 47. PDAF pixel shift as a function of the PDAF location in readout zone 5 and lens focusing on “infinity” and with F2.8
Figure 48. PDAF pixel shift as a function of the PDAF location in readout zone 5 and lens focusing on “infinity” and with F11
Figure 49. PDAF pixel shift as a function of the PDAF location in readout zone 5 and lens focusing on “macro” and with F2.8
Figure 50. PDAF pixel shift as a function of the PDAF location in readout zone 5 and lens focusing on “macro” and with F11
Figure 51. Location of the various PDAF regions under test
Figure 52. PDAF pixel shift as a function of the PDAF location on AF-line 5 and on the diagonal with auto-focus setting of the camera and F2.8
Figure 53. PDAF pixel shift as a function of the PDAF location on AF-line 5 and on the diagonal with auto-focus setting of the camera and F11
Figure 54. PDAF pixel shift as a function of the PDAF location on AF-line 5 and on the diagonal with focus set to “infinity” and F2.8
Figure 55. PDAF pixel shift as a function of the PDAF location on AF-line 5 and on the diagonal with focus set to “infinity” and F11
Figure 56. PDAF pixel shift as a function of the PDAF location on AF-line 5 and on the diagonal with focus set to “macro” and F2.8
Figure 57. PDAF pixel shift as a function of the PDAF location on AF-line 5 and on the diagonal with focus set to “macro” and F11
Figure 58. Pulses used to measure the PDAF pulse shifts in zones 2 to 5 on the AF-line 5, lens focus at “infinity” and F2.8
Figure 59. Incoming rays for a PDAF pair at the edge of the sensor
Figure 60. Pulses used to measure the PDAF pulse shifts in zones 2 to 5 on the AF-line 5, lens focus at “macro” and F11
Figure 61. Odd and even pulses in AF-line 5, in AF-line 5 + 1 line and in AF-line 5 + 2 lines, with green light input, F2.8 and focusing at “infinity”
Figure 62. Odd and even pulses in AF-line 5, in AF-line 5 + 1 line and in AF-line 5 + 2 lines, with green light input, F2.8 and focusing at “infinity”
Figure 63. Odd and even pulses in AF-line 5, in AF-line 5 + 1 line and in AF-line 5 + 2 lines, with green light input, F2.8 and focusing at “infinity”
Figure 64. PDAF pixel shift as a function of object colour and auto-focus setting of the camera, with F2.8
Figure 65. PDAF pixel shift as a function of object colour and auto-focus setting of the camera, with F11
Figure 66. PDAF pixel shift as a function of object colour, lens focusing on “infinity” and with F2.8
Figure 67. PDAF pixel shift as a function of object colour, lens focusing on “infinity” and with F11
Figure 68. PDAF pixel shift as a function of object colour, lens focusing on “macro” and with F2.8
Figure 69. PDAF pixel shift as a function of object colour, lens focusing on “macro” and with F11
Figure 70. PDAF pixel shift as a function of exposure time, with F2.8, focusing on “macro” and white light input
Figure 71. PDAF pixel shift as a function of exposure time, with F2.8, focusing on “macro” and green light input
Figure 72. PDAF pixel shift as a function of exposure time, with F2.8, focusing on “macro” and blue light input
Figure 73. PDAF pixel shift as a function of exposure time, with F2.8, focusing on “macro” and red light input
Figure 74. Angular dependency of the PDAF pixels under the influence of white light
Figure 75. Angular dependency of the PDAF pixels (corrected data) in combination with the sum of the PDAF pixel signals
Figure 76. Angular dependency of the PDAF pixels (corrected data) in combination with the green pixels signals from neighbouring red-green and blue-green rows
I was wondering the PDAF pixels might bring chromatic aberration problem, I can see very clear purple fringing at corner. So might be problem of dual-PD.