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MT9T111_DG - Rev. B 9/10 EN
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MT9T111: Developer Guide
Lens Calibration Procedure
Preliminary
Calibration Procedure
1. Set lighting to D65.
2. Start up DevWare and camera in the default state (load default register settings).
3. Switch to full resolution.
4. Create and load a “
Lens Calibration Setup”
(See “Calibration Procedure Summary”
on page 128 for more details).
4a. Put sensor into Bypass Bayer 8+2 Mode after lens shading correction (PGA Bypass
Mode).
4b. PGA Bypass Mode should automatically bypass the following:
– AWB, AE, flicker detection, histogram, AF drivers in the sequencer, color correc-
tion, and gamma correction
5. Set gains so that the image is white-balanced.
6. Set light level and exposure so that the brightest portion in the center of the image is
about 85% of full scale with approximately gain = 1x (Be sure that no clipping occurs
in any region of the image).
7. Calculate lens correction parameters.
Option 1:
Calculate 2nd order polynomial for X and Y directions.
– Translate polynomial coefficients into lens correction register values.
Option 2:
Use DevWare tool. (See “Calibration Procedure Summary” on page 128 for more
details.)
– To find the optical center of the lens.
– To find the optimal lens correction register values.
8. After applying lens correction, save and capture processed RGB image after lens cor-
rection is applied.
9. Change the firmware variable responsible for flipping the output image. Be sure to do
a refresh mode after each change.
VAR = 18,12,0x01,0 // 0: cam1_ctx_a_horiz_mirror
VAR = 18,12,0x02,1 // 1: cam1_ctx_a_vert_flip
10. Check if the PGA variables responsible for flipping the applied PGA correction reflects
the status of the output image.
BITFIELD = 14208,0x0002,0 // 1: Input image is horizontally flipped.
BITFIELD = 14208,0x0004,1 // 2: Input image is vertically flipped.
Note:
You can use small pieces of painter’s tape on the glass diffuser plate to detect whether
or not the image was flipped. Check the image in Figure 60 on page 124 to ensure the
image is display properly.