Advance features for existing SDK lost

Transcription

1 Advance features for existing SDK lost scanning data- how SDK decodes images In SDK, you can use invert pattern to get better result. But the issue still happens at low difference. GRAY_CODE_PARAMETERS_PATTERN_INCLUDE_INVERTED = 1 Sense data Loss data threshold 29

2 Advance features for existing SDK lost scanning data- how SDK works Symptom: There are always black line in scanning result. They are invalid point cloud. Root cause: SDK uses fixed threshold to find the boundary of Gary code. GRAY_CODE_PARAMETERS_PIXEL_THRESHOLD = 10 Ideal condition: Depth map image Disparity map Invert pattern: positive negative pattern; non-invert pattern: pattern - albedo threshold If boundary is clear, brightness difference >10. You can get clear disparity map. 30

3 Advance features for existing SDK lost scanning data- failed condition Fix threshold cannot find correct boundary in bad contrast condition below. low albedo - Bad focus from Projector or camera - low camera resolution Loss some data around boundary high albedo\ flare 31

4 Advance features for existing SDK lost scanning data- find cross point for boundary Solution: put the rule to find the cross point for boundary of Gray code pattern in SDK Rule to search in check period: Search vertical direction for horizontal pattern vice versa. For plateau 1 and 2 Must exist, Disparity is different, polarity is different, plateau > plateau_limit 1 All checks must happen in check period Plateau 1 Plateau 2 noise threshold low albedo threshold Check period 32

5 Advance features for existing SDK lost scanning data Test Result on low albedo Find cross point Existing SDK Work better at low albedo area Retrieved lost data Depth map: Color represent the depth, black means no data(point cloud)

6 Advance features for existing SDK lost scanning data Test Result with low albedo threshold If polarity doesn t change, use low albedo threshold W/ low albedo threshold difference W/o low albedo threshold Vertices: New + w/o low albedo: Vertices: New + w/ low albedo: Get back ~1% lost data from low albedo

7 Advance features for existing SDK lost scanning data Test Result on defocus Defocus: all test condition is in defocus. For very bad focus: you need to fine tune cross_point_limit to get better result ?

8 Advance features for existing SDK lost scanning data Test Result on lower camera resolution Lower camera resolution (528*362) and for finest horizontal bar there is only 10pixels of camera sensor. Need to make sure plateau_limit is smaller than this. Plateau_limit is smaller than sensor data Plateau_limit is close to sensor data Sensor on finest line pixels 36

9 Advance features for existing SDK lost scanning data other symptom Edge left\ top(there is no data at left\ top side): the first few pixels from left\ top side would have same lost data issue as existing SDK. Can get it back by re-running the alg. from opposite side again. Edge right\ bottom sensor boundary not sensor boundary Edge top(horizontal pattern) (sensor boundary)(plateau_limit = 5) Top is If plateau_limit = 3, it becomes better. 37

10 Advance features for existing SDK lost scanning data other For calculation,, tan 3 is impossible. So, in code, we remove this pixel with this value.,, 2,,, But it could happen when it s very close and rounded to. W/o filter filter 38

11 Advance features for existing SDK lost scanning data speed affect Run at Step 7 (Horizontal scan) 1280x1024 standard (20Hz) 528x362 standard (20Hz) 528x362 max speed (180Hz) Pattern count x362 max speed + cross point (180Hz) Pattern sequence capture completed in (ms) Image retrieve from buffer in Patterns stored(ms) Horizontal patterns decoded in (ms) Point cloud reconstructed in (ms) vertices ms

12 Advance features for existing SDK lost scanning data conclusion Original SDK using fixed threshold cannot find correct boundary and loss the useful data. find cross point can help find the more accurate boundary for pattern code. It works more obviously when focus is not good. It doesn t affect the result with Gray code only if camera resolution is very close to DMD\ pattern resolution. 40

13 Advance features for existing SDK lost scanning data Notes to use find cross point Around image sensor boundary, there is unchecking area plateau_limit = 5. You can reduce the size but it should be at least 3. Need to adjust cross_point_limit for defocus. Higher is better for defocus. But it may have issue for high frequency pattern or lower camera resolution. For the area with highest frequency pattern, bright(or black) bar pixels must > plateau_limit plus some buffer. The buffer may be like 2. If left and up side has no data, it would lost few more pixels of data than other side. But it may be good because those data could be wrong because of defocus of projection edge. If right and down side has no data, it may get into low albedo. But eventually the data would be removed because noisy data in next few pixels needs to have same polarity with previous pixels. So, it should be fine. 41

14 Demo with find cross point Code change: standard standard Max speed Max speed + find cross point pattern rate 20Hz 20Hz 180Hz 180Hz camera resolution 1280x x x x362 Loss data obvious Very obvious Very obvious Good gray_code.cpp three_phase.cpp lcr4500.cpp 42