RCCC CMOS Sensor color space creation
RCCC Sensor Color space
•RCCC color space was created to assess the chromatic ability of RCCC system.
•F=(C-R)/C represents color spaces as follow:
•The diagram at left represent only pure color conditions.
White balance & color coordination
•The F=0.45 was set as the white balance point for the current RCCC system.
•F=0 is pure red.
•0<F<0.45 is variety of colors with more red component when F is smaller.
•F=0.45 and nearby is either white or yellow& brawn.
•1>F>0.45 is colors other then Red
Full color space response
RCCC response category 1
RCCC response category 2
RCCC response category 3
RCCC response category 4
Retro reflective night stop sign
•The retro reflective signs illuminated by head lamp make the image saturated.
•At this condition, RGB system may still works.
RCCC sensor saturation
•When RCCC pixels saturated at most cases by white reflection, it outputs them as red.
•Add saturation detection at algorithm can tells the red output at saturation pixels may not be true, but it can be almost any colors including red.
Red lights response
•Red lights can be detect reliably at night condition.
•Saturated white lamp can be mistaken as red.
•The red lights detection can still fail by phantom effect and surface imperfect at day time.
•Phantom effect lights is polarized which can be partially optically filtered out.
Rainy condition response
•At rainy condition, the RCCC system response to the red as orange.
Red sign at snow day
•The red sign appear white at snow day in the RCCC system, although it still can be identified as red in the RGB system.
Sign Reflection
•Sign boards often reflect the light from the sky or from an approaching car during the weak daylight hours or head lamp during night.
•the headlights of the vehicle can be clearly seen on the sign board. The reflect is treated as red by the RCCC while the RGB system take it as a bright spot.
Sunny day Partial shadow
•The red dyes reflect the red component for the stop sign which is the components we want the sensor only response of.
•Out door lighting skew its colors on traffic signs due to the impurity of the dye. Weather, time of day and season all will skew the color.
•The spectacular reflection of top coating will cost directional illumination which form significant portion of pixel value, which is polarized.
•The reflection beads imbedded response with chromatic aberration which is directional to the incoming lights.
•The imperfection and dust on the surface cause Lambertian reflectance which mirror s the illumination source color.
•The partial shadow or directly illuminated part of the traffic sign have white balance off due to the camera can not response for the two different color temperature at same time. The shadow portion illumination itself is polarized, the direct illuminated portion the reflection is polarized.
OBSERVATION AND DISCUSSION
PROS & CONS
•Under ideal condition, Pure Red is the only color can be identified with certain by the RCCC system under two channel color system. For other colors, the system can only group them into several categories; can not pinpoint exactly what color it is.
•In application level, the red detection ability basically means the system can be used for red color signal lamps identification. The traffic sign segregation will be less reliable due to the fact that the reflective color of traffic sign is not pure enough.
•White balance also contributes to the detection error of red color under out door condition.
•Although the red sign lamp detection ability make the RCCC sensor works for the intelligent head lamp control application to detect the tail lamps in the evening. The RCCC sensor saturation response property makes it more difficulty for the combo application, since the system mistaken the saturated pixels as red.
•Basically 4X of spatial resolution than RGB, which may be the biggest advantage over RGB sensor
•The clear pixel has 2X speed than RGB sensors.
•Still keep about 50% ability to differentiate colors