The forward facing automotive camera is a rapidly developing application.  The first systems were relegated to simple functions such as intelligent headlamp control (IHC), lane departure warning (LDW), or rain sensing.  Succeeding generations of forward facing cameras may incorporate multiple advanced functions such as: adaptive cruise control (ACC), forward collision warning (FCW), traffic sign recognition (TSR), pedestrian detection, obstacle detection and night vision.  These demanding applications require spiraling improvements in image processing, sensors and lenses. Sunex is pleased to be at the fore front of lens technology for forward facing camera systems. 

Compared to a rear vision lens the optical performance requirements for a forward facing lens are completely different but no less challenging.  A typical optical performance requires high resolution, low F-number, low distortion and minimal package size.  In addition, since the next generation forward facing cameras will use high- or wide dynamic range (HDR or WDR) sensors, special attention must be paid to veiling glare and stray light effects.  Sunex has developed proprietary design, simulation capability, coating, test and process tools that help to address these critical issues. The following shows an example of ghost image simulation, and high efficiency coating solutions to minimize the intensity of ghosting images.

Simulation using non-sequential ray tracing

Ghost images are caused by multiple reflections between the surfaces of the optical system including the lens elements surfaces, filter surfaces and CMOS imager cover glass surfaces. Before a ray reaches the imager active surface, it must pass thru all these optical surfaces.  At each optical surface, a small fraction of ray energy will be reflected backward due to the law of reflection.  This reflected ray can be reflected again by some other optical surfaces forming "ghost" images on the imager active surface. This phenomenon can be modeled using non-sequential ray tracing techniques.  The following diagram shows an example:

Once a high number of rays are analyzed, it is possible to generate an intensity profile on the imager active surface as follows:

An example of stray light simulation

Ghost mitigation

Ghost images are common among all lenses. However there are ways to minimize or eliminate "offensive" ghosts including choosing proper optical designs defocusing the ghost images, and by using highly efficient coatings on the lens/filter surfaces. The intensity of the reflected light is proportional to the reflectivity of the optical surface. For an uncoated optical surface, the average reflectivity is on the order of 4-5% over the visible spectral range. A double-reflected ghost ray will have a relative intensity of ~ 4.5%x4.5%=0.2%. A standard anti-reflection (AR) coating reduces the ghost intensity to ~ 0.023% (a 10x reduction). Sunex's BBAR coating technology enables further drastic reduction by reducing the surface reflectivity to as low as 0.3% per surface. This results in a relative ghost intensity of only 0.0009%, a 25x reduction from standard AR coating. The following curve shows the nominal reflectivity of each AR coating:

Below are several lenses specifically designed for forward facing automotive cameras that represent the state of the art.  These lenses are also applicable to critical applications where high-dynamic images are important such as security and surveillance in outdoor environment. The off-the-shelf solutions you see below are often a good starting point for a custom OEM solution.  If you cannot find the product that exactly meets your requirements, please contact us.

PN	Description	Focal length(mm)	f/#	Imager Format	Field of view/ Depth of field	Recommended Holder	Sample Price (1-99)	Volume Price
DSL819B	Low-profile glass lens with IR cut coating for 1/3.4" sensor, EFL=5.1, F/2.8, M8x0.5, metal barrel	5.1	2.8	1/3.4"	Calculate FOV Calculate DOF	CMT830	$39 Order Sample	Request Volume Quote
DSL946D-700	Low stray light lens for High or Wide Dynamic Range, IR cut-off at 700nm, EFL=5.7, F/1.6, metal barrel threaded M8x0.5	5.7	1.6	1/3"	Calculate FOV Calculate DOF	CMT821	$49 Order Sample	Request Volume Quote
DSL946C-700	Low stray light lens for High or Wide Dynamic Range, IR cut-off at 700nm, EFL=5.7, F/1.6, metal barrel threaded M12x0.5	5.7	1.6	1/3"	Calculate FOV Calculate DOF	CMT830	$49 Order Sample	Request Volume Quote
DSL946B-NIR	Low stray light lens for High or Wide Dynamic Range, IR cut-off at 700nm, EFL=5.7, F/1.6, metal barrel threaded M12x0.5	5.7	1.6	1/3"	Calculate FOV Calculate DOF	CMT821	$49 Order Sample	Request Volume Quote
DSL946A-NIR	Low stray light lens for High or Wide Dynamic Range, no IR cut-off, EFL=5.7, F/1.6, metal barrel threaded M8x0.5	5.7	1.6	1/3"	Calculate FOV Calculate DOF	CMT830	$49 Order Sample	Request Volume Quote
DSL849A-NIR	Low stray light lens for High or Wide Dynamic Range, no IR cut-off, EFL=6.0, F/1.9, metal barrel threaded M8x0.5	6	1.9	1/3"	Calculate FOV Calculate DOF		$49 Order Sample	Request Volume Quote
DSL849A-700	Low stray light lens for High or Wide Dynamic Range, IR cut-off at 700nm, EFL=6.0, F/1.9, metal barrel threaded M8x0.5	6	1.9	1/3"	Calculate FOV Calculate DOF		$49 Order Sample	Request Volume Quote
DSL821D-NIR	Standard glass lens for 1/3" sensor, NO IR cut filter, EFL=6, F/2.0, M12x0.5	6	2.8	1/3"	Calculate FOV Calculate DOF	CMT821	$39 Order Sample	Request Volume Quote
DSL208A-650-F2.0	Compact telephoto lens with IR cut coating, for day/night applications up to 1/3" sensor, EFL15.8, F/2.0, M12x0.5, metal barrel	15.8	2	1/3"	Calculate FOV Calculate DOF	CMT107, CMT103 CMT804	$49 Order Sample	Request Volume Quote
DSL208A-NIR-F2.0	Compact telephoto lens for day/night applications up to 1/3" sensor, NO IR cut-coating, EFL15.8, F/2.0, M12x0.5, metal barrel	15.8	2	1/3"	Calculate FOV Calculate DOF	CMT107, CMT103 CMT804	$49 Order Sample	Request Volume Quote

Didn’t find the lens you’re looking for? Try searching our entire lens database using one of the following options:

• By lens focal length and f/#
• By imager PN or imager key specifications
• Click here to request a custom lens
• Contact our support team