Chromatic Aberration of Industrial Megapixel Lens

[Baylab 0]

FA lens has been the only feasible choice for high definition video camera, not matter for industrial quality control application or general purpose video surveillance application, simply because the common CCTV lens can't provide enough resolving ability(resolution of CCTV lens is around 40-60lp/mm, while the resolution of megapixel FA lens could be as high as 120lp/mm at central area and 80-100lp/mm at the edge area ). However, FA lens , not matter rated as megapixel or 3 mega pixel or even 5/10 megapixel, maybe not an perfect solution for the application which need sharp and vivid colour image, some of them may suffer excessive colour aberration.

 

For most industrial inspection project, such colour aberration won't be a real problem, because most of such kind of application use single colour LED illumintion (red, green, or even IR, actually more than half of industrial cameras are B/W model), so the only drawback of such lens is just a slight drop of resolving ability in the edge area. but for the application which need broad band white light illumination, for example general purpose video surveillance or ANPR, the colour aberration will casue serious problem.

 

Here are some test results of a 5mm 1/2" F1.4 megapixel lens (to my opinion, it probably is the only affordable wide angle FA lens which can generate decent image). I attached this lens to a camera with 1/2.5" CMOS imager and reduced the aperture to F2.0 ( just roughly, since there is no any "clicking" mechanism inside its aperture adjusting ring), then turned the camera left and right to capture some picture with different ROI.

 

ROI located at the centre of image, the ROI area is quite sharp and there is no any noticeable chromatic aberration

ROI located at the left side of image, the ROI area suffer significant chromatic aberration.

ROI located at the right side of image, the ROI area suffer chromatic aberration too, just a little bit better than left side.

[Baylab 0]

Cropped and rescaled(300%) ROI in the central of image.

Cropped and rescaled(300%)ROI at left side of image.

Cropped and rescaled(300%)ROI at right side of image.

[Baylab 0]

And as a comparison, here are the test results of a 4.8mm 1/2.5" lens which was develop for a panoramic (with a view angle of 48 deg by 65 degree, so it 6 or 8 such lenses can cover 360degree) camera.

 

ROI in the centre of image. (Cropped ,300% rescaled)

ROI at left side of image. (Cropped ,300% rescaled)

ROI at right side of image. (Cropped ,300% rescaled)

 

So when you choose a lens for some critical application, you need to do some test yourself, the rated megapixel value ( megapixel, 1.5megapixel, 3 megapixel or 5/10 megapixel) or even MTF ( 100lp/mm 120lp/mm or even 150lp/mm) are not guarantee of sharp image for video surveillance project.

 

And, another issue, some lenses were optimised for visible light, if you try to use them for IR illumination, the image will become softer (even after refocusing).

[amirm 0]

Yup. That's why companies like Avigilon use Canon lenses for their high megapixel cameras. While CA exists with any lens especially in the corners, ability to use high-end DSLR lenses helps a lot here.

[shropna 0]

Yup. That's why companies like Avigilon use Canon lenses for their high megapixel cameras. While CA exists with any lens especially in the corners, ability to use high-end DSLR lenses helps a lot here.

Helps only in one way - you should have camera with 35 mm format imager

On small imager, i thing, you will not gave good result....

[amirm 0]

Yup. That's why companies like Avigilon use Canon lenses for their high megapixel cameras. While CA exists with any lens especially in the corners, ability to use high-end DSLR lenses helps a lot here.

Helps only in one way - you should have camera with 35 mm format imager

On small imager, i thing, you will not gave good result....

Yes, it does require having a camera compatible with a DSLR format (but not the same size sensor -- Canon makes DSLRs with three different sizes from full 35 mm to APS-C size. So there is no requirement to have a 35mm sensor).

[hardwired 0]

I've been getting good results with FA lenses from Fujinon and Kowa, both are pretty expensive, though.

 

Another issue that I have been experiencing is sensor misalignment to the focal plane, one side of image always slightly out of focus, see sample here with significant focal shift. (Arecont 5105DN camera, Kowa LMVZ3510-IR Lens)

[shropna 0]

I've been getting good results with FA lenses from Fujinon and Kowa, both are pretty expensive, though.

 

Another issue that I have been experiencing is sensor misalignment to the focal plane, one side of image always slightly out of focus, see sample here with significant focal shift. (Arecont 5105DN camera, Kowa LMVZ3510-IR Lens)

Yes, left side of image..

Imager placing fault, lens is good.

Arecont cameras quality is still bad....

[thewireguys 3]

Had that same problem with a Sanyo HD camera

[cglaeser 0]

Another issue that I have been experiencing is sensor misalignment to the focal plane,

 

Bummer, that one's pretty bad.

 

Best,

Christopher

[shropna 0]

Had that same problem with a Sanyo HD camera

What camera, and what lens?

I'm agree with You, that HD3000 (dome) series has average quality lenses....

But not HD 4600

On 2000 series lots depend on lens quality.... Imager wrong placement i'm dont find....

[thewireguys 3]

Had that same problem with a Sanyo HD camera

What camera, and what lens?

I'm agree with You, that HD3000 (dome) series has average quality lenses....

But not HD 4600

On 2000 series lots depend on lens quality.... Imager wrong placement i'm dont find....

 

Sanyo HD2300... Did not matter what lens I had on it and was way worse then the one I posted above.

[shropna 0]

Sanyo HD2300... Did not matter what lens I had on it and was way worse then the one I posted above.

But lens really matters

[thewireguys 3]

Sanyo HD2300... Did not matter what lens I had on it and was way worse then the one I posted above.

But lens really matters

 

understood..... But lens was not the problem

[Baylab 0]

35mm photography lens probably is a good solution for ancient 2/3'' or 1/2" 1.3 mega pxiel imager, it won't work with current 1/2.5" or 1/2.3" 5MP or 10MP sensor, 1/2.5" 5MP sensor has the same pixel density as a 180MP 35mm full frame sensor ( which haven't been on the market yet, maybe 5- 10 years later?). 20MP should be the limitation for most 35mm photography lens. if you're lucky to get a Canon 5D MKII (which has a 20MP full frame sensor), you need to invest a lots of money on Canon's expensive "L" series lens as well ( you can't expect really sharp image just from their low end zoom lens) .

 

Imager alignment is really trick stuff, in order to get best result, you might need a 6 DOF (degree of freedom, XYZ translation and rotation, yes , even the rotation around Z axis does matter, since most real world lenses are not symmetrical).

 

So for the camera with wide angle lens, the best one probably is the one come with a fixed lens ( the lens is fixed to the imager frame by glue or something else), of course, as long as the manufacturer made thoroughly alignment before sending them to customer. (Why? because the sensor itself is not absolutely parallel to it mounting surface, the variation of this parallelism is larger enough to cause some trouble, and for the lens itself, the optical axis of lens is not coincident with the axis of lens barrel either, the variation could be as larger as half degree )