In whole machine vision system,industrial lenses of machine vision is the important imaging part for image capture,so it is vital whether the model selection of industrial lenses in machine vision is right or not.DZ Optic combine years of practical case,here is notes for model selection of industrial lenses from below 7 aspects:
First,customer normally preferred to consider the special requirement of machine vision lenese,such as whether added other parts(lens,mirror lens,glass) beween machine vision lens and mechanical parts,working environment of machine vision lens ect.Here need to be confirmed firstly:
1.Restrictions of installation space:size,length and specification of machine vision lens.
2.Fix camera hangs lens,such as some camera can’t hangs heavier machine vision lens.
3.Camera shooting needs movement.The shooting system might shift if faster speed because of inertance.
4.Special requirement for spectral response,for example,common glass lens absorb almost all UV-light based on UV environment.
5.Whether added light source on machine vision lens or not,according to scene environment,you need add light source with need of wideth addition.Also you can try to install point source of light if it is coaxial lens.
7.Working environment for machine vision lens.
8.Whether other special components.
Second,Ref. to precision measuring system,we need use telecentric lens.The main function of telecentric lens is to overcome effect of perspective differ,due to different distance caused inconformity phenomenon of magnification times,and it makes object detection keep the same size data while moving within a certain range.Normally,telecentric lens all fix focal length and working distance,some telecentric lens with big volume and weight more than 5 kilo.So we need know about customer’s requirement carefully,such as view field size,working distance,space restriction and moving control,then confirm lens model no./spec.If no exact demands on object imaging of common defect detecting on surface or judgement or not,we suggest choosing telecentric lens with small distortion.
Third,some vision system with special requirement,industrial lens need bigger lens,which need depth of field.For example,some detection or measurement must make industrial camera into a certain angle and require overall object with clear imaging.If detected object is not in the same plane,then we need consider lens’ depth of field.The shorter for focal length,the bigger for depth of field.The smaller for iris,the bigger for depth of field.The furhter for distance between lens and object,the bigger for depth of field.It makes focus more convenient for small iris and good ray of light,but small iris will lose fine structure of object.The larger the pixel of camera chip,the greater the depth of field.
Forth,refer to chip size of machine vision lens,each kind of machine vision is only compatible with chip,which camera is within a certain size.So,we need confirm chip size of industrial camera first when choosing lens of machine vision,it is suggested that chip’s size must be bigger than the size which matches it chip size,to ensure quality of overall image,otherwise,with the result of severe distortion and discrepancy.
Fifth,The port is C,CS,F and other bigger size port both for lens of machine vision and camera.Camera and lens are complementation,that means C port of camera only match lens with C port.
Sixth,The focal length of lens in machine vision mainly influence in field of view and working distance.It is better to confirm field of view,working distance and chip size of camera before focal length of lens in machine vision confirmed.
Seventh,The distortion of lens in machine vision is the image distortion,caused by inconformity of local magnification in view.Because of workmanship restriction,lens’ distortion is unavoidable,the better lens and the smaller of distortion.With condition of high precision measuring system,you must consider lens distortion of machine vision.These lens specification need combine practical project with model selection.