Hi Sheila,
I have an issue with at the moment.
Our inspectors prefer to use a bench magnifier rather than the Vision Mantis available. The Mantis has a X4 lens and, although the manufacturers of the magnifier claim X2.5 its actual mag. is X1.5. Consequently defects can and are missed.
I also have a simple X7 to X45 stereozoom on my Process Bench but this is a bit too much for general inspection, mainly because the field of view is limited.
I am not sure that any single lens bench magnifier will ever achieve x4. The edge distortion will reach almost to the centre. You can easily check the magnification by putting a ruler or similar under the equipment where you can also see it by naked eye by glancing downwards. Compare the magnified image with the real thing, does one look four times as big as the other?
I suspect that some manufacturers get away with their claims by stating the area magnification not the linear magnification. The first is the square of the second.
Hope this helps.
Regards
Eric Dawson

> -----Original Message-----
> From: Sheila Akins [SMTP:[log in to unmask]]
> Sent: Thursday, November 27, 2003 11:22
> To:   [log in to unmask]
> Subject:      [TN] 4X magnification
> 
> Technetters,
> Under the Visual Examination para in IPC-600, IPC-6012, & IPC-6013 reference is made to "1.75x magnification (approx. 3 diopters)". Do any IPC or other Internationally recognized standards list the formula for determining magnification or a table of magnification vs. diopter? When I talked to my vendors and distributors about this topic almost all of them had a different theory and or method for calculating magnification. 
> 
> Under the Visual Examination para in IPC-610, as the size of the feature being inspected is reduced in size, the magnification increases. One of the magnification powers called out is 4X. Our stereo-microscopes start at 7X or 10X and we do not want to use pocket comparators or jewelers eye loops to perform inspection operations. Does anyone know where 4X halo lamps can be purchased? 
> 
> Does anyone know of a way to confirm the magnification of a standard Halo lamp? 
> 
> Vendor references can be sent to
> [log in to unmask]
> 
> Any and all assitance with this issue is greatly appreciated.
> 
> Sheila Akins
> 
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Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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