how to build an LED Intensity Inspection System using NI LabVIEW

[samriddh]

Hi,

I am having an requirement to test one LED Board (Passenger Infromation System at Railway Stations).

This board is having number of LED's mounted on it for the displaying of the text (steady or moving).

The goal of my requirement is to test the intensity of each and every LED mounted on the board before it is being released to the field.

The LED used is of 2800mcd and is yellow in color.

This can only be done using some smart intellegence like NI Vision.

The LED's are arranged in number of rows and colums on the board (say 30 rows and may be 500-600 colums).

I am new to image acquisition and is not able to identify how to build the test setup.

Can anybody guide me to any reference tutorials or study materials as how to acquire image using LabVIEW and what are the different techniques in image acquisition for the computations of the required area of interest.

Can any one help me in this regard or someone who has done the same project. I am not able to start.

Any help in thsi regard will be highly appreciated.

[samriddh]

Also the different types of NI Hardware available.

Regards,

Samriddh Sarbalhi

[Brent_R]

Hi Samriddh, We have solved numerous similar applications involving inspecting LED assemblies in car tail lights, instrument panels, LED televisions, and many other products. I'm confident NI Vision tools can address your needs as well. Acquiring images in LabVIEW is usually a straightforward affair: Install Vision Acqusition, plug in camera, open and run LabVIEW shipping example. Choosing the correct camera, optics, and setup in the first place requires some experience. Inspecting a long slender product poses some challenges and opportunities. Finding one camera with sufficient resolution to capture the entire field of view, while still seeing the smallest features can be rather expensive. It's sometimes more cost effective to place multiple lower resolution (lower cost) cameras along your part or use a motion system to move one camera to various locations. Consider also your expectations from the system. A camera based vision system can easily verify the functionality of an LED device. This often a binary decision; the LED is either on or off. Precision measurement of intensity is more challenging, since the apparent brightness of each LED can depend strongly on the angle of view. The optics and positioning of the camera are critical if you need to make uniformity measurements. If all of your LEDs are one color and/or it's not important to distinguish between colors, then a monochrome camera is usually ideal. You'll get higher effective resolution for a given number of pixels. A color camera can distinguish between various colors of LEDs, but cannot make precision spectral measurements. You couldn't measure the difference between 590nm and 595nm, for example. I would suggest downloading the Vision Development Module, Vision Builder AI, and the Vision Acquisition software and using each in eval mode to get familiar with the tools. It would also be worthwhile to speak with one of our Alliance Members for help with choosing the best components. Graftek Imaging (graftek.com) is a good starting point, as they have expertise in all aspects of vision system design. Regards, Brent

[samriddh]

Dear Brent,

Thanks for reply. You are correct that the first initial consideration regarding choosing the camera and sensor and other optics will require the importance at high priority. Here the dimension of the board is about 1236.6mm in length and we are planning to divide the entire board into identical proportions may be 1236.6/4,1236.6/6, 1236.6/8 because the camera will not be able to acquire the image of the whole board and if it acquires, the measuremet and analysis will be very difficult. Whenever the image is acquired for one portion, the board will be moved physically by an auto arrangement which will also gets its trigger from LabVIEW System and will carry the next portion of the LED board in front of the camera. The distance between two LED's on the board (horizontally or vertically) is 10mm from both centres on which the LED's are soldered on the board. The LED is 6mm in diameter. So after divinding the board into same proportions i am able to finalise my Field of View. The LED's are arranged in Rows and Columns on the board as 16 rows and 128 columns i.e. 2048 number of LED's. With this data i can also select the resolution of the camera. Kindly guide me to some of the numericals involved into the selection of the right optics for this kind of vision setup and the type of lighting because outer world light will also be coming into the picture. In order to avoid the mixture of outer lighting with the acquired image we are planning to put the LED Board and the camera in a fixed enclosure and the distance between the camera and the LED board will be 100 mm maximum. The color of the LED's are same/identical as yellow and the intensity of each LED is 2800 mcd (millicandela). Where exactly i am having the confusion is whether to go for PXI based system or PCI/PCIe based system as PCI/PCIe based system may not be so accurate as far as the image acquisition or measurements are concerned. We are considering the option of color image also so that the same hardware and software will get used where the color recognition kind of requirement comes into the picture. At this point of time the color is identical so we are also planning a monochromatic camera.

If you are having some of the initial considerations to be made for the selection of proper hardware like camera lens, FOV, Pixel to real world ratio, resolution, image frame size like 1024*640 etc, that will help me alot.

KIndly suggest some ideas as this is our goal which is to be achieved.

Thanks,

Samriddh Sarbalhi

9550871810

India.

[samriddh]

Also in the software side we can have odd or even number switching on the LED Columns. Mean suppose if the FOV is 1236.6/6 = 206.1mm, and in this 206.1 mm portion if 10 columns comes in front of the camera we can also switch on the LED's in the pattern like 2nd - 4th - 6th - 8th - 10 column or any combination so that the light intensity of LED's itself will not effect the image.

Its programmable. This is just an example.

Thanks & Regards,

Samriddh Sarbalhi

09550871810

INDIA.