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What is OMR Technology ?

Rohit Gupta , OMR Consultant , IndiaOutsources mail me at rohit@indiaoutsources.com.

OMR refers to the technique of converting a handwritten marks into an ASCII value. The Mark is created by filling a circle or a box on a pre-printed form .

An Optical Mark Reader (OMR) is simply a machine that takes sheet paper and records whether marks appear on the paper in predefined areas. If you have ever filled in an application form with bubbles then you have filled in a form that is read by an OMR machine.

OMR machines are not scanners in the sense that they do not form an image of the sheets that pass through. Instead, the OMR device simply detects whether predefined areas are blank or have been marked. The fact that OMRs don't form an image differentiates them from desktop scanners that are often used by departments to mark MCQ examinations.

OMRs have the capacity to read sheets at a very high rate. Now new high Hybrid Scanners are also available from Scantron which can read images simultaneously with OMR

The model we have can read over 7,000 per hour.

The presence or absence of a Mark in a specific location is then converted into a value such as a selection in a multi- choicequestion, the selection of one item in a list of several, or even to code a specific numeric or alphanumeric value, such as a date using six columns of 10 boxes or name with 26 columns etc

Thus, if a Mark by itself can only generate a binary choice (presence or absence), the combination of several marks arranged on a form can provide intelligent answers to questions and be used as a fast and accurate replacement to data entry in many applications. Basically an OMR Reader is only intelligent to accurately give the postion of the marks , interpretation of marks is an important aspect and more than often known as Template Creation

Optical marks recognition is traditionally performed using Reflective Light Method where a beam of light is reflected on a sheet with marks. (Sekonic Optical Mark Readers , a low priced Japanese Readers are very special )Special forms are created using Timing Marks and color drop-out (depends what reading head you uses , Visible or Infra-red) and are usually referred as Scantron or Sekonic Forms from the name of the vendors that sell these systems. OMR Solutions can assist you in locating a vendor for such a product. Please Contact us for details

On the other hand, techniques used to process marks from a scanned document raised different issues such as background color, densityof marks, coding scheme, timing marks etc.

Software based solutions: the issue of registration

Marks recognition can be achieved with specially designed forms or free forms. The problem of free forms (without timing or registrationmarks) is accuracy and control. If the marks are too close and are filled slightly inaccurately, the error rate can be extremely high. In addition, template setting is longer and more complex.It is possible to read the form without timing marks, howeve rprocessing time is usually longer and forms set-up more complex

The Main Product Line that was developed was from Principia Products , Remark Office OMR which has now released its latest version of 6.0.0

OMR Forms using Timing Marks

Timing marks are short black lines printed at the edge of the form, one mark per line. The timing marks provide for an accurate position of the data. This technique is used by all hardware base solutions (Scantron/Sekonic) Example of OMR form.

When timing marks based techniques are used, the position of the mark is extremely accurate and density check can be performed on the area of the grid quickly and accurately. Density check is done by using a fixed or relative threshold.

Since marks can be printed very close to each other, it is possible to create a grid of 10x10 or 20x26 or 8 x6 that can be used to code a number or a name etc . Usually a character is printed inside the bubble which requires that the form be printed in a drop-out color for the scanner (Visible red for pencil reading ). White light scanners do notwork very well in these application because the background appearsand makes the threshold decision between a filled mark and anempty mark difficult to decide.

This technique, however accurate and fast is not appropriate for other types of marks such as check boxes. Here simple density checks often generate invalid results because the difference betweenthe density of a filled mark and that of an empty mark is marginal.

In such applications, OMR Solutions offers a complete product called Genesis to process forms with timing marks. The product is currently only sold as part of a scanning station that includes a OMR Solutions scanner because this technique is very scanner sensitive.

AutoScan Capture OMR for forms processing applications: density checkor ICR
Density Checks Technique:
Density check can also be used in forms processing applicationthat do not use timing marks and high density. This method isonly acceptable for bubble marks since density checks is doneon a small area inside the bubble.

Check marks do not provide sufficient density to make accuratedecisions.

Well filled bubbles are very accurate providing the forms is correctlyregistered.

ICR Based Technique:

OMR Solutions also uses an ICR based technique and trains the recognitionsoftware using neural network technique to recognize a limitedfont set of filled marks and empty marks. This provides for awide variety of mark-reading capabilities from single check-markto the row and column marks.

The marks are analyzed by the software and a Yes or No value isreturned to the data record for the field defined.

The software is however subject to the same limitations that applyto OCR. There is a requirement for minimum distance between marksand "quiet" zones above and below the character. Itis also mandatory that the background appears in the image otherwisethe software cannot detect an empty mark and recognize it as character.(The software will return a space).

This technique require a good understanding of OCR and segmentationissue. Since the software uses an OCR like technique, it is subjectto the same kind of failure (usually touching or breaking characters).

OMR Solutions has mastered both technologies (density base and ICRbased), and sells a developer's tool kit that contain page registrationand marks recognition engines. Example of Check Mark form.

The OMR Solutions OMR engine available in Image Basic (Diamond Head)software is designed for check marks in forms applications anduses the trainable technique ICR, it assumes that the page iscorrectly registered and deskewed.

Integrators who wish to support marks recognition in their application can purchase the VisionTools product