Optical mark recognition


Optical mark recognition is the process of capturing human-marked data from document forms such as surveys and tests. They are used to read questionnaires, multiple choice examination paper in the form of lines or shaded areas.

OMR background

Many traditional OMR devices work with a dedicated scanner device that shines a beam of light onto the form paper. The contrasting reflectivity at predetermined positions on a page is then used to detect these marked areas because they reflect less light than the blank areas of the paper.
Some OMR devices use forms that are preprinted onto "transoptic" paper and measure the amount of light which passes through the paper; thus a mark on either side of the paper will reduce the amount of light passing through the paper.
In contrast to the dedicated OMR device, desktop OMR software allows a user to create their own forms in a word processor and print them on a laser printer. The OMR software then works with a common desktop image scanner with a document feeder to process the forms once filled out.
OMR is generally distinguished from optical character recognition by the fact that a complicated pattern recognition engine is not required. That is, the marks are constructed in such a way that there is little chance of not reading the marks correctly. This does require the image to have high contrast and an easily recognizable or irrelevant shape. A related field to OMR and OCR is the recognition of barcodes, such as the UPC bar code found on product packaging.
One of the most familiar applications of optical mark recognition is the use of #2 pencil bubble optical answer sheets in multiple choice question examinations. Students mark their answers, or other personal information, by darkening circles marked on a pre-printed sheet. Afterwards the sheet is automatically graded by a scanning machine. In the United States and most European countries, a horizontal or vertical "tick" in a rectangular "lozenge" is the most commonly used type of OMR form; the most familiar application in the United Kingdom is the UK National lottery form. Lozenge marks are a later technology and have the advantage of being easier to mark and easier to erase. The large "bubble" marks are legacy technology from very early OMR machines that were so insensitive a large mark was required for reliability. In most Asian countries, a special marker is used to fill in an optical answer sheet. Students, likewise, mark answers or other information by darkening circles marked on a pre-printed sheet. Then the sheet is automatically graded by a scanning machine.
Many of today's OMR applications involve people filling in specialized forms. These forms are optimized for computer scanning, with careful registration in the printing, and careful design so that ambiguity is reduced to the minimum possible. Due to its extremely low error rate, low cost and ease-of-use, OMR is a popular method of tallying votes.
OMR marks are also added to items of physical mail so folder inserter equipment can be used. The marks are added to each page of a mail document and consist of a sequence of black dashes that folder inserter equipment scans in order to determine when the mail should be folded then inserted in an envelope.

Optical answer sheet

An optical answer sheet or bubble sheet is a special type of form used in multiple choice question examinations. Optical mark recognition is used to detect answers. The most well known company in the United States involved with optical answer sheets is the Scantron Corporation, although certain uses require their own customized system.
Optical answer sheets usually have a set of blank ovals or boxes that correspond to each question, often on separate sheets of paper. Bar codes may mark the sheet for automatic processing, and each series of ovals filled will return a certain value when read. In this way students' answers can be digitally recorded, or identity given.

Reading

The first optical answer sheets were read by shining a light through the sheet and measuring how much of the light was blocked using phototubes on the opposite side. As some phototubes are mostly sensitive to the blue end of the visible spectrum, blue pens could not be used, as blue inks reflect and transmit blue light. Because of this, number two pencils had to be used to fill in the bubbles—graphite is a very opaque substance which absorbs or reflects most of the light which hits it.
Modern optical answer sheets are read based on reflected light, measuring lightness and darkness. They do not need to be filled in with a number two pencil, though these are recommended over other types. Black ink will be read, though many systems will ignore marks that are the same color the form is printed in. This also allows optical answer sheets to be double-sided because marks made on the opposite side will not interfere with reflectance readings as much as with opacity readings.
Most systems accommodate for human error in filling in ovals imprecisely—as long as they do not stray into the other ovals and the oval is almost filled, the scanner will detect it as filled in.

Errors

It is possible for optical answer sheets to be printed incorrectly, such that all ovals will be read as filled. This occurs if the outline of the ovals is too thick, or is irregular. During the 2008 U.S. presidential election, this occurred with over 19,000 absentee ballots in the Georgia county of Gwinnett, and was discovered after around 10,000 had already been returned. The slight difference was not apparent to the naked eye, and was not detected until a test run was made in late October. This required all ballots to be transferred to correctly printed ones, by :wikt:sequester|sequestered workers of the board of elections, under close observation by members of the Democratic and Republican political parties, and county sheriff deputies. The transfer, by law, could not occur until election day.g

OMR software

OMR software is a computer software application that makes OMR possible on a desktop computer by using an Image scanner to process surveys, tests, attendance sheets, checklists, and other plain-paper forms printed on a laser printer.
OMR software is used to capture data from OMR sheets. While data capturing scanning devices focus on many factors like thickness of paper dimensions of OMR sheet and designing pattern.

Commercial OMR software

One of the first OMR software packages that used images from common image scanners was Remark Office OMR, made by Gravic, Inc.. Remark Office OMR 1.0 was released in 1991.
The need for OMR software originated because early optical mark recognition systems used dedicated scanners and special pre-printed forms with drop-out colors and registration marks. Such forms typically cost US$0.10 to $0.19 a page. In contrast, OMR software users design their own mark-sense forms with a word processor or built-in form editor, print them locally on a printer, and can save thousands of dollars on large numbers of forms.
Identifying optical marks within a form, such as for processing census forms, has been offered by many forms-processing companies since the late 1980s. Mostly this is based on a bitonal image and pixel count with minimum and maximum pixel counts to eliminate extraneous marks, such as those erased with a dirty eraser that when converted into a black-and-white image can look like a legitimate mark. So this method can cause problems when a user changes his mind, and so some products started to use grayscale to better identify the intent of the marker—internally scantron and NCS scanners used grayscale.
OMR software is also used for adding OMR marks to mail documents so they can be scanned by folder inserter equipment. An example of OMR software is Mail Markup from UK developer Funasset Limited. This software allows the user to configure and select an OMR sequence then apply the OMR marks to mail documents prior to printing.

OMR Development Libraries

Open source OMR software

Some OMR software developed and distributed under free or open source licenses:
NameCreatorNotesLatest stable versionCost Software licenseOpen source
FormScannerAlberto Borsettamultiplatform Java application, supports custom forms2017-06-07
queXFAustralian Consortium for Social and Political Research Incorporatedcan be used alone or in conjunction with surveys exported from LimeSurvey2019-05-13
Udai OMRAaditeshwar Seth2007
Shared Questionnaire System 2016
Auto Multiple ChoiceAlexis Bienvenüefor class tests, with LaTeX formatting2018-12-29
Moodle Quiz OMRonline support for offline quizzes conducted on OMR sheets
SDAPS: Scripts for data acquisition with paper-based surveysBenjamin Bergfor surveys, supports LaTeX and ODT formatted documents2019-06-02
OMR Mark EngineC# implementation supports bulk scanning with custom forms2015
G'n'T EvalStefan Breunig2013

History

Optical mark recognition is the scanning of paper to detect the presence or absence of a mark in a predetermined position. Optical mark recognition has evolved from several other technologies. In the early 19th century and 20th century patents were given for machines that would aid the blind.
OMR is now used as an input device for data entry. Two early forms of OMR are paper tape and punch cards which use actual holes punched into the medium instead of pencil filled circles on the medium. Paper tape was used as early as 1857 as an input device for telegraph. Punch cards were created in 1890 and were used as input devices for computers. The use of punch cards declined greatly in the early 1970s with the introduction of personal computers. With modern OMR, where the presence of a pencil filled in bubble is recognized, the recognition is done via an optical scanner.
The first mark sense scanner was the IBM 805 Test Scoring Machine; this read marks by sensing the electrical conductivity of graphite pencil lead using pairs of wire brushes that scanned the page. In the 1930s, Richard Warren at IBM experimented with optical mark sense systems for test scoring, as documented in US Patents 2,150,256 and 2,010,653. The first successful optical mark-sense scanner was developed by Everett Franklin Lindquist as documented in US Patent 3,050,248. Lindquist had developed numerous standardized educational tests, and needed a better test scoring machine than the then-standard IBM 805. The rights to Lindquist's patents were held by the Measurement Research Center until 1968, when the University of Iowa sold the operation to Westinghouse Corporation.
During the same period, IBM also developed a successful optical mark-sense test-scoring machine, as documented in US Patent 2,944,734. IBM commercialized this as the IBM 1230 Optical mark scoring reader in 1962. This and a variety of related machines allowed IBM to migrate a wide variety of applications developed for its mark sense machines to the new optical technology. These applications included a variety of inventory management and trouble reporting forms, most of which had the dimensions of a standard punched card.
While the other players in the educational testing arena focused on selling scanning services, Scantron Corporation, founded in 1972, had a different model; it would distribute inexpensive scanners to schools and make profits from selling the test forms. As a result, many people came to think of all mark-sense forms as scantron forms. Scantron operates as a subsidiary of M&F Worldwide and provides testing and assessment systems and services and data collection and analysis services to educational institutions, businesses and government.
In 1983, Westinghouse Learning Corporation was acquired by National Computer Systems. In 2000, NCS was acquired by Pearson Education, where the OMR technology formed the core of Pearson's Data Management group. In February 2008, M&F Worldwide purchased the Data Management group from Pearson; the group is now part of the Scantron brand.
OMR has been used in many situations as mentioned below. The use of OMR in inventory systems was a transition between punch cards and bar codes and is not used as much for this purpose. OMR is still used extensively for surveys and testing though.

Usage

The use of OMR is not limited to schools or data collection agencies; many businesses and health care agencies use OMR to streamline their data input processes and reduce input error. OMR, OCR, and ICR technologies all provide a means of data collection from paper forms. OMR may also be done using an OMR scanner or an imaging scanner.

Applications

There are many other applications for OMR, for examples:
OMR has different fields to provide the format the questioner desires. These fields include:
In the past and presently, some OMR systems require special paper, special ink and a special input reader. This restricts the types of questions that can be asked and does not allow for much variability when the form is being input. Progress in OMR now allows users to create and print their own forms and use a scanner to read the information. The user is able to arrange questions in a format that suits their needs while still being able to easily input the data. OMR systems approach one hundred percent accuracy and only take 5 milliseconds on average to recognize marks. Users can use squares, circles, ellipses and hexagons for the mark zone. The software can then be set to recognize filled in bubbles, crosses or check marks.
OMR can also be used for personal use. There are all-in-one printers in the market that will print the photos the user selects by filling in the bubbles for size and paper selection on an index sheet that has been printed. Once the sheet has been filled in, the individual places the sheet on the scanner to be scanned and the printer will print the photos according to the marks that were indicated.

Disadvantages

There are also some disadvantages and limitations to OMR. If the user wants to gather large amounts of text, then OMR complicates the data collection. There is also the possibility of missing data in the scanning process, and incorrectly or unnumbered pages can lead to their being scanned in the wrong order. Also, unless safeguards are in place, a page could be rescanned, providing duplicate data and skewing the data.
As a result of the widespread adoption and ease of use of OMR, standardized examinations can consist primarily of multiple-choice questions, changing the nature of what is being tested.