Editing Optical mark recognition (section)

==Background==
[[File:LegacyStyleOMRFormSm.jpg|thumb|OMR tests form, with registration marks and drop-out colors, designed to be scanned by dedicated OMR device]]

Many [[optical reader|OMR devices]] have a [[Image scanner|scanner]] that shines a light onto a form. The device then looks at the contrasting [[reflectivity]] of the light at certain positions on the form.  It will detect the black marks because they reflect less light than the blank areas on the form.

Some OMR devices use forms that are printed on transoptic paper. The device can then measure the amount of light that passes through the paper. It will pick up any black marks on either side of the paper because they reduce the amount of light passing through.

In contrast to the dedicated OMR device, desktop OMR [[software]] allows a user to create their own forms in a word processor or computer and [[printing|print]] them on a [[Laser Printer|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]] (OCR) 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 that the OMR device will not read them 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 OMR is the use of [[pencil|#2 pencil]] (HB in Europe) bubble [[optical answer sheet]]s in multiple choice question [[Test (assessment)|examination]]s.  Students mark their answers, or other personal information, by darkening circles on a forms.  The sheet is then graded by a scanning machine.  

* In the [[United States]] and most [[European Union|European]] countries, a horizontal or vertical "tick" in a rectangular "lozenge" is the most commonly used type of OMR form; 
* The most familiar form in the United Kingdom is the UK National lottery form.{{citation needed|date=April 2018}} 

Lozenge marks represent a later technology that is easier to mark and easier to erase.  The large "bubble" marks are legacy technology from very early [[optical reader|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 [[Popularity|popular]] method of tallying votes.<ref>{{cite web|url=http://www.postgradmed.com/issues/1998/08_98/dd_aug.htm |access-date=June 13, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060613072246/http://postgradmed.com/issues/1998/08_98/dd_aug.htm |archive-date=June 13, 2006 |title=Optical mark recognition}}</ref><ref name="bookrags">{{cite book|url=http://www.bookrags.com/sciences/computerscience/optical-character-recognition-csci-02.html |title=Research Optical Character Recognition &#124; Macmillan Science Library: Computer Sciences |publisher=Bookrags.com |date=2010-11-02 |access-date=2015-07-03}}</ref><ref>{{cite web|url=http://www.aceproject.org/main/english/et/et72.htm |title=Optical Scanning Systems — |publisher=Aceproject.org |access-date=2015-07-03}}</ref><ref name="Haag">Haag, S., Cummings, M., McCubbrey, D., Pinsonnault, A., Donovan, R. (2006). Management Information Systems for the Information Age (3rd ed.). Canada: McGraw-Hill Ryerson.</ref><ref>{{cite web|url=http://www.nyu.edu/its/pubs/connect/archives/96fall/loprestistats.html |access-date=June 13, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20051110131152/http://www.nyu.edu/its/pubs/connect/archives/96fall/loprestistats.html |archive-date=November 10, 2005 |title=Statisticians' Lib: Using Scanners and OMR Software for Affordable Data Input}}</ref><ref>{{cite web|url=http://remarksoftware.com/cdn/Data-Collection-on-the-Cheap-Format.ppt|archive-url=https://web.archive.org/web/20150722033337/http://remarksoftware.com/cdn/Data-Collection-on-the-Cheap-Format.ppt|url-status=dead|archive-date=2015-07-22|format=PPT|title=Data Collection on the Cheap|date=July 2015|access-date=2015-07-21}}</ref><ref>{{cite web|url=http://www.omrsolutions.com/principia/whousesremark.php |title=Remark Office OMR, by Gravic (Principia Products), works with popular image scanners to scan surveys, tests and other plain paper forms |publisher=Omrsolutions.com |access-date=2015-07-03}}</ref><ref name="Palmer, Roger C. 1989" /><ref>{{cite web |url=http://www.tkvision.com/tech/technology.htm |title=Forms Processing Technology |publisher=Tkvision.com |access-date=2015-07-03 |archive-url=https://web.archive.org/web/20080511220150/http://www.tkvision.com/tech/technology.htm |archive-date=2008-05-11 |url-status=dead }}</ref><ref name="bookrags_a">{{cite book|url=http://www.bookrags.com/sciences/computerscience/input-devices-csci-02.html |title=Research Input Devices &#124; Macmillan Science Library: Computer Sciences |publisher=Bookrags.com |date=2010-11-02 |access-date=2015-07-03}}</ref>

OMR marks are also added to items of printed mail so folder inserter equipment can be used. The marks are added to each (normally facing/odd) 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===
[[File:SAT-Grid-In-Example.svg|thumb|350x350px|A response to an [[SAT]] math question marked on an optical answer sheet]]
An optical answer sheet or bubble sheet is a special type of [[form (document)|form]] used in multiple choice question examinations. OMR is used to detect answers. The [[Scantron Corporation]] creates many optical answer sheets, although certain uses require their own customized system.{{citation needed|date=January 2013}}

Optical answer sheets usually have a set of blank ovals or boxes that correspond to each question, often on separate sheets of paper. [[Bar code]]s 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.<ref name=HowEverythingWorks.org>{{cite web|last=Bloomfield|first=Louis A|title=Question 1529: Why do scantron-type tests only read #2 pencils? Can other pencils work?|date=29 May 2006 |url=http://howeverythingworks.org/wordpress/2006/05/29/question-1529|publisher=HowEverythingWorks.org}}</ref> As some phototubes are mostly sensitive to the blue end of the [[visible spectrum]],<ref>Mullard Technical Handbook Volume 4 Section 4:Photoemissive Cells (1960 Edition)</ref> blue pens could not be used, as blue inks reflect and [[Transmittance|transmit]] blue light. Because of this, number two pencils had to be used to fill in the bubbles—[[graphite]] is a very [[Opacity (optics)|opaque]] substance which absorbs or reflects most of the light which hits it.<ref name=HowEverythingWorks.org />

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 (this is due to the lighter marks made by higher-number pencils and the smudges from number 1 pencils). Black ink will be read, though many systems will ignore marks that are the same color the form is printed in.<ref name=HowEverythingWorks.org /> 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.
===Designing and printing===
There are specific dimensions of designing OMR sheets with 0.05 mm precision on scale. If the dimensions are not up to the precision scale, the accuracy of the OMR sheet may vary, so the sheet should be designed, printed and cut perfectly.
* Single Part – Sheets are printed on 105 gsm to 120 gsm paper on A4/Legal sheets.
* Double Part (Carbonless) – Two sheets are printed; one on 105 gsm paper and one on 60-70 gsm paper on A4 sheets. The bottom of the first sheet and the top of the second sheet are chemically treated so that the impression of the first sheet comes on the second sheet.       
* Three Part (Carbonless) – Three sheets are printed on one 105 gsm paper and the other two are printed on 60-70 gsm paper on A4 sheets. The bottom of the first sheet, the top and bottom of the second sheet, and the top of the third sheet are chemically treated so that the impression of the first sheet comes on the second and third sheets.

===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 ballot]]s in the [[Georgia (U.S. state)|Georgia]] county of [[Gwinnett County|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 [[ballot]]s to be transferred to correctly printed ones, by [[:wikt:sequester|sequestered]] workers of the [[board of elections]], under close [[observation]] by members of the [[Democrat (US)|Democrat]]ic and [[Republican (US)|Republican]] (but not [[third party (politics)|other]]) political parties, and county [[sheriff]] [[Deputy sheriff|deputies]].  The transfer, by law, could not occur until [[Election Day (politics)|election day]] (November 4).{{citation needed|date=January 2013}}