GB2076196A - Improvements in and relating to document readers - Google Patents

Abstract

A document reader is described through which a sheet of paper (24) can pass with lines of information thereon (typically answer selections by an examination candidate) transverse to the direction of movement. Each line of information includes a line of boxes (28; 30) one of which is half coloured-in to designate the selected answer. An answer is cancelled by colouring-in the whole box. Empty or fully-coloured-in boxes are disregarded. A line of photocells register with the columns of boxes (28; 30) and electrical signals obtained as a half coloured box passes a photocell are processed to a computer which compares the candidate's selection with stored correct answers and counts up the candidate's correct answers, and expresses this as a percentage of the total. The photocells may have fields of view which are small relative to the box areas so that pulses of varying width are obtained which distinguish between half and completely coloured-in boxes. Alternatively, the fields of view may be commensurate with the completely filled box area so that an amplitude variation will occur distinguishing between completely coloured-in and half coloured- in boxes. <IMAGE>

Description

SPECIFICATION Improvements in and relating to document readers Field of invention This invention concerns document readers and in particular apparatus for reading preprinted documents which have been filled in to denote the answers to examinations questions or the like. It is to be understood that although the invention will be described specifically in relation to the analysis of examination papers in the form of preprinted forms filled in by candidates, the invention is not in any way limited to this particular application but may be applied to the reading of any standardised document in which the information is located in specified over the surface of the document and is presented in particular form, colour or the like so as to be readily recognised by an automatic inspection device.

Background to the invention An increasing tendency in examination is to present each candidate with a large number of questions and a preprinted answer sheet with a series of specimen answers for each question which can be identified by colouring in a box or identified region along line on the preprinted answer sheet corresoponding to the question. In the event that a candidate makes a mistake and wishes to change his selection of the answer to another one of the answers, an area adjoining the one already filled in and denoting the unwanted answer, can be coloured in and the appropriate area corresponding to the freshly selected answer can be coloured in. The difference between a mark denoting an answer which is to be considered as opposed to an answer which is not to be considered is thus dictated by the size of the area coloured in by the candidate.

It is a simple matter for the examiner to scan each line of each examination answer sheet and determine whether the correct answer has been given by the candidate.

It is an object of the present invention to provide a device for automatically reading examination of the sheet when completed and to provide information which can be processed to a computer to analyse the results.

The invention According to the present invention a document reader comprises a housing having a document inlet and document outlet, drive means for drawing an inserted sheet of paper from the document inlet towards the document outlet at a controlled speed, first sensor means for generating an electrical signal as a leading edge of a sheet of paper is introduced into the document inlet, means for scanning linear zones of the document as the latter passes from the inlet to the outlet, means for generating electrical pulses corresponding to surface markings contained on the sheet ot paper in response to the scanning thereof, first circuit means for determining whether a pulse corresponds to a marking of a first type or a second type, second circuit means for releasing pulses corresponding to only one cf the two types of markings to a computer, along with positional information indicating which of a number of columns on the document contain the markings of the said one type, memory means associated with the computer of the document reader containing info mation for comparison with the information arising during the scanning of the document and means for determining whether or not a correct selection has been made and means for generating a first type of count pulse (indicating a correct selection if the cosnpase- son indicates such) or a count pulse of a second type (in the event that an incorrect selection has been made) and means for accu mutating the number of count pulses of at least the first type. Where the markings of the one type correspond to selections made by a candidate between possible answers to exam questions, the number correspond to the number of successes achieved by the candidate.

Conveniently means is provided for expressing the number of count pulses of the first type as a percentage of the total number of answers.

Conveniently the means for moving the document through the reader comprises a pair of rollers forming a nip between which the sheet of paper or other material can be gripped and drawn as the rollers (operating in counter rotation) roll together.

The means for scanning a linear zone of the document may comprise a plurality of photo cells located transversely to the document travel and means for causing light to fall on the document at least in the region of the line of photoelectric cells, the amount of light impinging on any one of the photo cells varying as a marking passes through the illuminated region.

The light may be transmitted through the document or reflected off the document to illuminate the document.

By moving a document at a constant speed through the reader in a direction perpendicu lar to the direction of the lines of answer boxes across a document which are to be read, so the duration of an electrical pulse from a photo cell will be dictated by the area of answer box which has been coloured-in. If the colouring-in is only partial (approximately one-half the total area of the box) so pulses will be obtained of a relatively short duration and these can be distinguished from pulses or longer duration (obtained from scanning boxes which have been completely coloured-in where the canditate has had second thoughts and cancelled an existing answer).

An initial analysis of electrical pulses arising from scanning therefore may be on a pulse width basis, and from this, pulses corresponding to selected answers only are made available for subsequent processing.

Since the document is moving in one direction perpendicular to the lines of answer boxes, the scanner may comprise a plurality of photo cells one for each colour of answer boxes and guide means is provided for aligning the document with the photo cells so that the correct column of answer boxes registers with the appropriate photo cell.

Alternatively the scanner may be in the form of a flying spot scanner in which event only a single photo cell is required and an appropriate rotating mirror or similar lightdeflecting or refracting device for displacing a light spot in a repetitive manner as a series of line scans across the document.

Pulse width discrimation whether it be carried out on the pulse obtained from a series of photo cells or from a single line scan of a flying spot scanner or the like will allow only those pulses to be stored or passed for subsequent processing having an appropriate width compatible with that of a selected answer.

Preferably the signal processing means includes further circuit means for rejecting any pulses from a line having two or more markings of the said one type. In this way a candidate entering two answers along a line will not be credited even if one of the answers if the correct one.

The invention also envisages the combination of the document reader with a computer when programmed to receive and act on electrical signals from the document reader and when connected thereto so as to receive said signals, in which the computer includes the said memory in which is stored information with which information arising during a scanning of the document is to be compared, and further includes means for printing out information processed by the computer.

In the foregoing discussion it has been assumed that the field of view of the photo cell(s) or the scanning device is small relative to the height of a box which is to be half coloured-in to designate a selected answer (or completely coloured-in to designate a selected but subsequently cancelled answer). Where this relationship is not so, and the field of view of, for example, a photocell associated with each column on the answer sheet, is approximately the same size as the area which has to be coloured-in to designate a cancelled answer, then a form of width discrimination can be performed by the scanner itself. This arises from the fact that the amplitude of the voltage excursion obtained from a photocell depends on the difference in light levels bringing about the excursion.Clearly the max- imum excursion is achieved when the light level changes from full "ON" to fully "OFF".

This is achieved when a cancelled answer is "seen" by the photocell (since for an instant the whole field of view is taken up by the coloured-in box and all the light is cut off to the cell. When no colouring-in is present in the field of view, then the light reaching the photocell is at its maximum.

On the other hand an intermediate amplitude excursion will be obtained as a halfcoloured-in box passes through the field of view of the photocell, since although the light is partly obscured by a half-coloured-in box, it is not completely extinguished. If the photo cell is operating linearly, the amplitude excur.- sion will be approximately one-half that obtained from a completely coloured-in box.

An "answer" can thus be recognised by the "scanner" as being a coloured-in box which produces an intermediate amplitude excursion of the photocell output voltage, and by providing an appropriate voltage sensing circuit which ignores voltages above and below a voltage corresponding to the said intermediate amplitude excursion, but corresponds to any voltage (other than a transient) which corresponds to the said intermediate amplitude excursion, the output of the circuit will contain a pulse for each coloured-in box which designates an answer which the candidate wishes to be considered.

The invention is not of course limited to any particular scanner of method of width discrimination and the document reader shown in the accompanying drawings may include either a pulse width discriminator circuit as previously described (where the photocells have a small field of view) or may include photocells having a larger field of view, so that width discrimination can be carried out within the scanner itself, and pulses of different amplitude may be generated as just described.

For simplicity the document reader to be described will be assumed to be of the latter type.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a document reader constructed as one embodiment of the invention, Figure 2 is a plan view of an examination answer sheet drawn up and partially completed in a manner which can be read by a document reader embodying the invention, Figure 3 is a diagrammatic side view of the salient internal features of the document reader shown in Fig. 1, Figure 4 is a plan view of the photoelectric cells and light source of the reader, and Figure 5 is a block circuit diagram of the signal processing circuits associated with the scanning photocells of the document reader.

Detailed description of drawings As shown in Fig. 1, a document reader comprises a shallow housing 10 having side walls 1 2 and 14 for defining opposite parallel edges of a tray, which tray is bridged by a transverse housing 1 6. A space exists between the underside of the transverse housing 1 6 and the flat surface of the tray denoted by reference numeral 1 8.

A document to be read is inserted under the transverse housing 1 6 in the direction of the arrow 20 and leaves the tray in the direction of the arrow 22.

A specimen examination paper answer sheet only part of the printing on which is shown, is illustrated in Fig. 2. The document which is generally designated 24 is of a standard size typically A4DIN, and is preprinted down the left-hand edge with a series of dark grey or dense black squares denoted by reference numeral 26. In line with each of the squares are printed lines of boxes, each line being in two sections 28 and 30 and each section including five individual boxes each of which is divided into an upper and lower segment as denoted by reference numeral 32 and 34 respectively.

Answers are inserted by colouring-in an upper or lower segment (but not both) of a square corresponding to a selected answer and any answer which on reflection is deemed to be incorrect, can be cancelled by colouringin the adjoining region of its square. As the document traverses the reading station below the transverse housing 16, so electrical pulses whose duration correspond to the extent to which each answer box has been coloured-in, is generated.

Fig. 3 shows the essential parts of the document reader which will normally be housed within or immediately below the transverse housing 1 6 of the embodiment shown in Fig. 1. To this end drive is provided by means of two rollers 36 and 38 mounted above and below an aperture (not shown) in the surface of the tray 1 8 below the housing 16, the two rollers forming a nip into which the leading edge of the document 40 can be pushed. Counter-rotation of the two rollers in the appropriate direction causes the document to be drawn through the nip in the direction of the outlet 22.

In front of the nip is located a light source 42 and photocell 44. As soon as the leading edge of a document passes the photocell 44, so the latter produces a pulse indicating the arrival of the leading edge of the document.

A line of photoelectric cells 46 is located beyond the nip and an associated light source 48 typically in the form of a strip light (not shown) provides illumination for the photoelectric cells 46. Passage of the paper between the cells and the light source will produce voltage excursions in the outputs of some of the photoelectric cells and these excursions can be detected and pulse width or height discriminated so as to leave electrical signals relating only to a candidate's answers.

As shown in dotted outline at 50, the photoelectric cells may be located above the document next to the light source 48 and reflectors are provided for reflecting the light from the light source 48 onto the surface of the paper, reflection of the light being dictated by the markings in the answer boxes and again introducing voltage excursions in the outputs of some of the photocells as correct or incorrect answers are received, pulse width discrimination as between one electrical excursion and another, allowing a selection to be made between marks denoting answers which are to be considered and answers which have been cancelled for consideration by the candidate.

The light source 42 and photocell 44 may be located to advantage in alignment with the column of printed marks 26 down the lefthand edge of the document. The first of these marks instead of the leading edge of the paper may be used to denote the beginning of a series of lines which are to be scanned and the results of the scanning analysed.

Referring to Fig. 4, the line of photocells 46 are shown located below the paper 40 and the light source 48 is shown above the paper.

Ten photocells are located in two lines of five at 52 and 54 to coincide in position with two sets of five columns of boxes on the document 24. A remote photocell 56 serves to align with the column of preprinted synchronising marks 26.

Signal outputs from all of the photocells are supplied to an anologue to digital converter and logic circuits for selecting between incorrectly and correctly filled-in boxes.

Referring now to Fig. 5, the outputs from the photocells 46 are supplied to pulse shaping circuits 58 to produce reliable output voltages relative to background light levels.

The output from the pulse shaping circuits 58 is supplied to an analogue to digital converter 60 and the digital output for each pulse supplied thereto is transferred to logic circuits 62 which operate in a manner to isolate digital signals relating to selected answer boxes from those which relate to cancelled answers (i.e. corrections). The output from the logic circuits is supplied zo an interface 64 adapted to provide appropriate buffering between the logic circuits 62 and a computer (not shown) adapted to count and accumulate and if required print out the results for each examination answer sheet presented to the document reader.

A feedback path along line 66 from the computer allows the interface and logic circuits to be controlled by the computer.

A power supply 68 supplies power to the various circuits as required and the computer if the latter is not self-powered Operation of the system shown in the drawings involves the following steps: 1) An examination answer sheet is inserted into the reader in the direction of arrow 20.

2) Photo cell 44 registers the presence of the paper and a voltage drop activates the drive (not shown) for the rollers 36 and 38 and initiates the light source 48. The state of the photocell 44 can be monitored by the computer to which the signals are supplied and a change of state of photocell 44 indicates the start of marking of the paper.

3) VS, V1 V2 etc. to V10 are voltages across the photocells 46. As paper passes between the light source 48 and photocells 46, so a voltage drop occurs on all the photo cells.

A voltage drop occurs across photocell 56 at each synchronization mark 26.

4) At the minimum voltage drop across photo cell 56, voltages V1 to V10 can be in one of three states either low, medium or high. The low voltage state represents a candidate's cancelled answer, the medium represents a candidate's answer and the high represents no answer. This is achieved by arranging that each photocell has a field of view commensurate with the area coloured-in to denote an inaccurate answer and consequently greater than the area of a square which is coloured-in to denote an answer to be considered. Where no colouring occurs, the voltage across the relevant photocell will remain high indicating that particular answer has been ignored by the candidate.

Voltages VS and V1 to V10 are fed into analogue converters 60.

5) When VS is low, analogue to digital converters 60 produce a binary 1 for the output corresponding to the photoelectric cell 56.

Either of the other levels of illumination (i.e.

medium or high) produces a zero in the output of the analogue to digital converter 66.

6) When any of V1 to V10 is medium, the binary 1 is generated by the analogue to digital converter 60. All other values of V1 and V10 (i.e. high or low) gives a zero.

7) The computer is programmed so as to continuously sense the state of photocell 56.

If the analogue to digital conversion indicates a binary 1 then bits 1, 2, 3, 4 and 5 form the answer to a question for example 01000. This is read and stored by the computer memory.

The answer to the next question is contained in bits 6, 7, 8, 9 and 10.

The sequence continues until the voltage drop across photo cell 44 goes high when the drive rollers are stopped and the light 48 goes out.

The computer is programmed to carry out whatever analysis' is required of it on the total information and then prints out the score against each candidate's number which was read by the reader from the head of the paper in the same way as answers to questions.

8) At the end of all marking an analysis of the examination paper may be provided by the computer acting so as to produce statistical information from the stored results.

Claims (11)

1. A document reader comprising a housing having a document inlet and a document outlet, drive means for drawing an inserted sheet from the document inlet towards the document outlet at a controlled speed, first sensor means for generating an electrical signal as a leading edge of a sheet of paper is introduced into the document inlet, means for scanning linear zones of the document as the latter passes from the inlet to the outlet, means for generating electrical pulses corre- sponding to surface markings contained on the sheet of paper in response to the scanning thereof, first circuit means for determining whether a pulse corresponds to a marking of a first type or a second type, second circuit means for releasing pulses corresponding to only one of the two types of markings to a computer, along with positional information indicating which of a number of columns on the document contains the markings of the said one type, memory means associated with the computer or the document reader containing information for comparison with the information arising during the scanning of the document and means for determining whether or not a correct selection has been made and means for generating a first type of count pulse (indicating a correct selection if the comparison indicates such) or a count pulse of a second type (in the event that an incorrect selection has been made) and means for accumulating count pulses of at least the first type.

2. A device as claimed in claim 1 in which means is provided for expressing the number of count pulses of the first type as a percentage of the total number of answers.

3. A device as claimed in claim 1 or 2 in which the means for scanning a linear zone of the document comprises a plurality of photo cells located transversely to the document travel and means for causing light to fall on the document at least in the region of the line of photoelectric cells, the amount of light impingeing on any one of the photocells vary- ing as marking passes through the illuminated region.

4. A device as claimed in claim 3 in-whieh the light is transmitted through the document.

5. A device as claimed in claim 3 in which the light is reflected off the surface of the document.

6. A device as claimed in any of claims 3 to 5 in which the field of view of each photocell is equal to twice the area which is to be filled in to provide a marking of the said type, so that pulses of differing amplitude are obtained corresponding to markings of the said first and second type.

7. A device as claimed in any of claims 3 to 5 in which the document moves at a constant speed through the reader in a direc tion perpendicular to the direction of lines of answer boxes which extend across the docu ment and which are to be read.

8. A device as claimed in claim 7 in which the field of view of each photocell is less than the area which is to be filled in to provide a marking of the said one type, so that pulses of differing duration can be obtained corre sponding to the markings of the said first and second type.

9. A device as claimed in any of claims 1 'to 8 in which guide means is provided for aligning the document with the means for scanning.

10. A device as claimed in claim 1 or 2 in which the scanner is in the form of a flying spot scanner and comprises a single photocell and rotating mirror or similar light-deflecting or refracting device for displacing a light spot in a repetitive manner as a series of line scans across the document.

11. A device as claimed in any of claims 1 to 10 comprising further circuit means for rejecting any pulses from a line having two or more markings of the said one type.

1 2. A device as claimed in claim 1 or 2 in which the means for moving the document through the reader comprises a pair of rollers forming a nip between which the sheet of paper or other material can be gripped and drawn as the rollers (operating in counter rotation) roll together.

1 3. A device as claimed in any of the preceding claims in combination with a com puter when programmed to receive and act on electrical signals therefrom, in which the com puter includes the said memory in which is stored information with which information arising during a scanning of the document is to be compared, and further includes means for printing out information processed by the computer.

1 4. A document reader constructed, ar ranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.