FR2493569A1 - Microcomputer print character reader for blind user - has supported scanner forming character image on photosensitive matrix for processing and transcription into Braille - Google Patents

Abstract

The device enables blind people to understand print by using an optical system in the form of a micro camera for forming an image of an object character prevented to a matrix of photosensors. The device then generates a representative set of electrical signals. The signals are digital codes from which are extracted signals characterising the image for vertically centring the image and signals identifying the dimensions of characters. A circuit verifies that the signals extracted represent a single character and warns the user to move the camera if this is not the case. The character is then identified and indicated to the user by, for example, a cooperating tape recorder or braille character indicator.

Description

READING METHOD FOR THE BLIND AND DEVICE
FOR THE IMPLEMENTATION OF THIS PROCESS
The present invention relates to a reading method for the blind and to the device for implementing this method. The situation of the blind vis-à-vis their handicap has been significantly changed by technical developments.

Communication with the world is facilitated by radio, telephone and magnetic or other recordings. However, visual reading is still a fundamental means of accessing a great deal of information concerning everyday life: invoices, bank statements, administrative mail, labels, instructions for use, newspapers and books. These texts are generally read by a third party.

 We know a certain number of devices whose purpose is to give greater independence to the blind by allowing them to read certain texts. Thus there are editions in Braille whose principle consists in representing the characters by a certain number of points in relief. There are also known apparatuses for recording Braille characters on cassettes by means of special keys. The reading is done on a tactile bar comprising 12 to 48 Braille characters depending on the manufacturer. The disadvantage of these devices is mainly that they do not allow reading of current texts.

 We also know the Kurzweil machine which performs the capture, interpretation and audio transcription of printed texts. The sheet to be read is placed on a glass plate, the positioning of the camera being done automatically by a computer. The characters are recognized by program and the text is reproduced by voice thanks to a synthesizer. This device gives a certain independence to the blind but its price and its bulk make it practically inaccessible to individuals.

 There is also known a device sold SGUS not "Optacon" comprising a mini-camera which is moved over the text to be studied. The shape of the characters is reproduced in relief on a table comprising 6 x 24 vibrating points on which the blind person places his finger. This device requires a fairly long apprenticeship because the interpretation of the forms is particularly difficult, especially for the blind from birth accustomed to Braille.

The object of the present invention is to remedy these drawbacks and to provide a reading method for the blind and a device for implementing this method, which are simple and inexpensive.
Another objective of the present invention is to provide a portable device, of great flexibility of use.

 Another object of the present invention is to provide a direct reading device with simultaneous translation of multifont characters into Braille characters allowing a reading speed close to the reading speed in Braille.

An essential characteristic of the reading method according to the present invention resides in the fact that
an optical system is applied to the support, on which the characters to be read are written, opening a surface slightly larger than that of a character or a small number of characters, said optical system being maintained by carrier means having a front face disposed in abutment on the support, the optical system being adapted to obtain a clear image of an object situated substantially in the plane of the front face,
the carrier means of the optical system are moved on the support in order to explore the characters inscribed there,
an image of the character or of the small number of characters covered by it is formed for each position of the optical system on a matrix of photosensitive elements in order to obtain electrical signals representative of this image,
these signals are processed with a view to delivering signals for controlling transcription means in a system accessible to the blind,
and transcribing said signals using said transcription means.

 Another essential characteristic of the reading method according to the invention lies in the fact that, during the movement of the carrying means of the optical system, signals are generated for vertical centering of the character being entered and, from these signals, warning signals accessible to the blind and corresponding to a correction to be made.

An essential characteristic of the device according to the present invention lies in the fact that it comprises
an optical system arranged on carrier means having a front face of support and adapted to form a clear image, of an object located substantially in the plane of the front face, on a matrix of photosensitive elements, in order to obtain electrical signals representative of this image,
means for coding these signals in digital form,
means adapted to extract, from among all of said signals, on the one hand signals characteristic of the positioning of the character or of the small number of characters with a view to generating the vertical centering signals, on the other hand signals characteristic of the dimensions of each character,
means adapted to check whether the extracted signals correspond to a character fully captured and positioned within a determined horizontal interval,
means adapted to warn the blind that it is necessary to correct the displacement of the carrying means of the optical system,
means suitable for carrying out recognition tests on the characteristic signals of each character and for supplying control signals with a view to transcription in a system accessible to the blind,
and means for transcribing these signals in a system accessible to the blind.

Other characteristics of the reading method and of the device for implementing this method according to the present invention will be highlighted by the description below with reference to the appended drawing, given by way of nonlimiting example and in which
FIG. 1 is a block diagram showing the principle of the invention,
FIG. 2 is an enlarged view of the micro-camera according to the invention,
and Figure 3 is a view of an example letter illustrating the character recognition method.

 In FIG. 1, we can see a micro-camera 1 applied to a text support to read, here a dropper bottle 2. It is obvious that this support is indicated purely by way of non-limiting indication, this support being able to have any shape and all dimensions. The micro-camera 1 is connected by a cable 3 to an apparatus LI comprising specialized processors 5 for servo-control and pre-processing, a memory 6, a processing unit 7 and a processor 8 for transcription. This device 4 can be connected to various peripherals such as a digicassette 9 with a touch display with Braille characters or a sound transmitter 10 from Morse or also a display device 11 allowing a light to follow the reading of the blind.

 The micro-camera 2, FIG. 2, comprises a housing 12 of reduced size. By way of nonlimiting example, a parallelepipedic box of 72 x 36 x 26 mm was used.

The interior walls of this unit are painted matt black to eliminate stray reflections. In the housing 12 is arranged an optical system 13 with adjustable magnification comprising an achromatic doublet of low focal length. A diaphragm 14 makes it possible to increase the depth of field. One of the faces of the box is provided with a window 15 whose surface is slightly greater than that of a character or a small number of medium characters. A lighting system 16, comprising two small incandescent lamps, is necessary for good capture. A mirror 17, inclined at 45, or a prism makes it possible to obtain uniform illumination over the entire window 15. Behind the optical system 13 is placed a matrix of photosensitive elements 18, arranged inside a dark room 19 on a support 20. The optical system assembly 13 matrix of photosensitive elements 18 is mounted on a mobile platform 21 which, when it is moved using means not shown, makes it possible to adjust the magnification. The matrix of photosensitive elements 18, of a current model, defines a frame composed of points distributed in rows and columns. It may also be useful to place a filter absorbing infrared radiation between the optical system 13 and the matrix of photosensitive elements 18 in order to adapt the sensitivity of the matrix to the contrast between the characters and their support. of the housing 12 is also arranged a printed circuit on a plate 22 carrying the components Aes control circuits of the matrix of photosensitive elements 18, in particular six clocks whose role will be defined later. The housing 12 also contains two vibrators 23 whose vibrating pads are flush with one of the faces of the housing other than the face provided with the window 15. These vibrators constitute a signaling device whose role will be defined below.

 The blind person moves the micro-camera on the support. Through the window 15, a character or a small number of characters is captured by the optical system 13 which forms, on the matrix of photosensitive elements 13, an image of this or these characters. The optical system 13 is calculated to provide a sharp image without the need for focusing. However, given the disparity in font size, it is sometimes necessary to adjust the magnification. By way of nonlimiting example, a clear image has been obtained in a magnification range of between 0.3 and 1.

 Each photosensitive element of the matrix 18 delivers an electrical signal which must be coded in order to make it compatible with a digital system. For this, a Schmitt trigger is used which is arranged at the input of module 5 of the servo and preprocessing processors. The role of this trigger is to distinguish two classes of points in an image: white points, coded 0 and black points coded 1.

In order to be able to take into account the possibility of a poor contrast between the characters and the support, for example when the latter is colored, a Schmitt trigger threshold is manually adjustable by the operator.

 The electrical signals representative of the images drilled on the matrix of photosensitive elements 18 are generated by sequentially exploring the photosensitive elements to supply, at given frequency, signal trains each representative of an image.

 The coded signals are transmitted to a processor in which the grouping of the bits corresponding to the pixels of each image is carried out by a shift register coupled to a counter reset at the start of each line of the frame by one of the six clocks mentioned above. above. The synchronization of the frame transfers is thus obtained. A sampling signal, supplied by the miePoacaméra, allows valid information to be taken into account. A second clock synchronizes this signal. The coded signals are then introduced into a direct access memory 6 without slowing down the processor. We use two image buffers in memory: one contains the current frame the other, the validated frame which will be analyzed by the recognition module 7. After identifying a character, these buffers are swapped in order to obtain two processes in parallel : search for a valid frame and identify a character.

 To perform the frame analysis, we first look for the presence of a low press, i.e. a line below which all the dots are white.

If this line is one of the first lines at the bottom of the image, it means that the micro-camera is too high in relation to the text. If, on the contrary, this line is one of the upper lines of the image, this means that the microcamera is too low compared to the text. In each of these cases, a vertical centering signal is then transmitted to one of the vibrators 23 signaling to the blind that he must make a displacement correction. We then look for the presence of a left support, that is to say a column to the left of which there are only white dots. We then framed the character and the frame is selected in one of the image buffers.

 To prevent a character from being taken into account several times, validation signals are generated for each image provided that there is a signal for selecting the image in question and in no signal to select the previous image. Thus, each selected image can only be validated once.

The identification of the character is carried out by the following method: in FIG. 3, we see a character represented by its frame. We will identify this character by three lines H1, H2, H and three columns VI, V2, V3, chosen
their / caracteristi ne pour1situatiory. successively traverses rows V1, V2, V3,
H1, H2 and H3 of the image. The direction of travel of a column is from bottom to top and that of a line from left to right. For each row traversed, the number of white dots and black dots successively encountered is memorized. At the end of the scan, we therefore know for each row and for each column scanned the number of white areas and black areas as well as the number of points in each of these areas. We thus obtain a large number of characteristic data for each character . These data allow addressing of the registers in memory in which a real dictionary of characters is stored.

 The identification module 7 then delivers signals to the transcription module 8. The latter comprises one or more processors as required. The role of these processors is to convert the characteristic character signals into signals accessible to the blind. By way of nonlimiting example, two types of outputs will be described: a sound output emitting Morse signals and a tactile output with a Braille character display. It is obvious that other outputs can be envisaged, such as for example voice synthesizers, without departing from the scope of the present invention.

 The Morse processor essentially comprises a UART integrated circuit to perform the deserialization of the information supplied as input and a REPROM read-only memory allowing the Morse code to be obtained from the character identification code.

 The Braille processor controls the touchpad via a synchronous serial link. The character identification code is transmitted by a serial asynchronous interface. A simple program serializes this information.

 It may also be advantageous to be able to connect to the device a display device allowing a light to follow the reading of the blind. This is particularly useful during the familiarization phase with the device, in particular for teaching the blind to react correctly to the vertical character framing signals, to correctly adjust the magnification of the optics according to the size of the characters. and to suitably adjust the threshold of the Schmitt trigger as a function of the contrast existing between the characters and the support.

 It is obvious that the above description is given by way of nonlimiting example. Thus instead of the vibrators 22, one could use a color system emitting a sound of frequency F1 when the micro-camera 1 drifts down, a sound of frequency F2 when the microcamera drifts up and a sound of frequency F3 when the micro-camera performs an incorrect tracking.

 The operation of the vibrators is as follows: the upper stud vibrates when the micro-camera tends to go up, the lower stud vibrates when the micro-camera tends to descend and the two studs vibrate simultaneously when the tracking is incorrect.

 Finally, other modifications could be made because the invention is not limited to the terms of the preceding description, but on the contrary includes all the variants thereof.

Claims (18)

 1 / - Method for reading characters written on a medium, comprising the analysis of these characters and their transcription in a system accessible to the blind, for example sound or touch, characterized in that it consists of.  - Apply to the support an optical system (1) covering a surface slightly larger than that of a character or a small number of medium characters, said optical system (1) being arranged on carrier means (12) having a face front disposed in abutment on the support, and being adapted to obtain a clear image of an object situated substantially in the plane of the front face,  - move the carrier means (12) of the optical system (1) on the support in order to explore the characters inscribed there,  - forming, for each position of the optical system (1), an image of the character or of the small number of characters covered by it on a matrix of photosensitive elements (18) in order to obtain electrical signals representative of this image ,  - processing these signals with a view to delivering signals for controlling transcription means (9, 10) in a system accessible to the blind  - And transcribe said signals using said transcription means (9, 10).  21 - Reading method according to claim 1, characterized in that, during the displacement of the carrier means (12) of the optical system (1), signals are generated for vertical centering of the character being entered and, from these vertical centering signals, warning signals accessible to the blind, for example audible or tactile, corresponding to a correction to be made.  31 - Reading method according to claim 2, characterized in that the warning signals are modulated in order to allow an appropriate correction to be made ensuring complete entry of the character or of the small number of characters.  4 / - Reading method according to claim 1, for reading characters of different sizes, characterized in that Sue, beforehand, an adjustment is made in order to adjust the magnification of the optical system (13) according to the size of characters to read.  5 / - Reading method according to one of claims 1, 2, 3 or ", characterized in that the electrical signals representative of the images formed on the matrix of photosensitive elements are generated by sequentially exploring the photosensitive elements of said matrix for form at given frequency signal trains each representative of an image.  6 / - Reading method according to claim 2, characterized in that the processing of the signals con.- takes a first phase consisting of  code in digital form the signals representative of each image formed, this image being broken down into points distributed in rows and columns,  extracting from all of said signals, on the one hand, signals characteristic of the positioning of the character or of the small number of characters with a view to generating the vertical centering signals, on the other hand, signals characteristic of the dimensions of the character,  memorize signals representative of the image in order to carry out the recognition of each character.  7 / - Reading method according to claim 6, characterized in that it comprises a second processing phase consisting  to check whether the extracted signals correspond to a fully entered character,  if so, to check If the extracted signals correspond to a character positioned within a determined horizontal interval,  if so, to carry out recognition tests an o e on characteristic signals of the character in order to recommend the means of transcription (9, 10) in a system accessible to the blind.  8 / - Reading method according to claim 7, characterized in that, to check whether the extracted signals correspond to a fully entered character, the lowest line (or the highest line) below is searched in the image (or above) of which there are only white dots, the vertical centering signals being generated when this line is situated outside an area defined by an upper threshold and a lower threshold.  9 / - Reading method according to claim 7, characterized in that., To check whether the extracted signals correspond to a character positioned in a determined horizontal interval, the first column is looked for in the image on the left (or right) of which there are only white dots, selection signals being generated when this column is located in an area defined by two determined thresholds.  10 / - Reading method according to claims 5 and 9 taken together, characterized in that one generates a validation signal of each image for the recognition of the positioned character, said signal being generated on the double condition that the we are in the presence of a signal for selecting the image considered and in the absence of a signal for selecting the previous image, in order to take each character into account only once.  11 - Reading method according to claim 7, characterized in that, for the recognition of each character  . we successively scan rows and columns chosen for their characteristic situation,  the signals corresponding to the white points and to the black points successively encountered are memorized in order to determine the white zones and the black zones of each row and of each column scanned, as well as the number of points constituting these white and black zones,  one or more character recognition tests are carried out by addressing the characteristic signals of this character in the registers containing all the characteristic data of all the characters, each test carried out determining the address of the next test as a function of the result of this test, view of providing the control signals of the transcription means (9, 10) accessible to the blind.  12 / - Reading method according to claim 11, characterized in that one chooses three rows and three scanning columns, the position of the rows and outer columns being determined in order to eliminate burrs and possible serifs of the characters .  13 / - Reading method according to claim 9, characterized in that a buffer memory is used to store all of the coded signals corresponding to the image of the character or of the small number of characters before the generation of the validation signals , and a second buffer memory for storing the signals extracted after validation in order to carry out the recognition of each character.  14 / - Reading method according to claim 13, characterized in that the role of these buffer memories is changed after recognition of each character, with a view to simultaneously capturing a new image and recognizing a character extracted from the previous image.  15 / - Device for reading characters written on a support, for implementing the method defined in one of the preceding claims, characterized in that it comprises  an optical system (13) maintained by carrier means (12) having a front face of support and adapted to form a clear image of an object situated substantially in the plane of the front face, on a matrix of photosensitive elements ( 18), with a view to obtaining electrical signals representative of this image,  means for coding these signals in digital form,  means adapted to extract, from among all of said signals, on the one hand signals characteristic of the positioning of the character or of the small number of characters with a view to generating vertical centering signals, on the other hand signals characteristic of the dimensions of each character,  means adapted to check whether the extracted signals correspond to a character fully captured and positioned within a determined horizontal interval,  correction warning means (23) adapted to warn the blind of a movement to be made on the carrier means (12) of the optical system (13),  means suitable for carrying out recognition tests on the characteristic signals of each character and for supplying control signals with a view to transcription in a system accessible to the blind,  and means for transcribing (9, 10) these signals in a system accessible to the blind.  16 / - Reading device according to claim 15, characterized in that the carrying means consist of a housing (12) whose front face of support is provided with a window (15) covering a surface slightly greater than that of 'one character or a small number of characters.  17 / - Reading device according to claim (15), characterized in that the optical system (13) comprises a doublet of weak focal length, adjustable magnification by displacement of said optical system (13) inside the housing.  18 / - Reading device according to claim 15, characterized in that the coding means comprise a Schmitt trigger with adjustable threshold, adapted to make it possible to compensate for the differences in contrast between the characters and their support.  19 / - Reading device according to claim 18, characterized in that the correction warning means accessible to the blind include a sound system adapted to emit sounds of different frequencies depending on the nature of the correction to be made.  20 / - Reading device according to claim 15, characterized in that the correction entertainment means accessible to the blind include a touch system comprising two vibrators (23) adapted to vibrate separately or simultaneously depending on the nature of the correction to carry out.  21 / - Reading device according to claim 16, characterized in that inside the housing (12) are arranged:  . the matrix of photosensitive elements (18),  . the printed circuit on a wafer (22) carrying the control circuit components of the matrix of photosensitive elements (18),  . the optical system (13),  a diaphragm (14) for increasing the depth of field,  . a lighting system (16),  . and the two warning vibrators (23) for displacement correction, each vibrator comprising a vibrating pad flush with one face of the housing (12).  22 / - Reading device according to claim 21, ea.actérisé in that the matrix of photosensitive elements (18) is housed in a dark room (19) inside the housing (12).  23 / - Reading device according to claim 15, in which the means of transcription in a system accessible to the blind include a tactile display (9) with Braille characters.  24 / - Reading device according to claim 15, wherein the means of transcription in a system accessible to the blind include -a sound transmitter (10) of Morse signals.  25 / - Reading device according to claim 15, characterized in that it comprises a display interface (11) in order to allow an indicator to follow the reading of the blind.