IE46598B1 - Aid for the blind - Google Patents

Abstract

AID FOR THE BLIND A sight aid for the blind comprises a video device for producing video signals relating to the view in the field of vision of said video device, an amplifier connected to the video device, a transmitting aerial connected to the amplifier and arranged in the vicinity of the eye-socket, a receiver arranged near or in the eye-socket and coupled electromagnetically to the transmitting aerial, the output of said receiver having two output electrodes one of which is coupled via the lachrymal fluid to a still functioning part of the optical pathways or to the end of the optic nerve.

Description

The invention relates to a sight aid.for the blind in whom the optic nerve still extends to the region of at least one eye-socket. The remaining parts of the optic pathway should still function. The invention may be used by. those whose eyeballs have been removed.

Attempts have previously been made to restore a certain degree of visual faculty to persons blind in this way. To this end, the output signals from a television camera have been coupled to the optic pathways via probes connected by an operation to said optic pathways within the skull. These experiments failed, however, since the parts of the optic pathways to which the probes are connected become unusable even after a relatively short period of time, and the probe therefore has to be removed by operation. Thus, after a certain time there are no more parts of optical pathways to which the probes can be connected.

It is obvious that a sight aid for the blind-would be extremely valuable. Such a sight aid is provided by the present invention.

According to the invention there is provided a sight aid for the blind, comprising a video device for producing video signals relating to the view in the field of vision of said video device, an amplifier connected to the video device., a transmitting aerial connected to the amplifier and arranged in the vicinity of the eye-socket, a receiver arranged near or in - 2 -46588 the eye-socket and coupled eleetromagnetically to the transmitting aerial, the output of said receiver having two output electrodes, one of which is coupled via the lachrymal fluid to a still functioning part of the optical pathways or t'o the end of the optic nerve.

Practical tests carried out with the sight aid according to the invention have shown that the afore-mentioned class of persons can actually recognise objects with this aid. The resolving power in the recognition of objects obviously depends on the resolution of the video device. Letters approximately three centimetres high can be recognised by a patient using a CCDelement (charge coupled device) of the latest type. A certain amount of practice on the part of the patient is also a help in recognising objects.

A principal advantage of the sight aid according to the invention is that the picture signals are coupled to the optical pathways via the lachrymal fluid, and accordingly those parts of the optical pathways involved in the coupling are not damaged.

One embodiment of the invention will now be described with the aid of the accompanying drawings, in which:Figure 1 is a diagrammatic and perspective view of a frame carrying the transmitting unit of a sight aid according to the invention; Figure 2 is a diagrammatic view of the optical arrangement and CCD-element of the video device; .) - prosthesis unit in which the r'.:fiver is Figure 1 shows a spectacies-type frame 2 whose side par 10 3 and front part 4 accommodate the electronic components for th. transmitting unit of the sight aid. Figure 1 also shows ciagrammatically an objective lens 5 for forming images of objects in the proximity of a blind person, on a likewise diagramatica represented CCD-element 6. A CCD-element is a photoelectric component that can scan a picture formed on a screen of the eL-t and produce a video output signal which depends on the br' -htr. -values at the individual points of the screen. CCD-eler?* ts tr known per se and are manufactured and marketed by, for tx -Is the Fairchild Camera and Instrument Corporation, Figure 2 shows diagrammatidally the optica] devic < CCD-element in their geometrical arrangement. ‘t:.e ob-et is arranged so that the distance a can be varied ir. orctr ... form sharply defined images of objects at various distants the sensitive surface of the CCD-element 6. The pictr./: t: angle oi of the CCD-element 6 is for example 60° in the ....· - 4 10 CCD 211 type manufactured by Fairchild Camera and Instrument ) Corporation. The front part 4 of: the frame 2 is shown removed from the CCD-element 6 in Figure 2 so that the latter can be seen more easily. In actual fact the CCD-elgment practically sits in the front part 4. The distance between the objective 5 and the CCD-element 6 is determined by the type of objective.

Figure 3 shows a block diagram of the electronic device of the transmitting unit of the sight aid. As has previously been mentioned, the picture being transmitted to the blind person is formed by the objective 5 on the CCD-element 6. Figure 3 shows diagrammatically a CCD-element CCD 202 manufactured by Fairchild Camera and Instrument Corporation, the inputs being designated as follows: + =· positive input voltage 0¾ = horizontal, analog register-transport timing pulse 0¾ = inverted, analog register-transport timing pulse 0R = scanning pulse 0P = picture backspace pulse and picture element-reset pulse 0Vj ° vertical, analog register-transport timing pulse 0^2 " inverted, analog register-transport timing pulse I These input signals for the CCD 202 are produced in a known f manner by a pulse generator 20 and control circuit 22, and ! !· delivered to the CCD 202, The time co-ordination of the different E input pulse trains, the necessary voltages, and the like, are | j i i - 5 46596 given by the manufacturers of CCD-elements, to whom reference should be made.

If the CCD-element 6 is controlled with the said input signals and if a picture is projected on the'photosensitive surface, CCD 202 delivers a video output signal via the line 24, I and a compensation output signal via the line 24 . These signals are amplified in a wide band video amplifier 26 and delivered to an output stage 28, and from there to a transmitting coil 29.

This tra nEmitting coil 29 is connected at one end to the output stage 28, and is earthed at the other end.

Figure 4 shows a detailed block diagram of the wide band video amplifier 26 and output stage 28 of Figure 3. The video signal is delivered to an amplifier 30, which may for example be a juA 733 type integrated circuit, via an impedance converter consisting of a transistor 32 and a variable resistor 34, and a capacitive coupling stage consisting of a capacitor 36 and a resistor 38. Corresponding to this, the compensation signal from the CCD is applied to the inverting input of the amplifier 30 via an impedance converter consisting of a transistor 40 and a variable resistor 42, and to a capacitive coupling consisting of a condenser 44 and resistor 46. The impedance converter and capacitiv coupling are in both cases the same, and accordingly only the connection of the parts at the non-inverting input of the amplifier 30 will be described. The video signal is applied to the transistor base 32, the collector being at the operating voltage - 6 465S8 and the emitter leading to the variable resistor 34. The other end of the resistor 34 is earthed and its wiper leads to the capacitor 36. The resistor 38 is located between the capacitor and the non-inverting input on the one hand, and earth on the other hand. A variable resistor is provided at the inputs 4 and 11 of the amplifier 30 in order to be able to adjust externally the degree of amplification. Another way of adjusting the degree of amplification is of course to adjust the input voltages via the resistors 34 and 42. I'he positive operating voltage for the amplifier 30 is applied to the connection 10, and the negative operating voltage of the amplifier 30 at the connection 5 of the integrated circuit, A capacitor 50 and a terminating resistor 52 are provided at the output 8, both components being connected in series and the resistor being earthed.

The amplified video signal is derived from the output 7 of the amplifier 30. A capacitor 54 for d.c. separation of the following amplification stage is first of all provided at the output 7. The capacitor 54 is connected to a resistor 56 which is earthed.

The signal arising at the connection point between the capacitor 54 and the resistor 56 is passed to the output stage 28, which in the present case is a push-pull output stage consisting of an NPN and a PNP transistor 60 and 62 respectively. The signal passes to the base contacts of the two transistors via a diode 64 - 7 48598 and a diode 66, which arc orientated so that the NPN transistor receives the negative part of the signal via the diode 64, and the positive part of the signal is delivered to the transistor 62 via the diode 66. The resistors 68 and 70 serve to adjust the base bias of the transistors 60 and 62. The collector of the transistor 60 is at the positive reference voltage, whereas the collector of the transistor 62 is at the negative reference voltage. The emitter of the PNP transistor 60 is connected to a resistor 72, and the emitter of the transistor 62 to a resistor 74. The other ends of the resistors are connected to one another and form the output of the output stage 28, The signal arising at the output is 7 volts peak-to-peak in the case of a circuit tested practically. It has been found that such a signal is suitable for feeding the transmitting coil 29 and also for conveying signals to the receiving coil 82 (Figure 4).

The transmitting coil 29, which serves as a transmitting aerial for the transmitting unit of the sight aid, consists of two series-connected coils with 15 to 20 windings, the individual windings having a diameter of about 3 to 4 cm. One part of the coil is arranged in the vicinity of the left eye-socket and the other part of the coil in the vicinity of the right eye-socket, and in such a way that the coils lie on the inside of the front part 4 of the frame 2.

Figure 5 shows the electrical circuitry of the receiver 80. - 8 i c s a β The receiver 80 has a receiving coil 82, a capacitor 84 connected in parallel thereto, and a diode 86 located between one end of the receiving coil 82 and the capacitor 84. In the practical embodiment of the receiver about 50 m of wire are wound to form the coil 82, and the diode and capacitor are chosen so that an optimum inductive coupling effect is achieved between the transmitting coil 29 and the receiving coil 82. With this optimum coupling arrangement the 7 volts peak-to-peak on the transmitting coil 29 are sufficient for the image signals from the receiver to affect the optic nerve. Tlie output of the receiver 80 is formed by two electrodes 88, 90. The electrodes 88, 90 each, consists of approximately 25 cm long gold wire having a crosssectional area of 0.09 cm wound toroidally, the cross-sectional width of the toroid being approximately 1 mm. j I The spatial arrangement of the components of the receiver j in an ocular prosthesis member 92 is shown in Figure 6. The j I back of the member 92, which faces the rear wall of the eye-socket, j has a recess 94 in which one output electrode 88 is arranged in I the form of a ring. The recess 94 is closed by a plate 96 of j I J porous material. The other output electrode 90 is located in I Ϊ > an annular hollow space 98 extending around the completely sealed- j ! I in receiving coil 82. The capacitor 84 and diode 86 are also > ϋ ! completely sealed in the prosthesis member 92. When the member » 1' has been assembled and the output electrode has been connected ’ s - 9 - ? I 46596 up, a hole 100 is bored through the hollow space 98, which is then filled with water. The hole 100 is then sealed so that there is no longer any flow connection between the hollow space 98 and the recess 94. The recess 94 is filled with a liquid corresponding to lachrymal fluid, e.g. Optrik, and the plate 96 is impregnated with the same liquid. If the member 92 is now inserted in the eye-socket, the liquid in the recess 94 will be continuously replaced by the lachrymal fluid produced by the blind person himself. The output signal of the receiver 80 thus pass via the lachrymal fluid to the still functioning parts of the optical pathways. The coupled signals are, as can be seen from the above description, the output signals of the CCDelement after amplification, coupling to the receiver, nnd processing in the receiver circuit. These signals represent the result of a screen-like scanning of the light-sensitive surface of the CCD-element, as is known.

The information transmitted via these signals to the optical pathways is sufficient, as has been shown by practical tests with the sight aid according to the invention, to enable a person wearing such a sight aid to see.

It should be mentioned that the invention is not restricted to blind persons whose eyeballs have been removed. If the prosthesis member 92 is suitably designed, persons whose eyeballs are still present but are completely non-functioning may also - 10 4 6 5 3 8 see with the sight nid according to the invention. In this case too the picture signals from the receiver are coupled to the still functioning parts of the optical pathways, in particular the optic nerve, via lachrymal fluid and, initially, via a substitute fluid, for example Optrik.

The invention is obviously' also not restricted to the afore-mentioned type of CCD-element. Instead, video devices corresponding to the latest state of the art will be used in order to improve the resolving power of the sight aid. These may or may not be CCD-elements. The sight aid is ready for operation when a receiver is inserted. The visual faculty may be further improved by employing two receivers, one receiver in each case being coupled to part of the transmitting coil 29. It is also within the scope of the invention to provide video devices with separate transmitters and receivers, in order to provide stereoscopic vision.

By choosing a particular CCD-element, a preferred frequency range is established corresponding to the CCD-element. Such CCDelements whose maximum sensitivity is in the frequency range in which the sensitivity of the human eye is greatest, will preferably be chosen. On the other hand, the video device can also be designed so that other frequency ranges are optimally used. By virtue of the fact that the degree of amplification of the amplifier 26 can be adjusted, the sight aid can be adjusted if the brightness 4659© conditions alter. In other words, the signal level at the output of the receiver can always be maintained at the same value irrespective of whether the user is in bright day-light or in a comparatively dark room.

Claims (18)

1. j 1. A sight aid for the blind, comprising a video device for j j producing video signals relating to the view in the field of j vision of said video device, an amplifier connected to the video j 5 device, a transmitting aerial connected to the amplifier and arranged in the vicinity of the eye-sockct, a receiver arranged near or in the eye-socket and coupled electromagnetically to ί the transmitting aerial, the output of said receiver having two j output electrodes one of which is coupled via the lachrymal ; 10 fluid to a still functioning part of the optical pathways or - to the end of the optic nerve.

2. A sight aid according to claim 1, wherein the video device comprises a CCD-element.

3. A sight aid according to claim 2, wherein an adjustable 15 objective lens is optically coupled with the CCD-element.

4. A sight aid according to any of the preceding claims wherein the amplifier comprises a wide band video amplifier and an output stage.

5. A sight aid according to any of the preceding claims wherein 20 the output signal of the amplifier is substantially 7 volts peakto-peak.

6. A sight aid according to any of the preceding claims wherein thr transmitting aerial comprises a coil.

7. A sight aid according to claim 6, wherein the coil has 25 two part-coils with about 25 windings and with a diameter of ' 4 β 6 ® 8 about 3 to 4 cm, one part coil being arranged in the vicinity of the left eye-socket, and the other part coil in the vicinity of the right eye-socket.

8. A sight aid according to any of the preceding claims 5 wherein the video device, the amplifier, end the transmitting aerial are arranged on a spectacles-like frame, worn like spectacles.

9. A sight aid according to any of the preceding claims wherein a receiver is arranged in or at each eye-socket.

10. 10. A sight aid according to any of the preceding claims wherein the receiver has a coil, a capacitor connected in parallel therewith and a diode connected between one end of the coil and the condenser.

11. A sight aid according to claim 10, wherein an output electrode is connected to the other end of the receiver coil, 15 and the other output electrode is joined to the connection point between the capacitor and the diode.

12. A sight aid according to any of the preceding claims wherein the output electrodes are formed as toroids.

13. A sight aid according to claim 12, wherein the toroids 20 consist of a gold wire about 25 cm long with a cross-section of 2 0.9 cm , and the cross-section of the toroid being about 1 mm in width.

14. A sight aid according to claim 1, wherein the receiver is arranged in an ocular prosthesis member. 4308

15. A sight aid according to claim 14, wherein the receiver and an output electrode are encapsulated in the said ocular prosthesis member, and the other output electrode is arranged on the side of the ocular prosthesis member facing the eye-socket 5 rear wall in such a way that it is in contact with the lachrymal fluid.

16. A sight aid according to claim 15, wherein the other output electrode is located in a recess of the member, which is closed by a plate of porous material. 10

17. A sight aid according to claim 15, wherein the encapsulated output electrode is likewise embedded in a conducting liquid, in particular water.

18. A sight aid substantially as hereinbefore described with reference to the accompanying drawings.