WO2007019629A1

WO2007019629A1 - Illuminated eye chart

Info

Publication number: WO2007019629A1
Application number: PCT/AU2006/001174
Authority: WO
Inventors: Philip Stuart Esnouf
Original assignee: Philip Stuart Esnouf
Priority date: 2005-08-15
Filing date: 2006-08-15
Publication date: 2007-02-22

Abstract

An eye chart device including a plurality of panels, each defining a viewable field, at least one letter or indicium on or in each viewable field and control means for selectively illuminating each panel whereby the illumination of a particular panel defines which letter or indicium is to be viewed by the subject.

Description

ILLUMINATED EYE CHART

This invention relates to an illuminated eye chart.

An object of the present invention is to provide an illuminated eye chart which has a number of panels on which letters or other indicia can be printed, overlayed or otherwise applied to or embodied therein and wherein the background to the letter or other indicia can be selectively illuminated so as to indicate to the person undergoing the eye test which letters or indicia are to be viewed.

According to the present invention there is provided an eye chart device including a plurality of panels, each defining a viewable field, at least one letter or indicium on or in each viewable field and control means for selectively illuminating each panel whereby the illumination of a particular panel defines which letter or indicium is to be viewed by the subject.

Preferably the device is portable.

Preferably, each panel comprises a panel of electroluminescent material.

Preferably further, the letter or indicium is printed on or overlayed over the front face panel.

Preferably further, the control means includes a remote unit for sending signals to a sensor to selectively illuminate the respective panels.

Preferably further, the panels are arranged in a vertical array.

Preferably further, the remote unit includes a first control button activation of which causes illumination to change from one panel to the panel vertically adjacent thereto. Preferably further, the control unit includes a second control button activation of which causes illumination of the panel vertically above the panel which was previously illuminated. With this arrangement, the operator can remotely control sequential illumination of the panels upwardly and downwardly.

The invention also provides a method of testing the visual acuity of a subject, the method including the steps of: causing the subject to look at a display device having a plurality of electroluminescent panels each having one or more letters thereon from a predetermined distance; using a remote controller to selectively illuminate said electroluminescent panels; and determining the visual acuity of the subject by reference to which of the letters on the panels can be identified by the subject.

The invention will now be further described with reference to the accompanying drawings, in which:

FIGURE 1 is a perspective view of an eye chart device of the invention;

FIGURE 2 is a circuit diagram of an embodiment of the invention; FIGURE 3 shows the face of the eye chart in more detail;

FIGURE 4 shows a modified circuit diagram; and

FIGURE 5 shows a circuit diagram for a preferred form of remote control unit.

Figure 1 shows an eye chart device 2 and a remote control unit 4. The eye chart device 2 includes a display assembly 6 which includes eight electroluminescent panels 8,

10, 12, 14, 16, 18, 20 and 22. The panels may be mounted behind a transparent front sheet

29 of acrylic or the like. The device includes a base housing 24 within which is located circuitry for selectively illuminating the panels 8 to 22, as will be described below. Each of the panels 8 includes one or more letters 26, the size of which decreases in a known way in order to test the visual acuity of a subject. The letters can be arranged in accordance with the so-called "Snellen Eye Chart", either metric or imperial, according to requirements. The letters 26 are preferably printed onto the front sheet 29.

In the illustrated embodiment, each of the panels is surrounded by a dark border 28 so as to obscure gaps between the individual panels and provide a neat and attractive appearance for the device. The borders 28 also serve to more clearly delineate the particular electroluminescent field which is being illuminated. The borders are preferably printed onto the front sheet 29.

The front face of the housing 24 includes a sensor 30 for sensing control signals generated by the remote unit 4. Preferably the remote unit 4 utilises coded infrared signals, in accordance with known principles.

The device of the invention enables a medical practitioner, ophthalmologist, optician or other person who needs to carry out an eye test (hereinafter referred to as an operator) on a subject to very expeditiously carry out the eye test. For instance, the device 2 could be mounted on a bench, shelf or wall or other suitable location and the operator can remain seated at a desk while carrying out the test. The operator presses a switch 60 on the remote unit 4 in order to selectively illuminate the respective electroluminescent panels 8, 10, 12, 14, 16, 18, 20 and 22. Normally activation of the switch causes initial illumination of the top panel 8. A subsequent pressing of the switch 60 causes the illumination to switch to the next lower most panel 10 and further pressings of the switch 60 causes successively downward illumination of the panels. The subject would clearly be able to identify which panel is to be viewed because it would be illuminated whilst all the other panels would not be illuminated.

The use of the electroluminescent panels can also enable a predetermined level of backlighting relative to the letters 26 in order to provide an accurate visual acuity test.

Figure 2 diagrammatically illustrates typical circuitry for the embodiment of Figure 1. The control circuitry 32 located within the housing 24 includes the infrared sensor 30 which is coupled to a decoder circuit 34 which produces electrical pulses each time an infrared pulse is received by the sensor 30 from the remote unit 4. Output from the decoder 34 is inputed to the CLOCK input 36 of a Johnson decade counter 38. The counter 38 has eight outputs (01-08) 40 which are connected to respective electroluminescent panels 8 to 22 by means of drive transistors 42.

Each of the electroluminescent panels includes ground terminals 44, which are coupled to the respective transistors 42, and input terminals 46, all of which are coupled to an inverter 48. The inverter is operable to produce an operating voltage which is sufficient to illuminate the respective panels 8 to 22. The panels are preferably made by Starlite Technology, serial No. ELW8PEC and operate at an operating voltage of about 100 volts AC and at a frequency of about 700Hz. The inverter 48 is also controlled by means of the decade counter 38. In the illustrated arrangement, a switching transistor 54 is coupled to a voltage supply input 52 of the inverter 48. The switching transistor 54 is normally ON so that the inverter 48 is normally ON and is operable to produce on its output a suitable voltage for driving the panels 8 to 22. The gate electrode of the transistor 54 is coupled to the first output (00) 50 of the counter 38 and this output is arranged to turn the switching transistor 54 OFF, after each of the other eight outputs 40 has been activated to successively illuminate the respective panels 8 to 22.

The remote unit 4 includes a battery 56 coupled to an encoder circuit 58 by means of a press button switch 60, the arrangement being such that each time the button switch 60 is pressed, the encoder generates an operating signal which is applied to an infrared LED transmitter 62. The first signal produced by the switch 60 is received by the sensor 30 and the decoder 34 and operates on the counter 38 in order to activate the output 50 and the output (01) 40 for the first panel 8. This causes operation of the inverter 48 to turn on the drive transistor 42 coupled to the first panel to turn on. The operating voltage produced by the inverter is therefor applied across the terminals 44 and 46 of the first panel 8 and it will become illuminated. The other panels will not be illuminated because their drive transistors 42 will not be activated. When the button switch 60 is again pressed, the decoder 34 activates only the second output (02) 40 of the counter 38 whereby only the second panel 10 is illuminated. Successive operations of the button switch 60 causes the panels to be successively illuminated. After the last panel 22 has been illuminated, the next pressing of the switch 60 is arranged to cause the first output (00) 50 to be activated. This switches switching transistor 54 off and the inverter 48 no longer operates and none of the panels are illuminated.

The circuitry 32 includes a power supply 64 which in the illustrated arrangement includes a six volt battery 66 (or 4 x 1.5V batteries) coupled across a capacitor 68 which acts as a high frequency filter to eliminate spikes of voltage which might otherwise damage the semiconductor components in the circuit. The arrangement in which the inverter 48 is turned off at the end of the sequence helps conserve battery life. The use of a battery enables the device to be portable which is advantageous. Alternatively, a rectified power supply may be provided instead of or in addition to the batteries.

The chart is designed to be read at 3m or 10 feet depending whether it is to be used in a metric or non-metric environment. The preferred dimensions are set out below in Table 1. These dimensions are based on a principal that normal visual acuity 20/20 allows resolution of an image of one minute of arc at a distance of 20 feet or 6 metres and this is tested by using an optotype that has a height of 5 minutes of arc (8.73mm) and a limb width of 1 minute of arc (1.75). This information is referenced from Adler's physiology of the eye (Mosby). These optotypes have been scaled for the electroluminescent eye chart in order that the chart can be read at a distance of 10 feet or 3 metres. For this chart the 20/20 optotypes are adjusted to be 4.36mm high. The device could alternatively be configured for use at a distance of 6 metres in which case the optotypes are proportionally increased in size. TABLE 1

Figure 3 more accurately shows the preferred relative sizes of the various panels and letters 26 thereon.

The electroluminescent material allows for backlighting which may be consistent with relevant standards. It would be desirable if the material was operated so as to provide for lighting at an equivalent wavelength in the range 2500-2000K and at a luminance in the range 80-320 cd/m2.

The use of the electroluminescent material and its associated electronics have significant technical advantages over other forms of illumination such as fixed backlighting or projector style charts:

• Specifically the low power consumption of the electroluminescent material allows for the device to be powered by batteries which means it can be portable and compact with an acceptable battery life.

• The device can selectively illuminate optotypes to be read.

• The device can be manufactured so as it is of minimal thickness and thus can be hung on a wall or sat on a shelf.

• The device can be activated remotely by the operator or physician.

• The device can be manufactured at a cost not usually achievable for an eye chart of this level of sophistication.

In the circuitry shown in Figure 2, the remote unit 4 includes a single switch 60 for changing illumination from the top to the bottom. Figures 4 and 5 show a modified remote unit and control circuitry which enable the user to move the illumination upwardly or downwardly. In these drawings, the same reference numerals have been used to denote parts which are the same as or correspond to those of the earlier embodiment.

In this arrangement, the remote unit 4 includes an ON/OFF switch 80, UP switch 82 and DOWN switch 84. The remote unit includes a TX2B encoder, the ON/OFF switch being connected to pin 6, the UP switch 82 connected to pin 1 and the DOWN switch 84 connected to pin 14. The remote unit includes a drive transistor 86 which is connected to pin 7, the LED 62 being connected in circuit with the drive transistor 86. Pressing of the

UP switch 82 or DOWN switch 84 causes the encoder 58 to generate signals appropriate for moving the illumination of the panels upwardly and downwardly respectively.

Figure 5 shows the control circuitry 32 which can be used with the remote unit 4 shown in Figure 4. Coded infrared signals produced by the remote unit 4 are received by the sensor 30 and amplified in transistor 88 prior to being inputted to the decoder 34. In this case, the decoder 34 is an RX2B circuit. In this circuitry, the inverter 48 produces an operating voltage suitable for operating the panels 8 to 22 when the decoder 34 receives a signal corresponding to operation of the ON/OFF switch 80 to an ON position. This is achieved by coupling output from pin 12 of the decoder circuit 34 to a trigger circuit 90, which may comprise a CD 4013, the output of which is coupled to the gate of transistor 54 which provides driving current to the inverter 48.

The circuit 32 includes two NAND gates 92 and 94 which may comprise CD 401 1 circuits. The inputs of the NAND gates 92 and 94 are coupled to pins 7 and 6 respectively of the decoder 34. Outputs from the NAND gates are coupled to inputs of an up/down counter 96 having eight outputs 40 for driving the drive transistors 42. The up/down counter 96 may include a synchronous four bit up/down dicode binary counter 98 coupled to a BCD to decimal decoder 100. When the DOWN switch 84 is pressed, the decoder 34 will produce a high level on pin 7 and this causes the up/down counter 96 to cause a high level on one of its outputs 42 step in a downward direction whereby illumination of the panels moves downwardly. A subsequent pressing of the DOWN switch 84 has a similar effect. The opposite effect is achieved when the UP switch 82 is activated.

Many modifications to the device are possible. For instance, the illustrated arrangement includes eight luminescent panels. It may be possible to add a further panel at the bottom which represents 6/4 or 20/12 vision.

It is also desirable that the operator has the option of controlling the direction of successive illumination of the panels. In the arrangement described above, the direction is downward from the top panel 8 to the bottom panel 22. This can be reversed by providing appropriate circuitry. In this arrangement the control unit 4 may include two additional buttons (not shown) to commence the up or down sequence. Further, the control unit 4 may include a return button which returns the focal point to the top left of the chart. In this arrangement the control unit 4 would include the on/off switch 60 and three additional buttons to control down sequencing, up sequencing and return to the top left of the chart.

Many further modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. An eye chart device including a plurality of panels, each defining a viewable field, at least one letter or indicium on or in each viewable field and control means for selectively illuminating each panel whereby the illumination of a particular panel defines which letter or indicium is to be viewed by the subject.

2. A device as claimed in claim 1 wherein each panel comprises a panel of electroluminescent material.

3. A device as claimed in claim 2 including a transparent front face panel behind which said plurality of panels are located.

4. A device as claimed in claim 3 wherein said at least one letter or indicium are printed on or overlayed over the front face panel.

5. A device as claimed in claim 3 or 4 wherein borders are printed onto the front face panel to overlie edges of the panels of electroluminescent material.

6. A device as claimed in claim 3, 4 or 5 wherein the panels of electroluminescent material are arranged in a vertical array.

7. A device as claimed in any one of claims 3 to 6 wherein the panels of electroluminescent material generally decrease in height from the uppermost panel to the lowermost panel.

8. A device as claimed in claim 7 wherein the size of the said at least one letter or indicium decreases from the uppermost panel to the lowermost panel.

9. A device as claimed in claim 8 wherein the uppermost panel has a single letter of height H and the successively lower panels have letters of heights 0.6H, 0.4H, 0.3H, 0.2H,

0.15H, 0.1H and 0.084H respectively.

10. A device as claimed in claim 9 wherein the height H of the letter on the uppermost panel is about 44mm.

11. A device as claimed in any one of claims 1 to 10 wherein the control means is operable to illuminate each panel with a predetermined level of luminance.

12. A device as claimed in claim 11 wherein the control means is operable to illuminate each panel with a luminance in the range 80 to 320 cd/m².

13. A device as claimed in claim 11 or 12 wherein each panel emits light with equivalent wavelengths in the range 2500 to 2000K.

14. A device as claimed in any one of claims 1 to 13 including a base housing within which the control means is mounted and upon which the plurality of panels are mounted.

15. A device as claimed in any one of claims 1 to 14 including a remote controller for producing control signals for said control means.

16. A device as claimed in claim 7 or any one of claims 8 to 15 as appended directly or indirectly to claim 7 wherein the remote controller includes a first button which, upon successive pressings thereof by an operator, causes the control means to illuminate successively lower electroluminescent panels.

17. A device as claimed in claim 16 wherein the remote controller includes a second button which, upon successive pressings thereof by an operator, causes the control means to illuminate successively higher electroluminescent panels.

18. A device as claimed in claim 16 or 17 wherein the remote controller includes a third button which, on pressing thereof by an operator, causes the control means to illuminate the uppermost panel.

19. A device as claimed in claim 16, 17 or 18 wherein the remote controller includes an ON/OFF switch for controlling supply of power to the control means.

20. A device as claimed in any one of claims 1 to 19 wherein the device is battery operated and portable.

21. A method of testing the visual acuity of a subject, the method including the steps of: causing the subject to look at a display device having a plurality of electroluminescent panels each having one or more letters thereon from a predetermined distance; using a remote controller to selectively illuminate said electroluminescent panels; and determining the visual acuity of the subject by reference to which of the letters on the panels can be identified by the subject.