Light powered hearing aid

1. A hearing aid comprising in combination:

a) a case containing electronics for processing audio signals,

b) a battery for powering the electronics,

c) a photovoltaic cell responsive to light for generating an electrical voltage,

d) a charging circuit coupled to the photovoltaic cell for charging the battery,

e) a voltage comparator having an input coupled to the photovoltaic cell and being responsive to the electrical voltage generated thereby, the voltage comparator including an output for providing a first output signal when the electrical voltage generated by the photovoltaic cell is greater than a reference voltage, and for providing a second output signal when the electrical voltage generated by the photovoltaic cell is less than said reference voltage, and

f) a timer coupled to the output of the voltage comparator, said timer detecting changes at the output of the voltage comparator between the first output signal and the second output signal having a duration of approximately 0.2 seconds or longer resulting from variations in the intensity of light incident upon said photovoltaic cell,

g) wherein said electronics for processing audio signals is responsive to the timer for controlling the manner in which such audio signals are processed.

2. The hearing aid as set forth in claim 1 and further including a digital to analog converter for producing a reference voltage coupled to said voltage comparator.

3. The hearing aid as set forth in claim 1 and further including a microprocessor coupled to said timer.

4. The hearing aid as set forth in claim 3 wherein said microprocessor is programmed with several routines and said microprocessor is responsive to said timer for selecting which routine to execute.

5. The hearing aid as set forth in claim 1 wherein said hearing aid includes more than one photovoltaic cell.

6. The hearing aid as set forth in claim 1 wherein said photovoltaic cell is a thin film coating on said case.

7. The hearing aid as set forth in claim 1 further including a programmed microprocessor, and wherein said timer is implemented as software in said microprocessor.

8. A hearing aid comprising in combination:

a) a case containing electronics for processing audio signals,

b) a battery for powering the electronics,

c) a photovoltaic cell responsive to light for generating an electrical voltage, and

d) a charging circuit coupled to the photovoltaic cell for charging the battery,

e) a voltage comparator having an input coupled to the photovoltaic cell and being responsive to the electrical voltage generated thereby, the voltage comparator including an output for producing a pulse width modulated signal when the intensity of light incident upon the photovoltaic cell crosses a threshold magnitude,

f) a timer coupled to the output of the voltage comparator, said timer detecting data received as variations in the intensity of light incident upon said photovoltaic cell,

g) wherein said pulse width modulated signal has a frequency below approximately 5 Hz.

9. The hearing aid as set forth in claim 8 and further including a digital to analog converter for producing a reference voltage coupled to said voltage comparator.

10. The hearing aid as set forth in claim 8 and further including a microprocessor coupled to said timer.

11. The hearing aid as set forth in claim 10 wherein said microprocessor is programmed with several routines and said microprocessor is responsive to said timer for selecting which routine to execute.

12. The hearing aid as set forth in claim 8 further including a programmed microprocessor, and wherein said timer is implemented as software in said microprocessor.

13. A method of controlling a hearing aid, the hearing aid including a case containing electronics for processing audio signals, a battery for powering the electronics, first and second photovoltaic cells each responsive to light for generating an electrical voltage, a charging circuit coupled to at least one of the first and second photovoltaic cells for charging the battery, and a control circuit for selecting from among a plurality of audio signal processing modes, the method comprising the steps of:

a) monitoring the intensity of light incident upon the first photovoltaic cell;

b) monitoring the intensity of light incident upon the second photovoltaic cell;

c) detecting that the light incident upon the first photovoltaic cell has been reduced to a low intensity for a predetermined duration of approximately two seconds or more, while the light incident upon the second photovoltaic cell remains at a significantly higher intensity over the same duration, and generating a mode selection signal in response to such detection; and

d) causing the control circuit to change a currently selected audio signal processing mode in response to the generation of the mode selection signal in step c).