Analog to digital conversion using an integrater and a sample and hold circuit

Claim 3

The device of claim 1 wherein the integrating means comprises an operational amplifier.

Claim 4

The device of claim 1 wherein the control means comprises a microprocessor.

Claim 5

The device of claim 1 wherein the analog signal is provided by a photodiode.

Claim 6

The device of claim 1 wherein the analog signal is provided by a current to voltage converter.

Claim 7

The device of claim 1 wherein the device operates in a first mode at a predetermined rate and a second mode at a second predetermined rate, the mode being determined by the control means.

Claim 10

The method of claim 7 further comprising a step of controlling the step of integrating and the step of sampling and holding.

Claim 11

The method of claim 8 wherein the step of controlling is performed at at least two predetermined rates.

Claim 12

The device of claim 3, wherein the microprocessor is adapted to periodically reset the integrating means with a jitter time of not more than about an execution time of one instruction in the microprocessor.

Claim 13

The device of claim 3, wherein the microprocessor is adapted to periodically generate a sample and hold signal to the sample and hold means with a jitter time of not more than about an execution time of one instruction in the microprocessor.

Claim 14

The device of claim 11, further comprising a converter for analog to digital conversion of a signal held by said sample and hold means, wherein the analog to digital convertion takes place between two consecutive sample and hold signals.

Claim 15

The device of claim 3, wherein the microprocessor is adapted to generate the control signals using a high priority non-maskable interrupt.

Claim 16

The device of claim 1, wherein the analog signal is provided by a photosensor.

Claim 17

A circuit for converting an analog current derived from a photosensor to a digital signal comprising: a current to voltage converter for converting the analog current derived from the photosensor to a first voltage substantially continually; an integrator for integrating the first voltage substantially continually and providing an integrated voltage, the integrator being rest in response to a first signal; a sample and hold circuit for sampling and holding the integrated voltage in response to a second signal; a converter for analog to digital conversion of a voltage held by the sample and hold circuit to a frequency varying signal, the frequency varying signal being a digital representative of the analog current; a counter for counting a frequency of the frequency varying signal produced by the converter; and a processor for generating first signals to the integrator at predetermined intervals of time and second signals to the sample and hold circuit at predetermined intervals of time.

Claim 18

A circuit for converting an analog current derived from a photosensor to a digital signal comprising: a current to voltage converter for converting the analog current derived from the photosensor to a first voltage substantially continually; an integrator for integrating the first voltage substantially continually and providing an integrated voltage, the integrator being rest in response to a first signal; a sample and hold circuit for sampling and holding the integrated voltage in response to a second signal; a converter for analog to digital conversion of a voltage held by the sample and hold circuit to a frequency varying signal, the frequency varying signal being a digital representative of the analog current; a counter for counting a frequency of the frequency varying signal produced by the converter; and a processor for generating first signals to the integrator at predetermined intervals of time and second signals to the sample and hold circuit at predetermined intervals of time.