Light measuring device
First Claim
1. A light measuring device having a plurality of ranges for measuring light and comprising:
- a light responsive means for receiving light and for producing an electrical signal as a function of the received light;
an integration means including a capacitor means for integrating said electrical signal so as to change the amount of charge stored in said capacitor means;
a first control means for controlling the integration means such that said electrical signal is integrated during a predetermined period of time;
a means for setting said capacitor means to a predetermined initial condition before the integration of said electrical signal;
a means for producing a plurality of constant currents having different levels;
a means for selecting one of said plurality of constant currents in dependence on said changed amount of charge in said capacitor means;
a second control means for controlling said constant current producing means such that said selected constant current is supplied to or withdrawn from said capacitor means subsequent to the completion of said integration of said electrical signal for said predetermined periodd of time;
so as to again place said capacitor means to its predetermined initial condition;
a means for detecting the moment of time when said capacitor means again reaches said predetermined initial condition due to said selected constant current; and
a means for measuring the time interval from the moment of time when said constant current producing means starts to supply said selected constant current to said capacitor means to the moment of time when said detecting means detects that said capacitor means has again reached said predetermined initial condition.
1 Assignment
0 Petitions
Accused Products
Abstract
A light measuring device includes one or more photodiodes, which generate current in relation to the received light, and at least one capacitor for integrating the generated current. The amount of charge stored in the at least one capacitor at the completion of the integration is roughly detected by the number of capacitors used and/or the voltage across the capacitor. A current source capable of producing different levels of current in accordance with the detected amount of charge is provided for changing the amount of charge stored in the at least one capacitor. The time needed to change the amount of charge stored in the at least one capacitor is measured so as to obtain the value of total amount of the change in the charge stored in the at least one capacitor and to thus obtain the value of the received amount of light intensity.
-
Citations
35 Claims
-
1. A light measuring device having a plurality of ranges for measuring light and comprising:
-
a light responsive means for receiving light and for producing an electrical signal as a function of the received light; an integration means including a capacitor means for integrating said electrical signal so as to change the amount of charge stored in said capacitor means; a first control means for controlling the integration means such that said electrical signal is integrated during a predetermined period of time; a means for setting said capacitor means to a predetermined initial condition before the integration of said electrical signal; a means for producing a plurality of constant currents having different levels; a means for selecting one of said plurality of constant currents in dependence on said changed amount of charge in said capacitor means; a second control means for controlling said constant current producing means such that said selected constant current is supplied to or withdrawn from said capacitor means subsequent to the completion of said integration of said electrical signal for said predetermined periodd of time;
so as to again place said capacitor means to its predetermined initial condition;a means for detecting the moment of time when said capacitor means again reaches said predetermined initial condition due to said selected constant current; and a means for measuring the time interval from the moment of time when said constant current producing means starts to supply said selected constant current to said capacitor means to the moment of time when said detecting means detects that said capacitor means has again reached said predetermined initial condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. A light measuring device having a plurality of ranges for measuring light and comprising:
-
a light responsive means for receiving light and for producing a voltage signal as a function of the received light; an integration means, including both a means for generating an electric current commensurate with said voltage signal and a capacitor means, for integrating said electric current so as to change the amount of charge stored in said capacitor means; a first control means for controlling the integration means such that said integration is effected during a predetermined period of time; a means for setting said capacitor means to a predetermined initial condition before said integration; a means for producing a plurality of constant currents having different levels; a means for selecting one of said constant currents in dependence upon said voltage signal; a second control means for controlling said constant current producing means such that said selected current is supplied to or withdrawn from said capacitor means subsequent to the end of said predetermined period of time so as to again place said capacitor in its predetermined initial condition; a means for detecting the moment of time when said capacitor means again reaches said predetermined initial condition due to said selected constant current; and a means for measuring the time interval from the moment of time when said constant current producing means starts to supply said selected constant current to said capacitor means to the moment of time when said detecting means detects that said capacitor means has again reached said predetermined initial condition. - View Dependent Claims (17, 18, 19, 20, 21)
-
-
22. A light measuring device of the integration type comprising:
-
a light responsive means for generating an output as a function of light received thereby; an integration means, including a capacitor means which is chargeable, for integrating the output of said light responsive means for a given time period and for generating an integration output representative of the integrated value; a discharge means for discharging said capacitor means that has been charged to a level commensurate with the integration output, said discharge means including a plurality of discharge paths for respectively discharging said capacitor means with constant currents of different values; a means for selecting the discharge path in accordance with the level of said integration output; and means for generating a digital signal as a function of the time during which said charged capacitor is discharged to a given level. - View Dependent Claims (23, 24, 25, 26, 27, 28)
-
-
29. A light measuring device of the integration type comprising:
-
a light responsive means for generating an output as a function of light received thereby; an integration means including a capacitor means which is chargeable for integrating the output of said light responsive means for a given time period and for generating an integration output representative of the integrated value; a discharge means for discharging said capacitor means that has been charged to a level commensurate with the integration output, said discharge means including a plurality of discharge paths for respectively discharging said capacitor means with constant currents of different values; a means for selecting the discharge path in accordance with the level of the output of said light responsive means; and a means for generating a digital signal as a function of the time during which said charged capacitor is discharged to a given level. - View Dependent Claims (30, 31, 32)
-
-
33. A light measuring device of the integration type comprising:
-
a light responsive means for generating an output as a function of the intensity of the light received thereby; an integration means for integrating the output of said light responsive means for a given period of time; a reverse integration means for reversely integrating the integrated output by means of a constant current; a means for selecting the level of said constant current from a plurality of predetermined different levels in accordance with the integrated output; and a means for generating a digital signal as a function of the time duration of said reverse integration.
-
-
34. A light measuring device of the integration type comprising:
-
a light responsive means for generating an output as a function of the intensity of the light received thereby; an integration means for integrating the output of said light responsive means for a given period of time; a reverse integration means for reversely integrating the integrated output by means of a constant current; a means for selecting the level of said constant current from a plurality of predetermined different levels in accordance with the output of said light responsive means; and a means for generating a digital signal as a function of the time duration of said reverse integration.
-
-
35. A light measuring device comprising:
-
a light responsive means for generating an output as a function of the intensity of the light received thereby; an integration means, including a capacitor means, whose charge changes from its initial amount to an integrated amount commensurate with the integration of said output for a given time; a reverse integration means for changing the charge stored in said capacitance means from said integrated amount to said initial amount by means of a constant current; a range detection means for detecting which one of a plurality of ranges of light measurement the light being measured falls in; a selection means for selecting the level of said constant current from a plurality of predetermined different levels in accordance with the detected range; and a means for generating a digital signal as a function of the time duration of the reverse integration.
-
Specification