1. A smoke detector, comprising:
a dark chamber, adapted to accommodate smoke particles;
a photo emitter, disposed in the dark chamber;
a photo detector, disposed in the dark chamber;
a first region, at which an illumination region where light emitted from the photo emitter passes and a light detecting region where the photo detector is capable of detecting light are overlapped, so that light emitted from the photo emitter and scattered by the smoke particles is detected by the photo detector; and
a reflective photo converger, which converges light passed through the first region at a second region which is located outside of the first region.
2. The smoke detector as set forth in claim 1, wherein the second region is situated outside of a plane defined by an optical axis of the photo emitter and an optical axis of the photo detector.
3. The smoke detector as set forth in claim 1,
wherein the dark chamber is provided with a photo attenuator which attenuates light converged by the photo converger.
4. The smoke detector as set forth in claim 1, wherein the reflective photo converger includes a concave face configured to reflect the light passed through the first region and to converge the reflected light at the second region.
5. The smoke detector as set forth in claim 4, wherein the concave face faces downward.
6. The smoke detector as set forth in claim 1, wherein the reflective photo converger is monolithically formed with the dark chamber.
7. The smoke detector as set forth in claim 1, wherein:
the dark chamber is provided with a labyrinth structure which allows the smoke particles to enter the dark chamber while preventing external light from entering the first region; and
the reflective photo converger constitutes a part of the labyrinth structure.
8. The smoke detector as set forth in claim 1, wherein the reflective photo converger has a streamlined face which faces an outside of the dark chamber.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of controlling rate of adaptation of an adaptive filter in an echo canceller, having both hardware and software components, to accommodate different hybrids connected thereto, comprising:
calculating an expected Echo Return Loss Enhancement (ERLE) for said echo canceller;
calculating current ERLE of an input signal (Sin) applied to said echo canceller;
determining if the current ERLE is greater than the expected ERLE multiplied by a constant (Stage1 ERLEFactor), then adjusting the adaptation step (mu) to Mu=Mu*MuRedFactorMin, and if the current ERLE is greater than or equal to the expected ERLE, then adjusting the adaptation step (Mu) to Mu=Mu*MuRedFactorMax; and
one of either (i) increasing the adaptation step of said adaptive filter in the event the difference between the current ERLE and the expected ERLE is greater than a predetermined amount, or (ii) decreasing said adaptation step in the event said difference is less than said predetermined amount.
2. The method of claim 1, wherein said calculating current ERLE of said input signal further comprises calculating total energy (Es) of said input signal (Sin) and energy (Ee) of an output signal (ein) from said echo canceller, and dividing said energy (Es) by said energy (Ee).
3. The method of claim1, wherein Stage1_ERLEFactor=0.5, MuRedFactorMin=0.5 and MuRedFactorMax=0.25.
4. An echo canceller having both hardware and software components, comprising:
a first energy calculator for receiving a reference signal (Rin) and calculating energy (Er) thereof;
an expected ERLE estimator and current ERLE calculator for calculating ERLE_expected and ERLE_current, respectively:
an adaptation step calculator;
an adaptive filter connected to said adaptation step calculator for controlling rate of adaptation of filter coefficients thereof;
an ERL calculator for calculating the ERL of an input signal (Sin);
a noise level calculator connected to said ERLE estimator, for calculating noise energy (EnergyNoise) in said input signal;
a second energy calculator for calculating total energy in said input signal (Sin);
a subtractor for subtracting from said input signal (Sin) the signal output from said adaptive filter, and
a third energy calculator for calculating energy (Ee) in the signal output from said subtractor and in response outputting an error signal (ein),
wherein, one of either (i) increasing the adaptation step of said adaptive filter in the event a difference between the current ERLE and the expected ERLE is greater than a predetermined amount, or (ii) decreasing said adaptation step in the event said difference is less than said predetermined amount.
5. The method of claim 4, wherein said step expected ERLE estimator and current ERLE calculator operate and wherein said calculating ERIE current of said input signal further comprises calculating total energy (Es) of said input signal (Sin) and energy (Ee) of an output signal (ein) from said echo canceller, and dividing said energy (Es) by said energy (Ee).
6. The echo canceller of claim 4, wherein said adaptation step calculator operates and wherein the step of one of either increasing or decreasing said adaptation step further comprises:
determining if the current ERLE is greater than the expected ERLE multiplied by a constant (Stage1_ERLEFactor), then adjusting the adaptation step (mu) to Mu=Mu*MuRedFactorMin, and if the current ERLE is greater than or equal to the expected ERLE, then adjusting the adaptation step (Mu) to Mu=Mu*MuRedFactorMax.
7. The echo canceller of claim 4, wherein said adaptation step calculator operates and wherein Stage1_ERLEFactor=0.5, MuRedFactorMin=0.5 and MuRedFactorMax=0.25.