PULSE DETECTION APPARATUS AND PULSE DETECTION METHOD

1 . A pulse detection apparatus, comprising:

a pulse wave detector that detects a pulse wave, and outputs a pulse wave signal indicating the pulse wave that has been detected;

a threshold value setting circuit that sets a threshold value that changes with time in accordance with an amplitude of the pulse wave signal; and

a comparator that compares the pulse wave signal with the threshold value, and outputs, as information indicating a pulse, the pulse wave signal exceeding the threshold value.

2 . The pulse detection apparatus according to claim 1 , further comprising a first constant multiplication circuit that constant-multiplies the pulse wave signal by a value larger than 1, the pulse wave signal indicating the pulse wave, wherein:

the threshold value setting circuit includes:

a sample and hold circuit that holds a peak value of the pulse wave signal that has been detected by the pulse wave detector; and

a time constant circuit that maintains the peak value for a predetermined time, and outputs the peak value as the threshold value, the peak value having been held by the sample and hold circuit, and

the comparator compares the pulse wave signal with the threshold value, the pulse wave signal having been constant-multiplied by the first constant multiplication circuit, the threshold having been outputted from the sample and hold circuit.

3 . The pulse detection apparatus according to claim 1 , wherein:

the threshold value setting circuit includes:

a sample and hold circuit that holds a peak value of the pulse wave signal that has been detected by the pulse wave detector;

a time constant circuit that maintains the peak value for a predetermined time, and outputs the peak value as the threshold value, the peak value having been held by the sample and hold circuit; and

a second constant multiplication circuit that constant-multiplies the threshold value by a value smaller than 1, the threshold value having been outputted from the time constant circuit, and

the comparator compares the pulse wave signal with the threshold value, the pulse wave signal having been outputted from the pulse wave detector, the threshold value having been constant-multiplied by the second constant multiplication circuit.

4 . The pulse detection apparatus according to claim 1 , further comprising a first constant multiplication circuit that constant-multiplies the pulse wave signal by a value larger than 1, the pulse wave signal indicating the pulse wave, wherein:

the threshold value setting circuit includes:

a sample and hold circuit that holds a peak value of the pulse wave signal that has been detected by the pulse wave detector;

a time constant circuit that maintains the peak value for a predetermined time, and outputs the peak value as the threshold value, the peak value having been held by the sample and hold circuit; and

a second constant multiplication circuit that constant-multiplies the threshold value by a value smaller than 1, the threshold value having been outputted from the time constant circuit, and

the comparator compares the pulse wave signal with the threshold value, the pulse wave signal having been constant-multiplied by the first constant multiplication circuit, the threshold value having been constant-multiplied by the second constant multiplication circuit.

5 . The pulse detection apparatus according to any one of claim 2 , further comprising a constant voltage circuit that sets a lower limit value of the threshold value outputted from the time constant circuit.

6 . A pulse detection method, comprising:

detecting a pulse wave, and outputting a pulse wave signal indicating the pulse wave that has been detected;

setting a threshold value that changes with time in accordance with an amplitude of the pulse wave signal; and

comparing the pulse wave signal with the threshold value, and outputting, as information indicating a pulse, the pulse wave signal exceeding the threshold value.

7 . The pulse detection method according to claim 6 , comprising:

constant-multiplying the pulse wave signal by a value larger than 1;

holding a peak value of the pulse wave signal;

maintaining the peak value for a predetermined time, and outputting the peak value as the threshold value, the peak value having been held; and

comparing the pulse wave signal with the threshold value, the pulse wave signal having been constant-multiplied, the threshold value having been maintained for the predetermined time.

8 . The pulse detection method according to claim 6 , comprising:

holding a peak value of the pulse wave signal;

maintaining the peak value for a predetermined time, and outputting the peak value as the threshold value, the peak value having been held;

constant-multiplying the threshold value by a value smaller than 1, the threshold value having been maintained for the predetermined time; and

comparing the pulse wave signal with the threshold value that has been constant-multiplied.

9 . The pulse detection method according to claim 6 , comprising:

constant-multiplying the pulse wave signal by a value larger than 1;

holding a peak value of the pulse wave signal;

maintaining the peak value for a predetermined time, and outputting the peak value as the threshold value, the peak value having been held;

constant-multiplying the threshold value by a value smaller than 1, the threshold value having been maintained for the predetermined time; and

comparing the pulse wave signal with the threshold value, the pulse wave signal having been constant-multiplied, the threshold value having been constant-multiplied.