Method and apparatus for reliably detecting light beam in the presence of undesirable light, especially suitable for surveying instruments

A light beam detection apparatus, comprising:

• 1) light receiving means for converting a received light beam into an electrical signal;
• 2) peak holding means for holding a value of the electrical signal, that is a maximum value of the electrical signal for a predetermined sampling period;
• 3) means for storing the maximum value of the electrical signal as a stored value;
• 4) means for determining whether or not three maximum values have been stored;
• 5) means for comparing the stored maximum values with each other, when the means for determining determines that three maximum values have been stored;
• and
• 6) means for judging whether the light beam detection apparatus should either:
• 6a) use a first stored value of the three stored values for subsequent signal processing;
• or
• 6b) conclude that the stored values are based on noise;
• the judging depending on whether or not:
• i) the first stored value is larger than second and third of the three stored values;
• and
• ii) the second and third stored values are substantially equal to each other.

In a light beam detection apparatus having at least two light receiving means for receiving a beam of light turned about a vertical axis to define a reference plane and for converting the received light beam into an electrical signal, the light beam detection apparatus being adapted to measure the amount of light beam entering it and to output a signal representing a relative positional relationship between the entering light beam and the reference plane, the improvement comprising:

• 1) peak holding means for holding a value of the electrical signal, that is a maximum value of the electrical signal for a predetermined sampling period;
• 2) means for storing the maximum value of the electrical signal as a stored value;
• 3) means for determining whether or not three maximum values have been stored;
• 4) means for comparing the stored maximum values with each other, when the means for determining determines that three maximum values have been stored;
• and
• 5) means for judging whether the light beam detection apparatus should either:
• 5a) use a first stored value of the three stored values for subsequent signal processing;
• or
• 5b) conclude that the stored values are based on noise;
• the judging depending on whether or not:
• i) the first stored value is larger than second and third of the three stored values;
• and
• ii) the second and third stored values are substantially equal to each other.

A light beam detection method, comprising:

• 1) converting a received light beam into an electrical signal;
• 2) holding a value of the electrical signal that is a maximum value of the electrical signal for a predetermined sampling period;
• 3) storing the maximum value of the electrical signal in a memory as a stored value;
• 4) determining whether or not two maximum values have been stored in the memory;
• 5) comparing the stored values with each other, when it is determined that two such maximum values have been stored;
• and
• 6) performing a further step, based on the comparing step, the further step including either:
• 6a) using a first stored value of the two stored values for subsequent signal processing;
• or
• 6b) concluding that the stored values are based on noise;
• the further step being chosen depending on whether or not the first stored value is larger than the second stored value.

A light beam detection apparatus, comprising:

• 1) light receiving means for converting a received light beam into an electrical signal;
• 2) peak holding means for holding a value of the electrical signal, that is a maximum value of the electrical signal for a predetermined sampling period;
• 3) means for storing the maximum value of the electrical signal as a stored value;
• 4) means for determining whether or not two maximum values have been stored;
• 5) means for comparing the stored maximum values with each other, when the means for determining determines that two maximum values have been stored;
• and
• 6) means for judging whether the light beam detection apparatus should either:
• 6a) use a first stored value of the two stored values for subsequent signal processing;
• or
• 6b) conclude that the stored values are based on noise;
• the judging depending on whether or not the first stored value is larger than second store value.

In a light beam detection apparatus having at least two light receiving means for receiving a beam of light turned about a vertical axis to define a reference plane and for converting the received light beam into an electrical signal, the light beam detection apparatus being adapted to measure the amount of light beam entering it and to output a signal representing a relative positional relationship between the entering light beam and the reference plane, the improvement comprising:

• 1) peak holding means for holding a value of the electrical signal, that is a maximum value of the electrical signal for a predetermined sampling period;
• 2) means for storing the maximum value of the electrical signal as a stored value;
• 3) means for determining whether or not two maximum values have been stored;
• 4) means for comparing the stored maximum values with each other, when the means for determining determines that two maximum values have been stored;
• and
• 5) means for judging whether the light beam detection apparatus should either:
• 5a) use a first stored value of the two stored values for subsequent signal processing;
• or
• 5b) conclude that the stored values are based on noise;
• the judging depending on whether or not the first stored value is larger than second store value.