Metal detector, in particular mine detector

A metal detector for finding and locating metal objects located underneath a ground surface, wherein the ground has a specific ground character, comprising:

• a search head with a transmitting unit for transmitting electrical and/or magnetic signals or signal sequences past the surface;
• a metal detection unit with a receiving unit for response signals or response signal sequences, said receiving unit having at least one response signal strength sensor, and a device for indicating or displaying a presence of a metal object underneath the surface;
• a distance measurement sensor disposed on or in said search head and configured to estimate a depth and a size of the metal object, said distance measurement sensor having a transmitting unit for transmitting signals at frequencies which can each be set to desired values, and configured to determine an actual instantaneous geometric distance between said search head and the ground surface;
• a measurement data logic unit disposed to receive data from said response signal sensor and said distance measurement sensor, said measurement data logic unit receiving sets of response field strength measurement data and response signal level measurement data, and ground distance measurement data, in each case determined at a time in an event of a change in the distance between the search head and the ground surface when said search head is raised or lowered from or to the ground surface and generating a respective instantaneous distance/signal strength curve or algorithm reflecting a functionality between the response signal and the distance between said search head and the surface in digitized form or as a data packet;
• a curve comparison unit connected for dataflow and data interchange to said measurement data logic unit, and a standard curve and algorithm storage unit connected for dataflow and data interchange to said curve comparison unit, said standard curve and algorithm storage unit containing, stored together with information associated therewith relating to various parameters, a collection, matrix or library with a large number of standard distance/signal strength curves or algorithms, represented in digitized form or as a data packet, predetermined with a comparative detector of a same type from a large number of different, in each case predetermined standard conditions or with predetermined standard parameters selected from the group consisting of depth, size, volume and/or area extent, shape and position of the measurement object, frequency of the signals transmitted from the transmitting unit, and the ground character, and being configured to be supplied therefrom with the standard distance/signal strength curves or algorithms, and equipped with software for selection of a standard distance/signal strength curve or algorithm stored in said standard curve and algorithm storage unit and most similar to the respective distance/signal strength curve or algorithm determined at that time for the metal object currently being located;
• and
• a categorization unit for emitting from said curve and algorithm comparison unit parameter information associated with the respective standard distance/signal strength curve or algorithm selected from said standard curve storage unit and which is most similar with respect to the size and depth of the metal object, said categorization unit converting the information to qualitative or semi-quantitative object depth data and object size data, to a display unit configured to display in a small number of discrete measurement value steps at least those values that correspond to the depth and the size of the respective currently located measurement object, at a point which is easily visible for a user of the metal detector.

A method for detecting metal objects at least partially located underneath a ground surface, which method comprises:

• providing a metal detector with a search head having at least one transmitting unit for the transmission of electrical and/or magnetic signals or signal sequences into the ground, and with a metal detection unit having at least one receiving unit for response signals or response signal sequences with at least one field strength sensor, a ground distance measurement sensor, and a device for indicating or displaying a presence of a metal object in the ground, and with a distance measurement sensor;
• in a first stage, defining a plurality of different discrete measurement condition parameters by positioning metal objects of a discrete different size, shape or form, spatial position and composed of different metals, in subsoils or grounds of different character at different discrete depths underneath the ground surface;
• in a second stage, producing a family of standard distance/signal strength curves and algorithms applicable to a parameter that is in each case set for changing, discrete values, while keeping all other parameters constant, with the metal detector, in each case after choosing and setting one of the parameters and, optionally an appliance-specific parameter of the appliance to predetermined discrete different values, while keeping all other parameters constant, with the metal detector changing a distance of a search head from the ground surface, and storing the family in a standard curve and algorithm storage unit, and proceeding analogously with appropriate changes to the respective parameters to be changed discretely, and with each of the other parameters being kept constant, until a standard ground distance/signal strength curve and algorithm library has been obtained;
• in a third stage, upon locating a metal object that is unknown in terms of parameters, changing a distance of the search head from the ground surface with the metal detector or a metal detector of a same type, and producing a current distance/signal strength curve or algorithm with a measurement data logic unit from the current ground distance and response signal strength measurement data and comparing in a comparison unit with standard distance/signal strength curves and algorithms called up from a standard curve and algorithm storage unit, and selecting a standard distance/signal strength curve or algorithm which is most similar in terms of a coordinate position and profile to the respective currently determined distance/signal strength curve or algorithm, and passing on a depth parameter and object size parameter to the device for indicating or displaying for conversion of the parameters to a small number of clear display steps;
• and
• in a fourth stage, displaying the clear display steps to a person operating the metal detector, for recovering the metal object on the basis of the semi-quantitatively displayed object size and depth.