Rapid focusing during aiming in laser scanner

An electro-optical reader for reading a symbol, comprising:

• means for emitting a light beam along a path;
• means including a variable focusing element for focusing the light beam on the symbol located in a range of working distances relative to the reader along the path;
• means for sweeping the light beam across the symbol for return therefrom;
• means for detecting return light from the symbol, and for generating an electrical analog signal indicative of the detected return light;
• and
• control means for controlling the sweeping means to sweep the light beam over an aiming angle at an aiming rate to form an aiming line on the symbol during an aiming mode of operation, and over a reading angle at a reading rate to form a reading line on the symbol during a reading mode of operation that follows the aiming mode, the aiming angle being smaller than the reading angle, the aiming rate being higher than the reading rate, the aiming line being shorter than the reading line,
• the control means being further operative for determining a depth of modulation of the analog signal during the aiming mode, and for controlling the variable focusing element to focus the light beam on the symbol during the aiming mode when the depth of modulation is determined to be optimum, and
• the control means being further operative for processing the analog signal to data indicative of the symbol during the reading mode.

A method of reading a symbol, comprising the steps of:

• emitting a light beam along a path;
• focusing the light beam on the symbol located in a range of working distances along the path with a variable focusing element;
• sweeping the light beam across the symbol for return therefrom;
• detecting return light from the symbol, and generating an electrical analog signal indicative of the detected return light;
• and
• controlling the sweeping step to sweep the light beam over an aiming angle at an aiming rate to form an aiming line on the symbol during an aiming mode of operation, and over a reading angle at a reading rate to form a reading line on the symbol during a reading mode of operation that follows the aiming mode, the aiming angle being smaller than the reading angle, the aiming rate being higher than the reading rate, the aiming line being shorter than the reading line,
• determining a depth of modulation of the analog signal during the aiming mode, and controlling the variable focusing element to focus the light beam on the symbol during the aiming mode when the depth of modulation is determined to be optimum, and
• processing the analog signal to data indicative of the symbol during the reading mode.