Likewise, at least one pivotably mounted light projection device 230 (of like configuration to light projection device 130 of FIG. 1) is provided in housing 210, and is configured to project an image, such as a spot or line, onto a surface after the location of the point of interest (e.g., a midpoint between two endpoints of surface) has been calculated. Light projection device 230 is mounted within housing 210 for pivotable movement through an arc parallel to the movement of one or more distance measurement devices 220a and 220b, and may be automatically moveable (such as via an internally mounted servo motor, not shown), or manually moveable via an additional control knob (not shown) on housing 210, or alternatively through electronic controls on housing 210. As with distance measurement devices 220a and 220b, light projection device 230 likewise includes an angular position sensor that detects the position, and more particularly the angle, at which light projection device 230 is aligned with respect to housing 210. The angular position sensor of light projection device 230 likewise communicates with the processor, thus enabling the processor to direct light projection device 230 to aim at the calculated point of interest, or to confirm that light projection device 230 is aimed at the calculated point of interest. When such aiming point has been achieved, the processor may direct that light projection device 230 project its image to the calculated point of interest, or may signal a user (such as by lighting an LED or generating an audible tone) that such angle has been achieved.

In certain configurations, multiple calculated intermediate points of interest (e.g., lines at every one-third-point along the surface) may simultaneously be displayed by the point determination and projection device. More particularly, multiple light projection devices 230 configured as described above may optionally be provided in housing 210, each such light projection device 230 being independently pivotably mounted in housing 210 to project light, such as a vertical line, at a targeted intermediate point of interest.

Optionally, each of distance measurement devices 220a and 220b and light projection device 230 may be physically embodied in a single device, operable to both measure distances and project an image to the calculated point of interest as described herein, without departing from the spirit and scope of the invention.

As mentioned above, a processor (not shown) may be provided inside of housing 210, and may be in data communication with each of distance measurement devices 220a and 220b and light projection device 230, which processor is programmed to receive angular data from the angular position sensors that detect the angular position of distance measurement devices 220a and 220b, and of light projection device 230, to calculate a point of interest with respect to two endpoints (such as the midpoint between two endpoints of a structural feature such as a wall), and to determine the necessary angle of light projection device 230 with respect to housing 210 that is necessary to direct an image projected from light projection device 230 onto the structural feature at the calculated location of the point of interest. The processor may also be programmed to direct a drive signal to a servo motor in housing 210, if point determination and projection device 100 is equipped with such a servo motor to automatically pivot light projection device 230 to the calculated point of interest. More particularly and as further detailed below, the processor may be programmed to receive the angle and distance data from each distance measurement device 220a and 220b, calculate the location of a point of interest, such as a midpoint, between the points measured by distance measurement devices 220a and 220b, calculate a projection angle for light projection device 230, and either (i) send a control signal to a drive for light projection device 230 to move it to the calculated projection angle, or (ii) communicate with a drive mechanism for the light projection device 230 to determine when the projection device is aimed at the calculated projection angle, and thus at the calculated point of interest.

Optionally, housing 210 may include a bubble level situated along the back edge 214 of housing 210 to aid a user in maintaining the point determination and projection device 100 level during use. Likewise, housing 210 may optionally be provided a stand, or threaded receptacle to receive a threaded stand (such as a tripod), on the bottom face of housing 210 to aid a user in keeping the point determination and projection device 100 steady during use. As a further option, housing 210 may employ self-leveling devices as are known to persons skilled in the art and employed in such devices as the Model DW088K Self-leveling Cross Line Laser commercially available from DeWALT.

In use, point determination and projection device 100 is used to determine and display the location of a point of interest in relation to two measured points. In the exemplary embodiment described herein, the point determination and projection device 100 is described in relation to the calculation and display of the location of a midpoint between two endpoints of a surface, such as a wall surface in a building, including in those circumstances in which one or more of the endpoints are hidden. Those skilled in the art will recognize, however, that other points of interest (e.g., x % of the distance from a first endpoint to a second endpoint) could likewise be calculated and displayed through simple adjustment of the geometric formulas set forth herein without departing from the spirit and scope of the invention.

With reference to FIG. 3, when configured for manual intervention, a third control knob 224 may be provided at the middle of top face 216 of housing 210. Once the calculation is completed to project midpoint m, the user may be notified (e.g., by way of an audible tone or visual indicator, such as a light). The user then turns third control knob 224 until the angular position sensor on light projection device 230 determines that the calculated angle is reached. When the light projection device 230 reaches the calculated angle, the midpoint m will be projected onto the wall via the laser pointer of light projection device 230.

In order to obtain accurate calculations, point determination and projection device 100 should be positioned as follows:

- a. The device should preferably be placed on a fixed, hard surface (e.g., a tabletop) or affixed to a stationary tripod of other support for stability.
- b. The front of the device should be positioned approximately parallel to the wall or other surface being measured, although it need not be exactly parallel, as the calculations described below can account for when it is askew.
- c. The lasers distance measurement devices and light projection device should have a clear line of sight to the wall or other surface being measured.
- d. The dials of the device should face upwards.
- e. The device should be horizontally level.

After such positioning of point determination and projection device 100, operation may proceed as follows and as shown in FIG. 4. At a first step 400, a user may select a mode of operation (as detailed below) to instruct the processor to operate in one of multiple wall configuration modes that will establish the series of measurements and manipulations to be performed by point determination and projection device 100. Next, at step 402, the user depresses a first one of the control knobs, such as control knob 222a, and holds such control knob to display a laser point onto the surface that is to be measured, and turns the control knob 222a to point the laser distance measurement device at the first point of interest (such as a first corner of a wall whose midpoint is to be located). Next, at step 404, the user releases the first control knob 222a, which action instructs the processor to capture the distance between the vertex of the point determination and projection device and the first point of interest. Next, at step 406, the user depresses a second one of the control knobs, such as control knob 222b, and holds such control knob to display a laser point onto the surface that is to be measured, and turns the control knob 222b to point the laser distance measurement device at the second point of interest (such as a second corner of a wall whose midpoint is to be located). Next, at step 408, the user releases the second control knob 222b, which action instructs the processor to capture the distance between the vertex of the point determination and projection device and the second point of interest, as well as the angle between the first laser distance measurement device and the second laser distance measurement device. Next, at step 410, upon completion of all measurements of points of interest, a user depresses a capture button on point determination and projection device 100 to instruct the processor that all measurements have been completed. Finally, at step 412, the processor calculates the designated point of interest, such as the midpoint of a wall section that is undergoing examination, and sends a drive signal to the servo motor in point determination and projection device 100 to move light projection device 230 to visually designate the calculated point of interest.

Those skilled in the art will recognize that the ordering of steps in FIG. 4 are exemplary only, and that the steps may be varied in order of performance without departing from the spirit and scope of the invention.

The following description sets forth several scenarios in which the point determination and projection device 100 may be used to solve the specific problem of finding a midpoint. In each such exemplary implementation, we presume that the point determination and projection device 100 is perfectly level, such that all geometric calculations are being performed in a two-dimensional plane. The following notational conventions are used:

- a. Upper case letters denote geometric points. Two distinguished points, M and P, represent the midpoint of a line segment and the location of the point determination and projection device 100, respectively.
- b. The line segment described by two points, X and Y is denoted by XY. Alternatively, lower case letters are used to name line segments.
- c. The length of a line segment is denoted by the segment's termination points concatenated sans the overline. E.g., XY denotes the length of line segment XY. Alternately, when the context is clear, the lower case name of a line segment is used to denote that segments lengths.
- d. Greek letters denote geometric angles.
- e. In the examples that follow and in the related figures (FIGS. 5A through 8):
  - (i) An open circle denotes a hidden corner.
  - (ii) The symbol denotes a measurement.
  - (iii) The symbol denotes a computed point/line projection.

Example 1—Basic Flat Wall (FIG. 5A and FIG. 5B)

In this operational mode, the point determination and projection device 100 is used to evaluate a flat wall with no protrusions at any point along the wall. The corners of the wall (points A and B) are in clear line-of-sight, as shown in plan view in FIG. 5A. In this scenario, the point determination and projection device performs the following steps, illustrated in FIG. 5B:

- a. Mode 1 (Basic Flat Wall) is selected by the user via a Mode button 218 on top face 216 of housing 210.
- b. The right distance measurement device 220a is directed at the rightmost corner B of the wall by rotating the control knob 222a on the top of the device 100.
- c. When the laser dot that is projected from distance measurement device 220a is displayed on the corner B of the wall, then the position of such endpoint is recorded, such as by depressing control knob 222a downward into housing 210.
- d. The distance measurement device 220a that is directed via dial 222a is a measurement laser—therefore, at this point, the device has captured a measurement of the distance from the center of the device to the rightmost corner of the wall, i.e., the length of line segment b.
- e. The left distance measurement device 220b is directed at the leftmost corner A of the wall by rotating the control knob 222b on the top of the device 100.
- f. When the laser dot that is projected from distance measurement device 220b is displayed on the corner A of the wall, then the position of such endpoint is recorded, such as by depressing control knob 222b downward into housing 210.
- g. The distance measurement device 220b that is directed via dial 222b is a measurement laser—therefore, at this point, the device has captured a measurement of the distance from the center of the device to the leftmost corner of the wall, i.e., the length of line segment a.
- h. Using the processor, the device 100 automatically calculates the length of the wall by using the triangle that was created from 3 points: {A, P, B}, as discussed below. In this case, P is the center of the device, A is the left corner of the wall and B is the right corner of the wall.