Abstract:
An apparatus including an enclosure having an interior surface and an exterior surface; a first radiation sensor coupled to the interior surface being configured to produce a first signal dependent on the radiation sensed by the first radiation sensor; a second radiation sensor coupled to the interior surface being configured to produce a second signal dependent on the radiation sensed by the second radiation sensor; and a bus accessible from the exterior surface, the bus being coupled to the first radiation sensor and the second radiation sensor.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to the field of levels; more particularly, the present invention relates to a radiation-sensitive-device based level.  
           [0003]    2. Description of Related Art  
           [0004]    Levels are typically used to determine whether a line or plane is perpendicular to the force of gravity. Levels are used in numerous applications.  
           [0005]    One type of level is a structure that has a flat surface and a tubular container mounted to the structure such that the longitudinal axis of the tubular container is parallel to the length of the flat surface. The tubular container is partially filled with a liquid such that there is a bubble in the tubular container. Two lines are marked about the middle of the tubular container such that when the length of the flat surface is level, the bubble is between the two lines.  
           [0006]    Some levels include a tubular container that is parallel to the width of the flat surface. Two lines are marked about the middle of the tubular container such that when the width of the flat surface is level, the bubble is between the two lines.  
           [0007]    Some levels include a tubular container that is at some other orientation to the length (or the width) of the flat surface. Two lines are marked about the middle of the tubular container such that when the length and/or the width of the flat surface has a particular orientation to the level orientation, the bubble is between the two lines. For example, the tubular container may be oriented at a 45 degrees incline relative to the length of the flat surface. Thus, when the length of the flat surface rises at a 45 degree angle, the bubble in that tubular container is between the two lines.  
           [0008]    Determining whether the bubble is centered between the lines may be difficult in poor lighting conditions or because of awkward positioning of the level relative to the line of sight. Therefore, it is desirable to provide a level that is readable in a wider range of conditions.  
           [0009]    The orientation of the tubular containers is fixed relative to the flat surface of the level. Thus, the typical level can determine whether the orientation is one of a limited number of orientations defined by the fixed positions of the tubular containers relative to the flat surface. In some applications, it is desirable to determine whether a line has another orientation besides the standard ones, such as level and a 45 degree incline. For example, one may want to determine if a line is at a 30 degree incline.  
           [0010]    In some applications, it is desirable to measure the orientation (for example, in degrees) rather than simply determine whether or not the level has a particular orientation or not. Furthermore, it may be desirable to periodically measure the orientation and store it.  
           [0011]    What is needed is an apparatus to more easily determine the orientation of a line or a surface.  
         SUMMARY OF THE INVENTION  
         [0012]    An apparatus including an enclosure having an interior surface and an exterior surface; a first radiation sensor coupled to the interior surface being configured to produce a first signal dependent on the radiation sensed by the first radiation sensor; a second radiation sensor coupled to the interior surface being configured to produce a second signal dependent on the radiation sensed by the second radiation sensor; and a bus accessible from the exterior surface, the bus being coupled to the first radiation sensor and the second radiation sensor.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 illustrates one embodiment of a level device of the present invention.  
         [0014]    [0014]FIG. 2 illustrates one embodiment of a level of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0015]    In one embodiment, the present invention is an apparatus to more easily determine whether a line or a surface is level. In another embodiment, the present invention is an apparatus to determine whether a line or a surface has a user-selected orientation. In yet another embodiment, the present invention is an apparatus to measure the orientation of a line or a surface relative to a particular orientation, such as the level orientation.  
         [0016]    In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the described invention. Some of these specific details need not be used to practice the invention. In other instances, well-known structures, signals, and methods have not been shown in detail in order not to obscure the described invention.  
         [0017]    [0017]FIG. 1 illustrates one embodiment of a level device of the present invention.  
         [0018]    A level device  100  includes a container  170 , an analysis circuit  150 , a reference memory  151 , and an interface device  160 .  
         [0019]    The container  170  has an interior surface  190  and an exterior surface  195 . A charge couple device (CCD) array  120  is coupled to the interior surface  190 . The CCD array  120  includes at least two CCD sensors coupled such that they are serially accessible through an access bus  140 . The container  170  is partially filled with a liquid  110 . When the container is oriented such that the plane of the CCD array  120  is approximately parallel to the force of gravity, a portion of the interior surface  190  is obscured by the liquid  110  and a portion of the interior surface is exposed to define a liquid profile  180  at the interface between the liquid  110  and the interior surface  190 . The liquid profile  180  is a line that is level (perpendicular to the force of gravity).  
         [0020]    In one embodiment, a portion of the container  170  is transparent to allow ambient radiation to enter the container  170 . Alternatively, the level device  100  includes a radiation source to provide radiation within the container  170 .  
         [0021]    The liquid  110  is transparent or opaque to the radiation. The CCD sensors are sensitive to the radiation. When a CCD sensor is obscured by the liquid  110 , the intensity of radiation incident to the CCD sensor is less than when the CCD sensor is not obscured by the liquid  110 . In one embodiment, the radiation is visible light. Alternatively, the radiation is non-visible radiation or some combination of visible and non-visible radiation.  
         [0022]    In one embodiment, the CCD array  120  is disposed between the interior surface  190  and the exterior surface  195  such that the CCD array  120  is not in direct contact with the liquid  110 . The portion of the material between the CCD array  120  and the interior surface  190  is transparent to the radiation. Alternatively, the liquid  110  directly contacts the CCD array  120  and the liquid  110  is selected such that it does not interact with the CCD array  120  to cause malfunctions.  
         [0023]    Each CCD sensor generates a signal corresponding to the intensity of the incident radiation. The CCD array  120  is coupled to the access bus  140 . In one embodiment, the signals corresponding to each of the CCD sensors in the CCD array  120  are serially accessible through the access bus  140 . Other access methods may be used. For example, each CCD sensor may be directly accessible through the access bus  140 .  
         [0024]    The analysis circuit  150  is coupled to the access bus  140  and the interface device  160 . The analysis circuit  150  includes logic to access the signals from the CCD array  120  and determine the location of the liquid profile  180 . In one embodiment, each signal is analog and the analysis circuit  150  compares each signal against a threshold voltage to determine if the CCD sensor corresponding to that signal is obscured by the liquid  110 . Alternatively, each signal is a digital signal indicating whether that CCD sensor is obscured by the liquid  110 .  
         [0025]    In one embodiment, the threshold voltage is set at the midpoint between the voltage of the signal generated by a first reference CCD sensor that is known to be exposed and the voltage of the signal generated by a second reference CCD sensor that is known to be obscured. For example, the two reference CCD sensors may be positioned within the container  170  such that both reference CCD sensors cannot be covered by the liquid  110  at the same time. In another embodiment, the threshold voltage is the midpoint between the maximum voltage generated by a CCD sensor and the minimum voltage generated by a CCD sensor when the CCD array  120  is accessed. Alternatively, the threshold voltage is the midpoint between the maximum expected voltage generated by an obscured CCD sensor and the minimum expected voltage generated by an exposed CCD sensor. The expected voltages may be based, for example, on the manufacturing tolerances of the radiation source and the CCD sensors and the degree that the liquid  110  transmits incident radiation (transparency). Other methods of selecting a threshold value may be used.  
         [0026]    In one embodiment, the interface device  160  is used to provide information to a user. The information may include an indication as to whether or not the level device  100  is level and/or a measurement of the orientation in degrees. In one embodiment, the interface device  160  includes a light emitting diode that is on when the level device  100  is level. In another embodiment, the interface device  160  includes a sound source that generates a sound when the level device  100  is level. In yet another embodiment, the interface device  160  includes a display that is used to indicate whether or not the level device  100  is level. In addition, the display may be used to graphically indicate the measured orientation or textually indicate the orientation in units such as degrees. Furthermore, the interface device  160  may interface with another device used to periodically sample the output of the analysis circuit  150 . In one embodiment, one or more of these measurements are stored in a memory, such as random-access memory (RAM), magnetic tape, or a hard-disk drive.  
         [0027]    In one embodiment, the interface device  160  holds measurements in a memory or on the display in response to an input by the user, such as pressing a button. Thus, the user may hold a measurement for reading in better lighting conditions or in order to save it for subsequent reference, for example.  
         [0028]    There are numerous methods to analyze the signals from the CCD array  120  to determine whether or not the level device  100  is level or to provide a measurement of the orientation in degrees or radians, for example.  
         [0029]    In one embodiment, a CCD sensor  121  and a CCD sensor  124  are laterally positioned on the interior surface  190  such that they are both slightly below the surface of the liquid  110  when the level device  100  is level. Thus, when the level device  100  is level, neither the CCD sensor  121  nor the CCD sensor  124  are exposed. If the left side of the level device  100  rises from the level orientation to a sufficient degree, the liquid profile  180  will fall relative to the CCD sensor  121  to expose it. Similarly, if the right side of the level device  100  rises from the level orientation to a sufficient degree, the liquid profile  180  will fall relative to the CCD sensor  124  to expose it. Thus, the analysis circuit  110  is configured to indicate that the level device  100  is level if neither the CCD sensor  121  nor the CCD sensor  124  is exposed. The distance the CCD sensors are placed from the surface of the liquid  110  relative to the distance between the CCD sensors (as measured when the level device  100  is level) determines the range of angles that will be considered level.  
         [0030]    Alternatively, the two CCD sensors may be placed slightly above the surface of the liquid such that when the level device  100  is determined to be level when neither of the two CCD sensors is obscured.  
         [0031]    In another embodiment, a first column of CCD sensors and a second column of CCD sensors are laterally positioned on either side of the interior surface  190  such that both columns are perpendicular to the liquid profile  180  when the level device  100  is level. Each CCD sensor in the first column of CCD sensors has a corresponding CCD sensor in the second column of CCD sensors such that the corresponding pair of CCD sensors are the same distance from the liquid profile  180  (measured along the line perpendicular to the liquid profile  180 ) when the level device  100  is level. The level device  100  is determined to be level when each of the corresponding pairs of CCD sensors have the same status. For example, in a case where each column of CCD sensors has 20 CCD sensors, if 8 corresponding pairs of CCD sensors are both obscured and the other  12  corresponding pairs of CCD sensors are both exposed, the level device  100  is determined to be level. On the other hand, if one of the corresponding pairs of CCD sensors have one CCD sensor that is obscured and the other CCD sensor that is exposed, the device is determined to not be level. The density of the CCD sensors in each column and the distance between the two columns determines the range of angles that will be considered level.  
         [0032]    In another embodiment, the relative position of each CCD sensor is used to measure the orientation in degrees for example. An X-axis that is level and a Y-axis that is perpendicular to the X-axis is used. The two-dimensional position of the CCD sensors in the CCD sensor array is described herein by assigning XY positions when the level device  100  is level while the CCD sensor array is in the XY plane (reference position) and when the level device  100  is in a measurement position.  
         [0033]    The reference position may be stored in the level device  100  in a reference memory  151  as part of the manufacturing process. Thus, the level device  100  is affixed to a level structure which is positioned to be level. The level device  100  stores the state of selected CCD sensors in the CCD array  120  in response to a store first reference position signal. This is the reference position against which measurement positions are compared.  
         [0034]    In another embodiment, the level device  100  stores store a second reference position in the reference memory  151  in response to a store second reference position signal. The level device  100  is configured to use either the first or second reference position according to user input, such as a switch. For example, this capability may be used to store the position of an arbitrary orientation. When the second reference position is selected, the level device  100  indicates when the level device  100  is in that arbitrary orientation. Alternatively, the level device  100  provides measurements in degrees or radians, for example, relative to that arbitrary position.  
         [0035]    In one embodiment, a first column of CCD sensors and a second column of CCD sensors is used. Each of the CCD sensors in the first column of CCD sensors has the same X coordinate, X1, and a Y coordinate, Y1(m), where m is the number of the CCD sensor in the first column of CCD sensors sequentially numbered from the lowest to the highest Y-coordinate (as determined when the level device  100  is level). Each of the CCD sensors in the second column of CCD sensors has the same X coordinate, X2, and a Y coordinate, Y2(n), where n is the number of the CCD sensor in the second column of CCD sensors sequentially numbered from the lowest to the highest Y-coordinate (as determined when the level device  100  is level). The analysis circuit  150  determines m such that CCD sensor m is obscured and CCD sensor m+1 is exposed. Thus, the liquid profile  180  passes through the point between [X1, Y1(m)] and [X1, Y1(m+1)]. The analysis circuit  150  determines n such that CCD sensor n is obscured and CCD sensor n+1 is exposed. Thus, the liquid profile  180  passes through the point between [X2, Y2(n)] and [X2, Y2(n+1)]. One method to compute the angle is to assume the liquid profile  180  passes through the midpoint of the pairs of Y coordinates, Y1m(m,m+1) and Y2m(n,n+1). Thus, the angle, Θ, (relative from level) is computed as follows.  
       Θ   =     -       SIN     -   1            (         Y2m        (     m   ,     m   +   1       )       -     Y1m        (     n   ,     n   +   1       )           X2   -   X1       )                               
 
         [0036]    The resolution of the measurement depends on the density of CCD sensors in each column and the distance between each column. Denser positioning of the CCD sensors allows the position of the liquid profile to be more precise. A wider spacing of the two columns allows the angle to be determined more precisely.  
         [0037]    It will be apparent to one skilled in the art that the CCD array  120  may have numerous arrangements. For example, the CCD array  120  may include three or more columns of CCD sensors. In addition, numerous methods may be used to interpret the signals from the CCD array  120  to determine the liquid profile  180 . For example, pattern recognition techniques may be used.  
         [0038]    In one embodiment, the interpretation of the signals from the CCD array  120  includes the ability to respond to the detection of defective CCD sensors in the CCD array  120 . For example, alternative CCD sensors may be selected for use when the primary CCD sensors are determined to be defective. Alternatively, the analysis may recognize a degree of reduced accuracy due to defective CCD sensors. The ability to recognize and/or compensate for defective CCD sensors allows the use of CCD arrays with defective CCD sensors. This provides a use for CCD arrays that may otherwise be discarded.  
         [0039]    In one embodiment, the interior surface  190  is at a right angle to an interior surface  191 . A second CCD array is coupled to the surface of the interior surface  191  and a liquid profile  181  is defined at the interface between the liquid  110  and the interior surface  191 . The methods and apparatus described above are used to determine the orientation of the level device  100  relative to the line in the plane of the interior surface  191 . Thus, the orientation of the level device  100  may be determined in two-dimensions.  
         [0040]    In one embodiment, the exterior surface  195  of the container  170  is used to apply to the surface to be leveled (or whose orientation is to be measured).  
         [0041]    [0041]FIG. 2 illustrates one embodiment of a level of the present invention.  
         [0042]    A level  200  includes a level structure  210  and a level device  230 . The level structure has a surface  220  that is applied to the surface to be leveled (or whose orientation is to be measured). The level device  230  is mounted to the level structure  210  such that it indicates that it is level when the surface  220  is level.  
         [0043]    The level structure  210  includes a display  260  to provide a graphical and or numerical indication of the orientation. The level structure also includes a set of buttons  270  to provide user input to switch modes, activate functions, store reference positions, and hold measurements, for example. Other means of user input, such as switches, may be used.  
         [0044]    Numerous specific details are set forth in order to provide a thorough understanding of the described invention. Some of these specific details need not be used to practice the invention. In one embodiment, the liquid  110  is visible to the user through a window that includes graduation marks to provide for manual orientation readings as prior art level devices. Furthermore, the present invention is not limited to CCD arrays. Other radiation sensitive devices, such as a complementary metal oxide semiconductor (CMOS) image sensing array, may be used.  
         [0045]    In other instances, well-known structures, signals, and methods have not been shown in detail in order not to obscure the described invention. For example, a power source, such as a battery, is not shown in the figures.