Patent Publication Number: US-8111383-B1

Title: Portable laser surveillance method of a point on a target

Description:
BACKGROUND 
     Law enforcement personnel and private investigators conduct surveillance activities on people in order to document their specific activities. For the most part, a large volume of surveillance is conducted in the area of “rolling surveillance”. This type of surveillance is where the agent sits in a motor vehicle and watches out tinted windows of a mini van or other similar vehicle. Usually they are watching a residence or other structure from some distance away, waiting for the subject of interest to leave, come into view or conduct certain activities to be documented for later evaluation and/or prosecution. Law enforcement agents sit and watch for hours at a specific area, usually a door to a dwelling or a vehicle parked in the driveway waiting for activity or departure. This type of surveillance can go on for days causing eyestrain, fatigue and frustration. 
     Motion detection systems in use today are inaccurate over long distances for motion monitoring of a specific point on a specific target. Several systems offer sweeping detection of an entire area for the change in fields to detect movement. Some of these also have trigger mechanisms to start video recorders automatically. However, these devices are not self-contained and capable of being aimed or pointed at a specific target for detecting movement of a specific area only and generating a perceptible alert signal. 
     U.S. Pat. No. 6,700,528 to Christopher R. Williams relates to the detection of a wide area under observation. Specifically, ice flows in rivers or ice sheets or rubble fields. The portable laser device is mounted proximate the target surface with orientation to laterally and elevation to identify detection of movement. Therefore, this device is designed for the detection of a large area of mass including ice sheets flowing down rivers and the like. The system is then designed to contact a responsible party by means of cell phone signal or similar device. It is not designed to detect the specific movement of one small area not larger than 2 square feet. 
     U.S. Pat. No. 5,299,971 to Frank J. Hart describes an interactive tracking device for detecting intruders with a single quadruplex stationary passive infrared sensor. The sensor provides a signal to a microcontroller which drives a stepper motor to rotate additional sensors with narrower fields of view to more precisely determine the exact bearing of the intruder. When an intruder is verified, a camera and/or light are activated to record the intruder. This device is designed for a larger area and “sweeps” the covered area for movement and not designed to be aimed at a specific target of a small size to detect the precise movement necessary to avoid false alerts to the operator. 
     U.S. Pat. No. 5,299,971 to Frank J. Hart describes an interactive tracking device for detecting intruders with a single quadruplex stationary passive infrared sensor. The sensor provides a signal to a microcontroller, which drives a stepper motor to rotate additional sensors with narrower fields of view to more precisely determine the exact bearing of the intruder. When an intruder is verified, a camera or lights are activated to record the intruder. This device too is designed for a larger area and “sweeps” the covered area for movement and not designed to be aimed at a specific target of a small size to detect the precise movement necessary to avoid false alerts to the operator. 
     U.S. Pat. No. 5,757,004 to Donald R. Sandell &amp; Wade Lee May 26, 1998 describes a motion detector with a lens-sensor mounting and adjustment arrangement that permits a user to adjust the effective range of the motion detector without alerting the sensor&#39;s sensitivity settings. The mounting arrangement provides for relative movement of the sensor in relation to the lens matrix through an adjustment accessible to the user. The primary use of this device is to detect movement in an “area” covered in the field by the sensor such as a room or portion of an outside yard perhaps. The sensitivity setting or range is to shorten the distance of the effective range and not necessarily making it more pin-point. 
     In other words, if you were to take a flashlight beam that gets wider and wider as it travels from the source, you would be simply shortening the distance in which it illuminates without altering how sensitive it is. 
     U.S. Patent Application Publication US2002/0060737, 2002 to Chun-Hsing Hsieh &amp; Yuan-Jen Hsiao relates to the method of detecting motion for a digital camera. A method of detecting motion is described by capturing a first image and transferring it into a control device. This image is then stored with real-time gray scale values so that subsequent images taken can be compared to the first value to identify changes or movement. This device is not designed to be aimed at a specific target of small size. 
     Currently, law enforcement personnel conduct surveillance by simply watching their target. This is usually done from a safe distance with the help of binoculars, monocular, or some other similar instrument. This method of surveillance has multiple drawbacks. First of all, while watching their target, the surveillance personnel lose the ability to multitask. Secondly, the risk of missing an activity (at the target) becomes high when the personnel momentarily take their eyes off the target, or take a break. Third, through constantly monitoring the target, surveillance personnel can succumb to fatigue and frustration due to eye strain. 
     Hence, a strong need exists for a detection device that will consistently and accurately detect small movements on a target without continuous human monitoring. 
     SUMMARY OF THE INVENTION 
     A method for surveillance of a target which comprises the step of obtaining a portable device, which includes: a laser range finder operable for measuring distances between the laser range finder and a target, an alarm operable for generating a perceptible signal, and a microcontroller. The microcontroller is configured and arranged to receive an initial distance value and subsequent distance measurements from the laser range finder and compare the values wherein an alarm is triggered id the change in the values is within a specified range. Subsequent steps include statically positioning and operating the device to measure the distance to an object comprising a moveable obstruction to an ingress or egress and monitoring the generation of any signal by the device indicative of movement of the object to permit ingress or egress. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts one embodiment of the present invention wherein the portable laser device emits a laser beam to an obstruction object blocking a point of ingress or egress. 
         FIG. 2  is a flow diagram of the method of emitting the laser beam to a target. 
         FIGS. 3   A  and  3   B  depicts emitting a laser beam from a vehicle to an obstruction objected of a point of ingress or egress. 
         FIG. 4  is a front view of one embodiment of the portable laser device. 
         FIG. 5  is a rear view of one embodiment of the portable laser device. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     
       
         
           
               
             
               
                   
               
               
                 Nomenclature 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 10 
                 Portable Device 
               
               
                 12 
                 Housing 
               
               
                 20 
                 Laser Range Finder 
               
               
                 22 
                 Laser Diode Module 
               
               
                 24 
                 Photodiode 
               
               
                 26 
                 Laser Beam 
               
               
                 28 
                 Amplifier 
               
               
                 30 
                 Microcontroller 
               
               
                 40 
                 Alarm 
               
               
                 50 
                 Scope 
               
               
                 60 
                 Power Supply 
               
               
                 70 
                 User Interface 
               
               
                 72 
                 Power Switch 
               
               
                 73 
                 Three-Way Reset Switch 
               
               
                 74 
                 A/C Power Jack 
               
               
                 75 
                 D/C Power Jack 
               
               
                 76 
                 Distance Display 
               
               
                 77 
                 Calculation Button 
               
               
                 78 
                 Battery Compartment 
               
               
                 80 
                 Hand Grips 
               
               
                 100 
                 Ingress or Egress 
               
               
                 102 
                 Obstruction Object 
               
               
                 110 
                 Auxiliary Device 
               
               
                 112 
                 Camcorder 
               
               
                 114 
                 Computer 
               
               
                   
               
            
           
         
       
     
     As depicted in  FIGS. 1-5 , the invention is directed to a method of surveillance with a portable device  10  of a moveable obstruction object  102  to a specific point of ingress or egress  100  to a building or vehicle. The portable device  10  will emit a laser beam  26  to target the obstruction object  102 . The laser beam  26  measuring the distance from the portable device  10  to the obstruction object  102  is received back at the portable device  10 , amplified and sent to an internal microcontroller  30 . An initial distance value or reference value is stored within the electronic memory of the microcontroller  30 . Subsequent distance measurement values are received and read at the microcontroller  30 . If the change between the initial distance value and the subsequent distance measurement value is within the predetermined measurable range the microcontroller  30  will trigger an alarm  40 . This allows the user to not constantly focus on the obstruction object  102  when no activity is present and be alerted when a change within the specified range occurs. The laser range finder  20 , microcontroller  30  and alarm  40  are in electrical connection and encapsulated in a housing  12 . 
     As depicted in  FIG. 1 , the laser beam  26  is emitted from the portable device  10 . In the present embodiment the laser beam  26  targets the obstruction object  102  blocking a specific point of ingress or egress  100 . By aiming the laser at the obstruction object  102  the portable device will alert the user when a movement in the obstruction object  102  occurs. A user may monitor if a person enters or leaves a particular premises or vehicle based on the movement of the obstruction object  102 . The obstruction object  102  may include, but not limited to, a residential door or window, an overhead garage door or vehicle doors. Any barrier blocking the ingress or egress  100  of an establishment or vehicle may be monitored. A perceptible signal from the alarm  40  is triggered when activity is detected. The perceptible signal from the alarm  40  may be a visual, audio or vibrational alert to get the attention of the user that a change has occurred and human visual surveillance is suggested. 
     The portable device  10  is designed and encased in a plastic or metal housing  12  of sufficient strength durable enough to withstand transportation within a trunk of a moving vehicle. The portable device  10  is self-contained, not dependent on any other external devices for its surveillance operation. This allows for easy transportation, set-up and surveillance by a single user. 
     As depicted in  FIGS. 1-3   B , the laser beam  26  from the portable device  10  is focused on an obstruction object  102  blocking a specific point of ingress or egress  100 . The laser beam  26  monitors the obstruction object  102 . Movement of the obstruction object  102  blocking the ingress or egress  100  of a particular structure such as a building or vehicle may indicate that a person is entering or leaving. The alarm  40  alerts the user of movement of the obstruction object  102 . 
     The laser beam  26  is received using a photodiode  24 . A targeting scope  50  is used to focus the reflected portion of the laser beam  26  on to the photodiode  24  and the same scope  50  may be used to aim the laser beam  26 . The received signal goes through an amplifier  28  before going into the microcontroller  30 . The microcontroller  30  calculates if a change in distance from the portable device  10  and the obstruction object  102  has occurred. If such a change is detected and within a specified range the alarm  40  alerts the user. A band pass filter may be used to eliminate unwanted light reflected weakening the signal. 
     Several types of signals were considered for surveillance of the obstruction object  102 . Doppler radar was considered but the receiving antenna would have to be huge and cumbersome in order to receive a pin-point signal accurate to 900 feet. Image processing using still or video imagery were also considered. Although this method certainly has possibilities with the digital age it requires a unit to feed the signal into a control device such as a separate operational computer. Failure of a separate electrical component or a hard wired or wireless connection would then render the portable device  10  useless. 
     Furthermore, the portable device  10  is designed to be transported by a compact unit within a single housing  12  allowing for easier set up and transportation by a single user. A connection to a computer  114  or other auxiliary device  110  is an option available to the portable device  10  if the user wished to track data, but is not be required for operation. 
     In a first embodiment depicted in  FIGS. 1-3   B , the portable device  10  detects movement of the obstruction object  102  of the ingress or egress  100  by measuring the intensities of the reflected portions of the laser beam  26  and comparing them with a predetermined or calculated initial distance value or reference value. The laser range finder  20  includes a laser diode module  22  to emit the continuous modulating laser beam  26  at the obstruction object  102 . The reflected portion of the laser beam  26  is received at the scope  50  and focused on the photodiode  24 . Examples of a receiving photodiode  24  include, but are not limited to, a semiconductor diode which the reverse current varies with illumination, such as, an alloy junction photocell and the grown junction photocell. 
     The output signal of the receiving photodiode  24  enters the amplifying and filtering circuits through an amplifier  28 . For example, a trans-impedance amplifier converts current into voltage and amplifies it. The photodiode  24  is connected to the input of the amplifier  28 , which converts the current from the photodiode  24  into voltage. The output of the amplifier  28  may go through more amplification stages before being sent to the microcontroller  30  such as non-inverting amplifier stages used to increase the signal strength into the microcontroller  30 . Low and high frequency filters may be used to filter high frequency or ambient noise for a cleaner signal. 
     Subsequent distance measurement values are collected and sent to the microcontroller  30 . The intensity change between the reflected portion of the laser beam  26  and the reference value is calculated within the microcontroller  30 . If the intensity change is determined to be within the specified range the microcontroller  30  triggers the alarm  40 . 
     In the first embodiment the change in intensity is measured by the change in amplitude of the reflected portion of the laser beam  26 . The reflected portion of the laser beam  26  is read and sent to the microcontroller  30 , which compares its amplitude using an A/D converter. Examples of a microcontroller  30  functionality needed are serial communication, analog to digital conversion and adequate pins for triggering an auxiliary device  110 . An example of an industry available controller is Microchip&#39;s PIC16F877A microcontroller  30  utilizing an 11 MHz oscillator and a MAX232 for serial communication. Other microcontrollers  30  with comparable functionality may be used to perform the necessary calculations. In order to log the time and date into a computer  114  or other auxiliary device  110 , serial communication RS-232 using MAX232 chip may be used as the microcontroller  30  sends an array of characters through RS-232 to a communication port. 
     If the change in intensity is within a specified range the microcontroller  30  will trigger the alarm  40  alerting the user. A change in intensities that falls outside of the predetermined range may not trigger the alarm  40 . The microcontroller  30  will either ignore the change and continue monitoring the obstruction object  102  or stop emitting the laser beam  26  and trigger the alarm  40  to notify the user that surveillance is no longer being performed. 
     The initial distance value or reference value is calculated or manually entered into the microcontroller  30 . To calculate the reference value the microcontroller  30  may receive one measurement or a first set of initial measurements from the laser range finder  20 . From the first measurements the microcontroller  30  may calculate the average, determine the median or mode of the values. One example of a reference value is taking the reference measurement with the largest amplitude out of one hundred measurements. The process is repeated as desired with the largest amplitude selected. An average of the largest amplitude values is taken and stored within the memory function of the microcontroller  30 . Alternatively, a plurality of measurements over a time period may be averaged. For example, measurements are taken every 2 ms for 5 seconds and then averaged for the reference value. 
     Additionally, a single measurement value may be used. For example, a cycle of reference values may be used such that each measurement is compared to the measurement taken immediately prior. In such a case each first measurement is compared to the second subsequent measurement, the microcontroller  30  then uses the second subsequent measurement as the reference value and compares it the next subsequent measurement. In this case the reference value is constantly updated and the subsequent distance measurement is compared to measurement immediately preceding it. If the change in consecutive measurements falls within a specified range the alarm  40  is triggered. 
     Once an initial distance value or reference value is determined subsequent distance measurements are taken. The subsequent distance measurements may be a calculated average or a determined median or mode in the same manner as the initial distance value or reference value. 
     The microcontroller  30  compares the reference value and subsequent distance measurements which are a second set of measured values from the laser range finder  20 . The second set of measurement values are the values continuously read from the laser range finder  20  which will indicate if the position or distance to the obstruction object  102  has moved. The reference value from the reflected portion of the laser beam  26  and the subsequent distance measurements are compared in order to see if the difference is greater that a threshold or specified range stored within the microcontroller  30 . 
     The specified range may be entered into the microcontroller  30  indicting the range where the measurement must fall in order to trigger the alarm  40 . Buffer zones outside of the specified range indicate ranges where the microcontroller  30  ignores the measurements and does not trigger the alarm  40 . A specified measureable range is defined within the microcontroller  30 . In one example the buffer range is 0-0.5 V. The alarm  40  and/or the auxiliary devices  110  are triggered if the three consecutive second set measurements deviate from the reference value by more than the threshold of 0.5V, deviations of 0-0.5 V are ignored. Alternatively, the specified range could be set at a calculated distance range greater than 1 foot and less than 10 feet. This range is the approximate distance a door would open to allow a person to enter or leave while ignoring disruptions in the laser beam  26  from passing cars. Generally, the obstruction object  102 , a door in this example, is monitored from across a street or more than 100 feet away. By ignoring breaks in the laser beam  26  occurring over 10 feet from the obstruction object  102 , the user limits the potential false readings. 
     The obstruction object  102  to the a place of ingress or egress  100 , may include: a residential door such as a front, side or back door leading to a building, a window or garage door has been opened to allow a person or vehicle to exit. Movement of the obstruction object  102  is indicated by the changes subsequent distance measurements and the initial distance value or reference value. A vehicle or person may also have disrupted the laser beam  26  from contacting the obstruction object  102 , thus triggering the alarm  40 . A user will then make a visual inspection to determine if someone is entering or exiting the particular premises. Alternatively, buffer zones may be programmed to instruct the portable device  10  to ignore passing motorists or individuals. Disruptions in the laser beam  26  outside the specified range would not trigger the alarm  40 . This program may be especially beneficial if surveillance is done from across a busy street so the user would not be burdened by constant false alarms due to passing vehicles. 
     Selection of the wavelength to be used is an important part of the design. Since the portable device  10  is meant for surveillance, detection of the laser beam  26  may be a concern, thus the invisible infrared laser beam  26  is desirable for continuous surveillance. However, a visible laser may also be used to aim an invisible laser beam  26  or perform the actual surveillance depending on the user&#39;s needs. With an invisible infrared laser beam  26  a person can end up unknowingly looking into it for a long amount of time damaging the eyes and cause a safety concern. To address such safety concerns the microprocessor  30  may be programmed to stop laser emission or trigger the alarm  40  if any change is detected. Furthermore, the laser diode module  22  may be driven at less than 5 mW which is eye safe for public use. 
     The laser beam  26  may be a modulated continuous laser wherein the modulation is a low frequency sine wave. The laser diode module  22  is used to emit the laser beam  26  at the obstruction object  102  of an ingress or egress  100 . The emitted laser beam  26  is modulated and may be done by using a Schmitt trigger oscillator at a frequency of 5 MHz. The oscillator generates a square wave of 10V peak to peak amplitude. Output of the oscillator goes through a voltage dividing and biasing stage before being applied to the laser diode module  22  as a 1.8V-2.1V square wave. The modulation of the laser beam  26  is necessary to differentiate the reflected signal from common noise. Without modulation the reflected signal will be lost to common background noise making reading the signal difficult. For purposes of law enforcement or military surveillance an invisible emitted laser beam  26  is preferable. 
     The portable device  10  may also measure the distance to the obstruction object  102  using a time of flight laser measurement method. The time of flight ranging laser method uses lasers with short pulse duration and high peak power. It is commonly used for long distance measurement applications such as satellite and missile tracking and military range finding. These laser ranging systems are used to measure the distance between the source and a target. The time taken by the laser beam  26  to hit the obstruction object  102  and come back is measured. The velocity of light is converted to a distance from the portable device  10  to the obstruction object  102 . The change in distance from the reference distance and the obstruction object  102  is calculated by the microcontroller  30  and the alarm  40  is triggered if the change is outside a specified range. 
     In yet another embodiment, the distance may be measured by the portable device  10  through the triangulation method where the laser beam  26  is emitted and the reflected portion of the laser beam  26  is collected in a lens adjacent to the emission point forming a triangle wherein the distance to the obstruction object  102  may be calculated. 
     As depicted in  FIG. 1 , the scope  50  is detachably attached to the housing  12  and used for aiming the emitting laser beam  26 . The user may line up the laser beam  26  with the scope  50  and rely on the accuracy of the scope  50  to focus the invisible emitted laser beam  26 . The scope  50  is also used to focus the reflected portion of the laser beam  26  on to the photodiode  24 . From there the photodiode  24  reflected portion of the laser beam  26  goes through an amplification stage before going into the microcontroller  30  where it is compared against a reference value. 
     An auxiliary device  110  may be turned on, such as a camcorder  112  or computer  114  to log the date and time of the activity. Activity from other external auxiliary devices  110  would be left to the discretion of the user. 
     As depicted in  FIGS. 4-5 , the portable device  10  may be powered by a power supply  60 , such as a battery or an electrical connection. For example a 14.4V or 9V battery or 12 volts D/C and 110 volts A/C with and internal rechargeable battery with sufficient power so as to run the portable device  10  for a minimum of 3 hours. It will also have a 12-volt D/C power cord that will allow the portable device  10  to be powered by an auxiliary jack such as a cigarette lighter or D/C jack on a large power pack. A 110 volt A/C power cord may be included to allow the portable device  10  to be powered by A/C current when used with a power converter or when used inside a structure with standard A/C current. Both the A/C and D/C power cords will be of a plug in design so that they can be removed from the rear of the portable device  10  when they are not in use. 
     The portable device  10  has a user interface  70  to allow a user to operate and program as desired. A power switch  72  and a light or LED to indicate when the portable laser device  10  is powered is on the user interface  70 . Also available are two power jacks an A/C power jack  74  and a 12 volt D/C power jack  75 . A three-way reset switch  73  could allow the user to preset when the power jacks  74 ,  75  will have power. When the three-way reset switch  73  is in the “off” position, the two jacks  74 ,  75  will not have power at any time. When in the “switched” mode, the power jacks  74 ,  75  will only have power when the portable device  10  is on and in the set or surveillance mode or alerts. In this mode the power jacks  74 ,  75  will only get power when the portable device  10  triggers the alarm  40 . The third switching position of the three-way reset switch  73  is the “un-switched” position. In the “un-switched” position power is supplied to the two power jacks  74 ,  75  so long as the portable device  10  is connected to a power supply  60  regardless if the portable device  10  is set to surveillance mode or alerts. A distance display  76  may show the change in the distance from the portable device  10  to the obstruction object  102 . 
     As depicted in  FIG. 4 , the laser diode module  22  is in the center of the front of the housing  12 . The bottom of the portable device  10  may mount on a standard tripod or dash mounting bracket (not shown). Securing the portable device  10  when monitoring an obstruction object  102  allows for more accurate distance measurements. 
     The bottom of the portable device  10  may also have the battery compartment  78 . An auxiliary device  110  may be turned on, such as a camcorder  112  or computer  114  to log the date and time of the activity. Activity from other external auxiliary devices  110  would be left to the discretion of the user. 
     As depicted in  FIG. 5 , the rear of the portable device  10  may have the scope  50  in the center including cross hairs to position the emitted laser beam  26 . A calculation button  77  to aim the portable device  10  appears on the user interface  70 . The hand grips  80  on the left and right sides of the housing  12  may be designed as hand grips  80  for ease in holding and positioning the portable device  10 . A three-way reset switch  73  allows the operator to place the portable device  10  in an auto reset mode after an alert or manual reset mode requiring the operator to reset the portable device  10 . The auto reset mode allows the portable device  10  to reset in about five seconds after the portable device  10  returns to its pre-alert status. 
     The portable device  10  may be mounted onto a tripod or dash-mounting bracket (not shown) by means of the universal threads on the bottom of the portable laser device  10  or similar installation. The operator may mount the portable device  10  next to a camcorder  112 , computer  114  or other auxiliary device  110 . 
     In  FIG. 5 , a calculation button  77  on the user interface  70  of the portable device  10  would configure the reference values from the emitted laser beam  26  and set the parameters within the microcontroller  30 . A user would press the calculation button  77  and emit the laser beam  26  setting a default point. The calculation button  77  will be pressed to indicate that the reference value is entered and subsequent distance measurements will be made and movement of the obstruction object  102  will be indicated. The portable device  10  may be designed and programmed to alert when movement occurs at the obstruction object  102  to the point of ingress or egress  100 . 
     The foregoing discussion discloses and describes merely exemplary embodiments and aspects of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications, and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.