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自动封皮检测系统Automatic envelope measuring systemABSTRACTA system for automatically measuring a clearance envelope about a path of travel in a specific embodiment includes a laser and a rotating reflector mounted on a moving vehicle for radially scanning the region around the path of travel in a direction generally perpendicular to the path of travel. A television camera is mounted on the vehicle and is responsive to light from the laser that has been reflected by objects located within the viewing field of the camera. The television camera is radially scanned and provides analog video signals representative of the radial distances between the reflector and the scanned objects. An analog video tape recorder is utilized to record on video tape the distance representative video signals together with binary codes or identification numbers identifying the camera radial scanning information. The video tape may be played at a central or home office where the distance representative analog video signals may be converted to digital computer compatible binary form for suitable processing and storing by the computer.AUTOMATIC ENVELOPE MEASURING SYSTEMBACKGROUND OF THE INVENTIONA. Field of the InventionThe present invention generally relates to measuring systems and, more particularly, to systems for determining an envelope, such as a clearance or maximum cargo envelope, about a path of travel, for example, a section of railroad tracks.B. Description of the Prior ArtA need exists for railroads to determine the maximum cargo size that may be transported on a railroad car along a section of railroad track or along a specific railroad route. This need particularly exists when it is desired to transport an oversize load on a railroad car. The clearance or maximum cargo envelope about the railroad track over a particular section or along an entire route must be known before an oversize load can be shipped without fear of damage.In the past, efficient, inexpensive and rapid systems have not been available for determining clearance or maximum cargo envelopes about sections of railroad tracks. Two prior art devices or systems are described in U.S. Pat. Nos. 3,168,023 (Harmony and 3,705,772: (Andreas). The device described in the Harmon patent utilizes a high pressure arc lamp mounted on a railroad vehicle for projecting a plane of light radially along the path of travel of the vehicle. A photographic camera having a wide angle lens is utilized periodically to photograph and record on a photographic film medium the obstacles along the path of travel illuminated by the plane of light. The resulting photographs may then be viewed on a calibrated viewing screen to determine the clearance envelope at the point where each photograph was taken.The device described in the Andreas patent utilizes a mobile computer controlled scanning system utilizing a light emitting diode and a rotating mirror to provide a radially directed rotating beam for illuminating objects along the path of travel. The computer controlled system collects the reflected light beam and ultimately generates binary data representative of the radial distances on a number of points along a preselected portion of each 360 sweep of the beam. The data for each sweep is compared by the mobile computer with the data obtained from successive sweeps. Normally, only the data representing the smallest distance along any radial line is stored by the remote computer and periodically placed on a suitable output medium for further processing by a centrally located computer.While these systems provide a way to determine clearance or maximum cargo envelopes about a path of travel, the photographic system requires each photograph to be individually viewed and the clearance envelope information provided by each photograph to be tabulated. Furthermore, obstacles located between the photographed areas will not be detected. These undetected obstacles can cause damage to a railroad cargo.The computer controlled system provides a more convenient way of collecting and tabulating the results of the radial distance measurements; however, the system is relatively complex and requires the use of a mobile computer to control the system and to process the data. Such mobile computers are relatively expensive and are subject to damage by the shock and vibrations often encountered on a railroad vehicle. Furthermore, the computer controlled system only stores and output sselected data, such as periodically determined minimum radial distance data, thereby limiting the flexibility of the system and precluding subsequent error checking of the data by comparing the results of successive scans.SUMMARY OF THE INVENTIONAn object of the present invention is to provide a new and improved envelope measuring system.Another object of the present invention is to provide a new and improved system for automatically measuring a clearance or maximum cargo envelope along a path of travel, such as a section of railroad tracks.Another object of the present invention is to provide a new and improved video system for measuring a clearance or maximum cargo envelope along a path of travel that provides an analog video tape record of the envelope suitable for subsequent processing by a centrally located digital computer.Another object of the present invention is to provide a new and improved video system for measuring a clearance or maximum cargo envelope along a path of travel that provides a complete record of all data obtamed.Another object of the present invention is to provide a relatively simple and inexpensive system for automatically measuring a clearance or maximum cargo envelope along a path of travel that does not require the use of a mobile computer.Briefly, in accordance with a preferred embodiment of the present invention, a source of coherent light is mounted on a railroad car and radially scans objects in the proximity of the road bed or tracks. The radially scanned light source is generated by a laser beam that emits a coherent infrared light beam along the direction of travel of the railroad car. The emitted light beam is radially deflected by a rotating mirror or other suitable reflector aligned with the emitted light beam for radially reflecting the emitted light beam in a direction perpendicular to the direction of travel of the railroad car to provide a helical scan of the region about the road bed or railroad tracks.A television camera is mounted on the railroad car in close proximity to the laser and receives light from the laser that has been reflected back to the camera by objects in the scanned area. The television camera is radially scanned and generates an analog video signal representative of the shape of the clearance envelope around the road bed. The clearance envelope may be displayed on a radially scanned monitor and is recorded on video tape for subsequent processing by a remote or centrally located digital computer. A binary code is assigned to each radial scanning line and recorded together with the analog video signal information to indicate the scanning direction corresponding to each line of recorded video information.A centrally located digital computer system advantageously processes the data recorded on the video tape by the mobile measuring system. The computer system includes a digital-to-analog converter for converting the analog signal recorded on the video tape to a binary signal usable for subsequent processing by the computer. The digital signals are stored in the computer which may be programmed to regenerate and display the clearance envelope at any desired location along a railroad route. Furthermore, the dimensions of any oversize load may be entered into the computer; and the computer programmed to display both the cross section of the load together with the clearance or maximum cargo envelope along a railroad route. Such a system permits an operator visually to determine whether the load can be safely transported along the selected railroad route. As a result, the most direct route over which an oversize load may be safely shipped can be determined quickly and inexpensively.BRIEF DESCRIPTION OF THE DRAWINGThe above and other objects and advantages and novel features of the present invention will become apparent from the following detailed description of a preferred embodiment of the invention illustrated in the accompanying drawing wherein:FIG. 1 is a block diagram of the mobile or vehicle carried portion of an envelope measuring and determining system constructed in accordance with the principies of the present invention;FIG. 2 is a block diagram of the centrally located portion of the measuring and determining system of FIG. 1;FIG. 3 is an illustration of the cross section of a railroad vehicle and its load or cargo;FIG. 4 is an illustration- of a clearance envelope as determined by the envelope measuring and determining system of FIG. 1; andFIG. 5 is an illustration of a composite display of a clearance envelope and vehicle and its cargo or load.DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, the mobile or vehicular portion of a clearance or maximum cargo envelope measuring system constructed in accordance with the principles of the present invention includes a radial scanning section 10 having a television camera 12, a continuous wave infrared laser 14 and a reflector or mirror 16 that is rotated at a variably controlled speed by a motor 18. The direction of emission from the laser 14 is along the direction of travel of the vehicle; and the mirror 16 is oriented at a 450 angle with respect to the direction of emission of the laser 14. The mirror 16 is rotated by the motor 18 about an axis of rotation parallel with the direction of travel of the vehicle and deflects the emitted laser beam perpendicularly to and radially about the path of travel of the vehicle. When the vehicle is stationary, the laser beam is deflected in a plane perpendicular to the direction of the tracks; and when the vehicle is in motion, the beam is helical in nature with the pitch of the helix being proportional to the speed of the vehicle. The pitch of the helix is also determined by the rotational speed of the mirror 16 which is controlled by the speed of the motor 18 under the control of a variable speed motor control 20. Consequently, the pitch of the helix and the ability of the scanning section 10 to detect small objects located between radial scans is controlled by controlling the speed of the vehicle and the rotational speed of the mirror 16. A lower safety limit on the rotational speed of the mirror 16 is imposed to prevent excessive laser beam power from being concentrated in any one area.The television camera 12 is chosen for its sensitivity to infrared radiation and is equipped with filters to attenuate undesirable background optical frequency radiation, such as light from street lamps and automobile headlights. In order to further reduce the effects of extraneous light on the operation of the television camera 12, the system according to the invention is preferably operated at night.The television camera 12 is swept in a radial mode by sweep signals applied to a pair of horizontal and vertical sweep inputs from sweep input lines 22 and 24, respeclively. The video output of the camera 12 is applied to a radially swept television monitor 25 and to the video input of an analog video tape recorder 29 by means of a multiplexer 30. The monitor 30 and the recorder 28 permit the operator of the system to record the analog video signal from the camera 12 for subsequent processing and evaluation and to visually monitor the signal as it is being recorded.The radial sweep signals for the camera 12 and the monitor 26 are synthesized from a pair of sinusoidally varying horizontal and vertical sweep components provided by a clock 32 that operates at 500kHz in a specific embodiment, an eight stage binary counter 34, a pair of read-only memories 36 and 38, a pair of digital-to-analog converters 40 and 42, and a pair of operational amplifiers 44 and 46 which are connected as Miller integrators. The outputs of the operational amplifiers 44 and 46 are connected to the horizontal and vertical sweep circuits by means of the lines 22 and 24, respeclively, to provide the horizontal and vertical components of the radial sweep to the horizontal and vertical deflection circuits of the camera 12. The output of the eight stage binary counter 34 is also applied to a parallel-to-serial converter 48 for application to the video tape recorder 28 via the multiplexer 30.The eight stage binary counter 34 counts clock pulses from the clock 32 and provides a zero to 511 count to the read-only memories 36 and 38. Hence, 512 different addresses (zero to 511) are generated by the binary counter 34, each of the binary addresses corresponding to a different one of 512 radial scanning lines for the television camera 12 and the monitor 26. Consequently,512 scanning lines are generated over the 3600 radial scan to provide a resolution of less than 10 per scan.More specifically, the binary numbers generated by the binary counter 34 are applied to the sine read-only memory 36 and the cosine read-only memory 38 to address specific address locations in each. The sine read-only memory 36 has stored in each of its address locations a binary representation of the sine of the angle of the scanning line represented by the value of the count from the binary counter 34. Similarly, each address location of the cosine read-only memory 38 has stored therein a binary value representing the cosine of the angle of the radial scanning line represented by the number in the binary counter 34. Consequently, the output of the read-only memory 36 is a series of binary numbers representative of the sines of each of the angles of each of the 512 radial scanning lines; and the output of the read-only memory 38 is a series of binary numbers representative of the cosines of the angles of each of the 512 radial scanning lines.The outputs of the read-only memories 36 and 38 are connected to the digital-to-analog converters 40 and 42 to convert the binary numbers from the read-only memories 36 and 38 to analog signals each having an amplitude corresponding to the value of the binary number from the read-only memories 36 and 38. Since the amplitudes of the output signals from the digital-to-analog converters 40 and 42 change only during the time the value of the count in the eight stage binary counter 34 is incremented, the output signals from the digital-to-analog converters 40 and 42 are a series of voltage steps approximating a sine wave and a cosine wave, respectively.The operational amplifier 44 is connected as an inverting amplifier, has a capacitor 50 connected between its input and output terminals and serves as a Miller effect capacitance multiplier. Consequently, the input capacitance of the amplifier 44-capacitor 50 combination is substantially equal to the capacity of the capacifor 50 multiplied by an amount proportional to the gain of the amplifier 44. Similarly, the input capacitance of the amplifier 46-capacitor 45 combination is substantially equal to the capacity of the capacitor 54 multiplied by an amount proportional to the gain of the amplifier 46.When signals are applied to the amplifiers 44 and 46 through a pair of resistors such as the resistors 52 and 56, each of the circuits operates as a nearly ideal integrator for integratrng the srgnais rrom the argttai-to-analog converters 40 and 42.The integrated signals from the amplifiers 44 and 46 are applied to the lines 22 and 24, respectively, and serve as the horizontal and vertical sweep signals for the，television camera 12 and the monitor 26. The amplifiers44 and 46 are reset at the beginning of each clock pulse so that the output from each of the amplifiers 44 and 46 is a series of variable slope ramps, the slope of each of the ramps being proportional to the amplitude of one of the voltage steps provided by the respective digital-to-analog converters 40 and 42. Since the output signals from the digital-to-analog converters 40 and 42 are stepped approximations of sine and cosine functions,respectively, the envelope of the variable slope ramp signal from the amplifier 44 varies as a sine function; and the envelope of the ramp signal from the amplifier 46 varies as a cosine function, thereby providing the desired radial sweep.In operation, as the measuring vehicle proceeds down. the tracks, the mirror 16 is rotated by the motor 18 and causes the laser 14 to scan the terrain in the proximity of the tracks. When an obstacle such as an obstacle 60 is encountered, a portion of the obstacle is illuminated by the laser beam. The illuminated area is viewed by the television camera 12.When the television camera 12 is properly focused and aligned with the laser 14, the illuminated spot on the obstacle 60 is projected onto an area on the target of the television camera vidicon that is displaced from the center of the target by an amount proportional to the radial distance between the rotating mirror 16 and the obstacle 60. Consequently, as the mirror 16 rotates, the area illuminated by the laser 14 progresses helically along the obstacle and provides an image on the target of the television camera vidicon having a shape similar to the shape of the cross section of the area between the rotating mirror 16 and the obstacle 60. If the vehicle were proceeding through a tunnel, the image projected onto the target of the television camera vidicon may be similar to the image shown in FIG. 4.A television camera vidicon has the characteristic that the beam current of the vidicon is relatively low when the target of the vidicon is not illuminated. As a result, when the scanning beam of the vidicon is swept along the target, very little beam current flows through the vidicon until an illuminated area is reached. At this point, the current through the vidicon increases, and the location of the illuminated portion of the target may be determined. In a typical television camera such as the television camera 12, a signal representative of the vidicon beam current is generated and amplified by video amplifier circuitry (not shown) to provide a video output signal that may be recorded by the video tape recorder 28.The system illustrated in FIG. 1 is designed so that the television camera 12 responds primarily to the output of the laser 14. As a result, the amplitude of the video signal from the camera 12 remains at a relatively low level until the portion of the vidicon target that is illuminated by the reflected light from the laser 14 is scanned. At this point, a sharp pulse is generated in the video signal, with the time interval between the initiation of the scan and the generation of the sharp video pulse being indicative of the radial distance to the obstacle 60. Since the vidicon has a certain amount of persistance, the rotation of the mirror 16 need not be synchronized with the radial sweep of the television camera 12.The output of the eight stage binary counter 34 is converted to serial form by the parallel-to-serial converter 48 and applied to the video input of the video tape recorder 28 to identify the radial line being scanned. The multiplexer 30 is synchronized to the clock 32 and causes the value of the count in the binary counter 34 to be recorded at the initiation of each radial scanning line, with the analog video signal from the television camera 12 being recorded for the remainder of the scanning line. Consequently, the information recorded by the video tape recorder 28 consists of a binary identification number for each of the 512 scanping lines followed by the analog video signal resulting from the radial scan along that line. Thus, the video data may easily be retrieved and processed since ea
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