MXPA98000763A - Method and apparatus to align follow up in opal communications inalambri - Google Patents

Abstract

The present invention relates to an optical communication system and methods wherein the reception source uses a set detector to retrieve data from a transmitted haptic and to evaluate alignment accuracy with the transmitted beam. The ensemble detector uses the principles of geometric invariance to determine the alignment accuracy. The detector can retransmit the recovered information to a system controller or other convenient device that can then relocate the receiver in a manner that properly aligns with the transmitter. The system and methods advantageously provide a more compact and robust communication system in which a single receiver element can be used for both alignment evaluation and data recovery functions.

Description

METHOD AND APPARATUS FOR ALIGNING FOLLOW-UP IN OPTICAL COMMUNICATIONS TNAT-AMRPTPAff BACKGROUND OF THE INVENTION This invention relates to optical communications and more particularly to a method and apparatus for tracking alignment in optical communication systems. Wireless optical base transceiver systems have provided revolutionary advances in the field of communications. These systems have increasingly become predominant and have been implemented for many practical applications. For example, optical communications are used for data collection functions such as video conferencing, email, fax, television, digital radio communications and a variety of network applications. The popularity of optical systems can be attributed to their numerous beneficial characteristics. The optical systems are wireless; in this way the physical installation is relatively simple. Interference and noise problems associated with other types of wireless communications have been substantially eliminated with the advent of optical systems. The total energy consumption for most optical systems is comparatively low. These and other benefits have made wireless optical components an increasingly popular communication technique. REF: 25367 A disadvantage of the existing wireless optical systems is the requirement that the transmission source is properly aligned with the receiving source. without proper alignment, the optical receiver can not effectively evaluate the optical beam to perform data recovery. The problem is exacerbated when there is substantial electrical noise in the environment that interferes with the optical receiver. This interference can trigger the system falsely to recognize an optical beam when in fact none has been transmitted. In contrast, systems that use physical equipment connections such as fiber optic systems do not require transceiver alignment. The transmitted wave simply follows the contour of the wire or cable or other transmission medium until it reaches the receiver. However, a wireless optical reception system having a very efficient correction mechanism will minimize alignment problems while retaining the remaining substantial benefits associated with wireless optical communications. Also, for maximum efficiency it is convenient to implement an optical system that can effectively process a low energy optical beam. With this system, low energy optical signals can be transmitted and decoded at the receiving end such that a minimum energy source is spent in the process. To perform these tasks, an optical communications system must be able to automatically realign the transmitter and receiver that, for whatever reason, have become misaligned. Unfortunately, current technology requires that multiple receiver elements be used for receiver realignment and data collection. The use of multiple elements, among other things, increases the cost and energy consumption while decreasing the overall efficiency of the system. As an illustration, a communication system with optical reception of the prior art uses a separate quadrant sensor, placed in the line of sight of the optical transmitter, to detect and correct alignment errors. The system also uses a collection lens to project the received beam onto a photodiode for data recovery. Disadvantageously, this approach requires at least three different elements (a quadrant detector, a collection lens and a photodiode) to implement the optical receiver of the system. In this way, multiple optical receiver elements are required to implement data recovery and tracking with directional precision, which complicates and increases the cost of the receiving system. Another disadvantage of this system is its inefficient use of transmitted optical energy. In particular, after evaluating the alignment accuracy of the transmitted beam, the quadrant sensor must then allow beam photons to pass through the detector to a second apparatus (collection lens and photodiode) for data recovery. The transmitted beam must contain enough signal energy to allow the beam to pass enough photons to the photodiode through a small opening in the quadrant detector. This configuration of the prior art imposes practical limits on the minimum achievable transmitted signal energy. While the discussion of additional disadvantages of this prior art approach is omitted, these will be apparent to those who practice the technique. Therefore, it is an object of the invention to provide a more compact and robust simplified method and apparatus for processing the received optical signals. Still another object of the invention is to provide a method and apparatus for using a simple optical receiver optical element to perform both data recovery functions and tracking accuracy evaluations. A further object of the invention is to provide a more efficient optical communication system that requires less energy consumption than existing systems.

COMPENDIUM OF THE INVENTION These and other objects of the invention are achieved in accordance with the principles of the invention by providing a method and apparatus employing a single detector assembly for receiving transmitted data and for determining tracking precision. The set detector, which is the main data recovery mechanism, receives an optical beam from a transmission source such that a projected image of the received beam is captured in the set. The projected image is compared to a predetermined image, to determine tracking precision of the received beam. Deviations between the projected image and the default image alert the system that a tracking error has occurred and corrective action can be initiated to realign the receiver with the transmitter based on the error. Additional characteristics of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS Figure la is a simplified representation of an optical communications system of the illustrative prior art.

Figure Ib is a front view of a quadrant detector of the prior art used in the optical communication system of Figure la. Figure 2a is a simplified representation of an illustrative embodiment of an optical communication system using a simple assembly detector, in accordance with the present invention. Figure 2b is a view of a set of light collection devices comprising the assembly detector of Figure 2a. Figure 2c is an orthogonal view of the assembly detector of Figure 2a. Figure 3 is a simplified representation of a technique for aligning illustrative tracking according to a preferred embodiment of the present invention. Figure 4 is a conceptual diagram illustrating geometric invariance with respect to various projected images with varying magnitude and direction. DESCRIPTION? pBFATTAnA OF THE PREFERRED MODAI.TDADKS The Figure illustrates a prior art system for receiving optical communications. The system in general is characterized by two transceiver stations placed at some spatial distance from each other. A transceiver station comprises a transmitter element 150 which includes the laser source 100 and the collimating lens 110. The collimation lens 110 produces a circular projection of the transmitted beam. The other transceiver station comprises a receiver element 160, which includes the photodiode 140 and the collection lens 120. An optical beam is transmitted from the laser source 100 in the dividing line of the receiving element 160. The collection lens 120 deflects the striking beam in photodiode 140 for further processing. Photons residing in the optical beam are used to transmit digital information to the receiver element 160. The photodiode 140 measures photon characteristics of the beam. These measurements are used to retrieve information conveyed from the transmitter element 150 to the receiver element 160. Typically, the presence or absence of a beam in a given time slot means either a logical zero or a logical one. To effect reliable data recovery, proper alignment is required between the transmission element 150 and the receiving element 160. Practitioners have conventionally deployed a quadrant detector ("quad" detector) 130 for this purpose. Figure Ib is an orthogonal view of the detector 130 of Figure 1, illustrating the circular opening 160 in which the optical beam passes through the detector 130 to contact the photodiode 140. The quad detector is based on four spatial quadrants 15 , 16, 17 and 18, to determine if the receiving element 160 (ie the collection lens 120 and the photodiode 140 of Figure la) are properly aligned with the laser source 100, in such a way that the precise transmission of the optical beam is effected. The impacting photons created by the optical beam cause charge to accumulate in the four spatial quadrants 15, 16, 17 and 18 of the quad detector 130 (Figure Ib). The optical system periodically measures the relative difference in charge concentration between diametrically opposed quadrants. For vertical alignment adjustments, the difference between the respective load concentrations in quadrants 17 and 18 is measured. Similarly, for horizontal alignment adjustments, the difference between the respective load concentrations in quadrants 15 and 16 is measured. These differences in cumulative charge between two quadrants are called the differential output. When the differential output is a zero, the charge concentration is uniform throughout the four quadrants, indicating that the receiver element 160 is properly aligned with the laser source 100. In the normal course of operation, the optical system periodically measures the two differential outputs. Based on these periodic measurements, the system intermittently realigns the receiving element 160 to maintain the value of the differential outputs close to zero. For quadrants 17 and 18, the magnitude of the differential output regulates the amount of vertical adjustment of the receiver element 160 required to restore proper alignment with the transmitted beam. Similarly, the measured differential output of quadrants 15 and 16 controls the required amount of horizontal adjustment. The differential output can be positive or negative depending on the selected reference frame for the measurements. If the differential output is positive or negative, the direction of the required adjustment is determined (ie left or right for horizontal measurements).; up or down for vertical measurements). In the exemplary quad detector of Figure Ib, the dial 17 receives a positive reference frame with respect to the dial 18 and the dial 15 receives a positive reference frame relative to the dial 16. If the load concentration in the dial 17 is greater than in quadrant 18, the system will measure a positive differential output. This means that a vertical adjustment ascending to the receiving element 160 is necessary. The amount of realignment required is proportional to the magnitude of the differential output obtained from quadrants 17 and 18. Horizontal alignment is achieved in a similar way. The system measures the difference between the load concentration in respective quadrants 15 and 16. If for example the measured concentration of the photons in quadrant 16 is greater than in quadrant 15, a negative differential output is obtained, which means that it is necessary a receiver setting to the left. The amount of horizontal receiver adjustment is directly proportional to the differential output obtained from quadrants 15 and 16. Based on the respective differential outputs obtained from the two pairs of quadrants, the optical communications system will trigger the realignment using some known method such as with physical actuators. While the system realigns the receiving element 160, with the transmission element 150, the photodiode 140 continues data recovery by detecting either the existence or absence of photons of the transmitted optical beam. The data recovery method is based on photons that are passed through the quad detector 130 through the aperture 146 to the photodiode 140. As previously explained, the communication technique of Figures la and Ib requires the use of multiple reception elements Optics to perform the dual tasks of data recovery and alignment tracking. Because the beam must be processed by a quad detector, and then passed through the collection lens for further processing, the use of multiple elements results in a less efficient use of the transmitted power. Using multiple elements also results in an optical communications system that is more bulky, more difficult to deploy in environments that have limited space, more expensive due to additional power consumption and the added cost of individual elements and less immune to electrical interference spurious. Additionally, when multiple elements work concurrently to provide both the data recovery functions and the necessary tracking alignment, alignment tracking can be a particularly slow process. The quad detector can also produce alignment errors where identical misalignments occur in the left and right quadrants and upper and lower quadrants, respectively. The present invention, described below in the context of the presently preferred embodiments, provides both a more compact approach to optical communications and a more efficient unitary use of transmitted energy. With reference to Figure 2a, a preferred transceiver assembly is illustrated in accordance with the present invention. A laser source 200 and a collimating lens 210 comprise the transmission element 250. The source 200 sends an optical beam using the collimating lens 210 to determine the circularity or degree of accuracy of the image. A single-set detector 225 comprises the receiver element. The assembly detector 225 generally comprises a set of light collection devices. Although it may comprise any convenient light collection device, the assembly detector 225 preferably comprises a set of photodiodes arranged in rows and columns. When photodiodes are employed as the light collection mechanism, each photodiode is considered to comprise an individual pixel in the detector of set 225. The output of each photodiode is typically coupled to an electronic control mechanism, the details of which are not critical to understanding the invention. The photodiodes comprising each pixel are used to detect the presence or absence of resident photons in a striking beam. This information in turn is used to establish the existence and shape of an optical beam transmitted in a manner that will be described below. Unlike systems of the prior art, wherein a collection lens 120 is required (see Figure 1), a collection lens does not need to be employed in the present invention. The optical beam on the contrary hits the assembly detector 225 directly, causing the image created from the laser source 200 to directly collimate in the detector 225. The system can then make alignment measurements and extract data when evaluating the illuminated image. in the assembly detector 225. Figure 2b is an illustrative view of the surface of the assembly detector 225 having a plurality of photodiodes 400 arranged in rows and columns as in some embodiments of the invention. In these embodiments, the 475 control system has a dedicated row direction and column address for each row and column of the set. By reference to a particular row address and row address, the control system 475 can read the output of the photodiode in the set. The row and column addresses may be stored in a memory 450 in the control system 475. In the illustration of Figure 2b, the control system 475 refers to a particular row direction and column direction to read the output in the photodiode 500 in the set. Figure 2c shows an orthogonal view of the assembly detector 225 in a flat rectangular shape. However, alternate forms of the assembly detector 225 can be contemplated. The data retrieval can be beneficially performed concurrently with the alignment analysis using the same set detector 225. In a preferred embodiment, there are discrete time slots where each time slot corresponds to a digital data value, i.e. a logical one or a logical zero. In this mode, the transmission of a beam in a time slot indicates the existence of a logical one. On the contrary, the absence of transmission in a time slot indicates the existence of a logical zero. Data according to this is retrieved as a digital bit per time slot. When a beam is transmitted from the laser source 200 (Figure 2a), the existence of photons that strike the line detector 225 impact areas which in turn establish the shape of the beam. The beam can be used for alignment evaluations (see below). The impact of the photons on the detector 225 also allows the system to extract data sent by the beam. Data can be recovered by adding, for each time slot, the net number of pixels in detector 225 that have been impacted by photons of the optical beam. Using this addition procedure, the transmitted information is collected for communication to a central controller or other designated location. The system controller then processes this information offline to perform data retrieval and tracking alignment functions. As such, the single set detector 225 advantageously performs the dual functions of aligning data tracking and retrieval. A preferred embodiment of the data recovery technique of the present invention utilizes a CMOS image detector as the set detector 225. A CMOS image detector comprises a plurality of photodiodes arranged in a row and column format, as the set illustrated in FIG. Figure 2b. Each photodiode comprises an individual pixel of the array detector 225. An advantage of using a CMOS image detector 225 over other devices such as a charge coupled device (CCD) is that it can read the output in individual pixels, thus significantly increasing data recovery times. Specifically, for each time slot, the image detector 225 measures the number of photons that impact each pixel located in the joint detector 225 as follows. The mechanism for system control preferably comprises a memory that stores row and column addresses as described above. The system controller addresses each pixel by choosing a particular column address and row address. Using these row and column addresses, the system controller reads the contents in each pixel output. The digital value of the pixel output will depend on the number of photons that have impacted that pixel during a particular time slot. In the case where a beam has been transmitted in that time slot, the concentration of photons in each photodiode will be high. Conversely, when no beam has been sent, the concentration of photons in each photodiode will be markedly lower. In this way some threshold amount of concentration of photons exists below which the output of the photodiode will have a first digital value and on which it will have a second digital value. When a high concentration of photons in a photodiode (indicating the presence of a beam) gives a second digital value in that pixel output, the system controller will place a flag to that pixel. Alternatively, when a lower concentration of photons in a photodiode produces a first digital value, the pixel is not flagged. The use of a CMOS image detector in this context has at least two advantages: (1) pixels not impacted by the optical beam are removed from the subsequent addition stage (see below); and (2) pixels that have been impacted by spurious electrical noise, but that have not been impacted by the optical beam, will not comply with the photodiode threshold (if the threshold was appropriately chosen) and are also not considered for addition. Next, the addition procedure described above is employed wherein the number of pixels with flag are summed with a system controller. If the sum total of the flagged pixels exceeds a second predetermined number or threshold, the system concludes that an optical beam has been transmitted (as opposed to no transmission or simply electrical interference without transmission) and accordingly assigns a one digital for that time slot. Conversely, if the total sum of pixels with flag does not exceed the predetermined threshold number, the system determines that no optical transmission has occurred and assigns a digital zero for that time slot. This summation procedure can occur for any number of time slots, and a digital information string of the transmission element 210 is obtained. Of course, the digital values can be inverted, where the presence of a beam on the contrary produces a zero digital, etcetera. The system controller can also record in memory the distribution of impacted pixels for alignment measurements (see below). In some embodiments, this information is stored only when the total sum of the impacted pixels meets or exceeds the predetermined threshold number. This preferred data recovery method using a CMOS image detector has distinct advantages. First, the image detector 260 significantly increases the speed of data recovery compared to previous methods. For example, conventional data recovery devices, such as coupled charge devices (CCD) used in instruments such as camcorders require reading the set of pixels before evaluating the individual pixels. This procedure results in comparatively long data recovery times. In contrast, the CMOS image detector 160 provides for the reading of individual pixels without requiring an evaluation of the entire assembly. Furthermore, unlike a system using a CCD, only those pixels selected by the image detector 160 need to be considered by the system controller. The remaining pixels are simply discounted from the addition stage. Therefore, the calculation time relating to the summing procedure is considerably faster than if all the pixels were added. Using this device, data recovery speeds of one Gpps or greater can be achieved. This data recovery time is comparable to or better than, optical communication techniques employing a quad detector. The use of a CMOS image detector provides greater benefits in terms of noise resistance. Spurious electrical transmissions that trigger minimal photon activity at a given pixel are easily discounted by the image detector. In this way, the noise effect is minimized, and more accurate data measurements are obtained. The above illustrations and each of the above techniques represent the preferred method of implementing data retrieval using the joint detector 225. Other techniques and equally suitable variations may be contemplated by those skilled in the art after a careful reading of this description. . For alignment measurements, the transmitted optical beam impacts the assembly detector 225 and thus illuminates an image in the detector 225. The preferred method for reading the individual pixel outputs described above is also employed by the system in determining the shape of a transmitted beam to perform aligned tracking. In particular, the system determines the shape of a striking beam by evaluating the number and position of pixels that have been impacted by photons. Preferably, information regarding the distribution of impacted pixels (which establishes the shape of the impacted image) is placed in a memory to wait for further processing. The system compares this illuminated image with a predetermined image, to determine if there are deviations between the two. The presence of deviations indicates that corrective measures must be taken to align the transmitter and the receiver. The magnitude and direction of the corrective measures are proportional to the amount of deviation of the illuminated image from the predetermined image. Advantageously, the information obtained during the data recovery process and specifically the information obtained from the image detector 260 with respect to each pixel, can also be used to measure alignment precision. For example, the shape of the image projected onto the detector 225 is determined based on the distribution of impacting photons in the assembly detector 225 as described above. The shape of this image gives important information regarding alignment accuracy (see below).

The assembly detector 225 determines if there is a misalignment between it and the transmission element 250. This determination is made unnecessarily by additional alignment detection structures. In determining alignment errors, the detector 225 provides necessary information to a system controller or other source. Using this information, the system can take corrective action to quickly restore proper alignment for continuous and accurate reception of transmitted data. The realignment mechanism of the present invention is based in part on the known principle of geometric invariance under perspective transformation. This principle decrees that a projected circle will form an image as a circle but if the image is projected orthogonally (this is perpendirly) with respect to the screen. In all other cases, the projected circle will form an image as an ellipse. In this way, when a cirr beam from a transmission source is projected under circumstances where the transmitter is not perfectly aligned with the receiver, the image will consequently appear as an ellipse to the transmission source. In addition, the specific contour of the ellipse conveys beneficial information regarding the nature and extent of the misalignment.

By applying this principle to the present invention, the orthogonal alignment between the transmitter element 250 and the assembly detector 225 results in the image formation of the collimated beam as a circle on the detector 225. In this way, when the detector 225 perceives a image-forming circle on it (ie using a CMOS image detector technique) alignment is considered correct, no corrective action is taken and data recovery is started as usual. When the projected image on the contrary appears as an ellipse, the system concludes that there is misalignment between the transmitter and receiver. The degree of divergence from the cirr shape and the shape of the projected image provide the system with information regarding the direction and extent of misalignment. Using this information, the system can adjust the alignment of the detector 225 in a manner proportional to the magnitude and direction of the misalignment of the optical beam. In this way, the simple projection of the beam formed in image on the reception detector 225, allows the system to take corrective measures in response to deviations in alignment. Associated with the ensemble detector, and contained within the system is a predetermined image for comparison with the image shocking detector. When a cirr beam is projected, for example the default image will be a circle. Other geometries are intended within the scope of the invention. Figure 3 is a conceptual diagram illustrating the use of geometric invariance in projected images. The image projected onto the assembly detector 325 is examined, and the extent to which the image of a circle is deflected is determined in both the horizontal and vertical directions. The drawers 345 represent orthogonal views of the assembly detector 325. The following alignment corrections by the system are proportional to the magnitudes of horizontal and vertical deviations of the cirr shape. In some embodiments, the physical actuators are used to realign the receiver with the transmitter. Figure 4 is a conceptual diagram illustrating geometric invariance with respect to several projected images of varying magnitude and direction. The circles labeled 501 represent an instance in time where the elements of transmission and reception are perfectly aligned. In this case, the composite image will result in circle 502 in which case no realignment by the system is required. The other circles 600 comprising the vertical and horizontal projected image are displaced from the center of the assembly detector. As such, each pair of these images (one vertical and one horizontal) represents individual instances at a time when the alignment is imperfect.

Depending on the magnitude of misalignment direction, the composite image will look like an ellipse rotated on a diagonal. The misalignment direction and direction are proportional to the degree of rotation of the composite image. In response to the shape and degree of rotation of the composite image, the system can then take corrective action to realign the receiving element with the transmitting element. Ambiguities of the detector 225 to interpret the alignment are solved initially by properly calibrating the system when installing. Initial calibration is necessary to avoid misalignment of the image by an amount identical to the left and right side of the projected image, which will otherwise cause misalignments due to the si- lerality of the right and left images produced. Likewise, initial calibration solves the problem that occurs when misalignment by an equal amount up and down results in similar ellipses causing similar images that otherwise result in ambiguities in alignment. An initial calibration of the system allows the misaligned image to be projected onto a different quadrant of the assembly detector, in such a way that bad alignments can be vividly distinguished from left to right and / or top to bottom. In this way, in the initial installation, the approximate location of the source is preferably evaluated, and a center is established with respect to the communications system. Based on this initial centering, the system can evaluate the resulting ellipse to determine the actual amount of displacement and, accordingly, make alignment corrections. In addition to projecting the beam as a circle, other shapes can be contemplated. The principle of geometric invariance dictates that a non-orthogonal projection of a beam having a predetermined shape will result in the beam hitting a source with a different shape. In this way, for example the practitioner can choose the shape of the beam as a rectangle, and then use the principles of geometric invariance and the present invention to evaluate the extent of misalignment at the receiving end by making the appropriate corrections. It will be understood that the foregoing is merely illustrative of the principles of the invention and that various modifications may be practiced by those skilled in the art without departing from the scope and spirit of the invention. All of these variations and modifications are intended to fall within the scope of the following claims. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (19)

1. CLAIMS 1.- An optical communications system, characterized in that it comprises: a transmission element and a reception element, the reception element comprises an assembly detector to determine the tracking accuracy of an optical beam transmitted from the transmission element and to detect data.
2. 2. The system according to claim 1, characterized in that the assembly detector comprises a CMOS image detector.
3. 3. A system for receiving optical communications to align beam tracking, characterized in that it comprises: a set detector for receiving an optical beam from a transmission source, wherein the system compares an illuminated image in the ensemble detector created by the impact of the optical beam with a predetermined image and wherein the system initiates corrective alignment between the transmission source and the ensemble detector upon detecting a deviation between the image and the predetermined image.
4. 4.- The system in accordance with the claim 3, characterized in that the predetermined image comprises a circle.
5. 5. - The system according to claim 3, characterized in that the magnitude of the corrective alignment is proportional to the amount of deviation between the image and the predetermined image.
6. 6.- The system in accordance with the claim 3, characterized in that data is transmitted from the transmission source to the overall detector, by selectively driving the optical beam over a plurality of time slots, the system records digital data during each time slot based on the transmission or absence of transmission of the optical beam during each time slot.
7. 7. The system according to claim 3, characterized in that the assembly detector comprises an image detector consisting of a set of photodiodes for detecting the presence or absence of a transmitted beam.
8. 8. The system according to claim 7, characterized in that the image detector comprises a CMOS image detector.
9. 9. The system according to claim 7, characterized in that the data is communicated over a plurality of time slots by the impact or lack of impact of the optical beam on the set detector, where the system adds up for each slot of time the number of pixels in the ensemble detector impacted by the beam, the impact of the beam on a pixel is represented by a first data value and the absence of impact is represented by a second data value.
10. 10. An optical communication system for evaluating alignment precision, characterized in that it comprises: a transmitter comprising a laser source for transmitting an optical beam; and a receiver comprising a set detector that receives the optical beam, the optical beam strikes the set detector, an image that is formed in the set detector by the impact of the optical beam, the image is used to determine whether the detector The set is aligned with the transmitter.
11. 11. The system according to claim 10, characterized in that the assembly detector comprises an image detector to sense the presence or absence of a transmitted beam.
12. 12. The system according to claim 10, characterized in that the set detector recovers data based on the presence or absence of a transmitted beam.
13. 13. An optical reception element, characterized in that it comprises an assembly detector consisting of a set of devices for light collection, the receiver element is used to recover data based on the presence or absence of an optical beam that impacts the detector of set and the receiver element used to measure alignment errors based on the shape of a striking optical beam.
14. 14. - The receiving element according to claim 13, characterized in that the receiving element comprises a CMOS image detector.
15. 15. Method for alignment tracking using an optical communication system, characterized in that it comprises the steps of: receiving an optical beam from a transmission source when the optical beam hits an assembly detector; compare the impacted image with a predetermined image; determine if there is a deviation between the images; and initiate corrective alignment based on a deviation between the images.
16. 16. The method according to the claim 15, characterized in that it further comprises the step of detecting data on a plurality of time slots based on the presence or absence of a striking beam during each time slot.
17. 17. The method according to claim 15, characterized in that the comparing step further comprises the steps of: adding the pixels in the overall detector that are impacted by the beam; compare the sum with a predetermined threshold number; and record the distribution of impacted pixels in a memory where the sum meets or exceeds the threshold number.
18. 18. - The method of compliance with the claim 16, characterized in that the comparison step further comprises the step of creating a projected image in the horizontal and vertical directions and combining the horizontal and vertical images to create a composite image.
19. 19.- The method according to the claim 17, characterized in that the addition stage includes the initial step of recording digital values at the output of each individual pixel.