Viewpoint adjustment reference sample for line camera, uniform viewpoint adjustment device, and uniform viewpoint adjustment method

Abstract

To easily and efficiently perform viewpoint adjustment for a plurality of line cameras in an inspection device in a turbulent transmission optical system.SOLUTION: A viewpoint adjustment reference sample for a line camera that has a plurality of grooves in parallel with each other each having arc-shaped cross sections and being different in arc width, the grooves having the same depth and being vertical grooves, and a uniform viewpoint adjustment device and a uniform viewpoint adjustment method using the viewpoint adjustment reference sample for a line camera, are provided, thereby allowing an easy determination that a plurality of line cameras have the same degree of adjustment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a line camera viewpoint adjustment reference sample and a uniform viewpoint adjustment method for eliminating variations during the implementation of a line sensor using the line camera viewpoint adjustment reference sample, which are used for adjusting the viewpoints of a plurality of line cameras in a diffused transmission optical system when inspecting defects in a translucent inspection object such as a film or a sheet.

Background Art

[0002] In a translucent inspection object such as a film, transparent defects such as unevenness and fish eyes occur. To inspect the presence or absence of such defects, in an inspection apparatus with a diffused transmission optical system, line-shaped light is irradiated from a light source, and slit light with its spread restricted by a slit is irradiated onto the inspection object that moves.

[0003] Here, a diffused transmission optical system means reducing the variation in the direction in which light travels by inserting a slit, and refers to an optical system having a feature that the refraction of light when the light hits an uneven defect is emphasized. On the other hand, a direct transmission optical system means one that does not have a slit and applies all the light from the light source, and refers to an optical system in which the refraction of light is difficult to distinguish even when the light hits an uneven defect. Therefore, in the inspection with a direct transmission optical system, there are cases where defects cannot be found.

[0004] A plurality of line cameras arranged linearly so as to face the light source across the inspection object image the light transmitted through the inspection object that moves. Based on the image data output from these line cameras, the presence or absence of defects in the inspection object is determined. When a defect is detected, the position, shape, etc. of the defect are specified.

[0005] Therefore, it is necessary to mount a plurality of line cameras. Depending on the sensors of the line cameras, there may be individual variations, and it is necessary to adjust them to a uniform and identical degree of adjustment. The line cameras are adjusted so that the degree of adjustment reaches the same detection level.

[0006] For example, even if the position of the line camera shifts during the installation or use of the inspection device, the detection level may change, and there is a risk that uniform detection cannot be achieved.

[0007] Further, in Patent Document 1, in order to easily grasp the positional deviation of the line camera, the position of the light source is adjusted, and based on the output values of the line sensor cameras at their respective positions, it is determined whether the position of the line sensor camera is appropriate. If the position of the line sensor camera is not appropriate, the operator adjusts the positions of the light source and the line sensor camera.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In the above inspection device, in order to confirm the sensitivity of the inspection device, an actual defect is arranged at the scanning position, the inspection waveform is measured with an oscilloscope or the like, and the S / N and the signal level are measured. Then, the light source is moved and its position is adjusted to determine whether the line sensor camera is misaligned, and based on the determination, the position of the line sensor camera is adjusted.

[0010] Therefore, especially when a large number of actual machines are installed, the position setting of the sensor is only calculated by the ratio to the output value to calculate the edge amount, there is no index as a reference for adjustment, and it takes time for adjustment.

[0011] Also, since it is based only on the value of the light reception amount, variations are likely to occur in the adjustment, and there are cases where it is not performed appropriately. For this reason, when using a plurality of line cameras, it has been difficult to adjust them uniformly.

[0012] It is necessary to search for defects that result in a light reception amount near the threshold value in an actual inspection. Moreover, it is unclear whether the detected defects necessarily emit a standard light reception amount, leading to trial-and-error adjustments. As a result, there was a problem in that the perspective adjustment of multiple line cameras could not be efficiently performed.

[0013] Therefore, an object of the present invention is to provide a perspective adjustment reference sample for a line camera, a perspective adjustment device using the perspective adjustment reference sample, and a uniform perspective adjustment method that can easily perform adjustment on an actual machine when uniformly adjusting the perspectives of multiple line cameras in a diffusive transmission optical system.

[0014] Also, an object of the present invention is to provide a perspective adjustment reference sample and a uniform perspective adjustment device and a uniform perspective adjustment method using the perspective adjustment reference sample that can easily adjust the perspectives of multiple line cameras with individual variations during the design, inspection, installation, mounting, and maintenance of an inspection device.

[0015] Another object of the present invention is to provide a perspective adjustment reference sample for a line camera, and a uniform perspective adjustment device and a uniform perspective adjustment method for a line camera that determine the degree of adjustment based on a light amount waveform by using the perspective adjustment reference sample for the line camera.

Means for Solving the Problems

[0016] To achieve the above object, as a first invention, a perspective adjustment reference sample for a line camera is provided, in which a plurality of grooves with an arc-shaped cross-section and different widths of the arcs are provided in parallel, the depths of the grooves are the same, and the grooves are vertical grooves.

[0017] Further, as a second invention, a line-shaped light source that irradiates light on a translucent inspection object, a plurality of line cameras that are arranged in a line so as to face the light source with the inspection object interposed therebetween and image the light transmitted through the moving inspection object, and a slit that cuts off the spread of light from the light source, and a uniform viewpoint adjustment device for line cameras that determines the degree of adjustment of the viewpoints of the plurality of line cameras using a viewpoint adjustment reference sample of the line cameras.

[0018] Further, as a third invention, a uniform viewpoint adjustment device for line cameras is provided, in which the viewpoint adjustment reference sample of the line cameras is installed at the work position at an angle with respect to the moving direction of the inspection object.

[0019] Further, as a fourth invention, a uniform viewpoint adjustment device for line cameras is provided, which includes an installation jig for installing the viewpoint adjustment reference sample of the line cameras at the work position at an angle with respect to the moving direction of the inspection object.

[0020] Further, as a fifth invention, a line-shaped light source that irradiates light on a translucent inspection object, a plurality of line cameras that are arranged in a line so as to face the light source with the inspection object interposed therebetween and image the light transmitted through the moving inspection object, and a slit that cuts off the spread of light from the light source, and a uniform viewpoint adjustment method for line cameras that adjusts the degree of adjustment of the viewpoints of the plurality of line cameras using the viewpoint adjustment reference sample of the line cameras.

[0021] Furthermore, as a sixth invention, a line-shaped light source that irradiates light on a translucent inspection object, a plurality of line cameras that are arranged in a line so as to face the light source with the inspection object interposed therebetween and image the light transmitted through the moving inspection object, and a slit that cuts off the spread of light from the light source, and a uniform viewpoint adjustment method for line cameras that measures the light reception amount waveforms of the plurality of line cameras respectively using the viewpoint adjustment reference sample of the line cameras and adjusts the degree of adjustment of the viewpoints of the line cameras.

Advantages of the Invention

[0022] According to the present invention, by using the viewpoint adjustment reference sample of the line camera, the viewpoint adjustment of a plurality of line cameras can always be adjusted based on the same standard.

[0023] Also, by grasping the adjustment degree of the line camera at the time of designing the inspection apparatus and performing the viewpoint adjustment of a plurality of line cameras at the time of setting, it is possible to adjust a plurality of line cameras to the same performance without variation. Further, at the time of inspection of the inspection apparatus that is periodically performed, when the inspection apparatus is installed at the installation destination, and further at the time of maintenance after a certain period has elapsed, the viewpoint adjustment of the plurality of line cameras can be easily adjusted to the same state, so that the inspection accuracy of the inspection apparatus can be maintained the same and the reliability of the inspection apparatus can be enhanced.

[0024] Further, the present invention can provide a uniform viewpoint adjustment apparatus and a uniform viewpoint adjustment method for a line camera that discriminates the adjustment degree based on the light amount waveform by using the viewpoint adjustment reference sample of the line camera.

Brief Description of the Drawings

[0025]

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Mode for Carrying Out the Invention

[0026] (Line camera perspective adjustment reference sample) The line camera perspective adjustment reference sample of the present invention will be described.

[0027] FIG. 1 is a perspective view of the line camera perspective adjustment reference sample of the present invention, and FIG. 2 shows a cross-sectional view of the groove of the line camera perspective adjustment reference sample of the present invention.

[0028] In FIG. 1, 1 is the line camera perspective adjustment reference sample of the present invention. 2, 3, and 4 are grooves provided in the line camera perspective adjustment reference sample 1, respectively. These grooves 2, groove 3, and groove 4 are grooves having an arc-shaped cross-section with different widths of the arcs, and the respective grooves are provided in parallel, the depths of the grooves are the same, and the grooves are vertical grooves.

[0029] For example, what is shown in this embodiment is a line camera perspective adjustment reference sample in which the line camera perspective adjustment reference sample 1 is made of acrylic resin (colorless and transparent) (50 mm long, 70 mm wide), the width of groove 2 is 20 mm, the width of groove 3 is 10 mm, the width of groove 4 is 5 mm, and the depth of each of grooves 2, 3, and 4 is 5 mm.

[0030] This line camera perspective adjustment reference sample has no particular limitation in terms of size, and the width and depth of the groove are not limited to these.

[0031] However, by making the widths of at least the grooves 2, 3, and 4 different from each other, the peak values of the light quantity waveform (contrast difference, light and dark difference, intensity difference) can be clearly detected. Based on these contrast differences, the degree of viewpoint adjustment of the line camera can be adjusted.

[0032] Also, along with the viewpoint adjustment of the line camera, the position adjustment of the slit can also be performed.

[0033] Also, regarding the depths of the grooves 2, 3, and 4, by making them the same, the peak value of the light quantity waveform can be changed depending on the difference in the widths of the grooves.

[0034] In the case of this embodiment, regarding the size of the width of the groove, groove 2 > groove 3 > groove 4 Therefore, the peak value of the light quantity waveform is the peak value of the portion of groove 2 < the peak value of the portion of groove 3 < the peak value of the portion of groove 4.

[0035] Generally, the peak value of a groove with a larger width is smaller than the peak value of a groove with a smaller width.

[0036] (Schematic of the inspection device) Here, the schematic of the inspection device will be described.

[0037] FIG. 3 is a diagram showing a schematic configuration of an inspection device according to an embodiment of the present invention, and FIG. 4 is a plan view showing the positional relationship between a plurality of line cameras and a light source.

[0038] In FIG. 3, reference numeral 5 denotes an object to be inspected, which inspects defects in a film, sheet, or the like having translucency. The object to be inspected 5 is moving from left to right as indicated by the arrow in FIG. 3.

[0039] Reference numeral 6 denotes a light source that irradiates light. Reference numeral 7 denotes a line camera, and reference numeral 8 denotes a slit.

[0040] As shown in Fig. 3, the inspection apparatus includes a linear light source 6 that irradiates light onto a test object 5 having translucency such as a film or a sheet, a plurality of line cameras 7 that are linearly arranged so as to face the light source 6 with the test object 5 interposed therebetween and image the light transmitted through the moving test object 5, and a slit 8 that cuts off the spread of the light from the light source 6.

[0041] Regarding the slit 8, an edge is provided at the tip. The intensity of stray transmission can be changed depending on the insertion state of the slit 8, and the appearance of the defect will also change significantly.

[0042] As the light source 6, an LED, a fluorescent lamp, a halogen lamp, etc. are used, and the light source 6 mounted in the case 9 is arranged in the longitudinal direction orthogonal to the moving direction of the test object 5. The case is housed and fixed in a cabinet (not shown). The lighting of the light source 6 is controlled to irradiate light toward the test object 5 moving upward.

[0043] Above the light source 6, a slit 8 with a knife-edge-shaped tip is arranged in the longitudinal direction so as to cover a part of the light source 6. When viewed from above, the slit 8 covers the downstream half of the light source 6 in the moving direction of the test object 5.

[0044] As a result, a part of the light emitted from the light source 6 is cut off by the slit 8, and a stray transmission optical system is configured. In this optical system, by inserting the slit 8, the variation in the direction in which the light travels can be reduced, so the refraction of the light when the light hits a defect with irregularities is emphasized. Therefore, since the defect appears clearly, it is suitable for detecting defects such as irregularities and fish eyes.

[0045] A part of the light from the light source 6 is cut off by the slit 8, and the light that is not cut off passes through the moving test object 5. The light transmitted through the test object 5 is captured by the line camera 7, and the test object 5 is imaged. If there is a defect in the test object 5, the transmitted light is scattered, so the amount of light received by the line camera 7 changes. The line camera 7 outputs the image data of the captured test object 5.

[0046] The line camera 7 is composed of, for example, a CCD camera or a CMOS camera. A plurality of line cameras 7 are arranged above the light source 6, and each line camera 7 is arranged in a row in the longitudinal direction and attached to the pedestal 10. The pedestal 10 is housed in a cabinet and is movably attached. In order to adjust the viewpoint position of the line camera 7, it is performed using the viewpoint position adjustment sample 1.

[0047] In the inspection apparatus, in order to reliably and stably detect the defect of the object to be inspected 5, the detection level must be maintained constant. Therefore, the line camera 7 is adjusted and maintained at the same level. Since a plurality of line cameras 7 are installed, adjustment of each line camera 7 is required.

[0048] As shown in FIG. 5, at the work position through which the moving object to be inspected 5 passes, the viewpoint position adjustment sample 1 is installed so as to be inclined with respect to the moving direction of the object to be inspected 5. The grooves 2, 3, and 4 are inclined with respect to the longitudinal direction of the light source 6 and face each other.

[0049] This inclination angle is set to be from 5° to 30°, and preferably about 10° is good. The inclination angle can be adjusted as appropriate.

[0050] When the light source 6 irradiates light in this state, the light restricted by the slit 8 hits the grooves 2, 3, and 4 and is refracted, and the light transmitted through the viewpoint position adjustment sample 1 is taken into the line camera 7.

[0051] Specifically, in FIG. 5, the boundary between the edge portion of the slit 8 and the light source 6 and the contact point with the viewpoint position adjustment sample 1 of the line camera of the present invention are a, i, u, e, o, ka, ki, ku indicated by.

[0052] Each point indicates the following part in the viewpoint position adjustment sample of the line camera of the present invention.

[0053] a - i Flat portion Arc portion of groove 2 Upper flat portion Arc portion of groove 3 Lower flat portion Arc portion of groove 4 Flat portion Fig. 6 shows the output waveform of the light quantity along the scanning line in the output data. Corresponding to the three grooves 2, 3, and 4, output waveforms of three peak values appear. And at each position corresponding to the vicinity of the edges on both sides of the grooves 2, 3, and 4, it becomes the minimum peak of the darkest part or the maximum peak of the brightest part. Since the waveform height of the peak is larger than that of the minimum peak, it is preferable to manage the adjustment condition based on the maximum peak value of the viewpoint position adjustment sample 1.

[0054] Fig. 6 is a diagram showing the output waveform (contrast) when inspecting the viewpoint adjustment reference sample of the line camera, and shows the light reception amounts of the line camera at the respective points (A, I, U, E, O, K, I, K).

[0055] The peak value at point I is shown as 100%.

[0056] By adjusting a plurality of line cameras so that the output waveforms (contrasts) of these light reception amounts are the same, it becomes an index for determining whether the line cameras are adjusted to have the same performance.

[0057] (1. Adjustment at the time of reference setting) First, at the time of inspection serving as the reference of the inspection device, the output waveform of the light reception amount is adjusted and measured.

[0058] Based on this output waveform, at the time of shipment, installation, and maintenance of the inspection device, the position of the line camera 7 using the viewpoint position adjustment sample 1 is adjusted.

[0059] Also, at the time of shipment, installation, and maintenance of the inspection device, the line camera is adjusted so as to be the same as the light reception amount waveform at the time of inspection.

[0060] That is, at the time of the new order inspection, the output waveform of the light reception amount is surely acquired by using the viewpoint adjustment reference sample 1 of the line camera of the present invention.

[0061] This inspection is repeated to confirm the reproducibility of the output waveform of the light reception amount, and basic test data for adjusting a plurality of line cameras to have a uniform viewpoint is acquired.

[0062] In order to adjust the line camera, a precision stage is attached to the camera pedestal 10 in advance.

[0063] In order to adjust the position of the line camera 7, a moving part is provided on the pedestal 10 of the line camera 7, which is an electric stage such as a precision stage for example, and the moving part is actuated by a command signal from the adjustment part, and the position of the pedestal 10 is finely adjusted.

[0064] Note that the position of the pedestal 10 may be manually finely adjusted by using a manual stage.

[0065] (2. Adjustment at the time of shipment) Next, at the time of shipping the actual machine, the inspection is performed by installing the viewpoint adjustment reference sample 1 of the line camera so as to be inclined with respect to the moving direction at the work position where the inspection object 5 is located, and the test data obtained by imaging the transmitted light of the viewpoint adjustment reference sample 1 of the line camera and the data at the time of shipment are compared, and the adjustment of each line camera is performed so that the viewpoint positions of the line cameras 7 become uniform according to the comparison result.

[0066] (3. Adjustment at the time of installation) Also, when the actual machine is installed, the inspection is performed by installing the viewpoint adjustment reference sample 1 at the work position so that the viewpoint adjustment reference 1 of the line camera is inclined with respect to the moving direction of the inspection object 5, and the test data obtained by imaging the transmitted light of the viewpoint adjustment reference 1 of the line camera and the installation data are compared, and the line camera 7 is adjusted and installed according to the comparison result.

[0067] (4. Adjustment during Maintenance) Furthermore, during the maintenance of the actual machine, when adjusting the perspective of the line camera, the perspective adjustment reference sample 1 of the line camera is placed at the work position so that the perspective adjustment reference 1 of the line camera is inclined with respect to the moving direction of the inspection object 5, and the inspection is carried out. The test data obtained by imaging the transmitted light of the perspective adjustment reference 1 of the line camera is compared with the maintenance data, and maintenance adjustment is executed to adjust each line camera so that the perspective positions of the line cameras 7 become uniform according to the comparison result.

[0068] In the sample inspection process, using an existing defect inspection device, the perspective adjustment reference sample 1 of the line camera is placed at the work position in an inclined manner, and a new inspection of the perspective adjustment reference sample 1 of the line camera is carried out. The image data of the line camera 7 is output to the inspection unit, image processing is performed, and output data is generated. This test data is stored in a storage unit such as a memory, HDD, or SSD.

[0069] Next, the test data is repeatedly acquired, and similarly, the perspective adjustment reference sample 1 of the line camera is placed at the work position in an inclined manner, and the inspection is carried out multiple times.

[0070] Each time the inspection is carried out and the test data is generated, the adjustment unit compares the test data with the data at the time of shipment to confirm that there is no difference between the data at the time of shipment and the test data.

[0071] That is, the output value (maximum peak value) of the large defect in the test data as shown in FIG. 7 and the output value (maximum peak value) of the large defect in the data at the time of shipment, and the output value (maximum peak value) of the medium defect in the test data as shown in FIG. 8 and the output value (maximum peak value) of the medium defect in the data at the time of shipment are compared, and it is checked whether the difference is within the threshold value (3%). When the output values of all the test data are within the threshold value, the adjustment unit determines that there is no difference between the test data and the data at the time of shipment. Thereby, the reproducibility of the test data is confirmed.

[0072] Here, in order to improve the accuracy of inspection during adjustment, it is necessary to install the line camera's viewpoint adjustment reference sample 1 at a predetermined work position. Therefore, as shown in FIGS. 9 and 10, an installation jig 11 is used to install the line camera's viewpoint adjustment reference sample 1 at an inclined position at the work position of the actual machine. The installation jig 11 holds the outer peripheral edge of the line camera's viewpoint adjustment reference sample 1 and is detachably attached to the case 9 of the light source 2 by the support 12 of the installation jig 11.

[0073] At the time of shipment, in the manufactured actual machine, using the installation jig 11, the line camera's viewpoint adjustment reference sample 1 is installed at an inclined position at the work position, and inspection is performed. The adjustment unit compares the test data with the shipment data and checks whether the difference between the output value of the test data and the output value of the shipment data is within the threshold value. This check is performed in the same manner as the confirmation method during the repeated inspection in the sample inspection process. When the difference in the output value is within the threshold value, it is considered qualified and no adjustment is made. When the difference in the output value is greater than or equal to the threshold value, it is considered unqualified, and the position of the line camera 7 is adjusted.

[0074] The adjustment unit analyzes the shipment data that has become unqualified, identifies the shipment data corresponding to the unqualified output value and the difference therefrom, and determines the adjustment condition. A table storing data related to the position direction and movement amount of the line camera 7 corresponding to the identified defect and difference is stored in the storage unit, and the adjustment condition can be determined by referring to the table. The adjustment unit outputs a command signal based on the determined adjustment condition to the moving unit. The moving unit operates to adjust the position of the line camera 7. After the adjustment, inspection is performed again, and the pass / fail is determined. When it passes, the installation jig 11 is removed, and the manufactured actual machine is shipped.

[0075] When the actual machine is delivered and installed at the site, adjustment during installation is performed using the line camera's viewpoint adjustment reference sample 1. The adjustment during installation is performed in the same manner as the adjustment at the time of shipment.

[0076] Furthermore, during maintenance while the actual machine is in use, adjustments during maintenance are also made using the line camera viewpoint adjustment reference sample 1, and the adjustments during maintenance are performed in the same manner as the adjustments at the time of shipment.

[0077] However, the threshold value (1%) during the adjustment process at the time of maintenance is set higher than the threshold value (3%) during the inspection process at the time of shipment.

[0078] As described above, by performing the adjustment using the line camera viewpoint adjustment reference sample 1, the adjustment check at the time of shipment, the adjustment check at the time of installation, and further, the adjustment check at the time of maintenance can be easily performed, and the variations among multiple line cameras can be eliminated, enabling uniform viewpoint adjustment to be performed based on the same standard.

[0079] Therefore, the inspection accuracy of the defect inspection device can be maintained, and the reliability can be enhanced.

[0080] Also, by installing the line camera viewpoint adjustment reference sample 1 at an inclination, the peak of the output waveform with respect to the defect becomes clear, the defect can be surely detected, and the influence of the positional deviation of the line camera 7 can be accurately recognized.

[0081] Moreover, by changing the installation angle or shifting the installation position of the line camera viewpoint adjustment reference sample 1, the data from the line camera 7 can be set according to the inspection device.

[0082] It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that many modifications and changes can be made to the above-described embodiments within the scope of the present invention.

Explanation of Reference Numerals

[0083] 1 Line camera viewpoint adjustment reference sample 2 Groove 3 Groove 4 Groove 5 Object to be inspected 6 Light source 7 Line camera 8 slits 9 cases 10 pedestals 11 installation jigs 12 supports

Claims

1. A reference sample for viewpoint adjustment of a line camera, characterized in that a plurality of grooves having an arc-shaped cross section and different widths of the arcs are provided in parallel, the depths of the grooves are the same, and the grooves are vertical grooves.

2. An inspection apparatus comprising: a line-shaped light source that irradiates a light-transmissive inspection object with light; a plurality of line cameras that are arranged in a line so as to face the light source with the inspection object interposed therebetween and that image light transmitted through the moving inspection object; and a slit that cuts off the spread of light from the light source, A uniform viewpoint adjustment device for a line camera that determines the degree of adjustment of the viewpoints of a plurality of line cameras using a reference sample for viewpoint adjustment of the line camera.

3. The uniform viewpoint adjustment device for a line camera according to claim 2, wherein the reference sample for viewpoint adjustment of the line camera is installed at a work position at an angle with respect to the moving direction of the inspection object.

4. The uniform viewpoint adjustment device for a line camera according to claim 2, further comprising an installation jig for installing the reference sample for viewpoint adjustment of the line camera at a work position at an angle with respect to the moving direction of the inspection object.

5. An inspection apparatus comprising: a line-shaped light source that irradiates a light-transmissive inspection object with light; a plurality of line cameras that are arranged in a line so as to face the light source with the inspection object interposed therebetween and that image light transmitted through the moving inspection object; and a slit that cuts off the spread of light from the light source, A uniform viewpoint adjustment method for a line camera that adjusts the degree of adjustment of the viewpoints of a plurality of line cameras using the reference sample for viewpoint adjustment of the line camera.

6. An inspection apparatus comprising: a line-shaped light source that irradiates a light-transmissive inspection object with light; a plurality of line cameras that are arranged in a line so as to face the light source with the inspection object interposed therebetween and that image light transmitted through the moving inspection object; and a slit that cuts off the spread of light from the light source, A uniform viewpoint adjustment method for a line camera that measures the light reception amount waveforms of each of a plurality of line cameras using the reference sample for viewpoint adjustment of the line camera and adjusts the degree of adjustment of the viewpoints of the line cameras.

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