KR102302028B1 - Apparatus and method for laser processing - Google Patents

Abstract

A laser processing apparatus capable of suppressing deterioration of processing quality during light-converging processing is provided.
A variable aperture is arranged in the path of the laser beam. The laser beam passing through the variable aperture is focused to form a beam waist on the surface of the object to be processed. In the path of the laser beam between the laser light source and the variable aperture, a beam expander having a function of changing the divergent convergence angle of the laser beam is arranged. The control device acquires the measured value of the laser beam power when the size of the opening of the variable aperture is set to the first size and the second size, and determines whether the relationship between the measured values is appropriate or not based on the judgment condition to judge When it is judged as non-conforming, the beam expander is controlled to change the divergent convergence angle of the laser beam so that the relationship between the measured values of the laser beam power is judged to be acceptable.

Description

Laser processing apparatus and laser processing method {Apparatus and method for laser processing}

This application claims priority based on Japanese Patent Application No. 2016-186850 for which it applied on September 26, 2016. The entire contents of the application are incorporated herein by reference.

The present invention relates to a laser processing apparatus and a laser processing method for processing with a beam waist.

When drilling is performed on the object to be processed, a method of performing processing by reducing the opening of the optical mask on the surface of the object to be processed (hereinafter referred to as reduction projection processing), and a method of processing at the position of the beam waist (hereinafter, condensing light) processing) is known. In the reduction projection processing, in general, the beam profile at the position of the optical mask is equalized, so that the beam profile on the surface of the object to be processed is processed into a top flat shape (refer to Patent Document 1).

The object to be processed is, for example, a composite substrate in which copper foil is adhered to a resin substrate. In the case of performing the reduction projection processing, a blackening treatment and a roughening treatment of the surface of the copper foil are usually performed in order to increase the laser energy absorption efficiency. When laser processing is performed in a mirror-finished state without performing blackening treatment and roughening treatment on the surface of the copper foil, higher power density is required. In processing of copper foil to which blackening treatment has not been performed, for example, perforation processing of copper foil of a package substrate, condensing processing is used in order to increase the power density of a laser beam.

In the case of drilling by means of condensing processing, the shape and size of the processing hole depend on the beam diameter (minimum spot diameter) of the beam waist.

Patent Document 1: Japanese Patent Application Laid-Open No. 2015-188890

The minimum spot diameter when the laser beam is condensed with a condensing lens is determined by the diffraction limit. However, when the profile of the laser beam incident on the condensing lens is disturbed, the beam spot cannot be focused up to the diffraction limit. If the profile of the laser beam incident on the condensing lens is disturbed due to changes in characteristics of the laser oscillator over time or deterioration of optical components, the beam spot cannot be focused to a target dimension. If machining is performed in a state where the minimum beam diameter is not reduced to the target dimension, the machining quality will deteriorate. For example, the shape or depth of the hole deviates from the allowable range.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser processing apparatus capable of suppressing deterioration of processing quality during light-converging processing.

According to one aspect of the present invention,

A laser light source for outputting a laser beam;

a variable aperture which is disposed in the path of the laser beam output from the laser light source and can change the size of the opening;

a condensing lens for condensing the laser beam passing through the variable aperture to form a beam waist on the surface of the object to be processed;

a beam expander disposed in the path of the laser beam between the laser light source and the variable aperture and having a function of changing the divergent convergence angle of the laser beam;

a measuring instrument for measuring the power of the laser beam condensed by the condenser lens;

and a control device for controlling the variable aperture and the beam expander,

The control device is

Obtaining a measured value of the power of the laser beam from the measuring instrument when the size of the opening of the variable aperture is set to a first size and when set to a second size,

determining whether the relationship between the measured value of the laser beam power when the size of the opening of the variable aperture is the first size and the second size based on a determination condition;

When the relationship between the measured values of the laser beam power is judged to be inconsistent, the laser processing apparatus controls the beam expander to change the divergent convergence angle of the laser beam so that the relationship between the measured values of the laser beam power is judged to be acceptable. is provided

According to another aspect of the present invention,

A method of performing laser processing by passing a laser beam through a variable aperture capable of changing the size of an opening and then condensing the laser beam to form a beam waist on the surface of an object to be processed,

When the size of the opening of the variable aperture is set to the first size, the power of the laser beam transmitted through the variable aperture, and when the size of the opening of the variable aperture is set to the second size By adjusting the ratio of the power of the laser beam, the beam profile on the surface of the object to be processed is controlled,

After controlling the beam profile, there is provided a laser processing method for performing laser processing by setting the size of the opening of the variable aperture to a size applied during processing.

When the relationship between the measured values of the laser beam power is judged to be inconsistent, laser processing can be continued under favorable conditions by adjusting the beam expander. Accordingly, it is possible to suppress deterioration of the processing quality during the light-converging processing. Further, by controlling the beam profile on the surface of the object to be processed, it becomes possible to perform desired processing.

In Fig. 1, Fig. 1 (a) and Fig. 1 (b) are schematic views of a laser processing apparatus according to an embodiment.
Fig. 2 is a flowchart of processing executed by the control apparatus of the laser processing apparatus according to the embodiment.
3 is a chart showing the relationship between the evaluation ratio A and the machining surface profile.
4 is a schematic diagram of a laser processing apparatus according to another embodiment.
In Fig. 5, Figs. 5(a) to 5(c) are cross-sectional photographs of holes processed in the state where the evaluation ratio A is 30%, 50%, and 70%, respectively.
6 is a graph showing the relationship between the evaluation ratio A, the diameter of the opening of the processed hole, and the depth of the processed hole.

A laser processing apparatus according to an embodiment will be described with reference to FIGS. 1A to 4 .

1(a) and 1(b) are schematic views of the laser processing apparatus according to the present embodiment. The laser light source 10 outputs a pulsed laser beam. As the laser light source 10, for example, a carbon dioxide laser oscillator can be used.

The pulsed laser beam output from the laser light source 10 is incident on the measuring instrument 15 via the beam expander 11 , the variable aperture 12 , the beam scanner 13 , and the condensing lens 14 . The beam expander 11 is composed of, for example, three lenses, and by changing the relative positions of the three lenses, the beam diameter and divergent convergence angle of the laser beam can be changed. A lens optical system having such a function is sometimes referred to as a "beam expander telescope".

The variable aperture 12 has a circular opening having a variable size. As the variable aperture 12, for example, a rotating disk provided with openings of various sizes may be used. The center of the opening of the variable aperture 12 coincides with the central axis of the laser beam. When the opening is made larger than the cross-section of the laser beam, all components of the laser beam pass through the variable aperture 12 as shown in FIG. 1A. When the opening is made smaller than the cross-section of the laser beam, only the central axis of the laser beam and a part of its surrounding components pass through the variable aperture 12 as shown in FIG. 1B. The laser beam passing through the opening of the variable aperture 12 is incident on the beam scanner 13 .

The beam scanner 13 scans a laser beam in a two-dimensional direction. For the beam scanner 13, for example, a galvanoscanner including a pair of galvanometer mirrors can be used. The laser beam scanned by the beam scanner 13 is focused on the surface of the object 30 by the condensing lens 14 . For the condensing lens 14, for example, an fθ lens can be used. The relative positions of the condensing lens 14 and the object 30 are adjusted so as to form a beam waist on the surface of the object 30 . The object to be processed 30 is, for example, a copper-clad laminate on which a plurality of package substrates are multi-faceted.

1(a) and 1(b) show a state in which the measuring instrument 15 is disposed at the converging position of the laser beam. The measuring instrument 15 measures the average power of the incident laser beam. As the measuring instrument 15, for example, an optical power meter for measuring the power of a laser beam can be used. By disposing the measuring instrument 15 at the condensing position, it is possible to measure the average power of the pulsed laser beam.

The measured value measured by the measuring instrument 15 is input to the control device 20 . The control device 20 transmits an output command of the pulsed laser beam to the laser light source 10 . In addition, the control device 20 controls the beam expander 11 to change the divergent convergence angle and the beam diameter of the laser beam, and controls the variable aperture 12 to change the size of the opening. In addition, the control device 20 moves the measuring instrument 15 to the condensing position of the laser beam to evacuate from the converging position.

Various data and commands required for laser processing can be input from the input device 21 to the control device 20 . As the input device 21, for example, a keyboard, a touch panel, a display device, a pointing device, and the like can be used.

Next, a laser processing method using a laser processing apparatus according to an embodiment will be described with reference to FIG. 2 .

Fig. 2 is a flowchart of processing executed by the control device 20 (Fig. 1(a)) of the laser processing apparatus according to the embodiment.

Before laser processing of the object 30 (FIG. 1(a)), it is determined in step S01 whether or not the control device 20 adjusts the beam profile. For example, the control device 20 executes a process of adjusting the beam profile immediately after the laser processing apparatus is started, and whenever a predetermined period of time elapses in advance. When the beam profile is not adjusted, the object 30 is arranged at the converging position of the laser beam in step S09.

Next, the case where the beam profile is adjusted will be described. First, in step S02, the measuring instrument 15 (FIG. 1(a)) is arranged at the converging position of the laser beam. Thereafter, in step S03, the size of the opening of the variable aperture 12 is adjusted to the first size. In step S04, a pulsed laser beam is output from the laser light source 10, and the measured value of the average power of the pulsed laser beam measured by the measuring instrument 15 is acquired.

Thereafter, in step S05, the size of the opening of the variable aperture 12 is adjusted to the second size. In step S06, a pulsed laser beam is output from the laser light source 10, and the measured value of the average power of the pulsed laser beam measured by the measuring instrument 15 is acquired.

In step S07, the measured value of the average power when the opening of the variable aperture 12 is set to the first size and the measured value of the average power when the opening of the variable aperture 12 is set to the second size Conformity or nonconformity of the relationship is judged based on a predetermined judgment condition. The judgment conditions will be described later. When the determination result is "inconsistent", by adjusting the beam expander 11 (Fig. 1(a)) in step S08, the divergent convergence angle of the laser beam is changed so that the determination result becomes "conformity". Thereafter, the processes from step S03 to step S07 are executed again.

If the determination result in step S07 is "suitable", in step S09, the object 30 is arranged at the converging position of the laser beam. In addition, the size of the opening of the variable aperture 12 is adjusted to the size at the time of predetermined processing. Thereafter, laser processing is performed in step S10. In step S10 , the control device 20 operates the beam scanner 13 to cause the laser beam to be incident on a position where a hole is to be formed in the surface of the object 30 . Thereby, a hole is formed at a predetermined position.

Next, the determination conditions applied in the determination of step S07 will be described. In this embodiment, the first size (step S03) of the opening of the variable aperture 12 is made larger than the second size (step S05). The measured values of the average power when the openings of the variable aperture 12 have the first size and the second size are denoted by P1 and P2, respectively. Define P2/P1 as the evaluation ratio A. When the evaluation ratio A is within the allowable range, the judgment result becomes "acceptable";

Next, with reference to FIG. 3, the allowable range of the evaluation ratio A will be described.

3 is a chart showing the relationship between the evaluation ratio A and the machining surface profile. As the evaluation ratio A is larger (closer to 1), it can be said that the light intensity distribution at the position of the variable aperture 12 is localized in the vicinity of the central axis of the laser beam. That is, the increase in the evaluation ratio A means that the beam diameter of the laser beam incident on the condensing lens 14 (Fig. 1(a)) becomes small. As the beam diameter of the incident laser beam decreases, the beam diameter (beam diameter in the processing surface) of the beam waist of the laser beam focused by the condensing lens 14 increases. When the power of the laser beam is constant, the beam diameter of the beam waist becomes large, and the peak power at the processing surface becomes small.

Conversely, when the evaluation ratio A becomes small, the beam diameter of the beam waist of the laser beam focused by the condensing lens 14 (beam diameter in the processing surface) becomes small. When the power of the laser beam is constant, the beam diameter of the beam waist becomes small, and the peak power at the processing surface becomes large. In this way, the evaluation ratio A has a certain relationship with the beam profile of the machining surface. That is, it can be seen that the evaluation ratio A affects the processing quality.

The allowable range of the evaluation ratio A can be determined by actually performing laser processing under various conditions in which the value of the evaluation ratio A is different and evaluating the processing results.

Next, the excellent effect of the laser processing apparatus according to the above embodiment will be described.

The optimal beam profile differs according to the material of the object 30, the shape of the hole to be formed, or the type of processing (close drilling, through-hole processing, etc.). In the laser processing apparatus according to the embodiment, the beam profile on the processing surface can be controlled by changing the evaluation ratio A. By setting the allowable range of the evaluation ratio A so as to obtain a beam profile suitable for each material of the object 30, the shape of the hole to be formed, and the type of processing, drilling can be performed under suitable conditions.

Moreover, in this embodiment, since the beam profile adjustment process from step S02 to step S07, S08 shown in Fig. 2 is automatically executed whenever a certain time elapses, the stability of the machining quality is improved.

Next, a laser processing apparatus according to another embodiment will be described with reference to FIGS. 4 to 6 . Hereinafter, differences from the embodiment shown in Figs. 1A to 3 will be described, and descriptions of common configurations will be omitted.

Fig. 4 is a schematic diagram of a laser processing apparatus according to the present embodiment. In the laser processing apparatus according to this embodiment, the optical mask 17, the folding mirror 18, and the collimating lens 19 are arranged in the path of the laser beam between the beam expander 11 and the variable aperture 12. has been The object to be processed 30 is held on the stage 31 . A measuring instrument 15 is mounted on the stage 31 . The measuring instrument 15 moves together with the stage 31 according to a command from the control device 20 . A relay lens 35 is disposed in the path of the laser beam between the laser light source 10 and the beam expander 11 . The relay lens 35 is composed of, for example, two convex lenses.

The optical mask 17 shapes the beam cross-section by shielding the component of the outer edge of the beam cross-section of the laser beam that has passed through the beam expander 11 . The folding mirror 18 reflects the laser beam passing through the optical mask 17 toward the variable aperture 12 . For example, the variable aperture 12 is disposed below the folding mirror 18, and the folding mirror 18 reflects the laser beam downward. As the laser beam transmitted through the beam expander 11 is diffracted by the optical mask 17, the laser beam transmitted through the optical mask 17 becomes a divergent beam. The collimating lens 19 collimates the diverging beam. The collimated laser beam is incident on the variable aperture 12 . The stage 31 moves the object 30 and the measuring instrument 15 in the horizontal direction.

The beam expander 11 can change the divergent convergence angle and the beam diameter of the laser beam on the incident side at the position of the optical mask 17 .

The procedure for adjusting the beam profile in this embodiment is the same as that of the flowchart shown in FIG.

Next, with reference to FIGS. 5(a) to 5(c) and FIG. 6, the results of an evaluation experiment in which laser processing is performed using the laser processing apparatus shown in FIG. 4 will be described. Laser processing was performed under a plurality of conditions in which the evaluation ratio A was different. As the object 30 to be processed, an acrylic substrate was used.

In the evaluation experiment, the diameter of the circular opening of the optical mask 17 was set to 4.8 mm. The beam diameter of the laser beam at the position of the variable aperture 12 is about 25 mm. Here, the beam diameter is defined as the diameter of the closed curve connecting the positions where the ^{light intensity becomes 1/e 2 of the peak intensity.} The first size of the opening of the variable aperture 12 in step S03 (FIG. 2) is set to a size of 40 mm in diameter, and the second size of the opening of the variable aperture 12 in step S05 (FIG. 2). The size was set to a size of 12 mm in diameter.

That is, the first size is a size that includes the beam cross-section of the laser beam at the position of the variable aperture 12 , and the second size is larger than the cross-section of the laser beam at the position of the variable aperture 12 . small. When the opening of the variable aperture 12 is of the first size (step S03), almost all components of the laser beam propagating up to the variable aperture 12 pass through the variable aperture 12 . When the opening of the variable aperture 12 is of the second size (step S05 ), only a component near the central axis of the laser beam propagating up to the variable aperture 12 passes through the variable aperture 12 . The laser processing was performed under three conditions in which the evaluation ratio A was 30%, 50%, and 70%.

5(a) to 5(c) are cross-sectional photographs of holes processed in a state where the evaluation ratio A is 30%, 50%, and 70%, respectively. It can be seen that the cross-sectional shape of the hole, the size of the opening, and the depth of the hole are different according to the evaluation ratio A.

6 is a graph showing the relationship between the evaluation ratio A, the diameter of the opening of the processed hole, and the depth of the processed hole. The horizontal axis represents the evaluation ratio A in unit "%", the left vertical axis represents the diameter of the opening of the machined hole in unit "μm", and the right vertical axis represents the machined hole depth in the unit "μm". The triangular symbol and the circular symbol in FIG. 6 indicate the diameter of the opening of the processed hole and the depth of the processed hole, respectively.

It turns out that the diameter of the opening part of a hole becomes large and the depth becomes shallow as the evaluation ratio A becomes large. As shown in Fig. 3, as the evaluation ratio A increases, the beam diameter at the processing surface increases and the peak intensity decreases.

Based on the experimental results shown in Fig. 6, it is possible to determine the allowable range of the evaluation ratio A from the size and depth of the hole to be formed. The allowable range of the evaluation ratio A is input to the control device 20 from the input device 21 by the operator. For example, the control device 20 may display the allowable range of the evaluation ratio A on the display device for each size and depth of the hole to be formed, and the operator may select one from a plurality of allowable ranges.

When judging conformity/nonconformity of the relationship between the measured values in step S07 of Fig. 2, if the measured value of the evaluation ratio A falls within a predetermined allowable range, the relationship between the measured values is determined as "conformity", When the value of the evaluation ratio A is out of the allowable range, the relationship between the measured values may be judged as "nonconforming".

Next, the method of adjusting the beam expander 11 in step S08 shown in FIG. 2 is demonstrated.

The beam expander 11 changes the divergent convergence angle of the laser beam while maintaining the beam size at the position of the optical mask 17 (FIG. 4) substantially constant by changing the relative positions of the three lenses. can do it When the divergent convergence angle of the laser beam changes, the beam profile at the position of the variable aperture 12 changes. As a result, the evaluation ratio A changes.

Usually, it is adjusted so that the laser beam which has passed through the beam expander 11 may become a slightly converging beam. If the reduction angle of the converging beam is changed, the evaluation ratio A is changed. In the laser processing apparatus according to this embodiment, it has been confirmed by experiments that when the reduction angle of the converging beam is increased, that is, when the degree of convergence is increased, the evaluation ratio A is decreased. In addition, the relationship between the fluctuation range of the reduction angle and the fluctuation range of the evaluation ratio A can be determined by actually conducting an evaluation experiment. These relationships are stored in the control device 20 in advance.

The control device 20 can determine in which direction and to what extent the reduction angle of the converging beam needs to be changed from the difference between the measured value of the evaluation ratio A and the allowable range.

Next, the excellent effect of the laser processing apparatus according to this embodiment will be described.

Also in this embodiment, similarly to the embodiment shown in Figs. 1(a) to 4, by setting the allowable range of the evaluation ratio A, drilling can be performed under suitable conditions. In addition, since the beam profile adjustment processing from step S02 to step S07, S08 shown in Fig. 2 is automatically executed whenever a predetermined time elapses, the effect of improving the stability of the machining quality is obtained.

In addition, in this embodiment, the optical mask 17 is disposed in front of the variable aperture 12 . By shielding the component (component with a large diffusion angle) of the outer edge of the beam cross section with the optical mask 17, the processed shape can be stabilized. The laser beam is diffracted by the optical mask 17 , and the effect of the diffraction is reflected in the beam profile at the position of the variable aperture 12 . For example, the beam profile at the position of the variable aperture 12 is influenced by the diffraction by the optical mask 17, and takes a local maximum periodically as it moves away from the central position in the radial direction. For this reason, a region in which the light intensity exhibits a maximum value appears at the periphery of the cross section of the beam. When the periphery of this beam cross-section is shaded, compared with the case where the periphery of the Gaussian beam is shielded, the decrease in average power becomes larger. Accordingly, the amount of change in the evaluation ratio A due to the temporal change of the characteristics of the laser oscillator or the deterioration of the optical component becomes large. As a result, it is possible to improve the accuracy of determination of nonconformity of the measured value in step S07 (FIG. 2).

Next, the first size and the second size of the opening of the variable aperture 12 applied in the processing of steps S03 and S05 in FIG. 2 will be described.

In actual laser processing, the opening of the variable aperture 12 is made larger than the beam size at the position in order to effectively use laser energy. In order to estimate the beam profile of the laser beam used in actual processing, it is preferable that the first size be equal to or larger than the size of the opening of the variable aperture 12 when actually laser processing is performed. That is, it is preferable that the first size be such that the cross-section of the laser beam at the position of the variable aperture 12 is included.

The second size is set smaller than the first size. However, if the difference between the second size and the first size is too small, even if the beam profile at the position of the variable aperture 12 changes, the amount of change in the evaluation ratio A becomes small. For this reason, the determination precision of the conformity/nonconformity of the beam profile based on the evaluation ratio A will fall. In order to avoid a decrease in determination accuracy, the diameter of the second size is preferably 2/3 or less of the beam diameter at the position of the variable aperture 12, and more preferably 1/2 or less. . Here, "beam diameter" means a beam diameter when the laser processing apparatus is adjusted to the optimal state for processing.

Next, various modifications of the above embodiment will be described.

In the embodiment shown in Fig. 2, first, the opening of the variable aperture 12 is set to a first size (step S03) and the light intensity is measured (step S04), and then the opening of the variable aperture 12 is removed. Although the light intensity was measured with the second size smaller than one size (step S05) (step S06), the order may be reversed and steps S05 and S06 may be performed before steps S03 and S04.

In the above embodiment, the surface of the object 30 is matched to the height of the beam waist of the laser beam, but within a range that can perform processing of substantially the same level of quality, the surface of the object 30 is adjusted to the height of the beam waist. The position may be shifted up and down. For example, the surface of the object 30 may be shifted up and down from the position of the beam waist within the range of the depth of focus.

Each of the above-described embodiments is an example, and it cannot be overemphasized that partial substitutions or combinations of configurations shown in other embodiments are possible. The same operation and effect by the same configuration of a plurality of embodiments will not be sequentially mentioned for each embodiment. In addition, the present invention is not limited to the above examples. For example, it can be said that it is obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

10 Laser light source
11 Beam Expander
12 Variable Aperture
13 beam syringe
14 condensing lens
15 instrument
17 Optical Mask
18 folding mirror
19 collimated lens
20 control
21 input device
30 object to be processed
31 stage
35 relay lens

Claims (6)

A laser light source for outputting a laser beam;
a variable aperture which is disposed in the path of the laser beam output from the laser light source and can change the size of the opening;
a condensing lens for condensing the laser beam passing through the variable aperture to form a beam waist on the surface of the object;
a beam expander disposed in the path of the laser beam between the laser light source and the variable aperture, and having a function of changing the divergent convergence angle of the laser beam;
a measuring instrument for measuring the power of the laser beam condensed by the condenser lens;
and a control device for controlling the variable aperture and the beam expander,
The control device is
Obtaining a measured value of the power of the laser beam from the measuring instrument when the size of the opening of the variable aperture is set to a first size and a second size,
determining whether the relationship between the measured value of the laser beam power when the size of the opening of the variable aperture is the first size and the second size based on a determination condition;
A laser processing apparatus for changing a divergent convergence angle of a laser beam by controlling the beam expander so that the relationship between the measured values of the laser beam power is judged to be satisfactory, when the relationship between the measured values of the laser beam power is determined to be satisfactory. The method of claim 1,
It further has an optical mask disposed in the path of the laser beam between the beam expander and the variable aperture to shape the beam cross-section of the laser beam,
The beam expander is a laser processing apparatus having a function of changing a diverging and converging angle of a laser beam incident on the optical mask. 3. The method according to claim 1 or 2,
The first size is a size that includes a cross-section of the laser beam at the position of the variable aperture, and the second size is smaller than the cross-section of the laser beam at the position of the variable aperture. Device. 3. The method according to claim 1 or 2,
Further comprising an input device to which the determination condition is input,
The control device is a laser processing device that determines whether or not the relationship between the measured values of the laser beam power is suitable or not based on the determination condition input from the input device. A method of performing laser processing by passing a laser beam through a variable aperture capable of changing the size of an opening and then condensing the laser beam to form a beam waist on the surface of an object to be processed,
When the size of the opening of the variable aperture is set to the first size, the power of the laser beam transmitted through the variable aperture, and when the size of the opening of the variable aperture is set to the second size, the amount of light transmitted through the variable aperture By adjusting the ratio of the power of the laser beam, the beam profile on the surface of the object to be processed is controlled,
After controlling the beam profile, laser processing is performed by setting the size of the opening of the variable aperture to a size applied during processing. 6. The method of claim 5,
The laser processing method of adjusting the said ratio by changing the divergent convergence angle of the laser beam in the path|route on the side of a laser light source rather than the said variable aperture.

Images