JPH07199004A - Fiber coupling optical system - Google Patents

Abstract

PURPOSE:To obtain a fiber coupling optical system which has superior luminous flux transmission characteristics by dispersing the luminous flux of the center area of the section of the luminous flux to the peripheral area and converging the luminous flux of the peripheral area on the center area. CONSTITUTION:The luminous flux emitted from a laser light source 1 is made incident on a fiber A1 through a collimator lens system 6, but the emitted luminous flux has a uniform light quantity distribution since the fiber A1 is an SI type and is made incident on the coupling optical system 7. The coupling optical system 7 converts the light quantity distribution state in the luminous flux section into luminous flux which is converged on the center part and a stop member 3 provided in the coupling optical system 7 reduces the diameter of the luminous flux. The quantity of light of the part which is cut off by the stop member 3 is extremely small and light quantity loss becomes extremely small. Further, the external diameter of the luminous flux passed through the stop member 3 becomes small, so projection NA (substantial power) becomes small and the light quantity loss of a fiber BI is suppressed smaller than before.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coupling optical system of an optical transmission system using a fiber used in, for example, a laser processing device.

[0002]

2. Description of the Related Art In recent years, a processing method (so-called laser processing) in which a processing tool is directly contacted with a processing material by irradiating laser light (so-called laser processing) has been used. However, it is attracting attention as a processing method having various advantages such as that it can be processed in a short time.

Here, a fiber transmission system in a general laser processing apparatus will be described by showing its schematic configuration in FIG. FIG. 7A shows a laser processing apparatus in which one processing portion is provided for one laser light source, and is an example of the configuration of an optical transmission system that guides a light beam from the laser light source to the processing surface by one fiber. Yes, a total reflection type SI fiber is used here.

In FIG. 7A, a light beam emitted from a laser light source 31 enters a fiber A through a collimator lens 37 as a coupling optical system and a diaphragm 33. The coupling optical system in this case has a function for coupling the laser light source 31 and the fiber, and includes a collimator lens 37.

The collimator lens 37 is an optical system for adjusting the incident NA of the light beam so that the light beam emitted from the light source 31 can be efficiently incident on the fiber A.
Reference numeral 3 denotes an adjusting mechanism that reduces the effective diameter by shielding the peripheral portion of the light beam cross section. Then, the light flux emitted through the fiber A is condensed by the condensing optical system 38 to form a condensed spot on the processed surface 35.

FIG. 7B shows an example of a laser processing apparatus in which two processing parts are provided for one laser light source, and a laser beam is emitted from the laser light source to the processing surface via two fibers. 2 is an example of the configuration of an optical transmission system that guides In this example, the switching means provided in the transmission system switches the fiber that guides the light beam to the processing unit to be used, so that it is possible to perform laser processing at a plurality of spatially separated locations using one light source. You can do it.

In FIG. 7B, the light beam emitted from the laser light source 41 is made incident on the fiber B via the collimator lens 47a and the diaphragm 43a which are the first coupling optical system as in the above. The light flux emitted through the fiber B is guided to the next fiber C or D after the emission NA and effective diameter of the light flux are adjusted again by the second coupling optical system 47b and the diaphragm 43b.

The second coupling optical system 47b and the diaphragm 43b.
Is integrally formed with the switching means (not shown) in this fiber transmission system, and the light flux passing through the coupling optical system 47b, the diaphragm 43b and the switching means is the fiber C.
Alternatively, it is incident on the fiber D and guided to the processing surface 45 or 55 corresponding thereto.

Fiber C or fiber D
The emitted light flux is condensed by the condensing optical systems 48 and 58 to form condensing spots on the respective processed surfaces 45 and 55.

By the way, in a general laser processing apparatus,
It is equipped with an optical transmission system that uses a YAG laser or the like as a light source to transmit a light flux from the light source to the processing location by a fiber. The light flux emitted from the fiber is focused on the processing surface by a condenser lens, etc. Laser processing is performed. In order to improve the processing efficiency in such a laser processing apparatus, it is an important point to increase the optical power density on the processing surface.

Conventionally, in order to increase the optical power density at this converging point, an optical design has been performed so that the diameter of the converging spot on the processed surface is made as small as possible. The size of the focused spot diameter on the processed surface is determined by the type of laser light source used, the divergence angle of the laser, or the diameter of the fiber used and its NA.

In such an optical transmission system, there is a Helmholz-Lagran between the type of laser light source used and the divergence angle of the laser, or between the fiber diameter and NA.
The invariant of ge generally holds. This Helmhol
The invariant of z-Lagrange is that “height of light ray × gradient of light ray is preserved”, and the following equation holds from this. φL × αL = φL ′ × αL ′ Equation (1) φA × αA = φA ′ × αA ′ Equation (2) φB × αB = φ × α Equation (3)

Here, the diameter of the emitting portion of the laser light source is φ
L, NA of the divergent light emitted from the laser light source is αL, the core diameter of the transmission fiber A is φA, and the transmission fiber A is N
A is αA, the core diameter of the transmission fiber B is φB, the NA of the transmission fiber B is αB, the focused spot diameter on the processed surface is φ, the focused NA on the processed surface is α, and the fiber A is incident by the optical system L1. The diameter of the light source image formed on the end face is φL ′,
The NA of the converged light imaged on the incident end face of the fiber A by the optical system L1 is αL ′, and the fiber B by the optical system L2 is
Let φA ′ be the diameter of the core image of the fiber A formed on the incident end surface of A, and αA ′ be the NA of the converged light imaged on the incident end surface of the fiber B by the optical system L2.

In order to eliminate the light quantity loss due to the coupling optical system in the transmission system, "the size of the image at the exit end surface x the value of the emitted convergent light NA" is calculated as "the value of the fiber on which the light beam enters. Since it is important to make it smaller than “core diameter × NA value of the fiber”, it is necessary to satisfy the following expressions (4) and (5). φL ′ ≦ φA, αL ′ ≦ αA Equation (4) φA ′ ≦ φB, αA ′ ≦ αB Equation (5) From the above Equations (1) to (5), the following Equation (6) is established. . φL × αL ≦ φA × αA ≦ φB × αB ≦ φ × α (6)

Therefore, from the formula (6), "diameter of laser light source x divergence value of laser light source", "core diameter of transmission fiber A x NA value of transmission fiber A", or "core of transmission fiber B" Diameter x NA of transmission fiber B ”
If any one of them is reduced, the spot diameter on the processed surface can be further reduced, and the light quantity loss due to the coupling optical system can be reduced.

[0016]

By the way, as a means for reducing the diameter of the focused spot on the processed surface as much as possible,
A method of reducing the magnification of the condensing optical system that condenses the light beam transmitted from the fiber and a method of reducing the core diameter of the fiber used in the transmission system are considered.

However, in the former method of reducing the magnification of the condensing lens, the NA on the exit side of the condensing optical system becomes large, and therefore the aberration is corrected unless the number of lenses forming the condensing optical system is increased. This makes it difficult to design the condensing optical system and causes a cost increase.

In the latter method of reducing the core diameter of the fiber used, there is a drawback that when the light beam from the laser light source is guided by the fiber, it leaks from the core of the fiber, resulting in an extremely large light quantity loss. There is.

As another method, there is a method of shielding the peripheral portion of the light beam emitted in the transmission system and adjusting the diameter of the light beam cross section. In this method, since the effective diameter can be reduced by blocking the light flux, the magnification of the optical system to be provided next is changed according to the reduction amount of the diameter in the cross section of the light flux, and the exit NA of the condensing optical system is not changed. The focused spot can be narrowed down. However, also in this case, since the light amount is partially cut by the light shielding member, there is a problem that the light amount loss is about the same as the light amount loss due to the method of reducing the core diameter.

Here, the light amount loss caused by blocking the light beam emitted in the transmission system will be described by taking the optical transmission system shown in FIG. 7A as an example. In FIG. 7A, the light quantity of the cross section of the light beam before passing through the diaphragm 33 is W1, and the diaphragm 33 is
Let ΔW1 be the amount of light in the cross section of the light beam shielded by
W1 and ΔW1 can be expressed by the following equations (7) and (8).

[0021]

[Equation 1]

[0022]

[Equation 2]

However, I (r) is the light amount distribution in the light flux cross section, a is the radius of the light flux before passing through the diaphragm, and ka is the radius in the light flux cross section after being shielded. From this, the light amount loss amount LOSS caused by the light shielding is expressed by the following equation. LOSS = ΔW1 / W1 × 100 (%) Equation (9)

Here, in the light flux emitted from the SI type fiber, since the light amount distribution in the cross section is uniform, I (r) = 1 in the above equation, and the light amount loss amount is
It is expressed by the following equation. LOSS = (1−k) ² × 100 (%) Equation (10)

Further, the light blocking ratio Δk in the light beam cross section
Is Δk = 1−k 1, the light amount loss amount LOSS
Is approximated by the following equation. LOSS≈2 × Δk × 100 (%) Equation (11)

Further, in the optical transmission system shown in FIG. 7B, since the diaphragms 43a and 43b are arranged at two places in the transmission system, the light beam is shielded each time it passes through the diaphragms 43a and 43b. Therefore, the amount of light loss is increased as compared with the case where one light blocking member is provided.

As described above, in the conventional optical transmission system, a large amount of light is lost due to the action and characteristics of the optical members arranged in the transmission system, and it is possible to suppress the decrease in the intensity of the transmitted light flux. It has become a development proposition for optical transmission systems.

The present invention has been made in view of these problems, and its main purpose is to provide a fiber coupling optical system having an excellent light flux transmission characteristic. In particular, it is also an object to obtain a fiber-coupled optical system which has a small light quantity loss and can effectively utilize the intensity of the laser light when applied to a laser processing apparatus using the laser light.

[0029]

[Means for Solving the Problems] To achieve the above object,
The invention according to claim 1 of the present invention is a fiber coupling optical system for coupling a fiber with another member provided in a transmission system when guiding a light beam from a light source in the transmission system. A light amount distribution conversion means is provided for dispersing the light flux of the central region in the cross section of the light flux transmitted within the peripheral region and concentrating the light flux of the peripheral region in the cross section in the central region.

According to a second aspect of the present invention, in the fiber transmission system according to the first aspect, the light amount distribution conversion means has a first conical optical element and a second conical optical element which are sequentially arranged along the traveling direction of the light beam. A conical optical element, wherein the first and second conical optical elements are arranged such that their apex angles are opposite to each other, and the central axis of the element and the central axis of the light beam coincide with each other. It is arranged as follows.

Further, the invention of claim 3 is the fiber transmission system according to claim 2, wherein the first and second conical optical elements are focused by the first conical optical element on the central axis of the light beam. The position and the apex angle of the second conical optical element are arranged so as to coincide with each other.

Further, the invention of claim 4 is the fiber transmission system according to claim 1, 2 or 3, further comprising a light beam diameter adjusting means for adjusting the diameter of the light beam whose light amount distribution is converted by the light amount distribution converting means. It is further equipped.

[0033]

Since the present invention is configured as described above, it has the following effects. First, in the present invention, when the light flux from the light source is guided in the transmission system, a coupling optical system for coupling the fiber with other members provided in the transmission system is provided, and the amount of light provided in the coupling optical system is provided. The distribution conversion means disperses the light flux in the central region in the cross section of the light flux transmitted in the transmission system into the peripheral region and concentrates the light flux in the peripheral region in the cross section in the central region.

That is, the light quantity distribution converting means in the present invention changes the luminous flux in the luminous flux cross section,
This is for converting the distribution of the light quantity in the cross section of the light flux. For example, if a light flux with a uniform light quantity distribution in the cross section of the light flux is passed, the light flux in the peripheral part before passing will be concentrated in the central part. As the light intensity of the part increases,
Since the light flux in the central portion before passing through is dispersed in the peripheral portion, the light amount in the peripheral portion after passing is reduced.

Therefore, by passing through the light quantity distribution converting means, the light flux having a uniform light quantity distribution in the cross section is changed into a light flux having a light quantity distribution having a high central intensity and a low peripheral intensity. . On the contrary, when a light flux having a light intensity distribution in which the intensity of the central part is high and the intensity of the peripheral part is low,
It is converted into a light flux having a roughly averaged intensity distribution.

By coupling the fiber and other members with a coupling optical system equipped with such a light quantity distribution converting means,
A light quantity transmission method suitable for the converted light quantity distribution characteristic can be adopted. For example, when the light flux from the light source is incident on the fiber, or when the light flux emitted from the fiber is incident on another fiber or the like, the light amount is concentrated on the center of the light flux via the coupling optical system of the present invention. Therefore, even when the light flux system is reduced on the exit side by a diaphragm or the diameter of the fiber, the light density of the light flux in the light-shielded portion is small, so that the light amount loss amount can be suppressed to an extremely small amount.

Further, in the invention described in claim 2, the light quantity distribution converting means has a first conical optical element and a second conical optical element which are sequentially arranged along the traveling direction of the light beam. The first and second conical optical elements are arranged so that their apex angles face each other, and are arranged so that the central axis of the elements and the central axis of the light beam coincide with each other. .

Here, the conical optical element used in the present invention does not necessarily have to be a perfect conical shape, but may be an optical element having at least a conical surface portion corresponding to a side surface portion of the conical shape. Therefore, for example, a cone-shaped apex part partially cut parallel to the bottom part can be applied to the present invention.

The two conical optical elements are arranged so that their apexes face each other, and
It is arranged so that the central axis of the cone coincides with the central axis of the passing light beam.

With this arrangement, the light beam incident from the bottom surface side of the first conical optical element is refracted at the conical surface portion of the first conical optical element. Progress toward. Therefore, the light flux at the peripheral portion in the light flux cross section travels in the central portion (optical axis) direction, but the light flux at the central portion (near the optical axis) is guided to the peripheral portion across the optical axis.

In this state, the light is incident on the second conical optical element. However, since the second conical optical element is arranged in the above-described positional relationship, the conical optical element of the first conical optical element is arranged. The light beam refracted by the surface portion enters the conical surface portion of the second conical optical element.

Here, when the apex angle of the second conical optical element is equal to that of the second conical optical element, it is incident on the conical surface of the second conical optical element. The light flux is refracted here and travels in the same traveling direction as before traveling in the first conical optical element.

Therefore, by appropriately adjusting the relative distance between the first and second conical optical elements, the luminous flux transmitted through both conical optical elements has a traveling position in the luminous flux cross section before and after transmission. The light amount distribution is converted according to these conversion amounts.

Here, in the invention described in claim 3, the relative distance between the first and second conical optical elements is such that the first conical optical element on the central axis of the light flux (coincident with the central axis of the cone). Are arranged and aligned so that the condensing position by and the apex portion of the second conical optical element coincide with each other.

The converging position of the conical optical element means the peripheral portion in the cross section of the luminous flux when the luminous flux incident from the bottom surface of the conical optical element in parallel with the central axis of the cone is refracted and emitted at the conical surface portion. Is the position where the light flux of is condensed (crosses) on the optical axis.

The apex portion is the apex position itself when the conical optical element has a perfect conical surface, but in the case of an element with the apex portion removed, the apex portion is originally apex. The position where the position exists (the intersection point on the extension of the conical surface or the convergence position) is referred to.

When the two conical optical elements are arranged in such a relative positional relationship, in the light flux before and after transmission through these elements, the light flux at the peripheral portion of the cross section of the light flux before transmission is guided to the central axis portion. The light flux of the central axis portion before transmission is guided to the peripheral edge portion. Then, the light flux that travels in the central portion in the radial direction becomes a light flux that travels in substantially the same cross-sectional position before and after transmission.

In other words, the light fluxes in the central portion and the peripheral portion are completely interchanged with the central portion in the radial direction as a boundary, but the cross-sectional areas are different before and after the interchange. That is, the cross-sectional area of the light flux in the central portion is a circle whose radius is half that of the cross-sectional area of the entire light flux,
Although it is 1/4 of the whole, the cross-sectional area of the peripheral portion will occupy the remaining 3/4.

Therefore, after passing through the light amount distribution converting means, the light flux in the central portion before being transmitted is dispersed into a portion having a cross-sectional area of about three times when being guided to the peripheral portion, so that it is about 1 / before transmitting.
The light quantity density is 3 or less. On the contrary, the light flux in the peripheral portion before transmission is concentrated in a portion having a cross-sectional area of about ⅓ of the central portion and has a light amount density of about three times or more.

Therefore, it is understood that the light amount distribution conversion element as described above can convert the light amount distribution in the light beam cross section by changing the traveling position in the cross section of the transmitted light beam. For example, when a light flux having a uniform light intensity distribution is incident, it is converted into a light flux having a high intensity (light intensity density) in the central part and a low intensity in the peripheral part, and conversely, the light intensity density in the central part. When a high luminous flux is transmitted, the luminous flux becomes a luminous flux having an averaged light amount distribution.

The conversion status of such a light quantity distribution is described in claim 3.
In the case where the light amount distribution conversion means having the arrangement as in the invention described in 1) is provided, the conversion state of the light amount distribution can be changed by changing the relative distance.

Next, in the invention described in claim 4, since the light beam diameter adjusting means for adjusting the diameter of the light beam whose light amount distribution is converted by the light amount distribution converting means is provided, the light amount density in the cross section of the light beam is changed. The lower part is selectively removed to adjust the diameter of the light flux. That is, if the luminous flux diameter adjusting means is configured by using the diaphragm means and the diameter of the luminous flux having a low light quantity density at the peripheral portion in the luminous flux cross section is adjusted as described above, the light quantity of the portion shielded by the diaphragm means is reduced from the whole. Since it is very small when viewed, the light amount loss is also small.

Here, the state of light amount loss in the light beam diameter adjusting means of the present invention will be specifically described with reference to FIG. 4 (a) is an explanatory view showing a schematic configuration of an optical transmission system using a fiber coupling optical system of the present invention, fiber A ₄
And a fiber B ₄ are connected by a coupling optical system 7a.

In FIG. 4A, the light beam emitted from the fiber A ₄ becomes a parallel light beam through the lens L2a and enters the light amount distribution converting means 2a. Here, FIG.
(B) shows a light quantity distribution state in the cross section of the light flux (S ₁ position) between the lens L2a and the light quantity distribution conversion means 2a.

The light quantity distribution converting means 2a is a conical optical element (hereinafter, referred to as a conical optical element made of a glass optical member having a conical surface portion).
It is called a conical lens).
The conical lenses are arranged such that the central axes of the conical lenses and the optical axis of the light beam coincide with each other, and the vertices of the two conical lenses face each other. Further, the conical lenses are transmitted through the first conical lens R ₁ . The second conical lens R ₂ is arranged so that the apex position of the second conical lens R ₂ coincides with the position where the light beam that has passed through the peripheral portion converges on the optical axis.

As described above, the light beam incident on the light amount distribution converting means 2a passes through the first conical lens R1 and then
By passing through the second conical lens R2, the light amount distribution in the light beam cross section becomes a converted light beam. Here, in FIG. 4C, the luminous flux (S
The light intensity distribution in the cross section at position ₂ ) is shown.

In FIGS. 4B and 4C, the solid line and the dotted line are the light quantity distribution states corresponding to before and after conversion, respectively, and S
It shows a case where a light beam having a uniform distribution (solid line portion) emitted from the I-type fiber is incident and a case where a light beam having a mountain distribution (dotted line portion) emitted from the GI type fiber is incident.

Here, the conversion status of the light quantity distribution is analyzed as follows. First, the light quantity distribution state in the cross section S ₁ of the light beam before entering the light quantity distribution converting means 2a is expressed as I (r).
Then, the light amount distribution I ′ (r) in the cross section S ₂ of the light flux emitted from here is expressed by the following equation. I ′ (r) = (ar) / r × I (ar) Equation (12)

Further, the light flux which has passed through the light quantity distribution conversion element 2a is partially shielded by the diaphragm 3a so that the outer diameter of the light flux cross section is reduced, and then the light flux is condensed by the lens L3a to the fiber B. Incident.

Here, the diameter of the light beam before being blocked by the diaphragm 3a is a, the diameter of the light beam cross section after being blocked by the diaphragm 3a is (1-k) a (where k <1), and the diaphragm 3a is Assuming that the amount of light in the cross section of the light beam before passing is W2 and the amount of light in the cross section of the light beam shielded by the diaphragm 3a is ΔW2, W2 and ΔW2 can be expressed by the following equations (13) and (14). .

[0061]

[Equation 3]

[0062]

[Equation 4]

Then, the light amount loss amount LOSS caused by the light shielding can be expressed by the following equation (15). LOSS = ΔW1 / W1 × 100 (%) Equation (15)

Further, since the light quantity of the cross section of the light beam emitted from the SI type fiber has a uniform distribution, I (r) =
Since it is 1, the light amount loss amount LOSS is expressed by the following equation. LOSS = (1−k) ² × 100 (%) Equation (16)

Here, when the ratio Δk of the light shielding portion to the light beam diameter of the light shielding portion is Δk = 1−k 1, the light amount loss amount L
OSS is approximated by the following equation. LOSS = Δk ² × 100 (%) Equation (17)

That is, the light amount loss amount LOSS in the case where only the above-mentioned diaphragm is provided is given by the equation (11).
A small amount of first-order relative to the light-shielding ratio Δk (LOSS≈2 × Δ
k × 100 (%)), whereas the light amount loss amount LO when light is blocked after passing through the light amount distribution conversion element of the present invention
SS is a secondary minute amount. This shows that in the fiber transmission system utilizing the present invention, the amount of light loss caused by the coupling optical system is suppressed as much as possible.

The total light amount of the transmitted light beam is calculated by the processing power P.
Then, it is expressed by the following equation. P = (1-LOSS) / k 2 × 100 = (1- (1-k) 2) / k 2 × 100 = (2 / k-1) × 100 (%) ... Equation (18)

In the above case, the amount of light loss by the coupling optical system of the present invention is described by taking the case of using the SI type fiber as an example, but the effect of reducing the amount of light loss is also obtained by using the GI type fiber. There is something.

Thus, the coupling optical system according to the present invention is
Since it is possible to concentrate the light amount distribution in the central region of the light flux via the light intensity distribution conversion element, when the light transmission device is used in an optical transmission system in which the effective diameter is reduced by a light shielding member thereafter, the loss light amount is reduced. It is possible to obtain a fiber transmission system in which the intensity of the propagating light beam is reduced and which can be used with high efficiency.

Therefore, when the optical transmission system using this fiber coupling member is applied to, for example, a laser processing device, a laser processing device capable of effectively utilizing a light flux of a light source, that is, laser processing capable of obtaining high laser power. The device can be constructed.

In the above description, the case where the converging position of the first conical optical element and the apex position of the second conical optical element are matched with each other has been described. When the optical element is arranged, the light quantity distribution state of the light flux after transmission changes.

For example, when the relative distance between the conical optical elements is made closer than that of the above arrangement, interference light may be generated in the central region, and this interference action causes a light beam whose luminous intensity in the central region is extremely high. Obtainable.

Therefore, in the case where the intensity distribution required by the optical system (optical member) utilizing the light flux emitted from the coupling means of the present invention requires that the intensity of the central portion be high, etc. It may be arranged.

Further, even when the intensity distribution in the central region of the light flux becomes weak due to the type of the light source or the influence of the optical member until reaching the coupling optical system, the coupling of the arrangement configuration utilizing this interference action is performed. It is also possible to use an optical system to concentrate the light amount distribution in the central area of the cross section of the light flux.

On the contrary, when a light source having a high light density or power is used, the light intensity (density) at the central portion of the light beam condensed by the first conical optical element becomes extremely high, and the second cone The optical element and the optical member such as the fiber to be incident next may be damaged. In such cases,
The connecting means or the like having the above-described arrangement configuration or an arrangement configuration apart from the above arrangement may be used.

For example, in order to suppress the concentration of light quantity in the central region, as shown in FIG. 5A, the first light quantity conversion element is used.
By arranging the apex angle portion of the second conical lens at a position distant from the condensing position of the conical lens, concentration of light amount on the apex angle portion of the second conical lens is avoided, and As shown in FIG. 5B, it is possible to suppress the light amount of the light flux emitted from the central portion of the cross section.

However, in this case, the outer diameter of the light beam emitted from the second conical optical element is larger than the outer diameter of the light beam incident on the first conical optical element. However, as described above, since the light amount (light flux density) in the peripheral portion is small, the light amount loss amount is small even if the peripheral portion is shielded by the light beam diameter adjusting means.

Further, as shown in FIG. 6 (a), by using an element in which the apex angle portion (central portion) of the conical surface portion of the conical optical element is made flat (or hollow), It is possible to suppress the concentration of the light amount (density) in the central portion and convert the light amount distribution while maintaining the light amount in the central portion to some extent.

Furthermore, by having such an element structure,
Since there is no light flux going from the central part to the peripheral part,
Since the spread of the light flux can also be suppressed, the outer diameter of the light flux emitted from the second conical optical element can be suppressed.

As described above, when the coupling optical system according to the present invention is used, the light quantity distribution within the cross section of the light flux is converted.
Then, consider the arrangement configuration with other members such that the light amount distribution state after conversion becomes stronger (higher density) in the central region and becomes weaker (lower density) as it approaches the peripheral region, particularly the peripheral region. Is preferred.

With this structure, when the effective diameter of the light beam emitted from the coupling member and sent to another member is reduced, a means for shielding the light beam at the peripheral portion and adjusting the light diameter may be provided. The light amount loss can be suppressed to an extremely small level.

Further, by suppressing the light beam diameter in this way, the incident NA to the next member can be made small, so that the converging spot can be made small and the light beam can be effectively transmitted. There is an advantage that an optical transmission system can be constructed.

That is, when applied to a laser processing apparatus or the like, there was a demand for reducing the diameter of the focused spot on the processed surface as much as possible in order to improve the processing efficiency. Since the light flux system can be made smaller by suppressing the light quantity loss of the light flux emitted from the optical system, the design burden will be small even if the magnification of the focusing optical system that focuses the light flux transmitted from the fiber is reduced. .

Similarly, it has been considered to reduce the core diameter of the fiber used in the transmission system. However, if the light amount loss of the light beam emitted from the coupling optical system is suppressed and the light beam system is reduced, Since the emission NA from is also small, even if it is incident on a fiber having a small core diameter, the light amount loss in the fiber becomes extremely small.

It is preferable that the light beam diameter adjusting means is capable of adjusting the light beam diameter according to the type of light source and the required processing power by a light shielding member such as a diaphragm. If the arrangement is such that the diameter of the light beam emitted from the second conical optical element is adjusted, it is possible to obtain the one in which the light amount loss amount is reduced more reliably.

[0086]

The present invention will be described in more detail with reference to the following examples. FIG. 1 shows a schematic configuration of a laser processing apparatus to which a coupling optical system according to a first embodiment of the present invention is applied. This processing device performs laser processing by connecting two fibers by a coupling optical system and condensing the transmitted light beam on the processing surface by a condensing optical system when guiding the light beam from the light source to the processing surface. It is a thing.

In FIG. 1, the laser light from the laser light source ₁ is guided to the fiber A ₁ by the collimator lens system 6 composed of the lens L ₁ and enters the coupling optical system 7. This coupling optical system 7 is composed of a lens L2, a light quantity conversion means 2 and a lens L3 in this order from the light source 1 side, and is provided with a diaphragm member 3 for adjusting the light flux diameter.

Further, the luminous flux emitted from the coupling optical system 7 is guided to the fiber B ₁ and enters the condensing optical system 8. The condenser lens system 8 is composed of a lens L4 and a lens L5, and these lenses form a condensed spot on the processing surface 5 to perform laser processing.

In this embodiment, as the fiber A ₁ , an SI type fiber for making the intensity distribution on the exit end face uniform is used, but the fiber B ₁ may be an SI type or a GI type. .

The light beam emitted from the laser light source 1 enters the fiber A ₁ through the collimator lens system 6, but since the fiber A ₁ is of SI type, the fiber A ₁
If the length of ₁ is to some extent, the light amount distribution in the light beam cross section of the light beam transmitted and emitted by the fiber A ₁ becomes uniform. Therefore, the light beam emitted through the fiber A ₁ becomes a light beam having a uniform light amount distribution and enters the coupling optical system 7.

In the coupling optical system 7, the state of light quantity distribution in the cross section of the luminous flux is converted into a luminous flux concentrated in the central part, and the diameter of the luminous flux is reduced by the diaphragm member 3 provided in the coupling optical system 7. Is done.

The luminous flux whose luminous flux distribution and luminous flux diameter have been adjusted by the coupling optical system 7 is incident on the fiber B ₁ and transmitted, and is guided to the condenser lens system 8. The light flux that has entered the condenser lens system 8 is condensed by the lenses L4 and L5, and is irradiated onto the processed surface 5 as the condensed spot 4.

Coupling Optical System 7 of this Example 7 Coupling Optical System 7 It has the same structure as the coupling optical system shown in FIG. 4, and after converting a light beam having a uniform light quantity distribution into a state of being concentrated in the central portion, The diaphragm member 3 is used to reduce the effective diameter of the light beam. For this reason, the light amount of the portion shielded by the diaphragm member 3 is extremely small, and the light amount loss is extremely small.

Further, since the outer diameter of the light beam transmitted through the diaphragm member 3 becomes small, for example, the lens L having the same magnification as the conventional one is used.
Even if 3 is used, the emission NA is reduced as much as the luminous flux system becomes smaller.
(Substantial magnification) becomes smaller. It is also possible to use a lens with a small magnification that matches this light flux system. Since the incident NA to the fiber B ₁ is reduced by such a lens having a small magnification, the light amount loss in the subsequent fiber B ₁ can be suppressed to be smaller than before.

That is, in the laser processing apparatus according to the present embodiment, in order to improve the laser processing characteristics, a transmission system that suppresses the loss of light quantity is constructed so that the laser power itself is stronger than before.

As described above, the lens L3 arranged after the diaphragm member 3 is also a collimator lens for incidence on the fiber B _1. Therefore, by changing the magnification of this lens to a small one, a small core diameter can be obtained. Even if a fiber is used, the light amount loss in the fiber can be suppressed. That is, the fiber B _{1 on} which the light beam after passing through the light quantity conversion element 2 is incident
By making the effective NA of the fiber smaller than the effective NA of the fiber A ₁ , the light amount loss in the fiber having a small core diameter can be suppressed.

Further, in order to improve the laser processing characteristics, it is preferable to make the focused spot diameter smaller, but for that purpose, it is necessary to reduce the focusing magnification of the focusing optical system. In the conventional laser processing apparatus, there is a defect that the apparatus becomes large in size simply by reducing the magnification of the condenser lens.

In this embodiment, when the method of changing the magnification of the condenser lens in which the light beam enters through the fiber B ₁ is adopted, the light beam diameter can be reduced while the light amount loss is suppressed to a very low level. It is possible to use a lens having a small condensing magnification, and further, even if a condensing lens having a condensing magnification similar to the conventional one is used by reducing the diameter of the light beam, the substantial reduction magnification becomes small.

Since these two methods are affected by other design conditions of the laser processing apparatus, either one or both of them which are preferable in design may be selected and used. Here, the luminous flux propagation characteristics when the design conditions in the configuration of the first embodiment are changed will be described.

In the laser processing apparatus shown in the first embodiment, the amount of light when the diameter of the focused spot 4 is changed by changing the aperture amount of the aperture member 3 and the magnification of the lens L ₃ arranged after the aperture member 3. Consider the loss amount and processing power. First, when the diameter of the focused spot 4 is not reduced at all, the spot diameter is 0.9 times, 0.8 times, 0.7 times.
The light amount loss amount LOSS and the processing power P when doubled are shown in Table 1 in comparison with the light amount loss amount LOSS by the conventional method.

[0101]

[Table 1]

As is clear from Table 1, the light amount loss amount LOSS when the diameter of the focused spot 4 is reduced by the diaphragm to 0.9 times by the conventional method (without using the light amount distribution conversion element).
Is very large as LOSS = 19.0 (%), whereas the light loss loss LOSS in the present invention is LOSS = 1.
It becomes 0 (%), and the light amount loss amount LOSS can be significantly reduced. Similarly, the processing power P is 122.2 (%), which is considerably higher than that of the conventional example.

Further, when the diameter of the focused spot 4 is made smaller than 0.9 times, the ratio of lowering the light quantity loss amount LOSS is smaller than that when the diameter of the focused spot 4 is made 0.9 times (the light quantity loss amount). However, the processing power P is significantly increased as the spot diameter becomes smaller.

Here, in the laser processing apparatus having the same configuration as that of the first embodiment, the embodiment of the present invention and the conventional example (where light quantity distribution conversion is not performed when the diameter of the focused spot 4 is 0.9 times) ) Is shown in Table 2.

[0105]

[Table 2]

[0106] In Table 2, .phi.A the core diameter of the fiber A _1, .alpha.A the NA of the fiber A _1, squeezing .alpha.A the effective NA of the fiber A ₁ adjusted by the member 3 ', the focal length of the lens L2 f2, The focal length of the lens L3 is f
3. Imaging magnification of coupled lens system is mAB, fiber B ₁
, ΦB, NA of the fiber B ₁ is αB, the focal length of the lens L4 is f4, the focal length of the lens L5 is f5,
The imaging magnification of the condenser lens system is m, the diameter of the condensed spot 4 on the processed surface is φO, the condensed light beam NA to the processed surface is αO, the amount of light loss is LOSS, and 100% when the light beam is not shielded at all.
Let P be the average irradiation energy per unit area on the processed surface.

In the configuration example 1, after the effective diameter of the light flux is reduced by using the diaphragm member 3, the magnification of the lens L3 is reduced to reduce the light flux diameter with a small amount of loss of light quantity and reduce the emission NA. However, in this example, the focused spot diameter is reduced by making the light incident on the fiber B ₁ having a smaller diameter than the fiber A ₁ .

Further, in the configuration example 2, after the effective diameter of the light beam diameter is reduced by using the diaphragm member 3, it is incident on the fiber B ₁ having an effective NA smaller than the fiber A ₁ , and this fiber B ₁ is A condenser lens L through which a light beam is incident
This is an example in which the magnification of 5 is reduced.

On the other hand, Conventional Example 1 and Conventional Example 2 are examples in which the light quantity conversion element is not used in the coupling optical system 7. In the conventional example 1, the diaphragm member 3 is used to reduce the effective diameter of the luminous flux while keeping the light amount distribution of the luminous flux section unchanged, and the diaphragm member 3 is used.
This is an example in which the magnification of the lens L3 arranged after is reduced, and Conventional Example 2 is an example in which the light flux is condensed on the processed surface without reducing the condensed spot diameter.

As is clear from Table 2, the focused spot 4
If the diameter of is reduced by 10%, the amount of light loss is 1 in the conventional example.
While it is 9%, it can be extremely reduced to 1% in the example of the present invention. Therefore, the irradiation energy per unit area is increased by 20% as compared with the conventional example.

FIG. 2 shows the light quantity distribution of the focused spot 4 when the SI type is used for the fiber B ₁ . As described above, if the SI type fiber is long and meandering, the light amount distribution in the light beam cross section of the light beam transmitted and emitted by this fiber is generally uniform. Therefore, as shown in FIG. 2, the light amount distribution is almost uniform without the converging spot 4, but the total light amount (processing power) is significantly higher in the embodiment of the present invention than in the prior art. You can see that

Table 3 shows a configuration similar to that of the fiber transmission system shown in FIG. 1. A GI type fiber is used as the fiber A ₁ and the aperture amount of the aperture member 3 and the lens disposed after the aperture member 3 are used. The light amount loss amount LOSS and the irradiation energy P per unit area in the example of the present invention and the conventional example when the diameter of the focused spot is reduced by changing the magnification are shown. (However, the reference value is 1 when the diameter of the focused spot is not reduced at all.)

[0113]

[Table 3]

As is clear from Table 3, when the GI type fiber is used as the fiber A ₁ , the effect is slightly smaller than when the SI type fiber is used. It can be seen that the LOSS decreases and the irradiation energy P per unit area increases.

Next, a laser processing apparatus to which the second embodiment of the present invention is applied will be described with reference to FIG. Here, using the fiber transmission system according to the present invention, an optical transmission optical system in which a laser light source and a processed surface are connected by two coupling optical systems, three fibers and a condenser lens system is shown.

In this configuration example, the first and second coupling optical systems in the transmission system convert the light amount distribution in the light beam cross section, and the diaphragm members provided in the respective coupling optical systems further convert the light beams. The diameter is adjusted.

In FIG. 3, the light flux from the laser light source 11 enters the fiber C ₃ through the collimator lens system 16 including the lens L11 and is guided to the first coupling optical system 17. Further, the luminous flux emitted from the first coupling optical system 17 is guided to the second coupling optical system via the fiber D ₃ , and the luminous flux emitted from this is guided to the focusing optical system by the fiber E ₃ .

The first coupling optical system 17 includes a lens L12, a light quantity conversion element 12 and a lens L13 in order from the light source 11 side.
The second coupling optical system is also composed of a lens L22, a light quantity conversion element 22 and a lens L23 in this order from the light source 1 side, and the condenser lens system 18 is composed of a lens L14 and a lens L15. Is.

Further, as in the above embodiment, the coupling optical system 1
7, 27, and the light quantity conversion elements 12, 22 and the lens L13,
The diaphragm members 13 and 2 for adjusting the diameter of the light beam
3 are provided respectively.

Further, among the three fibers, at least two fibers C ₃ and D ₃ are SI type fibers which make the intensity distribution on the exit end surface uniform, but the fiber E ₃ is SI. Type or GI type.

In the present embodiment having such a structure, the light beam emitted from the light source 1 enters the fiber C ₃ via the lens L11 of the collimator lens system 16. Since the fiber C ₃ is of the SI type as described above, the light beam emitted through the fiber C ₃ is converted into a light beam having a uniform light amount distribution in the light beam cross section, and then is transmitted to the first coupling optical system 17. Incident.

The coupling optical system 17 converts the light quantity distribution in the cross section of the luminous flux into a centralized form, and the diaphragm member 13 provided in the coupling optical system 17 reduces the luminous flux diameter. As in the example, even if the outer diameter of the light beam is reduced, the loss of light quantity is small, and the emission NA from this is small.
Needless to say, can be made smaller.

Then, the light flux whose light volume distribution and light flux diameter are adjusted here enters the fiber D ₃ . Since this fiber D _{3 is} also an SI type fiber, the light beam emitted through the fiber D ₃ is converted again into a light beam having a uniform light quantity distribution.

The light beam emitted from the fiber D ₃ enters the second coupling optical system 27. This second coupling optical system 27
As a result, the light quantity distribution in the cross section of the light flux is converted again into a shape concentrated in the center, and the diaphragm member 23 provided in the second coupling optical system 27 reduces the effective diameter of the light flux.

Further, after entering the fiber E ₃ and being transmitted, it enters the condenser lens system 18. Then, the light flux that has entered the condenser lens system 18 has a lens L14 and a lens L14.
15 and a processing spot 1 is formed on the processing surface 15 by being condensed.
It is irradiated as 4.

As described above, in this embodiment, the light amount distribution and the light beam diameter of the light beam cross section are adjusted every time different fibers are connected. Then, similarly to the above-described first embodiment, the effective diameter of the light beam is reduced by using the diaphragm member, so that (substantially) the lens disposed after the diaphragm member can be used.
The magnification is reduced.

Specifically, the diaphragm member 13 and the diaphragm member 2
3, after making the light flux diameter after transmission 0.8 times that before transmission, the magnification of each of the lens L13 and the lens L13 arranged immediately after the diaphragm member 13 and the diaphragm member 23 is changed to reduce the emission NA, A fiber C ₃ and a fiber D _{3 on} which a light beam is incident after passing through the coupling optical systems 17 and 27.
The diameter of each is small.

With such a configuration, the light amount distribution and the luminous flux diameter of the luminous flux cross section are adjusted twice so that the diameter of the final focused spot 14 becomes 0.9 times or 0.8 times that of the conventional example. The light amount loss amount LOSS at the time of is compared with the conventional example. As a comparative example, Table 4 shows the light amount loss amount LOSS when only the light flux cross-sectional diameter is adjusted by the diaphragm member (the light amount distribution conversion is not performed). (However, the standard value is 1 when the diameter of the focused spot is not reduced at all.)

[0129]

[Table 4]

According to Table 4, in the conventional method, the amount of light loss is 18.5 when the diameter of the focused spot 4 is 0.9 times.
(%) Is very large, whereas the light amount loss amount in the embodiment of the present invention is 0.5 (%), which means that the light amount loss amount LOSS can be significantly reduced. P is also strong at 110.0 (%).

Further, when the diameter of the focused spot 4 is 0.8 times, similarly, in the conventional method, the light amount loss amount is 34.4.
(%), The light amount loss amount in the present invention is 1.0 (%), which means that the light amount loss amount LOSS can be significantly reduced. P is also quite strong at 149.3 (%). Here, Table 5 shows a specific configuration example of the laser processing apparatus according to the example of the present invention and the comparative conventional example when the diameter of the focused spot 14 is 0.8 times.

[0132]

[Table 5]

However, the core diameter of the fiber C ₃ is φC,
The NA of the fiber C ₃ is αC, the effective NA of the fiber C ₃ adjusted by the diaphragm member 13 is αC ′, and the lens L1.
The focal length of 2 is f12, and the focal length of the lens L13 is f1.
3, the imaging magnification of the first coupling optical system is mCD, fiber D
₃ of the core diameter [phi] D, .alpha.D the NA of the fiber D _3, .alpha.D the effective NA of the fiber D _3, which is adjusted by the diaphragm member 23 ', the focal length of the lens L22 f22, lens L2
The focal length of 3 is f23, and the imaging magnification of the second coupling optical system is m
DE, focal length of lens L14 is f14, lens L15
F15, the imaging magnification of the condensing lens system is m, the diameter of the condensing spot 4 on the processed surface is φ0, the condensed light beam NA to the processed surface is α0, the light amount loss amount is LOSS, and the luminous flux is completely Let P be the average irradiation energy per unit area on the processed surface when 100% is set without light shielding.

In the configuration example 3, the fibers are spliced twice by the first coupling optical system 17 and the second coupling optical system 27, and the light quantity distribution and the luminous flux diameter in the luminous flux cross section at the time of each splicing. Is being adjusted. Each coupling optical system 1
In Nos. 7 and 27, the effective diameter of the luminous flux is reduced by the diaphragm members 13 and 23 after the light quantity distribution in the cross section of the luminous flux is converted, and the magnification of the lenses L13 and L23 arranged after the diaphragm members 13 and 23 is reduced. As a result, the effective diameter of the luminous flux is reduced.

Therefore, the reduced luminous flux is reduced to a small N
Since the light can be transmitted to the next fiber by A, even if it is incident on the fiber D ₃ or the fiber E ₃ having a smaller diameter than the fiber C ₃ , the light quantity loss can be suppressed and the light is propagated by this. This is an example in which the focused spot diameter is reduced by a light beam having a small diameter.

Further, the configuration example 4 is an example in which the coupling optical system of the present invention is used between the fiber D ₃ and the fiber E ₃ with the same configuration. In this configuration example 4, only the coupling optical system 27 provided between the fiber D ₃ and the fiber E ₃ is used to adjust the light amount distribution and the light beam diameter in the cross section of the light beam.

Therefore, in the coupling optical system 27, after the light amount distribution of the light beam cross section is converted, the aperture amount of the aperture member 23 is
The effective diameter of the luminous flux is reduced to about twice that of the above-described configuration example 3, and the lens L23 arranged after the diaphragm member 23 is used.
The effective diameter of the luminous flux is reduced by decreasing the magnification of. Furthermore, this reduced luminous flux is converted into the fiber D
_This is an example in which the light is emitted from the fiber E ₃ having an effective NA smaller than ₃ and the light spot from this is used to reduce the focused spot diameter.

Conventional example 3 and conventional example 4 are combined optical system 1
This is an example in which the light quantity conversion elements 12 and 22 are not used in the reference numerals 7 and 27. In the conventional example 3, the light quantity distribution in the cross section of the light flux remains unchanged, and the diaphragm members 13 provided in the coupling optical systems 17 and 27
After reducing the effective diameter of the luminous flux by 23, the diaphragm member 1
This is an example in which the focusing spot diameter is reduced twice by reducing the magnification of the lenses L13 and L23 arranged after 3 and 23. Conventional Example 4 is an example in which a light beam is focused on the processed surface without reducing the focused spot diameter with the same arrangement configuration.

As is clear from Table 4 described above, in order to reduce the diameter of the condensed light spot 14 by 20%, the light amount loss amount is 34.4% in the conventional example, whereas the configuration of the present invention is used. In Example 3, the amount of light can be extremely reduced to 2%, and also in the configuration example 4, the amount of light loss can be reduced to 4%, which is very small compared to the conventional case.

From the comparison between the configuration example 3 and the configuration example 4,
It can be seen that it is more efficient to adjust the light quantity distribution and the light flux diameter of the light flux cross section twice or more than to adjust the light quantity distribution and the light flux diameter of the light flux cross section at once.

Further, similarly, the processing power P in the configuration example 3 of the present invention is also considerably strong at 149.3 (%), which is also high when the light quantity distribution and the light flux diameter of the light flux cross section are adjusted at once. It is stronger than 146.3 (%).

As described above, according to the embodiment of the present invention, since the optical system for joining the fibers is equipped with the light quantity conversion element, the light flux is changed to the next fiber in the state where the light quantity distribution at the joint is converted. Is incident. Therefore, when using a fiber having a small core diameter as the fiber on the output side, a substantially incident NA can be obtained by using a diaphragm member or the like for reducing the light beam diameter.
Is smaller and the loss of light quantity in the fiber is suppressed.

Further, since the condenser lens having a small magnification can be used by reducing the diameter of the light beam, there is an advantage that a smaller condensed spot can be formed. For this reason, a finer focused spot with high processing strength can be obtained, so if it is applied to the laser enclosing device as in this embodiment,
This makes it possible to construct an apparatus with excellent processing characteristics.

Although the diaphragm means is used as the means for adjusting the diameter of the light beam in this embodiment, the peripheral portion of the light beam is effectively shielded and the diameter of the light beam emitted from the coupling optical system is reduced so that the next optical It is not limited to the diaphragm means as in this embodiment as long as it guides the member.

For example, in the light flux emitted from the coupling optical system of the present invention, the light quantity density at the peripheral portion is generally low, so that the peripheral portion is removed by the rim of the lens or the outer diameter portion of the core, so that an effective portion is obtained. An optical image in which only the light flux passes can be considered.

[0146]

As described above, according to the fiber coupling optical system of the present invention, the light quantity distribution state of the light beam guided from the light source is converted and guided to the next optical member. Therefore, it is possible to construct an optical transmission system with less loss of light amount.

Further, since the light beam system can be reduced by effectively utilizing only the portion having a high optical power density, a converging optical system with a small magnification can be used. Therefore, when applied to a laser processing apparatus or the like, the processing accuracy and processing can be improved. A highly efficient device can be constructed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a laser processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a light quantity distribution diagram of a focused spot when the SI type is used for the fiber B in the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a laser processing apparatus according to a second embodiment of the present invention.

FIG. 4A is an explanatory diagram showing a configuration of a light quantity conversion element and a diaphragm member of the present invention, and FIG. 4B is a view showing S1 in the coupling optical system.
It is a light quantity distribution map in a cross section, and (c) is a light quantity distribution map in a S2 cross section in the coupling optical system.

FIG. 5 is an explanatory diagram showing a second configuration example of the light amount conversion element of the present invention.

FIG. 6 is an explanatory diagram showing a third configuration example of the light amount conversion element of the present invention.

FIG. 7A is a schematic configuration diagram of a conventional laser processing apparatus in which one light source has one processing surface, and FIG. 7B shows two processing surfaces for one light source. It is a schematic block diagram of the conventional laser processing apparatus when there is.

[Explanation of symbols]

1, 11, 31, 41 Light source 2, 12, 22, 2a Light amount conversion element 3, 13, 23, 3a, 33, 43a, 43b Diaphragm member 4, 14 Focused spot 5, 15, 35, 45, 55 Processed surface 6, 16 Collimator lens system 7, 17, 27, 7a, 37, 47a, 47b Coupling optical system 8, 18, 48, 58 Condensing lens system AE fiber L1, L11 Collimator lens L2, L3 Coupling lens L12, L13 Coupling lens L22, L23 Coupling lens L2a, L3a Coupling lens R1 First conical lens R2 Second conical lens

Claims (4)

[Claims] 1. An optical transmission optical system for guiding a light beam from a light source, which is a fiber coupling optical system for coupling a fiber with another optical member provided in the transmission system, wherein the transmission is performed in the transmission system. A fiber-coupling optical system comprising: a light quantity distribution conversion means for dispersing a light flux of a central region in a cross section of the generated light flux to a peripheral region and concentrating the light flux of the peripheral region in the cross section to the central region. 2. The light quantity distribution conversion means has a first conical optical element and a second conical optical element which are sequentially arranged along a traveling direction of a light beam, and the first and second conical optical elements are provided. 2. The conical optical elements are arranged such that their apex angle portions face each other, and are arranged such that the central axis of the element and the central axis of the light beam coincide with each other. The fiber-coupled optical system described in 1. 3. The first and second conical optical elements have a condensing position of the first conical optical element on the central axis of the light flux and a vertex portion of the second conical optical element. 3. The elements are arranged so as to coincide with each other.
The fiber-coupled optical system described in 1. 4. The fiber coupling optics according to claim 1, further comprising a light beam diameter adjusting means for adjusting a diameter of the light beam whose light amount distribution is converted by the light amount distribution converting means. system.