JP5019788B2 - fθ lens - Google Patents

Description

  The present invention relates to an fθ lens suitable for use in an optical device, particularly a laser processing machine, and more particularly to an fθ lens in which three or more single lenses are aligned inside a cylindrical case with the optical axis direction aligned. .

  When the focal length of the fθ lens is f, the fθ lens emits light incident at an angle θ with respect to the optical axis of the fθ lens from the optical axis of the plane perpendicular to the optical axis at the focal point to the position of fθ. It has characteristics. Since it is difficult to realize such characteristics with a single lens, a single fθ lens is formed by combining a plurality of lenses (usually three or more, each of which is hereinafter referred to as a “single lens”). It is configured.

  FIG. 3 is a front sectional view of a conventional fθ lens. In the case of the illustrated fθ lens 30, the lens includes a first single lens 1A, a second single lens 1B, and a third single lens 1C. The single lens 1A, 1B, 1C has a circular outer shape, and SeZn, Ge (in the case of CO2 laser) or SiO2 (in the case of UV laser) is adopted as the material. The single lenses 1A, 1B, and 1C are positioned inside the case 10 so that the optical axis O is coaxial. The case 10 has a first recessed portion 6a formed from one side end portion, and a stepped second recessed portion 6b and a third recessed portion that gradually become smaller in diameter from the other side end portion toward the back. 6c is formed.

  An annular nut 3a that is screwed into a threaded portion 2a provided on the case 10 has a single lens 1A provided on the cylindrical case 10 via an annular packing 4a made of rubber or plastic and a metal washer 5a. It is positioned and fixed to the flat surface 6ah of one recess 6a. The annular packing 4a prevents the surface of the single lens 1A from being damaged by the washer 5a, and biases the single lens 1A to the flat surface 6ah. The diameter of the cylindrical surface 6av of the recess 6a is slightly larger than the diameter of the single lens 1A.

  An annular nut 3b that is screwed into a threaded portion 2b provided in the case 10 has a single lens 1B provided in a cylindrical case 10 via an annular packing 4b made of rubber or plastic and a metal washer 5b. It is positioned and fixed to the flat surface 6bh of the second recess 6b. The annular packing 4b prevents the surface of the single lens 1B from being damaged by the washer 5b and biases the single lens 1B toward the flat surface 6bh. The diameter of the cylindrical surface 6bv of the recess 6b is slightly larger than the diameter of the single lens 1B.

  An annular nut 3c that is screwed into a threaded portion 2c provided in the case 10 has a single lens 1C provided in a cylindrical case 10 via an annular packing 4c made of rubber or plastic and a metal washer 5c. 3 is positioned on the flat surface 6ch of the recess 6c. The annular packing 4c prevents the surface of the single lens 1C from being damaged by the washer 5c, and biases the single lens 1C toward the flat surface 6ch. The diameter of the cylindrical surface 6cv of the recess 6c is slightly larger than the diameter of the single lens 1C.

  If the optical characteristics (hereinafter simply referred to as “characteristics”) of the assembled fθ lens 30 deviate from the desired characteristics, for example, the annular nut 3a is removed and the single lens 1A is rotated in the circumferential direction. Adjustment work such as re-fixing at a position where desired characteristics can be obtained.

  As a specific example of the characteristics required for the fθ lens, for example, when a laser beam having a circular outer shape is incident on the fθ lens, the roundness of the laser beam at the imaging position is 90% or more. .

JP 2005-165210 A

  Incidentally, the shapes and characteristics of the single lenses 1A, 1B, and 1C vary, and the flatness of the flat surfaces 6ah, 6bh, and 6ch also varies. In particular, when the number of single lenses constituting the fθ lens is increased, it is difficult to polish and finish the surface on the heel side away from the side end portion of the case 10 such as the flat surface 6bh. Therefore, when the cutting surface is not subjected to grinding, the flatness is lowered and the single lens 1B may be inclined. When the single lens 1B is tilted, for example, when the lens diameter of the fθ lens 30 is 100 mm, even if a hole having a roundness of 90% or more can be machined in the center and four corners of the machining area range 30 mm × 30 mm, In other positions, the roundness may be less than 90%.

  Further, when the concentricity of the recesses 6a, 6b, and 6c is shifted, the roundness may be less than 90% in the entire processing region.

  If the annular nuts 3a, 3b, 3c are tightened too much, partial distortion occurs in the single lenses 1A, 1B, 1C. The distortion generated in the lens can be confirmed using an interferometer. Therefore, when distortion occurs in the single lenses 1A and 1C arranged on the surface side, it is easy to remove the distortion. However, it is troublesome to check the distortion of the single lens 1B arranged on the back side. Further, after the single lens 1C is assembled, the distortion of the single lens 1B disposed inside cannot be confirmed. For this reason, not only did assembly take time, but the characteristics varied.

  An object of the present invention is to solve the above-described problems, to provide an fθ lens that is easy to assemble and has uniform characteristics.

In order to solve the above problems, the present invention provides an fθ lens (30) in which three or more single lenses (1A, 1B, 1C) are aligned in a cylindrical case with the optical axis direction aligned.
A plurality of storage cases (50A, 50B, 50C) (50C, 50D) for holding one or two single lenses ;
The first storage case (50C), which is one of the plurality of storage cases, has a first recess (6c) formed on one side end thereof from the opened one side end surface, and the other side. A second recess (21) is formed at the end from the other end face opened ,
The single lens (1C) is accommodated and fixed integrally in the first recess (6c), and the second storage case (50B) is accommodated and fixed integrally in the second recess (21). ,
A plurality of the single lenses (1A, 1B, 1C) are integrally connected in the optical axis direction.
The fθ lens is characterized by this.

The second storage case (50B) is formed with a third recess (6b) at one side end portion from the opened one side end surface and at the other side end portion from the opened other side end surface. 4 recesses (20), the single lens (1B) is stored and fixed integrally in the third recess (6b), and a third storage case ( 50A) or a single lens (1A) is housed and fixed integrally.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on the structure of a claim by this.

  Since the storage case only holds one or two single lenses, it is easy to check the distortion, and it is easy to readjust even when distortion occurs. Moreover, since the depth of each storage case is small, the flatness of the surface supporting the single lens can be easily improved. As a result, assembly is easy and variation in characteristics can be reduced.

  FIG. 1 is a front cross-sectional view of an fθ lens comprising three single lenses according to the present invention, and those having the same or the same functions as those in FIG.

  The fθ lens 30 has a plurality of storage cases (hereinafter simply referred to as cases) 50A, 50B, and 50C each storing a single lens.

  The case 50A includes a screw portion 2a and a recess 6a inside, and the outer diameter on the side engaged with the case 50B is D1, and a circumferential groove is provided at a position facing the screw hole 7b provided in the case 50B. 9a is formed. The large diameter portion is provided with a bottomed hole 50Ab coaxial with the screw hole 41 provided in the case 50B when combined with the case 50B, and a through hole 50Ac coaxial with the bottomed hole 50Ab. As with the screw holes 41, the bottomed holes 50Ab and the through holes 50Ac are provided at three locations at 120 ° intervals in the circumferential direction. The flatness of the flat surface 6ah is 1 μm or less by grinding. The diameter of the cylindrical surface 6av is slightly larger than the outer diameter of the single lens 1A. The flatness of the bottom surface 50Aa is 1 μm or less by grinding. The single lens 1A is positioned and fixed to the flat surface 6ah by an annular nut 3a through an annular packing 4a and a washer 5a.

The case 50B has a threaded portion 2b and a recessed portion 6b formed inside from one end portion, and a recessed portion 20 that engages with the case 50A from the other end portion. The outer diameter of the side which engages the casing 50C is D2, the groove 9b in the circumferential direction is formed at a position opposite to the screw hole 7 c provided in the case 50C. The diameter of the recess 20 is 0.5 mm larger than the outer diameter D1 of the case 50A. The diameter of the cylindrical surface 6bv is slightly larger than the outer diameter of the single lens 1B. A threaded portion 7b is provided between the cylindrical surface 20v of the recess 20 and the outer surface of the case 50B. Three screw portions 7b are provided at intervals of 120 ° in the circumferential direction. The large diameter portion is provided with a bottomed hole 50Bb that is coaxial with the screw hole 42 provided in the case 50C when combined with the case 50C, and a through hole 50Bc that is coaxial with the bottomed hole 50Bb. The bottomed holes 50Bb and the through-holes 50Bc are provided at three places at intervals of 120 ° in the circumferential direction like the screw holes 42. Three screw holes 41 are provided in the flat surface 20h at intervals of 120 ° in the circumferential direction. The flatness of the flat surface 6bh and the flat surface 20h of the recess 20 is 1 μm or less.

  The single lens 1B is positioned and fixed to the flat surface 6bh by the annular nut 3b through the annular packing 4b and the washer 5b. The bolt 8b fixes the case 50A to the case 50B.

The case 50C has a threaded portion 2c and a recessed portion 6c formed inside from one end portion, and a recessed portion 21 that engages with the case 50B from the other end portion. The diameter of the recess 21 is 0.5mm larger than the outer diameter D2 of the case 5 B. The flatness of the flat surface 6ch and the flat surface 21h of the recess 21 is 1 μm or less. The diameter of the cylindrical surface 6cv is slightly larger than the outer diameter of the single lens 1C. A threaded portion 7c is provided between the cylindrical surface 21v of the recess 21 and the outer surface of the case 50C. Three screw portions 7c are provided at intervals of 120 ° in the circumferential direction. Three screw holes 42 are provided in the flat surface 21h at intervals of 120 ° in the circumferential direction.

  The single lens 1C is positioned and fixed to the flat surface 6ch by an annular nut 3c through an annular packing 4c and a washer 5c. The bolt 8c fixes the case 50B to the case 50C.

  Next, the assembly procedure will be described.

  First, the single lens 1A is inserted into the recess 6a, the annular packing 4a and the washer 5a are sandwiched, and the annular nut 3a is tightened to position the single lens 1A in the optical axis direction. At this time, the tightening force of the annular nut 3a is set to 0.98 N at the maximum. In this way, the single lens 1A can be positioned in the optical axis direction and the rotation direction, and distortion generated in the single lens 1A can be prevented.

  Next, in a state where the single lens 1A is incorporated in the case 50A, it is confirmed by using an interferometer that the single lens 1A is not distorted. And when distortion has generate | occur | produced, after reducing the fastening force of the annular nut 3a, for example, the presence or absence of distortion is confirmed again. At this time, since the flatness of the flat surface 20h is 1 μm or less, it is not necessary to rotate the position of the single lens 1A in the case 50A in the rotation direction.

  Thereafter, similarly, the single lens 1B is incorporated into the case 50B, and the single lens 1C is incorporated into the case 50C.

  Next, the lower end portion of the case 50A is inserted into the recess 20 of the case 50B, and the case 50A is fixed to the case 50B with the bolts 8b. Next, the lower end portion of the case 50B is inserted into the recess 21 of the case 50C, and the case 50B is fixed to the case 50C with the bolts 8c. By tightening the bolts 8b and 8c, the cases 50A, 50B, and 50C are substantially integrated to form the fθ lens 30.

  Next, the characteristics of the fθ lens 30 are confirmed. For example, when the optical axis of the single lens 1A is deviated from the optical axis O, the bolt 8b is removed and the case 50A is placed in a direction perpendicular to the optical axis O. Move to match the optical axis. In this state, a push screw (not shown) is screwed into each of the screw holes 7b, and the case 50A is fixed to the case 50B.

  As described above, according to the present invention, since the single lenses 1A, 1B, and 1C are fixed to the cases 50A, 50B, and 50C, it is easy to confirm the presence or absence of distortion. Since no distortion occurs in the single lenses 1A, 1B, and 1C arranged inside, desired characteristics can be obtained by simply connecting the cases 50A, 50B, and 50C.

  Further, the adjustment work when assembling the whole is only to make the optical axes coincide, and the assembly work is easy.

  In addition, since the position of the surface for positioning the single lens can be made shallower from the end, grinding is easy and the flatness of the positioning surface can be made excellent. Therefore, it is possible to prevent the optical axis from falling when the single lens is fixed.

  Also, when it is desired to adjust the focal length for some reason, it is only necessary to change the intervals of the cases 50A, 50B, 50C instead of changing the positions of the single lenses 1A, 1B, 1C in the direction of the optical axis O, and the work is easy It is.

  Even if the cases 50A, 50B, and 50C have a defect (for example, the flatness of the flat surface 6bh is poor), the correction is easy.

  In this embodiment, the cases 50A, 50B, and 50C are fixed using the bolts 8b and 8c. However, a screw (not shown) may be screwed into the screw holes 7b and 7c and fixed. In this case, it is not necessary to provide the bottomed holes 50Ab and 50Bb, the through holes 50Ac and 50Bc, and the screw holes 41 and 42.

  FIG. 2 is a front sectional view of an fθ lens showing a modification of the present invention.

In the fθ lens described with reference to FIG. 1, one single lens is fixed to one case. However, as shown in FIG. 2, the case 50 </ b> A and the case 50 </ b> B are integrated into a case 50 </ b> D. The single lens 1A and the single lens 1B may be fixed. Even if two single lenses are fixed to the case 50D, the presence or absence of distortion generated in each single lens can be confirmed from both sides in the optical axis direction .

  The assembly procedure is substantially the same as that in FIG.

  As described above, according to the present invention, the time required for assembly can be reduced to 1/2 to 1/3 of the conventional one.

  In addition, since the focal length can be uniform over the entire processing area, when processing a circular hole, the hole diameter does not change or the hole shape does not become an ellipse, and the processing quality is excellent. And the processing reliability is improved.

It is front sectional drawing of the f (theta) lens which concerns on this invention. It is front sectional drawing of the f (theta) lens which concerns on this invention. It is a front sectional view of a conventional fθ lens.

Explanation of symbols

30 fθ lens 1A single lens 1B single lens 1C single lens 50A ( third storage) case 50B ( second storage) case 50C ( first storage) case O optical axis
6a Lens storage recess
6b (Third) lens housing recess
6c (first) lens housing recess
20 (fourth) case or lens recess
21 (second) recess for storing case

Claims (2)

In an fθ lens in which three or more single lenses are aligned inside a cylindrical case with the optical axis direction aligned,
A plurality of storage cases for holding one or two single lenses ;
The first storage case, which is one of the plurality of storage cases, has a first recess formed in one end portion thereof from the opened one side end surface, and is opened in the other end portion. A second recess is formed from the other side end face ,
Storing the single lens in the first recess and fixing it integrally; and storing the second storage case in the second recess and fixing it integrally;
A plurality of the single lenses are integrally connected in the optical axis direction.
An fθ lens characterized by that. The second storage case has a third recess formed at one side end portion from the opened one side end surface, and a fourth recess formed at the other side end portion from the opened other side end surface. The single lens is housed and fixed integrally in the third recess, and the third housing case or single lens is housed and fixed integrally in the fourth recess.
The fθ lens according to claim 1.

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