GB2329723A

GB2329723A - Adjustably coupling light emitter and optical fibre using two lenses

Info

Publication number: GB2329723A
Application number: GB9816988A
Authority: GB
Inventors: Hiroshi Kanazawa
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1997-08-07
Filing date: 1998-08-05
Publication date: 1999-03-31
Also published as: JPH1152177A; DE19835902A1; GB9816988D0

Abstract

A coupling apparatus for coupling alight emitter 15 and an optical fiber 20 has a coupling lens including a first lens L1 which converges light emitted from the light emitter source and a second lens L2 which converges the light emitted from the first lens onto an end of the optical fiber. The first lens may be made integral with the light emitter through a first member 11. The second lens may be made integral with the optical fiber through a second member 12. The first member and the second member are interconnected so as to adjust the relative position therebetween. The method for adjusting a light emitter and an optical fiber through a coupling lens is also disclosed. The coupling apparatus may be used in a multi laser drawing apparatus (Fig 2).

Description

2329723 - 1 COUPLING APPARATUS OF LIGHT EMITTER AND OPTICAL FIBER AND

METHOD FOR ADJUSTING POSITION OF OPTICAL FIBER USING THE SAME The present invention relates to a coupling apparatus f or coupling a light emitter and an optical fiber via a coupling lens. The present invention also relates to a method for adjusting the position of the optical fiber relative to the light emitter using the same.

Laser drawing apparatuses using multi-laser beams have been proposed in which a group of light sources consisting of a plurality of laser emitters and a plurality of optical fibers are provided to increase drawing speed.

In a multi-laser beam drawing apparatus using optical fibers as a light source, the laser beam emitted from the semiconductor laser and made incident upon the incident surface of the optical fiber is partly reflected by the incident surface. If the reflected light is made incident upon the semiconductor laser, the laser emission is disturbed, thus' resulting in a change in the intensity of the laser beams. To avoid this, the incident surface of the - 2 optical fiber is cut along a plane inclined with respect to the center axis of the optical fiber to form an oblique incident surface, so that the light reflected thereby does not reach the semiconductor laser, as shown in Fig. 4.

In the prior art shown in Fig. 4, a laser diode (LD) 136 is secured, via LD holder 126, to a lens holder 116 which holds a coupling lens 156. The lens holder 116 is provided with an adjusting ring 166 secured thereto. An optical fiber 20 is held by a ferrule 196 so that the center axis of the optical fiber at the incident surface thereof is inclined with respect to the optical axis of the coupling lens 156 at a predetermined inclination angle. The ferrule 196 is press-fitted in the adjusting ring 166 which is secured to the lens holder 116. The incident surface of the optical fiber 20 is defined by an oblique surface 20a inclined at a predetermined inclination angle with respect to a plane perpendicular to the center axis thereof. The optical fiber 20 is held in such a way that the incident surface 20a thereof.is not normal to the optical axis 01.

The ferrule 196 which holds the optical fiber 20 is not parallel with the optical axis 01 of the coupling lens 156 and is moved in the direction parallel with the center axis of the optical fiber 20 to adjust the position of the incident surface (core surface) 20a of the optical fiber 20. However, since the direction of the movement of the optical fiber 20 is inclined with respect to the optical axis 01, if the ferrule 196 is slid to move the incident surface 20a to the focal point of the coupling lens 156, not only does the distance between the incident surface 20a and the coupling lens 156 in the optical axis direction change, but also the distance between the center of the incident surface 20a and the optical axis 01 also varies. Consequently, it is difficult to adjust the incident surface 20a of the optical fiber 20 to the focal point f of the coupling lens 156.

Moreover, to establish a highly precise positional relationship between the laser diode 136 and the optical fiber 20 at the connection therebetween, the LD holder 126 and the adjusting ring 166 are independently moved along the contact surfaces thereof with the lens holder 116 in the prior art. Upon completion of the adjustment, the LD holder 126 and the adjusting ring 166 are welded to the coupling lens holder 116 by, for example, YAG laser welding to prevent the accidental movement thereof.

However, even if the position of the adjusting ring 166 and the coupling lens holder 116 is precisely adjusted, a slight relative movement (1 - 3 Iem) therebetween could occur during the YAG laser welding. In particular, the core diameter of the single mode optical fiber decreases as the wavelength of the laser beams used therefor decreases. Consequently, if a positional error occurs upon assembling - 4 operation, the coupling efficiency is deteriorated.

Moreover, if the coupling apparatus is incorporated in a multiple-beam and fiber array laser scanner unit (LSU), irregularity in the emission power of the light sources and stability have a large influence on the image quality. Therefore, the laser beams emitted from the laser diode 136 must be stably and efficiently made incident upon the incident surface (core) 20a. of the optical fiber 20.

An object of the present invention is to provide a coupling apparatus which can stably and precisely couple a light emitter and an optical fiber via a coupling lens.

According to an aspect of the pr4sent invention, there is provided a coupling apparatus for connecting a light emitter and an optical fiber via a coupling lens, the coupling apparatus includes: at least a first lens which converges or diverges light emitted from the light emitter source and at least a second lens which converges the light emitted from the first lens onto an end surface of the optical fiber, the coupling lens constitutes the first lens and the second lens; a first member which supports and connects the first lens and the light emitter; and a second member which supports and connects the second lens and the orDtical fiber. The first member and the second member are interconnected so as to be relatively adjustable.

In this regard, the inventor has conceived that if the sensitivity to the adjustment during the assembling operation is reduced, error caused by the displacement of the components produced upon the securing operation can be eliminated or minimized.

Preferably, the magnification of the second lens is smaller than 1.

Preferably, the first member includes a first lens holder to which the first lens is attached and an LD holder to which a laser diode constituting the light emitter is attached, so that the LD holder is laser-welded to the first lens after the position of the LD holder is adjusted relative to the first lens holder.

Preferably, the second member includes a second lens holder to which the second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of the optical fiber is attached through the ferrule holder, wherein the adjusting ring is laser-welded to the second lens holder after Ithe position of the adjusting ring is adjusted relative to the second lens holder.

Preferably, the first member includes a first lens holder to which the first lens is attached, and an LD holder to which a laser diode constituting the l-igli,t em-.zter is attached, so that the LD holder is laser-welded to the 1L.J._-st - 6 lens after the position of the LD holder relative to the first lens holder is adjusted. Preferably, the second member includes a second lens holder to which the second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of the optical fiber is attached through a ferrule holder, so that the adjusting ring is laser- welded to the second lens holder after the position of the adjusting ring is adjusted relative to the second lens holder, the first and second lens holders being interconnected by screws upon completion of the position adjustment thereof.

According to another aspect of the present invention, there is provided a method for adjusting the position of a light emitter and an optical fiber via a coupling lens in a coupling apparatus. The coupling apparatus includes: at least a first lens which converges or diverges light emitted from the light emitter source and at least a second lens which converges the light emitted from the first lens onto an end surface of the optical fiber, the coupling lens constitutes the first lens and the second lens; a first member which supports and connects the first lens and the light emitter; and a second member which supports and connects the second lens and the optical fiber. The method includes: securing the first lens and the light emitter to the first member after the relative position of the first - 7 lens and the light emitter is adjusted; securing the second lens and the optical f iber to the second member after the relative position of the second lens and the optical fiber is adjusted; and securing the first member and the second member after the relative position of the first member and second member is adjusted.

Preferably, the magnification of the second lens is smaller than 1.

Preferably, the first member includes a first lens holder to which the first lens is attached and an LD holder to which a laser diode constituting the light emitter is attached, and wherein the LD holder is laser-welded to the first lens after the position of the LD holder is adjusted relative to the first lens holder.

Preferably, the second member includes a second lens holder to which the second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of the optical fiber is attached through a ferrule holder, and wherein the adjusting ring is laser-welded to the second lens holder after the position of the adjusting ring is adjusted relative to the second lens holder.

Preferably, the first member includes a first lens holder to which the first lens is attached and an LD holder to which a laser diode as the light emitter is attached, so that the LD holder is laser-welded to the first lens after the position of the LD holder is adjusted relative to the first lens holder. The second member includes a second lens holder to which the second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of the optical fiber is attached through a ferrule holder, so that the adjusting ring is laser-welded to the second lens holder after the position of the adjusting ring relative to the second lens holder is adjusted, the first and second lens holders being interconnected by screws upon completion of the position adjustment thereof.

An example of the present invention will now be discussed below in detail,with reference to the accompanying drawings, in which:- Figure 1 is an enlarged longitudinal sectional view of a coupling apparatus of a light emitter and an optical fiber of an embodiment of the present invention; Figure 2 is a perspective view of a multiple laser drawing apparatus to which a coupling apparatus of a light emitter and an optical fiber of the present invention is applied; Figure 3 is an exploded perspective view of an end portion of a multiple laser source using optical fibers; and Figure 4 is an enlarged longitudinal sectional view of a known coupling apparatus of a light emitter and an optical f iber.

Referring to Figs. 2 and 3, a multi-laser drawing apparatus to which an optical fiber coupling apparatus of the present invention is applied will be discussed below by way of example.

A multi-laser drawing apparatus shown in Fig. 2 includes a multi-laser source having a plurality of laser sources 10 to which optical fibers 20 are coupled. The laser sources 10 are secured in the form of an array. The optical fibers 20 are held at their emission ends by a fiber array structure (not shown) within a fiber holder block 44, so that the emission ends of the optical fibers 20 are aligned along a line at an equi-pitch (distance) smaller than the distance (pitch) of the remaining portions of the optical fibers.

The laser beams emitted from the laser sources 10 are transmitted througl the optical fibers 20 and are emitted from the fiber holder block 44. The laser beams emitted from the fiber holder block 44 are emitted toward a rotating polygonal mirror 37 via a collimating lens 31, a reflection mirror 33, and a beam shaping optical system 35. The laser beams reflected and deflected by the polygonal mirror 37 are transmitted through an f 0 lens group 39; are reflected by a - 10 mirror 41; and are made incident upon an outer peripheral surface of a photosensitive drum to scan the same. In the illustrated embodiment, the polygonal mirror 37 is driven at a constant speed by a spindle motor 38, and the laser sources 10 are turned ON or OFF in synchronization with a pixel clock which is in turn synchronized with the rotation of the spindle motor 38 and in accordance with drawing data.

Fig. 3 is an exploded view of the fiber holder block 44. As can be seen in Fig. 3, the emission ends 20b of the optical fibers 20 are spaced at a predetermined distance and are interconnected to form a fiber array so that the laser beams emitted from the emission ends 20b reach respective points on a drawing surface spaced at a predetermined distance from one another in the main scanning direction and sub-scanning direction. Namely, the optical fibers 20 are received in respective parallel V-shaped grooves 45a of a Vgroove block 45 and are pressed by a retainer block 46. The optical fibers 20, the V-groove block 45 and the retainer block 46 are adhered together. The emission ends 20b of the optical fibers 20 are ground together with the ends 45b and 46b of the blocks 45 and 46 on the emission side to define a plane normal to the central axes of the fibers 20.

The present invention can be applied to a multi-laser beam drawing apparatus constructed as above. Fig. 1 shows an enlarged longitudinal sectional view of an embodiment of 1 - J1 - the present invention.

In this embodiment, the coupling lens is composed of an LD lens L1 and a f iber lens L2. The LD lens Ll of this embodiment is a condenser lens of small numerical aperture (NA) which condenses the laser beams emitted from the laser diode 15, the laser diode 15 being the light source. The fiber lens L2 is a condenser lens which converges the laser beams emitted from the LD lens Ll onto the incidence surface of the optical fiber. The adjustment sensitivity of the fiber lens L2 is reduced as the magnification thereof is not larger than 1.

Note that in the following description, the Z-axis is identical to or parallel with the optical axis 0 of the laser diode 15 or the lenses L1 and L2, and the X-Y axes extend in a plane perpendicular to the Z-axis and do not refer to a specific direction. The LD lens L1 is mounted to a first lens holder (first member) 11 and the fiber lens L2 is mounted to a second lens holder (second member) 12. The first lens holder.11 is equipped with a lens receiving recess (hole) 11a in which the LD lens Ll is fitted and held and a light path hole llb in which the laser beams emitted from the LD lens L1 pass. The second lens holder 12 is equipped with a fiber lens receiving recess (hole) 12a in which the fiber lens L2 is fitted and held and a light path hole 12b whose diameter is gradually decreased from the end - 12 adjacent to the lens receiving recess 12a toward the other end. The first and second lens holders 11 and 12 are relatively slidable, i.e., the position of the first and second lens holders are adjustable in the XY plane when they abut against each other. The first and second lens holders 11 and 12 can be interconnected and secured by means of a plurality of screws 14.

The laser diode 15 is inserted in and secured to a cylindrical LD holder (first member) 13. The LD holder 13 abuts against the end surface 11c of the first lens holder 11 so as to relatively slide thereon, i.e., to adjust the position in the X-Y plane. The laser diode 15 and the LD lens L1 are aligned and after the alignment is completed, the contact surfaces of the LD holder 13 and the first lens holder 11 are secured, for example, by YAG laser welding.

The optical fiber 20, with the incidence end straightened, is inserted in a ferrule (second member) 19. The end face of the ferrule 19 and the incidence surface (core surface) 20a. of the optical fiber 20 are ground together so as to define an oblique plane inclined at a predetermined angle with respect to the direction perpendicular to the center axis 01 of the optical fiber located in the ferrule 19. The cylindrical ferrule 19 i inserted in and secured to an oblique hole 18a formed in a ferrule holder (second member) 18. The oblique hole 18a is - 13 inclined with respect to the axis of the ferrule holder 18. The ferrule holder 18 is press-fitted in a cylindrical ferrule ring (second member) 17 which is in turn pressfitted in an adjusting ring (second member) 16.

The cylindrical adjusting ring 16 abuts against end face 12c of the cylindrical portion of the second lens holder 12 and is secured thereto, for example, by YAG laser welding, after the position adjustment therebetween is completed.

The ferrule ring 17 is inserted in the adjusting ring 16 in a direction parallel with the optical axis 0 and is secured to the adjusting ring 16, for example, by YAG laser welding after the distance between the incidence surface 20a and the fiber lens L2 is adjusted (focus adjustment). The ferrule holder 18 is press-fitted in the ferrule ring 17 movable in a direction parallel with the optical axis 0. Namely, the ferrule 19 is held relative to the second lens holder 12 so as to be movable in the direction parallel with the optical axis 0 while maintaining a predetermined inclination angle of the longitudinal center axis 01 thereof with respect to the optical axis 0.

The assembling and adjusting operations will be discussed below in more detail. one of the most significant features of the illustrated embodiment resides in that the first lens holder 11 which holds the laser diode 15 and the LD lens L1 and the second lens holder 12 which holds the optical fiber 20 and the fiber lens L2 are separately adjusted and assembled, and thereafter, the first lens holder 11 and the second lens holder 12 are adjusted relative to each other and are interconnected by, for example, screws 14.

<step l> The lenses L1 and L2 are aligned with and secured to the lens holders 11 and 12, respectively, by means of an adhesive or the like.

The optical fiber 20 is inserted in and secured to the ferrule 19, the aligning of which determines the angular position of the optical fiber 20 and the through-hole of the ferrule 19. The incidence surface 20a of the optical fiber 20 is ground together with the ferrule 19 to define an oblique planar surface which is inclined at a predetermined angle with respect to a direction perpendicular to the longitudinal axis 01.

<step 2> The laser diode 15 is press-fitted in the LD holder 13 at a predetermined position. The LD holder 13 and the first lens holder 11 are mounted to an adjustment tool to adjust the position of the laser diode 15 in the directions of the X, Y and Z axes. Upon completion of the adjustment, the LD holder 13 and the laser diode 15 are secured to each other - is - at the contact surfaces therebetween, for example, by YAG laser welding.

<step 3> The ferrule 19 is press-fitted in the ferrule holder 18; the ferrule holder 18 is press-fitted in the ferrule ring 17; the ferrule ring 17 is inserted in the adjusting ring 16; and the adjusting ring 16 and the second lens holder 12 are mounted to a coupling adjustment tool. Thereafter, the position of the incidence surface 20a of the optical fiber 20 relative to the ferrule holder 18 in the directions of the X, Y, and Z axes are adjusted.

<step 4> Subsequently, position adjustment of the incidence surface 20a of the optical fiber 20 by moving the ferrule ring 17 in the Z axis direction is concurrently carried out with the adjustment of the adjusting ring 16 in the X and Y axial directions relative to the second lens holder 12 so that the maximum light flux from the laser diode 15 is made incident upon the iwident surface 20a of the optical fiber 20. Upon completion of the adjustment, the ferrule ring 17 and the adjusting ring 16 are secured to each other, and the adjusting ring 16 and the second lens holder 12 are secured to each other, for example, by YAG laser welding.

<step 5> The first lens holder 11 and the second lens holder 12 16 are brought into contact with each other and are mounted to a tool to adjust the relative position therebetween in the X and Y axial directions. Namely, the displacement caused during YAG laser welding at step 4 is corrected. Thereafter, the first and second lens holders 11 and 12 are interconnected by the screws 14 which are then secured by an adhesive.

Instead of steps 3, 4 and 5 mentioned above,the following steps are also possible with the present embodiment.

1. The first lens holder 11 and the second lens holder 12 are secured by the screws 14 aligning the optical axes of the lens L1 and the lens L2.

2. The adjusting ring 16, the ferrule ring 17 and the second lens holder 12 are held by special coupling-adjustment tools in order for these members to be in the positions shown in fig. 1.

3. The position adjustment of the ferrule ring 17 relative to the adjqsting ring 16 in the Z axis direction is concurrently carried out with the adjustment of the adjusting ring 16 in the X and Y axial directions relative to the sec-und lens holder 12 so that the maximum light flux from the laser diode 15 is made incident upon the incident surface 20a of the optical fiber 20. Upon completion of the adjustment, the ferrule ring 17 and the adjusting ring 16 - 17 are secured to each other, and the adjusting ring 16 and the second lens holder 12 are secured to each other, for example, by YAG laser welding.

4. It is possible to readjust the relative position between the first lens holder 11 and the second lens holder 12 by loosening the screws 14 to eliminate or adjust any displacement caused during the YAG laser welding.

As mentioned above, with the present embodiment, since the positions of the LD lens L1 and the fiber lens L2 are independently adjusted, the adjustment is less sensitive than the adjustment of a single lens, thus resulting in a precise position adjustment. Moreover, even if a positional displacement takes place, the positional deviation of the laser beams incident upon the incidence surface 20a of the optical fiber is small due to the low adjustment sensitivity. Thus, not only can reliability be enhanced but also the assembling operation can be simplified.

Furthermore, in the illustrated embodiment, if the laser diode 15 is broken, it is possible to replace the same with a new one for each first lens holder 11. The adjustment after the replacement can be carried out in the same way as in step 7. Consequently, the replacement of the laser diodes is facilitated.

The present invention is not limited to the lens - 18 arrangement of the illustrated embodiment. Although the LD lens L1 is made of a converging lens which condenses the laser beams in the embodiment shown in Fig. 1, it is possible to make the LD lens L1 a diverging lens. Although the ferrule ring 17 is provided between the adjusting ring 16 and the ferrule holder 18, it is possible to directly insert the ferrule holder 18 in the adjusting ring 16.

As can be understood from the above discussion, of the present invention, the coupling lens is composed of at least two lens elements whose positions are independently adjustable between the light emitter and the optical fiber, and the relative position of the lens elements is adjustable. Consequently, the sensitivity to the position adjustment in each lens element is reduced.

Hence, a precise position adjustment can be carried out.

Moreover, since no or little error caused by the positional deviation are produced, a simple and reliable coupling apparatus for the light emitter and the optical fiber can be provided.

Obvious changes may be made in the specific embodiment of the present invention described herein, such modifications being within the scope of the invention claimed.

- 19

Claims

CLAIMS:-

1. A coupling apparatus for coupling a light emitter and an optical fiber via a coupling lens means, said coupling apparatus comprising:- at least two lenses comprising a first lens for converging or diverging light emitted from the light emitter source and a second lens for converging the light emitted from said first lens onto an end surface of said optical fiber, said coupling lens means comprising said first lens and said second lens; a first member for supporting and connecting said first lens and said light emitter; and a second member for supporting and connecting said second lens and said optical fiber; wherein said first member and said second interconnected so as to be relatively adjustable.

member are

2. A coupling apparatus for a light emitter and an optical fiber according to claim 1, wherein the magnification of said second lens is smaller than 1.

3. A coupling apparatus for a light emitter and an optical fiber according to claim 1 or 2, wherein said first member is comprised of a first lens holder to which the first lens is attached and an LD holder to which a laser diode constituting said light emitter is attached, so that said LD holder is laser-welded to said first lens after the - 20 position of said LD holder is adjusted relative to said first lens holder.

4. A coupling apparatus for a light emitter and an optical fiber according to any preceding claim, wherein said second member is comprised of a second lens holder to which said second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of said optical fiber is attached through said ferrule holder, wherein the adjusting ring is laser-welded to said second lens holder after the position of said adjusting ring is adjusted relative to said second lens holder.

5. A coupling apparatus for a light emitter and an optical fiber according to any preceding claim, wherein said first member is comprised of a first lens holder to which said f irst lens is attached, and an LD holder to which a laser diode constituting said light emitter is attached, so that the LD holder is laser-welded to the first lens after the position of the LD holder relative to the first lens holder is adjusted, and said second member is comprised of a second lens holder to which said second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of said optical fiber is attached through a ferrule holder, so that said adjusting ring is laser-welded to said second lens holder after the position of said adjusting ring is adjusted relative to said second lens holder, said first - 21 and second lens holders being interconnected by screws upon completion of the position adjustment thereof.

6. A method for adjusting the position of a light emitter and an optical fiber in a coupling apparatus, said coupling apparatus comprising:- a coupling lens means; at least two lenses comprising a first lens for converging or diverging light emitted from the light emitter source and a second lens for converging the light emitted from said first lens onto an end surface of the optical fiber, said coupling lens means comprising said first lens and said second lens; a first member for supporting and connecting said first lens and said light emitter; and a second member for supporting and connecting said second lens and said optical fiber; said method comprising: securing said first lens and said light emitter to said first member after the relative position of the first lens and the light emitter is adjusted; securing said second lens and said optical fiber to said second member after the relative Position of the second lens and the optical fiber is adjusted; and securing said first member and said second member after the relative Position of the first member and second member is adjusted.

7. A method for adjusting the position of a light emitter and an optical fiber in a coupling apparatus according to claim 6, wherein the magnification of said second lens is smaller than 1.

8. A method for adjusting the position of a light emitter and an optical fiber in a coupling apparatus according to claim 6 or 7, wherein said first member is comprised of a first lens holder to which the first lens is attached and an LD holder to which a laser diode constituting said light emitter is attached, and wherein said LD holder is laser-welded to said first lens after the position of said LD holder is adjusted relative to said first lens holder.

9. A method for adjusting the position of a light emitter and an optical fiber in a coupling apparatus according to any one of claims 6 to 8, wherein said second member is comprised of a second lens holder to which said second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of said optical fiber is attached through a ferrule holder, and wherein the adjusting ring is laser-welded to said second lens holder after the position of said adjusting ring is adjusted relative to said second lens holder.

10. A method for adjusting the position of a light emitter and an optical fiber in a coupling apparatus - 23 according to any one of claims 6 to 9, wherein said first member is comprised of a first lens holder to which said first lens is attached and an LD holder to which a laser diode as the light emitter is attached, so that said LD holder is laserwelded to said first lens after the position of said LD holder is adjusted relative to the first lens holder, and wherein said second member is comprised of a second lens holder to which said second lens is attached and an adjusting ring to which a ferrule which holds the incidence end of said optical fiber is attached through a ferrule holder, so that said adjusting ring is laser-welded to said second lens holder after the position of the adjusting ring relative to the second lens holder is adjusted, said first and second lens holders being interconnected by screws upon completion of the position adjustment thereof.

11. A coupling apparatus for coupling a light emitter and an optical fiber, the apparatus comprising:- first member for supporting said light emitter and a first lens element; second member for supporting said optical fiber and a second lens element; wherein the first and second members are connected for relative adjustment.

1

12. A coupling apparatus substantially as hereinbefore described with reference to the accompanying drawings.

13. A method for adjusting the position of a light emitter and an optical fiber substantially as hereinbefore described with reference to the accompanying drawings.