JP3928273B2 - Mechanism and method for holding a truncated pyramid light guide - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light guide holding mechanism for making light uniform. More particularly, the present invention relates to a holding mechanism for a pyramid-shaped light guide.
[0002]
[Prior art]
For example, in a projector lighting unit, it is necessary to irradiate light from a light source uniformly onto a DMD (digital micromirror device). In such a case, a prismatic light guide called an integral rod is used. Has been.
[0003]
That is, in general, even if light from a point light source is spot-condensed by a reflector or a condensing lens group, the illuminance distribution of the light is generated in the spot and is not uniform. Therefore, in order to irradiate the irradiated surface with light from the light source with uniform illuminance, a prismatic light guide 1 as shown in FIG. 1 has been used. That is, the light incident from the one end surface 1a of the light guide 1 is uniformly reflected by repeating total reflection in the light guide, and is irradiated from the other end surface 1b.
[0004]
As can be seen from FIG. 1, the end face 1a for introducing light into the light guide preferably has a large area in order to efficiently introduce more light from the light source. From such an idea, a light guide 2 having a truncated pyramid shape in which the area of one end face is increased as shown in FIG. 2 is known.
[0005]
As a method of holding the light guide 2 having a truncated pyramid shape in the optical path, as shown in FIG. 3, the light guide 2 placed on the slope is pressed onto the slope from above (arrow A) and the optical axis direction The deviation of the gap is regulated by a stopper 3 provided on the slope. However, in the fixing method as shown in FIG. 3, when the light guide 2 is thermally expanded, the axis 2 </ b> A of the light guide moves slightly as shown by the arrow B, and the irradiation accuracy of light on the irradiation surface is improved. There is a problem of lowering.
[0006]
[Problems to be solved by the invention]
Therefore, a technical problem to be solved by the present invention is a mechanism for holding a truncated pyramid-shaped light guide, and even if the light guide is thermally expanded, its axis is not moved. It is to provide a holding mechanism and a holding method.
[0007]
[Means / Actions / Effects to Solve Problems]
The present invention was devised in order to effectively solve the above-described problem, and the light guide is thermally deformed with respect to “a truncated pyramid-shaped light guide having a first end surface having a large area and a second end surface having a small area”. Even in this case, the shaft center and the first end face are held so as not to move. The size of the area here is relative, and means that the first end face is relatively larger than the second end face. Therefore, such a light guide necessarily has a cone shape. Moreover, since the light guide has a truncated pyramid shape, the shapes of the first end face and the second end face are naturally polygonal. In addition, it is preferable that the shape of a 1st end surface is a regular polygon.
[0008]
In the present invention, “the second end surface of the light guide whose first end surface is in contact with the surface of the support wall is elastically biased toward the support wall side” and “the light guide is also moved around the optical axis. The light guide is held by elastically urging and rotating the corners of the first end face against the slightly larger frame wall provided on the outer periphery of the first end face. Is done. The present invention provides a light guide holding mechanism having the following features.
[0009]
The light guide holding mechanism of the present invention includes a “pyramidal trapezoidal light guide having a first end surface having a large area and a second end surface having a small area” as “a first end surface support wall for supporting the first end surface” and “the support wall. The second end face support member that is not relatively rotatable and elastically biases the second end face toward the support wall ”is sandwiched. The first end surface support wall is similar to the first end surface and is slightly larger in size than the “abutting surface provided around the opening through which incident light is transmitted to the first end surface and in contact with the first end surface”. Frame wall ". The second end surface support member includes an “opening through which light emitted from the second end surface passes”, and is pressed onto the second end surface in a state where the peripheral edge of the opening is in contact with the peripheral edge of the second end surface. Yes. Further, the second end face support member includes an “intermediate ring having an opening for holding the light guide in conformity with the cross-sectional shape perpendicular to the axis at a predetermined axial position between the first end face and the second end face of the truncated pyramid light guide. "Members" are connected via a coil spring. Then, the intermediate ring member engaged with the light guide rotates the light guide around the optical axis by the biasing force in the circumferential direction of the coil spring to rotationally press the corner portion of the first end surface against the frame wall, thereby Hold.
[0010]
According to the light guide holding mechanism having the above configuration, the thermal expansion in the radial direction and the length direction can be absorbed as follows without displacing the optical axis position of the light guide.
[0011]
(1) The radial thermal expansion light guide has a shape similar to that of the first end surface, and is elastically held by rotationally pressing the corner portion of the first end surface against a slightly large frame wall. . This rotational pressure contact is performed using an intermediate ring member that is biased in the circumferential direction by a coil spring and holds the light guide. Since the cross-sectional shape of the frame wall is similar to that of the first end surface, when the light guide expands and contracts in the radial direction, the contact position of the corner portion of the first end surface on the frame wall changes, so that the light guide It will rotate around the axis. The displacement of the light guide due to this thermal expansion and contraction is only rotation about the optical axis, and the position of the optical axis itself does not change. Further, when the light guide rotates, the intermediate ring member engaged therewith also rotates integrally to absorb the rotation of the light guide. Of course, even after the rotation, the elastic force by the spring acts effectively, and thereby the light guide is rotationally pressed against the frame wall. It is preferable to further provide a guide wall for guiding the intermediate ring member to rotate in a state where the center of the intermediate ring member coincides with the optical axis of the light guide.
[0012]
(2) The thermal expansion light guide in the length direction (optical axis direction) is elastically attached to the support wall side by the second end surface support member in a state where the first end surface is in contact with the support wall surface. Be forced. Therefore, when the light guide expands and contracts in the length direction, the expansion and contraction is absorbed by the movement of the second end surface support member accordingly. Of course, even after expansion and contraction, the elastic force by the second end surface support member acts effectively, and thereby the light guide is held. As a matter of course, the optical axis position of the light guide does not change by expansion and contraction in the length direction.
[0013]
In the present invention, a small hole is provided in each of the second end surface support member and the intermediate ring member, and each bent end portion formed by bending both ends of the coil spring in the optical axis direction is passed through the small hole, whereby the second The end surface support member and the intermediate ring member are preferably connected to a coil spring. In that case, further, the bent end portion of the coil spring passed through the small hole of the second end surface support member is projected through the support member, and the second end surface support member is engaged by the lock member engaged with the projecting end. It is preferable to prohibit relative rotation with respect to the first end face support wall.
[0014]
In the light guide, light travels while repeating total reflection, but in general, part of the light escapes outside at the contact portion between the light guide and its holding member, and transmission efficiency decreases. Accordingly, it is naturally preferable that the contact area between the intermediate ring member engaged with the light guide and the light guide is also small. That is, the intermediate ring member holds the light guide by inserting a truncated pyramid-shaped light guide into the opening, but a notch is provided at the periphery of the opening so that the opening periphery and the light guide It is preferable to reduce the contact area. From the same viewpoint, it is preferable that the peripheral edge of the opening and the light guide are in line contact rather than surface contact.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 4 is a schematic exploded view showing a holding mechanism according to an embodiment of the present invention. FIG. 5 shows a state after the assembly of the holding mechanism is completed.
[0016]
The light guide 2 is the same as that shown in FIG. 2, and has a truncated pyramid shape having a relatively large area first end surface 2a and a small area second end surface 2b. In this example, the first end face 2a is square and the second end face 2b is rectangular. As will be described below, the light guide 2 is held by the holding mechanism of the present invention so that the axial center and the first end face are not displaced even when thermally deformed.
[0017]
The light guide 2 is accommodated in a bottomed outer cylinder 10 that is open at one end. The outer cylinder 10 includes a cylindrical peripheral wall 11 and a bottom wall 12, and a flange 16 is formed on the periphery of the open end. The bottom wall 12 functions as a support wall that supports the first end surface 2a of the light guide. As can be seen from FIG. 4, the support wall 12 has a square recess 13 at the center, and further has a circular opening 14 inside thereof.
[0018]
After the assembly of the holding mechanism, as shown in FIG. 5, the disk-shaped support plate 40 presses the second end surface 2b of the light guide 2 toward the support wall 12 side. That is, the light guide 2 is elastically sandwiched between the support wall 12 and the support plate 40. The support plate 40 includes a rectangular opening 41 that is slightly smaller than the second end face 2b of the light guide, and is pressed by a leaf spring 50 with the peripheral edge of the opening 41 in contact with the second end face 2b. Has been. In FIG. 5, the central portion of the second end face 2 b can be seen in the opening 41 of the support plate 40.
[0019]
The elastic force that presses the support plate 40 onto the second end surface 2b is given by the leaf spring 50. The leaf spring 50 is fixed to the flange 16 of the outer cylinder 10 using a screw (not shown) or the like, and includes four locking pieces 51 protruding inward. The four locking pieces 51 abut against the peripheral edge of the support plate 40, thereby pressing the support plate 40 onto the second end surface 2b of the light guide. The leaf spring 50 is a C-shaped member obtained by cutting a part of a ring-shaped member in order to escape a lock member 60 described later (see FIG. 5).
[0020]
The light guide 2 is held with its first end face 2 a engaged in the recess 13 on the support wall 12. The concave portion 13 is constituted by a square frame wall 13a which is similar in shape and slightly larger to the first end surface 2a of the light guide. The opening 12 formed inside the frame wall 13a is provided for passing incident light to the first end surface 2a of the light guide, and is dimensioned so that the first end surface 2a cannot pass therethrough. . Since the frame wall 13a is square and the opening 14 inside thereof is circular, there are four contact surfaces 15 between the frame wall 13a and the opening 14. Therefore, when the first end surface 2a of the light guide is fitted into the recess 13 and the light guide 2 is pressed toward the support wall 12 side, the four corners of the first end surface 2a are in pressure contact with the contact surface 15. This pressure contact is performed by the support plate 40 as described above.
[0021]
When the light guide 2 thermally expands and expands and contracts in the axial direction, the four locking pieces 51 are elastically deformed to move the support plate 40 in the axial direction. As a result, the expansion and contraction of the light guide 2 is absorbed. . At this time, the position of the first end surface 2a that is in contact with the four contact surfaces 15 formed between the frame wall 13a and the opening 14 does not change. The displacement of the light guide 2 is absorbed by the displacement of the second end face 2b. As a matter of course, the optical axis position of the light guide 2 does not change by expansion and contraction in the length direction.
[0022]
So far, the mechanism in which the holding mechanism of the present invention holds the light guide 2 in the optical axis direction has been described. Next, a mechanism for holding the light guide 2 in the radial direction will be described.
[0023]
The intermediate ring 20 is connected to the support plate 40 via a coil spring 30. Small holes 21 and 42 are formed in the intermediate ring 20 and the support plate 40, respectively. The coil spring 30 is connected to the intermediate ring 20 and the support plate 40 by inserting the bent end portions 31 and 32 formed by bending both ends in the optical axis direction through the small holes 21 and 42, respectively. Yes. As will be described later, the support plate 40 is fixed to the outer cylinder 10 so as not to rotate relative to the outer cylinder 10 after the assembly of the holding mechanism, and thus is connected to the support plate 40 via the coil spring 30. The intermediate ring 20 urges the light guide 2 to rotate around its optical axis.
[0024]
FIG. 6 is an enlarged plan view showing the intermediate ring 20. The opening 23 is provided to hold the light guide 2 so as not to rotate relative to the intermediate ring 20 itself. That is, the opening 23 is configured by providing circular notches 23a at the four corners of the rectangular basic shape 23 'shown by the broken line in FIG.
[0025]
The reason why the basic shape 23 ′ is rectangular is to hold the light guide 2 in a relatively non-rotatable manner. That is, the truncated pyramid-shaped light guide 2 in which the first end face 2a is square and the second end face 2b is rectangular has a rectangular shape perpendicular to the axis at a predetermined position in the axial direction between both end faces 2a and 2b. The shape is basically a rectangular shape that fits (fits) the rectangular shape, thereby holding the light guide 2 so as not to rotate relative to the intermediate ring 20.
[0026]
The reason why the notch 23a is added to the basic shape 23 'is that the contact area between the intermediate ring 20 and the light guide 2 is made as small as possible without preventing the light guide 2 from being held in a relatively non-rotatable manner. It is to do. That is, light travels while repeating total reflection in the light guide 2, but part of the light escapes outside at the contact portion between the light guide 2 and the intermediate ring 20, and transmission efficiency decreases. The notch 23a is provided to avoid this.
[0027]
Accordingly, it is preferable to provide as many cutouts as possible within the range in which the light guide 2 can be held in a relatively unrotatable manner by the opening 23, as well as the cutouts 23a shown in FIG. On the other hand, FIG. 7 is an axial sectional view showing the contact portion between the light guide 2 and the intermediate ring 20 in an enlarged manner. From the same viewpoint as described above, the peripheral edge of the opening 23 of the intermediate ring 20 and the light guide 2 are It is preferable to make line contact instead of surface contact. In FIG. 7, the intermediate ring 20 is drawn thicker than it actually is to make it easier to understand the state of line contact.
[0028]
As already described, the frame wall 13a constituting the recess 13 is similar in shape to the first end surface 2a and is a slightly large square. In other words, the first end face 2a of the light guide is fitted in the recess 13 with a slight backlash, and can be slightly rotated (rotated) about its own optical axis. On the other hand, since the entire light guide 2 is rotationally biased by the intermediate ring 20, the first end surface 2a rotates in the recess 13 and presses the corners 2a 'of the four corners against the surface of the frame wall 13a. It becomes. 8 and 9 are schematic views for explaining this, and is a view of the support wall 12 seen from the arrow B direction in FIG. Therefore, the direction of arrow A in FIG. 4 and the direction of arrow A in FIGS. 8 and 9, the opening 14 is not shown. FIG. 8 shows a state before the first end face 2a of the light guide 2 is pressed against the frame wall 13a, and FIG. 9 shows a state after the pressure contact.
[0029]
4 and 5, the direction in which the intermediate ring 20 urges the light guide 2 to rotate is the direction of arrow A. This will be described below. When actually assembling the holding mechanism, the intermediate ring 20 and the support plate 40 connected by the coil spring 30 are fitted into the peripheral wall 11 of the outer cylinder 10. At this time, the light guide 2 is inserted into the opening 23 provided in the intermediate ring 20, and the first end face 2 a is fitted into the recess 13. Since the support plate 40 is fitted into the peripheral wall 11 while being urged to rotate in the direction of arrow A in FIG. 4, as a result, the light guide 2 is also urged to rotate in the direction of arrow A by the intermediate ring 20.
[0030]
The support plate 40 is held at the predetermined position by the lock member 60 while being rotated to a predetermined position in the arrow A direction. The lock member 60 is a wedge-shaped member that protrudes from the flange 16 toward the inner diameter side, and engages with the bent end portion 32 of the coil spring 30 that protrudes through the support plate 40, thereby fixing the support plate 40 to a predetermined position. Hold in position. The bent end 32 is pressed against the tip 61 of the lock member 60 by the restoring force of the coil spring 30. As a result, the support plate 40 rotates relative to the outer cylinder 10 including the first end support wall 12. It will be fixed impossible. That is, the support plate 40 can rotate relative to the support wall 12 during the assembly process of the holding mechanism, but cannot rotate relative to the support wall 12 after the assembly is completed.
[0031]
The fixing position of the support plate 40 by the lock member 60 is set so that the positions of the opening 41 of the support plate and the second end surface 2b of the light guide are substantially aligned. That is, in the illustrated example, both the opening 41 and the second end surface 2b are rectangular, and the second end surface 2b is slightly larger. And in the fixed position of the support plate 40 shown in FIG. 5, the support plate 40 is press-contacted on the 2nd end surface 2b in the state which all the peripheral parts of the opening 41 contact | abutted to the peripheral part of the 2nd end surface 2b. Yes. As a result, light emitted from the second end surface 2b exits from the second end surface 2b in a shape defined by the opening 41. In other words, the opening 41 functions as a mask for the second end face 2b of the light guide.
[0032]
When the locking member 60 is engaged with the bent end portion 32 of the coil spring 30, the opening 41 of the support plate 40 and the second end surface 2b of the light guide 2 are substantially aligned with a screw or the like. Fixed. The fixing position of the support plate 40 can be finely adjusted by adjusting the protruding direction of the wedge-shaped tip portion 61. In the illustrated example, one end 32 of the coil spring 30 is protruded from the support plate 40 and is fixed by the lock member 60 using this to reduce the number of parts and reduce the cost. Alternatively, the protrusions may be integrally formed on the support plate 40 and may be fixed by the lock member 60 using this.
[0033]
FIG. 9 shows a state in which the first end face 2 a of the light guide 2 is rotationally pressed against the frame wall 13 a by the intermediate ring 20. That is, when the light guide 2 rotates relative to the support wall 12 in the direction of the arrow A, the four corners 2a ′ of the first end face 2a of the light guide are pressed against the surface of the frame wall 13a. The light guide 2 is prevented from shifting in the radial direction (a direction perpendicular to the optical axis direction).
[0034]
As already described, the frame wall 13a has a shape similar to that of the first end face 2a and is slightly larger, so that the optical axis of the light guide 2 and the center of the frame wall 13a Will match exactly. When the light guide 2 expands and contracts in the radial direction due to thermal expansion, the length of one side of the first end face 2a of the light guide also expands and contracts, so that the light guide 2 is centered on the optical axis while maintaining pressure contact with the frame wall 13a. Will rotate as. During such rotation, the optical axis position of the light guide 2 and the center position of the frame wall 13a do not deviate. That is, the expansion and contraction in the radial direction is absorbed without the optical axis position of the light guide 2 being displaced. Of course, even after expansion and contraction, the elastic force by the coil spring 30 acts effectively, thereby holding the light guide.
[0035]
As can be seen from the above description, when the frame wall 13a is too large with respect to the first end surface 2a, the first end surface 2a idles inside the frame wall 13a, and the above-described effect of pressure contact is obtained. Can not be. That is, in the present invention, “the frame wall 13a is slightly larger than the first end surface 2a” means that the dimensional difference between the frame wall and the first end surface is close enough not to cause the idle rotation. means. Further, when the first end surface 2a rotates (spins) while maintaining pressure contact with the frame wall 13a, the optical axis position of the light guide 2 and the center position of the frame wall 13a are kept in agreement with each other. In order to prevent deviation, it is necessary that the shape of the first end surface 2a and the shape of the frame wall 13a are similar. The first end surface 2a (and therefore the frame wall 13a) may be rectangular, for example, but is preferably a regular polygon.
[0036]
Since the intermediate ring 20 is connected to the support plate 40 via the coil spring 30, not only the rotation biasing force but also the action of pressing the light guide 2 toward the support wall 12 in the direction of the optical axis is natural. Have. However, it is the support plate 40 fixed to the flange 16 via the leaf spring 50 that absorbs the expansion and contraction of the light guide 2 in the optical axis direction. Note that when the light guide 2 expands and contracts in the optical axis direction, the distance between the support plate 40 and the intermediate ring 20 changes. This change in distance is absorbed by the coil spring 30.
[0037]
When the intermediate ring 20 rotates (spins) by the urging force of the coil spring 30, the peripheral wall 11 of the outer cylinder 10 rotates while keeping the center of the intermediate ring 20 aligned with the optical axis of the light guide 2. It has the effect | action which guides. However, the intermediate ring 20 itself has a function of pressing the light guide 2 toward the support wall 12, and the light guide 2 itself has a radial direction as its first end surface 2 a presses against the frame wall 13 a. Therefore, even if the peripheral wall 11 is not necessarily provided, the intermediate ring 20 has a property of attempting to rotate in a state where the center thereof coincides with the optical axis of the light guide 2. However, the provision of the peripheral wall 11 can more reliably prevent the center of the intermediate ring 20 and the optical axis of the light guide 2 from shifting. In this sense, the peripheral wall 11 is not necessarily provided so as to surround the entire circumference of the light guide 2. For example, the intermediate ring 20 is guided by a plurality of bar members provided at predetermined intervals in the circumferential direction. Also good.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a prismatic light guide.
FIG. 2 is a perspective view showing a light guide having a truncated pyramid shape.
FIG. 3 is a schematic diagram illustrating a conventional mechanism for holding the light guide of FIG. 2;
FIG. 4 is an exploded perspective view illustrating a light guide holding mechanism according to an embodiment of the present invention.
5 is a perspective view showing an assembled state of the holding mechanism of FIG. 4; FIG.
6 is a front view of an intermediate ring used in the holding mechanism of FIG. 4. FIG.
7 is an axial cross-sectional view showing an enlarged contact portion between the light guide and the intermediate ring in the assembled state of FIG. 5;
FIG. 8 is a schematic explanatory view showing a state before the first end face of the light guide is pressed against the frame wall.
FIG. 9 is a schematic explanatory view showing a state where the first end face of the light guide is pressed against the frame wall.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 prismatic light guide 1a, 1b end surface 2 pyramid-shaped light guide 2a 1st end surface 2a 'of large area 1b corner 2b of 1st end surface 2nd end surface 3 of small area Stopper
10 outer cylinder
11 perimeter wall
12 Support wall (bottom wall)
13 recess
13a frame wall
14 opening
15 Contact surface
16 Flange
20 Intermediate ring
21 small hole
23 opening
23 'basic shape of opening
23a Notch
30 Coil spring
31, 32 Bent edge
40 Support plate
41 opening
42 small holes
50 leaf spring
51 Locking piece
60 Locking member
61 Tip

Claims (8)

A truncated pyramid light guide having a first end face with a large area and a second end face with a small area, a first end face support wall that supports the first end face, and a second end face that is not rotatable relative to the support wall. A light guide holding mechanism sandwiched between a second end surface support member elastically biased toward the wall side,
The first end surface support wall is provided in the vicinity of an opening through which incident light is transmitted to the first end surface and is in contact with the first end surface, and is provided on the outer peripheral side of the first end surface support wall and is similar to the first end surface and has a slightly larger frame. With walls,
The second end surface support member includes an opening through which light emitted from the second end surface passes, and is pressed against the second end surface in a state where the peripheral edge of the opening is in contact with the peripheral edge of the second end surface, The support member includes an intermediate ring member having an opening for holding the light guide in conformity with a cross-sectional shape perpendicular to the axis at a predetermined position in the axial direction between the first end surface and the second end surface of the truncated pyramid light guide. Are connected via
The holding is characterized in that the intermediate ring member engaged with the light guide rotates the light guide around the optical axis by the biasing force in the circumferential direction of the coil spring so that the corner portion of the first end face is in rotational pressure contact with the frame wall. mechanism. The holding mechanism according to claim 1, wherein the shape of the first end face is a regular polygon. A small hole is provided in each of the second end surface support member and the intermediate ring member, and the second end surface is formed by passing each bent end portion formed by bending both ends of the coil spring in the optical axis direction through the small hole. 3. The holding mechanism according to claim 1, wherein the support member and the intermediate ring member are connected to a coil spring. A bent end portion of the coil spring passed through the small hole of the second end surface support member protrudes through the support member, and the second end surface support member is 4. The holding mechanism according to claim 3, wherein relative rotation with respect to the one end face support wall is prohibited. 5. The holding according to claim 1, further comprising a guide wall for guiding the intermediate ring member to rotate in a state where the center of the intermediate ring member coincides with the optical axis of the light guide. mechanism. The holding mechanism according to claim 1, 2, 3, 4, or 5, wherein a notch is provided in an opening periphery of the intermediate ring member to reduce a contact area between the opening periphery and the light guide. The holding mechanism according to claim 1, 2, 3, 4, 5 or 6, wherein the opening peripheral edge of the intermediate ring member and the light guide are in contact with each other by line contact. A method of holding a truncated pyramid light guide having a first end face with a large area and a second end face with a small area so that the axial center and the first end face do not move even when the light guide is thermally deformed,
While elastically urging the second end surface of the light guide with the first end surface in contact with the support wall surface toward the support wall side,
The light guide is also elastically rotated around the optical axis, and the corner portion of the first end face is rotationally pressed against a frame wall similar to the first end face, which is provided on the outer peripheral side thereof. ,
A light guide holding method.

Images