JPH073553B2 - Light source unit - Google Patents

Description

The present invention relates to a light source unit, and is particularly suitable for use as a light source for office equipment such as an image scanner, an optical printer, a monochrome copying machine, a color copying machine, and a facsimile machine. A light source unit.

[Conventional technology]

As a light source for office equipment such as image scanners, optical printers, monochrome copiers, color copiers, facsimile machines, etc., in order to improve the resolution and reading speed, the light intensity level is large, and the light intensity level is uniform and uniform. It is desirable that the irradiation light be a linear light and an irradiation light close to a parallel light ray having a small light distribution beam angle (hereinafter, referred to as a high bright line light).

As a light source for high-brightness linear light that meets such requirements, the present applicant has previously proposed, as Japanese Patent Application No. 60-284115, a light source unit using an optical transmission rod covered by a cylindrical mirror with a slit. ing. This light source unit is provided with a base that is attached to a body to be attached, a reflection mirror that is supported by the base, has a reflecting surface axially inward on one end surface, and has a high refractive index fine powder on the outer peripheral surface. An optical transmission rod provided with a diffusion fringe formed by attaching a body in a linear fine stripe shape in the axial direction, and a position facing the diffusion fringe formed on the optical transmission rod while covering the optical transmission rod. A cylindrical mirror with a slit having a slit, and a lamp which is provided on the other end surface of the optical transmission rod and which allows light to enter the other end surface.

In the above configuration, when the lamp is turned on, the light emitted from the lamp is incident on the end face of the optical transmission rod while being condensed. The incident light is irradiated with only the primary beam light from the slit due to the diffusion fringes. As a result, it is possible to obtain uniform linear light that is close to parallel rays and has no unevenness in light amount, that is, high-brightness linear light. Also, the secondary beam light is
The light is reflected by the fringes in the optical transmission rod by the cylindrical mirror with slits and is used again as the primary beam light.

[Problems to be solved by the invention]

However, according to the light source unit disclosed in the above-mentioned Japanese Patent Application No. 60-284115, since the cylindrical mirror with slit simply covers the optical transmission rod on a concentric circle, the secondary beam light is efficiently diffused. When the curvature of the reflecting surface is selected to be the optimum curvature for reflecting the stripes, there is a drawback in that the slitted cylindrical mirror becomes large and the light source unit as a whole becomes large in size.

[Means for solving problems]

The present invention has been made in view of the above, and efficiently reflects the secondary beam light to the diffusion fringes and effectively uses it as the primary beam light, and further reduces the size of the entire light source unit. Provided is a light source unit having a reflecting mirror with a slit formed only on an anti-slope of light to have an optimum curvature.

That is, this light source unit is formed on the optical transmission rod, which has an optical transmission rod provided on the outer peripheral surface thereof with diffusion fringes formed by adhering fine powder having a high refractive index in the form of linear fine stripes in the axial direction. There is a slit at a position facing the diffusion fringes, and the slit portion facing the diffusion fringes is at a position most adjacent to the light transmission rod, and also from the light transmission rod as it goes away from the slit. In addition to having a reflective surface that is formed with an optimal curvature that is spaced apart,
A reflection mirror with a slit formed so as to be provided in the vicinity of the optical transmission rod except for the reflection surface, and a light source for injecting light into at least one end surface of the optical transmission rod. Is.

〔Example〕

Hereinafter, a light source unit according to the present invention will be described in detail with reference to the drawings.

FIGS. 1 (a), (b) and (c) show an embodiment of a light source unit according to the present invention, which is attached to an attached body such as a scanner by any fixing means such as screws and bolts, and will be described later. Holes for fitting and fixing the legs 14L, 14R of the supports 12L, 12R and the legs 18 of the reflecting mirror 16 with slits.
A base 10 having 20 and a groove 22 (the leg portion 14R is fitted and fixed to the groove 22) and a columnar optical transmission rod 26 are closely inserted into and supported by the through hole 28, and A pair of left and right supports 12L, 12R having legs 14L, 14R and protrusions 30L, 30R engaged and fixed to the base 10 and the reflecting mirror 16 with slits, and a base
Protrusions 3 of legs 18 and supports 12L, 12R that engage holes 20 of 10
It has a notch 32 that engages with 0L and 30R, and has a slit-shaped reflecting mirror 16 having a slit 34 at the top and a mirror-like substantially inverted U-shape. Diffuse fringes 36 are formed on the outer peripheral surface of a cylindrical optical transmission rod 26 that transmits the light incident from one end toward the other end by applying fine powder having a high refractive index in the form of linear fine stripes in the axial direction. In addition, a reflecting mirror having an anti-slope on the inner surface of the optical transmission rod 26 is provided on one end surface. Note that the diffusion fringes 36 are located on the surface opposite to the slits 34 in the assembled state, and the leg portions 18 penetratingly engaged with the holes 20 are fixed by being bent at the bottom surface of the base 10. It
A reflection surface for returning scattered light other than the effective incident light to the light transmission rod 26 to the lamp reflection mirror 42 of the lamp 40 again is provided on the end surface of the light transmission rod 26 opposite to the end surface having the reflection mirror. A reflector 44 having is attached. A lamp such as a halogen bulb, a xenon lamp, or a flash lamp can be used as the lamp 40. In this embodiment, a halogen bulb with a reflector is used as the lamp 40 and the reflector 42.

While the light from the lamp 40 is being condensed, the light incident on the inside of the end face of the optical transmission rod 26 that does not have a reflecting mirror is:
The transmitted light that has been transmitted in the axial direction while repeating total reflection in the optical transmission rod 26 and reaches the reflecting mirror is reflected by this reflecting mirror. On the outer peripheral surface of the optical transmission rod 26, since the diffusion fringes 36 made of fine powder having a high refractive index are formed along the axial direction, the transmitted light transmitted through the optical transmission rod 26 and reflected by the reflecting mirror are reflected. The reflected light thus reflected is diffused and reflected in the optical transmission rod 26 by the diffusion stripes 36, and further, the optical transmission rod 26.
Due to the lens action of, the light is emitted with directivity in the direction opposite to the diffusion stripe 36. FIG. 2 is an explanatory view of the principle of the lens action of the optical transmission rod 26, and the diffusion fringes 36 are the optical transmission rods.
26 It will act as an arc-shaped diffusive reflector closely attached to the outer peripheral surface.

Therefore, in the diffused light diffusely reflected by the reflecting mirror action of the diffuser fringes 36, due to the directional characteristics associated with the circular arc shape of the diffuser fringes 36, the light is once focused on the central axis 46 of the optical transmission rod 26 and then emitted. Of the component and other diffused light that does not focus on the central axis 46, of the ones emitted by converging in the opposite direction to the diffusion fringes 36 by reducing the angle by the lens action of the optical transmission rod 26, the central axis 46 is emitted. The component that is once focused and then emitted and the component in the overlapping range are combined and combined to form the primary beam light A having a large light amount level. Then, the secondary light beam B having a small light quantity level is constituted by the diffused light component other than the component constituting the primary light beam A. In addition, the incident light that is not emitted from the optical transmission rod 26 repeats total reflection inside the optical transmission rod 26, and diffused fringes again.
The light is diffused and reflected by 36 and is emitted to the outside of the optical transmission rod 26. In this way, the transmitted light and the reflected light in the optical transmission rod 26 are sequentially diffused by the diffusion stripes 36 during the transmission and the reflection.
As a result, along with this, the light is emitted with directivity in the direction opposite to the side on which the diffusion fringes 36 are coated, so that it is possible to obtain linear light with no unevenness in the amount of light. Further, since the lens action of the optical transmission rod 26 differs depending on the wavelength of light, the visible light component has a strong directivity, and the components from the near infrared to the infrared have a weak directivity and are diffused, so that harmful heat ray radiation is avoided. be able to.

The primary beam light A, which has a strong light quantity level and a uniform light quantity distribution, is useful as a high-brightness linear light source. The secondary beam light B is transmitted through the optical transmission rod as it approaches the critical angle.
When the light is emitted from 26 to the surrounding medium, the interface reflection component inside the optical transmission rod 26 increases and the light amount level decreases, and the emission angle also tends to widen except near the critical angle. Therefore, by returning the secondary beam light B to the diffusion fringes 36 and converting the secondary beam light B into the primary beam light A, the light amount of the primary beam light A can be increased. Therefore, the reflecting mirror 16 with slits is determined to have a curvature such that the light emitted from the optical transmission rod 26 returns to the same optical path and returns to the diffusion fringes 36. However, at that time,
As shown in FIG. 3, as the outgoing light is separated from the central axis 46 of the rod for optical transmission, the angle α at which the reflected light is re-incident on the rod becomes larger (α ₂ > α ₁ ), and the rod for optical transmission is increased. 26 Reflection loss on the surface increases. Therefore, the effect in the region where α is large is relatively reduced. From this, the curvature of the reflecting mirror with slit 16 in the vicinity of the primary beam light A becomes important and is determined as follows. That is, regarding the outgoing light characteristic of the optical transmission rod 26, the coordinate system is set as shown in FIG. 4 in the optical transmission rod cross-sectional view, and considering the first quadrant, it is emitted from the diffusion stripe (36) point Q and from an arbitrary point P. When the relational expression is obtained for the luminous flux emitted into the surrounding medium n ₂ of the rod 26, Y = tan (α−i ₂ ) X + {Y _P −tan (α−i ₂ ) · X _P } ...
(1) where, X _P = Rcosα, a Y _P = Rsinα. Regarding the fourth quadrant, the first quadrant and x
Be symmetrical about the axis.

If the apparent focal point where the extension line of the outgoing optical axis intersects the X axis is F (X _F , O) as shown in FIG. According to Shnell's law, n ₁ · sini ₁ = n ₂ · sini ₂ , so i ₂ = 90 °
iic When i ₂ <90 °, i ₂ is Further, R _M = | X _F | + R + δ (5) α = 2i ₁ (6) The emitted light is limited to the range of i ₁ <iic or α <2iic.

From the equations (2), (4), (5) and (6), when arranging R _M with respect to α, Then, the desired radius of curvature R _M of the cylindrical mirror is calculated.

For example, n ₁ = 1.46 (refractive index of quartz rod) n ₂ = 1.0 (refractive index of medium [air] in contact with the rod) Therefore, the range of α <± 86.46 ° contributes as outgoing light.

Regarding δ = 1 (mm) 1) R = 3 (mm) 2) R = 5 (mm) 3) R = 7.5 (mm) The calculation results for each case are shown in Appendix 1. From the calculation results, it can be seen that it is practical that the curvature value of the reflecting mirror does not change so much and that it is represented by an average value in the range of α ≦ 50 °.

Further, when n ₁ = 1.49 (refractive index of acrylic resin rod), it contributes as outgoing light in the range of α <± 84.3 °.

Regarding δ = 1 (mm) 4) R = 3 (mm) 5) R = 5 (mm) 6) R = 7.5 (mm) The calculation results for each case are shown in Appendix 2. From these facts, the emitted light in the range of 0 ≦ α ≦ 20 ° almost overlaps with the primary beam light, and passes through the slit 34 of the reflecting mirror 16 as it is to be emitted to the outside.
The value of the curvature R _M may be considered mainly in the range of ± 20 ° <α <± 50 °.

Therefore, the shape of the reflecting mirror 16 that is suitable for effectively returning the light flux that does not pass through the slit 34 of the reflecting mirror 16 to the diffusion fringes 36 and re-reflecting it is approximately represented by the following radius of curvature when the air gap δ is 1 mm. Can be made.

1) Quartz rod R _M = 12.5 (mm) (R = 3 mm) R _M = 20 (mm) (R = 5 mm) R _M = 30 (mm) (R = 7.5 mm) 2) Acrylic resin rod R _M = 13 (mm) (R = 3 mm) R _M = 21 (mm) (R = 5 mm) R _M = 32 (mm) (R = 7.5 mm) Also, in the rod cross-sectional view of FIG. The outgoing angle of the outgoing light with respect to is the critical angle Since it is limited to a certain range determined by
Is required to have an optimum curvature only in the portion facing the emitted light. As shown in FIG. 4, the reflecting surface of the slit reflecting mirror 16 is such that the portion of the slit 34 facing the diffusion stripe 36 is the rod 26.
Is formed on the reflecting surface having the optimum curvature that is the closest to the slit 34, and is separated from the rod 26 as it is separated from the slit 34. Since any curvature other than the reflecting surface may be used, the reflecting mirror with slit 16 is miniaturized by being provided in the vicinity of the rod 26.

According to an experiment by the applicant, fused silica is used as the material of the optical transmission rod 16, the rod diameter is 10 mm, and the diffusion stripe is
When the stripe width of 36 is 3 mm, there is the following relationship between the width of the slit 34 and the stripe width, and the results of Appendix 3 are obtained.

However, as an experimental method, according to the method shown in Fig. 5, a quartz fiber for multi-mode optical communication (core diameter 50μ, cladding diameter 125μ, acceptance angle 2θ = 20 °) was used to measure the light level. The scan was performed in the direction perpendicular to the axis center. The measurement distance was 5 mm from the outer surface of the cylindrical mirror.

From the experimental results, the distribution characteristic diagram of the amount of light emitted from the slit 34 is shown in FIG. 6. Therefore, the relationship between the width of the slit 34 and the stripe width is (3) in actual use. In terms of characteristics and stability, it is preferable to narrow the slit width a little as in (2) in order to obtain a sharp directional characteristic and a maximum light amount level.

The 90% outgoing light quantity distribution width is x in FIG. 7, and indicates the outgoing width at a light quantity level of 90% or more.

In the above configuration, when the lamp 40 is turned on, the lamp 40
The light radiated by is directly or via the lamp reflecting mirror 42 and the reflector 44 incident on the end face of the optical transmission rod 26 while being condensed. Only the primary beam light A is emitted from the slit 34 due to the diffused fringes 36 of the incident light, and it is possible to obtain a uniform linear light which is close to a parallel light beam and has no light amount unevenness.

The secondary beam light B is reflected by the reflecting mirror with slit 16 to the diffusion fringes 36 in the optical transmission rod 26, and is used again as the primary beam light.

8 (a), (b) and (c) show another embodiment of the reflecting mirror with slits, which are designated by reference numerals 216, 316 and 416. In short, only the portion (reflecting surface) where the emitted light is reflected has a shape having an optimum curvature, that is, the vicinity of the slit 34 is closest to the optical transmission rod 26, and the light transmission rod is separated from the slit 34. Any shape other than the reflecting surface can be selected as appropriate as long as the shape is separated from 26.

Further, FIG. 9 shows that the slit reflecting mirror 116 and the base 100 are integrally molded, and in this case, the production can be efficiently performed.

Furthermore, as shown in FIG. 10, instead of the reflecting mirror provided on the one end surface of the optical transmission rod 4, a lamp that makes light incident on the one end surface may be provided (that is, the optical transmission rod 4). Of course, the lamps are arranged at both ends of this, and in this case, a more effective light amount distribution can be obtained in the axial direction.

〔The invention's effect〕

As described above, according to the light source unit of the present invention,
An optical transmission rod provided with diffusion fringes formed by attaching fine powder having a high refractive index to the outer peripheral surface in the form of linear fine stripes in the axial direction, and facing the diffusion fringes formed on the optical transmission rod. While having a slit at a position, the slit portion facing the diffusion fringe is at a position most adjacent to the optical transmission rod, and has an optimum curvature so as to be separated from the optical transmission rod as it goes away from the slit. Since a reflecting surface with a slit having an anti-slope formed in a curvature and a light source for injecting light into at least one end surface of the optical transmission rod are provided, the secondary beam light is efficiently reflected to the diffusion fringes. As a result, the light source unit can be effectively used as the primary light beam and the entire light source unit can be downsized, so that the mountability to the device can be significantly improved.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, (a) is an exploded perspective view of a main part, (b) is a front view of a unitized state, (c) is a sectional view taken along the line CC, and FIG. 2 is FIG. 3 is an explanatory view showing the principle of the lens action of the optical transmission rod, FIG. 3 is an explanatory view showing the relationship between the emitted light and the curvature of the reflecting mirror, and FIG. 4 is for obtaining a relational expression for a desired radius of curvature of the cylindrical mirror. Explanatory diagram, FIG. 5 is an explanatory diagram showing a light amount level measuring method in an experiment showing the relationship between the stripe width of diffusion stripes and the width of the slit, and FIG. 6 is an explanatory diagram showing distribution characteristics of the amount of light emitted from the slit, FIG. 7 is an explanatory view showing the 90% outgoing light quantity distribution width, and FIGS. 8 (a), 8 (b) and 8 (c).
Is a sectional view showing another embodiment of the reflecting mirror with slit, FIG. 9 is a sectional view showing the slit reflecting mirror and the base integrally formed, and FIG. 10 is shown at both ends of the optical transmission rod. The front view of the united state showing the example in which the lamp is arranged. Explanation of symbols 10 …… Base, 12L, 12R …… Support 14L, 14R …… Leg, 16 …… Reflector with slit 18 …… Leg, 20 …… Hole 22 …… Groove, 26 …… Optical transmission Rod 28 …… Through hole, 30L, 30R …… Projection 32 …… Notch, 34 …… Slit 40 …… Lamp, 42 …… Lamp reflector, 44 …… Reflector 116,216,316,416 …… Slit reflector n ₁ ...... Transmission rod refractive index n ₂ ...... Rod surrounding medium refractive index δ …… Air gap between rod and cylindrical mirror R …… Transmission rod radius _RM …… Desired cylindrical mirror curvature radius Q …… Diffusion fringe Position, F ... Apparent focus of emitted light

Claims (1)

[Claims] 1. A cylindrical optical transmission rod having an outer peripheral surface provided with diffusion fringes formed by adhering fine powder having a high refractive index in the form of linear fine stripes in the axial direction, and an outer periphery of the optical transmission rod. There is a slit at a position facing the diffusion fringes formed on the surface, and the slit facing the diffusion fringes is at a position closest to the light transmission rod, and faces the light transmission rod. The surface has a curvature along the outer peripheral surface of the optical transmission rod, has a curvature that separates from the optical transmission rod as it goes away from the slit, and is diffusely reflected by the diffusion fringes. Among the diffused emitted light, the secondary beam light, which is a component other than the primary beam light component that is once focused on the central axis of the optical transmission rod and then emitted, returns to the same optical path again to the diffusion fringes. Formed with a curvature that returns And a surface of the curved surface facing the rod for optical transmission, which has a mirror-like reflecting surface, is provided with a slit-reflecting mirror, and a light source for making light incident on at least one end surface of the rod for optical transmission. A light source unit having.