JPH04328538A - Lighting device - Google Patents

Abstract

PURPOSE:To improve the light quantity distribution and the utilization efficiency of light by returning light which is emitted by the light source and reflected by a submirror to the, light source and setting the focus of a main mirror and the light source at different positions. CONSTITUTION:When an elliptic mirror as a main mirror 11 and an annular spherical mirror as a submirror 13 are used, the center light emission part 12c of the light source 12 is positioned in the spherical center Or of the submirror 13. The main mirror 11 has a 1st focus f1 and a 2nd focus f2 and the 1st focus f1 and the center light emission part 12c of the light source 12 are offset in the direction of the optical axis O of lighting without being aligned with each other. The offset quantity (a) and its direction are set by simulation corresponding to elements such as the shape of the main mirror 11 and the size of the light source 12. Namely, the light which is emitted by the light source light emission part 12c and reflected by the submirror 13 returns to the light source light emission part 12c, so the light reflected by the submirror 13 can be returned to the main mirror 11 without increasing the size of the light source 12 substantially. The focus f1 of the main mirror 11 is offset from the light source light emission part (spherical center of submirror) 12c, so an illuminance distribution which is free from center absence is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination device having a secondary mirror in addition to a primary mirror that reflects light from a light source toward an irradiated area.

0002

[Prior art and its problems] The present applicant has filed a patent application
No. 116379, No. 2-116380, No. 2-236
No. 418, etc., proposed a lighting device having a secondary mirror in addition to a primary mirror. These lighting devices basically align a light source with the focal point of a primary mirror consisting of an elliptical or parabolic mirror, and then provide a secondary mirror that reflects the light from the light source back toward the primary mirror. . As the secondary mirror, a spherical mirror, a spherical Fresnel mirror, a micro-Dach mirror, etc. can be used, and the focal point (spherical center) of this secondary mirror also coincides with the light source. According to these lighting devices, it is theoretically possible to use wasted light that has been irradiated on the outside of the primary mirror to illuminate the area to be illuminated, and it is possible to improve the efficiency of light use.

However, when examining the actual illuminance distribution of this lighting device, it was found that the amount of light at the center was still insufficient. This is because an actual light source lamp is not a point light source but has a fixed size, and near the optical axis, the light reflected from the primary and secondary mirrors is vignetted by the light source itself, so there is a so-called hollow state. This is thought to be because it occurs.

0004

OBJECTS OF THE INVENTION An object of the present invention is to provide a lighting device that uses a secondary mirror in addition to a primary mirror, which can improve the light amount distribution and has high light utilization efficiency.

[0005]

SUMMARY OF THE INVENTION The present invention provides a relationship between a light source and a secondary mirror, in which light emitted from the light source's light emitting section and reflected by the secondary mirror returns to the light source's light emitting section; This device was completed after discovering that the light amount distribution and light utilization efficiency can be improved by arranging the focal point and the position of the light emitting part of the light source so that they do not match.

That is, the lighting device of the present invention includes a light source having a light emitting section, a primary mirror that reflects light from the light source toward the irradiated section, and a secondary mirror that reflects the light from the light source toward the primary mirror. the light source and the secondary mirror have a relationship in which light emitted from the light source light emitting part and reflected by the secondary mirror returns to the light source light emitting part again;
The primary mirror and the light source are characterized in that the focal point of the primary mirror and the position of the light emitting part of the light source are offset.

In the present invention, the shape of the primary mirror does not matter. For example, a parabolic mirror, an ellipsoidal mirror, an arbitrary aspherical mirror, etc. can be used. As the secondary mirror, a spherical mirror, a spherical Fresnel mirror, a micro-Dach mirror, etc. can be used. The reason why the secondary mirror and the light source should be in such a relationship that light emitted from the light emitting part of the light source and reflected by the secondary mirror returns to the light emitting part will be explained later. On the other hand, it has been empirically discovered that it is preferable to make the focal point of the primary mirror and the position of the light emitting part of the light source not coincide with each other. The amount of displacement between the light emitting part position of the light source and the focal position of the primary mirror is determined depending on each lighting device.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to illustrated embodiments. 1 and 2 show an embodiment of a lighting device according to the present invention. This embodiment uses an ellipsoidal mirror as the primary mirror 11 and an annular spherical mirror as the secondary mirror 13. Secondary mirror 1
3 has an illumination aperture 13W in the center centered on the illumination optical axis O.
have. This secondary mirror 13 is located at the open end of the primary mirror 11, and the central light emitting portion 12C of the light source 12 is located at its spherical center Or.

As is well known, the primary mirror 11 has a first focus f1 and a second focus f2. The present invention is characterized in that the first focus f1 of the primary mirror 11 and the spherical center Or of the secondary mirror 13 (that is, the central light emitting part 12C of the light source 12) are not made to coincide, but are offset in the direction of the illumination optical axis O. be. FIG. 1 shows a distance a from the primary mirror 11 to the rear with respect to the center light emitting part 12C of the light source 12.
FIG. 2 shows an embodiment in which the primary mirror 11 is similarly offset forward by a distance b. In the figure, the offset amounts a and b are exaggerated.

The amount of offset and its direction are set by simulation using a computer depending on factors such as the shape of the primary mirror 11 and the size of the light source 12. By appropriately setting this offset amount and its direction, if there is no offset, that is, the primary mirror 11
Compared to the case where the first focus f1 of the secondary mirror 13 coincides with the spherical center Or of the secondary mirror 13, the light amount distribution can be improved and the light utilization efficiency can be increased. The first focal point f1 of the primary mirror 11 and the spherical center Or of the secondary mirror 13 are offset as described above, whereas the spherical center Or of the secondary mirror 13 and the central light emitting part 12 of the light source 12
C is strictly matched. The reason for this is shown in Figures 3A to 3.
C will be explained.

FIG. 3A shows a case where the central light emitting portion 12C of the light source 12 coincides with the spherical center Or of the secondary mirror 13. In this case, the light directed from the light source 12 to the secondary mirror 13 is
It is reflected by the secondary mirror 13 and returns to the light source 12 again. In other words, the image of the light source 12 formed by the secondary mirror 13 is formed to coincide with the light source 12 without aberration. On the other hand, as shown in Figures 3B and 3C,
When the center light emitting part 12C of the light source 12 is shifted from the spherical center Or of the secondary mirror 13, the image 12 of the light source 12 by the secondary mirror 13
I is formed at a point symmetrical position with respect to the spherical center Or with a size multiplied by a magnification. This means that regarding the primary mirror 11,
Since the light source 12 and the image 12I of the light source 12 are located at different positions, this is substantially equivalent to increasing the size of the light source light emitting section. As the size of the light emitting part increases,
Obviously, this results in a reduction in the efficiency of light collection onto the illuminated area.

FIG. 4 shows an embodiment in which a spherical Fresnel mirror 14 is used in place of the secondary mirror 13 of the embodiment shown in FIG. In this spherical Fresnel mirror 14, each fine reflecting spherical surface 14a forms a spherical surface centered on the spherical center Or. Therefore, the same effect as the embodiment shown in FIG. 1 can be obtained, and
In addition to this, there is an advantage that it can be made more compact.

FIG. 5 shows an embodiment in which a micro roof mirror 15 is used in place of the secondary mirror 13 of the embodiment in FIG. The micro-Dach mirror 15 is an optical element that reflects an incident light beam in the same (strictly parallel) direction as the incident light beam. 6A and 6B show an example of this, in which fine reflection patterns having a pair of roof reflection surfaces 15a that are perpendicular to each other are aligned. Figure 6A shows the same fine patterns arranged side by side, and Figure 6B shows fine patterns arranged so that the bisector of the angle between the pair of reflective surfaces of each roof mirror passes through the light emitting point 12C in order to increase efficiency. This is an example of a pattern. This embodiment also provides the same effect as the embodiment shown in FIG. 1, and in addition has the advantage of being more compact.

Next, the effects of the present invention will be explained using specific examples. 7A, 7B, and 7C show the device of the present invention, primary mirror 1
1, and a second comparative example in which the primary mirror 11 is the only reflecting mirror. Now, in these lighting devices, the size of the light source 12: φ4 mm spherical primary mirror 11; ellipsoidal mirror, f1 = 20 mm, f2 = 400 m
m, conic coefficient K = -0.819, diameter of the hole on the illumination optical axis O for passing the light source 12 φd = 16 mm Secondary mirror 13: spherical mirror, radius R = 44 mm Area to be illuminated: φA = φ36 mm From the light source 12 to the Distance to area; WD=200mm
Intake angle of light ray from light source 12 by reflecting mirror; θ=1
The offset amount of the 20° secondary mirror 13; a = 0.4 mm, and the results of examining the illuminance distribution and illuminance ratio (assuming the illuminance at the center of the device of the present invention is 1) within the illuminated area are shown in FIG. 8, respectively.
Shown in A, 8B, and 8C. From this figure, compared to the first and second comparative examples, the lighting device according to the present invention exhibits an excellent illuminance distribution in which a sufficient amount of light is obtained especially in the center and the amount of light gradually decreases toward the periphery. is understood.

In addition, in this comparative example, the light collection efficiency (luminous flux in the illuminated area/total luminous flux of the light source 12), the overall reflecting mirror size of the primary mirror 11 and the secondary mirror 13 (φDmm×Hmm),
Table 1 shows the results of examining the F number of the projection lens for taking in the luminous flux within the illuminated area.

[0016]

[Table 1] From this table, it can be seen that the illumination device of the present invention can obtain better light collection efficiency, and can also reduce the size of the reflecting mirror, especially when compared with the second comparative example.

[0017]

As described above, the present invention provides a lighting device having a primary mirror and a secondary mirror. By establishing the relationship between the light source and the light emitting part, the light rays reflected by the secondary mirror can be returned to the primary mirror without substantially increasing the size of the light source. By offsetting the focal point of the light source and the position of the light emitting part of the light source,
It is possible to obtain a preferable illuminance distribution that prevents so-called hollow spots and high efficiency.

[Brief explanation of drawings]

FIG. 1 is an optical configuration diagram showing an embodiment of a lighting device according to the present invention.

FIG. 2 is an optical configuration diagram showing another embodiment of the illumination device according to the present invention.

FIGS. 3A, 3B, and 3C are optical configuration diagrams illustrating the relationship between the light source and the secondary mirror of the lighting device according to the present invention.

FIG. 4 is an optical configuration diagram showing a modification of the illumination device according to the present invention.

FIG. 5 is an optical configuration diagram showing another modification of the lighting device according to the present invention.

6A and 6B are enlarged views showing a configuration example of the micro roof mirror shown in FIG. 5. FIG.

7A, 7B, and 7C are optical configuration diagrams of a lighting device according to the present invention, a first comparative example, and a second comparative example.

8A, 8B, and 8C are graphs showing the illuminance distribution and illuminance ratio of the illumination devices of FIGS. 7A, 7B, and 7C.

[Explanation of symbols]

11 Primary mirror 12 Light source 12C Center light emitting part 13W lighting aperture Or Secondary mirror spherical center (focal point) 13 Secondary mirror 14 Spherical Fresnel mirror 14a Fine reflective spherical surface 15 Micro roof mirror 15a Roof reflective surface O Illumination optical axis a b Offset amount

Claims (4)

[Claims] 1. A light source comprising: a light source having a light emitting section; a primary mirror that reflects light from the light source toward an irradiated section; and a secondary mirror that reflects light from the light source toward the primary mirror. and the secondary mirror have a relationship in which the light emitted from the light source light emitting part and reflected by the secondary mirror returns to the light source light emitting part again, and the primary mirror and the light source have a relationship between the focal point of the primary mirror and the light emitting part position of the light source. A lighting device characterized by being arranged in an offset manner. 2. The lighting device according to claim 1, wherein the secondary mirror is a spherical mirror. 3. The lighting device according to claim 1, wherein the secondary mirror is a spherical Fresnel mirror. 4. The lighting device according to claim 1, wherein the secondary mirror is a micro roof mirror.