KR20070021052A - Illuminator, led illuminator, and imaging device with illuminator - Google Patents

Abstract

The present invention includes an image forming mechanism 14 and an LED lighting device 20 for emitting illumination light to an image forming area of the image forming mechanism 14. The LED lighting device 20 includes a light emitting module 21 having a light emitting element 21a disposed therein; A Fresnel lens 22 for causing light from the light emitting module 21 to be parallel rays of light; A pair of lens arrays 23 and 24 disposed in the direction of light emitted from the light source and shaped into rectangular shapes of parallel rays formed by the Fresnel lens 22; And an adjusting mechanism 25 for adjusting the gap between the lens arrays 23 and 24 according to the image forming area of the image forming mechanism 14.

Lighting device, LED, light emitting element, illuminance, Fresnel lens, lens array, collimation unit

Description

Lighting device, LED lighting device, and image forming apparatus having lighting device {ILLUMINATOR, LED ILLUMINATOR, AND IMAGING DEVICE WITH ILLUMINATOR}

1 is a perspective view showing a personal digital assistant having a digital camera incorporating a lighting apparatus according to a first embodiment of the present invention.

2 is an explanatory diagram schematically showing an LED flash embedded in a personal digital assistant.

3 is a plan view showing a lens array embedded in the LED flash.

4 is an explanatory diagram showing a light emitting region of an LED flash.

5 is an explanatory diagram showing a light emitting region of an LED flash.

Fig. 6 is an explanatory diagram showing the relationship between the illuminated area R and the image forming area Q of the personal digital assistant.

7 is an explanatory diagram showing a relative illuminance of the LED flash compared to the illuminance of a general lighting device.

8 is an explanatory diagram showing a light emitting region of a lighting apparatus according to a comparative example.

9 is an explanatory diagram showing a light emitting region of an LED flash.

10 is an explanatory diagram showing a relationship between a drive current value and a luminous flux.

Fig. 11 is an explanatory diagram showing the relationship between the drive current and the central illuminance at a position 1 m away from the LED lighting apparatus.

Fig. 12 is a vertical sectional view schematically showing the main part of a mobile telephone according to the second embodiment of the present invention.

Fig. 13 is a vertical sectional view schematically showing the main part of a mobile telephone according to the third embodiment of the present invention.

14 is an explanatory diagram showing the effect of a Fresnel lens.

15 is an explanatory diagram showing the effect of a Fresnel lens.

Fig. 16 is a sectional view showing a modification using the reflector.

17 is a cross-sectional view illustrating an example of an LED lighting apparatus.

18 is an explanatory diagram showing directing characteristics of the LED lighting apparatus.

19 is a cross-sectional view illustrating an example of an LED lighting apparatus.

20 is an explanatory diagram showing the directivity characteristics of the LED lighting apparatus.

21 is an explanatory diagram showing the relationship between the illuminated area P and the image forming area Q in the prior art.

<Description of the symbols for the main parts of the drawings>

14: image forming mechanism

20: LED lighting device

21: light emitting module

22: Fresnel lens

23, 24: lens array

25: adjusting mechanism

The present invention relates to an image forming apparatus having an illuminating device and an illuminating device to be used as a light source for a projector, a digital camera, and the like. It relates to a lighting device designed to be.

LED lighting devices use a light emitting module in which a plurality of LED elements (light emitting elements) are mounted on a substrate, and are known to have various advantages such as adjustment of color tone. Such LED lighting devices can also be used for indoor lighting, shop lighting, and stage lighting (see, for example, Japanese Patent Application Laid-Open No. 2004-22257). Such LED lighting devices can also be used as LED flashes for digital cameras or mobile phones with cameras.

For example, a blue LED 102 is mounted on the ceramic substrate 100 as shown in FIG. Light (not shown) from the blue LED 102 is emitted directly, but part of it is reflected by the reflector plate 104 and emitted to the outside. At this time, the light passes through the yellow fluorescent substrate 106 and becomes fake white. In this case, as shown in Fig. 18, the light from the light source exhibits a directing characteristic in which 2θ _1/2 is 110 °, which is approximately equally diffused (Lambertian).

The viewing angle of a digital camera or a camera built into a mobile phone is generally about 60 °. Therefore, the orientation angle of 110 ° as described above is too wide. To cope with this, a structure as shown in FIG. 19 is proposed, in which a blue LED 112 is mounted on the ceramic substrate 110 and the blue LED 112 is sealed in the fluorescent substrate 113, Reduce the angle of orientation. In this structure, the light from the LED 112 passes through the fluorescent substrate 113, a part of the light is reflected by the reflecting plate 114, the rest is emitted directly to the outside. At this time, as shown in Fig. 20, 2θ _1/2 is 50 °.

Using the above-described camera LED lighting device has the following problems. Specifically, the illuminated area of the LED lighting device as shown in Fig. 17 or 18 is almost circular, so that the illuminance is the highest at the center, and gradually decreases with the increase in the directing angle. In order to ensure uniform illuminance throughout the image forming area, an area larger than the image forming area must be illuminated, which requires a plurality of LEDs emitting a large amount of light. However, LED flashes used in digital cameras or mobile phones with cameras do not have sufficient illumination due to battery capacity or the configuration of LED flashes. Also, the periphery is dark compared to the center, which causes deterioration of image quality at the periphery. In addition, the blue light emitted from the LED and the yellow light emitted from the fluorescent color light are substantially different in the divergence position or the directing angle, and as a result, the illuminated area may not be uniform in color.

As shown in Fig. 21, the illuminated area P of the LED lighting apparatus is almost circular, but the image forming area Q captured by the camera is a rectangle whose width and length ratio is 4: 3. Light that does not fit inside the rectangle is not used and is thus wasted. In addition, the camera of the zooming operation has a narrower image forming range, but the illuminated area is the same size. This results in an enlarged area that is not in the image forming area, which increases the area that is not used and wasted.

Accordingly, it is an object of the present invention to provide a lighting device that provides illumination with sufficient and uniform illumination even if a light emitting device such as an LED having a relatively low output or other light emitting devices is used, and also provides an LED lighting device and a lighting device. It is to provide an imaging device having.

One aspect of the present invention provides a light source having a light emitting element disposed therein; A collimating unit for causing light from the light source to be parallel rays of light; And a lens array for shaping the parallel rays formed by the collimation unit. The lens array also functions to shape the parallel light rays formed by the collimation unit.

Another aspect of the invention provides a light source having a light emitting element disposed therein; A collimating unit for causing light from the light source to be parallel rays of light; A pair of lens arrays arranged in a direction of light emitted from the light source, the pair of lens arrays forming a rectangular parallel ray formed by the collimating unit; And an adjustment mechanism for adjusting the spacing between the pair of lens arrays.

Another aspect of the invention includes an image forming apparatus and a lighting apparatus for emitting illumination light to an image forming region of the image apparatus, the lighting apparatus comprising: a light source having a light emitting element disposed therein; A collimating unit for causing light from the light source to be parallel rays of light; A pair of lens arrays arranged in a direction of light emitted from the light source, the pair of lens arrays forming a rectangular parallel ray formed by the collimating unit; And an adjusting mechanism for adjusting the distance between the pair of lens arrays in accordance with the image forming area of the image forming mechanism.

According to the present invention, illumination with sufficient and uniform illuminance is obtained even when a light emitting element having a relatively low output is used.

Advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the present invention can be realized and obtained by means and combinations particularly pointed out below.

The accompanying drawings are included in and constitute a part of the detailed description of the invention, illustrate embodiments of the invention, and serve to explain the principles of the invention in conjunction with the generic description set forth above and with reference to the embodiments set forth below. Do it.

1 is a perspective view showing a personal digital assistant 10 having a digital camera incorporating a lighting apparatus according to a first embodiment of the present invention. 2 is an explanatory diagram schematically showing the LED flash 20 embedded in the personal digital assistant 10. 3 is a plan view of lens arrays 23 and 24 embedded in the LED flash 20. FIG. 6 is an explanatory diagram showing the relationship between the illuminated area R and the image forming area Q. FIG.

The personal digital assistant 10 has a cuboid housing 11. On the surface of the housing 11, a display LCD 12 and various operation buttons 13 are arranged. On the rear surface of the housing 11, a CCD camera (image forming apparatus) 14 having a zoom lens and an LED flash (lighting apparatus) 20 is disposed.

The LED flash 20 includes a light emitting module 21 in order along the optical axis (C); Fresnel lens 22 made of acrylic material (example of resin material); A pair of lens arrays 23 and 24 made of polycarbonate material; And an adjustment mechanism 25 for adjusting the distance between the lens arrays 23 and 24 based on the distance signal from the CCD camera 14. In this embodiment, acrylic resins and polycarbonate resins are used as materials for the lens arrays 23 and 24. However, the material of the lens is not limited to them.

The light emitting module 21 has one or two LED elements 21a. The LED element 21a is adjusted to emit white light by combining blue and yellow, for example, by applying a yellow fluorescent substrate to a 500 × 500 μm GaN blue LED. The light beam of 30-40 lm is obtained from the LED element 21a. Note that the LED element 21a for use in the light emitting module 21 is not limited to a blue LED.

Each lens array 23, 24 comprises 23 × 17 spherical lenses each of which has a radius of 0.4 mm (each an example of a refractive convex lens), each of which has a length of 10 mm, 10 mm It is configured to have a width of and a thickness of 0.5 mm. These spherical lenses form fly-eye optics. Therefore, the light passing through the fly-eye optical system becomes uniform in shape. The function of the adjustment mechanism 25 is to adjust the gap between the lens arrays 23 and 24 based on the distance signal from the CCD camera 14. The spacing between the lens arrays 23 and 24 is determined in accordance with the dimensions of the projection area. In the present embodiment, the lens arrays 23 and 24 are separate components. However, the lens arrays 23 and 24 can be integrated by injection molding. According to the design of each spherical lens described above, the light can be easily shaped into a rectangle. In the case where the projection area is fixed, the adjustment mechanism 25 can be omitted.

In the personal digital assistant 10 configured as such, the LED flash 20 is turned on when there is not enough light to perform image formation by the CCD camera 14. In this case, the light emitted from the blue LED 21a is shaped into collimate parallel rays by an angle of divergence of 30 ° (total angle) by a Fresnel lens 22 disposed immediately behind the blue LED 21a. )do. Collimated light is incident on lens arrays 23 and 24.

In this case, the distance between the lens arrays 23 and 24 is determined by the area to be illuminated. For example, if the interval between the lens arrays 23 and 24 is zero, as shown in Fig. 4, a light emitting area of 1.2 x 1.6 m is obtained at a distance of 1.5 m. If the distance between the lens arrays 23 and 24 is 0.13 mm, as shown in Fig. 5, a light emitting area of 0.85 x 1.13 m is obtained at a distance of 1.5 mm.

This effect is improved by matching the distance between the lens arrays 23 and 24 with the precision of the zoom of the CCD camera 14. Specifically, an image forming area is calculated from the degree of zoom of the CCD camera 14, and the distance between the lens arrays 23 and 24 is adjusted to match this image forming area. For example, the spacing between the lens arrays 23 and 24 can be set to 0 or 0.13 mm as in the above examples.

On the other hand, the shape of the illuminated area R is almost rectangular as shown in Fig. 6, whereby the area where the emitted light is wasted is minimized. Thus, the low output of the LED 21a can be used sufficiently for the LED flash 20. In conclusion, sufficiently bright illumination can be ensured without increasing battery capacity.

The effects of the lens arrays 23 and 24 will now be described. For example, in the case of an LED lighting device as shown in FIG. 17, the illuminance distribution on the optical axis, for example at a position 50 cm away from the device, has the highest illuminance at the center and toward the edge as indicated by the dotted line in FIG. Decreases gradually. In the case of the LED lighting device 20 using the lens arrays 23 and 24, the illuminance gradually decreases from the center to the edge as shown by the solid line in Fig. 7, and decreases rapidly outside the light emitting area. That is, using the lens arrays 23 and 24 ensures uniform illumination.

Next, the effect of shaping the light into a rectangle is described. Fig. 8 is a schematic view showing the light emitting area T, the illuminance of the edge of which is 1 m away from the LED lighting device (comparative example) shown in Fig. 17 with a dispersion angle (= 2θ _1/2 ) of 50 °. In half of the illuminance of the center. At this time, the diameter of the light emitting region T is the diameter of a circle or ellipse having a diameter of approximately 93 cm. FIG. 9 is a schematic diagram showing a light emitting area K 1 m away from the LED flash 20 as shown in FIG. At this time, the diagonal of the light emitting area K is approximately 93 cm.

10 is an explanatory diagram showing a relationship between a drive current value and a luminous flux. Fig. 11 is an explanatory diagram showing the relationship between the drive current and the central illuminance at a position 1 m away from the LED lighting apparatus. In the graph, α represents an LED flash 20 and β represents a comparative example. Assume that the relationship between the amount of light emitted from the LED lighting device (luminous flux) and the central illuminance of the area to be illuminated is expressed by the light use efficiency by illuminance / luminous flux (lx / lm). In this case, the light usage efficiency of the comparative example and the light usage efficiency of the LED flash 20 are 0.9 and 1.6, respectively, when driven at 200 mA. This means that the LED flash 20 has a higher light use efficiency than the comparative example. In other words, light use efficiency is improved by making the light emitting area rectangular rather than circular.

As described above, the personal digital assistant 10 having a digital camera with a built-in lighting device ensures illumination with sufficient and uniform illumination even if a relatively low output LED is used as the light emitting device.

Fig. 12 is a vertical sectional view schematically showing the main part of the cellular phone 30 according to the second embodiment of the present invention. Components of the same function as those shown in FIG. 2 are denoted by the same reference numerals in FIG. 12, and their detailed description is omitted.

The mobile phone 30 has an LED flash 20 embedded in the housing 31. Referring to FIG. 12, a lens module including a light emitting module 21, a Fresnel lens 22, and lens arrays 23 and 24 is mounted on a substrate 32. Light from the light emitting module 21 is emitted through the transparent cover 33 fitted to the upper portion of the housing 31. In this case, the light emitting module 21 is soldered to the substrate 32, and the lens module is bonded to the substrate 32 with an adhesive.

Other methods may also be used, such as forming notches in the light emitting module 21 and inserting the lens module into the light emitting module 21.

Fig. 13 is a vertical sectional view schematically showing the main part of the personal digital assistant 40 according to the third embodiment of the present invention. Components of the same function as those shown in FIG. 12 are denoted by the same reference numerals in FIG. 13, and their detailed description is omitted.

In the cellular phone 40, the lens module is fitted into the recess 42 formed in the housing 41.

Fresnel lens 22 and lens arrays 23 and 24 are both separate lenses. However, one side of the lens array 23 may be a Fresnel lens and the other side may be a lens array. According to the present invention, when the light emitting area is circular rather than rectangular, more uniform illumination is obtained by the lens arrays 23 and 24.

14 is an explanatory diagram showing the effect of collimation by the Fresnel lens 22. FIG. FIG. 14 shows an example of using one Fresnel lens 22 disposed at a position 3.1 mm from the light emitting module 21. FIG. 15 shows an example in which the convex lens 26 is disposed in the vicinity of the light emitting module 21, and the Fresnel lens 22 is disposed at a position 6 mm from the light emitting module 21. As shown in FIG. The light rays shown in FIG. 15 are collimated closer than those shown in FIG. 14, and the efficiency is improved by 20%.

The above-described embodiments use a method in which the rays are collimated by the Fresnel lens 22, but alternatively the rays collimated by the curved reflector 28 and the LED 27 emitting sideways are arranged in a lens array. The method of incidence to (23, 24) can be used.

The method of adjusting the lens spacing uses an electromagnetic actuator, an electrostatic actuator, or the like. In the above-described embodiment, an electromagnetic actuator is used.

LED lighting devices can be used in mobile phones with cameras, but can also be used in digital cameras or projectors.

It is to be understood that the present invention is not limited to the above-described embodiments and is intended to include various modifications within the spirit and scope of the present invention. Moreover, a suitable combination of the various elements of the above-described embodiments makes it possible to construct various inventions. For example, some structural elements may be omitted from all structural elements of each embodiment, or structural elements of different embodiments may be appropriately combined.

Additional advantages and modifications will readily appear to those skilled in the art. Thus, in its broadest sense, the invention is not limited to the details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit and scope of the inventive concept as defined by the appended claims and their equivalents.

According to the present invention, it is possible to provide illumination with sufficient and uniform illuminance even when using a light emitting element such as an LED having a relatively low output or another light emitting element.

Claims (7)

A light source having a light emitting element disposed therein, A collimation unit for causing light from the light source to become parallel rays of light, And an array of lenses for shaping the parallel rays formed by the collimation unit. The lighting device of claim 1, wherein the collimating unit comprises a Fresnel lens. The illuminating device according to claim 1, wherein the collimating unit has a reflecting structure that reflects light from the light emitting element. The lighting device of claim 1, wherein the lens array is formed of a plurality of refractive convex lenses. The lighting device according to claim 1, wherein the light emitting element has a white LED formed by combining a blue LED with a yellow fluorescent substrate. A light source having an LED element disposed therein, A collimation unit for causing light from the light source to become parallel rays of light, A pair of lens arrays arranged in the direction of light exiting the light source, the pair of lens arrays shaping parallel rays formed by the collimation unit, An LED lighting device comprising an adjustment mechanism for adjusting the spacing between a pair of lens arrays. An image forming apparatus having an illuminating device, With an image forming apparatus, An illuminating device for emitting illumination light to an image forming area of the imaging apparatus, The lighting apparatus includes a light source having a light emitting element disposed therein; A collimating unit for causing light from the light source to be parallel rays of light; A pair of lens arrays arranged in the direction of light exiting the light source, the pair of lens arrays shaping parallel rays formed by the collimating unit; And an adjusting mechanism for adjusting the distance between the pair of lens arrays in accordance with the image forming area of the image forming mechanism.

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