JPWO2012053387A1 - Optical element and illumination device - Google Patents

Abstract

Provided is an optical element capable of obtaining a good light distribution even when the size of the light source with respect to the optical element is relatively large or when a plurality of light sources are used, and more uniformly illuminating the irradiated surface. The position of the light emitting point on the optical axis is taken as the coordinate origin O, the length of the straight line LM connecting the arbitrary point on the second surface P2 and the origin O is M, and the straight line LM and the optical axis (z axis) When the angle formed is α and the length between the intersection D of the straight line LM and the first surface P1 and the origin O is m, the lens thickness (M−m) of the first surface P1 and the second surface P2 is The extreme value or the inflection point has a maximum within the range of 0 ° ≦ α ≦ 90 °, and the following equation is satisfied when the value of α is α1. 15 ° ≦ α1 ≦ 80 ° (1)

Description

  The present invention relates to an optical element suitable for an illumination device using a surface-emitting light source, and an illumination device using the optical element.

  In fields such as indoor lighting, there is a demand for a lighting device that uniformly illuminates a wider area. In consideration of ease of attachment, there is a demand for an optical member for a lighting device having a rotationally symmetric shape. Further, from the viewpoint of energy saving or the like, use of an LED light source or the like with low current consumption is being studied.

  One of the performance requirements for the lighting device is whether the luminance is sufficient. This is an essential requirement for basic performance for lighting. In order to achieve sufficient luminance, an approach from two directions of increasing the efficiency of the optical element and ensuring the luminance of the light source itself is performed.

  In the former approach, the efficiency of light utilization is improved by devising the configuration of the optical element. However, since the efficiency decreases basically as the optical element is downsized, an appropriate design on the optical element side is required. On the other hand, in the latter approach, for example, when an LED light source is used, since the brightness of the LED chip alone is often insufficient at present, a form of using a plurality of LED chips is often adopted.

  As described above, in the optical element for the lighting device using the LED light source, the optical element is downsized and a plurality of LED chips are used. The area of the light emitting surface is increased. This means that the light source cannot be regarded as a point light source. For this reason, when considering the configuration of the optical element, it is necessary to consider the spatial spread of the light emitting position.

  In order to illuminate a wider range as uniformly as possible, it is desirable that the intensity center angle (peak angle) of the light distribution has an angle with respect to the normal direction of the light emitting surface. The illuminance distribution on the irradiated surface and the illuminable range (angle) vary depending on the peak angle of the light distribution, the shape of the peak, and the way of spreading.

  Patent Document 1 discloses a lens of an illumination device that can illuminate a limited region (irradiated region) such as a subject brightly and uniformly. Patent Document 2 discloses an illumination lens that can widen the directivity of a light source and realize a good light distribution.

JP 2007-294187 A JP 2010-140769 A

  However, since the optical elements of Patent Documents 1 and 2 have the best performance when the light source can be regarded as a point light source, when the optical element is downsized and the light source is relatively large, or inherently When a light source having a light emitting surface with a large area is used (including the case of using a plurality of light sources that emit surface light), there is a problem that sufficient light distribution characteristics cannot be obtained.

  More specifically, the optical element disclosed in Patent Document 1 achieves a wide light distribution characteristic when a point light source is used. However, when the area of the light source is large or there are a plurality of light sources, the optical element is realized. Needs to be very large, or illuminance unevenness tends to occur on the irradiated surface, and good light distribution characteristics cannot be obtained. Further, in the optical element disclosed in Patent Document 2, a uniform and good light distribution is obtained by using the total reflection of the light of the surface light source having a strong light distribution near 0 degrees. Since the method of returning the reflected light to the light source and reflecting it is adopted, the reduction in the amount of light due to repeated reflection cannot be denied. In addition, the surface in the total reflection region has a problem that high accuracy is required and the cost is increased.

  As described above, when the light source is relatively large with respect to the optical element (for example, the size L of the light source is larger than 1/4 of the optical element diameter), it becomes difficult to control the light distribution. On the other hand, even when trying to distribute light with only one optical element, the problem that it becomes difficult to obtain the desired distribution of light distribution appears.

  The present invention provides an optical element capable of obtaining a good light distribution even when the size of the light source relative to the optical element is relatively large or using a plurality of light sources, and more uniformly illuminating the irradiated surface. The purpose is to provide.

The optical element according to claim 1 is an optical element for an illuminating device using a light source having a light emitting surface, the optical axis of the light source being a z axis, and the light emitting surface being directed in a positive direction of the z axis. The first surface on which the light emitted from the light emitting surface is incident, and the second surface that emits the light incident on the first surface,
The position of the light emitting point on the optical axis is taken as the origin of coordinates, the length of a straight line connecting an arbitrary point on the second surface and the origin is M, and the angle formed by the straight line and the optical axis is α. , Where m is the length between the intersection of the first surface and the origin on the straight line, the lens thickness (M−m) of the first surface and the second surface is 0 ° ≦ α ≦. It has an extreme value or an inflection point that becomes a maximum within a range of 90 °, and when the value of α at that time is α1, the following expression is satisfied.
15 ° ≦ α1 ≦ 80 ° (1)

  FIG. 1 is a cross-sectional view of an optical element showing an example of the present invention, but the present invention is not limited to the following example. In FIG. 1, a rotationally symmetric optical element OE has a light source OS arranged in its internal space. The optical axis of the light source OS means the center of the light emitting surface in the case of a single large area light source. For example, when using a plurality of LED light sources, the optical axis of the light source OS is shown in FIG. As shown, it shall mean a perpendicular line passing through the center z of the circumscribed circle OC of the LED light source. In this case, a plane including the light emitting surface of the LED light source in a region surrounded by the circumscribed circle OC is defined as a light emitting surface, and the size L of the light emitting surface is a radius of the circumscribed circle.

  As shown in FIG. 1, when the optical axis of the light source OS is set to the z axis and the light emitting surface EP of the light source OS is installed in the positive direction of the z axis, the light that enters the light emitted from the light emitting surface EP is incident. The inner surface of the element OE is defined as a first surface P1, and the outer surface that emits light incident from the first surface P1 is defined as a second surface P2.

The position where the optical axis and the light emitting surface intersect on the optical axis is taken as the origin O of coordinates, the length of the straight line LM connecting the arbitrary point F on the second surface P2 and the origin O is M, and the straight line LM and the optical axis The thickness of the first surface P1 and the second surface P2 is defined as α where the angle formed with the (z axis) is α and the length between the intersection D with the first surface P1 and the origin O in the straight line LM is m. (M−m) has an extreme value or an inflection point that is maximal within a range of 0 ° ≦ α ≦ 90 °, and the following equation is satisfied when the value of α is α1.
15 ° ≦ α1 ≦ 80 ° (1)

  By using the optical element OE having such a shape, the light distribution peak of the light beam emitted from the optical element OE can be formed at an angle other than 0 degrees, and an arbitrary irradiation surface can be illuminated more uniformly. It becomes possible. The inflection point here refers to the change in the lens thickness (Mm) relative to the change in the angle α when the horizontal axis is the angle α and the vertical axis is the lens thickness (Mm). For example, when the lens thickness (M−m) gradually decreases or increases according to the change in the angle α and no longer changes (the lens thickness becomes constant), It shall be the starting point.

  It is desirable that the lens thickness (M-m) has an extreme value that is maximum in the range of 15 ° ≦ α1 ≦ 80 °. More desirably, 60 ° ≦ α1 ≦ 80 °.

  According to a second aspect of the present invention, in the invention of the first aspect, the sag amount of the surface shape of the second surface increases with increasing distance from the optical axis when the vertex of the second surface is 0. The amount of change is monotonously decreasing.

  Referring to FIG. 1, the sag amount S of the surface shape of the second surface P2 refers to the “negative optical axis direction distance” from the surface vertex of the second surface P2 to any point on the second surface P2. . The sag amount S of the surface shape of the second surface P2 is preferably monotonically decreasing as the distance from the optical axis increases when the vertex of the second surface P2 is zero.

  The monotonic decrease here means that the center of curvature of the surface is in the negative direction of the optical axis. However, this is not the case when the radius of curvature near the paraxial axis is very large and can be regarded as a substantially flat surface. By setting it as such a shape, shape shaping | molding of a 2nd surface becomes easy and there exists a cost reduction effect. There may be a portion where the sag amount is constant. Further, the sag amount S at the intersection F between the straight line LM and the second surface P2 only needs to be monotonously decreased in a range of at least 0 ° ≦ α ≦ 45 °.

An optical element according to a third aspect is the optical element according to the first or second aspect, wherein an angle formed by a straight line connecting an arbitrary point on the first surface and the origin and the optical axis is β, Assuming that the length of a straight line connecting an arbitrary point on the surface and the origin is m (β), the maximum value of m (β) is m (β) max within the range of 0 ≦ β ≦ 60 °. The following expression is satisfied.
1 ≦ m (β) max / m (0) ≦ 2 (2)

  FIG. 3 is a cross-sectional view of an optical element showing an example of the present invention, but the present invention is not limited to the following example. In FIG. 3, an angle formed between an arbitrary point H on the first surface P1 of the optical element OE and the straight line Lb connecting the origin O and the optical axis (z axis) is β, and an arbitrary point on the first surface P1. When the length of the straight line Lb connecting H and the origin O is m (β), and the maximum value of the length m (β) is m (β) max within the range of 0 ≦ β ≦ 60 °, The expression (2) is satisfied.

By determining the length m (β) so as to satisfy this range, the peak of the light distribution angle in the optical element can be made wider. In addition, a relatively large light source or a plurality of light sources can be arranged as compared with the optical element. Furthermore, the processing of the optical element is easy. Note that the length m (β) is not limited to the range of 0 ≦ β ≦ 60 °, and the length m (β) may increase monotonously as the angle β increases. Further, the length m (β) may be constant regardless of the increase in the angle β. More preferably, the expression (2 ′) is satisfied.
1 <m (β) max / m (0) <2 (2 ')

  The optical element according to claim 4 is the invention according to any one of claims 1 to 3, wherein both the first surface and the second surface have a rotationally symmetric surface shape with respect to the optical axis. It is characterized by having.

  Since both the first surface and the second surface have a rotationally symmetric surface shape with respect to the optical axis, the direction, direction, angle, and the like of rotation are not limited during installation, and can be easily installed. Become.

  An optical element according to a fifth aspect is the optical element according to any one of the first to fourth aspects, wherein a plurality of the light sources are provided.

  By providing a plurality of the light sources, it becomes possible to form a brighter illuminance distribution. Further, in this case, the size L of the light emitting surface of the light source is a radius of a circumscribed circle around the origin that completely surrounds the plurality of light sources (see FIG. 2).

  An optical element according to a sixth aspect is the invention according to any one of the first to fifth aspects, wherein the surface shape of the second surface is defined by a plurality of surface shape formulas, and the surface shapes are connected. It is characterized by being formed.

  If the surface shape of the second surface is defined by a plurality of surface shape formulas and the surface shapes are formed continuously, it is possible to form a shape that is difficult to express with one surface shape formula. Further, when the portion where the surface shape is continuously formed has an abrupt sag amount change, there is an effect that uneven illuminance hardly occurs even when there are a plurality of light sources.

  An optical element according to a seventh aspect is characterized in that, in the invention according to any one of the first to fifth aspects, the second surface is expressed by one surface shape formula. When the second surface is expressed by a single surface shape formula, surface formation is facilitated.

  An optical element according to an eighth aspect of the present invention is the optical element according to the seventh aspect, wherein the point where the inclination of the surface shape becomes maximum and the origin are within the range where the second surface is represented by one surface shape formula. Is characterized in that γ ≧ α1.

  The angle γ connecting the point G where the inclination of the surface shape of the second surface is maximum and the origin is preferably γ ≧ α1. By satisfying this, a light distribution having a peak at a wider angle can be obtained. Here, the inclination of the surface shape is a value obtained by differentiating the surface shape formula of the second surface, and the location G where this value is maximum is the location where the differential value is maximum, for example, the location G shown in FIG. . In addition, the location where the differential value is maximum may be minimum depending on whether the distance from the optical axis is positive or negative or the curvature radius is positive or negative. It is even better if the location G is an extreme value.

  An optical element according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the length M is an extreme value or an inflection that is a maximum in a range of 15 ° ≦ α ≦ 80 °. It has the point.

  With reference to FIG. 1, the peak of the light distribution angle becomes a wider angle when the length M has an extreme value or an inflection point that becomes a maximum in a range of 15 ° ≦ α ≦ 80 °. Thereby, the light distribution angle becomes sufficiently wide. When α ≧ 15 °, a light beam having a large light quantity is emitted from the optical element at an angle of less than 15 °, and thus the light distribution angle is sufficiently widened.

  An optical element according to a tenth aspect is the optical element according to any one of the first to ninth aspects, wherein the lens thickness between the first surface and the second surface is (M−m). , (M−m) increases as the angle α increases, and has a maximum value in a range of 45 ° ≦ α ≦ 80 °.

  It is preferable that the lens thickness (M-m) of the first surface and the second surface increases monotonously and increases as the angle α increases, and has a maximum value in a range of 45 ° ≦ α ≦ 80 °. Specifically, the point where the local maximum is exerted as if it were a convex lens having an optical axis of angle α, so that the light beams emitted from the optical element across the portion converged in the optical axis direction of angle α. The luminous flux is as follows. As a result, a light beam in the front direction of the optical element having a relatively strong intensity can be emitted with an angle, and the light distribution angle can be widened.

An optical element according to an eleventh aspect is the invention according to any one of the first to tenth aspects, wherein the length M has an extreme value that becomes a maximum within a range of 0 ≦ α ≦ 90 °, When the value of α at that time is α2, the following expression is satisfied. Thereby, a light distribution having a peak at a wider angle can be obtained.
45 ° ≦ α2 ≦ 80 ° (3)

  An optical element according to a twelfth aspect is characterized in that in the invention according to any one of the first to eleventh aspects, the optical element has a negative power in a paraxial region. Since the optical element has a negative power in the paraxial region, it is possible to diverge a light beam in a strong front direction and widen a light distribution angle.

The optical element according to claim 13 is the invention according to any one of claims 1 to 12, wherein L is a distance between a position of the light emitting surface of the light source farthest from the origin and the origin. When the point C is separated from the origin on the optical axis by the distance L, the length of the straight line connecting the arbitrary point on the second surface and the point C is N, and the straight line and the optical axis Assuming that the angle formed is φ, the intersection between the straight line of φ = 60 ° and the second surface in the direction opposite to the optical axis side when viewed from the point C is C ′, and the straight line connecting C ′ and the origin is When the angle formed with the optical axis is α ′, the following expression is satisfied.
15 ° ≦ α ≦ α ′ (4)

  Referring to FIG. 45, at a point C that is a distance L from the origin O on the optical axis z, the length of a straight line Lc that connects an arbitrary point C ′ on the second surface P2 and the point C is represented by N, An angle formed by the straight line Lc and the optical axis z is φ. Here, when the intersection of the straight line Lc of φ = 60 ° in the direction opposite to the origin O when viewed from the point C and the second surface P2 is C ′, the straight line Lc ′ connecting the point C ′ and the origin O and the light When the angle formed with the axis z is α ′, the expression (4) is satisfied. By satisfying the expression (4), a wide portion of the lens can be used with an angle when the light beam is incident on the first surface, and the light beam after incident on the first surface can be angled. Thereby, the illuminating device which irradiates a wider range more uniformly can be provided.

  The optical element according to claim 14 is the invention according to any one of claims 1 to 13, wherein L is a distance between a position farthest from the origin of the light emitting surface of the light source and the origin. The length of the straight line connecting the origin and the intersection B, where B is the intersection of the straight line parallel to the optical axis and the first surface, passing through a point separated from the origin on the optical axis by the distance L. M (β) is constant or monotonically increased with an increase in angle β in the range of 0 ≦ β ≦ θ, where mB (θ) is the angle between the straight line and the optical axis. .

  FIG. 4 is a cross-sectional view of an optical element showing an example of the present invention, but the present invention is not limited to the following example. In FIG. 4, when the distance from the origin O to the position farthest from the origin O of the light emitting surface EP of the light source OS and the origin O is L, the point C separated from the origin O on the optical axis (z axis) by the distance L. If the intersection of the straight line Lb parallel to the optical axis and the first surface P1 is B, the length of the straight line Lmb connecting the origin O and the intersection B is mB (θ), and the straight line Lmb and the optical axis Assuming that the formed angle is θ, m (β) increases constant or monotonously as the angle β increases in the range of 0 ≦ β ≦ θ.

  This makes it possible to form a good light distribution even when a relatively large light source is used for the optical element. It is also easy to use a plurality of light sources. Thereby, even when the light quantity of the single LED used as the light source is insufficient, the light quantity can be increased by using a plurality of LEDs.

  A lighting device according to a fifteenth aspect includes the optical element according to any one of the first to fourteenth aspects.

  When the distance between the position of the light emitting surface EP of the light source OS farthest from the origin O and the origin O is L, the distance m (0) from the origin O to the intersection of the optical axis and the first surface P1 is L / Desirably greater than 2.

  The distance from the optical axis when M (α1) is maximized is given by Msinα1. The value of Msin α1 is preferably larger than L, where L is the distance between the position of the light emitting surface EP of the light source OS farthest from the origin O and the origin O. Therefore, α1 is desirably larger than the arc sine L / M. In this case, it is desirable that the increment of M is larger in the range of α ≧ α1.

  There may be many αs that maximize M (α1). Let α1 be the smallest α and let M (α1) be the distance from the origin.

  The thickness of the optical element changes from thin to thick and further thin as the angle α increases, and acts as if it were a convex lens with the optical axis rotated by α. Naturally, by taking such a power arrangement, the light condensing action is strongest in the α direction, and an intensity peak tends to appear near the angle.

  In order to obtain an ideal light distribution by a refractive optical system such as a lens, it is necessary to consider the power balance between the entrance surface and the exit surface for each angle of light incident on the optical element. It is possible to obtain a desired light distribution by calculating and optimizing the minute curvatures of the incident surface and the exit surface for each angle of the light beam.

  Originally, since there is a difference in refractive index between air and the lens, it is not sufficient to calculate the power of the lens for each angle of the light beam emitted from the light source. However, in illumination using a light source with a large size, Since the incident surface position and the incident angle are homogenized to some extent, this is not a problem. In the case of obtaining strictly, the power distribution can be obtained by performing ray tracing for each angle and calculating a minute curvature at a point through which the ray passes.

  When using a plurality of light sources, the point at which the sag amount M of the second surface is maximum is a location where two different surfaces are connected and continuously formed, and the amount of change in the surface shape at that location, In other words, when the amount of change in tilt is large, the angle of the light beam emitted from the second surface greatly changes between the light beam passing through the optical axis side and the side away from the optical axis from the point on the second surface. It is possible to realize a light distribution with no unevenness and an illuminance distribution without unevenness on the irradiated surface.

  As the light source, a planar light emitting element such as an LED or an organic EL is preferable. In particular, the surface on the optical element side is preferably flat, and more preferably a surface mount type.

  As a material of the optical element, plastic, glass, silicon resin, urethane resin, olefin resin, and gel can be used.

  According to the present invention, even when the size of the light source with respect to the optical element is relatively large or when a plurality of light sources are used, a good light distribution can be obtained and the irradiated surface can be illuminated more uniformly. An optical element can be provided.

It is sectional drawing of the optical element which shows an example of this invention. It is a figure which shows the definition of each numerical value in a some light source. It is sectional drawing of the optical element which shows an example of this invention. It is sectional drawing of the optical element which shows an example of this invention. It is an optical axis direction sectional view of the optical element concerning the 1st example. It is a figure which shows the light distribution characteristic of the optical element concerning a 1st Example, The vertical axis | shaft has taken the luminous intensity, and the horizontal axis has taken the angle with respect to the optical axis. It is a figure which shows the illumination intensity distribution of the optical element concerning a 1st Example, The illuminance ratio is set to the vertical axis | shaft, and the position from the optical axis z is taken as 0 mm on the horizontal axis. In the optical element concerning a 1st Example, it is the figure which took angle (alpha) on the horizontal axis, and took length M, m on the vertical axis | shaft. In the optical element concerning a 1st Example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is optical axis direction sectional drawing of the optical element concerning a 2nd Example. It is a figure which shows the light distribution characteristic of the optical element concerning a 2nd Example, and has taken the luminous intensity on the vertical axis | shaft, and the angle with respect to the optical axis on the horizontal axis. It is a figure which shows the illumination intensity distribution of the optical element concerning a 2nd Example, The illuminance ratio is set to a vertical axis | shaft and the position of the optical axis z is set to 0 mm on the horizontal axis | shaft, and the distance from this is taken. In the optical element concerning a 2nd Example, it is the figure which took angle (alpha) on the horizontal axis and took length M, m on the vertical axis | shaft. In the optical element concerning 2nd Example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is optical axis direction sectional drawing of the optical element concerning a 3rd Example. It is a figure which shows the light distribution characteristic of the optical element concerning a 3rd Example, The vertical axis | shaft has taken the luminous intensity, and the horizontal axis has taken the angle with respect to the optical axis. It is a figure which shows the illumination intensity distribution of the optical element concerning a 3rd Example, The illuminance ratio is set to a vertical axis | shaft, and the position from the optical axis z is set to 0 mm on the horizontal axis | shaft. In the optical element concerning a 3rd Example, it is the figure which took angle (alpha) on the horizontal axis, and took length M, m on the vertical axis | shaft. In the optical element concerning 3rd Example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is an optical axis direction sectional view of the optical element concerning the 4th example. It is a figure which shows the light distribution characteristic of the optical element concerning a 4th Example, The vertical axis | shaft has taken the luminous intensity, and the horizontal axis has taken the angle with respect to the optical axis. It is a figure which shows the illumination intensity distribution of the optical element concerning a 4th Example, The illuminance ratio is set to a vertical axis | shaft, and the position from the optical axis z is taken as 0 mm on the horizontal axis. In the optical element concerning a 4th Example, it is the figure which took angle (alpha) on the horizontal axis and length M, m on the vertical axis | shaft. In the optical element concerning a 4th Example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is an optical axis direction sectional view of the optical element concerning the 5th example. It is a figure which shows the light distribution characteristic of the optical element concerning a 5th Example, The vertical axis | shaft has taken the luminous intensity, and the horizontal axis has taken the angle with respect to the optical axis. It is a figure which shows the illumination intensity distribution of the optical element concerning a 5th Example, The illuminance ratio is set to a vertical axis | shaft, and the position from the optical axis z is set to 0 mm on the horizontal axis | shaft. In the optical element concerning a 5th Example, it is the figure which took angle (alpha) on the horizontal axis, and took length M, m on the vertical axis | shaft. In the optical element concerning a 5th Example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is an optical axis direction sectional view of the optical element concerning the 6th example. It is a figure which shows the light distribution characteristic of the optical element concerning a 6th Example, The vertical axis | shaft has taken the luminous intensity, and the horizontal axis has taken the angle with respect to the optical axis. It is a figure which shows the illumination intensity distribution of the optical element concerning a 6th Example, The illuminance ratio is set to a vertical axis | shaft, and the position from the optical axis z is set to 0 mm on the horizontal axis from this. In the optical element concerning a 6th Example, it is the figure which took angle (alpha) on the horizontal axis, and took length M, m on the vertical axis | shaft. In the optical element concerning 6th Example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is an optical axis direction sectional view of the optical element concerning the 1st comparative example. It is a figure which shows the light distribution characteristic of the optical element concerning a 1st comparative example, and has taken the luminous intensity on the vertical axis | shaft, and the angle with respect to the optical axis on the horizontal axis. It is a figure which shows the illuminance distribution of the optical element concerning a 1st comparative example, the illuminance ratio is set to a vertical axis | shaft, the position of the optical axis z is set to 0 mm on the horizontal axis, and the distance from this is taken. In the optical element concerning a 1st comparative example, it is the figure which took angle (alpha) on the horizontal axis, and took length M, m on the vertical axis | shaft. In the optical element concerning a 1st comparative example, it is the figure which took angle (alpha) on the horizontal axis, and took lens thickness (Mm) on the vertical axis | shaft. It is an optical axis direction sectional view of the optical element concerning the 2nd comparative example. It is a figure which shows the light distribution characteristic of the optical element concerning a 2nd comparative example, and has taken the luminous intensity on the vertical axis | shaft, and the angle with respect to the optical axis on the horizontal axis. It is a figure which shows the illuminance distribution of the optical element concerning a 2nd comparative example, the illuminance ratio is set to a vertical axis | shaft, and the position from the optical axis z is taken as 0 mm on the horizontal axis. In the optical element concerning the 2nd comparative example, it is the figure which took angle alpha on the horizontal axis, and took lengths M and m on the vertical axis. In the optical element concerning the 2nd comparative example, it is a figure which took angle alpha on the horizontal axis, and took lens thickness (Mm) on the vertical axis. It is sectional drawing of the optical element which shows an example of this invention. It is a figure which shows the sag amount of a 2nd surface in the optical element concerning a 1st Example. It is a figure which shows the sag amount of a 2nd surface in the optical element concerning a 2nd Example. It is a figure which shows the sag amount of a 2nd surface in the optical element concerning a 3rd Example. It is a figure which shows the sag amount of a 2nd surface in the optical element concerning a 4th Example. It is a figure which shows the sag amount of a 2nd surface in the optical element concerning a 5th Example. It is a figure which shows the sag amount of a 2nd surface in the optical element concerning a 6th Example. In the optical element concerning the 1st comparative example, it is a figure showing the amount of sag of the 2nd surface. In the optical element concerning the 2nd comparative example, it is a figure showing the amount of sag of the 2nd surface.

  Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a light source OS composed of a plurality of LEDs formed on a substrate (not shown) shows only the outline of the circumscribed circle, and the light emitting surface EP faces upward. The optical element OE, which has a rotationally symmetric shape around the optical axis center on both the outer and inner surfaces, is made of glass or resin, and a light source OS is disposed in the inner space, with air interposed therebetween.

  As shown in FIG. 1, the optical axis of the light source OS is the z axis, the light emitting surface EP of the optical element OS is made to coincide with the xy plane orthogonal to the z axis, and the light emitting surface EP of the light source OS is positive with respect to the z axis. When installed in the direction, the inner surface of the optical element OE that receives the light emitted from the light emitting surface EP is the first surface P1, and the outer surface that emits the light incident from the first surface P1 is the second surface P2. To do. The second surface P2 is defined by one or a plurality of surface shape formulas.

The position of the light emitting point on the optical axis is taken as the coordinate origin O, the length of the straight line LM connecting the arbitrary point on the second surface P2 and the origin O is M, and the straight line LM and the optical axis (z axis) When the angle formed is α and the length between the intersection D of the straight line LM and the first surface P1 and the origin O is m, the lens thickness (M−m) of the first surface P1 and the second surface P2 is The extreme value or the inflection point has a maximum within the range of 0 ° ≦ α ≦ 90 °, and the following equation is satisfied when the value of α is α1.
15 ° ≦ α1 ≦ 80 ° (1)

  In the following examples, the aspherical shape is obtained by substituting the numerical values shown in Table 1 or 2 with the vertex of the surface as the origin, the Z axis in the optical axis direction, and the height in the direction perpendicular to the optical axis as h. It shall be expressed by the following equation (1).

但し、
Ａｉ：ｉ次の非球面係数（ｉ＝３，４，５，６，・・・・２０）
Ｒ（レンズデータ表ではｒ）：曲率半径
ｋ：円錐定数
また、非球面係数において、１０のべき乗数（例えば２．５×１０^-02）をＥ（例えば２．５Ｅ−０２）を用いて表している。

However,
Ai: i-order aspherical coefficient (i = 3,4,5,6,... 20)
R (r in the lens data table): radius of curvature k: conic constant In addition, in the aspheric coefficient, a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). ing.

Example 1
FIG. 5 is a sectional view in the optical axis direction of the optical element according to the first embodiment. FIG. 6 is a diagram illustrating light distribution characteristics of the optical element according to the first example. FIG. 7 is a diagram illustrating the illuminance distribution of the optical element according to the first example. FIG. 8 is a plot of the optical element according to the first example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 9 is a plot of the optical element according to the first example with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 46 is a diagram illustrating the sag amount of the second surface in the optical element according to the first example. In the optical element according to the first embodiment, the second surface is formed by connecting two surfaces (aspherical surface and tapered surface) defined by different surface shape formulas, and a light source having a length L = 7.7 mm is used. When used, referring to FIG. 9, since (M−m) gradually increases as the angle α increases, and (M−m) is the maximum (maximum) angle α1 = 61.26 deg. 1) Expression is satisfied. Further, in the range of 0 ≦ β ≦ θ, m (β) increases constant or monotonously with the increase of the angle β, and m (β) max / m (0) = 1.21. Fulfill. Furthermore, the angle α2 = 61.26 deg at which M has an inflection point and becomes a maximum, and satisfies the expression (3). Further, α ′ = 75.30 deg, which satisfies the expression (4). As shown in FIG. 6, the light distribution characteristic of Example 1 is good in the vicinity of ± 50 °. Further, as shown in FIG. 7, the illuminance distribution is good because the half width is 800 mm or more or the minimum illuminance (relative value) within the effective area is 0.1 or more. Thereby, when it attaches to the center of a room as an indoor lighting device, it is suitable for illuminating the corner of the room.

(Example 2)
FIG. 10 is a cross-sectional view in the optical axis direction of the optical element according to the second embodiment. FIG. 11 is a diagram illustrating light distribution characteristics of the optical element according to the second example. FIG. 12 is a diagram illustrating an illuminance distribution of the optical element according to the second example. FIG. 13 is a plot of the optical element according to the second example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 14 is a plot of the optical element according to Example 2 with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 47 is a diagram showing the sag amount of the second surface in the optical element according to the second example. In the optical element according to the second embodiment, when the second surface is an aspheric surface defined by one surface shape formula and a light source having a length L = 7.7 mm is used, refer to FIG. Since (M−m) gradually increases as the angle α increases and (M−m) is the maximum (maximum) angle α1 = 60.16 deg, the equation (1) is satisfied. Further, in the range of 0 ≦ β ≦ θ, m (β) increases constant or monotonously as the angle β increases, and m (β) max / m (0) = 1.22. Fulfill. Furthermore, the angle α2 = 62.45 at which M has an inflection point and becomes a local maximum satisfies Expression (3). Further, α ′ = 75.26 deg, which satisfies the expression (4). As shown in FIG. 11, the light distribution characteristics of Example 2 are good in the vicinity of ± 50 °. Further, as shown in FIG. 12, the illuminance distribution is good because the half width is 800 mm or more or the minimum illuminance (relative value) within the effective area is 0.1 or more. In this embodiment, γ = 80.89 deg.

(Example 3)
FIG. 15 is a sectional view in the optical axis direction of the optical element according to the third embodiment. FIG. 16 is a diagram illustrating light distribution characteristics of the optical element according to the third example. FIG. 17 is a diagram showing the illuminance distribution of the optical element according to the third example. FIG. 18 is a plot of the optical element according to the third example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 19 is a plot of the optical element according to Example 3 with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 48 is a diagram illustrating the sag amount of the second surface in the optical element according to the third example. In the optical element according to the third example, the second surface is formed by connecting two surfaces (aspherical surface and spherical surface) defined by different surface shape formulas, and a light source having a length L = 7.7 mm is used. Referring to FIG. 19, (M−m) gradually increases as the angle α increases, and (M−m) is the maximum (maximum) angle α1 = 64.66 deg. ) Is satisfied. Further, in the range of 0 ≦ β ≦ θ, m (β) increases constant or monotonously as the angle β increases, and m (β) max / m (0) = 1.19. Fulfill. Further, the angle α2 = 64.66 deg at which M has an inflection point and becomes a maximum, and satisfies the expression (3). Also, α ′ = 68.67 deg, which satisfies the expression (4). As shown in FIG. 16, the light distribution characteristics of Example 3 are good in the vicinity of ± 60 °. As shown in FIG. 17, the illuminance distribution has a half width of 800 mm or less, but the minimum illuminance (relative value) within the effective area is 0.1 or more, which is favorable.

Example 4
FIG. 20 is a cross-sectional view in the optical axis direction of the optical element according to the fourth example. FIG. 21 is a diagram illustrating light distribution characteristics of the optical element according to the fourth example. FIG. 22 is a diagram showing the illuminance distribution of the optical element according to the fourth example. FIG. 23 is a plot of the optical element according to the fourth example, with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 24 is a plot of the optical element according to Example 4 with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 49 is a diagram illustrating the sag amount of the second surface in the optical element according to the fourth example. In the optical element according to the fourth example, when the second surface is an aspheric surface defined by one surface shape formula and a light source having a length L = 7.7 mm is used, refer to FIG. Since (M−m) gradually increases as the angle α increases and (M−m) is the maximum (maximum) angle α1 = 45.29 deg, the equation (1) is satisfied. Further, in the range of 0 ≦ β ≦ θ, m (β) increases constant or monotonously with the increase of the angle β, and m (β) max / m (0) = 1.21. Fulfill. Furthermore, the angle α2 at which M has an inflection point and becomes a maximum is α2 = 48.38 deg, which satisfies the expression (3). Further, α ′ = 75.02 deg, which satisfies the expression (4). Note that this embodiment has a paraxial negative power. As shown in FIG. 21, the light distribution characteristics of Example 4 are good in the vicinity of ± 30 °. Further, as shown in FIG. 22, the illuminance distribution is good because the half width is 800 mm or more or the minimum illuminance (relative value) within the effective area is 0.1 or more. In this embodiment, γ = 61.76 deg.

(Example 5)
FIG. 25 is a sectional view in the optical axis direction of the optical element according to the fifth example. FIG. 26 is a diagram illustrating light distribution characteristics of the optical element according to the fifth example. FIG. 27 is a diagram illustrating the illuminance distribution of the optical element according to the fifth example. FIG. 28 is a plot of the optical element according to the fifth example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 29 is a plot of the optical element according to Example 5 with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 50 is a diagram illustrating the sag amount of the second surface in the optical element according to the fifth example. In the optical element according to the fifth example, the second surface is formed by connecting two surfaces (aspherical surface and tapered surface) defined by different surface shape formulas, and a light source having a length L = 7.7 mm is used. When used, with reference to FIG. 29, (M−m) gradually increases as the angle α increases, and (M−m) is the maximum (maximum) angle α1 = 28.11 deg. 1) Expression is satisfied. In addition, in the range of 0 ≦ β ≦ θ, m (β) increases constant or monotonously as the angle β increases, and m (β) max / m (0) = 1.01. Fulfill. Furthermore, M is an angle α2 = 28.11 deg having an inflection point, which satisfies the expression (3). Further, α ′ = 65.92 deg, which satisfies the expression (4). As shown in FIG. 26, the light distribution characteristics of Example 5 are good in the vicinity of ± 45 °. In addition, as shown in FIG. 27, the illuminance distribution is good because the half width is 800 mm or more or the minimum illuminance (relative value) within the effective area is 0.1 or more.

(Example 6)
FIG. 30 is a sectional view in the optical axis direction of the optical element according to the sixth example. FIG. 31 is a diagram illustrating light distribution characteristics of the optical element according to the sixth example. FIG. 32 is a diagram illustrating the illuminance distribution of the optical element according to the sixth example. FIG. 33 is a plot of the optical element according to the sixth example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 34 is a plot of the optical element according to Example 6 with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 51 is a diagram illustrating the sag amount of the second surface in the optical element according to the sixth example. In the optical element according to the sixth example, when the second surface is an aspheric surface defined by one surface shape formula and a light source having a length L = 7.7 mm is used, refer to FIG. Since (M−m) gradually increases as the angle α increases and (M−m) is the maximum (maximum) angle α1 = 64.20 deg, the equation (1) is satisfied. In addition, in the range of 0 ≦ β ≦ θ, m (β) increases constant or monotonously as the angle β increases, and m (β) max / m (0) = 1.99. Fulfill. Further, α ′ = 72.39 deg, which satisfies the expression (4). Note that this embodiment has a paraxial negative power. As shown in FIG. 31, the light distribution characteristics of Example 6 are favorable in the vicinity of ± 40 °. Further, as shown in FIG. 32, the illuminance distribution is good, with a half width of 800 mm or more or a minimum illuminance (relative value) within an effective area of 0.1 or more. In this embodiment, γ = 78.96 deg.

(Comparative Example 1)
FIG. 35 is a cross-sectional view in the optical axis direction of the optical element according to the first comparative example. FIG. 36 is a diagram showing the light distribution characteristics of the optical element according to the first comparative example. FIG. 37 is a diagram showing the illuminance distribution of the optical element according to the first comparative example. FIG. 38 is a plot of the optical element according to the first comparative example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 39 is a plot of the optical element according to the first comparative example, with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 52 is a diagram showing the sag amount of the second surface in the optical element according to the first comparative example. In the optical element according to the first comparative example, when a light source having a length L = 7 mm is used, with reference to FIG. 39, an angle α1 = 80.08 deg at which (M−m) is maximum (maximum). Therefore, equation (1) is not satisfied. As shown in FIG. 36, the light distribution characteristic of Comparative Example 1 is not good because it is convex in the vicinity of 0 °. Further, as shown in FIG. 37, the illuminance distribution is not preferable because the full width at half maximum is less than 800 mm and the minimum illuminance (relative value) within the effective area is less than 0.1.

(Comparative Example 2)
FIG. 40 is a cross-sectional view in the optical axis direction of the optical element according to the second comparative example. FIG. 41 is a diagram showing the light distribution characteristics of the optical element according to the second comparative example. FIG. 42 is a diagram illustrating an illuminance distribution of the optical element according to the second comparative example. FIG. 43 is a plot of the optical element according to the second comparative example with the angle α on the horizontal axis and the lengths M and m on the vertical axis. FIG. 44 is a plot of the optical element according to the second comparative example, with the angle α on the horizontal axis and the lens thickness (M−m) on the vertical axis. FIG. 53 is a diagram showing the sag amount of the second surface in the optical element according to the second comparative example. In the optical element according to the second comparative example, when a light source having a length L = 7 mm is used, with reference to FIG. 44, the angle α1 = 14.4 deg at which (M−m) is a maximum (maximum). Therefore, equation (1) is not satisfied. As shown in FIG. 41, the light distribution characteristic of Comparative Example 2 is not good because it is convex in the vicinity of 0 °. Further, as shown in FIG. 42, the illuminance distribution is not preferable because the full width at half maximum is less than 800 mm and the minimum illuminance (relative value) within the effective area is less than 0.1.

  It should be noted that the present invention is not limited to the embodiments and examples described in the present specification, and that other embodiments and modifications are included in the embodiments and technical ideas described in the present specification. To those skilled in the art.

EP light emitting surface LM straight line Lm straight line O origin OE optical element OS light source P1 first surface P2 second surface

Claims (15)

An optical element for an illuminating device using a light source having a light emitting surface, where the optical axis of the light source is the z axis, and the light emitting surface is installed in the positive direction of the z axis, from the light emitting surface. A first surface for entering the emitted light beam, and a second surface for emitting the light beam incident from the first surface;
The position of the light emitting point on the optical axis is taken as the origin of coordinates, the length of a straight line connecting an arbitrary point on the second surface and the origin is M, and the angle formed by the straight line and the optical axis is α. , Where m is the length between the intersection of the first surface and the origin on the straight line, the lens thickness (M−m) of the first surface and the second surface is 0 ° ≦ α ≦. An optical element having an extreme value or an inflection point that is maximal within a range of 90 °, and satisfying the following formula, where α is α1.
15 ° ≦ α1 ≦ 80 ° (1)   2. The sag amount of the surface shape of the second surface is a monotonously decreasing amount as the distance from the optical axis increases when the vertex of the second surface is 0. 3. Optical elements. An angle formed by a straight line connecting an arbitrary point on the first surface and the origin and the optical axis is β, and a length of a straight line connecting an arbitrary point on the first surface and the origin is m (β). The optical element according to claim 1, wherein the following expression is satisfied, where m (β) max is a maximum value of m (β) within a range of 0 ≦ β ≦ 60 °. .
1 ≦ m (β) max / m (0) ≦ 2 (2)   4. The optical element according to claim 1, wherein both the first surface and the second surface have a rotationally symmetric surface shape with respect to the optical axis. 5.   The optical element according to claim 1, wherein there are a plurality of the light sources.   6. The optical element according to claim 1, wherein the surface shape of the second surface is defined by a plurality of surface shape formulas, and the surface shapes are connected to each other.   The optical element according to claim 1, wherein the second surface is expressed by a single surface shape formula.   The angle γ connecting the point where the inclination of the surface shape is maximum and the origin is within a range where the second surface is expressed by one surface shape formula is γ ≧ α1. 8. The optical element according to 7.   9. The optical element according to claim 1, wherein the length M has an extreme value or an inflection point that is a maximum in a range of 15 ° ≦ α ≦ 80 °.   When the lens thickness between the first surface and the second surface is (M−m), (M−m) increases as the angle α increases and is in a range of 45 ° ≦ α ≦ 80 °. The optical element according to claim 1, wherein the optical element takes a local maximum value. 11. The length M has an extreme value that becomes a maximum within a range of 0 ≦ α ≦ 90 °, and when the value of α at that time is α2, the following expression is satisfied. The optical element according to any one of the above.
45 ° ≦ α2 ≦ 80 ° (3)   The optical element according to claim 1, wherein the optical element has a negative power in a paraxial region. When the distance between the position farthest from the origin and the origin on the light emitting surface of the light source is L, an arbitrary point on the second surface at a point C away from the origin on the optical axis by the distance L. If the length of the straight line connecting the point C and the point C is N, and the angle between the straight line and the optical axis is φ, the straight line φ = 60 ° in the direction opposite to the origin as seen from the point C When the intersection point with the second surface is C ′,
13. The optical element according to claim 1, wherein an angle between a straight line connecting C ′ and the origin and an optical axis is α ′, and the following expression is satisfied.
15 ° ≦ α ≦ α ′ (4)   When the distance between the position farthest from the origin and the origin on the light emitting surface of the light source is L, a straight line passing through the point on the optical axis that is the distance L away from the origin and parallel to the optical axis Assuming that the intersection point with the first surface is B, if the length of the straight line connecting the origin and the intersection point B is mB (θ) and the angle between the straight line and the optical axis is θ, 0 ≦ β ≦ θ 14. The optical element according to claim 1, wherein m (β) increases constant or monotonously as the angle β increases in the range of.   An illumination device comprising the optical element according to claim 1.

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