JPH05281402A - Optical device - Google Patents

Abstract

PURPOSE:To reduce the aperture of a lens body and to reduce its cost without degrading the efficiency of the device while reducing its thickness. CONSTITUTION:A lens body 15 is constituted of a refractive lens part 16 provided at the central part of an optical axis K and reflector parts 17, 18. The focal positions O thereof are aligned to the positions where an LED 14 is disposed. The incident light on the refractive lens part 16 from the LED 14 is refracted by the refractive lens 16 and is converted to collimated beams of light. The incident light beams on the reflector parts 17, 18 are totally reflected by reflection surfaces 17a, 17a constituting a parabolic shape and are converted to the collimated beams of light. Since the light of the LED 14 is efficiently converted to the collimated beams of light, the aperture is reduced and the detection distance is increased. Since there is no need for a vapor deposition state of metal, the cost is reduced. Since the lens body is divided to the two reflector parts 17, 18, the thickness thereof is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for focusing and emitting light from a reference point.

[0002]

2. Description of the Related Art For example, in a multi-optical axis photoelectric switch such as an area sensor, a light projecting element and a light receiving element are provided corresponding to each optical axis, and light emitted from the light projecting element is forwardly directed. It is converted into parallel rays by the lens provided and projected toward the detection area, and the parallel rays passing through the detection area are focused on the light receiving surface as light focused by a similar lens arranged in front of the light receiving element. It is configured to be incident.

In this case, as such a lens, for example, a convex refracting lens is generally used, but in order to convert light from a point light source such as an LED (light emitting diode) into parallel rays, the point light source is a refraction lens. Need to be placed at the focal point of. However, since the point light source and the refracting lens have to be separated by the focal length in order to arrange in this way, there is a problem that the device becomes large as a whole because the thickness dimension becomes large.

Therefore, conventionally, in order to eliminate such a problem, for example, the one disclosed in Japanese Utility Model Publication No. 1-12741 has been considered. This is shown in FIG.
As also shown in FIG. 1, the convex first lens 1 is provided with a first reflecting surface 2 having a convex metal-deposited film on the central portion on the one end surface side, and a concave portion 3 is provided on the central portion on the opposite surface. The LED is formed and disposed at the focus position O, and the second reflecting surface 4 having a concave metal deposition film is formed on the outer peripheral portion thereof.

Then, the light from the LED passes through the inside of the convex lens 1 and is reflected by the first reflecting surface 2 so as to diverge, and the reflected light is reflected again by the second reflecting surface 4 and is collimated forward. It is output as a light beam. That is, the LED
The light from the LED is reflected by the first and second reflecting surfaces 2 and 4 in two steps to form parallel rays, whereby the LED and the convex lens 1
It is designed to be thinner by shortening the distance between the and.

[0006]

By the way, in such a multi-optical axis photoelectric switch, it is desired to shorten the optical axis pitch to improve the detection accuracy. For example, the detection accuracy is improved by doubling the number of optical axes by changing the optical axis pitch from the conventional 40 mm interval to half the 20 mm interval.

In this case, since two convex lenses 1 are used for each optical axis as described above, for example, in the conventional product having 24 optical axes, 48 convex lenses 1 are used, whereas the number of optical axes is 24. Is doubled to 48 optical axes, a total of 96 lenses are used.

However, the convex lens 1 in the conventional structure is very expensive as a whole because the metal deposition process for forming the two reflecting surfaces 2 and 4 costs about half of the manufacturing cost. There is a problem that it becomes a thing.

Further, in order to make the optical axis pitch short in this way, it is necessary to make the diameter of the convex lens small, but in the conventional one, when the diameter is made small, the amount of light emitted to the detection area is reduced. There is a problem in that the detection distance is shortened because it is reduced by that amount.

In this case, as shown in FIG. 12, in the normal convex lens L, since a point light source such as an LED is arranged at the position of the focal point F, the light emitted from the LED that is incident on the lens is the light. The light is in the range of the angle θa with respect to the axis K. Therefore, the light with the emission angle θa or more and the angle θ is wasted. The maximum value of the angle θa is 42 even when the lens La having the sectional shape as shown in FIG. 13 is used.
Since it is possible to obtain only up to °, there is a problem that the efficiency of emitting parallel rays becomes poor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the distance from a reference point at which a light source is arranged while reducing the cost by eliminating the metal deposition step. It is an object of the present invention to provide an optical device which can be made thin and which can transmit light with high efficiency even with a small diameter.

[0012]

An optical device according to the present invention comprises a refraction lens unit for converging light components within a predetermined angle range with respect to light from a reference point by refraction, and the reference point. And a reflector portion that focuses the light component outside the predetermined angle range by guiding the light component to the inside and totally reflecting the light component on the parabolic reflection surface.

Further, the reflector portion is divided into a plurality of angle ranges of a light component outside a predetermined angle range with respect to the light from the reference point with respect to the optical axis, and a plurality of reflections are made so as to focus each of them. The surface may be integrally formed.

[0014]

According to the optical device of the first aspect, when the point light source is arranged at the reference point, of the light from the point light source,
Light components within a predetermined angle range with respect to the optical axis are focused and emitted through the refraction lens section, and light components outside the predetermined angle range are caused by total reflection on the parabolic reflection surface of the reflector section. Since the light is focused and emitted, the light from the light source can be converted into parallel rays or diffused rays.

In this case, even when the light from the point light source of the reference point is emitted in a wide range of angles, the light outside the refracting lens is focused by the reflector, so that the conversion efficiency is improved. Therefore, the diameter can be reduced and the detection distance can be increased. Further, in the reflector portion, since the incident light is totally reflected by the reflecting surface, processing such as metal vapor deposition is unnecessary.

According to the optical device of the second aspect, the light incident on the reflector portion is divided into a plurality of angular ranges, and the light is focused and emitted by the reflecting surfaces corresponding to the respective angular ranges. As a result, the dimension in the thickness direction of the reflecting surface can be made smaller than that in the case where the reflecting surface is constituted by one reflecting surface, so that the overall thickness can be further reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to an area sensor will be described below with reference to FIGS.

FIG. 3 shows a schematic structure of the area sensor 11, which comprises a light emitter 12 and a light receiver 13.
For example, 48 optical axes (indicated by 1, 2, ... In the figure) are provided in the detection area E. An LED (light emitting diode) 1 as a light projecting element is provided in the projector 12 corresponding to each optical axis.
4 is provided (see FIG. 1), and the light receiver 13 is similarly provided with a light receiving element (not shown).

A lens body 15 as shown in FIGS. 1 and 2 is provided on the front surface of each LED 14 and the light receiving element. The lens body 15 is integrally formed by molding acrylic resin or the like, for example, and has the following configuration.

That is, as shown in cross section in FIG. 1, a refracting lens portion 16 having a hyperboloid 16a within a predetermined radius centered on the optical axis K is formed. Then, on the outer peripheral portion of the refraction lens portion 16, a first reflector portion 17 having a parabolic reflection surface 17a and a second reflector portion having a parabolic reflection surface 18b on the outer peripheral side thereof. 18 is formed.

[0021] Also. The focus of the refraction lens unit 16 and the reflecting surfaces 17 of the first reflector unit 17 and the second reflector unit 18
The focal points of a and 18a are set to coincide with each other, and the focal point position O is used as a reference point, and the light receiving surface of the LED 14 or the light receiving element is arranged.

The inner surface portion 1 of each of the reflector portions 17 and 18
7b and 18b are formed so as to be a part of a spherical surface centered on the focal position O, and are adapted to go straight without refracting light from the focal position O.

As shown in FIG. 2, the second reflector portion 18 is formed in a shape in which both side portions are cut in parallel. This is to enable compact installation depending on the shape of the case of the light projector 12 or the light receiver 13.

Next, in order to explain the operation of the above configuration, first, the principle will be described with reference to FIG. That is,
FIG. 4 shows a cross section of a lens body 20 having a refracting lens portion 16 and one reflector portion 19.

The design of the shape of the lens body 15 and the specific effect thereof in this embodiment are collectively described at the end of the description of the embodiment.

In FIG. 4, L arranged at the focus position O
Of the light from the ED 14, for example, the optical path a along the optical axis K
The light passing through goes straight through the refraction lens unit 16 and is emitted to the detection area E side as it is. Further, the light passing through the optical path b is refracted upon entering the refraction lens portion 16 and is emitted to the detection area E side as a light ray parallel to the optical axis K.

Next, the light passing through the optical path c is not refracted but is incident straight from the surface portion 19b into the reflector portion 19,
By being totally reflected by the reflecting surface 19a, it is emitted to the detection area E side as a light beam parallel to the optical axis K. Similarly, the light passing through the optical path d is also incident on the reflector portion 19, totally reflected by the reflecting surface 19a, and emitted to the detection area E side as a light ray parallel to the optical axis K.

As a result, the LED 14 from the focus position O
Is emitted to the detection area E side as parallel rays up to light having an angle of about 90 ° with respect to the optical axis K, and the light diverged by the LED 14 can be efficiently used. Further, when the light receiving element is arranged at the focal position O, the parallel light rays from the detection area E side can be efficiently collected and made incident on the light receiving surface.

As described above, in the case of the structure in which the light incident on the outside of the refracting lens portion 16 such as the optical paths c and d is covered by one reflector portion 19, the reflecting surface 19a of the reflecting surface 19a is formed. The thickness dimension D1 of the lens body 20 is relatively large due to the large light receiving area.

Therefore, the lens body 15 in the present embodiment.
Is an improvement of the above-described configuration, and is configured such that two reflector portions 17 and 18 are provided instead of the reflector portion 19.

That is, in FIG. 5, of the light from the LED 14 arranged at the focal position O, for example, the light passing through the optical path a along the optical axis K and the light passing through the optical path b are the same as those described above in the refraction lens section. It is emitted to the detection area E side as a light beam parallel to the optical axis K via 16.

Next, the light passing through the optical path c is not refracted but is incident straight from the surface portion 17b into the reflector portion 17,
By being totally reflected by the reflecting surface 17a, it is emitted to the detection area E side as a light beam parallel to the optical axis K. Then, the light passing through the optical path d is not refracted by the surface portion 18b but is reflected by the reflector portion 18
The light enters the inside so as to go straight, is totally reflected by the reflecting surface 18a, and is emitted to the detection area E side as a light beam parallel to the optical axis K.

As a result, the LED 14 from the focus position O
Light is emitted to the detection area E side as parallel rays up to a light having an angle in the range of about 90 ° with respect to the optical axis K, and the light diverged by the LED 14 can be efficiently used, and the light is focused. When the light receiving element is arranged at the position O, the light can be collected efficiently on the light receiving surface.

In this case, of the light from the LED 14 from the focal position O, the light component in the range where the emission angle is small among the light components whose emission angle with respect to the optical axis K exceeds the incident angle to the refraction lens portion 16 is selected. Reflector part 17 arranged inside
Since the light rays are converted into parallel light rays by, the thickness dimension D2 of the lens body 15 can be reduced.

According to this embodiment, the following effects can be obtained. That is, firstly, the lens body 15 is composed of the refractive lens portion 16 and the reflector portions 17 and 18, and
With respect to the light from the focus position, the light component incident on the refraction lens unit 16 is refracted and emitted as a parallel light beam, and the light components having a large emission angle with respect to the optical axis K are converted into parallel light beams by the reflectors 17 and 18. As a result, it becomes possible to utilize a wide range of light with an angle of about 90 ° with respect to the optical axis K, and even when the lens body 15 having a small diameter is constructed, the light collection efficiency is improved and the detection distance is increased. Can be longer.

Secondly, since the light components incident on the reflector portions 17 and 18 are totally reflected on the respective reflecting surfaces 17a and 18a, the metal vapor deposition step is not required in the production of the lens body 15. Therefore, the lens body 15 can be manufactured easily and inexpensively.

Thirdly, since the two reflector portions 17 and 18 are provided, the thickness dimension D2 of the lens body 15 can be further reduced, and the projector 12 or the light receiver 13 can be downsized. obtain.

FIG. 9 shows a second embodiment of the present invention. Hereinafter, parts different from the first embodiment will be described. That is, the lens body 21 is composed of the refractive lens portion 22 and the reflector portions 17 and 18. In this case, in the refractive lens portion 22, the surface 22a on the focal position O side is formed as a lens surface having a small curvature, and the surface 22b on the opposite side is formed.
Is formed as a lens surface having a large curvature.

Also according to this embodiment,
The light component passing through each of the optical paths a to d with respect to the light from the focal position O is emitted as a parallel light beam to the detection area E side as shown in the figure, and when the parallel light beam is incident from the detection area E side, Since the light is focused at the focal position O by following the opposite optical path, the same effect as that of the first embodiment can be obtained.

FIG. 10 shows a third embodiment of the present invention, which will be described below. That is, the lens body 23
Corresponds to the one in which the refraction lens portion 14a is already formed on the LED 14 side, and the lens body 23 has a cylindrical hollow portion 23a in the portion where the refraction lens portion with the optical axis K as the center is to be arranged. Is formed on the outer wall surface, and a reflector portion 19 having a reflection surface 19a as shown in FIG. 4 used in the explanation of the principle is formed.

According to this structure, of the light from the LED 14 arranged at the focal position O, the light path a or the light path b is included.
The light that passes through is refracted by the refracting lens portion 14a and is emitted as parallel rays, and the light that enters the reflector portion 19 of the lens body 23 through the optical path c or the optical path d is reflected by the reflecting surface 19
The light is totally reflected by a and is emitted to the detection area E side as a parallel light beam.

Therefore, also in the third embodiment, the LED
The light from 14 can be efficiently converted into parallel rays,
Even when the ready-made LED 14 is used, it can be easily mounted simply by mounting the lens body 23 that can be manufactured easily and inexpensively like a cap. In this case, in order to make it more efficient, the refractive lens unit 1 on the LED 14 side
It is preferable that the refractive index of 4a and the refractive index of the lens body 23 are made of a material having substantially the same value.

In each of the above embodiments, one or two reflectors are provided, but the present invention is not limited to this, and three or more reflectors may be provided.

Further, in each of the above-mentioned embodiments, the focal positions of the refracting lens portion and the reflecting portion are made to coincide with the arrangement position of the LED 14, but the present invention is not limited to this, and for example, the output portion of the LED is the lens. In the case where the virtual focal position has a function and varies depending on the emission angle of light, the refraction lens portion and the reflector portion may be formed in accordance with the respective focal positions according to the emission angle.

In each of the above embodiments, the LED 14 is arranged with the focus position O as a reference point, and the lens body 1
The light is converted into parallel rays by 5, 20, or 21 and emitted, but the invention is not limited to this. For example, by shifting the reference point from the focus position O, the light from the LED 14 is made to pass through the lens body 15, 20, or 21. May be converged into a light beam which spreads through 21 and has a divergence angle of about 15 ° or more with respect to the optical axis, and in this case also, LE
The light from D14 can be efficiently focused and emitted.

Now, next, the lens body 1 in the present embodiment.
5, the design of the hyperboloid shape of the refracting lens portion, (b) the design of the reflecting surface shape of the reflector portion, (c) confirmation of the critical angle, and (d) the conventional lens body will be described. And the four items of the comparison of the light collection efficiency of the lens body of the present embodiment.

(A) Design of hyperboloid shape of refraction lens part For example, the distance between the LED 14 and the refraction lens part 16 is 1 m.
Since the distance is about m, the focal length f = 2 (mm). Generally, when the curved surface of the lens is expressed as the shape of the cross section passing through the optical axis K, it is expressed by the following equation (1) in the xy coordinate system shown in FIG. However, c is a vertex curvature, and k is a conic constant.

[0048]

[Equation 1] Also, the radius of curvature r of the apex of the hyperboloid 16a shown in FIG.
The vertex curvature c and the conic constant k are expressed by the following equations (2), (3) and (4), respectively, using the refractive index n and the focal length f of the refractive lens unit 16.

[0049]

[Equation 2] Here, the material of the refraction lens 16 is acrylic (PMMA)
Then, since the refractive index n = 1.485 and the focal length f = 2 (mm), the curvature radius r of the apex can be calculated from the above equations (2), (3) and (4). 0.97 (mm) (5) Vertex curvature c = 1.031 (6) Cone constant k = -2.205 (7)

(B) Design of Reflection Surface Shape of Reflector Section Here, the respective focal points of the parabolic reflection surfaces 17a and 18a are made to coincide with the focal points of the hyperboloid 16a of the refraction lens section 16 described above. It is assumed that the outlines of the cross sections passing through the optical axis K of the two reflecting surfaces 17a and 18a pass through points A and B shown in FIG.

1. Design of Reflecting Surface Shape Passing Point A Since the parabolic outline of the reflecting surface 17a in the section passing through the optical axis K is generally expressed by Expression (8), it can be expressed using the coordinate system of FIG. It becomes like Formula (9).

[0052]

[Equation 3] Therefore, assuming that the coordinates (x, y) of the point A are (x, y) = (1.5, 3.39) (10), by substituting these coordinate values into the equation (9), Since the value of p1 is obtained as the root of the quadratic equation, the real root is calculated as p1 = 1.1035 (11). Accordingly, by substituting the above-mentioned value of p1 into the equation (9), the outline of the reflecting surface 17a passing through the point A is given by the equation (12).
It is expressed as.

[0053]

[Equation 4] Further, at this time, according to the equation (1) representing the curved surface of the lens, the conic constant k = −1 (13) and the radius of curvature of the apex r = 2p = 2.207 (14).

2. Designing the shape of the reflecting surface passing through the point B In the same manner as described above, if the coordinates (x, y) of the point B are (x, y) = (1, 6.2) (15), this coordinate value is Substituting into equation (9), the value of p2 is p2 = 2.64006 (16). Accordingly, by substituting the above-mentioned value of p2 into the equation (9), the outline of the reflecting surface 18a passing through the point B is given by the equation (1
It becomes like 7).

[0055]

[Equation 5] Further, at this time, according to the expression (1) expressing the curved surface of the lens, the conic constant k = −1 (18) and the radius of curvature of the apex r = 2p = 5.28 (19).

(C) Confirmation of critical angle The value of the critical angle θ as a condition under which light passes through the inside and causes total reflection on the reflecting surfaces 17a, 18a is generally expressed by the formula (20).
As shown.

[0057]

[Equation 6] As a result, the above-mentioned acrylic refractive index n = 1.485.
By substituting in equation (20), the critical angle θ = 42.33 ° (21) is obtained.

Next, since the minimum incident angles on the reflecting surfaces 17a and 18a are incident angles θ1 and θ2 with respect to the focal point O at the points A and B as shown in FIG. 7, these values are obtained. The incident angle θ1 is the sum of angles α1 and β1 divided by a straight line parallel to the y-axis direction passing through the point A (θ1 = α
1 + β1).

The above angle α1 is equal to the angle indicated by the slope m1 of the tangent line at the point A of the reflecting surface 17a. Then, y is calculated from the equation (9) representing the reflecting surface and is calculated as x
Differentiating by means of the following equations (22) and (23).

[0060]

[Equation 7] In the above equation (23), the value of p1 previously obtained (p1 = 1.
1035) and the value of the x coordinate (x = 1.5), m1 = 0.65104 is obtained. From this, the angle α1 is calculated by the equation (24),
It can be obtained as in (25).

[0061]

[Equation 8] α1 = 33.05672 ° (25) On the other hand, since the angle β1 is obtained from the coordinates of the point A, it can be obtained by the following equations (26) and (27).

[0062]

[Equation 9] β1 = 23.86833 ° (27) Therefore, the incident angle θ1 at the point A is θ1 = α1 + β1 = 56.934 ° (28). As a result, the incident angle θ1 at the point A is sufficiently larger than the critical angle θ (= 42.33 °) shown in the equation (21), so that all the light striking the reflecting surface 17a is totally reflected.

Similarly, the incident angle θ2 at the point B is calculated as follows: θ2 = α2 + β2 (29) = 40.41 ° + 9.1623 ° = 49.58 ° (30) All the light that hits will be totally reflected.

(D) Comparison of light collecting efficiency between the conventional lens body and the lens body of the present embodiment. As shown in FIG. 11, a conventional parabola lens type lens (product name NA40 of Sunkus Co.) and FIG. The light collection efficiency characteristic with that of the present embodiment shown in FIG. 8 will be obtained. That is, in the conventional device, as shown in FIG. 11, the angular range of the light effectively emitted forward from the LED arranged at the focus O through the lens body 1 is 21 with respect to the optical axis K.
The range is 17 ° from ° to 38 °. Further, in the present embodiment, as shown in FIG. 8, the angle range of the light effectively emitted is 35 ° from 0 ° to 35 °,
The range is 30 ° from 50 ° to 80 °.

Therefore, the LED 14 is actually placed at the position of the focus O.
I will try to find the value when I place. According to the inventor's verification, the conduction current IF of the LED 14 used in the trial calculation is 100 m
Assuming that the value is A and is calculated in consideration of the directional characteristics of the emitted light of the LED 14, the conventional product ... 0.8336 mW (IF = 100 mA) The present embodiment ... 3.35 mW (IF = 100 mA) is obtained. In the case of the present embodiment, a light-collecting efficiency difference of 4.02 times, that is, about 4 times that of the conventional product is obtained.

[0066]

According to the optical device of the first aspect, with respect to the light from the reference point, the refraction lens unit refracts and focuses the light component within a predetermined angle range, and the reflector unit causes the light component to have a predetermined angle. Since the light component outside the range is guided to the inside and is totally reflected by the parabolic reflecting surface, the light in a wide angle range can be focused into parallel rays or diffused rays, and Since the diameter can be reduced and the detection distance can be lengthened, and the structure in which the reflection surface of the reflector portion is totally reflected, processing such as vapor deposition is not necessary, and the excellent effect that it can be manufactured at low cost is achieved.

According to the optical device of the second aspect, in the reflector portion, the light component outside the predetermined angle range with respect to the light from the reference point outside the predetermined angle range is divided into a plurality of angle ranges. Since it is configured to integrally have a plurality of reflecting surfaces for converging each, it is possible to reduce the dimension in the thickness direction of the reflecting surface as compared with the case where it is configured by one reflecting surface. Therefore, in addition to the above effect This has the excellent effect that the overall thickness can be further reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a lens body showing a first embodiment of the present invention.

FIG. 2 is a side view and a front view of a lens body.

FIG. 3 is a schematic configuration diagram of an area sensor.

FIG. 4 is an explanatory view of the principle of the lens body, part 1

FIG. 5 is an explanatory view of the principle of the lens body, part 2

FIG. 6 is an explanatory diagram of a lens body design procedure.

FIG. 7 is an explanatory diagram of a lens body design procedure.

FIG. 8 is an explanatory diagram for comparing efficiency of lens bodies.

FIG. 9 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 11 is an explanatory diagram for efficiency comparison of a convex lens of a conventional example.

FIG. 12 is a diagram illustrating a defect of a conventional example.

FIG. 13 is a view corresponding to FIG.

[Explanation of symbols]

11 is an area sensor, 12 is a light emitter, 13 is a light receiver, 1
4 is an LED, 15, 20, 21 are lens bodies, 14a, 1
6, 22 are refraction lens parts, 16a are hyperboloids, 17, 1
Reference numerals 8 and 19 are reflector portions, and 17a, 18a and 19a are reflection surfaces.

Claims (2)

[Claims] 1. A refracting lens unit for converging a light component within a predetermined angle range with respect to the light from a reference point within a predetermined angle range by refraction, and a light from the reference point outside the predetermined angle range. An optical device comprising: a reflector portion that guides a light component inside and totally reflects the light component on a parabolic reflection surface to focus the light component. 2. The reflector portion has a plurality of reflecting surfaces that divide a light component outside a predetermined angle range with respect to the optical axis with respect to light from a reference point into a plurality of angle ranges and focus each of them. The optical device according to claim 1, wherein the optical device is integrally formed.