JP4931137B2 - Light projecting optical system capable of changing light projecting range and light projecting apparatus equipped with the same - Google Patents

Description

  The present invention relates to a light projecting optical system capable of changing a light projecting range and a light projecting apparatus including the same.

  2. Description of the Related Art Conventionally, a distance measuring device that projects a light beam onto an object range with a light projecting device and measures a distance from an information of the reflected light to an object within the object range is known. Further, there is known a scanning type light projecting device that moves a light projection range by scanning a light beam to be projected, expands an object range, and acquires a wide range of distance information.

A light projecting optical system mounted on such a light projecting device is required to efficiently collect light emitted from the light source and to make the intensity distribution of the projected light beam appropriate. For example, if the intensity distribution is too wide, information such as an object other than the object becomes a noise signal, which causes a reduction in measurement accuracy . On the other hand, if the intensity distribution is too narrow, only information on a specific part of the object can be obtained, and information in other regions is lost.

In addition to scanning the light projection range, a function for moving and fixing the light projection range to an arbitrary position may be required. As an example of utilizing such a function, there are a case where a moving state of a specific object is measured and a case where detailed information on the object is acquired.
On the other hand, a light projecting optical system and a light projecting device equipped with the same are required to be reduced in size, weight, energy saving, brightness, and the like.

In recent years, semiconductor lasers and LEDs (light-emitting diodes) have come to be used as light sources for light projection optical systems. These light sources have high output and long life.
For example, Patent Document 1 discloses a light projecting optical system using a polygon mirror as a scanning light projecting optical device. Here, the projection range is enlarged by rotating the mirror.

JP-A-8-297255

  However, since the method using the polygon mirror requires a space for arranging the mirror, it is disadvantageous for downsizing the projection optical system.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a light projecting optical system that can change the light projecting range and is advantageous for miniaturization, and a light projecting apparatus including the light projecting optical system. It is another object of the present invention to provide a light projecting optical system and a light projecting device that can improve the light collection state of the projected light beam. It is another object of the present invention to provide a light projecting optical system and a light projecting device that can reduce the influence of heat from the light source, reduce the cost, and satisfy both of them.

  In order to solve the above-described problems and achieve the object, the present invention includes a light source, a condenser lens group having a negative lateral magnification and having a positive refractive power that converts a light beam diverged from the light source into convergent light, and a collecting lens. It has a negative refractive power projecting lens group that projects the light beam from the condensing lens group so that the emitted light beam approaches a parallel light beam with respect to the light beam from the optical lens group. The projection optical system is characterized in that the projection range is changed.

The luminous flux emitted from the light source is converted into a convergent luminous flux by the condenser lens group. Then, the light beam is projected close to the parallel light beam by the light projecting lens group. At this time, since the light projecting lens group has negative refractive power, the light projecting lens group can be easily brought close to the condenser lens group , which is advantageous for downsizing the light projecting optical system. The light beam emitted from the center of the light source by moving the condensing lens group eccentrically (generally, the light source has a strong intensity in the light projecting direction) is changed by changing the light projecting direction in the direction in which the light beam is decentered. The light range can be changed.

  At this time, since the entire system has positive refracting power, the positive refracting power of the condenser lens group can be increased by setting the light projecting lens group to have negative refracting power. Further, the light beam (center of gravity) deflected by the condenser lens group is further deflected in substantially the same direction by the negative refractive power of the light projecting lens group. Therefore, as compared with the case where the entire lens system or only the light projecting lens group is moved eccentrically, the light projection range can be changed with a small amount of movement by moving the condenser lens group. Further, there is no need to arrange a mirror that rotates, which is advantageous for downsizing.

Further, the present invention is in addition to the above structure, the relationship between the condenser lens group and the projection lens group, satisfy the following condition.
−0.7 <f _P / f _N <−0.2 (1)
here,
f _P is the focal length of the condenser lens group,
f _N is the focal length of the projection lens group,
It is.

  Conditional expression (1) specifies a preferable refractive power distribution between the condenser lens group and the light projecting lens group. If the lower limit of conditional expression (1) is not reached, the negative refractive power of the light projection lens group (that is, the reciprocal of the focal length) becomes relatively strong, and the total length of the light projection optical system tends to be long. Further, as the overall length becomes longer, the size of the projection lens group tends to increase. If the upper limit of conditional expression (1) is exceeded, the negative refractive power of the light projecting lens group becomes weak, the diverging action becomes small, and the change in the light projection range with respect to the movement of the condenser lens group tends to be small.

It is more preferable that the lower limit value of conditional expression (1) is −0.65, and further −0.6.
It is more preferable that the upper limit value of conditional expression (1) is −0.25, and further −0.3.

According to a preferred aspect of the present invention, the condensing lens group is composed of one positive lens component having a positive refractive power, and the light projecting lens group has only one negative lens component having a negative refractive power. It is desirable.
However, the lens component means a lens having only two refracting surfaces in contact with air on the optical axis, that is, a surface on the side where the optical axis is incident and a surface on the side where the optical axis is emitted.

  By making the number of lens components of the condensing lens group one of the minimum units, it is further advantageous for miniaturization. Since the projection lens group as a whole has a negative refractive power, ensuring the negative refractive power of the projection lens group, simplifying the configuration, and reducing the weight by making the total number of lens components having negative refractive power one. It is advantageous for compatibility.

According to a preferred aspect of the present invention, it is desirable that the positive lens component of the condenser lens group has a biconvex shape that satisfies the following conditional expression.
−3.0 <β _P <−0.7 (A)
-0.2 <SF _P <0.2 (B)
However,
β _P is the lateral magnification of the positive lens component of the condenser lens group,
SF _P is the shape factor of the positive lens component of the condenser lens group,
The paraxial radius of curvature of the entrance surface r _Pi, SF _P = when the paraxial curvature radius of the exit side were a _{r Po (r Pi + r Po} ) / (r Pi -r Po)
Defined by

  Conditional expressions (A) and (B) specify the preferred lateral magnification and shape of the positive lens component of the condenser lens group. Conditional expression (A) specifies a preferable lateral magnification of the condenser lens group. If the lower limit of conditional expression (A) is not reached, the distance between the condensing lens group and the light projecting lens group tends to be long, and the light flux in the light projecting lens group becomes thin. For this reason, the function of canceling the spherical aberration of the condensing lens group by the light projecting lens group becomes small. Further, the incident position of the light beam in the light projecting lens group when the condenser lens group is decentered is easily separated from the optical axis, and the change in the light projection angle is increased. Therefore, it is necessary to increase the accuracy of controlling the projection angle. If the upper limit of conditional expression (A) is exceeded, the condensing lens group tends to be separated from the light source, the total length tends to be long, and the size tends to increase.

  Conditional expression (B) specifies a preferable shape of the biconvex positive lens component. If the lower limit of conditional expression (B) is not reached, the curvature of the surface on the incident side increases, and aberrations on this surface tend to occur. If the upper limit of conditional expression (B) is exceeded, the curvature of the exit-side surface increases, and aberrations on this surface tend to occur.

It is more preferable that the lower limit value of the conditional expression (A) is −2.5, and further −2.0.
It is more preferable that the upper limit value of conditional expression (A) is −1.0, and further −1.2.
It is more preferable that the lower limit value of conditional expression (B) is set to -0.15, more preferably -0.1.
It is more preferable that the upper limit value of conditional expression (B) is 0.1, further 0.

  According to a preferred aspect of the present invention, it is desirable that all the lenses in the light projecting lens group are single lenses made of plastic.

  Thereby, it becomes easy to hold down manufacturing cost by using a plastic. Further, since the light projecting lens group has a smaller refractive power than the condenser lens group, the influence of the refractive index change due to heat can be suppressed even if plastic is used.

  According to a preferred aspect of the present invention, it is desirable that the light projecting lens group has a toric refractive surface.

  As a result, the refractive power can be changed depending on the direction of the projected light beam (for example, the horizontal direction and the vertical direction), so that the projection angle of the projected light beam can be easily adjusted. For example, the focal length can be changed in each direction of the lens system (for example, the horizontal direction and the vertical direction) by the toric surface. For this reason, it is easy to adjust the emission angle in the desired direction within the direction parallel to the light beam emitted from the light source in a state in which the light beam in one direction is secured.

  Further, when the light emitting portion of the light source has a non-rotationally symmetric shape, the magnification of the light projecting optical system can be made non-rotationally symmetric corresponding to the shape, and the direction of the projected light beam, for example, in the horizontal and vertical directions It becomes possible to improve the accuracy of light collection in each.

  Furthermore, if the light projection range is changed by the movement of the condenser lens group, the change in the light beam passage position in the light projection lens group becomes large. Therefore, with the above-described configuration, it is easy to adjust the luminous flux to be projected even when the projection range is changed. A lens having a toric surface is easy to manufacture if it is made of plastic.

  Further, according to a preferable aspect of the present invention, it is desirable that the light projecting lens group is composed of one negative lens component having a negative refractive power. Thereby, it becomes advantageous to cost reduction by making the structure of a light projection lens group into the structure of one lens component.

According to a preferred aspect of the present invention, it is desirable that the shape of the negative lens component of the light projecting lens group is a biconcave shape that satisfies the following conditional expression.
-0.9 <SF _Nn <-0.3 (C)
−1.6 <r _Nni / D _PN <−0.7 (D)
However,
SF _Nn is the shape factor of the negative lens component of the projection lens group.
SF _Nn = (r _Nni + r _Nno ) / (r _Nni -r _Nno ) where r _Nni is the paraxial radius of curvature of the incident side surface and r _{Nno is the paraxial} radius of curvature of the exit side _surface
Defined in
r _Nni is the paraxial radius of curvature of the incident side surface of the negative lens component of the projection lens group,
D _PN is the distance on the optical axis between the condenser lens group and the projection lens group,
It is.

  Conditional expressions (C) and (D) specify a more preferable relationship between the shape and arrangement of the negative lens component when the projection lens group is configured with one negative lens component. If the lower limit of conditional expression (C) is not reached, the curvature of the exit side surface of the negative lens component becomes smaller (and becomes more positive), and tends to be on the negative lens component exit side with respect to the principal point of the negative lens component. Becomes easier to enlarge. Further, the power burden on the incident side surface is increased, and the influence of the aberration generated on the negative lens component incident side surface is increased. On the other hand, if the upper limit of conditional expression (C) is exceeded, the curvature of the incident side surface of the negative lens component is small, the curvature of the exit side surface is large, and aberrations occurring on the exit side surface of the negative lens component when the condenser lens group is decentered. The impact will increase.

  If the lower limit of conditional expression (D) is not reached, the curvature of the incident side surface of the negative lens component becomes small, the incident angle to the negative lens component when the condensing lens group is decentered becomes large, and aberration tends to occur. On the other hand, if the upper limit of conditional expression (D) is exceeded, the curvature of the entrance surface of the negative lens component becomes too large, and aberrations on this surface tend to occur. Alternatively, the negative lens component is separated from the condenser lens group, and the projection optical system is likely to be enlarged.

It is more preferable that the lower limit value of conditional expression (C) is −0.8, and further −0.7.
It is more preferable that the upper limit value of conditional expression (C) is −0.4, and further −0.5.
It is more preferable that the lower limit value of conditional expression (D) is −1.5, and further −1.4.
It is more preferable that the upper limit value of conditional expression (D) is −0.9, and further −1.0.

  Further, according to a preferable aspect of the present invention, it is desirable that the light projecting lens group is composed of two lens components in order from the light source side: a negative lens component and a positive lens component having a positive refractive power.

  The structure of the projection optical system is a positive lens component, a negative lens component, and a positive lens component, which is advantageous for correcting aberrations. That is, the entire positive refracting power is shared by the two positive lens components of the condensing lens group and the light projecting lens group, and the negative lens component is arranged between them, so that it becomes easy to cancel the remaining spherical aberration.

According to a preferred aspect of the present invention, it is desirable that the relationship between the negative lens component and the positive lens component of the projection lens group satisfies the following conditional expression.
−0.4 <f _Nn / f _Np <−0.1 (2)
here,
f _Nn is the focal length of the negative lens component in the projection lens group,
f _Np is the focal length of the positive lens component in the projection lens group,
It is.

  Conditional expression (2) specifies a preferable refractive power distribution between the negative lens component and the positive lens component of the projection lens group. If the lower limit of conditional expression (2) is not reached, the diverging action of the negative lens component is reduced, and the amount of movement of the condenser lens group to be moved is likely to increase. On the other hand, if the upper limit of conditional expression (2) is exceeded, the refractive power of the negative lens component becomes strong, and the influence on aberrations when the condenser lens group is moved increases. In addition, when the negative lens component is a plastic single lens, the influence of temperature change characteristics is likely to occur.

It is more preferable that the lower limit value of conditional expression (2) be -0.3, and further -0.2.
It is more preferable that the upper limit value of conditional expression (2) is −0.13, and further −0.16.

According to a preferable aspect of the present invention, it is desirable that the shape of the negative lens component of the light projecting lens group is a biconcave shape that satisfies the following conditions.
-0.9 <SF _Nn <0.0 (E)
−1.0 <r _Nni / D _PN <−0.2 (F)
However,
SF _Nn is the shape factor of the negative lens component of the projection lens group.
SF _Nn = (r _Nni + r _Nno ) / (r _Nni -r _Nno ) where r _Nni is the paraxial radius of curvature of the incident side surface and r _{Nno is the paraxial} radius of curvature of the exit side _surface
Defined in
r _Nni is the paraxial radius of curvature of the incident side surface of the negative lens component of the projection lens group,
D _PN is the distance on the optical axis between the condenser lens group and the projection lens group,
It is.

  Conditional expressions (E) and (F) specify a more preferable relationship between the shape and arrangement of the negative lens component when the projection lens group is configured as described above. If the lower limit of conditional expression (E) is not reached, the curvature of the incident side surface of the negative lens component is large, the curvature of the exit side surface is small, and the influence of aberration generated on the incident side surface of the negative lens component when the condenser lens group is decentered. Becomes larger. On the other hand, when the upper limit of conditional expression (E) is exceeded, the curvature of the incident side surface of the negative lens component is small, the curvature of the exit side surface is large, and aberrations occurring on the exit side surface of the negative lens component when the condenser lens group is decentered. The impact will increase.

  If the lower limit of the conditional expression (F) is not reached, the curvature of the incident side surface of the negative lens component becomes too small, the incident angle to the negative lens component when the condensing lens group is decentered becomes large, and aberration tends to occur. On the other hand, if the upper limit of conditional expression (F) is exceeded, the curvature of the entrance surface of the negative lens component becomes too large, and the incident angle to the negative lens component when the condensing lens group is decentered becomes large and aberrations are likely to occur. Become. Alternatively, the negative lens component moves away from the condensing lens group, and the function of canceling out aberrations occurring in the condensing lens group with the negative lens component is likely to deteriorate.

It is more preferable that the lower limit value of conditional expression (E) is −0.7, and further −0.5.
It is more preferable that the upper limit value of conditional expression (E) be -0.2, and further -0.4.
It is more preferable that the lower limit value of conditional expression (F) be −0.8, and further −0.6.
It is more preferable that the upper limit value of conditional expression (F) is −0.3, and further −0.4.

Moreover, it is preferable to set it as the following structures. The shape of the positive lens component of the light projecting lens group is preferably a meniscus shape that satisfies the following conditions.
5.0 <SF _Np <20.0 (G)
−5.0 <r _Npi / D _np <−1.0 (H)
However,
SF _Np is the shape factor of the positive lens component of the projection lens group.
SF _Np = (r _Npi + r _Npo ) / (r _Npi −r _Npo ) where r _{Npi is} the paraxial radius of curvature of the incident side and r _Npo is the radius of paraxial _{curvature of} the exit side.
Defined in
r _Npi is the paraxial radius of curvature of the incident side of the positive lens component of the projection lens group,
D _np is the distance on the optical axis between the negative lens component and the positive lens component in the projection lens group,
It is.

  As a result, the positive lens component has a concave meniscus shape on the incident side and a convex surface on the exit side, so that it is easy to suppress the incident angle to the positive lens when the condenser lens group is decentered. In addition, the size can be easily reduced by adjusting the main point.

  Conditional expressions (G) and (H) specify the relationship between the shape and arrangement of a more preferable positive lens component in consideration of the influence of aberration and size when the projection lens group is configured as described above. It is. If the lower limit of conditional expression (G) is not reached, the curvature of both the incident side surface and the exit side surface of the positive lens component becomes small, and the influence of the aberration generated in the positive lens component when the condensing lens group is decentered becomes large. It is also disadvantageous for downsizing. On the other hand, if the upper limit of conditional expression (G) is exceeded, the curvature increases on both the incident side and exit side of the positive lens component, and the influence of aberration generated on the exit side of the negative lens component increases when the condenser lens group is decentered. .

  If the lower limit of conditional expression (H) is not reached, the curvature of the incident side surface of the positive lens component becomes too small, and the incident angle to the positive lens component when the image forming lens group is decentered becomes large and aberrations are likely to occur. On the other hand, if the upper limit of the conditional expression (H) is exceeded, the curvature of the entrance surface of the positive lens component becomes too large, and the influence of aberration generated on the exit side surface of the negative lens component when the condenser lens group is decentered becomes large. . Alternatively, the positive lens component is separated from the negative lens component, and the projection optical system is easily increased in size.

It is more preferable that the lower limit value of conditional expression (G) is 7.0, and further 9.0.
It is more preferable that the upper limit value of conditional expression (G) is 16.0, further 13.0.
It is more preferable that the lower limit value of conditional expression (H) is −3.0, more preferably −2.0.
It is more preferable that the upper limit value of conditional expression (H) is −1.2, and further −1.4.

  According to a preferred aspect of the present invention, it is desirable that the positive lens component and the negative lens component of the light projecting lens group be a single lens made of plastic.

  By making both the negative lens component and the positive lens component in the light projecting lens unit a single lens made of plastic, the power change resulting from the temperature dependence of the refractive index of the plastic has an opposite characteristic. Therefore, it is possible to suppress a decrease in optical performance due to a temperature change while reducing the cost by using plastic.

According to a preferred aspect of the present invention, it is desirable that the positive lens component of the projection lens group has a toric refracting surface.

  Since the refractive power can be changed depending on the direction of the projected light beam (for example, the horizontal direction and the vertical direction), it is easy to adjust the projection angle of the projected light beam. Further, in the direction in which the light projection range is changed by the movement of the condensing lens group, a change in the light beam passage position in the light projection lens group becomes large. Therefore, with the above-described configuration, it is easy to adjust the luminous flux to be projected even when the projection range is changed. A lens having a toric surface can be easily manufactured if it is made of plastic.

  According to a preferred aspect of the present invention, it is desirable that the toric surface is an aspherical surface whose curvature changes as the distance from the optical axis of the lens increases at least in the direction of eccentric movement.

  The passing position of the center of gravity of the light beam on the toric surface in the light projecting lens group varies depending on the position where the condenser lens group moves. Therefore, by changing the curvature in the direction of eccentric movement, it becomes easy to adjust the bundle of light beams and the projection angle.

  According to a preferred aspect of the present invention, it is desirable that the positive lens component of the condenser lens group has a convex aspheric surface whose absolute value of curvature decreases as the distance from the optical axis of the lens increases. Thereby, it becomes easy to suppress the collapse of the condensing state when the condensing lens group is moved eccentrically.

  According to a preferred aspect of the present invention, it is desirable that the positive lens component of the condenser lens group is made of glass. As a result, the power of the condenser lens group is increased. For this reason, it becomes easy to suppress the change of the optical performance by a temperature and humidity change by comprising with glass.

  According to a preferred aspect of the present invention, it is desirable that the positive lens component of the condenser lens group is a single lens. Thereby, the cost can be reduced by setting the number of constituent lenses of the condensing lens group to one single minimum lens.

  Further, it is more preferable that the above conditional expressions are satisfied not only in the direction of eccentric movement but also in the direction perpendicular to the direction of eccentric movement.

According to a preferred aspect of the present invention, it is desirable that the toric surface is a convex surface that satisfies the following conditional expression.
10 <1 / (RT _max / RT _min −1) <300 (I)
However,
RT _max is the maximum value of the absolute value of the paraxial radius of curvature of the toric surface that varies depending on the direction,
RT _min is the minimum value of the absolute values of the paraxial radius of curvature of the toric surface that varies depending on the direction,
It is.

  Conditional expression (I) defines an appropriate shape of the toric surface. If the lower limit of conditional expression (I) is not reached, the difference in paraxial radius of curvature increases, making it difficult to collect the projected light flux. If the upper limit of conditional expression (I) is exceeded, the merit of using a toric surface is reduced.

It is more preferable that the lower limit value of conditional expression (I) is 30 and further 50.
It is more preferable that the upper limit value of conditional expression (I) is 200, further 100.

According to a preferred aspect of the present invention, it is desirable that the combined lateral magnification of the lateral magnification of the condenser lens group and the lateral magnification of the light projecting lens group satisfies the following conditional expression.
−0.02 <β ⁻¹ _min <0.05 (J)
−0.02 <β ⁻¹ _max <0.10 (K)
However,
β ^-1 _min is the minimum value of the reciprocal of the combined lateral magnification (total system lateral magnification) in any direction intersecting the optical axis,
β ⁻¹ _max is the maximum value of the reciprocal of the combined lateral magnification (total system lateral magnification) in any direction intersecting the optical axis,
It is.

  If the upper limit or the lower limit of each conditional expression (J) or (K) is exceeded, the spread of the projected light beam increases, and the intensity of the projected light beam decreases.

It is more preferable that the lower limit value of conditional expression (J) is 0.0, further 0.002.
It is more preferable that the upper limit value of conditional expression (J) is 0.03, further 0.01.
More preferably, the lower limit value of conditional expression (K) is 0.0, more preferably 0.002.
It is more preferable that the upper limit value of conditional expression (K) is 0.07, further 0.05.

  According to a preferred aspect of the present invention, it is desirable that the light source includes at least one of a plurality of point light sources, a linear light source, and a planar light source.

  Moreover, according to the preferable aspect of this invention, it is desirable that the light emission site | part of a light source is linear or a rectangle.

  Alternatively, the light source is a light emitting diode or a semiconductor laser, and the light emitting portion of the light source is preferably rectangular or linear.

  Thereby, the amount of light emission can be increased as compared with a single point light source. In particular, this configuration can be easily configured when a semiconductor laser or LED is used as a light source.

  In addition, according to the present invention, the above-described light projecting optical system and a light receiving member that acquires position information of the target object based on the light beam projected by the light projecting optical system reflected by the target object are provided. Thus, it is possible to provide a light projecting device. Thereby, since the size of the light projecting optical system can be reduced, it is advantageous for miniaturization of the light projecting device that obtains the position information of the object.

  It is more preferable that each of the above-described inventions satisfies a plurality at the same time. For each conditional expression, only the upper limit value or lower limit value of the numerical range of the more limited conditional expression may be limited. Further, the above-described configurations may be arbitrarily combined.

ADVANTAGE OF THE INVENTION According to this invention, the light projection optical system which can change a light projection range, and is advantageous to size reduction, and a light projection apparatus provided with the same can be provided.
In addition, it is possible to provide a light projecting optical system and a light projecting device that can improve the light collection state of the projected light beam.
Furthermore, it is possible to provide a light projecting optical system and a light projecting device that can reduce the influence of heat from the light source or reduce the cost, and satisfy both of them.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 shows a paraxial conceptual diagram of a light projecting optical system according to an embodiment of the present invention. As shown in FIG. 1, the light projecting optical system includes a light source 201, a condenser lens group 202, and a light projecting lens group 203. The condenser lens group 202 and the light projecting lens group 203 are arranged in order from the light source 201.

  The condensing lens group 202 has a negative lateral magnification, and converts the luminous flux emitted from the light source 201 into convergent light. The light projecting lens group 203 projects the light flux from the condenser lens group 202 so that the emitted light flux approaches the parallel light flux with respect to the light flux from the condenser lens group 202.

  The light source 201 and the condenser lens group 202 are arranged in a positional relationship in which the lateral magnification of the light source image 211 by the condenser lens group 202 is a negative value. At this time, when the light source image 211 by the condensing lens group 202 coincides with the focal point of the light projecting lens group 203, the light beam from the center of the light source 201 becomes a parallel light beam.

  On the other hand, a parallel light beam emitted from the light source 201 having a length is converted into a light beam diverging in a direction having the length by the light projecting lens group 203. Therefore, when the light source 201 has a length or area, or has a plurality of point light sources, and the projection direction has a strong intensity in the direction of the optical axis 221 in FIG. 1, the position of the focus of the light projection lens group 203 is the light source image. If it is configured so that it is positioned slightly closer to the condenser lens side than the 211 position, the luminous flux emitted from the light source 201 as a whole becomes a projected luminous flux having a strong intensity in substantially the same direction while slightly diverging. A light beam close to a parallel light beam can be projected.

  In FIG. 1, a light beam 241 emitted from the center of the light source in the direction of the optical axis 203a of the light projecting lens coincides with the optical axis of the condenser lens group 202, and thus proceeds linearly without being bent. Among the light beams emitted from the center of the light source, this light ray and the light rays in the vicinity have high intensity. For this reason, the light ray 241 is set as the principal ray. Light rays 242 and 243 emitted in the peripheral direction from the center of the light source are directed to the surface of the light source image 211 by the action of the condensing lens group 202 and are substantially parallel to the light ray 241 by the action of the light projecting lens group 203. That is, in a paraxial manner (if there is no lens aberration), the light beam emitted from one point of the light source is emitted from the light projecting lens group 203 as a substantially parallel light beam.

  Next, an operation for changing the light projection range in the light projection optical system of the present embodiment will be described. FIG. 1 is a diagram illustrating a state in which the central light beam 241 is projected so as to travel straight, and FIG. It is a figure which shows the state made to do.

  In FIG. 1, since the optical axis 202 a of the condenser lens group 202 is located on the orbit of the central ray of the light flux, the light flux is not deflected by the condenser lens group 202. On the other hand, in FIG. 2, the optical axis 202a of the condensing lens group 202 is off the trajectory of the central ray of the light beam. For this reason, the light beam is deflected by the action of the positive refractive power of the condenser lens group 202. The light is further deflected in the same direction under the action of the negative refractive power of the light projecting lens group.

  The degree to which the light beam is deflected by the condensing lens group 202 depends on the amount by which the optical axis 202a of the condensing lens group 202 is off the orbit of the central ray of the light beam. Therefore, by controlling the eccentric position of the condensing lens group 202, the refraction action of the condensing lens group 202 with respect to the central ray 241 can be changed and the light projecting direction can be arbitrarily changed. That is, the projection range can be changed by moving the condenser lens group 202 eccentrically.

  In this way, the method of decentering the condenser lens group 202 can make a space required for arrangement and movement smaller than a method using a known polygon mirror. The decentering method of the condenser lens group 202 may be a method of shifting in a direction perpendicular to the optical axis 203a of the light projecting lens group 203 or a method of tilting in a circular arc shape. In the former, the drive system can be easily configured, and in the latter, the disturbance of the luminous flux can be reduced.

  In the light projecting optical system according to the present embodiment, the light source 201 includes, for example, at least one of a plurality of point light sources, a linear light source, and a planar light source. The light emitting part of the light source 201 is preferably linear or rectangular. Thereby, the emitted light amount can be increased compared with the point light source. The light source 201 is composed of, for example, a light emitting diode or a semiconductor laser.

  Specific examples of the light projecting optical system of the present invention are shown below. The embodiment shown below assumes an in-vehicle distance measuring device. In these embodiments, the light source 201 is a laser light source having a wavelength of 905 nm. A linear light source of about 0.4 mm is assumed in the vertical direction perpendicular to the road surface. In the optical path diagrams of the respective embodiments, they are exaggerated and drawn so that the longitudinal direction of the line light source can be seen.

  4A shows the light distribution characteristic in the horizontal direction of the light source 201, and FIG. 4B shows the light distribution characteristic in the vertical direction. As shown in (a) and (b), the divergence angle of the light source 201 is about 20 ° in the vertical direction (longitudinal direction of the light source) and in a direction horizontal to the road surface (perpendicular to the longitudinal direction of the light source). About 40 ° is assumed. The projection range is assumed to be a range having a solid angle of about 1.2 ° in the vertical direction (longitudinal direction of the light source) and about 0.1 ° in the horizontal direction (perpendicular to the longitudinal direction of the light source). Yes. The angle of the light projecting range is minimized in the horizontal direction with respect to the road surface and maximized in the vertical direction.

  FIG. 5A shows a cross-sectional configuration in the vertical direction (longitudinal direction of the light source) of the light projecting optical system of Example 1, and FIG. 5B shows a cross-sectional configuration in the horizontal direction. In the light projecting optical system of Example 1, as shown in FIGS. 4A and 4B, the condensing lens group 202 is composed of one biconvex positive lens 202A, and the light projecting lens group 203 is composed of one both. It is composed of a concave negative lens 203A.

  One biconvex lens 202A constituting the condenser lens group 202 is made of, for example, plastic, and both surfaces are aspherical surfaces having a rotationally symmetric shape with respect to the optical axis of the condenser lens group. The shape is such that the curvature decreases as the distance from the optical axis increases.

  The biconcave lens 203A constituting the light projecting lens group 203 is made of plastic, and both surfaces are formed of spherical surfaces that are rotationally symmetric with respect to the optical axis of the light projecting lens group.

  The convex surfaces on both sides of the biconvex lens 202A of the condensing lens group 202 are the above-mentioned aspherical surfaces, so that the condensing property is improved and the uniformity of the intensity distribution is improved. Further, the light projection range can be moved by decentering the condenser lens group 202 in the horizontal direction and the vertical direction.

  Since each lens in the condensing lens group 202 and the light projecting lens group 203 is a single plastic lens, it is advantageous in terms of light weight and low cost. Moreover, it is easy to form an aspherical surface. In the first embodiment, all the lenses are made of plastic. However, the present invention is not limited to this, and all or some lenses are made of a glass material, so that changes in characteristics can be reduced when used in an environment where the temperature and humidity change ranges are even greater.

  Table 1 shows lens data of the light projecting optical system of Example 1. Since the shape of the lens portion of Example 1 is rotationally symmetric with respect to the optical axis, the lens data is the same in both the horizontal direction and the vertical direction.

(Table 1)
Lens data unit of Example 1 mm

Surface data surface number rd nd
Object 25.57212
1 14.89309 (Aspherical surface) 6.60955 1.51561
2 -17.90081 (Aspherical) 10.74075
3 -19.94251 (spherical surface) 4.00568 1.51561
4 67.33842 (spherical surface)

Aspheric data first surface
K = -1.6500, A4 = 8.0777E-6, A6 = -1.3275E-7, A8 = 2.4656E-9
Second side
K = -4.8098, A4 = -3.4157E-5, A6 = 1.9112E-7, A8 = 1.2081E-9

  In all Examples below Table 1, r is the paraxial radius of curvature of each lens surface, d is the distance from the light source 201 to the incident side lens surface of the condenser lens group 202, d is the distance between the lens surfaces, and nd is This is the refractive index of each lens in the use wavelength (905 nm) under the assumed use environment (40 degrees Celsius). The aspherical shape is represented by the following equation, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis on the cross section.

^{x = (y 2 / r)} / [1+ {1- (K + 1) (y / r) 2} 1/2] + A4y 4 + A6y 6 + A8y 8
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A4, A6, and A8 are fourth-order, sixth-order, and eighth-order aspheric coefficients, respectively. In the aspheric coefficient, “E−n” (n is an integer) indicates “10 ⁻ⁿ ”.

  FIG. 6A shows the intensity distribution in the vertical direction of the projected light beam by the light projecting optical system of Example 1, and FIG. 6B shows the intensity distribution in the horizontal direction. By moving the condenser lens group 202 eccentrically (shifted or tilted) in the horizontal direction of the road surface (direction perpendicular to the longitudinal direction of the light source), the light projection range on the object side is moved in the horizontal direction and fixed thereafter. Or scan. Eccentric movement is also possible in the vertical and diagonal directions.

  FIG. 7A shows a cross-sectional configuration in the vertical direction (longitudinal direction of the light source) of the light projecting optical system of Example 2, and FIG. 7B shows a cross-sectional configuration in the horizontal direction.

  In the light projecting optical system of Example 2, as shown in FIGS. 7A and 7B, the condensing lens group 202 is composed of one biconvex positive lens 202B, and the light projecting lens group 203 is both. The lens includes a concave negative lens 203B and a meniscus toric positive lens 203C convex on the light projecting side. The projection lens group 203 as a whole has a negative refractive power. The biconvex positive lens 202B constituting the condenser lens group 202 is made of glass, and both surfaces are aspherical surfaces having a rotationally symmetric shape with respect to the optical axis of the condenser lens group. The curvature decreases with increasing distance from the axis.

  The biconcave negative lens 203B in the light projecting lens group 203 is made of plastic, and both surfaces are formed of spherical surfaces that are rotationally symmetric with respect to the optical axis of the light projecting lens group. The toric positive lens 203C in the light projecting lens group 203 is made of plastic, the light source side surface is a spherical surface that is rotationally symmetric with respect to the optical axis, and the light projecting side surface is a toric surface.

  The toric surface is such that the absolute value (minimum value) of the paraxial radius of curvature in the horizontal direction is smaller than the absolute value (maximum value) of the paraxial radius of curvature in the vertical direction, and the non-rotational symmetry of the light source The condensing state is adjusted depending on the direction in consideration of the shape. Also, the cross-sectional shape in the vertical direction including the optical axis is arc-shaped, and the cross-section in the horizontal direction including the optical axis is non-arc-shaped, so that the state of the light beam is improved when the projection angle of the light beam is changed. ing.

  The toric surface is a non-rotationally symmetric toric aspheric surface whose shape is smoothly changed between the vertical direction and the horizontal direction, and the longitudinal cross section and the horizontal cross section are symmetrical surfaces of the toric surface.

  The convex surfaces on both sides of the biconvex lens 202B of the condensing lens group 202 are the above-mentioned aspherical surfaces, so that the light condensing property is improved and the uniformity of the intensity distribution is improved. The light projection range can be moved by decentering the condenser lens group 202 in the horizontal and vertical directions. Further, since the lenses in the condenser lens group are made of glass, the influence of changes in temperature and humidity is suppressed. In addition, since both the negative lens and the positive lens of the light projecting lens group are made of plastic, it is possible to cancel the influence of the change in refractive index due to the change in temperature and humidity.

  In addition, the toric surface is easily formed by molding the toric positive lens 203C from plastic. It should be noted that the use of glass material for all lenses or some lenses of the projection optical system can reduce the change in characteristics when used in an environment where the temperature and humidity change ranges are large.

  Tables 2 and 3 show lens data of the light projecting optical system of Example 2. Table 2 shows the lens data in the longitudinal section, and Table 3 shows the lens data in the horizontal section. The definition of the lens data is the same as that in the first embodiment.

(Table 2)
Lens data of Example 2 (vertical cross section)

Surface data surface number rd nd
Object 15.182
1 9.9629 (Aspherical surface) 5.500 1.57386
2 -11.4662 (Aspherical) 2.371
3 -11.2797 (spherical surface) 2.000 1.51561
4 30.5718 (spherical surface) 9.3471
5 -15.7645 (Spherical surface) 6.000 1.51561
6 -13.3703 (toric aspherical surface)

Aspherical data of Example 2 (vertical section)
First side
K = 0, A4 = -1.5645E-4, A6 = 2.9012E-7, A8 = -6.6088E-9
Second side
K = 0, A4 = 2.7844E-4, A6 = -1.5228E-7, A8 = 7.1970E-9
6th page
K = 0, A4 = 0, A6 = 0, A8 = 0

(Table 3)
Lens data for Example 2 (horizontal section)

Surface data surface number rd nd
Object 15.182
1 9.9629 (Aspherical surface) 5.500 1.57386
2 -11.4662 (Aspherical) 2.371
3 -11.2797 (spherical surface) 2.000 1.51561
4 30.5718 (spherical surface) 9.3471
5 -15.7645 (Spherical surface) 6.000 1.51561
6 -13.1668 (Toric aspherical surface)

Aspherical data of Example 2 (horizontal section)
First side
K = 0, A4 = -1.5645E-4, A6 = 2.9012E-7, A8 = -6.6088E-9
Second side
K = 0, A4 = 2.7844E-4, A6 = -1.5228E-7, A8 = 7.1970E-9
6th page
K = 0, A4 = 7.3878E-6, A6 = -9.3931E-10, A8 = 4.6929E-10

FIG. 8A shows the intensity distribution in the vertical direction of the projected light beam by the light projecting optical system of Example 2, and FIG. 8B shows the intensity distribution in the horizontal direction.

  The entire condensing lens group 202 is decentered (shifted or tilted) in the horizontal direction of the road surface (the direction perpendicular to the longitudinal direction of the light source), thereby moving the light projection range on the object side in the horizontal direction and fixing it thereafter. Or scan. As in the first embodiment, it can be moved eccentrically in the longitudinal direction and the oblique direction.

  Further, in each embodiment, the reflecting surface may be disposed here by utilizing the lens space of the light projecting optical system to further reduce the size of the apparatus.

Table 4 shows values corresponding to the conditional expressions of the respective examples.

(Table 4)
Example 1 Example 2
Conditional expression Horizontal direction Vertical direction Horizontal direction Vertical direction
(1) f _P / f _N -0.57613 Same as left -0.35529 -0.36825
(A) β _P -1.57156 Same as left -1.52377 Same as left
(B) SF _P -0.09172 Same as left -0.07015 Same as left
(C), (E) SF _Nn -0.54303 Same as left -0.46097 Same as left
(D), (F) r _Nni / D _PN -1.85671 Same as left -4.75771 Same as left
(2) No f _Nn / f _Np None -0.1812 -0.17061
(G) SF _Np None None 11.13745 12.16873
(H) r _Npi / D _np None None -1.68657 Same as on the left
(I) 1 / (RT _max / RT _min -1) None 64.70172
(J) β ^-1 _min 0.005743 0.002951
(K) β ^-1 _max 0.005743 0.014341

(Light projector)
Hereinafter, with reference to FIG. 3, a light projecting device including the light projecting optical system according to the first embodiment will be described. FIG. 3 is a diagram for explaining a usage pattern of the light projecting device including the light projecting optical system according to the first embodiment. Of course, the second embodiment may be replaced.

  The light projecting optical system of this light projecting device includes a laser diode (light emitting diode or semiconductor laser) 132 as a light source. The condensing lens group 202 includes a biconvex lens 202A, and converts the light flux from the light source of the laser diode into convergent light. Then, the light beam is transmitted through the light projecting lens group 203 including the biconcave lens 203A, and the light beam is projected in the direction in which the object 158 exists.

  The condenser lens group 202 is fixed to the holder 12. The position of the holder 12 is maintained by eight wire springs 48A to 48H (only two are shown in the figure), and the holder 12 is configured to be shiftable in the direction of the arrow indicated by 152 in the figure. It can also move in the direction perpendicular to the page. For the shift movement, a linear motor or an ultrasonic motor (not shown) can be used.

  In the horizontal direction, the chief ray is changed to a range indicated by an arrow 154 in the figure by the shift movement of the condenser lens group 202. Then, the light beam having the principal ray 156 toward the object 158 is reflected by the object 158 and becomes a light beam having the principal ray 160.

  A light receiving lens 162 is disposed at a position away from the optical axis of the light projecting lens group 203 by a certain distance, and a photodetector 164 as a light receiving member is disposed on the image side of the light receiving lens 162.

  The light beam reflected by the object 158 passes through the light receiving lens 162 and enters the photodetector 164 as a light receiving member. Based on the incident position of the light beam projected by the light projecting optical system on the photodetector 164 and the light projection angle of the light beam, position information such as the distance, direction and moving speed of the object can be acquired.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the gist of the present invention. .

  As described above, the present invention is useful for a light projecting optical system that can change a light projecting range and is advantageous for downsizing, and a light projecting apparatus including the light projecting optical system.

It is a figure explaining the operation | movement which changes the light projection range in the light projection optical system of this invention. It is another figure explaining the operation | movement which changes the light projection range in the light projection optical system of this invention. It is a figure which shows schematic structure of the light projector of this invention. (A) is a figure which shows the light distribution characteristic of the horizontal direction of a light source, (b) is a figure which shows the light distribution characteristic of a vertical direction. (A) of the light projection optical system which concerns on Example 1 is a figure which shows the cross-sectional structure of a vertical direction, (b) is a figure which shows the cross-sectional structure of a horizontal direction. (A) by the light projection optical system which concerns on Example 1 is a figure which shows intensity distribution of the vertical direction of a projection light beam, (b) is a figure which shows intensity distribution of a horizontal direction. (A) of the light projection optical system which concerns on Example 2 is a figure which shows the cross-sectional structure of a vertical direction, (b) is a figure which shows the cross-sectional structure of a horizontal direction. (A) by the light projection optical system which concerns on Example 2 is an intensity distribution of the vertical direction of a light projection light beam, (b) is a figure which shows the intensity distribution of a horizontal direction.

Explanation of symbols

48A to 48H Wire spring 132 Laser diode 156 Principal ray 158 Object 162 Light receiving lens 164 Photo detector 201 Light source 202 Condensing lens group 202A Biconvex positive lens 202a Optical axis 203 Projecting lens group 203A Biconcave negative lens 203a Optical axis 211 Light source image 241 Central rays 242, 243 rays

Claims (23)

A light source;
A condenser lens group having a positive refractive power that converts a luminous flux diverging from the light source into a convergent light having a negative lateral magnification;
A light projecting lens group having a negative refractive power for projecting the light flux from the condenser lens group so that the emitted light flux approaches a parallel light flux with respect to the light flux from the condenser lens group,
Eccentrically moving the focusing lens group have line changes light projection range,
A light projecting optical system characterized in that a relationship between the condenser lens group and the light projecting lens group satisfies the following conditional expression .
−0.7 <f _P / f _N <−0.2 (1)
here,
f _P is the focal length of the condenser lens group,
f _N is the focal length of the projection lens group,
It is. The condenser lens group is composed of one positive lens component having a positive refractive power,
The projection optical system according to claim 1, wherein the projection lens group has only one negative lens component having a negative refractive power.
However, the lens component means a lens having only two refracting surfaces in contact with air on the optical axis, that is, a surface on the side where the optical axis is incident and a surface on the side where the optical axis is emitted. The projection optical system according to claim 2, wherein the positive lens component of the condenser lens group has a biconvex shape that satisfies the following conditional expression.
−3.0 <β _P <-0.7 (A)
-0.2 <SF _P <0.2 (B)
However,
β _P Is the lateral magnification of the positive lens component of the condenser lens group,
SF _P Is the shape factor of the positive lens component of the condenser lens group;
Let r be the paraxial radius of curvature of the incident side _Pi , The paraxial radius of curvature of the injection side _Po And when
  SF _P = (R _Pi + R _Po ) / (R _Pi -R _Po )
Defined by 4. The light projecting optical system according to claim 2, wherein all the lenses in the light projecting lens group are single lenses made of plastic. The light projecting optical system according to claim 2, wherein the light projecting lens group has a toric refractive surface. The light projecting optical system according to any one of claims 2 to 4, wherein the light projecting lens group includes one negative lens component having a negative refractive power. The light projecting optical system according to claim 6, wherein the shape of the negative lens component of the light projecting lens group is a biconcave shape that satisfies the following conditional expression.
-0.9 <SF _Nn <-0.3 (C)
−1.6 <r _Nni / D _PN <-0.7 (D)
However,
SF _Nn Is the shape factor of the negative lens component of the projection lens group;
Let r be the paraxial radius of curvature of the incident side _Nni , The paraxial radius of curvature of the injection side _Nno And when
SF _Nn = (R _Nni + R _Nno ) / (R _Nni -R _Nno )
Defined in
r _Nni Is the paraxial curvature radius of the incident side surface of the negative lens component of the projection lens group,
D _PN Is the distance on the optical axis between the condenser lens group and the projection lens group,
It is. The projection lens group is sequentially from the light source side.
The light projecting optical system according to any one of claims 2 to 5, comprising two lens components, the negative lens component and a positive lens component having a positive refractive power. The light projecting optical system according to claim 8, wherein a relationship between the negative lens component and the positive lens component of the light projecting lens group satisfies the following conditional expression.
−0.4 <f _Nn / F _Np <-0.1 (2)
here,
f _Nn Is the focal length of the negative lens component in the projection lens group,
f _Np Is the focal length of the positive lens component in the projection lens group,
It is. The light projecting optical system according to claim 9, wherein the shape of the negative lens component of the light projecting lens group is a biconcave shape that satisfies the following conditions.
-0.9 <SF _Nn <0.0 (E)
−1.0 <r _Nni / D _PN <-0.2 (F)
However,
SF _Nn Is the shape factor of the negative lens component of the projection lens group,
Let r be the paraxial radius of curvature of the incident side _Nni , The paraxial radius of curvature of the injection side _Nno And when
SF _Nn = (R _Nni + R _Nno ) / (R _Nni -R _Nno )
Defined in
r _Nni Is the paraxial curvature radius of the incident side surface of the negative lens component of the projection lens group,
D _PN Is the distance on the optical axis between the condenser lens group and the projection lens group,
It is. The projection optical system according to claim 10, wherein the shape of the positive lens component of the projection lens group is a meniscus shape that satisfies the following condition.
5.0 <SF _Np <20.0 (G)
−5.0 <r _Npi / D _np <-1.0 (H)
However,
SF _Np Is the shape factor of the positive lens component of the projection lens group;
Let r be the paraxial radius of curvature of the incident side _Npi , The paraxial radius of curvature of the injection side _Npo And when
  SF _Np = (R _Npi + R _Npo ) / (R _Npi -R _Npo )
Defined in
r _Npi Is the paraxial radius of curvature of the incident side surface of the positive lens component of the projection lens group,
D _np Is the distance on the optical axis between the negative lens component and the positive lens component in the projection lens group,
It is. The light projecting optical system according to claim 8, wherein the positive lens component and the negative lens component of the light projecting lens group are single lenses made of plastic. The light projecting optical system according to claim 8, wherein the positive lens component of the light projecting lens group has a toric refracting surface. The light projecting optical system according to claim 5 or 13, wherein the toric surface is an aspherical surface whose curvature changes as it moves away from the optical axis of the lens at least in a decentering direction. The positive lens component of the condensing lens group has a convex aspheric surface whose absolute value of curvature decreases as the distance from the optical axis of the lens increases. Projection optics. The projection optical system according to any one of claims 2 to 15, wherein the positive lens component of the condenser lens group is made of glass. The projection optical system according to any one of claims 2 to 16, wherein the positive lens component of the condenser lens group is a single lens. The light projecting optical system according to claim 5, wherein the toric surface is a convex surface that satisfies the following conditional expression.
10 <1 / (RT _max / RT _min -1) <300 (I)
However,
RT _max Is the maximum value of the absolute value of the paraxial radius of curvature of the toric surface that varies depending on the direction,
RT _min Is the minimum value of the absolute value of the paraxial radius of curvature of the toric surface that varies depending on the direction,
It is. The light projection according to any one of claims 1 to 18, wherein a combined lateral magnification of a lateral magnification of the condenser lens group and a lateral magnification of the projection lens group satisfies the following conditional expression: Optical system.
−0.02 <β ^-1 _min <0.05 (J)
−0.02 <β ^-1 _max <0.10 (K)
However,
β ^-1 _min Is the minimum value of the reciprocal of the combined lateral magnification (total lateral magnification) in any direction that intersects the optical axis,
β ^-1 _max Is the maximum value of the reciprocal of the combined lateral magnification (total lateral magnification) in any direction that intersects the optical axis,
It is. The light projecting optical system according to any one of claims 1 to 19, wherein the light source includes at least one of a plurality of point light sources, a linear light source, and a planar light source. The light projecting optical system according to any one of claims 1 to 19, wherein a light emitting portion of the light source is linear or rectangular. The light projecting optical system according to any one of claims 1 to 19, wherein the light source is a light emitting diode or a semiconductor laser, and a light emitting portion of the light source is rectangular or linear . The light reception which acquires the positional information on the said object based on the light projection optical system as described in any one of Claims 1-22, and the light beam projected by the said light projection optical system reflected by the target object A light projecting device comprising a member.

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