WO2016002442A1 - Distance measurement device and method - Google Patents
Distance measurement device and method Download PDFInfo
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- WO2016002442A1 WO2016002442A1 PCT/JP2015/066469 JP2015066469W WO2016002442A1 WO 2016002442 A1 WO2016002442 A1 WO 2016002442A1 JP 2015066469 W JP2015066469 W JP 2015066469W WO 2016002442 A1 WO2016002442 A1 WO 2016002442A1
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- light
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- half mirror
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C3/00—Measuring distances in line of sight; Optical rangefinders
- G01C3/02—Details
- G01C3/06—Use of electric means to obtain final indication
Definitions
- the present invention relates to a distance measurement technique, and more particularly to an optical distance measurement technique for irradiating an object with light and reflecting the object, and measuring an objective distance to the object based on the reflected light.
- Optical measuring devices that can measure the object distance to an object in a non-contact manner using light such as laser light are known.
- Such an optical measuring apparatus is not only for measuring an objective distance to an object, but is also considered to be applied to various uses such as measuring the surface shape of an object and measuring the thickness of a thin film.
- an optical measuring device for example, laser light is irradiated obliquely to the surface of an object, and the distance to the surface is calculated based on the principle of triangulation based on the position where the reflected light has reached. It has been known.
- Such an optical measuring apparatus is widely used as an inexpensive measuring apparatus because the apparatus configuration is relatively simple. However, since the tilt of the reflecting surface directly affects the distance measurement value, the measurement error increases when the surface of the object to be measured is not flat.
- An optical lens system is disposed between the measurement point and the CCD image sensor, and the reflected light reaches the CCD image sensor through the optical lens system.
- the optical lens system is configured such that the reflected light from the point to be measured passes through a plurality of optical paths and is then irradiated on the CCD image sensor. Since the optical path lengths of the respective optical paths are different from each other, interference fringes are generated on the CCD image sensor due to the optical path difference.
- the fringe spacing of the interference fringes changes according to the objective distance between the measurement point and the CCD image sensor. Therefore, in this optical measuring device, the objective distance to the measurement point is calculated based on the fringe interval obtained from the output of the CCD image sensor.
- an optical lens system in order to generate a plurality of optical paths having different optical path lengths.
- Such an optical lens system is a multifocal lens that requires precise polishing. Or a spherical lens. Accordingly, such optical lens systems are generally expensive and require precise assembly. For this reason, there existed a problem that the cost of a distance measuring device increased.
- the present invention is to solve such problems, and an object of the present invention is to provide a distance measuring technique capable of accurately measuring an objective distance to an object with an optical lens system having a simple configuration.
- a distance measuring device is a distance measuring device that irradiates and reflects light on an object, and measures an objective distance to the object based on the reflected light.
- a double-sided half mirror that outputs from a second surface facing the surface, a light-detecting element that detects interference fringes generated on a detection surface by two output lights from the double-sided half-mirror, and detection obtained by the light-detecting element
- a distance calculation unit that calculates a result of the calculation to extract a pitch of the interference fringes and calculates an objective distance from the condenser lens to the object based on the pitch;
- the distance measuring method is a distance measuring method for irradiating and reflecting light on an object and measuring an objective distance to the object based on the reflected light, the reflected light from the object
- a condensing step for condensing the light into an imaginary spot, and the reflected light that has passed through the imaginary spot is internally separated into two output lights, from a second surface facing the first surface on which the reflected light is incident
- a light separating step for outputting a light detecting step for detecting interference fringes generated on a detection surface by two output lights from the double-sided half mirror; and a detection result obtained by the light detecting element for arithmetic processing to perform the interference.
- reflected light from an object is separated into two output lights having different imaginary spot positions as virtual condensing points.
- Interference fringes whose pitch changes according to the object distance are generated on the detection surface by the output light.
- FIG. 1 is an explanatory diagram illustrating the configuration of the distance measuring apparatus according to the first embodiment.
- FIG. 2 is an explanatory diagram showing an interval between two imaginary spots generated by the double-sided half mirror.
- FIG. 3 is an explanatory view showing the extension of the image formation point by the double-sided half mirror.
- FIG. 4 is an explanatory view showing the shift of light by the double-sided half mirror.
- FIG. 5 is an explanatory diagram showing the chief ray of the first output light.
- FIG. 6 is an explanatory diagram showing the chief ray of the second output light.
- FIG. 7 is an explanatory diagram showing the relationship between the light spot interval and the optical path difference.
- FIG. 8 is an explanatory diagram showing the principle of distance measurement according to the present invention.
- FIG. 1 is an explanatory diagram illustrating the configuration of the distance measuring apparatus according to the first embodiment.
- FIG. 2 is an explanatory diagram showing an interval between two imaginary spots generated by the double-sided half mirror.
- FIG. 3 is an
- FIG. 9 is an image example showing interference fringes generated on the detection surface.
- FIG. 10 is an analysis example of the detection result obtained by the light detection element.
- FIG. 11 is an explanatory diagram illustrating the configuration of the distance measuring apparatus according to the second embodiment.
- FIG. 12 is a graph showing the relationship between the objective distance and the interference fringe pitch.
- This distance measuring device 10 has a function of irradiating and reflecting light on an object T to be measured for distance, and measuring an objective distance to the object T based on the reflected light.
- the distance measurement apparatus 10 includes, as main components, a light source 11, a light source lens 12, a beam splitter 13, a condenser lens 14, a double-sided half mirror 15, a light detection element 16, and a distance calculation unit 17. These are housed inside a casing (not shown).
- the light source 11 is a device that emits light of a single wavelength (monochromatic light) used for distance measurement.
- a monochromatic light such as a semiconductor laser device or a sodium lamp, or a device that emits light having a single wavelength by a white light source and a narrow band-pass filter.
- the light source lens 12 has a function of condensing the light emitted from the light source 11 and outputting it to the beam splitter 13.
- the beam splitter 13 is disposed on the optical axis O of the condensing optical system, reflects the light from the light source 11 collected by the light source lens 12, and is directed to the light spot A of the object T along the optical axis O. Of the reflected light diffused and reflected by the light spot A, the reflected light reflected in the direction of the optical axis O is transmitted to the condenser lens 14. In the present invention, when the light spot A is not on the optical axis O, the optical axis is read as a principal ray.
- the condensing lens 14 is composed of, for example, a convex lens, and is disposed on the optical axis O and has a function of condensing the reflected light from the object T transmitted through the beam splitter 13 onto the imaginary spot Q.
- the double-sided half mirror 15 has a first surface 15A and a second surface 15B having semi-translucency, which are made of a transparent parallel plate as a whole and are arranged in parallel to each other and subjected to processing such as half-mirror coating.
- the principal ray S that is reflected light that is disposed with an inclination with respect to the optical axis O of the condensing optical system and passes through the imaginary spot Q is internally separated into two output lights S1 and S2, and the reflected light Has a function of outputting from the second surface 15B facing the first surface 15A.
- the incident principal ray S mainly passes through the first surface 15A and then passes through the second surface 15B, and the incident principal ray S passes through the first surface 15A. After that, the light is separated into the second output light S2 that is reflected by the second surface 15B, then reflected again by the first surface 15A, and then transmitted through the second surface 15B.
- the transmittance and the reflectance on the first surface 15A and the second surface 15B of the double-sided half mirror 15 are not limited to 1: 1, and may be other than 1: 1.
- the light detection element 16 has a function of detecting interference fringes generated on the detection surface I using the two output lights S1 and S2 that have passed through the double-sided half mirror 15, and outputting a detection result.
- a light detection element 16 for example, a light receiving element arranged in one dimension such as a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) linear image sensor, or a photodiode array can be used.
- the distance calculation unit 17 includes an arithmetic processing circuit using a CPU, extracts the pitch (period length) of the interference fringes by performing arithmetic processing on the detection result obtained by the light detection element 16, and based on the obtained pitch. It has a function of calculating the objective distance from the condenser lens 14 to the object T.
- FIG. 8 only the condensing optical system of the distance measuring device 10 is shown as the main part, and the projection optical system is omitted. 2 to 8, for the sake of easy understanding, only the principal ray is shown as the ray, and the vertical direction of the drawing in the direction orthogonal to the optical axis O is the X direction, and the vertical direction of the drawing is the Y direction. The left-right direction on the paper along the optical axis O was taken as the Z direction.
- the lens originally has two principal points according to the incident direction of light, and the positions thereof are different, but in the following, in order to avoid complication of the mathematical expression, the condenser lens 14 is composed of a thin single lens, Assuming that there is only one principal point at the lens center, each equation was derived.
- the second surface mainly passes through the first surface 15 ⁇ / b> A.
- the output light S2 is separated. Therefore, the second output light S2 is parallel to the first output light S1, but is reflected twice inside the double-sided half mirror 15, and therefore the position where the first output light S1 is emitted from the second surface 15B. It is emitted from different positions.
- the virtual condensing points (light source points) of the first output light S1 and the second output light S2 are imaginary spots Q1 and Q2
- double-sided half Due to refraction and reflection at the mirror 15 these imaginary spots Q 1 and Q 2 are located at different positions that are shifted from the imaginary spot Q of the actual principal ray S. Therefore, when the first and second output lights S1, S2 from the imaginary spots Q1, Q2 are projected onto the detection surface I of the light detection element 16, interference fringes are generated on the detection surface I.
- the present invention pays attention to the fact that the pitch p of the interference fringes changes according to the objective distance a from the condenser lens 14 to the light spot A of the object T, and detects the interference fringes generated on the detection surface I. It is detected by the element 16 and the distance calculation unit 17 measures the pitch p, and the objective distance a from the condenser lens 14 to the object T is calculated based on the obtained pitch p.
- the first and second output lights S1 and S2 emitted from the double-sided half mirror 15 have the principal ray S along the normal direction Zg of the double-sided half mirror 15 to the detection surface I side or the condenser lens 14 side, respectively. It can be regarded as a translation. Therefore, if the distances Ld1 and Ld2 from the imaginary spot Q to the imaginary spots Q1 and Q2 in the normal direction Zg of the double-sided half mirror 15 are calculated, the imaginary spot between the imaginary spots Q1 and Q2 in the Z direction from these Ld1 and Ld2 The interval ⁇ Z can be obtained.
- a medium G having translucency composed of parallel flat plates such as a double-sided half mirror 15 having a high refractive index is disposed between a condensing lens C for condensing the light Sa and its imaging point Pa.
- the light Sa is translated, and the imaging point of the light Sb transmitted through the medium G is extended from the imaging point Pa to the imaging point Pb along the normal direction Zg of the medium G. become.
- the relative refractive index of the medium G is n
- the thickness of the medium G is t
- the incident angle of the light Sa to the medium G is ⁇ 1
- the refraction angle inside the medium G is ⁇ 2.
- the optical axis O is inclined and the normal line of the double-sided half mirror 15 is used as a reference (horizontal). Similar to the parallel movement of the light described above, the first output light S1 emitted from the double-sided half mirror 15 has a principal ray S incident on the double-sided half mirror 15 as shown in FIG. It can be considered that it is translated along the normal direction Zg.
- the principal ray S incident from the point A on the first surface 15A at the incident angle ⁇ 1 is refracted at an angle of refraction angle ⁇ 2 with respect to the normal direction Zg, and then passes through the inside of the double-sided half mirror 15, The light is emitted from the point C on the second surface 15B as the first output light S1.
- the position where the normal passing through the point A intersects with the second surface 15B is defined as a point B, and the position where the first output light S1 extends to the first surface 15A side intersects with the first surface 15A.
- the point A ′′ is the point A ′ and the position where the line A ′′ -C intersects the line AB is the point A ′
- the first output light S1 passing through the point A ′ and emitted from the point C is .
- the straight traveling light S1 ′ of the principal ray S incident on the point A can be regarded as being translated to the point A ′ on the detection surface I side along the normal direction Zg, and the distance of the line segment AA ′.
- d1 corresponds to the parallel movement distance of the first output light S1.
- the optical path length of the chief ray S is shortened to the detection surface I side by the length Ld1 of the line segment A ′′ -A ′ by such parallel movement of the first output light S1.
- the imaginary spot Q has moved to the imaginary spot Q1 on the detection surface I side by a distance d1 along the normal direction Zg.
- This Ld1 is obtained by the following equation (9) from the distance d1 obtained by the equation (8).
- the optical axis O is inclined and the normal line of the double-sided half mirror 15 is used as a reference.
- the second output light S2 emitted from the double-sided half mirror 15 has a principal ray S incident on the double-sided half mirror 15 as shown in FIG. It can be considered that the double-sided half mirror 15 is translated along the normal direction Zg.
- the principal ray S incident from the point A on the first surface 15A at the incident angle ⁇ 1 is refracted at an angle of refraction angle ⁇ 2 with respect to the normal direction Zg, and then passes through the inside of the double-sided half mirror 15, The light is reflected by the second surface 15B and the first surface 15A, and is emitted from the point E on the second surface 15B as the first output light S1.
- the path from the point A to the point E can be regarded as the same as the path that passes through the double-sided half mirror 15 having a thickness of 3 t without being reflected. Therefore, the path from the point A to the point E is developed on the left side of the first surface 15A, and the normal line passing through the development path and the point A on the virtual first surface separated by the distance 2t from the first surface 15A Is the point D, and when the second output light S2 is extended to the virtual first surface side, the point that intersects the normal passing through the point A is the point D ', and the point D' is passed.
- the second output light S2 can be regarded as the straight light S2 ′ of the principal ray S ′ incident on the point D being translated to the detection surface I side along the normal direction Zg.
- ⁇ D ′ corresponds to the parallel movement distance d2 of the second output light S2.
- the distance Ld2 ′ includes a developed distance 2t / cos ⁇ 1 developed by 2t up to the virtual first surface. Therefore, when the second output light S2 is extended to the virtual first surface side and the point intersecting with the first surface 15B is a point D ′ ′′, only the line segment D′ ⁇ D ′ ′′ It can be considered that the optical path length of the light beam S extends to the condensing lens 14 side, and this optical path length Ld2 is obtained by the following equation (13).
- the interval ⁇ z between the imaginary spots Q1 and Q2 in the Z direction is obtained by the following equation (14) based on the optical path difference Ld1 of the first output light S1 and the optical path difference Ld2 of the second output light S2.
- the imaginary spots Q1 and Q2 are separated by an interval ⁇ X in the X direction and are separated by an interval ⁇ Z in the Z direction.
- the arrival point at which the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 have reached the detection surface I of the light detection element 16 is defined as V
- the imaginary spot Q1 is defined as
- the intersection of the X-direction line passing through and the Z-direction line passing through the imaginary spot Q2 is defined as a point D, and a point where the line extending from the intermediate point D0 of the line segment Q1-D and extending in the Z direction intersects the detection surface I.
- V0 is a distance from V0 to V along the Y direction on the detection surface I
- P is a distance from the imaginary spot Q1 to the detection surface I.
- the optical path length L1 from the imaginary spot Q1 to the arrival point V with respect to the first output light S1 is obtained by the following equation (15) by the three-square theorem.
- the interval ⁇ x is very small compared to the distance c, and the slopes of the first output light S1 and the second output light S2 represented by the slope ⁇ of the line segment D0-V with respect to the Z direction are very small. Therefore, the optical path length L1 can be approximated as the following equation (16).
- the optical path length L2 from the imaginary spot Q2 to the arrival point V regarding the second output light S2 is the line segment Q2-Q2 'And the sum of the optical path length L22 of the line segment Q2'-V.
- the optical path length L21 is obtained by the following equation (17) in the same manner as the equation (16) described above, where the distance of the line segment DQ2 ′ is x ′.
- the optical path length L21 can be approximated by ⁇ z.
- the optical path length L22 is obtained by the following equation (18) by the square theorem, similarly to the optical path length L1.
- the optical path length L2 is obtained by the following equation (19), and the optical path difference ⁇ L between the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 is It is calculated
- interference fringes are generated due to this optical path difference ⁇ L.
- the optical path difference ⁇ L is an integer m (m is an integer of 0 or more) times the wavelength ⁇ of light, A bright line appears.
- the interval ⁇ z of the optical path difference ⁇ L is a constant value, and this value only affects the initial phase of the interference fringes and does not affect the interference fringe pitch p.
- the objective distance from the object T to the principal point M that is, the position of the condenser lens 14 is a
- the distance from the principal point to the imaginary spot Q is b
- the focal length of the condenser lens 14 Where f is expressed by the following formula (22) by the imaging formula (lens formula).
- the above-described equation (21) becomes the following equation (23). Therefore, from the equation (23, the objective distance a from the object T to the principal point M, that is, the position of the condenser lens 14, is obtained by the following equation (24).
- the interference fringes are formed by repeating bright lines with high luminance and dark lines with low luminance in a stripe shape. Accordingly, the interval between adjacent bright lines (or dark lines) corresponds to the interference fringe pitch p.
- the horizontal axis indicates the pixel position [pic] of the image along the X direction orthogonal to the interference fringes
- the vertical axis indicates the light intensity (no unit) at each pixel position.
- the obtained detection result has a substantially sine wave shape, and its peak position corresponds to a bright line. Therefore, the actual distance indicating the interference fringe pitch p can be calculated from the number of pixels existing between the peak positions.
- the reflected light from the object T is once condensed on the imaginary spot Q by the condenser lens 14, and then separated into two output lights by the double-sided half mirror 15, and the reflected light is
- the light is output from the second surface opposite to the incident first surface, the interference fringes generated on the detection surface I by these two output lights are detected by the light detection element 16, and the obtained detection results are subjected to arithmetic processing to cause interference.
- the fringe pitch is extracted, and the distance calculation unit 17 calculates the objective distance a from the condenser lens 14 to the object T based on this pitch.
- the output light S1 and S2 of the output light S1 and S2 that are different from each other in the positions of the imaginary spots Q1 and Q2, which are virtual condensing points, are reflected light from the object T by a very simple existing optical element called the double-sided half mirror 15.
- Interference fringes whose pitch p changes according to the objective distance a are generated on the detection surface I by these output lights S1 and S2. Therefore, it is not necessary to use a conventional multifocal lens or spherical lens that requires precise polishing, and an expensive optical lens and its precise assembly can be omitted. For this reason, it is possible to realize a distance measuring device that can accurately measure the objective distance a to the object T at a relatively low cost.
- the double-sided half mirror 15 is provided with two first and second surfaces 15A and 15B arranged in parallel, each having semi-translucency, and the reflected light once condensed on the imaginary spot Q is provided.
- the light transmitted through the first surface 15A is transmitted without being reflected by the second surface 15B and is output as the first output light S1
- the light transmitted through the first surface 15A is reflected by the second surface 15B.
- the light is reflected again by the first surface 15A, transmitted through the second surface 15B, and output as the second output light S2.
- the reflected light S from the imaginary spot Q is converted into the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 with a very simple optical element called the double-sided half mirror 15. They can be easily separated and interference fringes can be generated efficiently. Further, since the interference fringes have a sine wave shape, the interference fringe pitch p can be easily measured, and the interference fringes are not localized, that is, the phenomenon in which the interference fringes appear only in the vicinity of a specific periodic distance does not occur. The measurement span of the objective distance a can be widened. Furthermore, since the interference fringe pitch p is constant on the detection surface I, there is no need to correct the detection result of the light detection element 16, and the arithmetic processing can be simplified and the measurement error of the interference fringe pitch p can be reduced.
- the distance measuring apparatus 10 concerning the 2nd Embodiment of this invention is demonstrated.
- the objective lens 20 is provided in the condensing optical system in the first embodiment described above, and the reflected light from the object T is parallel in the section between the objective lens 20 and the condenser lens 14. The case of converting to light will be described.
- the objective lens 20 has a function of converting the reflected light from the object T into parallel light and outputting it to the condenser lens 14.
- the beam splitter 13 is disposed between the objective lens 20 and the condenser lens 14. Thereby, the light emitted from the light source 11 is converted into parallel light by the light source lens 12, reflected by the beam splitter 13, and then condensed by the objective lens 20 and applied to the object T.
- the reflected light from the object T is converted into parallel light by the objective lens 20, passes through the beam splitter 13, and is once condensed on the imaginary spot Q by the condenser lens 14, and then starts to spread from the imaginary spot Q.
- the reflected light passes through the double-sided half mirror 15 and is applied to the detection surface I.
- the relationship between the objective distance a and the interference fringe pitch p is obtained by simulation based on the present embodiment.
- the objective lens 20 is provided in the condensing optical system, and the reflected light from the object T is converted into parallel light in the section between the objective lens 20 and the condensing lens 14. Therefore, even if the objective distance a to the object T changes, the optical path is changed in the section from the objective lens 20 to the detection surface I by replacing the objective lens 20 with a focal length corresponding to the objective distance a. It becomes constant. For this reason, it is possible to deal with a wide range of objective distances a, and the measurement range can be greatly expanded.
- SYMBOLS 10 Distance measuring device, 14 ... Condensing lens, 15 ... Double-sided half mirror, 16 ... Photodetection element, 17 ... Distance calculation part, T ... Object, Q ... Imaginary spot, I ... Detection surface, a ... Objective distance, p ... interference fringe pitch.
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Abstract
The present invention involves: first concentrating reflected light from an object (T) onto an imaginary spot (Q) by using a light-concentrating lens (14); thereafter, separating into two output light beams by using a two-surface half mirror (15); outputting from a second surface facing a first surface on which the reflected light is incident; using a photodetection element (16) to detect an interference fringe produced on a detection surface (I) by the two output light beams; extracting an interference fringe pitch (p) by computing the obtained detection results; and using a distance calculation unit (17) to calculate the target distance (a) from the light-collecting lens (14) to the object (T), on the basis of this pitch (p). As a result, it is possible to accurately measure the target distance (a) to an object (T) using an optical lens system having a simple configuration.
Description
本発明は、距離測定技術に関し、特に物体に光を照射して反射させ、その反射光に基づいて物体までの対物距離を測定する光学的距離測定技術に関する。
The present invention relates to a distance measurement technique, and more particularly to an optical distance measurement technique for irradiating an object with light and reflecting the object, and measuring an objective distance to the object based on the reflected light.
レーザー光等の光を用いて、物体までの対物距離を非接触で測定できる光学的測定装置が知られている。このような光学的測定装置は、単に物体までの対物距離を測定するだけではなく、物体の表面形状測定や、薄膜の厚さ測定等、様々な用途への応用が考えられている。
Optical measuring devices that can measure the object distance to an object in a non-contact manner using light such as laser light are known. Such an optical measuring apparatus is not only for measuring an objective distance to an object, but is also considered to be applied to various uses such as measuring the surface shape of an object and measuring the thickness of a thin film.
このような光学的測定装置としては、例えば、レーザー光を物体の表面に対して斜めに照射し、その反射光が到達した位置に基づいて、表面までの距離を三角測量の原理で算出するものが知られている。このような方式の光学的測定装置は装置構成が比較的単純であるため、安価な測定装置として広く普及している。しかしながら、反射面の傾きが距離の測定値に直接影響してしまう方式であるため、測定対象である物体の表面が平坦でない場合には測定誤差が大きくなる。
As such an optical measuring device, for example, laser light is irradiated obliquely to the surface of an object, and the distance to the surface is calculated based on the principle of triangulation based on the position where the reflected light has reached. It has been known. Such an optical measuring apparatus is widely used as an inexpensive measuring apparatus because the apparatus configuration is relatively simple. However, since the tilt of the reflecting surface directly affects the distance measurement value, the measurement error increases when the surface of the object to be measured is not flat.
これに対し、物体の表面が平坦でない場合にも適用できる距離測定装置として、光の干渉を利用する方式の光学的測定装置が提案されている。例えば、下記特許文献1に記載された光学的測定装置では、物体の被測定点に光を照射して反射させ、その反射光が、干渉縞の検出面であるCCDイメージセンサに到達するような構成となっている。
On the other hand, as a distance measuring device that can be applied even when the surface of an object is not flat, an optical measuring device using a light interference has been proposed. For example, in the optical measuring apparatus described in Patent Document 1 below, light is irradiated to a measurement point of an object and reflected, and the reflected light reaches a CCD image sensor which is an interference fringe detection surface. It has a configuration.
被測定点とCCDイメージセンサとの間には光学レンズ系が配置されており、反射光は当該光学レンズ系を通ってCCDイメージセンサに到達する。光学レンズ系は、被測定点からの反射光が複数の光路をそれぞれ通過した後、CCDイメージセンサに重ねて照射されるように構成されたものである。それぞれの光路の光路長は互いに異なっているため、CCDイメージセンサ上には光路差に起因して干渉縞が生じる。
An optical lens system is disposed between the measurement point and the CCD image sensor, and the reflected light reaches the CCD image sensor through the optical lens system. The optical lens system is configured such that the reflected light from the point to be measured passes through a plurality of optical paths and is then irradiated on the CCD image sensor. Since the optical path lengths of the respective optical paths are different from each other, interference fringes are generated on the CCD image sensor due to the optical path difference.
当該干渉縞の縞間隔は、被測定点とCCDイメージセンサとの対物距離に応じて変化する。従って、この光学的測定装置では、CCDイメージセンサの出力から得られた縞間隔に基づいて、被測定点までの対物距離が算出される。
The fringe spacing of the interference fringes changes according to the objective distance between the measurement point and the CCD image sensor. Therefore, in this optical measuring device, the objective distance to the measurement point is calculated based on the fringe interval obtained from the output of the CCD image sensor.
しかしながら、このような従来技術では、互いに光路長の異なる複数の光路を生じさせるため、光学レンズ系を配置する必要があるが、このような光学レンズ系は、精密な研磨加工を要する多重焦点レンズや球体レンズ等によって構成される。したがって、このような光学レンズ系は、一般に高価となり、また精密な組み立てを必要とする。このため、距離測定装置のコストが増大するという問題点があった。
However, in such a conventional technique, it is necessary to arrange an optical lens system in order to generate a plurality of optical paths having different optical path lengths. Such an optical lens system is a multifocal lens that requires precise polishing. Or a spherical lens. Accordingly, such optical lens systems are generally expensive and require precise assembly. For this reason, there existed a problem that the cost of a distance measuring device increased.
本発明はこのような課題を解決するためのものであり、簡素な構成の光学レンズ系により、物体までの対物距離を正確に測定することができる距離測定技術を提供することを目的としている。
The present invention is to solve such problems, and an object of the present invention is to provide a distance measuring technique capable of accurately measuring an objective distance to an object with an optical lens system having a simple configuration.
このような目的を達成するために、本発明にかかる距離測定装置は、物体に光を照射して反射させ、その反射光に基づいて当該物体までの対物距離を測定する距離測定装置であって、前記物体からの前記反射光を虚スポットに集光させる集光レンズと、前記虚スポットを通過した前記反射光を内部で2つの出力光に分離して、当該反射光が入射される第1面と対向する第2面から出力する両面ハーフミラーと、前記両面ハーフミラーからの2つの出力光により検出面に生じた干渉縞を検出する光検出素子と、前記光検出素子で得られた検出結果を演算処理して前記干渉縞のピッチを抽出し、このピッチに基づいて前記集光レンズから前記物体までの対物距離を算出する距離算出部とを備えている。
In order to achieve such an object, a distance measuring device according to the present invention is a distance measuring device that irradiates and reflects light on an object, and measures an objective distance to the object based on the reflected light. A first condensing lens for condensing the reflected light from the object onto an imaginary spot, and the reflected light that has passed through the imaginary spot is internally separated into two output lights, and the reflected light is incident on the first lens A double-sided half mirror that outputs from a second surface facing the surface, a light-detecting element that detects interference fringes generated on a detection surface by two output lights from the double-sided half-mirror, and detection obtained by the light-detecting element A distance calculation unit that calculates a result of the calculation to extract a pitch of the interference fringes and calculates an objective distance from the condenser lens to the object based on the pitch;
また、本発明にかかる距離測定方法は、物体に光を照射して反射させ、その反射光に基づいて当該物体までの対物距離を測定する距離測定方法であって、前記物体からの前記反射光を虚スポットに集光させる集光ステップと、前記虚スポットを通過した前記反射光を内部で2つの出力光に分離して、当該反射光が入射される第1面と対向する第2面から出力する光分離ステップと、前記両面ハーフミラーからの2つの出力光により検出面に生じた干渉縞を検出する光検出ステップと、前記光検出素子で得られた検出結果を演算処理して前記干渉縞のピッチを抽出し、このピッチに基づいて前記集光レンズから前記物体までの対物距離を算出する距離算出ステップとを備えている。
The distance measuring method according to the present invention is a distance measuring method for irradiating and reflecting light on an object and measuring an objective distance to the object based on the reflected light, the reflected light from the object A condensing step for condensing the light into an imaginary spot, and the reflected light that has passed through the imaginary spot is internally separated into two output lights, from a second surface facing the first surface on which the reflected light is incident A light separating step for outputting; a light detecting step for detecting interference fringes generated on a detection surface by two output lights from the double-sided half mirror; and a detection result obtained by the light detecting element for arithmetic processing to perform the interference. A distance calculating step of extracting a fringe pitch and calculating an objective distance from the condenser lens to the object based on the pitch.
本発明によれば、両面ハーフミラーという極めて簡素な既存の光学要素で、物体からの反射光が、仮想的な集光点である虚スポットの位置が互いに異なる2つの出力光に分離され、これら出力光により対物距離に応じてピッチが変化する干渉縞が検出面に発生する。このため、従来の精密な研磨加工を要する多重焦点レンズや球体レンズを用いる必要がなくなり、高価な光学系レンズやその精密な組み立てを省くことができる。したがって、比較的安価なコストで、物体までの対物距離を正確に測定することができる距離測定装置を実現することが可能となる。
According to the present invention, with a very simple existing optical element called a double-sided half mirror, reflected light from an object is separated into two output lights having different imaginary spot positions as virtual condensing points. Interference fringes whose pitch changes according to the object distance are generated on the detection surface by the output light. For this reason, there is no need to use a conventional multifocal lens or spherical lens that requires precise polishing, and expensive optical lenses and precise assembly thereof can be omitted. Therefore, it is possible to realize a distance measuring device that can accurately measure the objective distance to an object at a relatively low cost.
次に、本発明の実施の形態について図面を参照して説明する。
[第1の実施の形態] Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
[第1の実施の形態] Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
まず、図1を参照して、本発明の第1の実施の形態にかかる距離測定装置10について説明する。
First, a distance measuring device 10 according to a first embodiment of the present invention will be described with reference to FIG.
この距離測定装置10は、距離の測定対象となる物体Tに光を照射して反射させ、その反射光に基づいて物体Tまでの対物距離を測定する機能を有している。
図1に示すように、距離測定装置10には、主な構成として、光源11、光源レンズ12、ビームスプリッタ13、集光レンズ14、両面ハーフミラー15、光検出素子16、および距離算出部17が設けられており、これらがケーシング(図示せず)内部に収納されている。 Thisdistance measuring device 10 has a function of irradiating and reflecting light on an object T to be measured for distance, and measuring an objective distance to the object T based on the reflected light.
As shown in FIG. 1, thedistance measurement apparatus 10 includes, as main components, a light source 11, a light source lens 12, a beam splitter 13, a condenser lens 14, a double-sided half mirror 15, a light detection element 16, and a distance calculation unit 17. These are housed inside a casing (not shown).
図1に示すように、距離測定装置10には、主な構成として、光源11、光源レンズ12、ビームスプリッタ13、集光レンズ14、両面ハーフミラー15、光検出素子16、および距離算出部17が設けられており、これらがケーシング(図示せず)内部に収納されている。 This
As shown in FIG. 1, the
光源11は、距離測定に用いる単一波長の光(単色光)を発する装置である。光源11としては、半導体レーザー装置、ナトリウムランプのような単色光や、白色光源と狭帯域バンドパスフィルタにより単一波長化された光を発する装置を用いることができる。
光源レンズ12は、光源11から発せられた光を集光してビームスプリッタ13へ出力する機能を有している。 Thelight source 11 is a device that emits light of a single wavelength (monochromatic light) used for distance measurement. As the light source 11, it is possible to use a monochromatic light such as a semiconductor laser device or a sodium lamp, or a device that emits light having a single wavelength by a white light source and a narrow band-pass filter.
Thelight source lens 12 has a function of condensing the light emitted from the light source 11 and outputting it to the beam splitter 13.
光源レンズ12は、光源11から発せられた光を集光してビームスプリッタ13へ出力する機能を有している。 The
The
ビームスプリッタ13は、集光光学系の光軸O上に配置されて、光源レンズ12で集光された光源11からの光を反射して、光軸Oに沿って物体Tの光スポットAに照射する機能と、光スポットAで拡散反射された反射光のうち、光軸O方向に反射された反射光を集光レンズ14へ透過させる機能を有している。なお、本発明において、光スポットAが光軸O上にない場合は、光軸を主光線と読み替えるものとする。
集光レンズ14は、例えば凸レンズからなり、光軸O上に配置されて、ビームスプリッタ13を透過した物体Tからの反射光を虚スポットQに集光させる機能を有している。 Thebeam splitter 13 is disposed on the optical axis O of the condensing optical system, reflects the light from the light source 11 collected by the light source lens 12, and is directed to the light spot A of the object T along the optical axis O. Of the reflected light diffused and reflected by the light spot A, the reflected light reflected in the direction of the optical axis O is transmitted to the condenser lens 14. In the present invention, when the light spot A is not on the optical axis O, the optical axis is read as a principal ray.
Thecondensing lens 14 is composed of, for example, a convex lens, and is disposed on the optical axis O and has a function of condensing the reflected light from the object T transmitted through the beam splitter 13 onto the imaginary spot Q.
集光レンズ14は、例えば凸レンズからなり、光軸O上に配置されて、ビームスプリッタ13を透過した物体Tからの反射光を虚スポットQに集光させる機能を有している。 The
The
両面ハーフミラー15は、全体として透明の平行平板からなり、互いに平行配置された、ハーフミラーコーティングなどの処理が施された半透光性を持つ第1面15Aおよび第2面15Bを有し、集光光学系の光軸Oに対して傾きを持って配置されて、虚スポットQを通過した反射光である主光線Sを内部で2つの出力光S1,S2に分離して、当該反射光が入射される第1面15Aと対向する第2面15Bから出力する機能を有している。
The double-sided half mirror 15 has a first surface 15A and a second surface 15B having semi-translucency, which are made of a transparent parallel plate as a whole and are arranged in parallel to each other and subjected to processing such as half-mirror coating. The principal ray S that is reflected light that is disposed with an inclination with respect to the optical axis O of the condensing optical system and passes through the imaginary spot Q is internally separated into two output lights S1 and S2, and the reflected light Has a function of outputting from the second surface 15B facing the first surface 15A.
これにより、入射された主光線Sは、主に、第1面15Aを透過した後に第2面15Bを透過した第1の出力光と、入射された主光線Sが第1面15Aを透過した後に第2面15Bで反射し、その後第1面15Aで再び反射した後に第2面15Bを透過した第2の出力光S2とに分離されて出力される。
なお、両面ハーフミラー15の第1面15Aおよび第2面15Bにおける透過率と反射率については、1:1に限定されるものではなく、1:1以外であってもよい。 As a result, the incident principal ray S mainly passes through thefirst surface 15A and then passes through the second surface 15B, and the incident principal ray S passes through the first surface 15A. After that, the light is separated into the second output light S2 that is reflected by the second surface 15B, then reflected again by the first surface 15A, and then transmitted through the second surface 15B.
The transmittance and the reflectance on thefirst surface 15A and the second surface 15B of the double-sided half mirror 15 are not limited to 1: 1, and may be other than 1: 1.
なお、両面ハーフミラー15の第1面15Aおよび第2面15Bにおける透過率と反射率については、1:1に限定されるものではなく、1:1以外であってもよい。 As a result, the incident principal ray S mainly passes through the
The transmittance and the reflectance on the
光検出素子16は、両面ハーフミラー15を通過した2つの出力光S1,S2により、検出面Iに生じた干渉縞を検出し、検出結果を出力する機能を有している。光検出素子16としては、例えば、CCD(Charge Coupled Device)やCMOS(Complementary Metal Oxide Semiconductor)リニアイメージセンサや、フォトダイオードアレイなどの一次元上に配置した受光素子が利用できる。
距離算出部17は、CPUを用いた演算処理回路からなり、光検出素子16で得られた検出結果を演算処理して干渉縞のピッチ(周期長)を抽出し、得られたピッチに基づいて集光レンズ14から物体Tまでの対物距離を算出する機能を有している。 Thelight detection element 16 has a function of detecting interference fringes generated on the detection surface I using the two output lights S1 and S2 that have passed through the double-sided half mirror 15, and outputting a detection result. As the light detection element 16, for example, a light receiving element arranged in one dimension such as a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) linear image sensor, or a photodiode array can be used.
Thedistance calculation unit 17 includes an arithmetic processing circuit using a CPU, extracts the pitch (period length) of the interference fringes by performing arithmetic processing on the detection result obtained by the light detection element 16, and based on the obtained pitch. It has a function of calculating the objective distance from the condenser lens 14 to the object T.
距離算出部17は、CPUを用いた演算処理回路からなり、光検出素子16で得られた検出結果を演算処理して干渉縞のピッチ(周期長)を抽出し、得られたピッチに基づいて集光レンズ14から物体Tまでの対物距離を算出する機能を有している。 The
The
[距離計測の原理]
次に、図2~図8を参照して、本発明にかかる距離計測装置10で用いる距離計測の原理について説明する。なお、図8では、距離計測装置10のうち、集光光学系のみを要部として示し、投影光学系については省略してある。また、図2~図8において、理解を容易とするため、光線については主光線のみを示し、光軸Oと直交する方向のうち紙面上下方向をX方向とし、紙面垂直方向をY方向とし、光軸Oに沿った紙面左右方向をZ方向とした。また、本来、レンズには光の入射方向に応じて2つの主点があり、それぞれの位置が異なるが、以下では、数式の複雑化を避けるため、集光レンズ14が薄肉単レンズからなり、主点がレンズ中心に1つだけ存在すると仮定して、各式を導出した。 [Principle of distance measurement]
Next, the principle of distance measurement used in thedistance measuring apparatus 10 according to the present invention will be described with reference to FIGS. In FIG. 8, only the condensing optical system of the distance measuring device 10 is shown as the main part, and the projection optical system is omitted. 2 to 8, for the sake of easy understanding, only the principal ray is shown as the ray, and the vertical direction of the drawing in the direction orthogonal to the optical axis O is the X direction, and the vertical direction of the drawing is the Y direction. The left-right direction on the paper along the optical axis O was taken as the Z direction. In addition, the lens originally has two principal points according to the incident direction of light, and the positions thereof are different, but in the following, in order to avoid complication of the mathematical expression, the condenser lens 14 is composed of a thin single lens, Assuming that there is only one principal point at the lens center, each equation was derived.
次に、図2~図8を参照して、本発明にかかる距離計測装置10で用いる距離計測の原理について説明する。なお、図8では、距離計測装置10のうち、集光光学系のみを要部として示し、投影光学系については省略してある。また、図2~図8において、理解を容易とするため、光線については主光線のみを示し、光軸Oと直交する方向のうち紙面上下方向をX方向とし、紙面垂直方向をY方向とし、光軸Oに沿った紙面左右方向をZ方向とした。また、本来、レンズには光の入射方向に応じて2つの主点があり、それぞれの位置が異なるが、以下では、数式の複雑化を避けるため、集光レンズ14が薄肉単レンズからなり、主点がレンズ中心に1つだけ存在すると仮定して、各式を導出した。 [Principle of distance measurement]
Next, the principle of distance measurement used in the
集光レンズ14で虚スポットQに集光された物体Tからの反射光である主光線Sが、両面ハーフミラー15に入射された場合、主に、第1面15Aを透過した後に第2面15Bで反射させずに透過する第1の出力光S1と、第1面15Aを透過した後に第2面15Bで反射し、さらに第1面15Aで再び反射し第2面15Bを透過する第2の出力光S2とに分離される。したがって、第2の出力光S2は第1の出力光S1と平行であるが、両面ハーフミラー15内部で2回反射するため、第1の出力光S1が第2面15Bから出射する位置とは異なる位置から出射される。
When the principal ray S, which is the reflected light from the object T focused on the imaginary spot Q by the condenser lens 14, enters the double-sided half mirror 15, the second surface mainly passes through the first surface 15 </ b> A. The first output light S1 that is transmitted without being reflected by 15B, and the second output light that is transmitted by the first surface 15A, then reflected by the second surface 15B, is reflected again by the first surface 15A, and is transmitted by the second surface 15B. The output light S2 is separated. Therefore, the second output light S2 is parallel to the first output light S1, but is reflected twice inside the double-sided half mirror 15, and therefore the position where the first output light S1 is emitted from the second surface 15B. It is emitted from different positions.
ここで、両面ハーフミラー15の存在を無視して、第1の出力光S1と第2の出力光S2の仮想的な集光点(光源点)を虚スポットQ1,Q2とした場合、両面ハーフミラー15での屈折および反射により、これら虚スポットQ1,Q2は、実際の主光線Sの虚スポットQからそれぞれずれた互いに異なる位置となる。このため、虚スポットQ1,Q2からの第1および第2の出力光S1,S2が光検出素子16の検出面Iに投影された場合、検出面I上に干渉縞が発生する。
Here, ignoring the presence of the double-sided half mirror 15, if the virtual condensing points (light source points) of the first output light S1 and the second output light S2 are imaginary spots Q1 and Q2, double-sided half Due to refraction and reflection at the mirror 15, these imaginary spots Q 1 and Q 2 are located at different positions that are shifted from the imaginary spot Q of the actual principal ray S. Therefore, when the first and second output lights S1, S2 from the imaginary spots Q1, Q2 are projected onto the detection surface I of the light detection element 16, interference fringes are generated on the detection surface I.
本発明は、この干渉縞のピッチpが、集光レンズ14から物体Tの光スポットAまでの対物距離aに応じて変化することに着目し、検出面I上に発生した干渉縞を光検出素子16で検出して、距離算出部17で、そのピッチpを測定し、得られたピッチpに基づいて集光レンズ14から物体Tまでの対物距離aを算出するようにしたものである。
以下では、両面ハーフミラー15に対する主光線Sの入射角θ1、すなわち両面ハーフミラー15の傾きと、X方向およびZ方向における虚スポットQ1,Q2の間隔ΔX,ΔZとの関係を説明した上で、これら間隔ΔX,ΔZとピッチp、さらにはピッチpと対物距離aとの関係について説明する。 The present invention pays attention to the fact that the pitch p of the interference fringes changes according to the objective distance a from thecondenser lens 14 to the light spot A of the object T, and detects the interference fringes generated on the detection surface I. It is detected by the element 16 and the distance calculation unit 17 measures the pitch p, and the objective distance a from the condenser lens 14 to the object T is calculated based on the obtained pitch p.
Hereinafter, after explaining the relationship between the incident angle θ1 of the principal ray S with respect to the double-sided half mirror 15, that is, the inclination of the double-sided half mirror 15, and the distances ΔX and ΔZ between the imaginary spots Q1 and Q2 in the X direction and Z direction, The relationship between the distances ΔX and ΔZ and the pitch p, and the pitch p and the objective distance a will be described.
以下では、両面ハーフミラー15に対する主光線Sの入射角θ1、すなわち両面ハーフミラー15の傾きと、X方向およびZ方向における虚スポットQ1,Q2の間隔ΔX,ΔZとの関係を説明した上で、これら間隔ΔX,ΔZとピッチp、さらにはピッチpと対物距離aとの関係について説明する。 The present invention pays attention to the fact that the pitch p of the interference fringes changes according to the objective distance a from the
Hereinafter, after explaining the relationship between the incident angle θ1 of the principal ray S with respect to the double-
[X方向における虚スポット間隔Δx]
図2に示すように、両面ハーフミラー15の厚さ、すなわち第1面15Aと第2面15Bとの距離をtとし、両面ハーフミラー15に対する光Sの入射角をθ1とし、第1面15Aおよび第2面15Bにおける屈折角をθ2とした場合、第2面15Bにおける第1の出力光S1と第2の出力光S2の出射位置の距離wは、次の式(1)で表される。
また、両面ハーフミラー15の相対屈折率をnとした場合、スネルの法則から、θ1とθ2との関係は、次の式(2)で表される。
[Imaginary spot interval Δx in X direction]
As shown in FIG. 2, the thickness of the double-sided half mirror 15, that is, the distance between the first surface 15A and the second surface 15B is t, the incident angle of the light S with respect to the double-sided half mirror 15 is θ1, and the first surface 15A When the refraction angle on the second surface 15B is θ2, the distance w between the emission positions of the first output light S1 and the second output light S2 on the second surface 15B is expressed by the following equation (1). .
When the relative refractive index of the double-sided half mirror 15 is n, the relationship between θ1 and θ2 is expressed by the following equation (2) from Snell's law.
図2に示すように、両面ハーフミラー15の厚さ、すなわち第1面15Aと第2面15Bとの距離をtとし、両面ハーフミラー15に対する光Sの入射角をθ1とし、第1面15Aおよび第2面15Bにおける屈折角をθ2とした場合、第2面15Bにおける第1の出力光S1と第2の出力光S2の出射位置の距離wは、次の式(1)で表される。
As shown in FIG. 2, the thickness of the double-
したがって、式(2)を式(1)に代入した場合、距離wは、θ1を用いた次の式(3)となり、X方向における虚スポットQ1,Q2の間隔Δxは、次の式(4)で求められる。
Therefore, when Expression (2) is substituted into Expression (1), the distance w becomes the following Expression (3) using θ1, and the interval Δx between the imaginary spots Q1, Q2 in the X direction is expressed by the following Expression (4). ).
[Z方向における虚スポット間隔ΔZ]
両面ハーフミラー15から出射された第1および第2の出力光S1,S2は、主光線Sが両面ハーフミラー15の法線方向Zgに沿って、検出面I側あるいは集光レンズ14側にそれぞれ平行移動したものと見なすことができる。
したがって、両面ハーフミラー15の法線方向Zgにおける、虚スポットQから虚スポットQ1,Q2までの距離Ld1,Ld2を算出すれば、これらLd1,Ld2からZ方向における虚スポットQ1,Q2間の虚スポット間隔ΔZを求めことができる。 [Imaginary spot interval ΔZ in the Z direction]
The first and second output lights S1 and S2 emitted from the double-sided half mirror 15 have the principal ray S along the normal direction Zg of the double-sided half mirror 15 to the detection surface I side or the condenser lens 14 side, respectively. It can be regarded as a translation.
Therefore, if the distances Ld1 and Ld2 from the imaginary spot Q to the imaginary spots Q1 and Q2 in the normal direction Zg of the double-sided half mirror 15 are calculated, the imaginary spot between the imaginary spots Q1 and Q2 in the Z direction from these Ld1 and Ld2 The interval ΔZ can be obtained.
両面ハーフミラー15から出射された第1および第2の出力光S1,S2は、主光線Sが両面ハーフミラー15の法線方向Zgに沿って、検出面I側あるいは集光レンズ14側にそれぞれ平行移動したものと見なすことができる。
したがって、両面ハーフミラー15の法線方向Zgにおける、虚スポットQから虚スポットQ1,Q2までの距離Ld1,Ld2を算出すれば、これらLd1,Ld2からZ方向における虚スポットQ1,Q2間の虚スポット間隔ΔZを求めことができる。 [Imaginary spot interval ΔZ in the Z direction]
The first and second output lights S1 and S2 emitted from the double-
Therefore, if the distances Ld1 and Ld2 from the imaginary spot Q to the imaginary spots Q1 and Q2 in the normal direction Zg of the double-
まず、図3および図4を参照して、光の平行移動について説明する。
図3に示すように、光Saを集光する集光レンズCとその結像点Paとの間に、屈折率の高い両面ハーフミラー15などの平行平板からなる透光性を持つ媒体Gを挿入した場合、光Saが平行移動した状態となり、媒体Gを透過した光Sbの結像点は、媒体Gの法線方向Zgに沿って結像点Paから結像点Pbまで延長されることになる。 First, the parallel movement of light will be described with reference to FIGS.
As shown in FIG. 3, a medium G having translucency composed of parallel flat plates such as a double-sided half mirror 15 having a high refractive index is disposed between a condensing lens C for condensing the light Sa and its imaging point Pa. When inserted, the light Sa is translated, and the imaging point of the light Sb transmitted through the medium G is extended from the imaging point Pa to the imaging point Pb along the normal direction Zg of the medium G. become.
図3に示すように、光Saを集光する集光レンズCとその結像点Paとの間に、屈折率の高い両面ハーフミラー15などの平行平板からなる透光性を持つ媒体Gを挿入した場合、光Saが平行移動した状態となり、媒体Gを透過した光Sbの結像点は、媒体Gの法線方向Zgに沿って結像点Paから結像点Pbまで延長されることになる。 First, the parallel movement of light will be described with reference to FIGS.
As shown in FIG. 3, a medium G having translucency composed of parallel flat plates such as a double-
ここで、図4に示すように、媒体Gの相対屈折率をnとし、媒体Gの厚さをtとし、媒体Gに対する光Saの入射角をθ1とし、媒体G内部での屈折角をθ2とし、法線方向Zgに沿った光Saから光Sbへの平行移動距離をdとした場合、媒体Gの出射面上における、媒体Gに対する光Saの入射位置と媒体Gからの光Sbの出射位置との距離kは、次の式(5)で表され、平行移動距離dは次の式(6)で求められる。
Here, as shown in FIG. 4, the relative refractive index of the medium G is n, the thickness of the medium G is t, the incident angle of the light Sa to the medium G is θ1, and the refraction angle inside the medium G is θ2. Where the parallel movement distance from the light Sa to the light Sb along the normal direction Zg is d, the incident position of the light Sa on the medium G on the emission surface of the medium G and the emission of the light Sb from the medium G The distance k to the position is expressed by the following equation (5), and the parallel movement distance d is determined by the following equation (6).
次に、図5を参照して、第1の出力光S1の平行移動について説明する。図5では、理解を容易とするため、光軸Oを傾け、両面ハーフミラー15の法線を基準(水平)としている。
前述した光の平行移動と同様にして、両面ハーフミラー15から出射された第1の出力光S1は、図5に示すように、両面ハーフミラー15に入射した主光線Sが、両面ハーフミラー15の法線方向Zgに沿って、平行移動したものと見なすことができる。 Next, the parallel movement of the first output light S1 will be described with reference to FIG. In FIG. 5, for easy understanding, the optical axis O is inclined and the normal line of the double-sided half mirror 15 is used as a reference (horizontal).
Similar to the parallel movement of the light described above, the first output light S1 emitted from the double-sided half mirror 15 has a principal ray S incident on the double-sided half mirror 15 as shown in FIG. It can be considered that it is translated along the normal direction Zg.
前述した光の平行移動と同様にして、両面ハーフミラー15から出射された第1の出力光S1は、図5に示すように、両面ハーフミラー15に入射した主光線Sが、両面ハーフミラー15の法線方向Zgに沿って、平行移動したものと見なすことができる。 Next, the parallel movement of the first output light S1 will be described with reference to FIG. In FIG. 5, for easy understanding, the optical axis O is inclined and the normal line of the double-
Similar to the parallel movement of the light described above, the first output light S1 emitted from the double-
まず、入射角θ1で第1面15A上の点Aから入射した主光線Sは、法線方向Zgに対して屈折角θ2の角度で屈折した後、両面ハーフミラー15内部を透過して、第2面15B上の点Cから第1の出力光S1として出射する。
First, the principal ray S incident from the point A on the first surface 15A at the incident angle θ1 is refracted at an angle of refraction angle θ2 with respect to the normal direction Zg, and then passes through the inside of the double-sided half mirror 15, The light is emitted from the point C on the second surface 15B as the first output light S1.
この際、点Aを通過する法線が第2面15Bと交差する位置を点Bとし、第1の出力光S1を第1面15A側に延長した場合に第1面15Aと交差する位置を点A’’とし、線分A’’-Cが線分A-Bと交差する位置を点A’とした場合、点A’を通過して点Cから出射する第1の出力光S1は、点Aに入射した主光線Sの直進光S1’が、法線方向Zgに沿って検出面I側に点A’まで平行移動したものと見なすことができ、線分A-A’の距離d1が第1の出力光S1の平行移動距離に相当する。
At this time, the position where the normal passing through the point A intersects with the second surface 15B is defined as a point B, and the position where the first output light S1 extends to the first surface 15A side intersects with the first surface 15A. When the point A ″ is the point A ′ and the position where the line A ″ -C intersects the line AB is the point A ′, the first output light S1 passing through the point A ′ and emitted from the point C is , The straight traveling light S1 ′ of the principal ray S incident on the point A can be regarded as being translated to the point A ′ on the detection surface I side along the normal direction Zg, and the distance of the line segment AA ′. d1 corresponds to the parallel movement distance of the first output light S1.
ここで、三角形ABCと三角形A’BCは、辺BCを共通としているため、次の式(7)の関係が得られる。また、両面ハーフミラー15の相対屈折率をnとし,両面ハーフミラー15の厚さをtとして、スネルの法則により、式(7)のθ2をθ1で置換した場合、線分A-A’の距離d1は式(8)で求められる。
Here, since the triangle ABC and the triangle A′BC share the side BC, the relationship of the following equation (7) is obtained. Further, when the relative refractive index of the double-sided half mirror 15 is n, the thickness of the double-sided half mirror 15 is t, and θ2 in equation (7) is replaced by θ1 according to Snell's law, the line segment AA ′ The distance d1 is obtained by Expression (8).
したがって、このような第1の出力光S1の平行移動により、主光線Sの光路長が線分A’’-A’の長さLd1だけ検出面I側に短縮されたことを示しており、見かけ上、虚スポットQが法線方向Zgに沿って距離d1だけ検出面I側に虚スポットQ1まで移動したことを示している。このLd1は式(8)で求めた距離d1から次の式(9)で求められる。
Accordingly, it is shown that the optical path length of the chief ray S is shortened to the detection surface I side by the length Ld1 of the line segment A ″ -A ′ by such parallel movement of the first output light S1. Apparently, the imaginary spot Q has moved to the imaginary spot Q1 on the detection surface I side by a distance d1 along the normal direction Zg. This Ld1 is obtained by the following equation (9) from the distance d1 obtained by the equation (8).
次に、図6を参照して、第2の出力光S2の平行移動について説明する。図6では、理解を容易とするため、光軸Oを傾け、両面ハーフミラー15の法線を基準としている。
前述した第1の出力光S1の平行移動と同様にして、両面ハーフミラー15から出射された第2の出力光S2は、図6に示すように、両面ハーフミラー15に入射した主光線Sが、両面ハーフミラー15の法線方向Zgに沿って、平行移動したものと見なすことができる。 Next, the parallel movement of the second output light S2 will be described with reference to FIG. In FIG. 6, for easy understanding, the optical axis O is inclined and the normal line of the double-sided half mirror 15 is used as a reference.
Similar to the parallel movement of the first output light S1 described above, the second output light S2 emitted from the double-sided half mirror 15 has a principal ray S incident on the double-sided half mirror 15 as shown in FIG. It can be considered that the double-sided half mirror 15 is translated along the normal direction Zg.
前述した第1の出力光S1の平行移動と同様にして、両面ハーフミラー15から出射された第2の出力光S2は、図6に示すように、両面ハーフミラー15に入射した主光線Sが、両面ハーフミラー15の法線方向Zgに沿って、平行移動したものと見なすことができる。 Next, the parallel movement of the second output light S2 will be described with reference to FIG. In FIG. 6, for easy understanding, the optical axis O is inclined and the normal line of the double-
Similar to the parallel movement of the first output light S1 described above, the second output light S2 emitted from the double-
まず、入射角θ1で第1面15A上の点Aから入射した主光線Sは、法線方向Zgに対して屈折角θ2の角度で屈折した後、両面ハーフミラー15内部を透過して、第2面15Bおよび第1面15Aで反射し、第2面15B上の点Eから第1の出力光S1として出射する。
First, the principal ray S incident from the point A on the first surface 15A at the incident angle θ1 is refracted at an angle of refraction angle θ2 with respect to the normal direction Zg, and then passes through the inside of the double-sided half mirror 15, The light is reflected by the second surface 15B and the first surface 15A, and is emitted from the point E on the second surface 15B as the first output light S1.
この際、点Aから点Eまでの経路は、厚さ3tの両面ハーフミラー15内部を反射せずに透過した経路と等しいものと見なすことかできる。したがって、点Aから点Eまでの経路を第1面15Aの左側に展開し、第1面15Aから距離2tだけ離れた仮想第1面上で、これら展開経路と点Aを通過する法線とが交差する点を点Dとし、第2の出力光S2を仮想第1面側に延長した場合に点Aを通過する法線と交差する点を点D’とした場合、点D’を通過する第2の出力光S2は、点Dに入射した主光線S’の直進光S2’が、法線方向Zgに沿って検出面I側に平行移動したものと見なすことができ、線分D-D’が第2の出力光S2の平行移動距離d2に相当する。
At this time, the path from the point A to the point E can be regarded as the same as the path that passes through the double-sided half mirror 15 having a thickness of 3 t without being reflected. Therefore, the path from the point A to the point E is developed on the left side of the first surface 15A, and the normal line passing through the development path and the point A on the virtual first surface separated by the distance 2t from the first surface 15A Is the point D, and when the second output light S2 is extended to the virtual first surface side, the point that intersects the normal passing through the point A is the point D ', and the point D' is passed. The second output light S2 can be regarded as the straight light S2 ′ of the principal ray S ′ incident on the point D being translated to the detection surface I side along the normal direction Zg. −D ′ corresponds to the parallel movement distance d2 of the second output light S2.
ここで、三角形DBEと三角形D’BEは、辺BEを共通としているため、次の式(10)の関係が得られる。また、両面ハーフミラー15の相対屈折率をnとし,両面ハーフミラー15の厚さをtとして、スネルの法則により、式(10)のθ2をθ1で置換した場合、線分D-D’の距離d2は、式(10)に基づき式(11)で求められる。
Here, since the triangle DBE and the triangle D′ BE share the side BE, the relationship of the following equation (10) is obtained. Further, when the relative refractive index of the double-sided half mirror 15 is n, the thickness of the double-sided half mirror 15 is t, and θ2 in Equation (10) is replaced by θ1 according to Snell's law, the line DD ′ The distance d2 is obtained by Expression (11) based on Expression (10).
したがって、第2の出力光S2を仮想第1面側に延長した際に、仮想第1面と交差する点を点D’’とした場合、このような第2の出力光S2の平行移動により、主光線Sの光路長が線分D’’-D’の長さLd2’だけ検出面I側に短縮されたことを示しており、見かけ上、虚スポットQが法線方向Zgに沿って距離d2だけ検出面I側に虚スポットQ2まで移動したことを示している。このLd2’は式(11)で求めた距離d2から次の式(12)で求められる。
Therefore, when the second output light S2 is extended to the virtual first surface side and the point intersecting with the virtual first surface is a point D ″, the parallel movement of the second output light S2 is performed. This shows that the optical path length of the chief ray S has been shortened to the detection surface I side by the length Ld2 ′ of the line segment D ″ -D ′, and the imaginary spot Q apparently extends along the normal direction Zg. This shows that the distance d2 has moved to the imaginary spot Q2 on the detection surface I side. This Ld2 ′ is obtained by the following equation (12) from the distance d2 obtained by the equation (11).
ここで、この距離Ld2’には、仮想第1面まで2t分だけ展開した展開距離2t/cosθ1が含まれている。このため、第2の出力光S2を仮想第1面側に延長した場合に第1面15Bと交差する点を点D’’’とした場合、線分D’-D’’’だけ、主光線Sの光路長が集光レンズ14側に延長したものと見なすことができ、この光路長Ld2は、次の式(13)で求められる。
Here, the distance Ld2 ′ includes a developed distance 2t / cos θ1 developed by 2t up to the virtual first surface. Therefore, when the second output light S2 is extended to the virtual first surface side and the point intersecting with the first surface 15B is a point D ′ ″, only the line segment D′−D ′ ″ It can be considered that the optical path length of the light beam S extends to the condensing lens 14 side, and this optical path length Ld2 is obtained by the following equation (13).
したがって、Z方向における虚スポットQ1,Q2の間隔Δzは、第1の出力光S1の光路差Ld1と第2の出力光S2の光路差Ld2に基づいて、次の式(14)で求められる。
Therefore, the interval Δz between the imaginary spots Q1 and Q2 in the Z direction is obtained by the following equation (14) based on the optical path difference Ld1 of the first output light S1 and the optical path difference Ld2 of the second output light S2.
[虚スポット間隔ΔX,ΔZとピッチpとの関係]
次に、図7を参照して、虚スポットQ1,Q2の間隔ΔX,ΔZと、検出面I上に生じる干渉縞のピッチpとの関係について説明する。図7では、理解を容易とするため、光軸Oを基準(水平)とし、両面ハーフミラー15は無視するものとする。 [Relationship between imaginary spot intervals ΔX, ΔZ and pitch p]
Next, with reference to FIG. 7, the relationship between the intervals ΔX, ΔZ between the imaginary spots Q1, Q2 and the pitch p of the interference fringes generated on the detection surface I will be described. In FIG. 7, for easy understanding, the optical axis O is the reference (horizontal), and the double-sided half mirror 15 is ignored.
次に、図7を参照して、虚スポットQ1,Q2の間隔ΔX,ΔZと、検出面I上に生じる干渉縞のピッチpとの関係について説明する。図7では、理解を容易とするため、光軸Oを基準(水平)とし、両面ハーフミラー15は無視するものとする。 [Relationship between imaginary spot intervals ΔX, ΔZ and pitch p]
Next, with reference to FIG. 7, the relationship between the intervals ΔX, ΔZ between the imaginary spots Q1, Q2 and the pitch p of the interference fringes generated on the detection surface I will be described. In FIG. 7, for easy understanding, the optical axis O is the reference (horizontal), and the double-
図7において、虚スポットQ1,Q2は、X方向に間隔ΔXだけ離れるとともに、Z方向に間隔ΔZだけ離れて位置している。ここで、虚スポットQ1からの第1の出力光S1と、虚スポットQ2からの第2の出力光S2が光検出素子16の検出面I上に到達した到達点をVとし、虚スポットQ1を通過するX方向の線と虚スポットQ2を通過するZ方向の線との交点を点Dとし、線分Q1-Dの中間点D0からZ方向に伸ばした線と検出面Iとが交わる点をV0とし、検出面I上でY方向に沿ったV0からVまでの距離をPとし、虚スポットQ1から検出面Iまでの距離をcとする。
In FIG. 7, the imaginary spots Q1 and Q2 are separated by an interval ΔX in the X direction and are separated by an interval ΔZ in the Z direction. Here, the arrival point at which the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 have reached the detection surface I of the light detection element 16 is defined as V, and the imaginary spot Q1 is defined as The intersection of the X-direction line passing through and the Z-direction line passing through the imaginary spot Q2 is defined as a point D, and a point where the line extending from the intermediate point D0 of the line segment Q1-D and extending in the Z direction intersects the detection surface I. It is assumed that V0 is a distance from V0 to V along the Y direction on the detection surface I, and P is a distance from the imaginary spot Q1 to the detection surface I.
第1の出力光S1に関する虚スポットQ1から到達点Vまでの光路長L1は、三平方の定理により、次の式(15)で求められる。この際、距離cに比較して間隔Δxが非常に小さく、Z方向に対する線分D0-Vの傾きΦに代表される第1の出力光S1および第2の出力光S2の傾きが非常に小さいため、光路長L1は次の式(16)のように近似できる。
The optical path length L1 from the imaginary spot Q1 to the arrival point V with respect to the first output light S1 is obtained by the following equation (15) by the three-square theorem. At this time, the interval Δx is very small compared to the distance c, and the slopes of the first output light S1 and the second output light S2 represented by the slope Φ of the line segment D0-V with respect to the Z direction are very small. Therefore, the optical path length L1 can be approximated as the following equation (16).
一方、線分Q2-Vと線分Q1-Dとの交点を点Q2’とした場合、第2の出力光S2に関する虚スポットQ2から到達点Vまでの光路長L2は、線分Q2-Q2’の光路長L21と線分Q2’-Vの光路長L22との和で求められる。
まず、光路長L21については、線分D-Q2’の距離をx’とした場合、前述した式(16)と同様にして、次の式(17)により求められる。
On the other hand, when the intersection of the line segment Q2-V and the line segment Q1-D is a point Q2 ', the optical path length L2 from the imaginary spot Q2 to the arrival point V regarding the second output light S2 is the line segment Q2-Q2 'And the sum of the optical path length L22 of the line segment Q2'-V.
First, the optical path length L21 is obtained by the following equation (17) in the same manner as the equation (16) described above, where the distance of the line segment DQ2 ′ is x ′.
まず、光路長L21については、線分D-Q2’の距離をx’とした場合、前述した式(16)と同様にして、次の式(17)により求められる。
First, the optical path length L21 is obtained by the following equation (17) in the same manner as the equation (16) described above, where the distance of the line segment DQ2 ′ is x ′.
ここで、前述したように、線分Q2-Q2’の傾きΦが非常に小さく、距離x’/間隔ΔzすなわちtanΦが極めて小さいため、式(17)の右辺第2項は非常に小さい値となる。このため、結果として光路長L21はΔzで近似できることになる。
一方、光路長L22は、光路長L1と同様は、三平方の定理により、次の式(18)で求められる。
Here, as described above, since the slope Φ of the line segment Q2-Q2 ′ is very small and the distance x ′ / interval Δz, that is, tan Φ is extremely small, the second term on the right side of the equation (17) is a very small value. Become. Therefore, as a result, the optical path length L21 can be approximated by Δz.
On the other hand, the optical path length L22 is obtained by the following equation (18) by the square theorem, similarly to the optical path length L1.
一方、光路長L22は、光路長L1と同様は、三平方の定理により、次の式(18)で求められる。
On the other hand, the optical path length L22 is obtained by the following equation (18) by the square theorem, similarly to the optical path length L1.
これにより、光路長L2は次の式(19)で求められ、虚スポットQ1からの第1の出力光S1と、虚スポットQ2からの第2の出力光S2との光路差ΔLは、次の式(20)で求められる。
Thereby, the optical path length L2 is obtained by the following equation (19), and the optical path difference ΔL between the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 is It is calculated | required by Formula (20).
検出面I上では、この光路差ΔLにより干渉縞が生じ、具体的には、光路差ΔLが光の波長λの整数m(mは、0以上の整数)倍となる場合、検出面Iにおいて明線が生じる。また、光路差ΔLのうち間隔Δzは一定値であり、この値は、干渉縞の初期位相にのみ影響を与えるだけで干渉縞ピッチpには影響を与えるものではない。
On the detection surface I, interference fringes are generated due to this optical path difference ΔL. Specifically, when the optical path difference ΔL is an integer m (m is an integer of 0 or more) times the wavelength λ of light, A bright line appears. In addition, the interval Δz of the optical path difference ΔL is a constant value, and this value only affects the initial phase of the interference fringes and does not affect the interference fringe pitch p.
したがって、検出面I上に生じた各明線のうち、隣接する明線の間隔は干渉縞ピッチpとなり、その値はm=1の場合に相当する。よって、検出面I上に生じた干渉縞の干渉縞ピッチpは、式(20)において光路差ΔL=λとし、間隔Δzを無視することにより、次の式(21)で求められる。
Therefore, among the bright lines generated on the detection surface I, the interval between adjacent bright lines is the interference fringe pitch p, and the value corresponds to the case of m = 1. Therefore, the interference fringe pitch p of the interference fringes generated on the detection surface I is obtained by the following equation (21) by setting the optical path difference ΔL = λ in the equation (20) and ignoring the interval Δz.
一方、図8に示すように、物体Tから主点Mすなわち集光レンズ14の位置までの対物距離をaとし、主点から虚スポットQまでの距離をbとし、集光レンズ14の焦点距離をfとした場合、これらの関係は、結像の公式(レンズの公式)により、次の式(22)で表される。
On the other hand, as shown in FIG. 8, the objective distance from the object T to the principal point M, that is, the position of the condenser lens 14 is a, the distance from the principal point to the imaginary spot Q is b, and the focal length of the condenser lens 14 Where f is expressed by the following formula (22) by the imaging formula (lens formula).
したがって、主点から虚スポットQまでの距離bと虚スポットQ1から検出面Iまでの距離cの和を距離g(g=一定)としてc=g-bとし、これに式(22)から求められる距離bを代入すると、前述した式(21)は次の式(23)となる。したがって、式(23から、物体Tから主点Mすなわち集光レンズ14の位置までの対物距離aは、次の式(24)で求められることになる。
Therefore, the sum of the distance b from the principal point to the imaginary spot Q and the distance c from the imaginary spot Q1 to the detection surface I is set as a distance g (g = constant), and c = g−b, which is obtained from the equation (22). When the distance b to be substituted is substituted, the above-described equation (21) becomes the following equation (23). Therefore, from the equation (23, the objective distance a from the object T to the principal point M, that is, the position of the condenser lens 14, is obtained by the following equation (24).
図9の画像例に示すように、干渉縞は、輝度の高い明線と輝度の低い暗線とが縞状に繰り返されて形成されている。したがって、互いに隣接する明線(または暗線)の間隔が干渉縞ピッチpに相当する。
As shown in the image example of FIG. 9, the interference fringes are formed by repeating bright lines with high luminance and dark lines with low luminance in a stripe shape. Accordingly, the interval between adjacent bright lines (or dark lines) corresponds to the interference fringe pitch p.
図10の解析例では、横軸が干渉縞に直行するX方向に沿った画像のピクセル位置[pic]を示し、縦軸が各ピクセル位置における光強度(無単位)である。得られた検出結果は、ほぼ正弦波形状をなしており、そのピーク位置が明線に相当している。したがって、ピーク位置間に存在するピクセル数から干渉縞ピッチpを示す実際の距離を算出できる。
10, the horizontal axis indicates the pixel position [pic] of the image along the X direction orthogonal to the interference fringes, and the vertical axis indicates the light intensity (no unit) at each pixel position. The obtained detection result has a substantially sine wave shape, and its peak position corresponds to a bright line. Therefore, the actual distance indicating the interference fringe pitch p can be calculated from the number of pixels existing between the peak positions.
[第1の実施の形態の効果]
このように、本実施の形態は、物体Tからの反射光を集光レンズ14により虚スポットQに一旦集光させた後、両面ハーフミラー15により2つの出力光に分離して、反射光が入射される第1面と対向する第2面から出力し、これら2つの出力光により検出面Iに生じた干渉縞を光検出素子16で検出し、得られた検出結果を演算処理して干渉縞のピッチを抽出し、距離算出部17でこのピッチに基づいて集光レンズ14から物体Tまでの対物距離aを算出するようにしたものである。 [Effect of the first embodiment]
As described above, in the present embodiment, the reflected light from the object T is once condensed on the imaginary spot Q by thecondenser lens 14, and then separated into two output lights by the double-sided half mirror 15, and the reflected light is The light is output from the second surface opposite to the incident first surface, the interference fringes generated on the detection surface I by these two output lights are detected by the light detection element 16, and the obtained detection results are subjected to arithmetic processing to cause interference. The fringe pitch is extracted, and the distance calculation unit 17 calculates the objective distance a from the condenser lens 14 to the object T based on this pitch.
このように、本実施の形態は、物体Tからの反射光を集光レンズ14により虚スポットQに一旦集光させた後、両面ハーフミラー15により2つの出力光に分離して、反射光が入射される第1面と対向する第2面から出力し、これら2つの出力光により検出面Iに生じた干渉縞を光検出素子16で検出し、得られた検出結果を演算処理して干渉縞のピッチを抽出し、距離算出部17でこのピッチに基づいて集光レンズ14から物体Tまでの対物距離aを算出するようにしたものである。 [Effect of the first embodiment]
As described above, in the present embodiment, the reflected light from the object T is once condensed on the imaginary spot Q by the
これにより、両面ハーフミラー15という極めて簡素な既存の光学要素で、物体Tからの反射光が、仮想的な集光点である虚スポットQ1,Q2の位置が互いに異なる2つの出力光S1,S2に分離され、これら出力光S1,S2により対物距離aに応じてピッチpが変化する干渉縞が検出面Iに発生する。
したがって、従来の精密な研磨加工を要する多重焦点レンズや球体レンズを用いる必要がなくなり、高価な光学系レンズやその精密な組み立てを省くことができる。このため、比較的安価なコストで、物体Tまでの対物距離aを正確に測定することができる距離測定装置を実現することが可能となる。 As a result, the output light S1 and S2 of the output light S1 and S2 that are different from each other in the positions of the imaginary spots Q1 and Q2, which are virtual condensing points, are reflected light from the object T by a very simple existing optical element called the double-sided half mirror 15. Interference fringes whose pitch p changes according to the objective distance a are generated on the detection surface I by these output lights S1 and S2.
Therefore, it is not necessary to use a conventional multifocal lens or spherical lens that requires precise polishing, and an expensive optical lens and its precise assembly can be omitted. For this reason, it is possible to realize a distance measuring device that can accurately measure the objective distance a to the object T at a relatively low cost.
したがって、従来の精密な研磨加工を要する多重焦点レンズや球体レンズを用いる必要がなくなり、高価な光学系レンズやその精密な組み立てを省くことができる。このため、比較的安価なコストで、物体Tまでの対物距離aを正確に測定することができる距離測定装置を実現することが可能となる。 As a result, the output light S1 and S2 of the output light S1 and S2 that are different from each other in the positions of the imaginary spots Q1 and Q2, which are virtual condensing points, are reflected light from the object T by a very simple existing optical element called the double-
Therefore, it is not necessary to use a conventional multifocal lens or spherical lens that requires precise polishing, and an expensive optical lens and its precise assembly can be omitted. For this reason, it is possible to realize a distance measuring device that can accurately measure the objective distance a to the object T at a relatively low cost.
また、本実施の形態は、両面ハーフミラー15に、それぞれ半透光性を持つ平行配置された2つの第1面15Aおよび第2面15Bを設け、虚スポットQに一旦集光した反射光のうち、第1面15Aを透過した光を第2面15Bで反射させずに透過させて第1の出力光S1として出力する機能と、第1面15Aを透過した光を第2面15Bで反射した後に第1面15Aで再び反射し第2面15Bを透過させて第2の出力光S2として出力するようにしたものである。
In the present embodiment, the double-sided half mirror 15 is provided with two first and second surfaces 15A and 15B arranged in parallel, each having semi-translucency, and the reflected light once condensed on the imaginary spot Q is provided. Among them, the light transmitted through the first surface 15A is transmitted without being reflected by the second surface 15B and is output as the first output light S1, and the light transmitted through the first surface 15A is reflected by the second surface 15B. After that, the light is reflected again by the first surface 15A, transmitted through the second surface 15B, and output as the second output light S2.
これにより、両面ハーフミラー15という極めて簡素な光学要素で、虚スポットQからの反射光Sを、虚スポットQ1からの第1の出力光S1と虚スポットQ2からの第2の出力光S2とに容易に分離させることができ、効率よく干渉縞を発生させることができる。
また、干渉縞は正弦波形状となるため、干渉縞ピッチpの測定が容易となるとともに、干渉縞の局在化、すなわち周期的な特定の距離近辺にのみ干渉縞が現れる現象が発生しないため、対物距離aの測定スパンを広くすることができる。さらに、干渉縞ピッチpが検出面I上で一定となるため、光検出素子16の検出結果を補正する必要がなく、演算処理を簡素化できるとともに干渉縞ピッチpの測定誤差を低減できる。 Thereby, the reflected light S from the imaginary spot Q is converted into the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 with a very simple optical element called the double-sided half mirror 15. They can be easily separated and interference fringes can be generated efficiently.
Further, since the interference fringes have a sine wave shape, the interference fringe pitch p can be easily measured, and the interference fringes are not localized, that is, the phenomenon in which the interference fringes appear only in the vicinity of a specific periodic distance does not occur. The measurement span of the objective distance a can be widened. Furthermore, since the interference fringe pitch p is constant on the detection surface I, there is no need to correct the detection result of thelight detection element 16, and the arithmetic processing can be simplified and the measurement error of the interference fringe pitch p can be reduced.
また、干渉縞は正弦波形状となるため、干渉縞ピッチpの測定が容易となるとともに、干渉縞の局在化、すなわち周期的な特定の距離近辺にのみ干渉縞が現れる現象が発生しないため、対物距離aの測定スパンを広くすることができる。さらに、干渉縞ピッチpが検出面I上で一定となるため、光検出素子16の検出結果を補正する必要がなく、演算処理を簡素化できるとともに干渉縞ピッチpの測定誤差を低減できる。 Thereby, the reflected light S from the imaginary spot Q is converted into the first output light S1 from the imaginary spot Q1 and the second output light S2 from the imaginary spot Q2 with a very simple optical element called the double-
Further, since the interference fringes have a sine wave shape, the interference fringe pitch p can be easily measured, and the interference fringes are not localized, that is, the phenomenon in which the interference fringes appear only in the vicinity of a specific periodic distance does not occur. The measurement span of the objective distance a can be widened. Furthermore, since the interference fringe pitch p is constant on the detection surface I, there is no need to correct the detection result of the
[第2の実施の形態]
次に、図11を参照して、本発明の第2の実施の形態にかかる距離測定装置10について説明する。
本実施の形態では、前述した第1の実施の形態において、集光光学系に対物レンズ20を設け、対物レンズ20と集光レンズ14との間の区間において、物体Tからの反射光を平行光に変換する場合について説明する。 [Second Embodiment]
Next, with reference to FIG. 11, thedistance measuring apparatus 10 concerning the 2nd Embodiment of this invention is demonstrated.
In the present embodiment, theobjective lens 20 is provided in the condensing optical system in the first embodiment described above, and the reflected light from the object T is parallel in the section between the objective lens 20 and the condenser lens 14. The case of converting to light will be described.
次に、図11を参照して、本発明の第2の実施の形態にかかる距離測定装置10について説明する。
本実施の形態では、前述した第1の実施の形態において、集光光学系に対物レンズ20を設け、対物レンズ20と集光レンズ14との間の区間において、物体Tからの反射光を平行光に変換する場合について説明する。 [Second Embodiment]
Next, with reference to FIG. 11, the
In the present embodiment, the
本実施の形態において、対物レンズ20は、物体Tからの反射光を平行光に変換して、集光レンズ14に出力する機能を有している。
図11の例では、対物レンズ20と集光レンズ14との間にビームスプリッタ13が配置されている。これにより、光源11から発せられた光は、光源レンズ12で平行光に変換された後、ビームスプリッタ13で反射され、この後、対物レンズ20により集光されて物体Tに照射される。 In the present embodiment, theobjective lens 20 has a function of converting the reflected light from the object T into parallel light and outputting it to the condenser lens 14.
In the example of FIG. 11, thebeam splitter 13 is disposed between the objective lens 20 and the condenser lens 14. Thereby, the light emitted from the light source 11 is converted into parallel light by the light source lens 12, reflected by the beam splitter 13, and then condensed by the objective lens 20 and applied to the object T.
図11の例では、対物レンズ20と集光レンズ14との間にビームスプリッタ13が配置されている。これにより、光源11から発せられた光は、光源レンズ12で平行光に変換された後、ビームスプリッタ13で反射され、この後、対物レンズ20により集光されて物体Tに照射される。 In the present embodiment, the
In the example of FIG. 11, the
また、物体Tからの反射光は、対物レンズ20で平行光に変換され、ビームスプリッタ13を通過して集光レンズ14により虚スポットQに一旦集光させた後、虚スポットQから広がり始めた反射光が両面ハーフミラー15を通過して検出面Iに照射される。
The reflected light from the object T is converted into parallel light by the objective lens 20, passes through the beam splitter 13, and is once condensed on the imaginary spot Q by the condenser lens 14, and then starts to spread from the imaginary spot Q. The reflected light passes through the double-sided half mirror 15 and is applied to the detection surface I.
これにより、第1の実施の形態と同様、対物レンズ20から物体Tまでの対物距離に応じてピッチが変化する干渉縞が検出面I上に生じるため、このピッチから対物距離を算出することができる。
As a result, as in the first embodiment, an interference fringe whose pitch changes according to the objective distance from the objective lens 20 to the object T is generated on the detection surface I. Therefore, the objective distance can be calculated from this pitch. it can.
図12に示すグラフは、本実施の形態に基づいて、対物距離aと干渉縞ピッチpとの関係をシミュレーションにより求めた。この際、対物レンズ20の焦点距離をf’=30mmとし、集光レンズ14の焦点距離をf=30mmとし、集光レンズ14から光検出素子16までの距離をL=40mmとした。
図12のグラフによれば、対物距離aの増加に応じて干渉縞ピッチpが単調増加していることがわかる。 In the graph shown in FIG. 12, the relationship between the objective distance a and the interference fringe pitch p is obtained by simulation based on the present embodiment. At this time, the focal length of theobjective lens 20 was f ′ = 30 mm, the focal length of the condenser lens 14 was f = 30 mm, and the distance from the condenser lens 14 to the light detection element 16 was L = 40 mm.
From the graph of FIG. 12, it can be seen that the interference fringe pitch p monotonously increases as the object distance a increases.
図12のグラフによれば、対物距離aの増加に応じて干渉縞ピッチpが単調増加していることがわかる。 In the graph shown in FIG. 12, the relationship between the objective distance a and the interference fringe pitch p is obtained by simulation based on the present embodiment. At this time, the focal length of the
From the graph of FIG. 12, it can be seen that the interference fringe pitch p monotonously increases as the object distance a increases.
[第2の実施の形態の効果]
このように、本実施の形態は、集光光学系に対物レンズ20を設け、対物レンズ20と集光レンズ14との間の区間において、物体Tからの反射光を平行光に変換するようにしたので、物体Tまでの対物距離aが変化しても、その対物距離aに応じた焦点距離を持つ対物レンズ20に取り換えることにより、対物レンズ20から検出面Iまでの区間においては、光路が一定となる。
このため、広範囲の対物距離aに対応することができ、測定レンジを大幅に拡大することが可能となる。 [Effect of the second embodiment]
As described above, in the present embodiment, theobjective lens 20 is provided in the condensing optical system, and the reflected light from the object T is converted into parallel light in the section between the objective lens 20 and the condensing lens 14. Therefore, even if the objective distance a to the object T changes, the optical path is changed in the section from the objective lens 20 to the detection surface I by replacing the objective lens 20 with a focal length corresponding to the objective distance a. It becomes constant.
For this reason, it is possible to deal with a wide range of objective distances a, and the measurement range can be greatly expanded.
このように、本実施の形態は、集光光学系に対物レンズ20を設け、対物レンズ20と集光レンズ14との間の区間において、物体Tからの反射光を平行光に変換するようにしたので、物体Tまでの対物距離aが変化しても、その対物距離aに応じた焦点距離を持つ対物レンズ20に取り換えることにより、対物レンズ20から検出面Iまでの区間においては、光路が一定となる。
このため、広範囲の対物距離aに対応することができ、測定レンジを大幅に拡大することが可能となる。 [Effect of the second embodiment]
As described above, in the present embodiment, the
For this reason, it is possible to deal with a wide range of objective distances a, and the measurement range can be greatly expanded.
[実施の形態の拡張]
以上、実施形態を参照して本発明を説明したが、本発明は上記実施形態に限定されるものではない。本発明の構成や詳細には、本発明のスコープ内で当業者が理解しうる様々な変更をすることができる。また、各実施形態については、矛盾しない範囲で任意に組み合わせて実施することができる。 [Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, each embodiment can be implemented in any combination within a consistent range.
以上、実施形態を参照して本発明を説明したが、本発明は上記実施形態に限定されるものではない。本発明の構成や詳細には、本発明のスコープ内で当業者が理解しうる様々な変更をすることができる。また、各実施形態については、矛盾しない範囲で任意に組み合わせて実施することができる。 [Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, each embodiment can be implemented in any combination within a consistent range.
10…距離測定装置、14…集光レンズ、15…両面ハーフミラー、16…光検出素子、17…距離算出部、T…物体、Q…虚スポット、I…検出面、a…対物距離、p…干渉縞ピッチ。
DESCRIPTION OF SYMBOLS 10 ... Distance measuring device, 14 ... Condensing lens, 15 ... Double-sided half mirror, 16 ... Photodetection element, 17 ... Distance calculation part, T ... Object, Q ... Imaginary spot, I ... Detection surface, a ... Objective distance, p ... interference fringe pitch.
Claims (5)
- 物体に光を照射して反射させ、その反射光に基づいて当該物体までの対物距離を測定する距離測定装置であって、
前記物体からの前記反射光を虚スポットに集光させる集光レンズと、
前記虚スポットを通過した前記反射光を内部で2つの出力光に分離して、当該反射光が入射される第1面と対向する第2面から出力する両面ハーフミラーと、
前記両面ハーフミラーからの2つの出力光により検出面に生じた干渉縞を検出する光検出素子と、
前記光検出素子で得られた検出結果を演算処理して前記干渉縞のピッチを抽出し、このピッチに基づいて前記集光レンズから前記物体までの対物距離を算出する距離算出部と
を備えることを特徴とする距離測定装置。 A distance measuring device that irradiates and reflects light on an object, and measures an objective distance to the object based on the reflected light,
A condenser lens for condensing the reflected light from the object onto an imaginary spot;
A double-sided half mirror that internally separates the reflected light that has passed through the imaginary spot into two output lights and outputs the light from a second surface opposite to the first surface on which the reflected light is incident;
A light detection element for detecting interference fringes generated on the detection surface by two output lights from the double-sided half mirror;
A distance calculation unit that calculates a detection result obtained by the light detection element, extracts a pitch of the interference fringes, and calculates an objective distance from the condenser lens to the object based on the pitch; A distance measuring device characterized by. - 請求項1に記載の距離測定装置において、
前記両面ハーフミラーは、互いに平行配置された半透光性を持つ前記第1面および前記第2面を有し、集光光学系の光軸に対して傾きを持って配置されて、前記反射光が当該第1面を透過した後に当該第2面を透過した第1の出力光と、当該反射光が当該第1面を透過した後に当該第2面で反射し、その後当該第1面で再び反射した後に当該第2面を透過した第2の出力光とを、前記2つの出力光として出力することを特徴とする距離測定装置。 The distance measuring device according to claim 1,
The double-sided half mirror has the first and second surfaces having semi-translucency arranged in parallel to each other, and is arranged with an inclination with respect to the optical axis of the condensing optical system, and the reflection The first output light that has passed through the second surface after light has passed through the first surface, and the reflected light is reflected by the second surface after passing through the first surface, and then reflected by the first surface. A distance measuring device that outputs second output light that has been reflected again and transmitted through the second surface as the two output lights. - 請求項2に記載の距離測定装置において、
前記集光レンズの焦点距離をfとし、当該集光レンズから前記虚スポットまでの距離と前記第1の出力光の仮想的な集光点である第1の虚スポットから前記検出面までの距離との和をgとし、当該第1の虚スポットと前記第2の出力光の仮想的な集光点である第2の虚スポットとの前記光軸と直交する方向における距離をΔxとし、前記両面ハーフミラーの厚さをtとし、前記両面ハーフミラーの傾き角度をθ1とし、前記両面ハーフミラーの屈折率をnとし、前記干渉縞のピッチをpとした場合、前記集光レンズから前記物体までの対物距離aを、次の式
The focal length of the condensing lens is f, the distance from the condensing lens to the imaginary spot, and the distance from the first imaginary spot, which is a virtual condensing point of the first output light, to the detection surface. And the distance between the first imaginary spot and the second imaginary spot, which is a virtual condensing point of the second output light, in the direction perpendicular to the optical axis, and Δx When the thickness of the double-sided half mirror is t, the tilt angle of the double-sided half mirror is θ1, the refractive index of the double-sided half mirror is n, and the pitch of the interference fringes is p, the object from the condenser lens The objective distance a up to
- 請求項1に記載の距離測定装置において、
前記物体からの前記反射光を平行光とする対物レンズをさらに備え、
前記集光レンズは、前記対物レンズからの前記平行光を前記虚スポットに集光させる
ことを特徴とする距離測定装置。 The distance measuring device according to claim 1,
An objective lens that collimates the reflected light from the object;
The condensing lens condenses the parallel light from the objective lens on the imaginary spot. - 物体に光を照射して反射させ、その反射光に基づいて当該物体までの対物距離を測定する距離測定方法であって、
前記物体からの前記反射光を虚スポットに集光させる集光ステップと、
前記虚スポットを通過した前記反射光を内部で2つの出力光に分離して、当該反射光が入射される第1面と対向する第2面から出力する光分離ステップと、
前記両面ハーフミラーからの2つの出力光により検出面に生じた干渉縞を検出する光検出ステップと、
前記光検出素子で得られた検出結果を演算処理して前記干渉縞のピッチを抽出し、このピッチに基づいて前記集光レンズから前記物体までの対物距離を算出する距離算出ステップと
を備えることを特徴とする距離測定方法。 A distance measurement method for irradiating and reflecting light on an object, and measuring an objective distance to the object based on the reflected light,
A condensing step of condensing the reflected light from the object into an imaginary spot;
A light separation step of internally separating the reflected light that has passed through the imaginary spot into two output lights and outputting the light from a second surface opposite to the first surface on which the reflected light is incident;
A light detection step of detecting interference fringes generated on the detection surface by two output lights from the double-sided half mirror;
A distance calculation step of calculating a detection result obtained by the light detection element to extract a pitch of the interference fringes and calculating an objective distance from the condenser lens to the object based on the pitch. A distance measuring method characterized by
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Citations (2)
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JPH0560652A (en) * | 1991-01-29 | 1993-03-12 | Asahi Optical Co Ltd | Method for measuring roof prism surface |
JP2009180562A (en) * | 2008-01-29 | 2009-08-13 | Tokyo Institute Of Technology | Device and method for measuring distance |
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JPH0560652A (en) * | 1991-01-29 | 1993-03-12 | Asahi Optical Co Ltd | Method for measuring roof prism surface |
JP2009180562A (en) * | 2008-01-29 | 2009-08-13 | Tokyo Institute Of Technology | Device and method for measuring distance |
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