JPS6119922B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an illumination optical system with constant magnification, and particularly to an illumination optical system that can maintain constant magnification of a light source image even when the distance between a light source and an image of the light source changes. .

Conventionally, the principle of an apparatus for measuring the shape of a target object as shown in FIG. 1 has been known. In this device, a beam of light emitted from a light source 1 is focused by a light transmitting lens 2 and irradiated onto a target object 3, and the irradiated image is formed at a certain angle θ with the optical axis of the light transmitting lens 2. The light is again imaged onto the detector 6 via the reflecting mirror 5 by the light receiving lens 4 having an optical axis of . Next, when the object is displaced and the point to be measured moves to the position 3', the light transmission lens 2 is moved in order to form an irradiation image on the object 3' in the same manner as above, and then the same angle θ In order to receive the reflected light from the object 3', the light receiving lens 4 and the reflecting mirror 5 are moved to form an image on the detector, and the amount of movement of the reflecting mirror 5 is measured. Measure the displacement of In such a method, the light transmitting lens 2, the light receiving lens 4, and the reflecting mirror 5 must each be given a corresponding movement amount independently, so that the mechanism of the device itself becomes large and the accompanying complexity can be avoided. do not have. Also, in order to simplify these, the light transmitting lens 2 is fixed to the device and a laser is used as the light source to illuminate the objects 3, 3' with the smallest possible spot through the light transmitting lens 2. Due to changes in the spot diameter depending on the distance, a constant size cannot be obtained when the irradiated image is formed on the detector through the light receiving lens group 4. This not only makes it difficult to obtain a constant precision, but also because the spot diameter is large. There are drawbacks such as difficulty in sensing minute changes in the object's shape at this position.

In order to keep the size of the spot irradiated onto a moving object constant, the entire light transmitting optical system may be moved integrally with the movement of the object so as to keep the distance to the object constant. In this case, moving the entire light transmitting optical system would involve moving a large device, which was not practical.

Therefore, the present invention eliminates the need to move the entire illumination device even when the distance from the light source to the image of the light source formed by the imaging optical system changes, and uses a simple configuration of moving some members. An object of the present invention is to provide an illumination optical system with constant magnification that can form a light source image of a constant size without causing any change in the size of the light source image.

The principle of the present invention will be explained below with reference to FIG. Figure 2 shows one focal position F' of lens group 7 whose focal positions are F ₁ and F' ₁ and whose focal length is f ₁ , and lens group 8 whose focal positions are F _{2 and F' 2 and} whose focal length is f 2. This shows an optical system that is a so-called afocal system in which ₁ and F ₂ match each other. Object point O placed at X from focal point F ₁
is imaged at a distance Y from the focal point F' ₂ by the afocal system. There is the following relationship between them.

Y=(f ₂ /f ₁ ) ² X Therefore, when considering the minute displacement ΔX of the object point, the movement amount ΔY of the image point O' conjugate to the object point O is also expressed as follows.

ΔY=(f ₂ /f ₁ ) ² ΔX Therefore, it can be seen that ΔY is displaced in the same direction as ΔX. Considering this in reverse, if the entire lens groups 7 and 8 are moved by a distance without moving the image point O', the position of the object point O will be changed by {(f ₁ /f ₂ ) ² -1}a to the original position. You will have to move from your location. By using the afocal system in this way, it is possible to change the image position of the object point by changing the distance between the afocal system and the object point, and the imaging magnification of the object image at this time is shown below. As shown, the amount of movement ΔX of the afocal system, ie, the amount of change in the distance between the object point and the afocal system, is always constant regardless of the amount of change. Therefore, the object point O shown in FIG.
If O' is the light source and the object point image O' is the light source image, it is possible to move the light source image by changing the distance between the light source and the afocal lens groups 7 and 8, and the light source image at this time is Since the imaging magnification is kept constant, it is possible to keep the size of the light source image constant.

m=-f ₂ /f ₁ Another great advantage is that the magnification and the amount of movement of the afocal lens group relative to the amount of movement of the object can be arbitrarily determined by the ratio of the focal lengths of each lens group 7 and 8. be.

An embodiment in which the illumination optical system with constant magnification according to the present invention is applied to a shape measuring device will be described below. The light transmitting lens system includes an auxiliary lens group 7 for forming an image of the light beam emitted from the light source 1, a light transmitting first lens group 2a having a focal length f ₁ and a light transmitting lens group 2a having a focal length f ₂ . A small light source image is formed and irradiated onto the object 3 by the second lens group 2b. The light-receiving lens system condenses the scattered light beams around an approximately constant angle θ with respect to the object irradiation axis, and forms an image of the irradiated surface on the detector 6 . The light-receiving lens system is an afocal system in which a reflecting mirror 5 is provided so that its optical axis is parallel to the optical axis of the light-transmitting lens system, and the optical axis is arranged so that the parallel optical axis coincides with the optical axis. It consists of a first lens group 4a for light reception having a focal length _f3 , a second lens group 4b having a focal length _f4 , and a lens group 8 having an auxiliary function for image formation. Furthermore, light source 1
The detector 6 and the reflector 5 are provided on the same stage and are configured to move integrally.

Now the test point of the object is ΔX from position 3 to position 3'
When the light source 1 is displaced by Δ
In order to move the light of light source 1 by ^Y in the same direction as ΔX and to form an image of the light _from light source ₁ on object 3, the light transmitting first , the focal length of the second lens group may be determined. At this time, in order to move the reflector 5 and detector 6 by the same amount ΔY as the light source, the following relationship must be satisfied: (f ₄ /f ₃ ) ² = ΔX/ΔY, where ΔX is the amount of movement of the object in the direction of the light receiving axis. What is necessary is to determine the focal length of each lens group. Therefore, if the focal length of each lens group is determined in this way, whenever the image of the light source is formed on the object, that image will also be formed on the detector.

Here, we will further describe the method for measuring the shape.
The image of the light source 1 is formed on the object to be measured (object to be detected) 3. The reflected light from the object to be measured is focused at a certain angle by the reflecting mirror 5 and the light-receiving lenses 4b, 4a, and 8 into an image near the center of the light-receiving elements arranged in a linear array on the detector 6. do as you like. Using the center point of this light-receiving element as a reference, when the object to be measured moves relative to the measuring device, the measured point changes, and the distance from the measuring device to the measured point changes, an image is formed on the light-receiving element accordingly. The position of the statue changes. At this time, by moving the reflector 5, light source 1, and detector 6 so as to receive the reflected light from the object at a certain angle, the irradiation point on the object is again near the midpoint of the initially set light receiving element group. As mentioned above, the amount of movement ΔY of the irradiation position is directly proportional to ΔX, so the amount of movement of the irradiation position can be known, and by performing this continuously, it is possible to know the unevenness from the reference, that is, the shape of the cross section. Further, by sequentially appropriately moving the object to be measured in a direction different from the movement direction, for example, at right angles, and repeating the above operation, the shape of the object can be determined three-dimensionally.

Similarly, as shown in FIG. 4, the light source 1 and the detector 6 are
is fixed, and the afocal lens groups 2a and 2b of the light transmitting lens and the afocal lens groups 4a and 4b of the light receiving lens are integrated to determine the displacement of the object point (from 3 to 3).
3'), move it in the opposite direction to the displacement direction,
Integrated afocal lens group 2a2b, 4
Even if the reflecting mirror 5 is moved in the direction opposite to the moving direction of the afocal lens group by the same amount as the moving amount of a4b, the above-mentioned logic remains unchanged and the same result can be obtained.

Next, a second embodiment is shown in FIG.

In the first embodiment shown in FIGS. 3 and 4, a light source 1, a detector 6, and a reflecting mirror 5 are integrated and moved, and afocal lens groups 2a, 2b, 4
a and 4b are integrated and moved in opposite directions by the same amount as the reflecting mirror 5, but the light source 1 and the detector 6
is a large-scale device, and since it is electrically connected, it is a member that you don't want to move.Also, providing a means to move the lens group and reflector 5 in opposite directions has a negative effect on accuracy. Therefore, the reflecting mirror 5 and the afocal lens groups 2a, 2
A method is desired in which the light source 1 and the detection means are fixed by moving the light source 1 and the light source 1 in a unified manner. For this purpose, the optical axis and Ψ must be
A fixed reflecting mirror 5 provided to have an inclination angle of
Affocal lens group 2 by providing a
a, 2b, 4a, 4b and the aforementioned movable reflecting mirror 5
It can be integrated with the robot and can be moved in the same direction.
Explaining in detail below, the functions of each member are the same as in the first embodiment, and the first lens group 2a and the second lens group 2b
_{The relationship} between _the ^focal _{length of} All you have to do is determine. Further, the fixed reflecting mirror 5a may be provided on the light receiving side, and the movable reflecting mirror 5 may be provided on the light transmitting side. The second embodiment is similar to the first embodiment shown in FIG. 4, even if the lens group is fixed and the light source 1 and detection means 6 are moved in the opposite direction with respect to the reflecting mirror 5. Needless to say.

In addition, for measurements when the object point only undergoes a decreasing displacement, the movable reflector 5 is fixed and the shift in the imaging position due to the movement of the object point is corrected by moving the light transmitting and receiving lens system. Since the constant angle with the optical lens system changes, the image will be formed at a different position on the detector 6, and the amount of movement may be converted into the amount of movement of the object point and read.

In the figure, an afocal system is constructed by two groups of convex lenses, but the present invention will not be adversely affected in any way even if the afocal system is composed of concave and convex lenses.
It goes without saying that the larger the constant angle θ with the optical axis of the light-transmitting lens, the greater the amount of movement of the light-receiving mirror when the object point moves, so that minute changes can be measured more accurately.

As described above, by using the illumination optical system with constant magnification according to the present invention, it is possible to form a light source image with a constant size at any position, and in that case, one of the light source and the afocal system must be moved. It is suitable not only because it allows the light transmitting lens system of the shape measuring device to have a simple configuration, but also because it can be used as an illumination optical system to change only the position without changing the size of the light source image. Needless to say, it can be used in various devices that require.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the conventional optical system for a shape measuring device, Fig. 2 is an explanatory diagram of the principle of the optical system according to the present invention, and Fig. 3 is an explanatory diagram showing the optical system of the first embodiment according to the present invention. , FIG. 4 is an explanatory diagram showing a modification of the first embodiment, FIG. 5 is an explanatory diagram of the optical system of the second embodiment,
FIG. 6 is an explanatory diagram showing a modification of the second embodiment. Explanation of symbols of main parts, 1... light source, 2a...
Light transmitting first lens group, 2b...light transmitting second lens group,
3...Object, 4a...First lens group for light reception, 4b
...Second lens group for light reception, 5...Reflector, 6...
Detector, 5a... fixed reflector.

Claims (1)

[Claims] 1 having a light source and an imaging optical system having an afocal system consisting of two lens groups whose focal positions match each other in order to form an image of the light source, 2 constituting the afocal system; two lens groups are provided so as to be integrally movable relative to the light source along the optical axis of the afocal system, and the imaging magnification of the light source image can be adjusted by moving one of the afocal system and the light source. An illumination optical system with constant magnification, characterized in that the distance between the light source and the image of the light source can be changed while keeping the distance constant.