JPS62215915A - Telecentric illuminating optical system - Google Patents

Abstract

PURPOSE:To simply change an illumination range by moving only a lens of the first group, by using a zoom lens for lenses of the first group and the second group. CONSTITUTION:A lens system is constituted as two group zoom lenses consisting of the first group 14 of a negative lens and the second group 16 of a positive lens, which have been placed in order from a light source 10 side. In this state, the group 14 is made movable along an optical axis 18, and also, the group 16 is fixed so that its position is not changed, on the optical axis 18, and when a composite focal distance (f) of the whole system has been set to the shortest one and the longest one on a design by moving the group 14, switching for a high magnification and a low magnification is used as an illuminating optical system of an expression, respectively. Also, a position of a rear side focus F' at the time when the distance (f) is the shortest on the design is set as a common position to be illuminated.

Description

[Detailed description of the invention] [Industrial application field]

This invention is for illuminating a measured object in a telecentric illumination optical system, particularly in a projection device or a measuring microscope, which converts the projection magnification by 1q in order to project objects of different sizes to the same size. This invention relates to improvements in telecentric illumination optical systems suitable for use in.

[Conventional technology]

When projecting objects or parts of projecting objects of different sizes are enlarged or reduced and projected onto a screen of the same size, for example, in a projection inspection machine, a method is used to convert the magnification of the projection objective lens. Similarly, in microscopes, the magnification of the objective lens is changed. In this case, the illumination optical system that illuminates the object to be projected or the object to be measured employs telecentric illumination in order to reduce the influence of focusing errors during measurement. In this case, if you use the same illumination system after converting the magnification of the projection (objective) lens, the range of incidence of transmitted light or reflected light on the projection lens will change, making it impossible to use the illumination luminous flux effectively. Or, you will not be able to recruit the necessary number of customers. Therefore, it is necessary to increase or decrease the illumination range by the illumination optical system in accordance with the magnification of the projection (objective) lens so that the illumination light flux can be used effectively. On the other hand, as shown in FIGS. 6 and 7, there is a device in which a positive lens L1 and a negative lens are arranged in the direction from the light source S to the illuminated surface O. As for the negative lenses, the sharpener for low magnification shown in FIG. 6 is replaced with negative lens L2, and the sharpener for high 18 skewers shown in FIG. is configured. (Problems to be Solved by the Invention) However, in the variable magnification illumination system as described above, when changing the magnification from a wide illumination area for low magnification to a narrow illumination area for high magnification, the peripheral luminous flux cannot be used effectively. In order to disappear,
There is a problem that the surface to be illuminated becomes dark. In other words, as shown in Fig. 6, a sharpener for low magnification has a long composite focal length, a large luminous flux diameter, and a small angle between the oblique luminous flux and the optical axis, so there is less wasted luminous flux (illumination efficiency). However, as shown in Fig. 7, when used for high magnification, the combined focal length is short, the diameter of the beam becomes narrow, and the angle of the oblique beam with respect to the optical axis becomes large, so that the negative lens L3
There is a problem in that the farther the position is from the illumination surface, the more the luminous flux that deviates from the illuminated surface increases, and the illumination efficiency decreases. Therefore, a problem arises in that the illumination operating path l1111WD shown in FIG. 7 becomes short. To solve this problem, it is possible to configure both the positive lens and the negative lens as a zoom lens, but in this case,
Zoom n structure? ! There are problems in that the process becomes complicated and the device becomes large. [Purpose of Fe Ming] This invention was made in view of the above-mentioned problems of the conventional technology, and consists of a two-group zoom lens, and by moving only the first group of lenses, the illumination range can be easily changed. An object of the present invention is to provide a telecentric illumination optical system that can perform the following tasks. Another object of the present invention is to provide a telecentric illumination optical system that has a long illumination working distance and high illumination efficiency.

[Means to solve the problem]

This invention provides a telecentric illumination optical system in which a light source is disposed on the front side and an object to be illuminated is disposed in the direction of the rear focal position of the entire system, in which a lens system is arranged as a first lens of negative lenses arranged in order from the light source side. and a second group of positive lenses.
Consisting of a group zoom lens: the first group is supported movably along the optical axis, the second group is fixed in position on the optical axis, and the first group is moved to zoom the entire system. When the combined focal length of the entire system is the shortest and longest in design, it is used as a switchable illumination optical system for high magnification and low magnification, respectively, and the combined focal length of the entire system is the shortest in design. The above object is achieved by making the rear focal point position a common illuminated position. Further, the present invention provides the above-mentioned method by configuring the n light sources to include a condenser lens that is disposed in front of the first group and forms a light source image to the rear side of the front end of the first group. It accomplishes its purpose. [Function] In the present invention, since the lenses of the first group and the second group are originally zoom lenses, the illumination light flux can be used efficiently even at high magnification, and the illumination working distance can be made long. I can do it. Furthermore, since the second BT is fixed and only the first group is moved, the structure is simple and the device volume and m output are small.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 to 3, this embodiment uses a lens system in a telecentric illumination optical system in which a light source 10 is disposed on the front side and an object to be illuminated is disposed in the direction of the rear focal point F position of the entire system. consists of a two-group zoom lens consisting of a first group 14 of negative lenses and a second group 16 of positive lenses arranged in order from the light source 10 side; the first group 14 is arranged along the optical axis 1.
8, the second group 16 is fixed in an unchangeable position on the optical axis 18, and the first group 14 is moved so that the combined focal length r of the entire system is the shortest in design. iAi is used as a switchable illumination optical system for IR rate and low magnification, respectively, and the rear focal point F-position when the combined focal length df of the entire system is the shortest in design. is set as a common illuminated position. Reference numeral 12 in FIGS. 1 and 2 indicates an object to be illuminated. That is, although the second lens group 16 is also a focus correction lens, it is fixed so as not to be movable in the direction of the optical axis 18, and only the first lens group 14 is movable. Here, the light source 10 is arranged in front of the first group 14 and includes a condenser lens 20 that focuses the light source image 11 on the rear side of the front end of the first group 14. Here, the lens focal lengths "1" and "f2" of the first lens group 14 and the second lens group 16 are -22, 1%l and 60%, respectively.
It is said to have three sickles. Also, the first group 14 and the second Lff1 for the focal point F, F=
6 and the distance e between these lenses are set to take movement trajectories 14A and 16A shown in FIG. However, the movement trajectory 16A is a virtual trajectory. Further, the relationship between the inter-lens distance 01, the composite fish point distance [, the light exclusion side focus F, and the rear side focus F' at a specific position is as shown in FIG. 4. Therefore, the composite focal length f is 28.92 and 125.7
It takes two values of 8n, and a zoom ratio of 4.35 can be obtained. In the above-mentioned actual flow example, the light source 1o is equipped with a light bar; a condensing lens 20 for focusing the image 11 on the rear side of the front end of the first group 14; As shown in the figure and FIG. 3, for high magnification, the light source side focal point F is
This is because the light source 10 cannot be provided at this position because it is located inside or on the rear side of the first group 14 . Therefore, by appropriately selecting the focal lengths "1" and "2" of the first group 14 and the second group 16 and the inter-lens distance e, the position of the light source side focal point F can be set from the front end of the first group 14. If the telecentric diaphragm 22 is also located on the front side, there is no need to provide the condenser lens 20. Next, a second embodiment of the present invention shown in FIG. 5 will be explained. A relay lens group 24 is provided so as to be able to provide a relay lens group 24. Reference numeral 13 in FIG. 5 indicates a relay image of the light source image 11. The telecentric aperture 22 is provided to make the NA of the illumination light beam variable in order to improve measurement accuracy when measuring a rod or the like.
is arranged between the first group 14 and the condenser lens 20, and
The relay lens group 24 includes a telecentric aperture 22 and a first
It is arranged between the group 14. The telecentric diaphragm 22 is arranged at the focal point of the condensing lens 20, and the relay lens group 24 focuses the light source image 11 on the first group 1 with the telecentric diaphragm 22 as the front object point.
The image is formed on the front side or the rear side of 4. [Effects of the Invention] Since the present invention is configured as described above, the illumination range can be easily switched between high magnification and low magnification by moving only the first group of lenses, and Since the lenses in the group are both zoom lenses, efficient illumination is possible and the illumination working distance can be increased, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the state of the first embodiment of the telecentric illumination optical system according to the present invention at low magnification, and FIG.
A diagram showing the state of the example at high magnification; FIG. 3 is a diagram showing the position]d relationship of the lens groups in the example; FIG. 4 is a diagram showing the relative positional relationship of the lens groups in the example; Fig. 5 shows the second embodiment of the present invention, but is the same as Fig. 1, and Figs. 6 and 7 show the conventional magnification change. FIG. 7 is a diagram showing the state of the telecentric illumination optical system at low magnification, and FIG. 7 is a pictorial diagram showing the state at high magnification. DESCRIPTION OF SYMBOLS 10... Light source, 11... Light source image, 12... Illuminated object, 14... M1 group, 16... Second group, 18... Optical axis, 20... Condensing lens , "...Synthetic focal length, F-...Back focus, F...Light source focus, e...Inter-lens distance. Agents: Kei Matsuyama, Ronsuke Cantaka, Figure 3! 4. figure

Claims (2)

[Claims] (1) In a telecentric illumination optical system in which a light source is placed on the front side and an object to be illuminated is placed in the direction of the rear focal position of the entire system, the lens system includes a first group of negative lenses placed in order from the light source side. and a second group of positive lenses; the first group is supported movably along the optical axis, and the second group is fixed in position on the optical axis, When the first group is moved to make the combined focal length of the entire system the shortest and longest in design, it is used as a switchable illumination optical system for high magnification and low magnification, respectively,
A telecentric illumination optical system characterized in that a rear focal position when the combined focal length of the entire system is the shortest in design is set as a common illuminated position. (2) The light source is arranged in front of the first group, and includes a condenser lens that focuses an image of the light source on the rear side of the front end of the first group. Telecentric illumination optics.