JPS5912974B2 - Optical centering method using laser light in lens centering work - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION As is well known, in general, for lenses that require various high performances, a plurality of lenses are bonded together or
Alternatively, they are placed side by side at regular intervals and combined, but for this purpose it is necessary to arrange the optical axes of each single lens correctly on a straight line, and to position the optical axis of each lens correctly in the center. Generally, the outer circumferential circle is ground to a predetermined diameter, and the lens is held at this outer circumferential circle.

Therefore, it is necessary to center and fix the optical axis of each lens one by one with the center of rotation of the holding spindle, and then perform a grinding operation to grind the outer periphery and periphery of this lens.
At this time, in the optical centering method for aligning the centers of the lens and the holding spindle, the processed lens is usually first temporarily held in the lens holder of the rotating spindle, then both are rotated, and a target placed behind the lens is used. When the image of the target plate is transmitted through the processing lens 30 and then formed on the fixed target plate of the microscope for observation, if the optical axis of the processing lens is decentered with respect to the rotation axis, the optical system As a single element is influenced by this, the image of the target plate appears to move in a circular orbit, so the processing lens is moved relative to the rotating spindle so that the movement circle of the center of the image is minimized. After carrying out removal work for mounting and correcting the lens, the lens is held and fixed in that position on the spindle, and then the outer periphery of the lens is ground.

However, in this case, the focal length of the processed lens,
The position of the image of the target plate changes greatly depending on whether the convergent lens or the diverging lens is used, so the position of the microscope must be adjusted so that the image of the target plate is formed on the fixed plate of the microscope. Generally, various adjustments such as moving the objective lens back and forth and changing the distance between the objective lens and a fixed target plate are required.

The present invention eliminates the need for these various adjustment operations at all, and also makes it possible to constantly set correction values, thereby making the work easier and smoother.

In the lens centering method of the present invention, a thin helium-neon laser visible beam with excellent parallelism is used to center the lens, without using the image of the target plate described above, and this is transmitted to each optical lens. After that, the beam is projected onto an opaque screen surface, and the cross section of the beam projected onto this screen surface is observed. This system is designed to allow visual measurement using scales drawn in advance on the screen surface, and will be explained in detail below with reference to a drawing showing one implementation situation.

In FIG. 1, a quasi-parallel visible light beam 2 with a beam divergence angle of about 1 milliradian is emitted from a laser oscillator 1, is converged by two condenser lenses 3 and 3', and is focused on the front main plane of a processing lens 4. The light beam after passing through the lens 4 becomes a diffused light beam with the vertex at the point on the rear principal plane of the lens 4. According to the well-known law of lenses, the spread of the light beam is There is a difference between convergence and divergence in the rate of change in the beam cross section perpendicular to the optical axis, but
This is the same as the degree of convergence of the light beam when it enters the lens.

In FIG. 2, X-X' represents the optical axis of the optical system of the present invention and the rotation center axis of the spindle 6, and Y-Y represents the optical axis of the processed lens 4.

Also, when a-+H1 is the center line of the convergent light beam, its half-angle is Δθ, and when considering the b-+H1 line and the C-+H1 line, HO is the front principal point, HHO is the front principal plane, and
Assuming that H'o is the rear principal point and 11'H is the rear principal plane, the center line of the convergent beam from a to H1 is HC-+a' with respect to the plane of the rear focal length f'' of the lens 4. H'0C''/CHl, HOb5/BH from the H?) point
Draw the auxiliary line of l and intersect the plane of f'' at point C', and the line connecting b' and H1 are b→H1→H'1→b', respectively.
The refraction direction by the lens 4 is shown as C-+H1→H1→C5.

Here, since /BHlC=2△θ=/b′c′, if points b and c change the distance k from the front principal plane to f′
, and assuming that it is on a plane perpendicular to the optical axis, BC
=B5C', and the size of the cross section of the light beam on the plane perpendicular to the optical axis is the same for both the convergent light beam and the diffused light beam.

Here, the explanation is made using the front principal plane H'H'0 and the rear principal plane H'H'0, but the above is based on the difference between positive and negative lenses, the difference in their shapes, and the focal length. Irrespective of size, only the front and rear principal planes are related.

Now, suppose we consider two types of lenses with different shapes and focal lengths, and when their transmission eccentric angle values ξ are the same, in FIG. The center line is a-+H1, which coincides with the optical axis X-X' of the optical system of the present invention, and its convergence angle is 2Δθ, which is spatially fixed.

In addition, the center line of the light flux that passes through the lens 4 and exits from point H is inclined to the x-r optical axis by the transmission eccentric angle ξ, and the river →
Directed in the direction of a', the divergence angle of the light beam is approximately 2△θXCOS
2ξ, which is an almost constant value, and the luminous flux is at the same fixed position spatially. As a result of these conditions, for the same ξ value for various processed lenses 4, the position of the center σ of the beam cross section when the beam passes through the subsequent objective lens 7 and projection lens 8 and reaches the screen 9. are at equal distances from the optical system axis center 0 of the present invention.
However, when considering the conditions in more detail,
Depending on the shape and type of the processed lens 4, there are differences in the relative positions of the front and rear principal planes with respect to the lens 4 surfaces, changes in the distance due to the thickness of the lens 4, differences between air and vacuum in the space on the front and rear sides of the lens 4, Although various different conditions can be counted, such as changes in the refraction angle due to the material of the
The tolerance ξ value used is usually 10
The measurement error of ξ due to the change in the center position of the beam cross section on the screen 9 is 0.2% or less even under the differences in the above conditions, and the present invention This is not a problem in terms of the intended use of the optical system.

Also, ξ=f? ) H'1/f' [=-ξ],
At ξ10 minutes (f-+f'') (angle), no error is recognized even if ξ=-ξ.

Next, the change in the size of the projected beam cross section is affected by the size of the cross section diameter at point H1 of the convergent beam, and if the beam cross section at this point is large, it will depend on the focal length of the processing lens 4 and other factors. This causes a change in the diameter of the cross section of the projected light beam, but in the present invention, this can be prevented by using a laser beam.

Note that Fig. 2 is an explanatory diagram for the case of a positive lens, but in the case of a negative lens, the refraction direction of the light beam after passing through lens 4 in the figure is 180° symmetrical with respect to the X-X5 optical axis. The only difference is that In this way, the diffused light flux becomes a convergent light flux again by the objective lens 7, and
-X' optical axis, but the projection lens 8 increases the angle of inclination with respect to the X-X' optical axis, crosses the optical axis, reaches the screen 9, and the luminous flux at that position. It shows the cross section Pt.

If the cross section Pt of the light beam reflected on the screen 9 is circular with a diameter of about 5 to 10 mm, the screen 9 can be seen clearly with both eyes even if the eye is removed from the screen 9. In order to recognize and facilitate measurements, a marking plate 10 is inserted immediately after the condenser lens 3' in FIG.

This marker 10 has a different function from that of a marker used in a general imaging optical system, and serves to block part of the light beam at the inserted portion. If , the features of the visible laser beam 2 allow the cross-section of a circle to be cut into a cross no matter where you look at the cross-section of the beam within the beam length distance equivalent to the optical system of the present invention. can. FIG. 3 shows an example of the cross-sectional shape 10' of the beam projected onto the screen 9. When the processed lens 4 is attached to the spindle 6 and rotated, if there is an axis misalignment in its holding, the cross-sectional shape of the beam will be moves in a circular orbit according to the magnitude of the transmission eccentric angle, so by reading the diameter 10'7 of this orbit on the scale on the screen 9, the value of the ξ angle can be directly measured, and then, A centering operation is performed to correct the holding position of the lens 4 with respect to the spindle 6 so that the center of the beam cross section is aligned with the center of the orbit circle, and when the diameter of the circular orbit becomes a point, complete centering is completed. In this case, the work will be made easier if the screen 9 can be manually shifted to align the center of the circular orbit so that it is easy to read.

However, if the brightness and darkness of the cross-sectional shape 10' of the luminous flux shown in FIG. It is also possible to make the cross-sectional pattern cross-shaped, and in either case, a diffraction image is formed in the vicinity of the cross due to the phenomenon of light diffraction, but this is symmetrical to the left, right, or top and bottom of the cross. Since it appears to be located at , it does not have a large effect on the observation.

Based on the above, the advantages and effectiveness of the method of the present invention compared to conventional methods are as follows: First, the image of the conventional target plate is formed on a fixed plate in a microscope and observed. In the method described above, there is no need for the image formation adjustment work required each time the lens is changed, and even if the processed lens is of a different type, the processing lens 4 can be simply replaced without touching the optical system of the present invention at all. The cross-section of the light beam is clearly projected on the screen 9 at a position corresponding to the transmission eccentric angle, and can be viewed.Also, by rotating the spindle 6 together with the processed lens 4 that is attached to it, the cross-section of the light beam can be seen. By drawing a circular locus on the screen 9 and reading the diameter of this circle on the scale 9' carved on the screen 9, the transmission decentering angle can be directly determined. Because the magnification is exactly the same and there is no discrimination due to There is no change in the shape, and the image can always be seen in the same shape. In addition, since the processing lens 4 uses only a narrow beam of extremely paraxial rays, it is possible to form images that are caused by various aberrations that are common in single lenses in conventional methods. No blurring of details occurs.

Furthermore, the bright and clear beam cross-sectional pattern projected onto the screen 9 can be viewed binocularly from an appropriate distance in a posture suitable for centering correction work, making it easier to perform work while looking through the eyepiece of a microscope. There is no cramping, centering work is easy and efficient, and visual fatigue can be drastically reduced. As described above, according to the method of the present invention, it is possible to center any type of lens centering machine such as a single spindle adhesive type centering machine, a bell clamp type centering machine, a manual type, an automatic type, a vacuum chuck type, etc. Although it can be applied to output work equipment, in particular, in a bell clamp type centering machine, the processing lens 4 can be moved from both sides by the bell chucks 5, 5' of relatively long spindles 6, 6'. Crimp and clamp the
Because it rotates as one unit to perform grinding, the front and rear
Even if the space available is only within the elongated hollow part of the pair of rotating spindles 6, 6', by applying the method of the present invention, a part of the light beam is blocked and dimmed when it passes through the elongated hollow part. This method not only solves the problems of the conventional method, but also allows easy observation of the alignment of the holding lens 4 with respect to the rotating spindles 6, 6' at all times during grinding.
It is possible to further expand the range of lens grinding near the limit of automatic centering using the bell clamp type, and it is a particularly optimal centering method for a bell clamp type centering machine.

[Brief explanation of the drawing]

The drawings show a state of implementation of an optical centering method using laser light in lens centering work according to the present invention, and Figure 1 shows the relationship between the optical system of the present invention and the lens holding spindle part in centering work. Figure 2 is a diagram illustrating the outline of the correlation arrangement; Figure 2 is a diagram illustrating the route of the light beam to the lens to be processed;
FIG. 3 is a diagram showing an example of a cross-sectional pattern of a light beam projected onto a screen. 1...Lower oscillator, 2...Visible light flux, 3,3'...Condenser lens, 4...
... Lens to be processed, 5, 5'... Bell chuck, 6, 6'... Spindle, 7... Objective lens, 8... Projection lens, 9...
Screen, 9/...Scale, 10...
Signboard, 10'... Luminous flux cross-sectional shape, 10'5...
...The diameter of the orbit.

Claims (1)

[Claims] 1 The parallel and linear thin visible light beam 2 continuously oscillated from the laser oscillator 1 is softened by a single spindle adhesive type or a bell clamp type in order to be centered in advance by two condenser lenses 3 and 3'. Processed lens held 4
The light beam that converges until it approaches a point on the front principal plane of The laser oscillator 1, each lens 3, 3', 7, 8, and the screen 9 are configured so that the beam cross section pg obtained by projecting onto a screen 9 by a projection lens 8 can be seen, and the set intervals are fixed. The eccentric angle of the transmitted light beam caused by the mismatch between the optical axis of the lens 4 to be processed, which is arranged on a straight line and is held soft, and the optical axis of the optical system,
The deviation of the transmitted light beam is observed as the offset position of the 0' point relative to the 0 point on the screen 9, and is caused by the holding deviation between the optical axis center of the lens 4 to be processed and the rotation axis center of the rotating spindle 6 for centering and grinding. By rotating the spindle 6 while holding the lens 4 to be processed, the angle can be observed by the diameter of the circular locus drawn by the center of the cross section of the light beam projected onto the screen 9. @0 on 9
The size of 0'@ and the diameter of the locus circle are made directly proportional to the transmission decentering angle, and the amounts are directly read on the scale scale on the screen 9, and the optical axis of the lens 4 to be processed is determined based on these values. The centering work for correcting the deviation between the center and the rotational axis of the spindle 6 to below the machining eccentricity tolerance can be easily carried out in terms of quantity, and a black crosshair or white mark is placed immediately after the condenser lens 3'. A lens centering system characterized in that a signboard 10 engraved with cut-out cross lines or the like is provided to block a part of the cross section of the light beam so that the center position of the cross section of the light beam reflected on the screen can be easily recognized. Optical centering method using laser light in work.