JPH0792085A - Optical system transmittance measuring device and measuring method - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the accuracy of optical system transmittance measurement. [Structure] An output when the light flux from the convergent light flux generating means 1 is directly received by the light intensity detecting means 5, and the convergent light flux generating means 1
From the output when the optical system a and the optical system b are arranged in the light flux from, the output when the optical system b and the optical system c are arranged, and the output when the optical system c and the optical system a are arranged. , The transmittances of the optical systems a, b, and c are calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system, and more particularly to a transmittance measuring apparatus and a measuring method for a convergent optical system which is composed of one or more groups and has a finite object-image distance.

[0002]

2. Description of the Related Art Conventionally, regarding the transmittance measurement of an optical system,
JIS B7107 discloses a method for measuring the spectral transmittance of a photographic lens.

FIG. 4 shows Method 1 in JIS B7107.
It is a measuring device of the method disclosed as (measuring method by finite aperture). Monochromator injection slit 2
The light flux exiting from No. 1 is converted into a parallel light flux by the collimator lens 22, and the parallel light flux has its light flux diameter limited by the light flux limiting diaphragm 23.

A lens 24 to be inspected is disposed after the diaphragm 23 for limiting the light flux, and the light flux is focused on the field diaphragm 25 and the relay lens 2.
The photoelectric output F _{s when} the light is guided to the integrating sphere 27 via 6 (FIG. 4 (1)), the lens 24 and the field stop 25 are removed, and the light flux from the light flux limiting stop 23 is relayed by the relay lens 26. seeking transmittance of the lens 24 by the time that led directly to the integrating sphere 27 (FIG. _{4 (2)) F s /} F o × 100 (%) photoelectric output from the F _o of.

FIG. 5 shows Method 2 in JIS B7107.
It is a measuring device of the method disclosed as (measuring method by paraxial opening). Monochromator injection slit 2
The light flux exiting from No. 1 is converted into a parallel light flux by the collimator lens 22, and the parallel light flux has its light flux diameter limited by the light flux limiting diaphragm 23.

A lens 24 to be inspected is arranged after the light flux limiting diaphragm 23, and the light flux is passed through the field diaphragm 25 to integrate the sphere 2.
When the photoelectric output F _{s when} the light is guided to 7 (FIG. 5 (1)), the lens 24 and the field diaphragm 25 are removed, and the light flux from the light flux limiting diaphragm 23 is directly guided to the integrating sphere 27 (FIG. The transmittance of the lens to be inspected 24 is obtained from F _{o of the} photoelectric output of 5 (2)) and F _s / F _o × 100 (%).

[0007]

A so-called finite specification objective lens used in an optical system for an optical disk, which collects a light beam from a light source directly on the disk surface without passing through the collimator lens, does not require a collimator lens. It is widely used because it has advantages such as a simplified structure and cost reduction.

The objective lens for this type of optical disk is
The plastic injection molding has been mass-produced, but in recent years, along with the improvement of the plastic injection molding technology, the precision of the objective lens for optical disks has been further improved.
High performance has come to be desired. Therefore, it is necessary to perform a rigorous inspection on the manufactured lens to see if it is the target, and the transmittance, which is one of the most basic characteristics of the optical system, is also an important inspection item.

On the other hand, in the transmittance measuring method, both of the parallel light fluxes are imaged by the lens 24 to be inspected, and although the measurement can be performed well by a camera lens or the like which images an object at infinity, finite specifications In the case of a lens that focuses an object at a finite position, such as the objective lens for optical disk applications described above, there is a problem in that the occurrence of image blurring due to aberrations becomes large and measurement cannot be performed with high accuracy.

[0010]

SUMMARY OF THE INVENTION The present invention has been made under such circumstances, and has a convergent luminous flux generating means, a light intensity detecting means, and a luminous flux from the convergent luminous flux generating means. Output when the light is directly received at, the output of the light intensity detecting means when the optical system a with unknown transmittance and the optical system b with unknown transmittance are arranged in the light flux from the convergent light flux generating means, and the convergent light flux The output of the light intensity detecting means when the optical system b and the optical system c whose transmittance is unknown are arranged in the light flux from the generating means, and the optical system c and the optical system a are arranged in the light flux from the convergent light flux generating means. Storage means for storing the output of the light intensity detection means at that time, and an optical system a, an optical system b, based on the output values.
Provided is a transmittance measuring device for an optical system, which is provided with a calculating means for calculating the transmittance of the optical system c.

The present invention also provides a transmittance measuring device for the above optical system, wherein the convergent light beam generating means is movable in the optical axis direction of the generated light beam. Further, the present invention provides the transmittance measuring device of the above optical system, wherein the light intensity detecting means is movable in the optical axis direction of the light flux from the convergent light flux generating means.

Further, according to the present invention, the output when the light flux from the convergent light flux generating means is directly received by the light intensity detecting means is P,
The output of the light intensity detection means when an optical system a with an unknown transmittance and an optical system b with an unknown transmittance are arranged in the light flux from the convergent light flux generation means is Pab The output of the light intensity detecting means when the system b and the optical system c of unknown transmittance are arranged is Pbc, and the light intensity detecting means when the optical system c and the optical system a are arranged in the light flux from the convergent light flux generating means. When the output of P is Pca, the above-mentioned calculation means is a calculation means for calculating the transmittance Ta of the optical system a, the transmittance Tb of the optical system b, and the transmittance Tc of the optical system c by the formula 3. An optical system transmittance measuring device is provided.

[0013]

[Equation 3]

Further, according to the present invention, the combined transmittance Tab of the optical system a and the optical system b, the combined transmittance Tbc of the optical system b and the optical system c, and the combined transmittance Tca of the optical system c and the optical system a. Is measured, and from each value, the transmittance Ta of the optical system a is calculated by the equation 4,
There is provided a method for measuring the transmittance of an optical system, characterized by obtaining the transmittance Tb of the optical system b and the transmittance Tc of the optical system c.

[0015]

[Equation 4]

The structure of the measuring apparatus of the present invention will be described with reference to FIG. The measuring apparatus of the present invention is a convergent light beam generating means 1 (laser light source 2, convex lens 3, convex lens 4 in the embodiment).
A light intensity detection means 5 (a photodiode 6 in the embodiment), a storage means 9 (a storage portion 11 of the microcomputer 10 in the embodiment), and a calculation means 12 (a calculation portion 13 of the microcomputer 10 in the embodiment). With.

In FIG. 1, 7 is a mount, 8 is an optical bench, 14 is an optical system a, optical system b or optical system c, and 15 is an optical system b, optical system c or optical system a. The light intensity detecting means 5 is arranged substantially on the optical axis of the light flux from the convergent light flux generating means 1.

The distance between the convergent light flux generating means 1 and the light intensity detecting means 5 is variable, and the light flux from the convergent light flux generating means 1 is brought close to a position where the convergence point of the light flux and the light intensity detecting means 5 coincide with each other. The optical system is configured to be separated from the optical axis by the sum of the distances between the object images of the two optical systems to be measured.

Next, the measuring method of the present invention will be described with reference to FIGS. The measuring method of the present invention comprises the following steps. First, the optical system a and the optical system b are converged to form a light flux.
Of the optical system b, the convergence point of the light flux from the convergent light beam generating means 1 coincides with the object point of the optical system a, and the image point thereof becomes the object point of the optical system b. The light intensity detection means 5 is placed at the point position, and the output after passing through the optical system a and the optical system b is stored in the storage means 9 (step 1).

Secondly, in the light beams from the convergent light beam generating means 1 in the optical system b and the optical system c, the convergence point of the light beam from the convergent light beam generating means 1 coincides with the object point of the optical system b, and its image The points are arranged so as to be the object points of the optical system c, the light intensity detection means 5 is placed at the image point position of the optical system c, and the output after passing through the optical systems b and c is stored in the storage means 9. (Step 1).

Thirdly, in the light flux from the convergent light flux generating means 1 in the optical system c and the optical system a, the convergence point of the light flux from the convergent light flux generating means 1 coincides with the object point of the optical system c, and its image The points are arranged so as to be the object points of the optical system a, the light intensity detection means 5 is placed at the image point position of the optical system a, and the output after passing through the optical systems c and a is stored in the storage means 9. (Step 1).

Fourth, the light intensity detecting means 5 is moved to the convergence point of the light flux from the convergent light flux generating means 1 to receive the light, and the output thereof is stored in the storage means 9 (step 4). Finally, the combined transmittance of the optical systems a and b, the combined transmittance of the optical systems b and c, the combined transmittance of the optical systems c and a (step 5), and the optical systems a, b, and c. The transmittance is calculated by the calculating means 12 (step 6).

[0023]

The operation of the transmittance measurement used in the present invention will be described below. For three optical systems a, b, and c whose transmittances are unknown, the combined transmittance of the optical systems a and b is Tab, the combined transmittance of the optical systems b and c is Tbc, and the optical systems c and a. Let Tc be the composite transmittance of Tc, Tb be the transmittance of the optical system a, Tb be the transmittance of the optical system b, and Tc be the transmittance of the optical system c.
Two expressions hold.

[0024]

[Equation 5]

Therefore, if Tab, Tbc, and Tca can be known, the above three equations become simultaneous equations in which Ta, Tb, and Tc are unknowns.
b and Tc can be calculated.

[0026]

[Equation 6]

When measuring the combined transmittance of the two optical systems, the converging light flux from the convergent light flux generating means is configured to be relayed by the two optical systems so that the convergent light flux has a light intensity. It can lead to a detection means. The measuring device and the measuring method of the present invention are configured based on these calculation principles and optical arrangements, and a device for obtaining a combined transmittance of two optical systems is used to measure three unknown transmittances. With respect to the optical system of (3), the transmittance of each composite in three combinations of two selected from three is obtained by measurement, and the transmittance of each optical system is obtained by calculation.

[0028]

EXAMPLE A measuring apparatus of an example will be described with reference to FIG. The measuring apparatus according to the embodiment includes the convergent light flux generating means 1, the light intensity detecting means 5, the output when the light flux from the convergent light flux generating means 1 is directly received by the light intensity detecting means 5, and the convergent light flux generating means 1. Output of the light intensity detecting means 5 when the optical system a and the optical system b are arranged in the light flux of the light beam, and the light intensity detection when the optical system b and the optical system c are arranged in the light flux from the convergent light flux generating means 1. Light intensity detection means 5 when the optical system c and the optical system a are arranged in the output of the means 5 and the light flux from the convergent light flux generation means 1.
Of the output of the optical system a, b,
and a calculation means 10 for calculating each transmittance of c. Hereinafter, each part will be described.

(Convergent light flux generating means 1) Laser light source 2
And a convex lens 3 and a convex lens 4. The light flux from the laser light source 2 is converted into a convergent light flux by the convex lens 3 and the convex lens 4 and emitted. (Light intensity detecting means 5) A photodiode 6 is used. The incident convergent light beam is received on the photodiode 6. The output value proportional to the light intensity obtained by receiving light is A /
It is D converted and sent to the microcomputer 10. The photodiode 6 is held by an optical support made up of a pedestal 7 and an optical bench 8, and is movable in the optical axis direction of the light flux from the convergent light flux generating means 1.

(Storage unit 9) The output value obtained by the light intensity detection unit 5 is stored. The storage unit 11 of the microcomputer 10 is used. (Calculation unit 12) The transmittance of the optical system is calculated based on the value of the storage unit 7 (storage unit 11 of the microcomputer 10). It is executed by using the arithmetic unit 13 of the microcomputer 10.

When two optical systems (14 and 15 in FIG. 1) are placed in a light beam and the output of the light intensity is observed, the two optical systems have the convergence point of the light beam from the convergent light beam generation means 1. It is arranged to be relayed by two optical systems. That is, it is arranged so that the convergence point position of the light flux from the convergent light flux generation means 1 becomes the object point of the first optical system, and the image point becomes the object point of the second optical system. By doing so, the convergent light beam can be guided to the light intensity detecting means 5 with or without the optical system in the light beam.

Further, when the above arrangement is performed, by setting the object-image distance of the optical system to the object-image distance when the optical system is actually used, it is possible to suppress the occurrence of aberration caused by the difference in conjugate conditions. As a result, the convergent light flux is guided to the light intensity detecting means 5 in a favorable manner. Next, the measuring method of the embodiment will be described with reference to FIGS. First, the optical system a and the optical system b are arranged in the light flux from the convergent light flux generation means 1, and the output Pab of the light intensity detection means 5 after passing through the optical system a and the optical system b is stored in the storage means 9. Store (step 1).

Second, the optical system b and the optical system c are arranged in the light flux from the convergent light flux generating means 1, and the output Pbc of the light intensity detecting means 5 after passing through the optical system b and the optical system c is stored. It is stored in the means 9 (step 2). Thirdly, the optical system c and the optical system a are arranged in the light flux from the convergent light flux generation means 1, and the output Pca of the light intensity detection means 5 after passing through the optical system c and the optical system a is stored in the storage means 9. Store (step 3). Fourthly, the light flux from the convergent light flux generation means 1 is directly received by the light intensity detection means 5, and its output P is stored in the storage means 9 (step 4). This value P serves as a reference for 100% transmittance.

Finally, the combined transmittance of the optical systems a and b, the combined transmittance of the optical systems b and c, the combined transmittance of the optical systems c and a (step 5), and the optical systems a and b, The respective transmittances of c are calculated by the calculating means 12 having the calculating function of the equation 7 (step 6).

[0035]

[Equation 7]

It is desirable that the optical systems a, b, and c have the same specifications. If the optical systems a, b, and c have the same specifications, it is possible to measure with the same light beam diameter passing through the optical system in any of step 1, step 2, and step 3, and it is caused by the difference in light beam diameter. You can prevent the error.

The present invention is not limited to the above embodiment. Although the embodiment has shown the configuration in which the light intensity detecting means 5 is movable in order to change the distance between the convergent light flux generating means 1 and the light intensity detecting means 5, the convergent light flux generating means 1 is mounted on a mount on an optical bench. It may be configured such that it is held in place and is movable in the optical axis direction of the light flux. Alternatively, both the convergent light flux generating means 1 and the light intensity detecting means 5 may be movable.

Further, in the embodiments, all three optical systems with unknown transmittance have been described as convergent optical systems, but measurement is also possible in the case of a divergent optical system with three optical systems with unknown transmittance. it can. As shown in FIG. 3, the light intensity detection means 5 is configured by combining a condenser lens 16 and a photodiode 6, and the combined transmitted light amount of the two divergence system optical systems (17, 18) is shown in FIG. 3) and the amount of light directly from the convergent light flux generating means 1 may be measured in the arrangement of FIG. 3 (2).

The convergent light beam generating means may be constituted by using a white light source and a monochromator which is a spectroscopic means to measure the spectral transmittance of the optical system.
The light intensity detecting means may be configured to guide the convergent light flux to the integrating sphere. Further, the converged light flux may be guided to the photoelectric conversion element via the optical fiber.

Although the measurement procedure has been described in the procedure from step 1 to step 6, step 1 to step 4 is not limited to this order, and step 1 to step 4 may be an arbitrary order. Although three optical systems have been described as measurement targets, the above-mentioned measurement can be performed by combining three optical systems even when there are four or more optical systems, and the transmittance of each optical system can be known. Further, from the transmittance of the optical system whose transmittance is known by the above method, and the transmittance of the optical system whose transmittance is unknown,
It is also possible to know the transmittance of an unknown optical system.

[0041]

As described above, according to the present invention,
By combining three or more optical systems, their transmittances can be measured with high accuracy. Also, because the optical arrangement is very close to the actual usage conditions and the measurement is performed using a light flux that is close to the actual light flux diameter, it can be used finitely, such as optical disk objective lenses, copier lenses, and facsimile lenses. The optical system can be measured almost without being affected by the aberration caused by the difference in the optical arrangement, and the defect of the lens member within the effective diameter or the quality of the antireflection film generally applied to the lens surface can be judged. The effect of being able to obtain information that can be effectively used for is also recognized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an optical system transmittance measuring apparatus of the present invention.

FIG. 2 is a process diagram showing a procedure of an example of a method for measuring transmittance of an optical system according to the present invention.

FIG. 3 is a configuration diagram of a transmittance measuring device of an optical system when the present invention is applied to a divergent optical system.

FIG. 4 is a configuration diagram of a conventional transmittance measuring device for an optical system.

FIG. 5 is a block diagram of a conventional transmittance measuring device for an optical system.

[Explanation of symbols]

 1: Convergent light beam generation means 2: Laser light source 3: Convex lens 4: Convex lens 5: Light intensity detection means 6: Photodiode 7: Frame 8: Optical bench 9: Storage means 10: Microcomputer 11: Microcomputer storage section 12: Computing means 13: Computing part of microcomputer 14: Optical system a, optical system b or optical system c 15: Optical system b, optical system c or optical system a 16: Condensing lens 17: Divergent system optical system 18: Divergent system Optical system 21: Monochromator exit slit 22: Collimator lens 23: Ray bundle limiting diaphragm 24: Test lens 25: Field diaphragm 26: Relay lens 27: Integrating sphere

Claims (5)

[Claims] 1. A convergent light beam generation means, a light intensity detection means,
An optical system a with unknown transmittance and an optical system b with unknown transmittance are arranged in the output when the light intensity detecting means directly receives the light flux from the convergent light flux generating means and in the light flux from the convergent light flux generating means. When the optical system b and the optical system c whose transmittance is unknown are arranged in the light flux from the convergent light flux generation means, the output of the light intensity detection means and the converged light flux generation means A storage unit that stores the output of the light intensity detection unit when the optical system c and the optical system a are arranged in the light flux, and the transmittance of the optical system a, the optical system b, and the optical system c based on the above output values. A transmittance measuring device for an optical system, comprising: a calculating means for calculating. 2. The transmittance measuring device for an optical system according to claim 1, wherein the convergent light beam generating means is movable in the optical axis direction of the generated light beam. 3. The transmittance measuring device for an optical system according to claim 1 or 2, wherein the light intensity detecting means is movable in the optical axis direction of the light flux from the convergent light flux generating means. 4. An output P when the light flux from the convergent light flux generating means is directly received by the light intensity detecting means, and an optical system a of unknown transmittance and an unknown transmittance in the light flux from the convergent light flux generating means. The output of the light intensity detecting means when the optical system b is arranged is P
ab, the output of the light intensity detection means when the optical system b and the optical system c of unknown transmittance are arranged in the light flux from the convergent light flux generation means is Pbc, and the optical system c is included in the light flux from the converged light flux generation means. When the output of the light intensity detecting means when the optical system a is arranged is Pca, claim 1, claim 2 or claim 3
Is a calculating means for calculating the transmittance Ta of the optical system a, the transmittance Tb of the optical system b, and the transmittance Tc of the optical system c by the mathematical formula 1. . [Equation 1] 5. A composite transmittance Ta of the optical system a and the optical system b.
b, the combined transmittance Tbc of the optical system b and the optical system c, and the combined transmittance Tca of the optical system c and the optical system a are measured, and from each value, the transmittance Ta of the optical system a, the optical system T A method for measuring the transmittance of an optical system, characterized by obtaining the transmittance Tb of b and the transmittance Tc of the optical system c. [Equation 2]