JPH06347369A - Lens performance inspecting apparatus - Google Patents

Abstract

PURPOSE:To focus a test pattern at an arbitrary position of image scanning mean by providing a plurality of photodetecting means near the scanning means, setting one or more of mirrors disposed on an optical axis and an off-axis optical path to an arbitrary angle. CONSTITUTION:Luminous fluxes from a light source 1 are emitted from test patterns 2a, 2b for inspecting an epaxial image, an off-image of a chart 2 to a lens 3 to be inspected. The flux from the pattern 2a is focused on image scanning means 4 through an epaxial optical path 3a, its signal is A/D-converted, and calculated by signal processing means 5 to inspect a focused state of the pattern 2a from a MTF value, an image processed output, etc. A mirror 6a is made to be out of the path 3a. On the other hand, the flux of the pattern 2b is propagated through an off-axis optical path 3b at an off-axis optical path 3c by a mirror 6b. In this case, when the path 3a is shut off at the mirror 6a under detection control by photodetecting means 20 and the path 3c is directed toward the center of the path 3a, the pattern 2b is focused on means 4, and a focused state of the pattern 2b can be similarly inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the positional light intensity distribution of a test pattern projection image formed by a lens to be inspected and forms a test pattern projection image of a plurality of image heights including the axis of the lens to be inspected. The present invention relates to a lens performance inspection device that inspects an image state.

[0002]

2. Description of the Related Art Conventionally, a test pattern such as a slit provided on a chart is imaged through a lens to be measured such as a photographic lens, and a light receiving element such as a CCD converts a positional light intensity distribution into a time series signal. As a lens performance inspecting apparatus for inspecting the imaging performance of a plurality of image heights including the axis of a lens to be inspected by analyzing a signal obtained from a light receiving element, for example, Japanese Patent Laid-Open No. 58-8.
There is an invention described in Japanese Patent No. 5132.

In the above invention, a plurality of slits are used as a test pattern, and at least one of the slit image projection positions is deviated due to the eccentricity of the lens to be inspected or the mounting error when the lens to be inspected is rotated. This is an MTF measuring device in which one projection slit image is on the light receiving element and the lens performance can be measured.

[0004]

However, the MTF measuring device in the prior art described above has the following drawbacks.

That is, a plurality of projected slit images are present on the light receiving element. When a plurality of projection images are present on the light receiving element, in order to measure the MTF performance of the lens under test, information on each projection image is separated and each projection image or a representative projection image is determined. Then, it is necessary to perform FFT calculation processing and the like on it. Whichever method is used, it is necessary to separate the information of a plurality of projected images into individual pieces of information, which complicates the processing and lengthens the measurement time.

Further, in order to reduce the separation processing of the projection image information, two projection images are present on the light receiving element in consideration of the focal length of the lens to be inspected, the projection magnification and the arrangement interval of the plurality of slits. With such a setting, it is possible to measure when one of the two is near the center of the light receiving element, but when both are near the end of the light receiving element, it is possible to measure the skirt of the projected image. There is a risk that information cannot be captured, and this will seriously affect lens performance evaluation.

What is further mentioned is the complication of the optical system around the light source. The irradiation light from the slits to the lens to be inspected has a uniform amount of light emitted from each slit, and the amount of light emitted from the same slit is uniform, and
The state in which the light receiving surface of the lens under test is uniformly irradiated is most desirable in terms of measurement accuracy. However, in order to realize the above-mentioned state with a plurality of slits, the structure becomes complicated because the optical system is inserted between the light source and the plurality of slits, and the slit is required to insert the optical system between the light source and the plurality of slits. It is difficult to actually realize it because, for example, the interval cannot be reduced.

Therefore, the present invention was developed in view of the above-mentioned drawbacks of the prior art, and it is possible to perform two or more tests on the image scanning means, which is a light receiving element, without complicating the optical system around the light source. A lens performance inspecting apparatus capable of inspecting lens performance from a test pattern projection image because there is no pattern projection image and the test pattern projection image can always be formed at an arbitrary position of the image scanning means. For the purpose of providing.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a light source, a chart provided with a test pattern illuminated by a light beam from the light source, and a lens to be inspected for forming a projected image of the test pattern on the chart. An image scanning means for converting the positional light intensity distribution of the projected image into a time series signal, a signal processing means for processing a signal from the image scanning means, and an image scanning means installed on the optical axis of the lens to be inspected. The optical axis switching means including an appropriately avoidable mirror for coaxializing a part of the on-axis light beam and the off-axis light beam of the lens to be inspected, and an optical path switching means including a mirror arranged on the off-axis optical path, In a lens performance inspecting apparatus for inspecting imaging performance of a plurality of image heights including on-axis, a plurality of light detecting means are arranged in the vicinity of the image scanning means, and a mirror on the optical axis and an off-axis optical path are provided. At least one of the mirrors The mirror is obtained by capable of setting an arbitrary angle.

FIG. 1 is a conceptual view of the present invention, and FIG. 2 is an enlarged front view of the chart in FIG. In FIG. 1, 3 is a lens to be inspected and 1 is a light source such as a halogen lamp. Reference numeral 2 is a chart. In this chart 2, chromium is vapor-deposited as a light-shielding film on the surface of a transmissive diffusion plate such as opal glass, and slits are formed on the light-shielding film at positions corresponding to the image height to be inspected on and off the axis. An opening such as a pinhole is arranged as a test pattern, the surface of which is directed toward the lens 3 to be inspected and is installed perpendicularly to the optical axis.

Reference numeral 6 denotes an optical path switching means composed of a mirror 6a which is arranged on the on-axis optical path and can be appropriately avoided, and a mirror 6b which is arranged on the off-axis optical path. Either one of the mirror 6a and the mirror 6b, or Both of them are configured so that the swing angle can be changed to an arbitrary angle around the point where the theoretical optical axis and the mirror surface intersect. Reference numeral 4 denotes an image scanning means such as a CCD installed vertically to the optical axis at the image forming position of the projected image of the test pattern on the chart 2. Reference numeral 5 is a signal processing means connected to the image scanning means 4, and 20 is a light detecting means installed in the vicinity of the image scanning means 4.

In the apparatus having the above structure, the light flux emitted from the light source 1 is diffused evenly on the chart 2, and a part of the light flux is emitted from the test pattern provided on the chart 2 toward the lens 3 to be inspected. To be done. As shown in FIG. 2, the chart 2 is provided with an on-axis image inspection test pattern 2a and an off-axis image inspection test pattern 2b.
The light flux emitted from a passes through the on-axis optical path 3a, and the test pattern 2 is applied to the image scanning means 4 by the imaging action of the lens 3 to be inspected.
Generate a projected image of a.

At this time, the mirror 6a is moved to the test pattern 2a.
It is avoided at a position where the light flux emitted from is not blocked. The positional light intensity distribution of the projected image of the test pattern 2a generated by the image scanning means 4 is converted into a time-series signal by the image scanning means 4, and the signal is subjected to A / D conversion / operation etc. by the signal processing means 5. , The MTF value, the image processing output, and the like can be used to inspect the image formation state of the projected image of the test pattern 2a generated by the lens 3 to be inspected.

On the other hand, the light beam emitted from the test pattern 2b passes through the off-axis optical path 3b, passes through the lens 3 to be inspected, and is then converted by the mirror 6b in the direction crossing the axial optical path 3a (optical path 3c). At this time, if the mirror 6a is installed at a position that blocks the on-axis light flux and matches the off-axis optical path 3c and the on-axis optical path 3a, a projected image of the test pattern 2b is generated on the image scanning means 4.

However, even if such a theory is true,
Actually, due to the eccentricity of the lens 3 to be inspected and the mounting error,
The projected image of the test pattern 2b may be displaced from the image scanning means 4. In such a case, the light detection unit 20 determines which of the projected images is out of alignment, and either one of the mirrors 6a and 6b, or
By adjusting the angles of the two mirrors 6a and 6b about the point where the theoretical optical axis and the surface of the mirror intersect,
The projected image of the test pattern 2b is generated near the center of the image scanning means.

The positional light intensity distribution of the projected image of the test pattern 2b generated on the image scanning means 4 is converted into a time series signal by the image scanning means 4, and the signal is A / D converted by the signal processing means 5. The performance of the test lens 3 can be inspected from the image formation state of the projected image of the test pattern 2b generated by the test lens 3 based on the MTF value, the image processing output, etc. by performing calculations and the like.

[0017]

Embodiment 1 FIGS. 3 and 4 show this embodiment, FIG. 3 is a schematic configuration diagram, and FIG. 4 is an enlarged front view of the chart of FIG. In FIG. 3, 3 is a lens to be inspected, and 1 is a halogen lamp as a light source. Reference numeral 7 is a chart. This chart 7 is formed of an opal glass plate as a transmissive light diffusing plate, and chromium is vapor-deposited on its surface as a light-shielding film, and the position is adjusted to a position corresponding to the image height to be inspected on and off the axis. Slit openings are arranged as a test pattern on the light-shielding film, and the surface thereof is oriented toward the lens 3 to be inspected and is installed perpendicularly to the optical axis.

As shown in FIG. 4, the chart 7 is provided with an on-axis image inspection test pattern 7a and off-axis image inspection test patterns 7b to 7e for inspecting off-axis projected images. The off-axis image inspection test patterns 7b to 7e have angular intervals α ₁ , α ₂ , respectively corresponding to the off-axis image inspection positions.
It is provided at α ₃ .

Reference numeral 6 is an optical path switching means rotatable about the optical axis of the lens 3 to be inspected, and is a mirror 6a which is arranged on the on-axis optical path 3a and can be appropriately avoided and a mirror 6b which is arranged on the off-axis optical path 3b. And the mirror 6a is the lens 3 to be inspected.
Of 45 degrees with respect to the optical axis of, and the off-axis image inspection position 6d where the off-axis light flux passing through the off-axis light path 3b is not eclipsed, or the on-axis light flux passing through the on-axis light path 3a is not eclipsed. The on-axis image inspection position 6c thus retracted can be appropriately switched. The mirror 6b arranged on the off-axis optical path 3b of the lens 3 to be tested rotates about an axis perpendicular to the plane of the drawing on the point where the off-axis optical path 3b of the lens 3 to be tested intersects with the mirror 6b. It is possible.

The off-axis optical path 3b is converted by the mirror 6b into a direction (optical path 3c) intersecting the axial optical path 3a at a right angle, and further converted by the mirror 6a into a direction coinciding with the axial optical path 3a. Reference numeral 8 denotes a collimator lens, the optical axis of which is installed coaxially with the optical axis of the lens 3 under test.

Reference numeral 9 denotes a CCD, which is installed on the image plane of the collimator lens 8 perpendicularly to the optical axis of the lens 3 to be inspected, and the scanning direction is centered on the optical axis of the lens 3 to be inspected. It is a one-dimensional CCD as an image scanning unit that can be rotated according to the rotation of the optical path switching unit 6 or the position of the mirror 6a so as to intersect the projection image of the test pattern of the chart perpendicularly. 21 is a PSD, this P
SD21 is a PSD as a light detecting means installed in the vicinity of the CCD 9 and rotates integrally with the CCD 9. 1
Reference numeral 0 denotes a signal processing means connected to the CCD 9 and comprising a signal processing device 10a capable of FFT and a monitor 10b.

In the apparatus having the above structure, the light beam emitted from the light source 1 is diffused evenly on the chart 7, and a part of the light beam is directed from the test pattern provided on the chart 7 toward the lens 3 to be inspected. Is ejected. First, the mirror 6a is installed at the on-axis image inspection position 6c. The on-axis light flux emitted from the on-axis image inspection test pattern 7a of the chart 7 passes through the on-axis optical path 3a and becomes a parallel light flux due to the focusing action of the lens 3 to be inspected. The on-axis light flux of the lens 3 under test, which has become a parallel light flux,
A projected image of the test pattern 7a is generated on the CCD 9 by the condensing action of the collimator lens 8 after passing through the axial optical path 3a.

At this time, the scanning direction of the CCD 9 is set perpendicular to the projected image of the test pattern 7a. CC
The positional light intensity distribution of the projected image of the test pattern 7a generated in D9 is converted into a time series signal by the CCD 9,
The signal is A / D converted / stored / stored by the signal processing device 10a.
MTF calculation by FFT is performed and MT is displayed on the monitor 10b.
By displaying the F value, it is possible to inspect the image formation state of the projected image of the test pattern 7a generated by the lens 3 to be inspected.

If the lens 3 to be inspected has an ideal property, the inspection can be performed as described above, but in reality, the eccentricity of the lens 3 to be inspected, the mounting error, and the like cause the test pattern 7a to be changed. The projected image may be off the CCD 9. In such a case, first, the lens 3 to be inspected is reattached and it is confirmed whether or not the projected image of the test pattern 7a for inspecting the image formation state on the axis enters the CCD 9. If the projected image does not enter the CCD 9, the lens 3 to be inspected is judged to be defective and the inspection is ended. When the projected image of the test pattern 7a for inspecting the on-axis image forming state is formed on the CCD 9, it is determined that the image forming position is displaced due to the improper mounting of the lens 3 to be inspected, and the measurement is continued to perform the inspection. I do.

Next, when the mirror 6a is installed at the off-axis image inspection position 6d, the on-axis light beam is blocked by the mirror 6a, and the off-axis light beam emitted from the test pattern 7b is focused by the lens 3 to be inspected. Will be a parallel light flux. The off-axis light flux that has become a parallel light flux is transmitted from the off-axis optical path 3b to the mirror 6b and the mirror 6b.
The optical path is switched by a and passes through the axial optical path 3a, and the focusing action of the collimator lens 8 produces a projected image of the test pattern 7b on the CCD 9.

At this time, the scanning direction of the CCD 9 is set perpendicular to the projected image of the test pattern 7b. CCD
The positional light intensity distribution of the projected image of the test pattern 7b generated in 9 is converted into a time series signal by the CCD 9, and the signal is A / D converted / stored / stored by the signal processing device 10a.
The MTF calculation by FT is performed and the MTF is displayed on the monitor 10b.
By displaying the value, it is possible to inspect the image formation state of the projected image of the test pattern 7b generated by the lens 3 to be inspected.

If the lens 3 to be inspected has an ideal property without eccentricity or the like, the inspection can be carried out as described above, but the lens 3 to be inspected has an eccentricity and the mirror 6b.
When the angle is set to a theoretical angle, for example, the off-axis light flux of the lens 3 to be inspected is switched to the optical path 3d by the mirror 6b and further switched to the optical path 3e by the mirror 6a, and the optical path is changed to the lens 3 to be inspected. Does not match the on-axis optical path 3a, and the projected image of the test pattern 7b is not formed on the CCD 9.

In such a case, the deviation direction of the projected image of the test pattern 7b can be detected by the output of the PSD 21, so that the swing angle of the mirror 6b is determined by the off-axis optical path 3b of the lens 3 to be inspected. 6B is rotated about an axis perpendicular to the plane of the drawing on which the point 6b intersects, and the optical path 3e is aligned with the axial optical path 3a, and a projected image is formed on the CCD 9 for inspection.

In the above example, the case where the mirror 6b can rotate about an axis perpendicular to the plane of the paper on the point where the off-axis optical path 3b of the lens 3 to be examined and the mirror 6b intersect is shown. Is the on-axis optical path of the lens 3 to be inspected and the mirror 6
It is clear that the same effect can be obtained even when the angle is variable with the axis perpendicular to the paper surface at the point where d intersects as the center of gravity. As described above, even when the off-axis image inspection test pattern is not imaged on the CCD 9 due to the eccentricity of the lens 3 to be inspected, it is formed on the CCD 9 by adjusting the swing angle of the mirror 6a or 6b of the optical path switching means 6. It becomes possible to inspect the off-axis image formation state by forming an image.

Further, the mirror 6a is moved to the off-axis image inspection position 6d.
The optical path switching means 6 and the CCD 9 are respectively rotated while being installed in the above position, and stopped at every installation angle α _{1 to} α _{3 of the} test pattern for off-axis image inspection. When the projected image of the lens 6 deviates from the CCD 9, the swing angle of the mirror 6b is centered around the axis perpendicular to the plane of the paper on the point where the off-axis optical path 3b of the lens 3 to be examined and the mirror 6b intersect. By adjusting by changing the angle, the projected images of the test patterns 7c to 7e are imaged on the CCD 9 and the image formation state is inspected, and the test patterns of a plurality of image heights including the axis of the lens 3 to be inspected are formed. The image formation state of the projected image can be inspected.

According to this embodiment, the rotation axes of the mirror 6a and the mirror 6b are only one axis, and the structure is simple. Further, since the optical path of the test pattern projection image is a parallel light beam from the lens 3 to be inspected to the collimator lens 8, the lens 3 to be inspected, the optical path switching means 6 and the collimator lens 8 are relatively flexible. There is.

Although not shown in this embodiment,
The swing angle control of the mirror 6b can be automatically performed from the output of the PSD 21 by a motor and a computer.

[0033]

Second Embodiment FIGS. 5 to 7 show the present embodiment, FIG. 5 is a schematic configuration diagram, FIG. 6 is an enlarged front view of the chart of FIG. 5, and FIG. 7 is an enlarged front view of the CCD 12 and PSD 22 of FIG. is there.
In FIG. 5, 3 is a lens to be inspected, and 1 is a halogen lamp as a light source. 11 is a chart, and this chart 1
Reference numeral 1 is formed of an opal glass plate as a transmissive light diffusing plate, and chromium vapor deposition is applied to its surface as a light-shielding film, and a pinhole opening is formed on the light-shielding film at a position corresponding to the image height to be inspected on and off the axis. Is arranged as a test pattern, the surface of which is directed toward the lens 3 to be inspected and is set perpendicularly to the optical axis.

As shown in FIG. 6, the chart 11 is provided with an on-axis image inspection test pattern 11a and off-axis image inspection test patterns 11b to 11e for inspecting an off-axis projected image. Off-axis image inspection test pattern 11b-
11e is an angular interval α corresponding to each off-axis image inspection position.
It is provided with ₁ , α ₂ , and α ₃ .

Reference numeral 6 is an optical path switching means rotatable about the optical axis of the lens 3 to be inspected, and is a mirror 6a which is arranged on the on-axis optical path 3a and can be appropriately avoided and a mirror 6b which is arranged on the off-axis optical path 3b. And the mirror 6a is the lens 3 to be inspected.
Of 45 degrees with respect to the optical axis of, and the off-axis image inspection position 6d where the off-axis light flux passing through the off-axis light path 3b is not eclipsed, or the on-axis light flux passing through the on-axis light path 3a is not eclipsed. The on-axis image inspection position 6c thus retracted can be appropriately switched. The mirror 6b arranged on the off-axis optical path 3b of the lens 3 to be tested rotates about an axis perpendicular to the plane of the drawing on the point where the off-axis optical path 3b of the lens 3 to be tested intersects with the mirror 6b. It is possible.

The off-axis optical path 3b is converted by the mirror 6b into a direction (optical path 3c) which intersects the on-axis optical path 3a at a right angle, and further converted by the mirror 6a into a direction coinciding with the on-axis optical path 3a. The optical path switching means 6 is set so that the on-axis optical path length L and the off-axis optical path length L'are equal to those when the optical path switching means 6 does not exist, with reference to the inspected lens exit pupil position 3f. Is ω, the angle between the on-axis optical path 3a and the off-axis optical path 3b is ω, the distance to the optical path switching means 6 is l, and the mirror 6 at the off-axis inspection position 6d.
When the distance between a and the mirror 6b is m, and the angle formed between the mirror 6b and the optical axis of the lens 3 under test is θ, 1 = L ×
(1-cosω) / (1 + sinω-cosω), m =
1 × tan ω, θ = (π / 4) − (ω / 2), and the off-axis optical path 3b intersects the on-axis optical path 3a at a right angle by the mirror 6b (optical path 3c ′). And is further converted by the mirror 6a in a direction in which the on-axis optical path 3a coincides.

Reference numeral 12 denotes a CCD. This CCD 12 is a two-dimensional image scanning means installed as an image scanning means on the image forming surface 14 of the projected image of the test pattern of the chart 11 perpendicularly to the optical axis of the lens 3 to be inspected. It is a CCD. Reference numeral 22 denotes a PSD, which is a PSD as a light detecting means installed in the vicinity of the CCD as shown in FIG. 13 is the CCD 12
The signal processing means is composed of a signal processing device 13a capable of FFT and a monitor 13b which are connected to each other.

In the apparatus having the above structure, the light beam emitted from the light source 1 is diffused evenly on the chart 11, and a part of the light beam is directed from the test pattern provided on the chart 11 toward the lens 3 to be inspected. Is ejected. First, the mirror 6
Set a at the on-axis image inspection position 6c. The on-axis light beam emitted from the on-axis image inspection test pattern 11a of the chart 11 passes through the on-axis optical path 3a, and a focusing image of the lens 3 to be inspected produces a projected image of the test pattern 11a on the CCD 12.

Test pattern 1 generated on CCD 12
The positional light intensity distribution of the projected image of 1a is converted into a time series signal by the CCD 12, and the signal is subjected to A / D conversion / storage / MTF calculation by FFT in two dimensions in the vertical and horizontal directions by the signal processing device 13a. Done, monitor 13b
If the MTF value is displayed on the screen, the image formation state of the projected image of the test pattern 11a generated by the lens 3 to be inspected is displayed in the vertical and horizontal directions.
Can be inspected in the direction. If the lens 3 to be inspected has an ideal property without eccentricity or the like, the inspection can be performed as described above. However, in reality, the test pattern 11a may be caused by the eccentricity of the lens 3 to be inspected or an attachment error.
There is a case where the projected image of is out of the CCD 12.

In such a case, first, the lens 3 to be inspected is reattached, and it is confirmed whether or not the projected image of the test pattern 11a for inspecting the image formation state on the axis enters the CCD 12. If the projected image does not enter the CCD 12, the lens 3 to be inspected is judged to be defective and the inspection is ended. Test pattern 1 for inspecting on-axis image formation
When the projected image of 1a is formed on the CCD 12, it is determined that the image forming position is displaced due to the improper mounting of the lens 3 to be inspected, and the measurement is continued to perform the inspection.

Next, when the mirror 6a is installed at the off-axis image inspection position 6d, the on-axis light beam is blocked by the mirror 6a, and the off-axis light beam emitted from the test pattern 11b is passed from the off-axis optical path 3b to the mirror 6b. The optical path is switched by the mirror 6a and the mirror 6a to pass through the on-axis optical path 3a, and by the focusing action of the lens 3 to be inspected, a projected image of the test pattern 11b is generated on the CCD 12.

Test pattern 1 generated on CCD 12
The positional light intensity distribution of the projected image of 1b is converted into a time-series signal by the CCD 12, and the signal is processed by the signal processing device 13a for A / D conversion, storage, and an off-axis image inspection position. If the MTF calculation by FFT is performed in two dimensions and the MTF value is displayed on the monitor 13b, the projected state of the projected image of the test pattern 11b generated by the lens 3 to be inspected is divided into the tangential direction and the normal direction. Can be inspected in dimensions.

Assuming that the lens 3 to be inspected has an ideal property without eccentricity or the like, the above is obtained.
Is decentered and the angle of the mirror 6b is set to a theoretical angle, for example, the off-axis light flux of the lens 3 to be inspected is switched to the optical path 3d by the mirror 6b and further switched to the optical path 3e by the mirror 6a. , Its optical path does not coincide with the on-axis optical path 3a of the lens 3 under test, and the test pattern 1
The projected image of 1b is not formed on the CCD 12. Also,
When the test pattern has a short width such as a pinhole, the test pattern projection image is easily transferred to the CCD 1 due to the deviation of the test pattern projection image in the direction perpendicular to the paper surface.
There is a possibility that it will deviate from 2.

In such a case, the deviation direction of the test pattern projection image can be detected by the output of the PSD 22, so that the swing angle of the mirror 6b can be changed to the lens 3 to be inspected.
2 at the point where the off-axis optical path 3b and the mirror 6b intersect
The angle is adjusted three-dimensionally, the optical path 3e is aligned with the on-axis optical path 3a, and the projected image of the test pattern for off-axis image inspection is transferred to the CCD 12.
The inspection is performed by forming an image on the top. In the above example, the mirror 6
Although b shows the case where the angle can be two-dimensionally adjusted at the point where the off-axis optical path 3b of the lens 3 to be inspected and the mirror 6b intersect, the mirror 6a shows the on-axis optical path of the lens 3 to be inspected and the mirror 6b.
It is obvious that the same effect can be obtained even when the angle can be changed two-dimensionally at the point where d intersects.

As described above, even when the off-axis image inspection test pattern is not formed on the CCD 12 due to the decentering of the lens 3 to be inspected, the mirror 6a or 6 of the optical path switching means 6 is formed.
By adjusting the swing angle of b two-dimensionally, the CCD 12
It is possible to inspect the off-axis image formation state by forming an image on top.

Further, the mirror 6a is moved to the off-axis image inspection position 6d.
The optical path switching means 6 is rotated while it is installed in the optical axis, and stopped at every off-axis image inspection test pattern installation angle α _{1 to} α ₃ , and the projected image of the off-axis image inspection test pattern is transferred from the CCD 12 in the same manner as above. When the test patterns 11c to 11e are deviated, the swing angle of the mirror 6b is adjusted two-dimensionally at a point where the off-axis optical path 3b of the lens 3 to be examined and the mirror 6b intersect each time. If the projected image is formed on the CCD 12 and the image formation state is inspected,
It is possible to inspect the image formation state of the projected image of the test pattern having a plurality of image heights including the axis of the lens 3 to be inspected.

According to this embodiment, it is possible to inspect the image formation state of an image in any direction with only one type of chart test pattern.

Also in this embodiment, similarly to the first embodiment, the swing angle control of the mirror 6b can be automatically performed from the output of the PSD 22 by the motor and the computer.

[0049]

[Third Embodiment] FIGS. 8 and 9A and 9B show the present embodiment.
8 is a schematic configuration diagram, and FIGS. 9a and 9b are CCDs of FIG. 8, respectively.
FIG. 15 is an enlarged front view of 15. In FIG. 8, 3 is a lens to be inspected and 1 is a halogen lamp as a light source. Reference numeral 7 is a chart. This chart 7 is formed of an opal glass plate as a transmissive light diffusing plate, and the surface thereof is subjected to chromium vapor deposition as a light-shielding film to a position corresponding to the image height to be inspected on-axis and off-axis. Slit openings are arranged as a test pattern on the light-shielding film, and the surface thereof is oriented toward the lens 3 to be inspected and is installed perpendicularly to the optical axis.

As shown in FIG. 4, the chart 7 is provided with an on-axis image inspection test pattern 7a and off-axis inspection test patterns 7b to 7e for inspecting an off-axis projection image. The off-axis image inspection test patterns 7b to 7e have angular intervals α ₁ , α ₂ , α corresponding to the off-axis image inspection positions, respectively.
It is provided in ₃ .

Reference numeral 6 is an optical path switching means rotatable about the optical axis of the lens 3 to be inspected, and is a mirror 6a which is arranged on the on-axis optical path 3a and can be appropriately avoided and a mirror 6b which is arranged on the off-axis optical path 3b. And the mirror 6a is the lens 3 to be inspected.
Off the off-axis light beam passing through the off-axis optical path 3b at an angle of 45 degrees with respect to the optical axis of the off-axis image inspection position 6d or on-axis light beam passing through the on-axis optical path 3a. The on-axis image inspection position 6c retracted to is properly switched. The mirror 6b arranged on the off-axis optical path 3b of the lens 3 to be inspected is rotatable with respect to an axis perpendicular to the paper surface at the point where the off-axis optical path 3b of the lens 3 to be inspected and the mirror 6b intersect. Has become.

The off-axis optical path 3b is converted by the mirror 6b into a direction (optical path 3c) intersecting the axial optical path 3a at a right angle, and further converted by the mirror 6a into a direction coinciding with the axial optical path 3a. The optical path switching means 6 is set so that the on-axis optical path length L and the off-axis optical path length L'are equal to those when the optical path switching means 6 does not exist, with reference to the inspected lens exit pupil position 3f. Is the on-axis optical path 3a
Is ω, the distance to the optical path switching means 6 is l, the distance between the mirror 6a and the mirror 6b at the off-axis inspection position 6d is m, the mirror 6b and the lens 3 to be inspected. When the angle formed with the optical axis is θ, l = L ×
(1-cosω) / (1 + sinω-cosω), m =
It is installed at a position of l × tan ω, θ = (π × 4) − (ω / 2), and the off-axis optical path 3b is converted by the mirror 6b into a direction (optical path 3c) that intersects the on-axis optical path 3a at a right angle. Then, the light is converted by the mirror 6a into a direction that matches the on-axis optical path 3a.

Reference numeral 15 denotes a CCD, which is installed on the image plane 14 of the projected image of the test pattern of the chart 7 perpendicularly to the optical axis of the lens 3 to be inspected.
One-dimensional CCD 15a and CCD 15b as scanning means rotatable in correspondence with the rotation of the optical path switching means 6 so that the scanning direction intersects at right angles with the projected image of the test pattern on the chart 7 around the optical axis of the. Two and are arranged in parallel with a certain distance. 21 is P
In SD, the PSD 21 is a PSD as a photodetector installed in the vicinity of the CCD 15, and rotates together with the CCD 15. 16 is an FFT connected to the CCD 15
The signal processing means includes a signal processing device 16a and a monitor 16b capable of performing the above.

In the apparatus having the above structure, the light beam emitted from the light source 1 is uniformly diffused on the chart 7, and a part of the light beam is emitted from the test pattern provided on the chart 7 toward the lens 3 to be inspected. It First, the mirror 6a is installed at the on-axis image inspection position 6c. The on-axis light beam emitted from the on-axis image inspection test pattern 7a of the chart 7 is transmitted through the on-axis optical path 3
Passing a, the focusing action of the lens 3 under test causes the CCD 15
Then, a projected image of the test pattern 7a is generated.

Test pattern 7 generated on CCD 15
The positional light intensity distribution of the projected image of a is converted into a time-series signal by the CCD 15, and the signal is subjected to A / D conversion, storage, and MFT calculation by FFT by the signal processing device 16a, and the MTF value is displayed on the monitor 16b. Then, it is possible to inspect the image formation state of the projected image of the test pattern 7a generated by the lens 3 to be inspected.

If the lens 3 to be inspected has an ideal property with no eccentricity or the like, the inspection can be performed as described above, but in reality, due to the eccentricity of the lens 3 to be inspected and the mounting error, etc. The projected image of the test pattern 7a may be off the CCD 15. In such a case, first, the lens 3 to be inspected is reattached and it is confirmed whether or not the projected image of the test pattern 7a for inspecting the image formation state on the axis enters the CCD 15. If the projected image does not enter the CCD 15, the lens 3 to be inspected is judged to be defective and the inspection is ended. When the projected image of the test pattern 7a for inspecting the on-axis image formation state is formed on the CCD 15,
It is determined that the image forming position is displaced due to the mounting failure of the lens 3 to be inspected, and the measurement is continued to perform the inspection.

Next, when the mirror 6a is installed at the off-axis image inspection position 6d, the on-axis light beam is blocked by the mirror 6a, and the off-axis light beam emitted from the test pattern 7b is transmitted from the off-axis optical path 3b to the mirror 6b. The optical path is switched by the mirror 6a and the mirror 6a to pass through the on-axis optical path 3a, and by the focusing action of the lens 3 to be inspected, a projected image of the test pattern 7b is generated on the CCD 15. At this time, the scanning direction of the CCD 15 is set to be perpendicular to the projected image of the test pattern 7b.

Test pattern 7 generated on CCD 15
The positional light intensity distribution of the projected image of b is converted into a time series signal by the CCD 15, and the signal is subjected to MTF calculation by A / D conversion, storage, and FFT by the signal processing device 16a, and the MTF value is displayed on the monitor 13b. If it is shown, it is possible to inspect the image formation state of the projected image of the test pattern 7b generated by the lens 3 to be inspected.

If the lens 3 to be inspected has an ideal property without eccentricity or the like, the inspection can be performed as described above. However, the lens 3 to be inspected has an eccentricity and the mirror 6a.
When the angle of the mirror 6b is set to a theoretical angle, for example, the off-axis light flux of the lens 3 to be inspected is switched to the optical path 3d by the mirror 6b, and further switched to the optical path 3e by the mirror 6a. It does not match the on-axis optical path 3a of the inspection lens 3, and the projected image of the test pattern 7b is not formed on the CCD 15.

In such a case, the deviation direction of the test pattern projection image can be detected by the output of the PSD 21, so that the swing angle of the mirror 6b can be determined by the lens 3 to be inspected.
The off-axis image inspection test pattern is made to match the optical path 3e with the on-axis optical path 3a by changing the angle about the axis perpendicular to the paper surface at the intersection of the off-axis optical path 3b and the mirror 6b. The inspection is performed by forming a projected image on the CCD 15.

If the projected image is displaced in the length direction of the slit, which is the test pattern, and the projected image for the off-axis inspection test pattern is formed on only one of the CCD 15a and the CCD 15b, the mirror 6a is used. The mirror 6a is rotated about the line of intersection of the mirror surface and the paper surface at 6d, and the image formation position is moved on a plane perpendicular to the paper surface so that the off-axis inspection test pattern projection images are generated by both the CCD 15a and the CCD 15b. To form an image at.

Even if the direction of the slits on the chart 7 is tilted with respect to the measurement direction at the off-axis position, the CCD 15 is set to the position shown in FIG.
As shown in a and b, the CCD 15a and the CCD 15b are rotated so that the positional light intensity distributions of the off-axis inspection test patterns are the same, so that the CCD 15 is easily made perpendicular to the off-axis inspection test pattern. It is possible. It is clear that the same effect can be obtained even if the two mirrors 6a and 6b in the above example have opposite rotation directions. Thus, even if the off-axis image inspection test pattern is not imaged on the CCD 15 due to the eccentricity of the lens 3 to be inspected, by adjusting the swing angle of the mirror 6a or 6b of the optical path switching means 6 to the CCD 15 respectively. It is possible to form an image and inspect the image formation state of the off-axis image.

Further, the mirror 6a is moved to the off-axis image detection position 6d.
The optical path switching means 6 and the CCD 15 and the PSD 21 are respectively rotated while being installed in the above position to stop at each of the off-axis image inspection test pattern installation angles α _{1 to} α ₃ and, similarly to the above, the off-axis image inspection test. The projected image of the pattern is CCD
When it is deviated from 15, the projected images of the test patterns 7c to 7e are formed on the CCD 15 by adjusting the swing angles of the mirror 6a and the mirror 6b each time, and the image formation state is inspected. It is possible to inspect the image formation state of the projected image of the test pattern having a plurality of image heights including the axis of the inspection lens 3.

According to this embodiment, even if the direction of the slit is inclined with respect to the measurement direction of the off-axis position, the CCD 1 can be easily operated.
Since 5 can be set perpendicularly to the test pattern for off-axis image inspection, the measurement accuracy is improved.

Also in this embodiment, similarly to the above-mentioned respective embodiments, the swing angle control of the mirror 6b can be automatically performed from the output of the PSD 21 by the motor and the computer.

[0066]

As described above, according to the lens performance inspection apparatus of the present invention, the test pattern projection image is formed at an arbitrary position on the image scanning means without being affected by the eccentricity of the lens to be inspected. Can be made.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the present invention.

FIG. 2 is a conceptual diagram showing the present invention.

FIG. 3 is a schematic configuration diagram showing a first embodiment.

FIG. 4 is an enlarged front view of essential parts showing the first embodiment.

FIG. 5 is a schematic configuration diagram showing a second embodiment.

FIG. 6 is an enlarged front view of essential parts showing a second embodiment.

FIG. 7 is an enlarged front view of essential parts showing a second embodiment.

FIG. 8 is a schematic configuration diagram showing a third embodiment.

FIG. 9A and FIG. 9B are enlarged front views of essential parts showing the third embodiment.

[Explanation of symbols]

 1 light source 2 chart 3 lens to be inspected 4 image scanning means 5 signal processing means 6 optical path switching means 20 light detecting means

Claims (1)

[Claims] 1. A light source, a chart provided with a test pattern illuminated by a light beam from the light source, a test lens for forming a projected image of the test pattern of the chart, and a positional light intensity of the projected image. An image scanning means for converting the distribution into a time series signal, a signal processing means for processing a signal from the image scanning means, and an on-axis light beam and an off-axis light beam installed on the optical axis of the lens to be inspected. The optical path switching means is composed of a mirror which makes a part of the light beam coaxial and which can be appropriately avoided, and a mirror arranged on the off-axis optical path, and forms a plurality of image heights including the axis of the lens to be inspected. In a lens performance inspecting device for inspecting image performance, a plurality of light detecting means are arranged in the vicinity of the image scanning means, and at least one of the mirror on the optical axis and the mirror on the off-axis optical path is arbitrary. Can be set to any angle A lens performance inspection device characterized in that