JP5202011B2 - Lens meter - Google Patents

Description

  The present invention relates to a lens meter that measures optical characteristics of a lens to be examined.

The measurement light beam is projected onto the test lens, and the measurement light beam transmitted through the test lens is detected by the light receiving element. Based on the detection result, the optical characteristics of the test lens (spherical power S, column surface power C, and column surface) Lens meters having a measuring optical system for obtaining an axial angle A) are known. This type of conventional lens meter is based on the deviation of the measurement index detected by the light receiving element with a set of four measurement indices (in principle, three measurement indices) around the measurement optical axis. It was set as the structure which measures the optical characteristic of a lens (for example, refer patent document 1, 2). In addition, a lens meter using a large number of measurement indexes arranged in the nosepiece has been proposed in order to easily measure the distribution of optical characteristics of the lens to be measured and the distance and near portions of the progressive lens. (For example, refer to Patent Document 3). In any lens meter, since the influence of the aberration increases as the measurement index moves away from the measurement optical axis in the measurement of the single focus lens, basically, it is on the circumference having a diameter of 2 to 3 mm around the measurement optical axis. Measurements were made using measurement indicators placed in
Japanese Unexamined Patent Publication No. 60-17335 JP 50-145249 A JP 2003-75296 A

  However, in the measurement based on the measurement index near the measurement optical axis, the measurement of the optical characteristics becomes unstable depending on the lens power and the state of the lens surface, and the reliability of the measurement accuracy may be inferior. That is, when the refractive power of the lens is a weak power, the measured value tends to be unstable because the deviation of the index near the optical axis is small. In particular, when the column surface frequency is weak, the column surface axis angle varies greatly, resulting in an unstable measurement result, resulting in poor measurement accuracy. Further, in measurement using an index near the measurement optical axis, even when there are scratches or dirt in the measurement region, the measurement value is not stable, and the reliability of measurement accuracy is poor.

  An object of the present invention is to provide a lens meter that can stably and accurately obtain optical characteristics of a lens in view of the above-described problems of the prior art.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) In a lens meter that measures optical characteristics of a lens to be measured and displays a measurement result on a display means, an index plate having a large number of measurement indexes arranged in a predetermined pattern around a measurement optical axis, An index plate having a measurement index including a first measurement index in a first area close to the measurement optical axis and a second measurement index in a second area outside the first area; and the index plate and the test lens A measurement optical system having a light receiving element that receives the measurement light flux that has passed, and
Computation means for computing the optical characteristics of the single focus lens based on the measurement index detected by the light receiving element, and based on the detection result of the first measurement index, the spherical power, column surface power, and column surface axis of the lens An operation for calculating a first optical characteristic including an angle and calculating a second optical characteristic including a spherical power, a column surface power, and a column surface axis angle of the lens based on detection results of the first measurement index and the second measurement index. Means,
When the column surface frequency of the first optical characteristic calculated by the calculation means is equal to or less than a predetermined weak power level that is set to be less affected by aberrations by using the second measurement index, or a column surface frequency And the second optical characteristic as the measurement result of the test lens when both the spherical power and the spherical power are equal to or lower than a predetermined weak power set to be less affected by the aberration caused by using the second measurement index. The first optical characteristic is displayed when the column surface power of the first optical characteristic is higher than the predetermined weak power, or when both the column power and the spherical power are higher than the predetermined weak power. Measurement control means for displaying on the display means as a measurement result of the test lens ;
A lens meter comprising:
(2) In a lens meter that measures the optical characteristics of the test lens and displays the measurement result on the display means,
An index plate having a large number of measurement indexes arranged in a predetermined pattern around a measurement optical axis, the first measurement index in a first region close to the measurement optical axis and a second region outside the first region A measurement optical system having an index plate having a measurement index including the second measurement index and a light receiving element that receives the measurement light beam that has passed through the index plate and the test lens;
Computation means for computing the optical characteristics of the single focus lens based on the measurement index detected by the light receiving element, and based on the detection result of the first measurement index, the spherical power, column surface power, and column surface axis of the lens An operation for calculating a first optical characteristic including an angle and calculating a second optical characteristic including a spherical power, a column surface power, and a column surface axis angle of the lens based on detection results of the first measurement index and the second measurement index. Means,
When the column surface frequency of the first optical characteristic calculated by the calculation means is equal to or less than a predetermined weak power level that is set to be less affected by aberrations by using the second measurement index, or a column surface frequency And the spherical power and the spherical surface power of the first optical characteristic when both the spherical power and the spherical power are equal to or lower than a predetermined weak power set to be less affected by the aberration caused by using the second measurement index. And the spherical optical power and the cylindrical surface power of the second optical characteristic are compared, and when both the spherical power and the cylindrical surface power are within a predetermined tolerance, the second optical characteristic is When the column surface power of the first optical characteristic is stronger than the predetermined weak power, or when both the column surface power and the spherical power are stronger than the predetermined weak power, the measurement unit displays the measurement result. The first optical characteristic Measurement control means for displaying on the display unit as a measurement result of the subject lens, and
Lens meter, characterized in that it comprises a.

  According to the present invention, the optical characteristics of the lens can be obtained stably and accurately.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an appearance of a lens meter according to the embodiment.

  Reference numeral 1 denotes a lens meter main body. Reference numeral 2 denotes a display composed of an LCD or the like, which displays information necessary for measurement such as measurement results and alignment targets. Reference numeral 3 denotes an input switch. When a switch corresponding to the switch display displayed on the display 2 is pressed, a necessary input instruction such as switching of the measurement mode is performed. Reference numeral 4 denotes a nosepiece on which a test lens LE is placed and which serves as a base point during measurement. Reference numeral 5 denotes a lens presser. By lowering the lens presser 5, the test lens LE placed on the nosepiece 4 can be stably held.

  Reference numeral 6 denotes a lens pad that is movable in the front-rear direction. In measurement of a lens with a spectacle frame, it is brought into contact with the lower part of the frame (the lower part in the spectacle wearing state) and is stabilized, thereby providing a reference for measuring Axis (columnar axis angle) create. Reference numeral 7 denotes a marking mechanism used when marking is applied to the lens LE. Reference numeral 8 denotes a READ switch for reading optical characteristic data of the test lens LE. By pressing the READ switch 8, the measured value is held on the display 2 and stored in the apparatus.

  FIG. 2 is a diagram showing an optical system and a control system. Reference numeral 20 denotes a measurement optical system, and L1 denotes its measurement optical axis. The measurement optical system 20 includes a measurement light source 21 such as an LED disposed on the optical axis L1, a collimating lens 22, a grid plate 23 on which a measurement index is formed, and a two-dimensional image sensor 24 as a light receiving element. The optical axis L1 passes through the center of the opening 4a of the nosepiece 4 and is disposed perpendicular to the opening plane of the opening 4a. The grid plate 23 is disposed in the vicinity of the nosepiece opening 4a. The distance between the image sensor 24 and the upper end of the nosepiece 4 (the rear vertex of the lens LE) is designed to be smaller than the minimum focal length within the measurement range of the lens LE.

  The grid plate 23 may be arranged on the light source 21 side from the lens LE to be placed on the nosepiece 4. Further, the measurement index may be configured by two-dimensionally arranging the light sources 21 so as to obtain a measurement light beam similar to that of the grid plate 23.

  The index pattern of the measurement index that the grid plate 23 has is shown in FIG. In this example, a large number of geometrically arranged circular holes 25 (dot indices) as measurement indices are arranged in a grid pattern at intervals of 0.5 mm. The holes 25 are arranged in a 9 × 9 arrangement, but more holes 25 may be arranged in a range in which the measurement light passes through the opening of the nosepiece 4. In this example, the distance between the centers of the holes 25 is equal to 0.5 mm. However, the distance is not limited to this as long as it has a predetermined geometric arrangement. Of the holes 25, a hole (fourth measurement index) H5 on the optical axis L1 and a hole (fifth measurement index) H1 located at a square corner with a side length of 2 mm around the hole H5. , H2, H3, and H4 are formed to have a diameter of 0.5 mm. The holes 25 other than the holes H1 to H5 are formed with a diameter of 0.2 mm. The holes H1 to H4 arranged in a fixed relationship with the central hole H5 and the hole H5 are detected by being distinguished from other holes 25 having different sizes. The center hole H5 is used for detecting the reference position of the deviation of each hole 25 received by the image sensor 24. When the center hole H5 is not normally detected due to scratches or dirt on the lens LE, the holes H1 to H4 are substituted. The group of holes H1 to H4 is a region that can be measured even when a small diameter nosepiece for a contact lens is used.

  The light beam from the light source 21 is converted into a parallel light beam by the collimating lens 22 and projected onto the lens LE. Of the transmitted light flux, the light flux that has passed through the holes 25 of the grid plate 23 reaches the image sensor 24. An output signal from the image sensor 24 is input to the control unit 40. Connected to the control unit 40 are a memory 41 for storing calculation results, and a display circuit 42 for displaying information such as calculation results on the display 2.

  Further, the control unit 40 obtains the measurement obtained when the lens LE having refractive power is placed on the basis of the position of the image (measurement index) of the hole 25 that reaches the image sensor 24 through the grid plate 23 when there is no lens LE. The optical characteristics (spherical power S, column surface frequency C, column surface axis angle A, prism power) of the lens LE are calculated from the positional deviation of the index. Basically, when a lens LE having only a spherical power is placed, each hole image is enlarged or reduced in a circular shape from the optical center of the lens LE, compared to the case where there is no lens LE. The spherical power S is obtained based on this enlargement or reduction deviation. When the lens LE having only the columnar power C is placed, each hole image is deviated by being enlarged or reduced from the center of the columnar axis of the lens LE. The column surface frequency C is obtained by this enlargement or reduction deviation. The column surface axis angle A is obtained as the center axis of the displacement. Further, the prism power is obtained from the amount of parallel movement of the hole H5 or a hole in the vicinity thereof. The lens LE having a spherical power and a columnar power may be considered as a composite of these (the same method as described in Japanese Patent Laid-Open Nos. 60-17335, 50-145249, etc. can be used). ).

  When using a large number of measurement indexes, use 5 × 5 (25), 7 × 7 (49), etc., which are 2 to 3 mm in diameter with the measurement optical axis L1 as the center. Preferably, the optical characteristics of the single-focus lens can be obtained with high accuracy by calculating the average of the optical characteristics of all sets obtained by setting four or three adjacent indexes as one set. In addition, the index of 5 × 5 (25), 7 × 7 (49), etc. is most fitted by applying the least square method using the ray tracing method based on the detection result of the deviation of each target. Alternatively, a method of calculating optical characteristics may be used by obtaining a regression plane of S, C, and A. In contrast to the conventional calculation of only one set of optical characteristics using four or three indices, the optical characteristics of the single focus lens can be obtained with high accuracy by using a larger number of indices.

  When measuring a progressive lens, the distribution of optical characteristics in a minute portion of the progressive lens can be obtained by calculating the optical characteristics with a set of four adjacent (at least three) indexes (holes 25). That is, a distribution of optical characteristics in the opening of the nosepiece 4 is obtained. Thereby, in the measurement of the progressive lens, it can be efficiently determined whether or not the current measurement position is in the distance portion, and similarly, it can be efficiently determined whether or not the current measurement position is in the near portion.

  Here, when measuring the optical characteristics of the single focus lens, the influence of the aberration increases as the measurement index hole 25 moves away from the measurement optical axis L1, so that basically the central hole H5 where the measurement optical axis L1 is located. The optical characteristics of the lens LE are calculated by using at least three measurement indexes arranged in a nearby small area (within a diameter of 2 to 3 mm) (first calculation). For example, the optical characteristics are calculated based on detection results of 25 indexes of 5 × 5 or 49 indexes of 7 × 7 with H5 as the center. However, in measurement using an index in the vicinity of the measurement optical axis L1, when the refractive power of the lens LE is weak, the deviation of the index is small, so that each measurement value is likely to be unstable, and the reliability of measurement accuracy is poor. . In particular, when the column surface frequency C is a weak frequency, the calculation result of the column surface axis angle becomes unstable, and the reliability of measurement accuracy also deteriorates.

  Therefore, in this apparatus, when the column surface power C is equal to or lower than the predetermined weak power, the number of measurement regions and measurement indexes is expanded with respect to a small region (in a region having a diameter of 2 to 3 mm) near the measurement optical axis L1 ( Increase) to calculate the optical characteristics (second calculation). When the column surface frequency C is a weak power, even if the range of the measurement region from the measurement optical axis L1 is widened, the influence of the aberration is small, so the measurement accuracy of the column surface axis angle due to the increase in the number of measurement indices Improvement and stability. Hereinafter, an example of the operation will be described based on the flowchart of FIG.

  The measurement mode of the apparatus includes a mode for measuring a single focus lens and a mode for measuring a progressive lens. Here, the measurement mode of the single focus lens is selected. The examiner presses a switch for designating left / right selection of the lens displayed on the display 2 to select the left / right of the lens to be measured.

  When the lens LE is placed on the nosepiece 4, the control unit 40 selects 7 × 7 (centered on the optical axis L <b> 1 among many index images (images of the holes 25) detected by the image sensor 24. Each measured value (S, C, A, prism frequency) is calculated based on the deviation of the 49 index images (S-1). FIG. 5A is an example of an alignment screen displayed on the display 2 at this time. Reference numeral 50 denotes an alignment reticle, and reference numerals 51 and 52 denote measurement value display units for displaying respective measurement values on the left and right sides. The display of the mark 53 indicates that the right lens is currently measured. Each measurement value obtained at this time is displayed on the right measurement value display unit 51. Further, the ring target 54 is displayed on the display 2 based on the deviation direction of the optical center with respect to the optical axis L1 of the lens LE and the prism power that is the amount of deviation. Further, the display position of the ring target 54 may be obtained based on the detection results of the holes H1 to H5, and alignment may be performed.

  When the lens LE is moved and the prism power (Δ) is less than 0.5Δ, the ring target 54 is switched to the cross target 55 (see FIG. 5B). If only the frequency is to be measured, the measured value is held by pressing the READ switch 8 in this state. When marking the lens LE, the lens LE is moved so that the cross target 55 is directed to the center of the reticle 50 for more accurate alignment. When the prism power becomes less than 0.1Δ, the cross target 55 is switched to the great cross target 57. Thereby, the examiner can know that precise alignment has been completed.

  In the measurement of such a single focus lens, the calculation of the optical characteristics by the control unit 40 is continuously performed at regular time intervals. At this time, the control unit 40 has a column surface power of a predetermined weak power δcD among optical characteristics obtained based on the deviation of 7 × 7 (49) index images arranged around the optical axis L1. It is determined whether (and spherical power is εsD, D: diopter) or less (S-2). For example, δcD is a weak reading of −0.5D or less with the column face frequency being negatively read.

  When the column surface power is less than δcD (and the spherical power is εsD), even if the number of measurement areas and indices is increased, the effect of aberration is small, so the stability of the measurement value and the accuracy of the column surface axis angle are improved. Therefore, the optical characteristics are calculated by enlarging the number of normal 7 × 7 (49) measurement areas and indices. The control unit 40 increases the number of measurement indexes by expanding the measurement area separately from the calculation of the optical characteristics by the 7 × 7 holes 25, and 9 × 9 centering on the central hole H 5. The optical characteristics of (81) index images are calculated (S-3).

  Here, preferably, the following determination condition is further provided (only the next determination condition can be a single condition). The control unit 40 compares each measurement value calculated by 7 × 7 and the measurement value calculated by 9 × 9. As a result of comparing each measurement value, it is determined whether or not each measurement value falls within the allowable error range (S-4). In this embodiment, if the difference between the spherical power and the column surface power is both within the tolerance ± 0.06D, the influence of the aberration due to the increase in the number of measurement areas and measurement indices is small, and 9 × 9. Assuming that a measurement value with higher reliability can be obtained by calculating from the index image, the control unit 40 displays a measurement result based on 9 × 9 index images on the display 2 (S-5). If the READ switch 8 is pressed, the control unit 40 holds the measured value and stores it in the memory 41 (S-6).

  On the other hand, as a result of comparing the measurement values of 7 × 7 and 9 × 9 in step S-4, if the difference in spherical power or column surface power is outside the allowable error range, the measurement value is stabilized. Assuming that the improvement of the property cannot be expected, the control unit 40 uses the calculation result of 7 × 7 index images as the measurement value (S-7).

  In the previous step S-2, if the column surface power is stronger than the predetermined weak power δcD, the inclusion of 9 × 9 index images arranged around the optical axis L1 increases the influence of aberration, and 7 × Since the reliability of accuracy can be ensured even with the measurement results of the seven index images, the calculation results of the 7 × 7 index images are displayed as the measurement results as they are (S-7).

  In the determination of step S-4, the process of performing 7 × 7 operations and 9 × 9 operations is performed a plurality of times (for example, 3 times). good. If the difference between the two is within the tolerance of ± 0.06D and the variation of the measured values measured three times in succession is also ± 0.06D, the measurement value is stabilized and the column surface axis Assuming that the accuracy of the angle can be expected, the measurement result is switched to 9 × 9. If the above condition is not satisfied, the process of using 7 × 7 calculation results as measurement results is continued. This continues until the lens moves greatly (as seen from the change in prism power) or until a new lens is placed on the nosepiece 4. However, even if there is no movement of the lens, it is reconfirmed every few seconds. Anyway.

  The embodiment of the present invention is not limited to the above. You may change suitably the column surface frequency used for determination of step S-2, and the reference | standard used for determination of step S-4. In addition, the method of switching the number of index images to be measured between 7 × 7 and 9 × 9 around the optical axis L1 has been described, but the number is not limited to these numbers. For example, 5 × 5 indexes centered on the hole H5 located on the measurement optical axis L1 are set as normal measurement targets, and the number of measurement indexes is increased by enlarging the region when the column surface frequency is δcD or less. Switch to increase. In addition, an index on the same circumference with a diameter of 2 mm centered on the measurement optical axis L1 is set as a normal measurement object, and the index is switched to an index positioned inside the enlarged diameter when the column surface power is δcD or less. Also good. Moreover, the structure which switches in multiple steps with 5x5 piece, 7x7 piece, and 9x9 piece according to the column surface frequency may be sufficient.

  In the above description, the calculation (second calculation) for enlarging the number of measurement areas and measurement indexes according to the power of the lens LE is used. However, the second calculation is also performed when the lens LE is scratched or dirty. It is effective when applied. That is, the number of index images that are normally detected due to insufficient light quantity or poor index image shape among index images in a small region (7 × 7) in the vicinity of the measurement optical axis L1 because the lens LE is scratched or dirty. Is less than a predetermined number or a fixed ratio (40%, 50%, etc.), the measurement results are likely to vary and the reliability of measurement accuracy is poor. In this case, the control unit 40 displays the measurement result obtained by the second calculation based on 9 × 9 indexes on the display 2. In this case, the stability of the measurement results is improved by increasing the number of index images that are normally detected. In addition, improvement in measurement accuracy can be expected. When the number of normally detected index images satisfies a predetermined number or a fixed ratio, the control unit 40 displays the measurement results obtained by calculating 7 × 7 index images as they are on the display 2.

  Furthermore, by calculating the standard deviation of each measurement value when calculating each measurement value, it is also possible to select only the indicators having the same value. Compared with the index image detection process, the calculation of the optical characteristics can be processed in a short time, so after the detection of the measurement index once, the adopted / non-adopted index is selected and the standard deviation is at the required level. Repeat until improved. Thereby, a stable measurement result can be obtained without extending the measurement time.

  Note that switching from the measurement result using the 7 × 7 index to the measurement result using the 9 × 9 index may not always be suitable for use in a lens manufacturer or the like. It is preferable that the selection switch provided on the display 2 can be used to select whether the measurement result based on the 7 × 7 indicators remains as it is.

  In the second calculation of the above embodiment, the optical characteristics are calculated by expanding (increasing) both the number of measurement regions and the number of measurement indexes, but either one may be used. For example, the normal first calculation targets 7 × 7 49 in a small area near the measurement optical axis L1, and the second calculation expands to 9 × 9 measurement areas, but the calculation processing time is increased. Therefore, the calculation is performed on the same 49 measurement indexes as in the first calculation, such as by setting one interval, instead of targeting all of the enlarged 9 × 9. In addition, as an example of expanding only the number of measurement indexes, in the normal first calculation, in order to shorten the calculation processing time, out of 7 × 7 measurement areas, 25 measurement indexes spaced by one are targeted. Calculate as On the other hand, in the second calculation, calculation is performed for all measurement indexes in the 7 × 7 measurement regions. The second calculation is preferably performed together with the expansion of the number of measurement areas and measurement indices as in the previous embodiment, but only one of them can provide a stable result with respect to the conventional first calculation.

It is a figure explaining the external appearance of the lens meter of embodiment. It is a figure explaining the optical system and control system of an embodiment. It is a figure explaining the index pattern of a measurement index. It is a figure explaining the operation example of embodiment. It is a figure explaining the display screen of alignment.

Explanation of symbols

2 Display 4 Nosepiece 21 Measuring light source 23 Grid plate 24 Image sensor 40 Control unit 41 Memory

Claims (2)

In the lens meter that measures the optical characteristics of the test lens and displays the measurement result on the display means,
An index plate having a large number of measurement indexes arranged in a predetermined pattern around a measurement optical axis, the first measurement index in a first region close to the measurement optical axis and a second region outside the first region A measurement optical system having an index plate having a measurement index including the second measurement index and a light receiving element that receives the measurement light beam that has passed through the index plate and the test lens;
Computation means for computing the optical characteristics of the single focus lens based on the measurement index detected by the light receiving element, and based on the detection result of the first measurement index, the spherical power, column surface power, and column surface axis of the lens An operation for calculating a first optical characteristic including an angle and calculating a second optical characteristic including a spherical power, a column surface power, and a column surface axis angle of the lens based on detection results of the first measurement index and the second measurement index. Means,
When the column surface frequency of the first optical characteristic calculated by the calculation means is equal to or less than a predetermined weak power level that is set to be less affected by aberrations by using the second measurement index, or a column surface frequency And the second optical characteristic as the measurement result of the test lens when both the spherical power and the spherical power are equal to or lower than a predetermined weak power set to be less affected by the aberration caused by using the second measurement index. The first optical characteristic is displayed when the column surface power of the first optical characteristic is higher than the predetermined weak power, or when both the column power and the spherical power are higher than the predetermined weak power. Measurement control means for displaying on the display means as a measurement result of the test lens ;
A lens meter comprising: In the lens meter that measures the optical characteristics of the test lens and displays the measurement result on the display means,
An index plate having a large number of measurement indexes arranged in a predetermined pattern around a measurement optical axis, the first measurement index in a first region close to the measurement optical axis and a second region outside the first region A measurement optical system having an index plate having a measurement index including the second measurement index and a light receiving element that receives the measurement light beam that has passed through the index plate and the test lens;
Computation means for computing the optical characteristics of the single focus lens based on the measurement index detected by the light receiving element, and based on the detection result of the first measurement index, the spherical power, column surface power, and column surface axis of the lens An operation for calculating a first optical characteristic including an angle and calculating a second optical characteristic including a spherical power, a column surface power, and a column surface axis angle of the lens based on detection results of the first measurement index and the second measurement index. Means,
When the column surface frequency of the first optical characteristic calculated by the calculation means is equal to or less than a predetermined weak power level that is set to be less affected by aberrations by using the second measurement index, or a column surface frequency And the spherical power and the spherical surface power of the first optical characteristic when both the spherical power and the spherical power are equal to or lower than a predetermined weak power set to be less affected by the aberration caused by using the second measurement index. And the spherical optical power and the cylindrical surface power of the second optical characteristic are compared, and when both the spherical power and the cylindrical surface power are within a predetermined tolerance, the second optical characteristic is When the column surface power of the first optical characteristic is stronger than the predetermined weak power, or when both the column surface power and the spherical power are stronger than the predetermined weak power, the measurement unit displays the measurement result. The first optical characteristic Measurement control means for displaying on the display unit as a measurement result of the subject lens, and
Lens meter, characterized in that it comprises a.

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