JP2007205905A - Method of measuring and manufacturing lens, and optical pick up - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of measuring optical performance highly precisely by detecting and adjusting the position to the light axis highly precisely, in the measurement of the optical performance of an optical pick up, or lens of DSC (Digital Still Camera). <P>SOLUTION: The position of the lens 105 to be tested to the optical axis is highly precisely detected and adjusted by the interference between the light emitted from the laser light source 1 and reflected at the reference surface 4 and the peripheral small surface 107 of the lens, the optical performance of the lens to be detected can be precisely measured by making measuring light which is emitted from the laser light source 100 with the same diameter light flux as the effective diameter by the optical filter 5 perfectly without disturbance light correctly incident on the lens spherical surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an objective lens for forming a light spot on an information recording medium of an optical disc system (CD, DVD, Blu-ray Disc, etc.), a lens mounted in an imaging optical system such as a DSC (digital still camera), etc. The present invention relates to a measuring method, an adjusting method, and an optical pickup for optical characteristics of the lens.

  In order to read information from an optical disk type information storage medium and record information in the information storage medium, an optical system capable of accurately irradiating a target location with light emitted from a light source is required. Among the optical systems, the objective lens, in particular, requires a strict optical characteristic such as a wavefront aberration of about 1/100 of the laser wavelength in the lens itself. Therefore, strict measurement is required also in the characteristic inspection of the objective lens.

  Conventionally, when measuring the optical characteristics of a lens such as an objective lens of an optical pickup, the position of the test lens relative to the optical system of the measuring device is adjusted by measuring light irradiated to the test lens in order to detect the optical characteristics. This is performed by capturing return light reflected by a part of the lens and detecting and adjusting the position of the lens under test based on the position of the return light (see, for example, Patent Document 1). FIG. 8 shows a schematic diagram of a conventional method for measuring optical characteristics of a lens.

  In FIG. 8, a laser generation source 100 that is a light source emits a laser beam 101. The emitted laser light 101 is expanded into substantially parallel light by the beam expander 102, is reflected by the half mirror 103, and enters the lens 105 to be tested supported by the holding table 104. The test lens 105 has a flat edge surface 107 around the lens spherical surface 106. The test lens 105 is inserted into the insertion hole 108 from the lens spherical surface 106 side, and is held by supporting the edge surface 107 with the holding table 104. The holding table 104 is configured such that light enters not only the lens spherical surface 106 but also the edge surface 107. The light incident on the edge surface 107 is reflected by the edge surface 107, passes through the half mirror 103, and then enters the imaging lens 109. The light incident on the imaging lens 109 is imaged on the image sensor 110 such as a CCD camera. The image sensor 110 transmits the received image to a display device 111 such as a monitor. The display device 111 processes the transmitted image and displays the image of the edge surface 107. By detecting the position of the image displayed on the display device 111, it is detected whether or not the test lens 105 is installed in the correct position with respect to the optical axis 112. If the test lens 105 is not in the correct position, the test lens 105 is held. In addition, the holding base 104 having a moving mechanism is adjusted to a correct position with respect to the optical axis 112.

  Here, the light transmitted through the lens spherical surface 106 of the test optical element 105 is incident on the optical characteristic measuring device 113 installed so that the optical axis 112 is the axis center, and the optical characteristic of the test lens 105 is measured. .

As described above, conventionally, the reflected return light of the light incident on the edge surface of the test lens is captured, and the position of the test lens with respect to the optical axis is detected based on the position of the return light.
JP 2000-329648 A (pages 20-21, FIG. 23)

  However, the conventional position detection method has a problem that the measurement accuracy is lowered due to a change in the shape of the return light, disturbance light incident on the edge of the lens, a positional shift of the incident light, and the like.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a measurement method, an adjustment method, and an optical pickup formed by these methods for accurately detecting the position of the lens with respect to the optical axis. .

  In order to achieve the above object, the lens measurement method of the present invention includes a first light reflected by a filter disposed between the light source and the lens, out of the light emitted from the light source, and the first light An interference fringe is formed by interfering with the second light having the same optical axis as the light and passing through the filter and reflected by the outer edge portion of the effective diameter of the lens, and the light intensity of the interference fringe The inclination of the lens with respect to the optical axis of the first light is measured from the distribution. With this configuration, it is possible to accurately detect the position of the lens with respect to the optical axis and accurately measure the optical characteristics of the lens.

  As described above, according to the configuration of the present invention, the position detection accuracy with respect to the optical axis of the test lens can be increased. In addition, it is possible to evaluate without degrading the detection accuracy of the optical characteristics by transmitting only the measurement light within the effective diameter region by the filter on the reference plane. Furthermore, by simultaneously entering light having different wavelengths, lens position detection and optical characteristic evaluation can be performed simultaneously.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic diagram of a lens measurement method and a measurement apparatus according to the first embodiment. In FIG. 1, the description of the same reference numerals as in FIG. 8 is omitted.

  In FIG. 1, reference numeral 1 denotes a laser light source, which has a wavelength different from that of the laser light source 100 for detecting optical characteristics of a lens to be examined. Reference numeral 2 denotes a lens that expands the light emitted from the laser light source 1 into substantially parallel light. 3 is a half mirror, and 4 is a reference plane. Reference numeral 4 a denotes an exit surface that is provided perpendicular to the optical axis and reflects a part of the light from the laser light source 1. Reference numeral 5 denotes an optical filter that transmits light having the wavelength of the laser light source 1 and shields light having the wavelength of the laser light source 100. An imaging lens 6 captures reflected return light from the incident surface 4a and reflected return light from the edge surface 107. Reference numeral 7 denotes an imaging element such as a CCD camera that captures an image formed by the imaging lens 6. Reference numeral 8 denotes an arithmetic unit that processes an image captured by the image sensor 7 and calculates the position of the test lens. Reference numeral 9 denotes a display device such as a monitor for displaying the captured image.

  Hereinafter, a measurement method of the test lens with respect to the optical axis will be described.

  The light emitted from the laser light source 1 is expanded into substantially parallel light by the lens 2. The substantially parallel light passes through the half mirror 103 and enters the half mirror 3. The light incident on the half mirror 3 further passes through the half mirror 3 and enters the reference plane 4. Of the reference plane 4, the exit surface 4 a is installed so as to be perpendicular to the optical axis, so that light incident on the exit surface 4 a is perpendicularly incident. The vertically incident light is partially transmitted by the exit surface 4a and partially reflected. The transmitted light is incident on the optical filter 5 and is transmitted as it is to the light of the wavelength of the laser light source 1. The transmitted light is incident on the test lens 105 supported by the holding table 104.

  FIG. 2 shows a cross-sectional view (a) and a lower view (b) of the holding stand and the insertion hole in the first embodiment. In FIG. 2, the description of the same reference numerals as those in FIGS.

  The test lens 105 has a flat edge surface 107 around the lens spherical surface 106, and the holding table 104 supports the edge surface 107 by inserting the lens spherical surface 106 into the insertion hole 108 and supporting the edge surface 107. Hold. The shape of the holding base 104 and the insertion hole 108 has a diameter larger than the diameter of the lens spherical surface and smaller than the diameter of the edge surface so that light is incident not only on the lens spherical surface 106 but also the edge surface 107 as shown in FIG. The shape of the insertion hole. Here, the angle formed between the edge surface 107 and the optical axis of the lens 105 to be measured is measured in advance. If the angle between the edge surface 107 and the test lens 105 is found to be 90 degrees, the test lens 105 on which the edge surface 107 is formed is used to adjust the optical axis of the test lens 105 to the edge surface. 107. The angle formed between the edge surface 107 and the optical axis of the lens 105 to be measured can be obtained from the design dimensions when the edge surface 107 is created.

  The reflected light on the exit surface 4 a and the reflected light on the edge surface 107 are reflected by the half mirror 3 along the optical path and imaged on the image sensor 7 by the imaging lens 6. At this time, the two reflected lights taken into the image sensor 7 cause interference fringes due to interference. The interference fringes are processed by the arithmetic unit 8 and displayed on the display unit 9. At this time, when the test lens 105 is inclined with respect to the optical axis, that is, the exit surface 4a, a linear interference fringe is generated. At this time, the relation θ between the linear stripe interval “a” and the inclination with respect to the optical axis is expressed by the following equation, where the wavelength of the laser light source 1 is λ.

  If the wavelength of the laser light source 1 is 405 nm and the diameter φ of the lens 105 to be detected is 3 mm, detection of 0.0039 degrees per fringe can be performed. If the inclination of the test lens 105 is adjusted so that the linear stripes appearing here are eliminated, the adjustment can be easily performed with high accuracy. The adjustment accuracy of the inclination of the lens 105 to be tested with respect to the optical axis 112 is about 0.01 degrees in the conventional method, but in this method, the adjustment can be performed at 0.0039 degrees or less. It is possible to adjust with about 2.5 times the accuracy.

  FIG. 3 is a diagram showing driving of the reference plane by the piezo element in the first embodiment. In FIG. 3, the description of the same reference numerals as those in FIGS.

  In FIG. 3, the reference plane 4 is driven in the optical axis direction by the piezo element 10, and the optical path length difference l between the reflected light from the exit surface 4 a and the reflected light from the edge surface 107 is changed from 0 to λ, thereby displaying the display device. The phase of the interference fringes displayed at 9 changes. If each pixel of the interference fringes at this time is (x, y) and the wavefront of the lens 105 is h (x, y), the intensity distribution I of the interference fringes is

It is represented by C0 is a bias component of the interference fringe intensity distribution, and C1 is a component depending on the contrast of the interference fringe. At this time, when the optical path length difference l is changed in N stages and the intensity distribution I (x, y, l) at that time is detected, the wavefront h (x, y) is

It is represented by This wavefront data is Zernike-expanded and each coefficient of the polynomial is calculated, so that not only the inclination with respect to the optical axis but also the surface shape of the edge surface 107 can be evaluated.

  FIG. 4 shows a schematic view of measurement light shielded by the optical filter in the first embodiment. In FIG. 4, the description of the same reference numerals as those in FIGS.

  After adjusting the inclination of the test lens 105 with respect to the optical axis, the laser light source 100 is caused to emit light. The emitted laser beam 101 is magnified to substantially parallel light by the beam expander 102 and then reflected by the half mirror 103. The reflected light further passes through the half mirror 3 and further passes through the reference plane 4. The transmitted light reaches the optical filter 5, but the optical filter 5 is formed in a region outside the circle surrounded by the same radius as the effective diameter of the lens 105 as shown in FIG. Light having an effective diameter passes through the effective diameter, and light outside the effective diameter is blocked by the optical filter 5. The light having the same diameter as the effective diameter that has passed through is accurately incident on the lens spherical surface 106 of the test lens 105. Light that does not include disturbance light that has passed through the test lens 105 is incident on the optical characteristic measuring device 113, and the optical characteristic of the test lens 105 can be accurately measured. Here, the angle formed by the optical axis of the light emitted from the laser light source 100 and the optical filter 5 is measured in advance. The angle formed by the optical axis of the light emitted from the laser light source 100 and the optical filter 5 is the same as the angle formed by the edge surface 107 and the optical axis of the lens 105 to be measured. By making the filter 5 parallel, the measurement of the present embodiment can be performed.

  FIG. 5 shows a flowchart in the first embodiment.

  In FIG. 5, first, in a flow S1, light is emitted from the light source to the lens. Next, in flow S2, the interference fringes are formed by causing the light reflected by the edge of the lens 105 to be inspected and the light reflected by the reference plane 4 to interfere with each other.

  Next, in the flow S3, the formed interference fringes are observed. Here, when a straight stripe appears in the interference fringe, it is determined that the test lens 105 is inclined with respect to the reference plane 4 in the flow A1. Here, when only the inclination of the test lens 105 is adjusted, the tilt of the test lens 105 is measured, and the test lens 105 is adjusted based on the measurement result.

  Next, in flow S4, the relative distance between the test lens 105 and the reference plane 4 is changed. Here, the wavefront data obtained by changing the relative distance is Zernike expanded, and each coefficient is calculated, whereby the surface shape of the edge surface 107 can be evaluated in the flow A2.

  Next, in flow S5, the light transmitted through the effective diameter of the test lens 105 is received. Here, the optical characteristic of the lens 105 to be detected can be detected by the received light that does not include disturbance.

  As described above, according to the first embodiment, the reference plane 4 and the edge surface 107 generated by the light of the laser light source 1 that oscillates a wavelength different from that of the laser light source 100 that measures the optical characteristics of the lens 105 to be measured. By measuring the interference fringes of the reflected light, the position of the test lens 105 can be detected and adjusted with high accuracy, and the surface accuracy of the edge surface 107 can be measured. Furthermore, the optical characteristics of the test lens are measured by measuring light that has the same diameter as the effective diameter and does not contain any disturbance light by an optical filter applied to the area outside the circle surrounded by the same radius as the effective diameter of the test lens. Therefore, it is possible to perform highly accurate evaluation.

  The wavelength of the light of the laser light source 1 having a wavelength different from that of the light of the laser light source 100 is not particularly limited. However, since the light of the laser light source 1 is substantially perpendicularly incident on the reference plane and the test lens, the reflectance is R = | (N−1) / (n + 1) | 2, and the greater the refractive index, the greater the reflectance. Therefore, if the material of the test lens 105 and the reference plane 4 is quartz or the like, the refractive index tends to increase as the wavelength becomes shorter with respect to light having a wavelength in the range of 400 nm to 2000 nm. When it is necessary to increase the frequency, it is preferable to use a laser having a short wavelength for the laser light source 1.

(Embodiment 2)
FIG. 6 shows a sectional view (a) and a lower view (b) of the holding stand and the insertion hole in the second embodiment. In FIG. 6, the description of the same reference numerals as those in FIGS.

  The second embodiment is the same as the first embodiment except that the shape of the holding table 104 is different. As shown in FIG. 6, the diameter of the insertion hole of the holding base 104 is made substantially the same as the diameter of the lens spherical surface of the lens 105 to be tested, and a notch is provided in a part of the outer peripheral portion of the insertion hole. The surface is also irradiated.

  By setting it as such a structure, the area of the edge used for reflection can be made small and a reference plane can be made small. Further, since the diameter of the insertion hole can be made substantially the same as the diameter of the lens spherical surface of the test lens 105, the optical device can be miniaturized.

(Embodiment 3)
FIG. 7 shows a sectional view (a) and a lower view (b) of the holding stand and the insertion hole in the third embodiment. In FIG. 7, the description of the same reference numerals as those in FIGS.

  The third embodiment is the same as the first embodiment except that the shape of the holding table 104 is different. As shown in FIG. 7, the entire surface of the edge surface 107 is irradiated with the light from the laser light source 1 by holding the edge surface 107 so as to support the side surface. The light incident on the edge surface 107 is reflected as it is.

  Such a configuration is useful when measurement is performed using the entire edge surface. Further, the size of the edge of the test lens 105 can be reduced, and the test lens 105 can be downsized.

  According to the present invention, since the optical characteristics of a lens can be measured with high accuracy, it can be applied to the measurement of an objective lens of an optical pickup mounted on an optical disk type information recording apparatus or a lens such as a DSC. .

Schematic diagram of lens measuring method and measuring apparatus in Embodiment 1 (A) sectional view and (b) lower view of holding base and insertion hole in embodiment 1 The figure which shows the drive of the reference plane by the piezoelectric element in Embodiment 1 Schematic of measurement light shielded by the optical filter in the first embodiment Flowchart in the first embodiment (A) sectional view and (b) lower view of holding base and insertion hole in embodiment 2 (A) sectional view and (b) lower view of holding base and insertion hole in the third embodiment Schematic diagram of a method for measuring the optical characteristics of a conventional lens

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Lens 3 Half mirror 4 Reference plane 4a Outgoing surface 5 Optical filter 6 Imaging lens 7 Imaging element 8 Arithmetic unit 9 Display apparatus 10 Piezo element 100 Laser light source 101 Laser light 102 Beam expander 103 Half mirror 104 Holding stand 105 Test lens 106 Lens spherical surface 107 Edge 108 Insert hole 112 Optical axis 113 Optical characteristic measuring device

Claims (10)

Of the light emitted from the light source, the first light reflected by the filter disposed between the light source and the lens, and the same optical axis as the optical axis of the first light and transmitted through the filter Then, interference fringes are formed by interfering with the second light reflected by the outer edge portion of the effective diameter of the lens,
A lens measurement method, comprising: measuring an inclination of the lens with respect to an optical axis of the first light from a light intensity distribution of the interference fringes. The lens measurement method according to claim 1, wherein a wavefront of a lens surface is calculated from a light intensity distribution of interference fringes, and an inclination of the lens with respect to an optical axis of the first light is measured from the calculation result. The second light is light that has passed through the filter transmission part that is centered on the optical axis of the lens and has the same shape as the projection of the lens effective surface,
3. The lens measurement method according to claim 1, wherein the first light is light reflected by a blocking portion of a filter that blocks light having a design wavelength of the lens formed other than the transmission portion. Using light of a first wavelength and light of a second wavelength having different wavelengths,
A first step of measuring the tilt of the lens by the method according to any one of claims 1 to 3 using light of the first wavelength;
And a second step of measuring the inclination of the lens with respect to the optical axis of the light from the light source by using the light of the second wavelength. The lens measurement method according to claim 4, wherein the first wavelength is a wavelength larger than the second wavelength. 6. The lens measuring method according to claim 1, wherein an angle formed by the filter and the first optical axis is measured in advance. The lens measuring method according to any one of claims 1 to 6, wherein an angle formed by a surface of an outer diameter outer edge portion of the lens and an optical axis of the lens is measured in advance. A lens manufacturing method, comprising: measuring a lens using the lens measuring method according to claim 1, adjusting the lens, and fixing the lens to the lens support portion. A light source, a lens, a light receiving element, and a transflective filter installed between the light source and the lens around the optical axis of the lens;
2. The optical pickup according to claim 1, wherein the filter includes a transmission part having the same shape as the projection of the lens effective surface, and a blocking part that blocks the light having the design wavelength of the other lens. The optical pickup according to claim 9, wherein a cross-sectional area of the opening of the lens is larger than an area of the projection of the lens effective surface.

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