Optical element, lens device, image pickup device, and method for identifying optical element

Abstract

The invention discloses an optical element, a lens device, an image pickup device, and a method for identifying the optical element. An optical element includes a region satisfying the inequality 50 nm < = PV < = 1000 nm, where PV represents a PV value, which is a difference between a maximum value and a minimum value of [Delta] f ([theta]) obtained by removing a primary symmetric component and a secondary symmetric component about an optical axis from f ([theta]), wherein f ([theta]) represents a position of the optical surface in the optical axis direction on a circumference at a first radius of 60% or more and 100% or less of the optical effective diameter with respect to a position [theta] in the rotation direction about the optical axis.

Description

TECHNICAL FIELD

[0001] Aspects of embodiments relate to an optical element, a lens device, an image device, and a method for identifying an optical element. BACKGROUND

[0002] Since an optical element, particularly an aspherical glass lens, has no mark serving as a singular point even when observing the shape of a molded surface of a lens obtained by press molding of a glass material, the optical element cannot be identified, and it is difficult to track or manage a manufacturing history.

[0003] Japanese Patent Publication No. 2006-268015 discloses a marking method in which an optical defect such as a convex portion, a concave portion, a colored portion, a portion having a different refractive index, a bubble embedded in an optical element, or a fine particle embedded in an optical element is used as a management mark in an effective optical surface of an optical element.

[0004] Japanese Patent Publication No. 2006-293115 discloses an identification method in which one optical surface of one side of an optical element is provided with an identification member based on a convex portion or roughness due to transfer of the shape of a mold.

[0005] In Japanese Patent Publication No. 2006-268015, in order to facilitate the above management, the mark needs to have a size (10 pm or more and 200 pm or less) that can be identified by an optical microscope. However, when a mark having such a size is located in an effective optical surface, an incident light beam is scattered and reflected by the mark portion, and imaging performance is deteriorated, and there is a problem that the mark cannot be applied to a product requiring high resolution.

[0006] In Japanese Patent Publication No. 2006-293115, since the identification member transfers irregularities and roughness having a certain position and size formed on a mold, when manufacturing conditions are changed in a batch, it is necessary to prepare and replace a mold corresponding to each condition. SUMMARY

[0007] An optical element includes a region that satisfies the following inequality,

[0008] 50 nm ≤ |PV| ≤ 1000 nm

[0009] where PV represents a PV value, the PV value being a difference between a maximum value and a minimum value of Δf(θ) obtained by removing a 1st order symmetric component and a 2nd order symmetric component around an optical axis from f(θ), where f(θ) represents a position of an optical surface in the optical axis direction on a circumference at a first radius of 60% or more and 100% or less of an optical effective diameter with respect to a position θ in a direction of rotation around the optical axis.

[0010] Features of the present disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments is described by way of example with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1A is a schematic view illustrating a molding method of an optical element according to the present disclosure.

[0012] Figure 1B is a schematic view illustrating a molding method of an optical element according to the present disclosure.

[0013] Figure 1C is a schematic view illustrating a molding method of an optical element according to the present disclosure.

[0014] Figure 1D is a schematic view illustrating a molding method of an optical element according to the present disclosure.

[0015] Figure 2A is a view for describing an evaluation position of a shape of an optical surface of an optical element of the present disclosure.

[0016] Figure 2B is a view for describing an evaluation position of a shape of an optical surface of an optical element according to the present disclosure.

[0017] Figure 2C is a view for describing an evaluation position of a shape of an optical surface of an optical element according to the present disclosure.

[0018] Figure 3 is a graph showing a relationship between a demolding temperature and a PV value on an R1 surface in Example 1 and Example 2.

[0019] Figure 4 is a graph showing a relationship between a demolding temperature and a PV value on an R2 surface in Example 1 and Example 2.

[0020] Figure 5 is an example of an optical system including an optical element of the present disclosure.

[0021] Figure 6 is an example of a lens device including an optical element of the present disclosure.

[0022] Figure 7 is an example of an image pickup device including the optical element of the present disclosure. DETAILED DESCRIPTION

[0023] [Embodiments]

[0024] Hereinafter, embodiments of the present disclosure will be described.

[0025] The present disclosure will be described with reference to embodiments and comparative examples. Note that the drawings described below can be drawn in different scales from actual scales in order to facilitate understanding of the embodiments of the present disclosure. It should also be noted that the present disclosure is not limited to the embodiments described below.

[0026] [Forming of optical element]

[0027] Figures 1A to 1D is a schematic view for describing a forming method of an optical element according to the present disclosure.

[0028] Each of the upper mold member 1 and the lower mold member 2 is a forming member that forms a forming surface of a shape of an optically effective surface of an optical element to be formed with a predetermined surface accuracy by predetermined lapping or polishing, and is made of, for example, a hard alloy. The cylinder mold 3 is configured to position the upper mold member 1 and the lower mold member 2 in a radial direction when the optical element is formed, and has an inner diameter so as to form a radial end surface of the optical element. The surface of the forming surface of the upper mold member 1 and the lower mold member 2 is covered with, for example, a carbon-based film.

[0029] At the time of forming, as shown in Figure 1A , the glass material 5 is put into a mold formed by the lower mold member 2 and the cylinder mold 3, the entire mold is installed in a forming device (not shown), and the entire device shown in Figure 1A is heated to soften the glass material 5. Further, the upper mold member 1 is lowered along the inner surface of the cylinder mold 3 Figure 1B , the glass material 5 is press-formed in a space formed by the upper mold member 1, the lower mold member 2, and the cylinder mold 3, and after the thickness of the glass material 5 becomes the thickness of the optical element 4, the entire device is cooled while the mold is closed. In one embodiment, the temperature is preferably controlled based on the temperature of the glass material 5, but can be controlled based on the temperature according to the temperature of the upper mold member 1, the lower mold member 2, or both.

[0030] Then, after being cooled to a predetermined temperature, the upper mold member 1 is raised Figure 1C), and the upper mold member 1 or the lower mold member 2 is separated (demolded) from the molded article 6 from each other. The temperature at which the upper mold member 1 is raised is referred to as a demolding temperature. The demolding temperature is set by various conditions, and a condition in which the upper mold member 1 is separated from the molded article 6 from each other while the lower mold member 2 is adhered to the molded article 6 from each other is referred to as a basic molding condition. However, when there is a temperature difference between the upper mold member 1 and the lower mold member 2, the upper mold member 1 and the molded article 6 can be adhered to each other.

[0031] After cooling through the demolding temperature, the molded article 6 is further cooled and taken out from the lower mold member 2 at 420°C Figure 1D ), to obtain the optical element 4 as the molded article 6. For the purpose of removing strain, the molded article 6 can be subjected to an annealing process which does not collapse the surface shape. Through the annealing step, the centering step, and the step of forming an antireflection film or a light shielding film, the molded article becomes the optical element.

[0032] [Shape of optical surface of optical element]

[0033] Figure 2A is a side view of the molded article 6 obtained in the present disclosure with respect to the optical axis.

[0034] Among the two optical surfaces of the molded article 6, one optical surface is referred to as an R1 surface (first optical surface), and the other optical surface is referred to as an R2 surface (second optical surface). Here, for convenience, in a case where the molded article 6 is used as the optical element 4 in an optical device such as a lens device, the surface on the incident side is referred to as the R1 surface, and the surface on the emission side is referred to as the R2 surface, but the present disclosure is not limited thereto.

[0035] The shape of the R1 surface is measured by a three-dimensional measuring machine on a circumference centered on the optical axis, for example, counterclockwise, at a first radius between 100% and 60% of an optical effective diameter r1 with the optical axis as the origin Figure 2B ) (a step of acquiring f(θ)). The shape of the optical surface of the optical element is measured in a manner in which deformation toward one side in the direction of the optical axis is positive and deformation toward the other side is negative. The measurement result f(θ) with respect to the position θ in the direction of rotation centered on the optical axis is Fourier-transformed, and an expression (1) close to the position f(θ) of the surface in the direction of the optical axis as the measurement result is obtained.

[0036]

[0037] where Ai represents an amplitude, and represents an initial phase.

[0038] Next, a corrected shape Δf(θ) is obtained from the expression (2) which is a shape obtained by removing, as a 1st order symmetric component (360 degree symmetric component) and a 2nd order symmetric component (180 degree symmetric component)

[0039]

[0040] Here, a PV value is obtained from the obtained corrected shape Δf(θ) based on a difference between a maximum value and a minimum value of Δf(θ) (a step of obtaining a PV value). A positive sign or a negative sign is assigned to the PV value, and a method of assigning the sign will be described later.

[0041] Similarly to the process of obtaining a PV value of the R1 surface which is one optical surface, a measurement process is similarly performed on the R2 surface which is another surface from a measurement start point determined by the R1 surface (). Figure 2C At this time, both the R1 surface and the R2 surface are measured on a circumference at a position of a first radius in a range of 60% or more and 100% of the optical effective diameter. In one embodiment, a measurement result at a position of a radius R at which a PV value is the largest in a range of 60% or more and 100% of the optical effective diameter is used for both the R1 surface and the R2 surface, but the present disclosure is not limited thereto. When measurement is performed in the same counterclockwise direction as the R1 surface, since a phase direction is reversed between the R1 surface and the R2 surface, it is necessary to align the direction with the start point of the measurement result of the R2 surface as a reference. In this case, the measurement result is translated and left-right reversed, and the measurement result is aligned with the start point as a reference.

[0042] Next, a maximum deformation portion of each of the R1 surface and the R2 surface is obtained. Here, in the present specification, the maximum deformation portion of each optical surface is defined as a position at which an absolute value of a difference between the corrected shape Δf(θ) and an average height (an average position in the optical axis direction) of the corrected shape Δf(θ) is the largest. For example, the maximum deformation portion is obtained as follows.

[0043] For example, an average height Ave of the corrected shape Δf(θ) is obtained by the expression (3) (a step of obtaining a first average value, a step of obtaining a second average value).

[0044]

[0045] In each of the R1 surface and the R2 surface, the maximum deformation portion is obtained as a position at which a maximum value is given in an absolute value D of a difference between the corrected shape Δf(θ) (0 ≤ θ ≤ 2π (rad)) and the average height Ave in each of the R1 surface and the R2 surface. ​

[0046] D = | Af(0) - Ave| (4)

[0047] In each optical surface, the magnitude of the position of the maximum deformed portion in the optical axis direction with respect to the average height Ave (positive or negative in the optical axis direction) is acquired. When the corrected shape Af(0) at the maximum deformed portion is larger than the average height Ave (on the object side), the PV value is expressed with a positive sign, and when the corrected shape Af(0) is smaller than the average height Ave (on the image side), the PV value is expressed with a negative sign.

[0048] The optical element of the present disclosure is characterized in that the corrected shape Af(0) in the maximum deformed portion of the R1 surface and the R2 surface is deformed in the same direction in the optical axis direction with respect to the average height Ave. In other words, assuming that one side in the optical axis direction is positive, the sign of Af(0) indicating the maximum difference from the first average value of Af(0) on the R1 surface is the same as the sign of Af(0) indicating the maximum difference from the second average value of Af(0) on the R2 surface. That is, the optical element of the present disclosure is characterized in that the PV values of the R1 surface and the R2 surface have the same sign.

[0049] In the optical element of the present disclosure, the following inequality is satisfied,

[0050] 0 < | 0i - 0i | < 10 (5)

[0051] where 0i (degrees) indicates the position of the maximum deformed portion of the R1 surface in the rotation direction around the optical axis, and 0i (degrees) indicates the position of the maximum deformed portion of the R2 surface in the rotation direction around the optical axis.

[0052] In the cooling process at the time of manufacturing the optical element, during the cooling of the molded article, the upper mold is raised at the demolding temperature (approximately around the glass transition temperature Tg), and the upper mold and the molded article are separated from each other (demolding). At the time of demolding, unevenness occurs on both the surface transferred by the upper mold and the surface transferred by the lower mold. The unevenness in the optical axis direction at a certain radial position of each molding surface around the optical axis tends to increase as the demolding temperature increases.

[0053] In the demolding process during the production of the optical element, a case where the glass molded article is firmly adhered to the upper mold (hereinafter referred to as "upper adhesion") or a case where the glass molded article is firmly adhered to the lower mold (hereinafter referred to as "lower adhesion") occurs. Since the behavior of the molded article (optical surface) at the time of demolding is different between the molded article formed by the upper adhesion and the molded article formed by the lower adhesion in the demolding process, unevenness (deformation) occurs on the optical surface of the optical element which is the molded article, and the direction of the deformation is affected.

[0054] For example, in the case of lower adhesion, at the time of demolding, a part of the surface molded by the lower mold is demolded earlier than other parts of the same surface to weaken the close contact with the mold, and the surface part fixed to the lower mold is pulled more than other surface parts and becomes convex in the direction of the lower mold, and a positional difference occurs in the amount of deformation in the surface in the curing process. This deformation also affects the surface formed by the upper mold, and the corresponding part of the surface formed by the upper mold is pulled toward the lower mold and becomes a concave part.

[0055] For example, in the case of upper adhesion occurring in the process of forming a convex aspherical lens having an approximate curvature radius of the lower mold smaller than that of the upper mold, when the surface formed by the upper mold is an upper surface and the surface formed by the lower mold is a lower surface, a deformed region convex toward the upper mold is formed at a position of the upper surface and the lower surface substantially parallel to the optical axis.

[0056] Similarly, in the case of upper adhesion, at the time of demolding, a part of the surface molded by the upper mold is demolded earlier than other parts of the same surface to weaken the close contact with the mold, and the surface part fixed to the upper mold is pulled more than other surface parts and becomes convex in the direction of the upper mold, and a positional difference occurs in the amount of deformation in the surface in the curing process. This deformation also affects the surface formed by the lower mold, particularly in the direction of pressure removal, and the corresponding part of the surface formed by the lower mold is pulled toward the upper mold and becomes a concave part.

[0057] For example, in the case of upper adhesion occurring in the process of forming a convex aspherical lens (having an approximate curvature radius of the lower mold smaller than that of the upper mold), when the surface formed by the upper mold is an upper surface and the surface formed by the lower mold is a lower surface, a deformed region convex in the direction of the upper mold is formed at a position of the upper surface and the lower surface substantially parallel to the optical axis.

[0058] The optical element of the present disclosure includes a region in which a PV value satisfies the following inequality,

[0059] 50 nm ≤ |PV| ≤ 1000 nm (6)

[0060] where PV represents a PV value that is a difference between a maximum value and a minimum value of a corrected shape Δf(θ) at a radius R of 60% or more and 100% or less of an optical effective diameter around an optical axis. Here, as described above, the corrected shape Δf(θ) is obtained by removing a 1st order symmetric component and a 2nd order symmetric component from a position f(θ) in the optical axis direction at a radius R of 60% or more and 100% or less of an optical effective diameter around an optical axis.

[0061] The optical element of the present disclosure is characterized in that, since the magnitude (absolute value) of the PV value of each optical surface is 1000 nm or less, the effects of scattering and reflection on the deterioration of imaging performance are small.

[0062] Further, in the optical element of the present disclosure, the region satisfying the inequality (6) is a region within a 90-degree range around the optical axis. Further, the optical surfaces of the optical element satisfying the inequality (6) are two surfaces (R1 surface and R2 surface) facing each other in the optical axis direction.

[0063] As described above, the optical element of the present disclosure includes an optical surface having a concave-convex shape depending on the manufacturing conditions within the optical effective diameter. Therefore, by grasping and storing in advance the relationship between the manufacturing conditions such as the demolding temperature and the PV value, the direction of deformation due to upper adhesion or lower adhesion, etc., even when optical elements of batches manufactured under different manufacturing conditions coexist, the optical element can be identified by measuring the lens shape, for example, to identify the manufacturing batch, and the manufacturing history of the lens (the step of identifying the optical element) is tracked and managed. For example, batches having different lens manufacturing conditions such as the demolding temperature can be distinguished, and batches having different demolding histories can be distinguished from the orientation of the concave-convex shape. That is, in the optical element of the present disclosure, the manufacturing conditions can be identified and tracked, and in particular, manufacturing batches having different thermal histories and demolding histories can be identified and tracked.

[0064] [Example 1]

[0065] An optical element 4 according to Example 1 was formed using a glass material A (glass transition temperature Tg = 500°C, refractive index nd = 1.58313) as a glass material 5. The optical element 4 as a molded article 6 had an optical effective diameter of 25.8 mm, and was an aspherical biconcave lens in which the R1 surface (object side surface) was formed by the upper mold and the R2 surface (image side surface) was formed by the lower mold. The following inequalities were satisfied,

[0066] CR1 < CR2

[0067] where CR1 and CR2 represent the approximate curvatures of the R1 surface and the R2 surface of the optical element 4, respectively.

[0068] In the present example, in the molding method of the above-described optical element, the demolding temperature was 505°C (molding condition 1A), and the temperature at which the molded article 6 was taken out from the lower mold member 2 was 420°C. In the optical element 4 of Example 1, the corrected shape Δf(θ) in the maximum deformation portion in both the R1 surface and the R2 surface was in the negative direction (image side) with respect to the average height Ave, and thus in the same direction.

[0069] In addition, the positions θ1 and θ2 of the maximum deformed portions of the R1 surface and the R2 surface in the rotation direction around the optical axis are within 10 degrees of each other. In other words, a straight line connecting the maximum deformed portions of the R1 surface and the R2 surface is substantially parallel to the optical axis.

[0070] The PV value of the R1 surface was -53 nm, the PV value of the R2 surface was -56 nm, and the maximum deformed portions of the R1 surface and the R2 surface were deformed to have convex shapes in the same direction (image side) in the optical axis direction with respect to the average height Ave.

[0071] Similarly, when molding was performed at a demolding temperature of 515°C (molding condition IB) and a demolding temperature of 525°C (molding condition 1C), the deformed directions of the maximum deformed portions of both the R1 surface and the R2 surface were deformed to be convex in the negative direction (image side) in the optical axis direction with respect to the average height Ave. In the optical elements formed under the molding conditions IB and 1C, the positions of the maximum deformed portions of the R1 surface and the R2 surface in the rotation direction around the optical axis were within 5 degrees of each other, and a straight line connecting the maximum deformed portions of the R1 surface and the R2 surface was substantially parallel to the optical axis.

[0072] In the optical element 4 formed under the molding condition IB, the PV value of the R1 surface was -256 nm, and the PV value of the R2 surface was -165 nm. In each of the R1 surface and the R2 surface, the positions of the maximum value and the minimum value of Δf(θ) in which the PV value was measured were within a range of 90 degrees around the optical axis.

[0073] In the optical element formed under the molding condition 1C, the PV value of the R1 surface was -332 nm, and the PV value of the R2 surface was -177 nm. The relationship between the demolding temperature and the PV value in the optical element of this example is shown in Figure 3 , and the relationship between the demolding temperature and the PV value in the optical element of this example is shown in Figure 4 . As shown in Figure 3 and Figure 4 , there is a correlation between the demolding temperature and the PV value, and the higher the demolding temperature, the larger (in absolute value) the PV value is.

[0074] In this example, since the optical element is a biconcave lens having an R2 surface with a larger approximate curvature than an approximate curvature of an R1 surface, and is molded under a condition of underadhesion, the PV value exhibits a negative value under all of the molding conditions IA, IB, and 1C.

[0075] Table 1 summarizes the glass material and the lens shape of the optical element of Example 1. Table 2 summarizes the molding conditions and the surface shape evaluation results of the optical element of Example 1.

[0076] (Manufacturing history tracking)

[0077] Next, a sample S1 is randomly selected from the optical element 4 molded under molding condition 1A, and a sample S2 is randomly selected from the optical element manufactured under molding condition 1B. Since neither sample S1 nor S2 has a clear singularity marker, they cannot be visually distinguished after the two samples are mixed.

[0078] For each of the two samples S1 and S2, the difference in approximate radius of curvature can be visually identified. Therefore, by comparing the two surfaces, the surface with the smaller approximate radius of curvature can be identified as surface R1. When visual inspection is difficult, the approximate curvature or approximate radius of curvature can be obtained using a measuring instrument, and surfaces R1 and R2 can be identified.

[0079] After the R1 and R2 surfaces of each of samples S1 and S2 were specified, the PV values ​​of the R1 and R2 surfaces of the two samples S1 and S2 were obtained using the surface shape measurement method described above. As a result, the PV value of the R1 surface of sample S1 was -341 nm and the PV value of the R2 surface was -182 nm, and the PV value of the R1 surface of sample S2 was -56 nm and the PV value of the R2 surface was -62 nm.

[0080] according to Figure 3 and Figure 4 The relationship between demolding temperature and PV value shown in the figure indicates that sample S1 is from the batch under molding condition 1B, and sample S2 is from the batch under molding condition 1A. Furthermore, since the deformation direction of the maximum deformation portion is negative in both the R1 and R2 surfaces, it can be understood that samples S1 and S2 were formed using under-adhesion molding.

[0081] Furthermore, regarding the impact on MTF (modulation transfer function), the optical element 4 molded under molding conditions 1A, 1B, and 1C according to Example 1 was evaluated using a lens performance evaluation method based on contrast reproducibility. As a result, since the impact on MTF was less than 10%, the degradation of optical imaging performance was minimal.

[0082] The optical element of this embodiment has the following effect: even if no definite odd shape is formed in the optical element, the manufacturing history can be identified and tracked, and in particular, the thermal history can be distinguished and managed.

[0083] [Example 2]

[0084] An optical element 4 according to Example 2 was formed using glass material B (glass transition temperature Tg = 502°C, refractive index nd = 1.58313) as the glass material 5. The optical element 4 as the molded article 6 had an optically effective diameter of 38.8 mm, and was an aspherical concave lens having an Rl surface (object side surface) formed by the upper mold and an R2 surface (image side surface) formed by the lower mold. The following inequalities were satisfied,

[0085] CR1 < CR2

[0086] where CR1 and CR2 represent the approximate curvatures of the Rl surface and the R2 surface of the optical element 4, respectively.

[0087] In the present example, in the molding method of the above-described optical element 4, the demolding temperature was 525°C (molding condition 2A), and the temperature at which the molded article 6 was taken out from the lower mold member 2 was 420°C. The molded article 6 was measured for both the Rl surface and the R2 surface by the above-described surface shape measurement method, and the shape and the PV value of each surface were obtained. In the optical element 4 of Example 2, the corrected shape Af(0) in the maximum deformation portion in both the Rl surface and the R2 surface was in the negative direction (image side) with respect to the average height Ave, and thus in the same direction.

[0088] In addition, the positions θ1 and θ2 in the rotational direction around the optical axis of each of the maximum deformation portion of the Rl surface and the maximum deformation portion of the R2 surface were within 10 degrees of each other. In other words, a straight line connecting the maximum deformation portion of the Rl surface and the maximum deformation portion of the R2 surface was substantially parallel to the optical axis.

[0089] The PV value of the Rl surface was -618 nm, the PV value of the R2 surface was -371 nm, and the maximum deformation portions of both the Rl surface and the R2 surface were deformed to be convex in the same direction (image side) in the optical axis direction with respect to the average height Ave. In each of the Rl surface and the R2 surface, the positions of the maximum and minimum values of Af(0) measured for the PV value were within a range of 90 degrees around the optical axis.

[0090] Similarly, when molding was performed at a demolding temperature of 560°C (molding condition 2B), the deformation direction of the maximum deformation portion was deformed to have a convex shape in the negative direction (image side) in the optical axis direction in both the Rl surface and the R2 surface with respect to the average height Ave. In the optical element formed under molding condition 2B, the positions of the maximum deformation portion of the Rl surface and the maximum deformation portion of the R2 surface in the rotational direction around the optical axis were within 10 degrees, and a straight line connecting the maximum deformation portion of the Rl surface and the maximum deformation portion of the R2 surface was substantially parallel to the optical axis.

[0091] The PV value of the optical element 4 formed under molding condition 1B was -911 nm for the R1 surface and -455 nm for the R2 surface. In each of the R1 surface and the R2 surface, the positions of the maximum and minimum values of Δf(θ) measured for the PV value were within a range of 90 degrees around the optical axis.

[0092] The relationship between the demolding temperature and the PV value in the optical element of this example was shown in Figure 3 for the R1 surface and in Figure 4 for the R2 surface. As shown in Figure 3 and Figure 4 there was a correlation between the demolding temperature and the PV value, and the higher the demolding temperature, the greater the magnitude (absolute value) of the PV value.

[0093] In this example, since the optical element was a biconcave lens having an R2 surface with an approximate curvature larger than that of the R1 surface, and was molded under the condition of lower adhesion, the PV value exhibited a negative value under both molding conditions 2A and 2B.

[0094] Table 1 summarizes the glass material and the lens shape of the optical element according to Example 2. Table 2 summarizes the molding conditions and the surface shape evaluation results of the optical element according to Example 2.

[0095] (Manufacturing history tracking)

[0096] In the same manner as the manufacturing history tracking of Example 1, one sample S3 was arbitrarily sampled from the optical element 4 molded under molding condition 2A, and one sample S4 was arbitrarily sampled from the optical element 4 molded under molding condition 1B. Since both samples S3 and S4 did not have clear singular point marks, they could not be visually identified after mixing the two samples.

[0097] For each of the two samples S3 and S4, the difference in the approximate curvature radius could be visually identified, and therefore, by comparing the two surfaces with each other, the surface having a smaller approximate curvature radius could be identified as the R1 surface. When it was difficult to visually check, the approximate curvature or the approximate curvature radius could be acquired by using a measuring instrument, and the R1 surface and the R2 surface could be identified.

[0098] After the Rl surface and the R2 surface of each of the sample S3 and the sample S4 were specified, the PV values of the Rl surface and the R2 surface of the two samples S3 and S4 were acquired by the surface shape measurement method described above. As a result, the PV value of the sample S3 was -602 nm for the Rl surface and -382 nm for the R2 surface, and the PV value of the sample S4 was -906 nm for the Rl surface and -451 nm for the R2 surface. Note that, in each of the sample S3 and the sample S4, the positions of the maximum and minimum values of Δf(θ) in which the PV value was measured in each of the Rl surface and the R2 surface were located within a 90-degree range around the optical axis.

[0099] According to Figure 3 and Figure 4 the relationship between the demolding temperature and the PV value shown in Table 1, it can be understood that the sample S3 is a batch of the molding condition 2A and the sample S4 is a batch of the molding condition 2B. Further, since the deformation direction of the maximum deformation portion is the negative direction of both the Rl surface and the R2 surface, both the sample S3 and the sample S4 utilize the under-adhesion molding.

[0100] Further, with respect to the influence on the MTF, the optical element 4 molded under the molding conditions 2A and 2B according to Embodiment 2 was evaluated, the MTF being a lens performance evaluation method based on contrast reproducibility. As a result, since the influence on the MTF was less than 10%, it was found that the degradation of the optical imaging performance was small.

[0101] The optical element according to the present embodiment has the following effect: even if a clear singular shape is not formed in the optical element, it is possible to specify and manage the manufacturing history.

[0102] [Embodiment 3]

[0103] A glass material C (glass transition temperature Tg = 691°C, refractive index nd = 1.80400) was used as the glass material 5 to form the optical element 4 according to Embodiment 3. The optical element 4 as the molded article 6 had an optical effective diameter of 40.1 mm, and was an aspherical bi-convex lens in which the R2 surface was formed by the upper mold and the Rl surface was formed by the lower mold. The following inequalities were satisfied,

[0104] CR1 > CR2

[0105] where CR1 and CR2 respectively denote the approximate curvatures of the Rl surface and the R2 surface of the optical element 4.

[0106] In this embodiment, in the molding method of the optical element 4 described above, the demolding temperature is 674°C, and the temperature at which the molded article 6 is removed from the lower mold member 2 is 420°C. When the temperature of the upper mold member 1 is 10°C higher than the temperature of the lower mold member 2 during demolding (molding condition 3A), lower adhesion occurs where the lower mold member 2 and the molded article 6 adhere to each other. On the other hand, when there is no temperature difference between the upper mold member 1 and the lower mold member 2 during demolding (for example, a temperature difference of 3°C or less) (molding condition 3B), upper adhesion occurs where the upper mold member 1 and the molded article 6 adhere to each other.

[0107] The surface shape measurement method described above is used to measure both the R1 and R2 surfaces of the molded article 6, and the shape and PV value of each surface are obtained.

[0108] In the optical element 4 formed under forming condition 3A, the corrected shape Δf(θ) in the largest deformed portion is in the positive direction (object side) relative to the average height Ave on both the R1 and R2 surfaces.

[0109] In the optical element 4 formed under forming condition 3B, the corrected shape Δf(θ) in the largest deformed portion is in the negative direction (image side) relative to the average height Ave on both the R1 and R2 surfaces.

[0110] Furthermore, the positions θ1 and θ2 of the maximum deformation portions of surfaces R1 and R2, respectively, in the direction of rotation about the optical axis are within 10 degrees of each other. In other words, the straight line connecting the maximum deformation portions of surfaces R1 and R2 is substantially parallel to the optical axis.

[0111] The PV value of the optical element 4 formed under molding condition 3A is 80 nm for surface R1 and 60 nm for surface R2. The PV value of the optical element 4 formed under molding condition 3B is -60 nm for surface R1 and -52 nm for surface R2. Note that, in both molding conditions 3A and 3B, the positions of the maximum and minimum values ​​of the measured Δf(θ) for the PV value on each of the R1 and R2 surfaces are within a 90-degree range around the optical axis.

[0112] Table 1 summarizes the glass material and lens shape of the optical element according to Example 3. Table 2 summarizes the molding conditions and surface shape evaluation results of the optical element according to Example 3.

[0113] (Manufacturing history tracking)

[0114] In the same manner as the manufacturing history tracking according to Embodiment 1, one sample S5 is arbitrarily sampled from the batch of optical elements 4 molded under molding condition 3A that causes lower adhesion, and one sample S6 is arbitrarily sampled from the batch of optical elements 4 molded under molding condition 3B that causes upper adhesion. Since both samples S5 and S6 do not have a clear singularity mark, they cannot be visually identified after the two samples are mixed.

[0115] For each of the two samples S5 and S6, the difference in the approximate curvature radius can be visually identified, and therefore, by comparing the two surfaces with each other, the surface having the smaller approximate curvature radius can be identified as the R2 surface. When it is difficult to visually check, the approximate curvature or the approximate curvature radius can be acquired by using a measuring instrument, and the R1 surface and the R2 surface can be distinguished from each other.

[0116] After the R1 surface and the R2 surface of the sample S5 and the sample S6 are specified, the PV values of the R1 surface and the R2 surface of the sample S5 and the sample S6 are obtained by the surface shape measurement method described above. As a result, the PV value of the sample S5 is 82 nm for the R1 surface and 65 nm for the R2 surface, and the PV value of the sample S6 is -62 nm for the R1 surface and -54 nm for the R2 surface.

[0117] Thus, in the sample S5, since the deformation direction of the maximum deformation portion of the R1 surface and the R2 surface is the positive direction, it can be specified that the sample S5 is the batch of molding condition 3A using the lower adhesion condition. Further, in the sample S6, since the deformation direction of the maximum deformation portion of the R1 surface and the R2 surface is the negative direction, it can be specified that the sample S6 is the batch of molding condition 3B using the upper adhesion condition.

[0118] Further, it can be seen that the optical elements 4 formed under molding conditions 3A and 3B according to Embodiment 3 have a PV value of 50 nm or more and 1000 nm or less, and the evaluation of the influence on the MTF exhibits an influence of less than 10%, so that the degradation of the optical imaging performance is small.

[0119] In the optical elements of the present embodiment, even if the optical elements do not have a clear singularity shape, the manufacturing batches having different thermal histories and demolding histories can be distinguished and managed by grasping the relationship between the PV value and the manufacturing condition in advance.

[0120] Table 1 shows the glass material and the lens shape of the optical elements according to Embodiments 1 to 3.

[0121] Table 1

[0122]

[0123] Table 2 shows the molding conditions and surface shape evaluation results of the optical elements according to Embodiments 1 to 3.

[0124] Table 2

[0125]

[0126] [Other Embodiments]

[0127] (Optical system)

[0128] Figure 5 A diagram showing an optical system 50 including the optical element 4 of the present disclosure is shown. The optical system 50 can enjoy the effect of the present disclosure including the optical element 4 in that it is possible to easily manage the manufacturing conditions and track the manufacturing history while suppressing deterioration of the optical imaging performance.

[0129] (Lens device)

[0130] Figure 6 A diagram showing an example of a lens device 100 including an optical system including the optical element 4 of the present disclosure is shown. The lens device 100 can enjoy the effect of the present disclosure including the optical element 4 in that it is possible to easily manage the manufacturing conditions and track the manufacturing history while suppressing deterioration of the optical imaging performance.

[0131] (Image pickup device)

[0132] Figure 7 A diagram is an image pickup device 300 including a lens device 100 including the optical element of the present disclosure. The image pickup device 300 having the effect of the present disclosure can be realized by the lens device 100 including the optical element of the present disclosure and a camera device 200 including an image pickup element 201 that receives (captures) an image formed by the lens device 100.

[0133] While the present disclosure has been described with reference to embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. The scope of the accompanying claims is to be afforded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An optical element comprising a region satisfying the following inequality, 50nm≤|PV|≤1000nm Wherein PV represents the PV value, which is the difference between the maximum and minimum values ​​of Δf(θ) obtained by removing the first and second symmetric components about the optical axis from f(θ), where f(θ) represents the position of the optical surface in the optical axis direction on the circumference at a first radius of more than 60% and less than 100% of the optically effective diameter, relative to the position θ in the rotation direction about the optical axis.

2. The optical element according to claim 1, wherein, The Δf(θ) is obtained by performing a Fourier transform on the f(θ) and removing the first-order symmetric component and the second-order symmetric component from the Fourier-transformed f(θ).

3. The optical element according to claim 2, wherein, The optical surfaces are a first optical surface and a second optical surface that face each other in the direction of the optical axis.

4. The optical element according to claim 3, wherein, When one side of the optical axis direction is defined as positive, the sign of Δf(θ) with the largest difference from the first average value of Δf(θ) on the first optical surface is the same as the sign of Δf(θ) with the largest difference from the second average value of Δf(θ) on the second optical surface.

5. The optical element according to claim 3, wherein, The following inequalities are satisfied: 0≤|θ1-θ2|≤10 Wherein, when one side of the optical axis direction is defined as positive, θ1 represents the position in degrees of the rotational direction about the optical axis where the difference between Δf(θ) and the first average value of Δf(θ) on the first optical surface is the largest, and θ2 represents the position in degrees of the rotational direction about the optical axis where the difference between Δf(θ) and the second average value of Δf(θ) on the second optical surface is the largest.

6. The optical element according to claim 1, wherein, The region is the area within a 90-degree radius around the optical axis.

7. An apparatus comprising an optical element according to any one of claims 1 to 6.

8. A pickup device, the pickup device comprising: The apparatus according to claim 7; And a pickup element configured to receive an image formed by the lens assembly.

9. A method for identifying optical elements, the method comprising: f(θ) is obtained, where f(θ) represents the position of the optical surface of the optical element in the optical axis direction on the circumference of a circle at a position θ in the rotational direction about the optical axis, at a position of a first radius that is more than 60% and less than 100% of the effective optical diameter of the optical element. Δf(θ) is obtained by removing the first-order and second-order symmetric components about the optical axis from f(θ); and The optical element is identified based on the Δf(θ).

10. The method according to claim 9, wherein, The identification includes obtaining a PV value, which is the difference between the maximum and minimum values ​​of Δf(θ).

11. The method according to claim 10, wherein, The identification is based on the PV values ​​relative to the two optical surfaces of the optical element and a pre-stored relationship between the PV values ​​and the demolding temperature during the molding of the optical element.

12. The method according to claim 11, wherein, The identification is based on the approximate relationship between the curvatures of the two optical surfaces of the optical element.

13. The method of claim 9, further comprising: Obtain the first average value of Δf(θ) on the first optical surface of the optical element; as well as Obtain the second average value of Δf(θ) on the second optical surface of the optical element. The identification step identifies the optical element based on the sign of Δf(θ) with the largest difference from the first average value on the first optical surface, and the sign of Δf(θ) with the largest difference from the second average value on the second optical surface, relative to the second average value.

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