Method and system for characterizing an optical lens

Abstract

This invention relates to a method for characterizing an optical lens, the method comprising the steps of: measuring the optical transfer function (OTF) of an optical objective lens for at least one of the following illumination types: green light, blue light, and red light; and, for at least one of the illumination types: comparing the measured OTF with at least one predetermined threshold OTF to determine whether the optical quality of the lens is satisfactory. The invention also relates to a system for implementing this characterization method for characterizing optical objectives, and a method and system for manufacturing optical objectives for implementing this characterization method and system.

Description

[0001] This invention relates to a method for characterizing optical objectives. It also relates to a system for carrying out this method. Furthermore, it relates to a method and system for manufacturing optical objectives using this characterization method and system.

[0002] The field of this invention is generally the field of characterizing optical objectives, particularly optical objectives for imaging, and even more particularly the field of determining the optical quality of said objectives. Background Technology

[0003] An optical objective (or objective lens hereinafter) comprises multiple optical elements, such as lenses, spacers, etc., stacked along a stacking direction within a lens barrel. Once manufactured, the optical objective undergoes performance testing to determine if its image quality is satisfactory. If the objective's quality is unsatisfactory, it is simply scrapped, which reduces manufacturing efficiency and results in time and cost losses.

[0004] Currently, the quality of optical objectives is tested by measuring the modulation transfer function (MTF) of the objective using white light. The measured MTF is compared with a predetermined threshold MTF to determine whether the quality of the objective is considered satisfactory.

[0005] The measured MTF represents all the optical aberrations of the objective lens, namely chromatic aberration, geometric aberration, and third-order and higher-order aberrations (hereinafter referred to as "third-order aberrations" for simplicity). However, the inventors have discovered that some aberrations (e.g., lateral chromatic aberration and geometric aberration) can be effectively corrected by calculation. Therefore, a new method is needed to characterize optical objectives.

[0006] One object of the present invention is to solve at least one of the above-mentioned defects.

[0007] Another object of the present invention is to provide a solution for characterizing optical objectives that allows for more relevant characterization of optical objectives.

[0008] Another objective of this invention is to provide a more efficient method for characterizing optical objectives. Summary of the Invention

[0009] This invention proposes a method for characterizing optical objectives to achieve at least one of the above objectives, the method comprising the following steps:

[0010] - Measure the optical transfer function (OTF) of the optical objective for at least one of the following light sources: green light, blue light, red light; and

[0011] - For at least one of the light sources: the measured OTF is compared with at least one predetermined threshold OTF to determine whether the optical quality of the objective lens is satisfactory.

[0012] The inventors have noted that displacement-type optical aberrations caused by optical objectives can be corrected very effectively through computation (i.e., by digital processing of the acquired image), while diffusion-type aberrations are very difficult to correct, and sometimes even impossible, depending on the scene being imaged. Based on this observation, the present invention proposes to measure the optical quality of optical objectives using an OTF (Optical Time Factor) measured individually for at least one, and particularly each, of the red, green, and blue light components, rather than the MTF (Medium-Tolerance Factor) of the optical objectives as currently measured with white light. In fact, characterizing the optical objectives separately for each color yields a more relevant characterization of contrast quality than under white light. Indeed, under white light, while there may be high contrast for each detected color, moderate contrast can still be obtained, especially when the lateral chromatic aberration becomes comparable to the pattern spacing used to evaluate this contrast ratio (i.e., MTF).

[0013] Therefore, the present invention proposes a new solution for characterizing optical objectives, which is more efficient and capable of better characterizing the optical objectives.

[0014] "Optical aberration" refers to the concept that points in a scene become spots of light, either wide or narrow, at locations that form the image (usually on a plane). Aberrations cause various types of effects: some aberrations have the characteristic of displacing the average position of the spots produced by points in the scene relative to the ideal position where the spots would be produced. These aberrations are called displacement aberrations. Other effects are that the spots have a spatially expanded rather than point-like energy distribution in the image trajectory. These aberrations are called diffusion aberrations.

[0015] Aberrations caused by optical objectives are commonly referred to as chromatic aberration, geometric aberration, and third-order aberration.

[0016] "Third-order aberrations" refer to all aberrations introduced into an image acquired using an optical objective, excluding chromatic aberration and geometric aberrations. These third-order (and higher-order) aberrations include, for example, spherical aberration, coma, astigmatism, field curvature, and distortions (of the spot shape and energy distribution). These third-order aberrations are diffuse.

[0017] Chromatic aberration, caused by the decomposition of light into multiple color bands, refers to the optical aberration that produces different focal positions in space according to wavelength. In the case of lateral chromatic aberration, it consists of a shift in focus along the image trajectory according to wavelength. The result is an image with iridescent edges or colored stripes around objects of uniform color (e.g., white). In the case of axial chromatic aberration, it consists of focusing away from the image trajectory because the focus shifts along an axis perpendicular to the image trajectory (or the axis corresponding to the central ray reaching the image point, which may be tilted relative to the image trajectory). The result is that some colors in the image are blurred. As long as lateral chromatic aberration is quantifiable, i.e., measurable during the design / manufacturing of optical objectives, it can be corrected by digitally processing the image captured by the optical objectives. Lateral chromatic aberration is a displacement aberration. On the other hand, axial chromatic aberration is a diffusion aberration because, for example, if green is focused on the image plane sensor, red may be focused upstream, and the red beam will broaden as it reaches the sensor located outside the focus.

[0018] "Geometric aberration" refers to the deviation between paraxial rays as defined in the Gaussian approximation and their corresponding actual rays. Geometric aberration can also be characterized by the deviation between the paraxial wavefront and the actual wavefront. For example, geometric aberration distorts the shape of the resulting image. For instance, a square might become more like a barrel shape (corners concave) or a pincushion shape (corners convex). Similarly, the straight, vertical edges of a building might become curved and not perpendicular. As long as this aberration is quantifiable—that is, measurable during the design / manufacturing of optical objectives—it can be corrected by digitally processing the captured image. Geometric aberration is a displacement-type aberration.

[0019] "Displacement aberration" or "displacement aberration" refers to lateral chromatic aberration and geometric aberration.

[0020] "Diffusion aberration" or "diffusion aberration" refers to axial chromatic aberration and third-order aberration.

[0021] In the following text, "colored light" refers to red, green, or blue light.

[0022] According to some embodiments, the optical transfer function (OTF) can be the modulation transfer function (MTF).

[0023] According to some embodiments, the optical transfer function (OTF) can be the point spread function (PSF).

[0024] Regardless of whether the OTF is MTF or PSF, the measured OTF and the threshold OTF belong to the same type; either both are MTF or both are PSF.

[0025] According to some embodiments, at least one, particularly each, measured OTF can be represented by OTF values ​​measured at multiple points (e.g., at the center of the objective lens, the edge of the objective lens, etc.). Preferably, the measured OTF can be represented by a value range that includes multiple measured OTF values, each corresponding to a position (x, y) of the image sensor used to perform the measurement, particularly corresponding to a pixel position (x, y).

[0026] Alternatively, a mathematical relationship can be derived from the measured values, which takes the position (x, y) of the image sensor as input and outputs the measured OTF value.

[0027] Of course, at least one measured OTF can be provided in other forms, such as a matrix, vector, etc.

[0028] According to some embodiments, for multiple locations (x, y) or multiple pixel locations (x, y) of an image sensor: for example, at the center, edge, etc. of the sensor, at least one, particularly each threshold OTF, can be represented by a set of values ​​(also called a value range). According to one example, for at least one location (x, y), the value range may include a minimum OTF value to be satisfied. Alternatively or additionally, for at least one location (x, y), the value range may include a pair of values ​​consisting of a minimum OTF value and a maximum OTF value.

[0029] Alternatively, at least one threshold OTF can be provided in the form of at least one mathematical relation that takes the position (x, y) of the image sensor as input and gives the following as output:

[0030] - Threshold OTF value, and especially the minimum OTF value, or

[0031] - Includes a pair of values: minimum OTF value and maximum OTF value.

[0032] Of course, at least one measured threshold OTF can be provided in other forms, such as a matrix, vector, etc.

[0033] At least one threshold OTF can be determined through experimentation or testing. Alternatively or additionally, at least one threshold OTF can be determined during the design or conception of the optical objective. Of course, these examples are by no means limiting, and at least one threshold OTF can be determined in other ways.

[0034] According to some embodiments, the measurement steps may be performed on a single light source to perform OTF measurements.

[0035] In this case, the OTF measured for this single light is compared with a predetermined threshold OTF for said single light. If the measured OTF meets the threshold OTF, the optical objective is considered to have satisfactory optical quality.

[0036] According to some embodiments, the single light used to measure OTF can be green light. In fact, the inventors have discovered that green is more representative of lateral color difference.

[0037] According to some embodiments, the measurement steps can be performed separately for at least two of red, green and blue light, and particularly for each of them.

[0038] In other words, the steps for measuring OTF are performed separately for multiple types of red, green, and blue light.

[0039] In this case, for each type of light being measured, the measured OTF is obtained. For example, if the measurement is performed for red light, the OTF measured for red light is obtained. For example, if the measurement is performed for green light, the OTF measured for green light is obtained. For example, if the measurement is performed for blue light, the OTF measured for blue light is obtained.

[0040] Preferably, the OTF measurement step is performed separately for each of the red, green, and blue light. In this case, the OTF measured for red light, the OTF measured for green light, and the OTF measured for blue light are obtained.

[0041] When the OTF measurement step is performed individually for multiple (or even each) of red, green, and blue light, the comparison step can compare each measured OTF with at least one predetermined threshold OTF.

[0042] In this case, the optical quality of an optical objective can be considered satisfactory if and only if each measured OTF satisfies the threshold OTF with which it is compared.

[0043] According to some embodiments, the same threshold OTF can be used for at least two types of light, and in particular for all types of light.

[0044] According to some embodiments, different threshold OTFs can be used for at least two types of light, and in particular for all types of light.

[0045] in other words:

[0046] - The threshold OTF is associated with red light, and the OTF measured for said red light is compared with the threshold OTF;

[0047] - A threshold OTF is associated with green light, and the OTF measured for said green light is compared with the threshold OTF; and

[0048] - The threshold OTF is associated with blue light, and the OTF measured for said blue light is compared with the threshold OTF.

[0049] According to some embodiments, for at least one light, an OTF measurement can be performed on a measurement plane corresponding to the maximum focus, or on a plane that achieves satisfactory focus.

[0050] Such a measuring plane is preferably perpendicular to the axis of the optical objective.

[0051] For this purpose, the method according to the invention may include the step of identifying the measurement plane by measuring the focus of a plurality of planes and identifying the plane from which maximum or satisfactory focus is obtained. For example, a test pattern may be arranged in front of an objective lens. The relative position of the test pattern with respect to the objective lens may be modified along the axis of the optical objective lens, and the focus value may be monitored to identify the measurement plane.

[0052] When the measurement steps perform OTF measurements for multiple types of light, the same measurement plane can be used for multiple types of light, in particular for all types of light.

[0053] Alternatively, the measurement plane can be identified as follows: The measurement plane is placed at a given distance from the optical objective, and the focus of the camera module formed by the optical objective and the image sensor is adjusted to obtain optimal sharpness at that distance.

[0054] Of course, other embodiments are also possible, and these non-limiting examples are provided for illustrative purposes only.

[0055] According to some embodiments, for at least one type of light, the measurement step may be performed at multiple points to measure the OTF value. For such light, the measured OTF is represented by the values ​​measured at these multiple points, or obtained from these values.

[0056] As mentioned above, for at least one type of light, the measured OTF can be represented by a domain of values, including the measured values ​​and optional other estimates, such as values ​​obtained by interpolation. Alternatively, the measured OTF can be represented by a mathematical relation derived from the measured values.

[0057] According to some embodiments, for at least one type of light, the measurement step can be performed using a test pattern located in front of an optical objective, the test pattern comprising one or more patterns.

[0058] For at least one light source, the test pattern may directly comprise a pattern whose color corresponds to the color of the light (i.e., red, green, or blue). Alternatively, the test pattern may comprise a transparent pattern illuminated by red, green, or blue light.

[0059] If OTF is MTF, then the MTF measurement at a point corresponds to the contrast measured for that point.

[0060] According to one example embodiment, a test pattern is positioned at a selected distance (the so-called scene distance) from the sensor and the objective lens. This distance can also be achieved using optics inserted between the test pattern and the objective lens to alter the apparent distance of the test pattern from the sensor beyond the physical distance between the test pattern and the objective lens. This apparent distance can even be set to infinity to obtain a so-called infinity scene distance. The objective lens can optionally be moved relative to the sensor to select the optimal sharpness of the test pattern for this scene distance. (Optimal sharpness can be obtained in one area of ​​the sensor, one color component, but not necessarily simultaneously in all three color components, or necessarily simultaneously across the entire sensor…). The test pattern alternately includes:

[0061] - So-called dark patterns, which do not allow light to pass through, and

[0062] - The so-called bright pattern corresponds to the color of the radiation.

[0063] Dark patterns should produce a non-radioactive pattern on the sensor because they do not allow any radiation to pass through. Bright patterns should produce a pattern of the same color as the radiation because they allow the radiation to pass through.

[0064] In this configuration, the MTF of a point (x, y) of the sensor is calculated as follows. For a region centered at point (x, y) and comprising multiple alternating patterns, multiple contrast values ​​are calculated based on the values ​​received by pixels in the region, each contrast value corresponding to one alternating pattern in the region. The MTF value of point (x, y) is calculated based on the measured values, for example, by averaging these values.

[0065] If the OTF is a PSF, then the PSF measurement of a point is performed in the usual way.

[0066] According to one example embodiment, a test pattern is arranged in front of the sensor and objective lens, for example, on a plane corresponding to maximum focus. This arrangement can be done directly or using distance-adaptive optics. The test pattern comprises multiple points through which radiation can pass. The remainder of the test pattern is opaque and does not allow any radiation to pass through.

[0067] Each point at position (x, y) is captured on the sensor as a light spot of different width and shape.

[0068] When the light spot is a perfect circle, the PSF value of point (x, y) corresponds to the radius of the light spot captured on the sensor.

[0069] When the light spot has other shapes, the PSF can be calculated as the average radius of the light spot, for example. The average radius can be calculated as follows: First, extract the center of the light spot, for example by determining the centroid of the location where the light spot forms, weighted by the intensity detected at each location. Next, calculate the sum of the detected amplitudes multiplied by the square of the distance to the centroid. Divide this sum by the sum of the detected amplitudes. This gives the square of the average radius of the light spot. Take its square root. This gives the effective average radius of the light spot.

[0070] According to another aspect of the present invention, a system for characterizing optical objectives is provided, the system comprising:

[0071] - At least one device for measuring optical transfer functions; and

[0072] - Computational unit;

[0073] The system is configured to implement the method according to the invention.

[0074] In terms of hardware and / or configuration, the characterization system according to the invention may include any combination of the features disclosed above with reference to the characterization method according to the invention, which will not be mentioned again here for the sake of brevity.

[0075] For at least one of red, green, and blue light, the system according to the invention may include a measurement device specifically designed for measuring OTF only for said light.

[0076] The system according to the invention may include devices for performing OTF measurements for various types of light, including red, green, and blue light.

[0077] At least one measuring device may include a source associated with at least one test pattern.

[0078] The light source can emit red and / or green and / or blue light. In this case, the test pattern can include a transparent pattern or a pattern with the same color as the light. Using a test pattern including a transparent pattern, the OTF of each color can be measured separately by changing the color of the light emitted by the light source; or, for white light emitted by the light source through the transparent pattern, the OTF of each color can even be measured simultaneously by analyzing the image obtained by the sensor (made of red, green, and blue pixels) after filtering for each color.

[0079] Alternatively, the light source can emit white light, and the test pattern can include a pattern of the same color as the light used to measure the OTF. Therefore, by using multiple test patterns, each including a pattern of one of red, green, and blue, the OTF for each color can be measured individually.

[0080] At least one measuring device may include a calculation module for determining the OTF for at least one type of light.

[0081] The computing unit can be configured to compare the measured OTF with at least one threshold OTF for at least one, particularly for each colored light.

[0082] At least one measuring device may include an image sensor for measuring OTF. In this case, the image sensor may be used to measure the OTF of multiple optical objectives.

[0083] Alternatively, at least one measuring device may not include an image sensor. In this case, the optical objective lens has previously been associated with, or in particular assembled with, the image sensor.

[0084] According to another aspect of the present invention, a method for manufacturing an optical objective lens is provided, wherein for at least one optical objective lens, the method comprises the following steps:

[0085] - Manufacturing the optical objective lens,

[0086] - The optical objective lens is characterized by the characterization method according to the invention.

[0087] - Based on the results of the characterization, the optical objective may or may not be retained.

[0088] When measuring OTF for a single colored light (i.e., red, green, or blue light), the optical objective can be retained if the measured OTF for that light meets at least one predetermined threshold OTF.

[0089] When measuring OTF for multiple colored lights (i.e., red light and / or green light and / or blue light), the optical objective can be retained if the measured OTF satisfies at least one predetermined threshold OTF for each type of light being measured.

[0090] According to some embodiments, each manufactured optical objective lens can be characterized.

[0091] Alternatively, only certain manufactured optical objectives may be characterized. For example, within the same batch of optical objectives, only one or a few objectives may be characterized. One or more OTF measurements taken for said one or more objectives in the batch can be used for all objectives in the same batch.

[0092] A batch of optical objectives can correspond to objectives with the same design. Alternatively, a batch of optical objectives can correspond to objectives with the same design and assembled according to the same assembly process.

[0093] According to another aspect of the invention, an apparatus for manufacturing optical objectives is provided, comprising:

[0094] - Optical objective lens production line, and

[0095] - A characterization system according to the invention for characterizing at least one optical objective.

[0096] In terms of hardware and / or configuration, the manufacturing facility according to the invention may include any combination of the features disclosed above with reference to the manufacturing method according to the invention, which will not be mentioned again here for the sake of brevity.

[0097] Specifically, the manufacturing facility is configured to implement the manufacturing method according to the invention.

[0098] According to another aspect of the present invention, a camera module is provided, comprising:

[0099] - An optical objective lens, characterized by the characterization method according to the invention; and

[0100] - An image sensor associated with the optical objective.

[0101] The image sensor can be any type of image sensor associated with an optical objective, such as a CMOS or CCD image sensor, but is not limited to these image sensors.

[0102] According to another aspect of the invention, a user device is also proposed, which includes at least one optical objective lens characterized by the method according to the invention.

[0103] In particular, the user device according to the invention may include at least one camera module according to the invention.

[0104] In particular, the user device can be a user device such as a smartphone, tablet, etc.

[0105] The user device may optionally include a display screen, particularly a touch screen.

[0106] Specifically, the user device may be a virtual reality headset or an augmented reality headset, designed for a user to wear.

[0107] The head-mounted device may optionally include a display screen, particularly a touchscreen.

[0108] In particular, the user device can be a user device such as a camera or camcorder.

[0109] Camera-type user devices may optionally include a display screen, particularly a touch screen.

[0110] In particular, the user device can be a computer-type user device.

[0111] Computer-type user devices may optionally include a display screen, particularly a touch screen.

[0112] The computer-type user device may optionally include a keyboard, or include any other device integrated into or associated with the device.

[0113] In particular, the user device can be a television set.

[0114] Televisions may optionally include a display screen, especially a touch screen.

[0115] In particular, the user device can be a medical imaging device.

[0116] Medical imaging equipment can be, for example, endoscopes, ultrasound machines, etc.

[0117] Of course, the apparatus according to the invention is not limited to the examples disclosed above.

[0118] According to another aspect of the invention, a vehicle is also proposed, which includes at least one optical objective lens characterized by the characterization method according to the invention.

[0119] In particular, the vehicle according to the invention may include at least one camera module according to the invention.

[0120] According to some embodiments, the vehicle may be a land vehicle (e.g., a car), such as a land vehicle with non-autonomous driving, semi-autonomous driving, or fully autonomous driving capabilities.

[0121] According to some embodiments, the vehicle may be an aircraft (e.g., a drone, an airplane, or a helicopter), such as an aircraft with non-autonomous, semi-autonomous, or fully autonomous driving capabilities.

[0122] According to some embodiments, the vehicle can be a waterborne or underwater vehicle (such as a boat or submarine), for example, a waterborne vehicle with non-autonomous, semi-autonomous, or fully autonomous driving capabilities.

[0123] According to another aspect of the present invention, a method for acquiring a scene image is provided, the method comprising the following steps:

[0124] - Acquire images using an optical objective characterized by the method according to the invention, and

[0125] - Perform digital processing on the image to correct it.

[0126] According to some embodiments, digital processing may include the step of correcting lateral chromatic aberration in an image introduced by an optical lens.

[0127] According to some embodiments, digital processing may include the step of correcting geometric aberrations introduced into an image by an optical lens.

[0128] In some embodiments, the optical objective lens can be used for 2D or 3D imaging.

[0129] According to some embodiments, optical objectives can be used for image acquisition to image a scene at a given moment, or to acquire an image stream or video of the scene.

[0130] Description of the Drawings and Detailed Description of the Embodiments

[0131] Other advantages and features will become apparent from a study of the detailed description of the non-limiting embodiments and the accompanying drawings, in which:

[0132] - Figure 1 This is an illustrative depiction of a non-limiting example embodiment of the characterization method according to the present invention;

[0133] - Figure 2 This is an illustrative depiction of another non-limiting example embodiment of the characterization method according to the present invention;

[0134] - Figure 3 This is a schematic depiction of a non-limiting exemplary embodiment of the characterization system according to the present invention;

[0135] - Figure 4 This is a schematic depiction of a non-limiting example embodiment of a method for manufacturing one or more optical objectives according to the present invention;

[0136] - Figure 5 This is a schematic depiction of a non-limiting example embodiment of a facility for manufacturing one or more optical objectives according to the present invention;

[0137] - Figure 6 This is a schematic depiction of a non-limiting example embodiment of a camera module according to the present invention;

[0138] - Figure 7 This is an illustrative depiction of a non-limiting example embodiment of a method for acquiring images according to the present invention;

[0139] - Figures 8a-8c This is an illustrative depiction of a non-limiting example embodiment of a device according to the invention; and

[0140] - Figure 9 This is a schematic depiction of a non-limiting example embodiment of a vehicle according to the present invention.

[0141] It should be clearly understood that the embodiments described below are by no means limiting. In particular, variations of the invention are conceivable that include only selections of features disclosed below independently of other disclosed features, if such selection is sufficient to impart a beneficial technical effect or distinguish the invention from the prior art. Such selections include at least one preferably functional feature that has no structural details, or only a portion of structural details, if that portion alone is sufficient to impart a beneficial technical effect or distinguish the invention from the prior art.

[0142] In particular, all the described variations and embodiments can be combined with each other if there are no technical obstacles to such combinations.

[0143] In the following description of the accompanying drawings and specification, the same reference numerals are used for features common to multiple drawings.

[0144] Figure 1 This is a schematic depiction of a non-limiting example embodiment of a method for characterizing optical objectives according to the present invention.

[0145] Figure 1 Method 100 can be used to characterize optical objectives OO for imaging (i.e., for acquiring images or videos). Such objectives OO can be associated with image sensors to form imaging modules or camera modules and integrated into various devices or vehicles.

[0146] An optical objective lens typically consists of multiple optical elements, such as lenses and spacers. The various elements of an optical objective lens are stacked along a stacking direction, which also corresponds to the axis of the optical objective lens.

[0147] The optical objective lens OO can be used with an image sensor ( Figure 1 (Not shown in the image). In this case, an image sensor is used to characterize the optical objective OO.

[0148] Alternatively, the optical objective lens may not be associated with an image sensor. In this case, the image sensor of the measuring device is used to characterize the optical objective lens OO.

[0149] Figure 1 Method 100 includes step 102 of identifying a measurement plane perpendicular to the optical axis of the optical objective lens OO for measuring the optical transfer function (OTF).

[0150] For this purpose, for example, a test pattern can be arranged in front of the objective lens. The relative position of the test pattern with respect to the objective lens can be modified along the axis of the optical objective lens (optionally by means of adaptive optics), and the focus value can be monitored to identify a measurement plane that provides maximum focus or a satisfactory focus value relative to a predetermined focus threshold.

[0151] Figure 1 Method 100 performs the characterization of the optical objective based on the optical transfer function (OTF) measured separately for each of the green, red, and blue colors.

[0152] exist Figure 1 In the example shown, OTF is MTF. Alternatively, PSF can be used instead of MTF as OTF.

[0153] Method 100 includes step 104, which measures the MTF of the green light measurement optical objective OO.

[0154] exist Figure 1 In a non-limiting example, the green light can be green light with a wavelength of 500 nm to 570 nm, particularly green light with a wavelength of 535 nm.

[0155] MTF can be measured using the techniques described above. Specifically, a test pattern is positioned within the measurement plane identified in step 102. This test pattern is associated with a light source that projects an image of the green pattern onto the objective lens. These images of the patterns pass through the optical objective lens and are captured by an image sensor. For a sensor point, MTF can be measured as the average contrast obtained across multiple patterns, or the average contrast obtained across multiple lines of the pattern surrounding the point.

[0156] Step 104 performs multiple measurements of MTF values ​​for multiple points on the image sensor and provides the measured MTF as represented by the range of measured MTF values, each value corresponding to the sensor position (x, y).

[0157] Then, step 106 compares the measured MTF with at least one threshold MTF.

[0158] As an example, the measured MTF is compared to a threshold MTF that gives the minimum MTF value. If the measured MTF is greater than the threshold MTF, the optical objective OO is retained. Otherwise, the optical objective is discarded.

[0159] As an example, the measured MTF is compared to a first MTF threshold that gives the minimum MTF value and a second MTF threshold that gives the maximum MTF value. If the measured MTF is between the first and second MTF thresholds, the optical objective is retained. Otherwise, the optical objective is discarded.

[0160] The comparison of the measured MTF with a threshold MTF (in particular, each one) can be performed value by value. In other words, for a sensor location (x, y), the MTF value measured for that location (x, y) is compared with the MTF threshold for that location. For each measurement location (x, y), the measured MTF satisfies the MTF threshold if and only if all measured MTF values ​​satisfy the MTF threshold. Finally, the threshold MTF can also depend on (x, y).

[0161] When the MTF measured for green light in step 106 is satisfactory, method 100 includes step 108 of measuring the MTF for red light, which is similar to the MTF measurement for green light in step 104.

[0162] exist Figure 1 In a non-limiting example, the red light can be red light with a wavelength of 570 nm to 730 nm, particularly red light with a wavelength of 650 nm.

[0163] In step 110, the MTF measured for red light is compared with at least one predetermined threshold MTF for red light. If the comparison shows that the MTF measured for red light does not meet at least one threshold MTF, the optical objective OO is discarded. Otherwise, the optical objective OO is retained, and method 200 continues.

[0164] When the MTF measured for red light in step 110 is satisfactory, method 100 includes step 112, which measures the MTF for blue light, similar to the MTF measurement for green light in step 104.

[0165] exist Figure 1 In a non-limiting example, the blue light can be blue light with a wavelength of 400 nm to 500 nm, particularly blue light with a wavelength of 450 nm.

[0166] In step 114, the MTF measured for blue light is compared with at least one predetermined threshold MTF for blue light. If the comparison shows that the MTF measured for blue light does not meet at least one threshold MTF, the optical objective OO is discarded. Otherwise, the optical objective is retained.

[0167] exist Figure 1 In the example shown, the MTF measured for one color is compared with at least one threshold MTF before measuring the MTF for another color. This avoids the need to measure the MTF for the other color if the MTF measured for the current color is unsatisfactory.

[0168] According to an alternative not shown, steps 104, 108, and 112 may be performed before performing comparison steps 106, 110, and 114.

[0169] Figure 2 This is a schematic depiction of another non-limiting example embodiment of the method for characterizing optical objectives according to the present invention.

[0170] Figure 2 Method 200 can be used to characterize optical objectives OO for imaging (i.e., for acquiring images or videos). Such objectives OO can be associated with image sensors to form imaging modules or camera modules and integrated into various devices or vehicles.

[0171] The optical objective lens OO can be used with an image sensor ( Figure 1 (Not shown in the image). In this case, the image sensor is used to characterize the optical objective OO.

[0172] Alternatively, the optical objective lens may not be associated with an image sensor. In this case, the image sensor of the measuring device is used to characterize the optical objective lens OO.

[0173] and Figure 1 The methods for characterizing objectives based on each of the green, red, and blue colors are 100 different. Figure 2 Method 200 characterizes the optical objective OO based on OTF measured separately for a single color.

[0174] exist Figure 2 In the example shown, the measured OTF is MTF. Alternatively, PSF can be used instead of MTF as OTF.

[0175] exist Figure 2 In the example shown, the single color used to characterize the optical objective is green. Alternatively, red or blue could, of course, be used.

[0176] Method 200 includes references Figure 1 The method 100 discloses steps 102-106, but does not include step 110 and subsequent steps of the method 100.

[0177] If the MTF measured for green light in step 108 is satisfactory, retain the optical objective lens OO. Otherwise, discard the optical objective lens OO.

[0178] Then, method 200 terminates.

[0179] According to another alternative not shown in the accompanying drawings, the optical objective OO can be characterized based on two colors selected from green, red, and blue.

[0180] Figure 3 This is a schematic depiction of a non-limiting example embodiment of a system for characterizing optical objectives according to the present invention.

[0181] Figure 3 The system 300 can be used to implement the method according to the invention, particularly any one of method 100 or 200.

[0182] System 300 includes a first measuring device 302 that uses green light to measure OTF. Measuring device 302 may include a green light source that illuminates a test pattern having a transparent pattern, such that an optical objective receives the green pattern. Alternatively, measuring device 302 may include a white light source that illuminates the test pattern having a green pattern, such that an optical objective receives the green pattern.

[0183] System 300 includes a second measuring device 304 that uses red light to measure OTF. Measuring device 304 may include a red light source that illuminates a test pattern having a transparent pattern, such that an optical objective receives the red pattern. Alternatively, measuring device 304 may include a white light source that illuminates a test pattern having a red pattern, such that an optical objective receives the red pattern.

[0184] System 300 includes a third measuring device 306 that uses blue light to measure OTF. Measuring device 306 may include a blue light source that illuminates a test pattern having a transparent pattern, such that an optical objective receives the blue pattern. Alternatively, measuring device 306 may include a white light source that illuminates the test pattern having a blue pattern, such that an optical objective receives the blue pattern.

[0185] It should be noted that OTF can be either MTF or PSF.

[0186] System 300 also includes computing unit 308.

[0187] The calculation unit 308 includes a calculation module 310. This calculation module can be configured or programmed to perform a comparison, for a given color, of the OTF measured for that color with one or more predetermined threshold OTFs.

[0188] The calculation module 310 may optionally be configured or programmed to calculate, for a given color, the measured OTF value based on measurements performed by any of the measuring devices 302-306. Alternatively, this calculation operation may be integrated into at least one, and particularly each, of the measuring devices 302-306.

[0189] The calculation unit 308 may optionally include a control module 312 for controlling at least one, and in particular each, of the measuring devices 302-306 to perform OTF measurements.

[0190] At least one of modules 310-312 may be a hardware unit, such as a processor, chip, computer, server, etc. Alternatively, at least one of modules 310-312 may be a software unit, such as a computer application or computer program. Alternatively, at least one of features 310-312 may be a combination of at least one hardware unit and at least one software unit.

[0191] At least one of modules 310-312 can be independent of the other modules 308-312. Two modules 310-312 can be integrated into the same module.

[0192] According to an alternative not shown, at least two, and in particular all, of the measuring devices 302-306 can be integrated into a single measuring device.

[0193] In this scenario, the single measuring device may include a light source configured to emit, for example, green, red, and blue light sequentially. In this scenario, the single measuring device may include or use:

[0194] - It has a test pattern with a transparent pattern that can be used to measure OTF for each color, or

[0195] - The test pattern used in sequence is the one with a green pattern, the one with a red pattern, and the one with a blue pattern.

[0196] Alternatively, the single measuring device may include a white light source. In this case, the device is capable of using a test pattern with a green pattern, a test pattern with a red pattern, and a test pattern with a blue pattern used sequentially.

[0197] Figure 4 This is a schematic depiction of a non-limiting example embodiment of a method for manufacturing an optical objective lens according to the present invention.

[0198] Figure 4 Method 400 can be used to manufacture optical objectives for imaging (i.e., for acquiring images or videos).

[0199] Method 400 includes step 402 of manufacturing an optical objective. The manufacturing of the optical objective is carried out in a conventional and well-known manner, which will not be disclosed in detail herein.

[0200] Method 400 includes step 404, which involves characterizing one or each of the optical objectives manufactured in step 402 using the method according to the invention (particularly using method 100 or method 200).

[0201] Method 400 further includes the step of retaining or not retaining the optical objective based on its performance. If the performance of the optical objective is satisfactory, the optical objective is retained. Otherwise, the optical objective is not retained and is discarded.

[0202] In method 400, each manufactured objective lens can be characterized.

[0203] Alternatively, only certain manufactured objectives can be characterized.

[0204] For example, when the first batch of objectives from the same production batch is characterized and shows satisfactory optical quality, other objectives from the same manufacturing batch may not be characterized.

[0205] According to another example, when the first batch of objectives from the pairing process is characterized and shows satisfactory optical quality, other objectives obtained using the same pairing process may not be characterized.

[0206] Figure 5 This is a schematic depiction of a non-limiting example embodiment of a facility for manufacturing optical objectives according to the present invention.

[0207] Figure 5 The manufacturing facility 500 is capable of manufacturing optical objectives for imaging (i.e., for acquiring images or videos).

[0208] Facility 500 includes optical objective lens production line 502. Production line 502 is a known conventional optical objective lens production line, and therefore will not be described in detail here.

[0209] Facility 500 also includes system 504, which can be Figure 3 System 300 is used to characterize one or each optical objective lens manufactured by production line 502. If the performance of the optical objective lens is satisfactory, it is retained. Otherwise, the optical objective lens is not retained and is discarded.

[0210] Figure 6 This is a schematic depiction of a non-limiting example embodiment of a camera module according to the present invention.

[0211] Figure 6 The camera module 600 includes the features characterized according to the invention (particularly by means of...). Figure 1 Method 100 or Figure 2 The optical objective 602 is characterized by method 200. The optical objective 602 can be... Figure 1-5 The optical objective lens OO is shown in the figure.

[0212] exist Figure 6In the non-limiting example shown, the optical objective 602 includes four lenses 604-610 stacked in the lens barrel 612 along a stacking direction 614, which also corresponds to the axis 614 of the optical lens 602.

[0213] The camera module 600 also includes an image sensor 616 associated with the optical objective lens 602. The image sensor 616 can be any type of image sensor, such as a CCD or CMOS sensor.

[0214] Of course, the camera module 600 can be included Figure 4 Other components not shown, such as devices for modifying the imaging angle or devices for modifying the sharpness distance of the imaging area.

[0215] The camera module 600 may optionally include a module 618 for digitally processing the data captured by the image sensor 616. Such a digital processing module 618 can, for example, be configured to correct the image captured by the image sensor 616 to, for example, correct at least some of the optical aberrations caused by the optical objective lens 602. The module 618 may, for example, integrate one or more predetermined aberration correction functions.

[0216] The processing module 618 can be a standalone module. Alternatively, the processing module 618 can be integrated into another module or another application, such as a photo application for image acquisition.

[0217] Figure 7 This is a schematic depiction of a non-limiting example embodiment of a method for acquiring images according to the present invention.

[0218] Method 700 includes using an optical objective lens characterized by the present invention or using a camera module according to the present invention (especially...). Figure 6 Camera module 600 or Figure 1-5 Step 702: Acquiring an image using the objective lens OO.

[0219] Method 700 further includes a step 704 of digitally processing the acquired image. Such digital processing can correct the acquired image to, for example, at least partially correct lateral chromatic aberration and / or geometric aberration caused by the optical objective used to acquire the image. This aberration correction can be performed, for example, using at least one predetermined aberration correction function.

[0220] Figure 8a This is a schematic depiction of a non-limiting example embodiment of the device according to the invention.

[0221] Figure 8a The device 810 includes at least one imaging module according to the invention, particularly Figure 6The imaging module 600.

[0222] exist Figure 8a In the example shown, device 810 is a smartphone or tablet.

[0223] Optionally, the device 810 may also include a display screen 812 equipped with, for example, a capacitive touch-sensitive surface 814.

[0224] The device 810 may also include an imaging application 816, such as a photo application and / or a video application, installed in and executed by the device 810. The application 816 may, for example, be integrated with the processing module 618 of the imaging module 600. Alternatively, the processing module 618 may be independent of the application 816.

[0225] Figure 8b This is a schematic depiction of another non-limiting example embodiment of the device according to the invention.

[0226] Figure 8b The device 820 includes at least one imaging module according to the invention, particularly Figure 6 The imaging module 600.

[0227] exist Figure 8b In the example shown, device 820 is a virtual reality headset (VR) or an augmented reality headset (AR).

[0228] Optionally, the head-mounted device 820 may also include a display screen 822. Optionally, the head-mounted device 820 may also include a sensor (not shown) for detecting the position of a user's single eye or both eyes on the display screen 822.

[0229] The head-mounted device 820 may also include an imaging application (not shown), such as a photo application and / or a video application, installed in and executed thereon. This imaging application may, for example, be integrated with the processing module 618 of the imaging module 600. Alternatively, the processing module 618 may be independent of the imaging application of the head-mounted device 820.

[0230] Figure 8c This is a schematic depiction of another non-limiting example embodiment of the device according to the invention.

[0231] Figure 8c The device 830 includes at least one imaging module according to the invention, particularly Figure 6 The imaging module 600.

[0232] exist Figure 8c In the example shown, device 830 is a medical imaging device, such as an endoscope, ultrasound equipment, etc.

[0233] Optionally, the medical imaging device 830 may also include a display screen 832.

[0234] Alternatively, the medical imaging device 830 may also be equipped with, for example, a capacitive sensing surface 834.

[0235] Optionally, the medical imaging device 830 may also include a distal objective lens 836 for collecting light, which may or may not be part of the imaging module 600.

[0236] The medical imaging apparatus 830 may also include an imaging application (not shown), such as a photo application and / or a video application, mounted on and executed thereon. This imaging application may, for example, be integrated with the processing module 618 of the imaging module. Alternatively, the processing module 618 may be independent of the imaging application of the apparatus 830.

[0237] Figure 9 This is a schematic depiction of a non-limiting example embodiment of a vehicle according to the present invention.

[0238] Figure 9 The vehicle 900 includes at least one imaging module according to the invention, particularly Figure 6 The imaging module 600, for example, is integrated into the camera 902.

[0239] In vehicle 900, camera 902 may be positioned, for example, behind the windshield, at the top of the windshield, or above the front windshield. Of course, this positioning is given as a non-limiting example, and camera 902 may be positioned in other locations.

[0240] exist Figure 9 In the example shown, vehicle 900 is a land vehicle, particularly an automobile. Vehicle 900 may also include a display screen 904 arranged in the passenger compartment of vehicle 900, which is equipped with a touch-sensitive surface 906, for example, capacitive.

[0241] The vehicle 900 may also include an imaging application 908, such as a photo application and / or a video application. The imaging application 908 may, for example, be integrated with the processing module 618 of the imaging module 600. Alternatively, the processing module 618 may be independent of the imaging application 908.

[0242] Of course, this invention is not limited to land vehicles. Vehicles according to the invention can be aircraft, such as unmanned aerial vehicles, airplanes, helicopters, etc. Vehicles according to the invention can also be waterborne or underwater vehicles, such as maritime unmanned aerial vehicles, ships, submarines, etc.

[0243] This invention is not limited to the examples of devices and vehicles given with reference to the accompanying drawings. This invention can be used in all types of devices and vehicles, including those with camera modules.

[0244] Of course, the present invention is not limited to the examples disclosed above.

Claims

1. A method (100; 200) for characterizing an optical objective (OO), said method (100; 200) comprising the following steps: - Measure the optical transfer function (OTF) of the optical objective (OO) for at least one of the following light sources (104; 108; 112): green light, blue light, red light; and - For at least one of the light sources: the measured OTF is compared with at least one predetermined threshold OTF (106; 110; 114) to determine whether the optical quality of the objective lens is satisfactory.

2. The method (100; 200) according to the preceding claim, characterized in that, The optical transfer function is a modulation transfer function (MTF).

3. The method (100; 200) according to claim 1, characterized in that, The optical transfer function is the point spread function (PSF).

4. The method (200) according to the preceding claim, characterized in that, Measurement step (104) performs OTF measurement only for a single light.

5. The method according to the preceding claim, characterized in that, The light is green light.

6. The method (100) according to any one of claims 1 to 3, characterized in that, Measurement steps (104, 108, 112) involve performing OTF measurements for at least two of the red, green, and blue light, and in particular for each of them.

7. The method (100) according to the preceding claim, characterized in that, The comparison steps (106; 110; 114) compare the measured OTF with at least one predetermined threshold OTF for each type of light for which the OTF has been measured.

8. The method (100; 200) according to any one of the preceding claims, characterized in that, For at least one light, an OTF measurement is performed on the measurement plane corresponding to the maximum focus or the plane that satisfies the focus (104; 108; 112).

9. The method (100; 200) according to any one of the preceding claims, characterized in that, For at least one light, measurement steps (104; 108; 112) perform OTF value measurements at multiple points.

10. The method (100; 200) according to any one of the preceding claims, characterized in that, For at least one type of light, a measurement step (104; 108; 112) is performed using a test pattern located in front of the optical objective (OO), the test pattern comprising one or more patterns.

11. A system (300) for characterizing an optical objective (OO), the system comprising: - At least one device for measuring optical transfer function (302-306). as well as - Calculation unit (308); The system is configured to implement the steps of the method according to any one of claims 1 to 10.

12. A method (400) for manufacturing an optical objective lens, the method comprising the following steps for at least one optical objective lens: - Manufacture the optical objective (OO). - Characterize the optical objective (OO) using the method according to any one of claims 1 to 10. - Based on the results of the characterization, retain or not retain the optical objective (OO).

13. An apparatus for manufacturing an optical objective lens, comprising: - Optical objective lens production line, and - A characterization system for characterizing at least one optical objective lens according to claim 12.

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