Lens measurement equipment and lens focal plane measurement method under variable temperature conditions

Abstract

The present invention relates to a lens measuring device under variable temperature conditions and a lens focal plane measuring method for measuring the changes of the lens at different temperatures using the lens measuring device. The device comprises a group of light source emitting devices and multiple groups of receiving measuring devices; the light source emitting device comprises a light source, a homogenizing plate and a graticule, and multiple groups of discrimination unit measurement patterns are arranged on the graticule; each group of receiving measuring devices comprises an auxiliary lens and an image sensor, the lens measuring device further comprises a box and a temperature control device, the lens with a holder to be measured can adjust the state where the focal plane of the lens and the bottom plane of the adapter seat overlap, and the present invention can measure the modulation transfer function value (MTF value) corresponding to the lens with a holder to be measured when the image sensor used to detect the imaging quality of the lens with a holder to be measured is offset to different positions under different temperature environments.

Description

Technical Field

[0001] The present invention relates to the field of lens measurement, in particular to a lens measurement device under variable temperature conditions and a lens focal plane measurement method for measuring changes of a lens at different temperatures using the lens measurement device. Background Art

[0002] Online optical lens modulation transfer function tester is widely used in the quality control of optical camera lenses such as security, mobile phones, vehicles, drones, and robot vision due to its high measurement accuracy and fast speed.

[0003] Optical camera lenses used in outdoor security, mobile phones, vehicles, drones, robot vision, etc. require a wide range of ambient temperature, from extremely hot to extremely cold (-45°C to about 70°C). Due to the different materials of lens components, changes in ambient temperature can cause the focal plane position of the optical lens to shift and the image quality to change. A good lens design takes into account the use of different materials between the internal structural parts of the lens and the optical lens and lens adapter, and adjusts the design with the help of simulation software to reduce the degradation of image quality caused by changes in ambient temperature. The high and low temperature performance of the actual finished product is not exactly the same as the results of software simulation, and the high and low temperature optical lens modulation transfer function is still needed to measure the finished product.

[0004] The most commonly used method for online measurement of the modulation transfer function of an optical lens is, for example, Chinese invention patent CN201410372868.4 discloses a method and device for measuring the modulation transfer function of an optical lens using an infinite conjugate optical path. The graticule is moved by a position adjustment mechanism, and during the movement, the content surface of the graticule (i.e., the corresponding surface where the detection image is set) is ensured to coincide with the focal plane of the lens to be measured, while the digital camera receiving the light remains fixed.

[0005] The above device can only evaluate the imaging of optical lenses under normal temperature conditions. Under high and low temperature changes, the position adjustment mechanism will deform, causing the focal plane of the lens to be tested to fluctuate, affecting the accuracy of the measurement of the entire optical system and complicating the measurement operation. Summary of the invention

[0006] The purpose of the present invention is to overcome the above disadvantages and provide a lens measuring device under variable temperature conditions and a lens focal plane measuring method for measuring the changes of the lens under different temperatures using the lens measuring device. On the one hand, it can measure the modulation transfer function value (MTF value) corresponding to the lens under test when the image sensor used to detect the imaging quality of the lens under test is offset to different positions under different temperature environments, so as to draw the defocus change curve of the imaging quality of the lens under test under different temperature environments, and obtain the focal plane offset of the lens under test caused by temperature change according to the comparison of the defocus change curve under different temperatures, so as to facilitate the designer to adjust the design parameters for compensation according to the measurement results of the focal plane offset, so that the imaging quality of the lens under test is basically the same under different temperature environment conditions and normal temperature. On the other hand, it can measure the change of the modulation transfer function of the lens under test caused by the change of temperature when the imaging position of the image sensor used to detect the imaging quality of the lens under test is not moved, so as to judge whether the lens under test is qualified by whether the change is within the allowable standard range. In addition, the lens measuring device can also avoid the influence of temperature deformation of the focusing mechanism in the high and low temperature box on the measurement, thereby improving the measurement accuracy.

[0007] The present invention is realized by the following technical scheme: a lens measuring device under variable temperature conditions, which comprises a group of light source emitting devices and multiple groups of receiving and measuring devices; the light source emitting device comprises a light source, a homogenizing plate and a grating plate which are used to be arranged on the image side of a lens holder to be measured at a detection installation position and arranged in sequence from far to near along the optical axis direction of the lens holder to be measured, and the grating plate is provided with multiple groups of discrimination unit measurement patterns; each group of receiving and measuring devices comprises an auxiliary lens for focusing the light emitted by the light source emitting device and passing through the lens holder to be measured and an image sensor for receiving the focused light and forming an image; the auxiliary lenses of each group of receiving and measuring devices are distributed on the object side of the lens holder to be measured at the detection installation position according to the measurement requirements of the lens holder to be measured, and the angle between the optical axis of each auxiliary lens and the optical axis of the lens holder to be measured at the detection installation position is less than or equal to half of the maximum field angle of the lens holder to be measured, and the optical axis of each auxiliary lens is aligned with the object side principal point of the lens holder to be measured; the characteristics are:

[0008] The lens measuring device also includes a box and a temperature control device for controlling the temperature inside the box. The light source, the homogenizing plate, and the grating plate are installed in the box from bottom to top. The plate surface of the grating plate is arranged horizontally, and the discrimination unit measurement pattern is arranged on the top surface of the grating plate.

[0009] A light-transmitting window for transmitting light is provided on the top wall of the box body corresponding to the light projection position of the light source emitting device, and a detection installation space for accommodating the lens with a holder to be tested is reserved in the box body between the reticle and the light-transmitting window;

[0010] The lens with a holder to be tested can adjust the state that the focal plane of the lens overlaps with the bottom plane of the adapter seat, and during the test, the lens with a holder to be tested is overlapped and pressed on the detection installation position on the top surface of the reticle through the bottom plane of the adapter seat;

[0011] Each group of receiving and measuring devices is distributed above the box body, and the auxiliary lens of each group of receiving and measuring devices is fixed relative to the position of the lens with a holder to be tested located at the detection installation position; each group of receiving and measuring devices also includes a shifting mechanism for driving the image sensor to move on the optical axis of the group of auxiliary lenses and a position measurement sensor for real-time measurement and acquisition of position information of the image sensor on the optical axis of the auxiliary lens relative to the auxiliary lens;

[0012] The lens measurement device also includes an intelligent processor connected to the image sensors and position measurement sensors of each group of receiving and measuring devices respectively; the intelligent processor has the function of selecting an image of a group of discrimination unit patterns captured at the center when the image sensors of each group of receiving and measuring devices are in different positions and calculating the MTF value of the corresponding position based on the image.

[0013] In the lens measuring device under variable temperature conditions of the present invention, the light source, the homogenizing plate and the grating plate are installed in a box, and after pre-adjusting the focal plane of the lens with a holder to be tested to coincide with the bottom surface of its adapter, the lens with a holder to be tested is placed in the box and directly placed on the top surface of the grating plate by its own gravity, so that the focal plane of the lens with a holder to be tested coincides with the top surface of the grating plate. After the detection starts, the position of the grating plate relative to the lens with a holder to be tested remains unchanged, but due to temperature changes, the focal plane position of the lens with a holder to be tested will produce a slight change relative to the top surface of the grating plate, thereby causing a change in the clear imaging position of the lens with a holder to be tested and the auxiliary lens on the image sensor. Under the same temperature environment, the modulation transfer function of different defocus positions can be obtained by moving the image sensor for measurement, and the clearest imaging position at the temperature can be found through each modulation transfer function value and the corresponding position information, and then the focal plane change of the lens with a holder to be tested caused by different temperature changes can be obtained by converting the change of the imaging position at different temperatures. In the present invention, the position adjustment mechanism that drives the movement of the graticule plate is removed, and the lens holder to be tested is pressed on the graticule plate by its own gravity, and the image sensor outside the box is moved to determine the imaging clarity position. In this way, the graticule plate and the lens holder to be tested are combined into an integral fixed structure without introducing other connecting parts in the middle. In this way, the influence of temperature change on optical imaging is only the change of the lens holder to be tested, which can improve the measurement accuracy, thereby adapting to the measurement of the modulation transfer function of the optical lens under different temperature changes.

[0014] Furthermore, the intelligent processor also has the function of generating a defocus change curve corresponding to each group of receiving and measuring devices at each temperature based on the MTF values ​​calculated when the image sensors of each group of receiving and measuring devices are in different positions, the position information corresponding to each MTF value obtained by the position measurement sensor, and the temperatures at which the above measurements are respectively taken.

[0015] The focal plane offset of the lens mount to be tested caused by temperature change can be known through the defocus change curve, so that designers can adjust the design parameters for compensation according to the measurement results of the focal plane offset, so that the imaging quality of the lens mount to be tested is basically consistent under different environmental conditions and at room temperature.

[0016] Furthermore, the lens of the lens holder to be tested is connected to the adapter seat by threaded connection to adjust the relative position of the focal plane of the lens and the bottom plane of the adapter seat. The threaded connection is used to facilitate the adjustment of the position of the lens and the adapter seat.

[0017] Furthermore, the lens measuring device also includes a humidity control device connected to the inside of the box body for controlling the humidity environment inside the box body. The humidity control device can prevent the lens with a holder to be measured and the light-transmitting window from frost and fog, which may affect the operation of the system.

[0018] Furthermore, the light-transmitting window is a quartz plane glass with an incident surface and an exit surface parallel to each other. The use of a quartz plane can reduce the influence on imaging and the deformation due to temperature change is small.

[0019] Furthermore, a side door which can be movably opened and closed and is used for taking in and placing the lens with a holder to be tested is provided on the side wall of the box.

[0020] The present invention also provides a lens focal plane measurement method for measuring changes of a lens at different temperatures based on the lens measurement device under the above-mentioned variable temperature condition, characterized in that it comprises the following steps:

[0021] ① At room temperature, first adjust the position of the lens of the lens holder to be tested relative to the adapter seat, so that the focal plane of the lens of the lens holder to be tested coincides with the bottom plane of the adapter seat, and the bottom plane of the adapter seat is overlapped and pressed on the detection installation position on the top surface of the reticle;

[0022] ② The temperature inside the box is adjusted to each set temperature through the temperature control device, and the following measurements are performed at each set temperature: each group of receiving and measuring devices is driven by the shift mechanism to reciprocate on the optical axis of the same group of auxiliary lenses, and a group of images of discrimination unit patterns captured at the center when the image sensors of each group of receiving and measuring devices are in different positions at the temperature are selected by the intelligent processor, and the MTF value of the corresponding position is calculated based on the image, and the image sensor position information corresponding to each MTF value is recorded in real time by the position measurement sensor.

[0023] Further, at each set temperature, the intelligent processor generates a defocus change curve corresponding to each group of receiving and measuring devices at the corresponding temperature based on the MTF values ​​calculated when the image sensors of each group of receiving and measuring devices are in different positions and the position information corresponding to each MTF value obtained by the position measurement sensor. In specific implementation, the above-mentioned defocus change curve can also be manually drawn as needed.

[0024] Further, according to the defocus change curves generated by each group of receiving and measuring devices at each temperature, the corresponding point values ​​of the maximum MTF values ​​of each group of receiving and measuring devices are obtained;

[0025] By comparing and subtracting the corresponding point value of the maximum MTF value of the defocus change curve obtained by each group of receiving and measuring devices under each abnormal temperature state with the corresponding point value of the maximum MTF value of the defocus change curve obtained under the normal temperature state, the focal plane offset Δ2 of the auxiliary lens of each group of receiving and measuring devices at each abnormal temperature state relative to the normal temperature state is obtained;

[0026] According to the focal plane offset Δ2 of each group of auxiliary lenses of the receiving and measuring device at each abnormal temperature relative to the normal temperature state, the focal plane offset Δ1 of the corresponding points of the lens with holder to be measured and each group of receiving and measuring device at each abnormal temperature relative to the normal temperature state is calculated.

[0027] Preferably, the focal plane offset Δ1 is calculated in the following manner:

[0028] Substitute the focal plane offset Δ2 into the following formula:

[0029] Δ1=Δ2*f1'*f1' / f2' / f2';

[0030] Where f1' is the focal length of the mounted lens to be tested, and f2' is the focal length of the auxiliary lens.

[0031] In addition, the present invention also provides another lens focal plane measurement method for measuring the change of the lens at different temperatures using the lens measurement device, which is characterized by comprising the following steps:

[0032] ① At room temperature, first adjust the position of the lens to be tested relative to the adapter, so that the focal plane of the lens to be tested coincides with the bottom plane of the adapter, and the bottom plane of the adapter overlaps and is pressed on the detection installation position on the top surface of the reticle;

[0033] ② Each group of receiving and measuring devices drives the image sensor of the group through the shift mechanism to move on the optical axis of the auxiliary lens of the same group to the position where the image presented by the image sensor is clearest;

[0034] ③ Keep the position of the image sensor relative to the auxiliary lens unchanged, adjust the internal temperature of the box to each set temperature through the temperature control device, select a group of images of the discrimination unit pattern taken by the center of the image sensor of each group of receiving and measuring devices at each temperature through the intelligent processor, and calculate the MTF value at different temperatures based on the image.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The lens measuring device and lens focal plane measuring method of the present invention can measure the modulation transfer function values ​​(MTF values) corresponding to when the image sensor is offset to different positions under different temperature environments, so as to draw the defocus change curve of the lens imaging quality under different temperature environments according to each MTF value and the corresponding position information, and obtain the focal plane offset of the lens to be tested caused by the temperature change according to the defocus change curve of each temperature, so as to facilitate the designer to adjust the design parameters for compensation according to the measurement result of the focal plane offset, so that the imaging quality of the lens to be tested is basically consistent under different environmental conditions and at room temperature.

[0037] (2) The lens measuring device places the lens holder to be tested directly on the graticule plate through an adapter. During the detection process, the lens holder to be tested does not move relative to the graticule plate, and only the image sensor outside the box moves. Therefore, the influence of temperature deformation of the focusing mechanism in the high and low temperature box on the measurement can be avoided, thereby improving the measurement accuracy.

[0038] (3) The present invention can measure the change in the modulation transfer function of the lens holder to be tested caused by the change in temperature when the imaging position of the image sensor used to detect the imaging quality of the lens holder to be tested is fixed, so as to judge whether the lens holder to be tested is qualified by whether the change is within the allowable standard range. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a light path diagram of Embodiment 1 of the present invention;

[0040] Figure 2 This is a schematic diagram of focal plane change imaging in the present invention;

[0041] Figure 3 It is the defocus change curve measured at different temperatures in the present invention.

[0042] Explanation of reference numerals: 1-box, 11-light-transmitting window, 3-light source emitting device, 31-light source, 32-averaging plate, 33-gradient plate, 4-receiving and measuring device, 41-auxiliary lens, 42-image sensor, a-lens with holder to be tested, a1-lens, a2-adapter seat. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with the accompanying drawings:

[0044] Embodiment 1:

[0045] This embodiment relates to a lens measurement device under variable temperature conditions, such as Figure 1 As shown, it includes a group of light source emitting devices 3 and multiple groups of receiving and measuring devices 4; the light source emitting device 3 includes a light source 31, a homogenizing plate 32 and a dividing plate 33, which are arranged on the image side of the to-be-tested seat lens a located at the detection installation position and arranged in sequence from far to near along the optical axis direction of the to-be-tested seat lens a, and the dividing plate 33 is provided with multiple groups of discrimination unit measurement patterns; each group of receiving and measuring devices 4 includes an auxiliary lens 41 for focusing the light emitted by the light source emitting device 3 and passing through the to-be-tested seat lens a and an image sensor 42 for receiving the focused light and forming an image; the auxiliary lenses 41 of each group of receiving and measuring devices 4 are distributed on the object side of the to-be-tested seat lens a located at the detection installation position according to the measurement requirements of the to-be-tested seat lens a, and the angle between the optical axis of each auxiliary lens 41 and the optical axis of the to-be-tested seat lens a located at the detection installation position is less than or equal to half of the maximum field angle of the to-be-tested seat lens a, and the optical axis of each auxiliary lens 41 is aligned with the object side principal point of the to-be-tested seat lens a; it is characterized in that:

[0046] The lens measuring device further comprises a housing 1 and a temperature control device for controlling the temperature inside the housing 1. The light source 31, the homogenizing plate 32, and the graticule 33 are installed in the housing 1 from bottom to top. The surface of the graticule 33 is arranged horizontally, and the discrimination unit measurement pattern is arranged on the top surface of the graticule 33. The discrimination unit measurement pattern may be a pattern composed of a plurality of groups of different line pairs of black and white thin lines arranged in the meridian and sagittal directions.

[0047] A light-transmitting window 11 for transmitting light is provided on the top wall of the box 1 corresponding to the light projection position of the light source emitting device 3, and a detection installation space for accommodating the lens a with a holder to be tested is reserved in the box 1 between the graticule 33 and the light-transmitting window 11;

[0048] The lens a1 of the lens holder a to be tested can be adjusted relative to the adapter seat a2 until the focal plane of the lens a1 coincides with the bottom plane of the adapter seat a2, and during the test, the lens holder a to be tested is pressed on the detection installation position on the top surface of the reticle 33 by overlapping the bottom plane of the adapter seat a2;

[0049] Each group of receiving and measuring devices 4 is distributed above the box body 1, and the auxiliary lens 41 of each group of receiving and measuring devices 4 is fixed relative to the position of the to-be-tested seat lens a located at the detection installation position; each group of receiving and measuring devices 4 also includes a shifting mechanism for driving the image sensor 42 to move on the optical axis of the group of auxiliary lenses 41 and a position measurement sensor for real-time measurement and acquisition of the position information of the image sensor 42 relative to the auxiliary lens 41 on the optical axis of the auxiliary lens 41;

[0050] The lens measurement device also includes an intelligent processor connected to the image sensors 42 and position measurement sensors of each group of receiving and measuring devices 4 respectively; the intelligent processor has the function of selecting an image of a group of discrimination unit patterns captured at the center when the image sensors 42 of each group of receiving and measuring devices 4 are in different positions and calculating the MTF value of the corresponding position based on the image.

[0051] Since the lens with a holder to be measured is pressed on the grating plate 33 by its own gravity, the position of the grating plate 33 relative to the lens with a holder to be measured remains unchanged during the measurement process, the position adjustment mechanism that drives the grating plate to move is removed, and the image sensor outside the box is moved to determine the imaging clarity position. In this way, the grating plate and the lens with a holder to be measured are combined into an integral fixed structure without introducing other connecting parts such as screws, glue, etc., so that the temperature change has little effect on the infinite conjugate optical system, thereby improving the measurement accuracy, thereby being able to adapt to the measurement of the modulation transfer function of the optical lens under different temperature changes.

[0052] Furthermore, the intelligent processor also has the function of generating a defocus change curve corresponding to each group of receiving and measuring devices 4 at each temperature based on the MTF values ​​calculated when the image sensors of each group of receiving and measuring devices 4 are in different positions, the position information corresponding to each MTF value obtained by the position measurement sensor 42, and the temperatures at which the above measurements are respectively taken.

[0053] The focal plane offset of the lens mount to be tested caused by temperature change can be known through the defocus change curve, so that designers can adjust the design parameters for compensation according to the measurement results of the focal plane offset, so that the imaging quality of the lens mount to be tested is basically consistent under different environmental conditions and at room temperature.

[0054] Furthermore, the lens a1 of the lens holder a to be tested and the adapter seat a2 are connected by threads to adjust the relative position of the focal plane of the lens a1 and the bottom plane of the adapter seat a2. The threaded connection is used to facilitate the adjustment of the position of the lens and the adapter seat.

[0055] Furthermore, the lens measuring device further comprises a humidity control device connected to the interior of the box 1 for controlling the humidity environment inside the box 1. The humidity control device can prevent the lens with a holder to be measured and the light-transmitting window from frost and fogging, which would affect the operation of the system.

[0056] Furthermore, the light-transmitting window 11 is a quartz plane glass with an incident surface and an exit surface parallel to each other. The use of quartz plane glass can reduce the influence on imaging and the deformation due to temperature change is small.

[0057] Furthermore, a side door for taking and placing the lens a with a holder to be tested is provided on the side wall of the box 1. The use of quartz plane glass can reduce the influence on imaging and the deformation due to temperature change is small.

[0058] Embodiment 2:

[0059] This embodiment relates to a lens focal plane measurement method based on the lens measurement device under the above-mentioned variable temperature condition to measure the change of the lens at different temperatures, characterized in that it includes the following steps:

[0060] ① At room temperature, first adjust the position of lens a1 of the lens holder a to be tested relative to the adapter seat a2, so that the focal plane of the lens a1 to be tested coincides with the bottom plane of the adapter seat a2, and the bottom plane of the adapter seat a2 overlaps and is pressed on the detection installation position on the top surface of the reticle 33;

[0061] ② The temperature inside the box 1 is adjusted to each set temperature through the temperature control device, and the following measurements are performed at each set temperature: each group of receiving and measuring devices 4 is driven by the shift mechanism to reciprocate on the optical axis of the same group of auxiliary lenses 41, and a group of images of discrimination unit patterns captured at the center when the image sensors 42 of each group of receiving and measuring devices 4 are in different positions at the temperature are selected by the intelligent processor, and the MTF value of the corresponding position is calculated based on the image, and the image sensor position information corresponding to each MTF value is recorded in real time by the position measurement sensor.

[0062] Further, at each set temperature, the intelligent processor generates a defocus change curve corresponding to each group of receiving and measuring devices 4 at the corresponding temperature based on the MTF values ​​calculated when the image sensors 42 of each group of receiving and measuring devices 4 are in different positions and the position information corresponding to each MTF value obtained by the position measurement sensor.

[0063] Further, the corresponding point value of the maximum MTF value of each group of receiving and measuring devices 4 is obtained according to the defocus change curve generated by each group of receiving and measuring devices 4 at each temperature;

[0064] According to the comparison and difference between the corresponding point value of the maximum MTF value of the defocus change curve obtained by each group of receiving and measuring devices 4 at each abnormal temperature state and the corresponding point value of the maximum MTF value of the defocus change curve obtained at the normal temperature state, the focal plane offset Δ2 of the auxiliary lens 41 of each group of receiving and measuring devices 4 at each abnormal temperature state relative to the normal temperature state is obtained;

[0065] According to the focal plane offset Δ2 of the auxiliary lens 41 of each group of receiving and measuring devices 4 at each abnormal temperature relative to the normal temperature state, the focal plane offset Δ1 of the lens a to be tested with the holder and the corresponding point of each group of receiving and measuring devices 4 at each abnormal temperature relative to the normal temperature state is calculated.

[0066] Preferably, the focal plane offset Δ1 is calculated in the following manner:

[0067] Substitute the focal plane offset Δ2 into the following formula:

[0068] Δ1=Δ2*f1'*f1' / f2' / f2';

[0069] Wherein f1′ is the focal length of the mount lens (a) to be tested, and f2′ is the focal length of the auxiliary lens 41 .

[0070] Embodiment three:

[0071] Another lens focal plane measurement method for measuring changes of a lens at different temperatures using the lens measurement device described in the first embodiment is characterized in that it comprises the following steps:

[0072] ① At room temperature, first adjust the position of lens a1 of the lens holder a to be tested relative to the adapter seat a2, so that the focal plane of lens a1 coincides with the bottom plane of the adapter seat a2, and the bottom plane of the adapter seat a2 overlaps and is pressed on the detection installation position on the top surface of the reticle 33;

[0073] ② Each group of receiving and measuring devices 4 drives the group of image sensors 42 through the shift mechanism to move on the optical axis of the same group of auxiliary lenses 41 to the position where the image presented by the image sensor 42 is the clearest;

[0074] ③ Keep the position of the image sensor 42 relative to the auxiliary lens 41 unchanged, adjust the internal temperature of the box 1 to each set temperature through the temperature control device, select a group of images of the discrimination unit pattern captured by the center of the image sensor 42 of each group of receiving and measuring devices 4 at each temperature through the intelligent processor, and calculate the MTF value at different temperatures based on the image. Whether the change of the MTF value at different temperatures is within the allowable standard range can be used to determine whether the lens with a holder to be tested is qualified.

[0075] like Figure 2 As shown, f1' is the focal length of the lens a with a mount to be tested, f2' is the focal length of the auxiliary lens 41, d is the spacing distance between the two lenses, and the focal plane of the lens is displaced by Δ1 due to temperature change, and the image position of the rear focal plane of the lens a with a mount to be tested is X1'.

[0076] According to Newton's formula: Δ1*X1'=f1'*f1', we get X1'=f1'*f1' / Δ1. For the auxiliary lens 41, the distance between the object and its front focus is:

[0077] X2 = X1’ + d - (f1’ + f2’);

[0078] Δ2 = -f2’ * f2’ / X2 = -f2’ * f2’ / [X1’ + d - (f1’ + f2’)];

[0079] Δ2 = -f2’ * f2’ * Δ1 / {-f1’ * f1’ + [d - (f1’ + f2’)] * Δ1};

[0080] Since [d - (f1’ + f2’)] * Δ1 << f1’ * f1’, it can be obtained that:

[0081] Δ2 = f2’ * f2’ * Δ1 / f1’ * f1’; or

[0082] Δ1 = f1’ * f1’ * Δ2 / f2’ * f2’.

[0083] In this way, it can be achieved that: during the temperature change process, the focal plane change value Δ1 of the lens with a seat to be measured is calculated by measuring the peak displacement Δ2 of the defocus curve.

[0084] As Figure 3 shown, under the conditions of -20°C, 25°C, and 85°C respectively in the figure, while measuring the MTF of a specified spatial frequency (100 lp / mm) at the position of the image sensor 42 relative to the auxiliary measurement lens 41, the above three curves can be obtained. The ordinates of the intersection points of the vertical line Δ2 = 0 and the three curves are different, indicating that when the imaging position of the image sensor 42 remains unchanged, the measured value of the MTF changes due to the temperature change.

[0085] When the MTF of the three curves is the largest, the abscissas are respectively at -105, 0, and 49, indicating that when the temperature is -20°C, the focal plane position is offset by Δ2 = -105 μm compared to the temperature of 25°C, and when the temperature is 85°C, the focal plane position is offset by Δ2 = 49 μm compared to the temperature of 25°C. According to the formula: Δ1 = Δ2 * f1’ * f1’ / f2’ / f2’, the focal plane offset of the lens under test caused by the temperature change can be obtained. The designer can adjust the design parameters for compensation according to the measurement result of the focal plane offset to obtain a better design.

[0086] Although the present invention is illustrated and described by using specific embodiments and their alternative ways, it should be understood that various changes and modifications can be implemented as long as they do not deviate from the spirit of the present invention. Therefore, it should be understood that the present invention is not limited in any sense except by the accompanying claims and their equivalent conditions.

Claims

1. A lens measuring device under variable temperature conditions, comprising a group of light source emitting devices (3) and a plurality of groups of receiving measuring devices (4); the light source emitting device (3) comprises a light source (31), a homogenizing plate (32) and a grating plate (33) arranged on the image side of a lens holder (a) to be measured at a detection installation position and arranged in sequence from far to near along the optical axis direction of the lens holder (a) to be measured, and a plurality of groups of discrimination unit measurement patterns are arranged on the grating plate (33); each group of receiving measuring devices (4) comprises a light source (31), a homogenizing plate (32) and a grating plate (33) for transmitting light emitted by the light source emitting device (3) and passing through the lens holder (a) to be measured. An auxiliary lens (41) for focusing and an image sensor (42) for receiving focused light and forming an image; the auxiliary lenses (41) of each group of receiving and measuring devices (4) are distributed on the object side of the lens holder (a) to be tested located at a detection installation position according to the measurement requirements of the lens holder (a) to be tested, and the angle between the optical axis of each auxiliary lens (41) and the optical axis of the lens holder (a) to be tested located at the detection installation position is less than or equal to half of the maximum field of view of the lens holder (a) to be tested, and the optical axis of each auxiliary lens (41) is aligned with the object side principal point of the lens holder (a) to be tested; characterized in that: The lens measuring device further comprises a box (1) and a temperature control device for controlling the internal temperature of the box (1); the light source (31), the homogenizing plate (32), and the grating plate (33) are installed in the box (1) from bottom to top; the plate surface of the grating plate (33) is arranged horizontally; and the discrimination unit measurement pattern is arranged on the top surface of the grating plate (33); A light-transmitting window (11) for transmitting light is provided on the top wall of the box (1) at a position corresponding to the light projection position of the light source emitting device (3), and a detection installation space for accommodating a lens (a) to be tested with a holder is reserved in the box (1) between the graticule (33) and the light-transmitting window (11); The lens (a1) of the component of the lens holder (a) to be tested can be adjusted relative to the adapter seat (a2) to a state where the focal plane of the lens (a1) overlaps with the bottom plane of the adapter seat (a2), and during testing, the lens holder (a) to be tested is pressed onto the testing installation position on the top surface of the reticle (33) by overlapping the bottom plane of the adapter seat (a2); Each group of receiving and measuring devices (4) is distributed above the box (1), and the position of the auxiliary lens (41) of each group of receiving and measuring devices (4) is fixed relative to the to-be-tested seat lens (a) located at the detection installation position; each group of receiving and measuring devices (4) also includes a shift mechanism for driving the image sensor (42) to move on the optical axis of the group of auxiliary lenses (41) and a position measurement sensor for real-time measurement and acquisition of position information of the image sensor (42) on the optical axis of the auxiliary lens (41) relative to the auxiliary lens (41); The lens measuring device further comprises an intelligent processor connected to the image sensors (42) and the position measuring sensors of each group of receiving and measuring devices (4) respectively; the intelligent processor has the function of selecting an image of a group of discrimination unit patterns captured at the center when the image sensors (42) of each group of receiving and measuring devices (4) are at different positions, and calculating the MTF value of the corresponding position based on the image.

2. The lens measuring device under variable temperature conditions according to claim 1, characterized in that: The intelligent processor also has the function of generating a defocus change curve corresponding to each group of receiving and measuring devices (4) at each temperature based on the MTF values ​​calculated when the image sensors of each group of receiving and measuring devices (4) are at different positions, the position information corresponding to each MTF value obtained by the position measurement sensor, and the temperature at which the above measurements are respectively performed.

3. The lens measuring device under variable temperature conditions according to claim 1, characterized in that: The lens measuring device further comprises a humidity control device connected to the interior of the box (1) and used for controlling the humidity environment inside the box (1).

4. The lens measuring device under variable temperature conditions according to claim 1, characterized in that: The light-transmitting window (11) is a quartz plane glass whose incident surface and exit surface are parallel.

5. The lens measuring device under variable temperature conditions according to claim 1, characterized in that: The side wall of the box body (1) is provided with a side door which can be opened and closed movably and is used for taking in and placing the lens (a) with a holder to be tested.

6. A lens focal plane measurement method for measuring changes of a lens at different temperatures using the lens measurement device according to any one of claims 1 to 5, characterized in that: The following steps are involved: ① First, at room temperature, adjust the position of the lens (a1) relative to the adapter seat (a2) so that the focal plane of the lens (a1) coincides with the bottom plane of the adapter seat (a2), and the bottom plane of the adapter seat (a2) overlaps and is pressed on the detection installation position on the top surface of the reticle (33); ② The temperature inside the box (1) is adjusted to each set temperature by a temperature control device, and the following measurements are performed at each set temperature: each group of receiving and measuring devices (4) is driven by a shift mechanism to reciprocate the image sensors (42) on the optical axis of the same group of auxiliary lenses (41), and an intelligent processor is used to select images of a group of discrimination unit patterns captured at the center of the image sensors (42) of each group of receiving and measuring devices (4) at the temperature when the image sensors (42) are at different positions, and the MTF value of the corresponding position is calculated based on the images, and the position information of the image sensors (42) corresponding to each MTF value is recorded in real time by a position measurement sensor.

7. The lens focal plane measurement method according to claim 6, characterized in that: At each set temperature, the intelligent processor generates a defocus change curve corresponding to each group of receiving and measuring devices (4) at the corresponding temperature based on the MTF values ​​calculated when the image sensors (42) of each group of receiving and measuring devices (4) are at different positions and the position information corresponding to each MTF value obtained by the position measurement sensor.

8. The lens focal plane measurement method according to claim 7, characterized in that: Obtain corresponding point values ​​of the maximum MTF values ​​of each group of receiving and measuring devices (4) according to the defocus change curves generated by each group of receiving and measuring devices (4) at each temperature; By comparing and differentiating the corresponding point value of the maximum MTF value of the defocus change curve obtained by each group of receiving and measuring devices (4) at each abnormal temperature state with the corresponding point value of the maximum MTF value of the defocus change curve obtained at the normal temperature state, a focal plane offset Δ2 of the auxiliary lens (41) of each group of receiving and measuring devices (4) at each abnormal temperature state relative to the normal temperature state is obtained; Calculate the focal plane offset Δ1 of the corresponding points of the lens with holder (a) to be measured and each group of receiving and measuring devices (4) at each abnormal temperature relative to the normal temperature state according to the focal plane offset Δ2 of the auxiliary lens (41) of each group of receiving and measuring devices (4) at each abnormal temperature relative to the normal temperature state; The focal plane offset Δ1 is calculated in the following way: Substitute the focal plane offset Δ2 into the following formula: Δ1 = Δ2 * f1' * f1' / f2' / f2'; Wherein f1' is the focal length of the mount lens (a) to be tested, and f2' is the focal length of the auxiliary lens (41).

9. A lens focal plane measurement method for measuring changes of a lens at different temperatures using the lens measurement device according to any one of claims 1 to 5, characterized in that: The following steps are involved: ① First, at room temperature, adjust the position of the lens (a1) of the lens holder (a) to be tested relative to the adapter seat (a2) so that the focal plane of the lens (a1) coincides with the bottom plane of the adapter seat (a2), and the bottom plane of the adapter seat (a2) overlaps and is pressed on the detection installation position on the top surface of the reticle (33); ② each group of receiving and measuring devices (4) drives the group of image sensors (42) to move on the optical axis of the same group of auxiliary lenses (41) to a position where the image presented by the image sensor (42) is clearest through a shift mechanism; ③ The position of the image sensor (42) relative to the auxiliary lens (41) is kept unchanged, and the internal temperature of the box (1) is adjusted to each set temperature by the temperature control device, and an image of a group of discrimination unit patterns captured by the center of each group of image sensors (42) of the receiving measurement device (4) at each temperature is selected by the intelligent processor, and the MTF value at different temperatures is calculated based on the image.

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