JP6430078B1 - MTF measuring apparatus and MTF measuring method - Google Patents

Abstract

An object of this invention is to provide the MTF measuring apparatus and MTF measuring method which can measure MTF of an optical device with respect to the light of all wavelengths. An MTF measuring apparatus (100) for measuring MTF of an optical device includes a test chart (105) on which a test pattern having a light non-transmissive area and a light transmissive area is formed, and light for irradiating the test chart with light. Using the output signal of the light source (101), the wavelength selection unit (102) for selecting the wavelength of light emitted from the light source, and the converter (solid-state imaging device 10) that photoelectrically converts the light emitted from the test chart And an arithmetic unit (107) for calculating the MTF. The wavelength selection unit (102) splits light emitted from the light source (101) to extract light of a specific wavelength, and incident light incident on the spectral element (diffraction grating 108). And an adjustment mechanism (rotation mechanism 109) for changing the angle.

Description

  The present invention relates to an MTF measuring apparatus and an MTF measuring method for measuring MTF of an optical device.

  Conventionally, OTF (Optical Transfer Function) is known as an index for evaluating the performance of an optical device such as a solid-state imaging device or a lens. MTF (Modulation Transfer Function), which is a real part of OTF, quantifies the sharpness of an image as a spatial frequency characteristic. The larger the MTF value, the higher the performance of the optical device.

  As an apparatus for measuring this MTF, Patent Document 1 discloses an MTF measuring apparatus including a light source and a test chart on which a test pattern is formed. The light source, the test chart, and the imaging device are arranged in this order on the optical path. A chart image generated by light emitted from the light source and passed through the test pattern is taken by the imaging device, and the MTF of the imaging device is calculated based on the output.

  Patent Document 2 discloses an MTF measuring device including a light source, a test chart on which a test pattern is formed, and a light receiving device. Two optical filters having different wavelength selectivity are arranged between the light source and the test chart, and a rod lens is arranged between the test chart and the light receiving device on the optical path. The two optical filters are switched according to a predetermined control program. The MTF is calculated based on the intensity of light emitted from the light source, passing through the optical filter, the test chart, and the rod lens and entering the light receiving element.

JP 2009-216450 A JP 2011-164383 A

  Here, in general, an optical device has a different MTF depending on the wavelength of light. Therefore, there is a need for MTF measurement apparatus for MTF measurement for light of all wavelengths. However, Patent Document 1 does not disclose a configuration for measuring MTF for light of a plurality of wavelengths. Moreover, in the MTF measuring apparatus disclosed in Patent Document 2, in order to measure MTF for light of a plurality of wavelengths (or wavelength regions), it is necessary to use a plurality of optical filters. Therefore, it is virtually impossible to measure MTF for light of any wavelength using the same device, or at least many optical filters must be used.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide an MTF measurement apparatus and an MTF measurement method capable of measuring the MTF of an optical device for light of any wavelength. .

In one embodiment of the present invention,
An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating MTF using an output signal of a converter that photoelectrically converts light emitted from the test chart,
The wavelength selection unit includes a spectroscopic element for separating light emitted from the light source to extract light of a specific wavelength, and an adjustment mechanism for adjusting an incident angle of light incident on the spectroscopic element.
An MTF measurement device is provided.

  According to one aspect of the present invention, the MTF measurement apparatus includes a wavelength selection unit that includes a spectroscopic element and an adjustment mechanism for adjusting the incident angle of light incident on the spectroscopic element. The MTF of the optical device can be measured with respect to light.

It is a figure which shows the MTF measuring apparatus which concerns on Embodiment 1 of this invention. It is a top view which shows the test chart in which the pinhole was formed as a test pattern. It is a top view which shows the test chart in which the slit was formed as a test pattern. It is a top view which shows the test chart in which the edge was formed as a test pattern. It is a top view which shows the test chart in which the rectangular wave pattern was formed as a test pattern. It is a flowchart which shows the MTF measuring method of the solid-state image sensor using the MTF measuring apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the MTF measuring apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the MTF measuring apparatus which concerns on Embodiment 3 of this invention. It is a flowchart which shows the MTF measuring method of the 2nd optical system using the MTF measuring apparatus which concerns on Embodiment 3 of this invention. It is a figure which shows the MTF measuring apparatus which concerns on Embodiment 4 of this invention.

  An MTF measuring apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same or similar components are denoted by the same reference numerals. In addition, in order to prevent the description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art, a detailed description of already known matters and a redundant description of substantially the same configuration may be omitted. . Also, the contents of the following description and the accompanying drawings are not intended to limit the subject matter described in the claims.

Embodiment 1 FIG.
(MTF measuring apparatus 100)
FIG. 1 shows an MTF measuring apparatus 100 according to Embodiment 1 of the present invention. The MTF measurement apparatus 100 includes a light source 101, a wavelength selection unit 102, a light guide 103, a first optical system 104, a test chart 105, and a second optical system 106. In the first embodiment, the MTF of the solid-state imaging device 10 on which the light emitted from the second optical system 106 is incident is measured using the MTF measurement device 100. It is assumed that the MTF value of the second optical system 106 is measured in advance using another apparatus and is a known value. The components (light source, light receiving element, etc.) 101 to 106 may be fixed on the same base member (not shown), or may be detachably arranged.

  The solid-state imaging device 10 may be a CCD (Charge Coupled Device) including a photodiode, a CMOS (Complementary Metal Oxide Semiconductor), or the like. The solid-state image sensor 10 is arranged such that the image plane of the solid-state image sensor 10 is a normal plane with respect to a projection center line connecting the center points of the first optical system 104, the test chart 105, and the second optical system 106. ing. The solid-state imaging device 10 photographs the test chart 105. In the first embodiment, the solid-state imaging device 10 functions as a converter that photoelectrically converts light emitted from the test chart 105. The solid-state imaging device 10 is connected to a driving device 10a that drives the solid-state imaging device 10 and an arithmetic device 107 that can transmit and receive signals.

  The light source 101 emits light 11. The light source 101 may be any light source, but is a white light source, for example.

  The wavelength selection unit 102 includes a diffraction grating 108 and a rotation mechanism 109. The diffraction grating 108 is an example of a spectroscopic element, and has a function of separating the light 11 emitted from the light source 101 and extracting and emitting the light 12 having a specific wavelength. In the drawing, a reflection type diffraction grating is shown as the diffraction grating 108, but a transmission type diffraction grating may be used. The rotation mechanism 109 is fixed to the diffraction grating 108 and is configured to rotate with respect to the light source 101 integrally with the diffraction grating 108. The rotation mechanism 109 may be a motor having a table on which the diffraction grating 108 is placed and an output shaft to which the table is attached. The motor may be a motor (for example, a stepping motor or a servo motor) that can control the rotation angle of the table (and hence the diffraction grating 108). Thus, by rotating the diffraction grating 108, the incident angle of the light incident on the diffraction grating 108 is changed and adjusted, and the wavelength of the emitted light 12 is changed.

  The light guide 103 has a function of guiding the light 12 having a specific wavelength emitted from the diffraction grating 108 of the wavelength selection unit 102 to the test chart 105. The light guide 103 has an entrance end 103a and an exit end 103b. In the embodiment, the light guide 103 is an optical fiber having a core and a clad. By using the light guide 103, the traveling direction of the light 12 emitted from the diffraction grating 108 can be controlled. In addition, the light incident on the light guide 103 travels in the core and is totally totally reflected at the interface with the clad. Thereby, it is possible to emit the light 13 from the emission end 103b in a state where the uniformity of the light 12 incident on the incidence end 103a of the light guide 103 is improved. This improves the accuracy of the measured MTF.

  The first optical system 104 is disposed between the emission end 103 b of the light guide 103 and the test chart 105 on the optical path. The first optical system 104 has a function of collecting the light 13 emitted from the light guide 103 and causing it to enter the test chart 105. In the drawing, one lens is shown as the first optical system 104, but the present invention is not limited to this, and the first optical system 104 may be composed of, for example, a plurality of lenses. By configuring the first optical system 104 with a plurality of lenses, there is an advantage that it is possible to correct aberrations and adjust the focal length.

  A test pattern having a light non-transmissive region and a light transmissive region is formed on the test chart 105. The test pattern may have any shape, but is selected from the group consisting of, for example, a pinhole (FIG. 2), a slit (FIG. 3), an edge (FIG. 4), and a square wave pattern (FIG. 5). The The test pattern of the test chart 105 is formed by providing a light opaque material on the light transmissive member. The light transmissive member may be, for example, a transparent film or transparent glass, and may be rectangular or flat. The light-impermeable material may be made of any material such as chromium oxide, and may be provided using any method such as paint, printing, and vapor deposition.

  The second optical system 106 is disposed between the test chart 105 and the solid-state imaging device 10 on the optical path. The second optical system 106 has a function of forming an image of the light 14 that has passed through the light transmission region of the test pattern formed on the test chart 105 on the pixel region of the solid-state imaging device 10. The second optical system 106 is preferably a telecentric optical system arranged so that the chief ray passes through the focal point. By using a telecentric optical system as the second optical system 106, the principal ray emitted from the test chart 105 passes through the focal point, so that the size of the image center changes even when the focal point is deviated. There is an advantage that In the drawing, one lens is shown as the second optical system 106, but the present invention is not limited to this, and the second optical system 106 may be composed of, for example, a plurality of lenses. By configuring the second optical system 106 with a plurality of lenses, there is an advantage that it is possible to correct aberrations and adjust the focal length.

  The arithmetic unit 107 may be a microcomputer having a CPU (central processing unit) and a memory storing a predetermined program, and by performing a predetermined operation on the pixel signal output from the solid-state image sensor 10. , MTF can be calculated. A specific method for calculating the MTF will be described later.

(Measurement method of MTF)
Next, a method for measuring the MTF of the solid-state imaging device 10 using the MTF measuring apparatus 100 according to the first embodiment will be described with reference to FIG.

  In step 111, the light 11 emitted from the light source 101 is irradiated onto the test chart 105 via the diffraction grating 108, the light guide 103, and the first optical system 104 of the wavelength selection unit 102. At this time, the incident angle of the light 11 emitted from the light source 101 is set to a predetermined angle by the rotation angle of the rotation mechanism 109. Thereby, the wavelength of the light extracted by the diffraction grating 108 is determined. A part of the light 13 irradiated to the test chart 105 is blocked by the light non-transmissive area in the test pattern of the test chart 105, and another part is transmitted through the light transmissive area. Thereby, the test pattern of the test chart 105 is projected onto the pixel region of the solid-state image sensor 10 via the second optical system 106 (that is, the chart image of the test chart 105 is photographed by the solid-state image sensor 10).

  In step 112, the light of the projected test pattern (that is, the light transmitted through the light transmission region) is photoelectrically converted by the solid-state imaging device 10, a test pattern is photographed, output as a pixel signal, and input to the arithmetic unit 107. Is done.

  In step 113, the pixel signal output from the solid-state image sensor 10 is processed by the arithmetic unit 107, and MTF is calculated. Here, the MTF may be calculated by any method, for example, using a known Fourier transform method, or may be calculated using a known contrast method.

  In the Fourier transform method, first, an output distribution with respect to a local light input is measured to obtain an output spread function SF (Spread Function). A spreading function obtained when light enters the solid-state imaging device 10 through the light transmission regions of the test charts 105A, 105B, and 105C in which pinholes, slits, and edges are formed as test patterns shown in FIGS. Are called PSF (Point Spread Function), LSF (Line Spread Function), and ESF (Edge Spread Function), respectively. An OTF is obtained by performing a Fourier transform on the spread function SF. The obtained OTF is a complex function, and its real part is MTF. Note that the LSF can also be obtained by differentiating the ESF.

  In the contrast method, an output with respect to a sine wave input having various frequencies is measured, a response function is obtained from an input / output contrast ratio, and an MTF is calculated from the response function. A rectangular wave response function obtained when light enters the solid-state imaging device 10 through the light transmission region of the test chart 105D on which the rectangular wave pattern shown in FIG. 5 is formed is referred to as SWRF (Square Wave Response Function). The By correcting SWRF to a sinusoidal response function, the MTF is obtained.

  The MTF obtained by the measurement is a value obtained by adding the MTF of the second optical system 106 and the MTF of the solid-state imaging device 10. By subtracting the known MTF of the second optical system 106 from the measured MTF, the MTF of only the solid-state imaging device 10 is calculated.

  Next, the wavelength of the light 12 emitted from the diffraction grating 108 is changed by rotating the rotation mechanism 119 by a desired angle and changing the incident angle of the light incident on the diffraction grating 108. Then, by performing Steps 111 to 113 shown in FIG. 6 again, the MTF of the solid-state imaging device 10 can be measured for the wavelength after the change. By repeating this operation, the MTF of the solid-state imaging device 10 can be measured for light of any wavelength.

  Here, in the solid-state imaging device 10, it is preferable to measure the MTF for light of any wavelength. In the first embodiment, the MTF measurement of the solid-state imaging device 10 can be completed using one MTF measurement device 100. Also, a certain type of solid-state imaging device may require MTF measurement for light of a certain wavelength, and another type of solid-state imaging device may require MTF measurement for light of another wavelength. In the first embodiment, even in such a situation, it is possible to measure the MTFs of a plurality of types of solid-state imaging elements using one MTF measuring apparatus 100.

Embodiment 2. FIG.
FIG. 7 shows an MTF measuring apparatus 200 according to Embodiment 2 of the present invention. In the description of the MTF measuring apparatus 200, the same or similar components as those of the MTF measuring apparatus 100 according to the first embodiment may be denoted by the same reference numerals and description thereof may be omitted.

  The MTF measurement apparatus 200 includes a second wavelength selection unit 202 in addition to the MTF measurement apparatus 100 according to the first embodiment. The second wavelength selection unit 202 includes an optical filter 203 and a reflection plate 204. The optical filter 203 has a function of selectively transmitting light having a specific wavelength or light having a specific wavelength range. For example, the optical filter 203 may be a long-pass filter, a short-pass filter, or a band-pass filter that transmits light in a predetermined wavelength range. The optical filter 203 may be a dielectric multilayer film that selects a wavelength by the light interference effect, or may be a filter glass that selects a wavelength by light absorption. The reflection plate 204 has a function of changing the traveling direction of the light 11 emitted from the light source 101.

  The second wavelength selection unit 202 is provided so as to be switchable between a wavelength selection unit 102 having a diffraction grating 108 and a rotation mechanism 109 (hereinafter referred to as a first wavelength selection unit). The switching operation between the first wavelength selection unit 102 and the second wavelength selection unit 202 may be performed manually or automatically by an actuator (not shown). For example, the wavelength selection units 102 and 202 are arranged on a turntable provided with a switch, and the turntable is rotated by pressing the switch by the user, and the first wavelength selection unit 102 and the second wavelength selection unit 202 are May be switched.

  The MTF measurement method for the solid-state imaging device 10 described in the first embodiment can be implemented using the MTF measurement apparatus 200 according to the second embodiment. When the first wavelength selection unit 102 is selected from the first and second wavelength selection units 102 and 202, the specific wavelength selected by the rotation angle of the rotation mechanism 109 and extracted by the diffraction grating 108 is used. Light enters the test chart 105. On the other hand, when the second wavelength selection unit 202 is selected from the first and second wavelength selection units 102 and 202, the optical filter 203 out of the light emitted from the light source 101 and reflected by the reflection plate 204. For example, light in a specific wavelength region extracted by the above is incident on the test chart 105.

  According to the second embodiment, the first and second wavelength selectors according to the characteristics of the solid-state image sensor 10, that is, according to the wavelength (or wavelength range) where MTF measurement is required in the solid-state image sensor 10. 102 and 202 can be switched and used as necessary. For example, one type of solid-state imaging device may require MTF measurement for light of a specific wavelength, and another type of solid-state imaging device may require MTF measurement for light of a certain wavelength range. In the second embodiment, even in such a situation, the MTFs of a plurality of types of solid-state imaging elements can be measured using one MTF measuring apparatus 100.

Embodiment 3 FIG.
FIG. 7 shows an MTF measuring apparatus 300 according to Embodiment 3 of the present invention. In the description of the MTF measuring apparatus 300, the same or similar components as those of the MTF measuring apparatuses 100 and 200 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The MTF measurement apparatus 300 includes a light receiving element 310 in addition to the light source 101, the wavelength selection unit 102, the light guide 103, the first optical system 104, and the test chart 105 described in the first embodiment. In the third embodiment, the light receiving element 310 functions as a converter that photoelectrically converts light emitted from the test chart 105. In the third embodiment, the MTF of the second optical system 30 disposed between the test chart 105 and the light receiving element 310 on the optical path is measured using the MTF measuring apparatus 300. It is assumed that the MTF value of the light receiving element 310 is measured in advance using another device and is a known value. The components 101 to 105 and 310 may be fixed on the same base member (not shown), or may be arranged so as to be separable from each other.

  Similar to the solid-state imaging device 10 described in the first embodiment, the light receiving element 310 is connected to a driving device 310 a that drives the light receiving element 310 and an arithmetic unit 107 that can transmit and receive signals. The arithmetic unit 107 is configured to calculate the MTF by performing a predetermined calculation on the pixel signal output from the light receiving element 310.

  Next, a method for measuring the MTF of the second optical system 30 using the MTF measuring apparatus 300 according to the third embodiment will be described with reference to FIG.

  In step 311, the light 11 emitted from the light source 101 is irradiated onto the test chart 105 through the diffraction grating 108, the light guide 103, and the first optical system 104 of the wavelength selection unit 102. At this time, the incident angle of the light 11 emitted from the light source 101 is set to a predetermined angle by the rotation angle of the rotation mechanism 109. Thereby, the wavelength of the light extracted by the diffraction grating 108 is determined. A part of the light 13 irradiated to the test chart 105 is blocked by the light non-transmissive area in the test pattern of the test chart 105, and another part is transmitted through the light transmissive area. As a result, the test pattern of the test chart 105 is projected onto the light receiving surface of the light receiving element 310 via the second optical system 30.

  In step 312, the light of the projected test pattern (that is, the light transmitted through the light transmission region) is photoelectrically converted by the light receiving element 310, and the output signal is input to the arithmetic unit 107.

  In step 113, the output signal of the solid-state image sensor 10 is processed by the arithmetic unit 107, and the MTF is calculated. Here, the MTF may be calculated by an arbitrary method, for example, may be calculated using a Fourier transform method, or may be calculated using a contrast method. These methods are as already described.

  The wavelength of the light 12 emitted from the diffraction grating 108 is changed by rotating the rotation mechanism 119 by a desired angle and changing the incident angle of the light incident on the diffraction grating 108. Then, by performing steps 311 to 313 shown in FIG. 9 again, the MTF of the second optical system 30 can be measured for the wavelength after the change. By repeating this operation, the MTF of the second optical system 30 can be measured for light of any wavelength.

Embodiment 4 FIG.
FIG. 8 is a diagram showing an MTF measurement apparatus 400 according to Embodiment 4 of the present invention. In the description of the MTF measuring apparatus 400, the same or similar components as those of the MTF measuring apparatuses 100, 200, and 300 according to the first to third embodiments are denoted by the same reference numerals and description thereof is omitted.

  The MTF measurement apparatus 400 includes the second wavelength selection unit 202 described in the second embodiment in addition to the MTF measurement apparatus 300 according to the third embodiment. The configuration of the second wavelength selection unit 202 is as already described.

  The MTF measurement method of the second optical system 30 described in the third embodiment can be implemented using the MTF measurement apparatus 400 according to the fourth embodiment.

  According to the fourth embodiment, the first and second wavelengths depend on the characteristics of the second optical system 30, that is, depending on the wavelength (or wavelength range) where MTF measurement is required in the second optical system 30. The selection units 102 and 202 can be switched and used as necessary. For example, one type of optical system may require MTF measurement for light of a specific wavelength, and another type of optical system may require MTF measurement for light of a certain wavelength range. In the fourth embodiment, even in such a situation, the MTFs of a plurality of types of second optical systems can be measured using one MTF measuring apparatus 400.

(Modification)
Although the present invention has been described using a plurality of embodiments, the features described in each embodiment may be freely combined. In addition, various improvements, design changes, and deletions may be added to the above-described embodiments, and various modifications exist in the present invention.

  For example, in the above-described embodiment, an example in which the diffraction grating 108 is used as a spectroscopic element has been described. However, the present invention is not limited to this, and other spectroscopic elements such as a prism may be used.

  In the above-described embodiment, the rotation mechanism 109 is used as an adjustment mechanism for changing the incident angle of light incident on the diffraction grating 108. However, the present invention is not limited to this, and for example, the light source 101 and A rotatable mirror provided between the diffraction grating 108 and the diffraction grating 108 may be used as the adjusting mechanism.

  In the above-described embodiment, the example using the light guide 103 and the first optical system 104 has been described. However, the present invention is not limited to this, and these components are omitted, and the wavelength selection units 102 and 202 are used. Light may directly enter the test chart 105.

  In the above-described embodiment, an example in which the light guide 103 is used as a mechanism for improving the uniformity of light has been described. However, the present invention is not limited to this, and a light such as a diffusion plate or a lens array is used. Other mechanisms that improve the uniformity of the image may be used. Further, a combination of the light guide 103 and a diffusion plate or lens array may be used.

  In the above-described embodiment, Embodiments 1 and 2 have been described as examples of measuring the MTF of the solid-state imaging device 10, and Embodiments 3 and 4 have been described as examples of measuring the MTF of the second optical system 30. For example, an MTF measurement apparatus that measures the MTF of the solid-state imaging device by arranging a second optical system with a known MTF value is configured, and then the solid-state imaging device is replaced with a light-receiving device with a known MTF value. An MTF measuring device that measures the MTF of the second optical system may be configured by replacing the second optical system with one whose MTF is not known.

(Aspect of the present invention)
Next, the MTF measuring apparatus according to the first aspect of the present invention and the MTF measuring method according to the second aspect of the present invention will be described using the reference numerals attached in the above-described embodiment. It should be understood that the reference numerals assigned to each component do not limit the scope of the present invention.

  In a first aspect of the present invention, there are provided MTF measuring apparatuses 100, 200, 300, 400 for measuring the MTF of an optical device. The MTF measuring apparatus includes a test chart 105 on which a test pattern having a light non-transmissive area and a light transmissive area is formed, a light source 101 for irradiating the test chart 105 with light, and a wavelength of light emitted from the light source 101. A wavelength selection unit 102 for selection and an arithmetic unit 107 for calculating MTF using an output signal of a converter that photoelectrically converts light emitted from the test chart 105 are provided. The wavelength selectors 102 and 202 have a spectroscopic element for separating light emitted from the light source 101 and extracting light of a specific wavelength, and an adjustment mechanism for changing the incident angle of the light incident on the spectroscopic element. ing.

  According to the first aspect of the present invention, the MTF measuring apparatus 100, 200, 300, 400 includes the spectral element and the wavelength selection unit 102 having the adjusting mechanism for changing the incident angle of the light incident on the spectral element. The MTF of the optical device can be measured with respect to light of any wavelength.

  In one embodiment of the first aspect of the present invention, the solid-state imaging device 10 is used as a converter. Further, the MTF measuring apparatuses 100 and 200 are arranged between the test chart 105 and the solid-state image sensor 10 on the optical path, and form an image on the pixel area of the solid-state image sensor 10 through the light transmitting area of the test pattern. A second optical system 106 is further provided. Then, the MTF measuring apparatuses 100 and 200 measure the MTF of the solid-state imaging device 10 as the MTF of the optical device.

  According to this embodiment, the light emitted from the light source 101 is applied to the spectral element of the wavelength selection unit 102, and a part of the emitted light from the spectral element is blocked by the light non-transmissive region in the test pattern of the test chart 105. And another part is transmitted through the light transmission region. As a result, the test pattern of the test chart 105 is projected onto the pixel region of the solid-state image sensor 10 via the second optical system 106, and the output of the solid-state image sensor 10 is transmitted to the arithmetic unit 107. Thereby, the MTF of the solid-state image sensor 10 is calculated. In this manner, the effects obtained by one embodiment of the present invention are specifically achieved.

  In one embodiment of the first aspect of the present invention, the MTF measuring devices 300 and 400 include a light receiving element 310 as a converter. The MTF measuring apparatuses 300 and 400 are arranged between the test chart 105 and the light receiving element 310 on the optical path as the MTF of the optical device, and are used for forming an image of the test pattern on the light receiving surface of the light receiving element 310. The MTF of the optical system 30 is measured.

  According to this embodiment, the light emitted from the light source 101 is applied to the spectral element of the wavelength selection unit 102, and a part of the emitted light from the spectral element is blocked by the light non-transmissive region in the test pattern of the test chart 105. And another part is transmitted through the light transmission region. As a result, the test pattern of the test chart 105 is projected onto the light receiving surface of the light receiving element 310 via the second optical system 30, and the output of the light receiving element 310 is transmitted to the arithmetic unit 107. The MTF is calculated. Thus, the effect obtained by the first aspect of the present invention is specifically achieved.

  Here, the second optical system 106 may be a telecentric optical system. By using a telecentric optical system, since the principal ray passes through the focal point, the size of the image center changes even when the focal point is deviated, and uniform illuminance is obtained over the entire field of view.

  In the first aspect of the present invention, the spectroscopic element may be the diffraction grating 108 or a prism.

  In the first aspect of the present invention, the adjustment mechanism may include a rotation mechanism 109 configured to rotate the spectroscopic element with respect to the light source.

  In one embodiment of the first aspect of the present invention, the MTF measurement devices 200 and 400 include the second wavelength in addition to the wavelength selection unit (referred to as the first wavelength selection unit) 102 having a spectroscopic element and an adjustment mechanism. A selection unit 202 is further provided. The second wavelength selection unit 202 is provided so as to be switchable with the first wavelength selection unit 102. The second wavelength selection unit 202 has an optical filter 203.

  According to this embodiment, in the optical device to be measured for MTF, the first and second wavelength selection units 102 and 202 can be arbitrarily switched and used according to the wavelength (or wavelength range) where MTF measurement is required. .

  In one embodiment of the first aspect of the present invention, the MTF measuring devices 100, 200, 300, and 400 include a light guide 103 that guides light of a specific wavelength emitted from the wavelength selectors 102 and 202 to the test chart 105. And a first optical system 104 for condensing the light emitted from the light guide 103, which is disposed between the emission end 103b of the light guide 103 and the test chart 105 on the optical path.

  According to this embodiment, by using the light guide 103, the traveling direction of the light emitted from the spectroscopic element can be controlled. In addition, the light incident on the light guide 103 travels in the core and is totally totally reflected at the interface with the clad. As a result, the light can be emitted from the emission end 104b in a state where the uniformity of the light incident on the incidence end 104a of the light guide 103 is improved. This improves the accuracy of the measured MTF.

  In the first aspect of the present invention, the test pattern formed on the test chart 105 may be selected from the group consisting of pinholes, slits, edges, and rectangular wave patterns.

  In the second aspect of the present invention, an MTF measurement method for measuring the MTF of an optical device (the solid-state imaging device 10, the second optical system 30, etc.) is provided. The MTF measurement method includes a step of selecting a wavelength of light emitted from the light source 101 using the wavelength selection unit 102, and a test pattern having light non-transmission regions and light transmission regions for light emitted from the wavelength selection unit 102. Are made incident on the test chart 105 formed, a step of photoelectrically converting light emitted from the test chart 105 using a converter (the solid-state imaging device 10, a light receiving element 310, etc.), and Calculating an MTF using the output signal. The step of selecting the wavelength of the light includes a step of separating light emitted from the light source 101 using a spectroscopic element (such as the diffraction grating 108) included in the wavelength selection unit 102 and extracting light of a specific wavelength, and a wavelength selection unit. And adjusting an incident angle of light incident on the spectroscopic element 108 by using an adjusting mechanism (such as a rotating mechanism 109) included in 102.

  According to the second aspect of the present invention, the light emitted from the light source 101 is dispersed using the spectroscopic element 108, and light having a specific wavelength is extracted. At this time, the incident angle of light incident on the spectroscopic element 108 is adjusted using the adjusting mechanism 109. In this way, the MTF of the optical devices 10 and 30 can be measured for light of any wavelength.

DESCRIPTION OF SYMBOLS 10 Solid-state image sensor, 10a Drive apparatus, 11-14 light, 30 2nd optical system, 100,200,300,400 MTF measuring apparatus, 101 Light source, 102,202
Wavelength selection unit, 103 light guide, 104 first optical system, 105, 105A, 105B, 105C, 105D test chart, 106 second optical system, 107 arithmetic unit, 108 diffraction grating, 109 rotating mechanism, 310 light receiving element, 310a drive apparatus

Claims (19)

An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating an MTF using an output signal of a solid-state imaging device that photoelectrically converts light emitted from the test chart ;
A second optical system disposed between the test chart and the solid-state image sensor on an optical path, for imaging light that has passed through a light transmission region of the test pattern on a pixel area of the solid-state image sensor; ,
It said wavelength selection section, possess a spectral element for extracting light of a specific wavelength by dispersing the light emitted from the light source, and an adjustment mechanism for adjusting the incident angle of light incident on the spectral element,
The second optical system is a telecentric optical system,
The MTF measuring apparatus measures the MTF of the solid-state imaging device as the MTF of the optical device.
MTF measuring device. An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating an MTF using an output signal of a solid-state imaging device that photoelectrically converts light emitted from the test chart ;
A second optical system disposed between the test chart and the solid-state image sensor on an optical path, for imaging light that has passed through a light transmission region of the test pattern on a pixel region of the solid-state image sensor;
A light guide for guiding the light of a specific wavelength emitted from the wavelength selector to the test chart;
A first optical system disposed on an optical path between the light guide emission end and the test chart, for collecting light emitted from the light guide ;
It said wavelength selection section, possess a spectral element for extracting light of a specific wavelength by dispersing the light emitted from the light source, and an adjustment mechanism for adjusting the incident angle of light incident on the spectral element,
The MTF measuring apparatus measures the MTF of the solid-state imaging device as the MTF of the optical device.
MTF measuring device. An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating an MTF using an output signal of a solid-state imaging device that photoelectrically converts light emitted from the test chart ;
A second optical system disposed between the test chart and the solid-state image sensor on an optical path, for imaging light that has passed through a light transmission region of the test pattern on a pixel region of the solid-state image sensor;
A diffusion plate or a lens array for guiding light of a specific wavelength emitted from the wavelength selection unit to the test chart;
A first optical system disposed on the optical path between the diffusing plate or lens array and the test chart for condensing light emitted from the diffusing plate or lens array ;
It said wavelength selection section, possess a spectral element for extracting light of a specific wavelength by dispersing the light emitted from the light source, and an adjustment mechanism for adjusting the incident angle of light incident on the spectral element,
The MTF measuring apparatus measures the MTF of the solid-state imaging device as the MTF of the optical device.
MTF measuring device. An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating MTF using an output signal of a light receiving element that photoelectrically converts light emitted from the test chart ;
A second optical system disposed on the optical path between the test chart and the light receiving element, for imaging the test pattern on a light receiving surface of the light receiving element ;
It said wavelength selection section, possess a spectral element for extracting light of a specific wavelength by dispersing the light emitted from the light source, and an adjustment mechanism for adjusting the incident angle of light incident on the spectral element,
The second optical system is a telecentric optical system,
The MTF measuring apparatus measures the MTF of the second optical system as the MTF of the optical device;
MTF measuring device. An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating MTF using an output signal of a light receiving element that photoelectrically converts light emitted from the test chart ;
A second optical system disposed on the optical path between the test chart and the light receiving element, for imaging the test pattern on a light receiving surface of the light receiving element;
A light guide for guiding the light of a specific wavelength emitted from the wavelength selector to the test chart;
A first optical system disposed on an optical path between the light guide emission end and the test chart, for collecting light emitted from the light guide ;
It said wavelength selection section, possess a spectral element for extracting light of a specific wavelength by dispersing the light emitted from the light source, and an adjustment mechanism for adjusting the incident angle of light incident on the spectral element,
The MTF measuring apparatus measures the MTF of the second optical system as the MTF of the optical device;
MTF measuring device. An MTF measuring apparatus for measuring the MTF of an optical device,
A test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
A light source for irradiating the test chart with light;
A wavelength selector for selecting a wavelength of light emitted from the light source;
An arithmetic unit for calculating MTF using an output signal of a light receiving element that photoelectrically converts light emitted from the test chart ;
A second optical system disposed on the optical path between the test chart and the light receiving element, for imaging the test pattern on a light receiving surface of the light receiving element;
A diffusion plate or a lens array for guiding light of a specific wavelength emitted from the wavelength selection unit to the test chart;
A first optical system disposed on the optical path between the diffusing plate or lens array and the test chart for condensing light emitted from the diffusing plate or lens array ;
It said wavelength selection section, possess a spectral element for extracting light of a specific wavelength by dispersing the light emitted from the light source, and an adjustment mechanism for adjusting the incident angle of light incident on the spectral element,
The MTF measuring apparatus measures the MTF of the second optical system as the MTF of the optical device;
MTF measuring device. The second optical system is a telecentric optical system.
The MTF measuring device according to any one of claims 2 , 3, 5, and 6 . A light guide for guiding the light of a specific wavelength emitted from the wavelength selector to the test chart;
A first optical system disposed on the optical path between the light guide emission end and the test chart, for collecting light emitted from the light guide;
The MTF measuring apparatus according to any one of claims 1 , 3, 4, and 6 . A diffusion plate or a lens array for guiding light of a specific wavelength emitted from the wavelength selection unit to the test chart;
A first optical system disposed on the optical path between the diffusing plate or lens array and the test chart and for collecting light emitted from the diffusing plate or lens array;
The MTF measuring apparatus according to any one of claims 1 , 2, 4, and 5 . The spectroscopic element is a diffraction grating or a prism.
The MTF measuring apparatus according to any one of claims 1 to 9 . The adjustment mechanism includes a rotation mechanism configured to rotate the spectroscopic element with respect to the light source.
The MTF measuring apparatus according to any one of claims 1 to 10 . A second wavelength selection unit provided to be switchable between the spectral element and the first wavelength selection unit having the adjustment mechanism;
The second wavelength selector has an optical filter;
The MTF measuring apparatus according to any one of claims 1 to 11 . The test pattern formed on the test chart is selected from the group consisting of pinholes, slits, edges, and rectangular wave patterns.
The MTF measuring apparatus according to any one of claims 1 to 12 . An MTF measurement method for measuring an MTF of an optical device, comprising:
Selecting a wavelength of light emitted from the light source using the wavelength selection unit;
Making the light emitted from the wavelength selection section enter a test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
Photoelectrically converting light emitted from the test chart using a solid-state imaging device ;
And a step of calculating an MTF of the solid-state imaging device using an output signal of the solid-
The step of selecting the wavelength of the light comprises
Using a spectroscopic element included in the wavelength selection unit to split light emitted from the light source and extract light of a specific wavelength;
Using the adjustment mechanism included in said wavelength selection section, viewed including the step of adjusting the incident angle of incident light to the spectral element,
The step of photoelectrically converting the light emitted from the test chart includes light that has passed through a light transmission region of the test pattern using a telecentric optical system disposed between the test chart and the solid-state imaging device on an optical path. including the steps of forming an image on the pixel region of the solid-
MTF measurement method. An MTF measurement method for measuring an MTF of an optical device, comprising:
Selecting a wavelength of light emitted from the light source using the wavelength selection unit;
Making the light emitted from the wavelength selection section enter a test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
Photoelectrically converting light emitted from the test chart using a solid-state imaging device ;
And a step of calculating an MTF of the solid-state imaging device using an output signal of the solid-
The step of selecting the wavelength of the light comprises
Using a spectroscopic element included in the wavelength selection unit to split light emitted from the light source and extract light of a specific wavelength;
Using the adjustment mechanism included in said wavelength selection section, viewed including the step of adjusting the incident angle of incident light to the spectral element,
The step of causing the light emitted from the wavelength selection unit to enter the test chart includes:
Injecting light of a specific wavelength emitted from the wavelength selection unit into an incident end of a light guide, and guiding the light to the output end of the light guide;
Condensing the light emitted from the light guide using a first optical system disposed on the optical path between the light guide emission end and the test chart;
The step of photoelectrically converting the light emitted from the test chart has passed through the light transmission region of the test pattern using the second optical system disposed between the test chart and the solid-state imaging device on the optical path. including the step of focusing the light to a pixel region of the solid-
MTF measurement method. An MTF measurement method for measuring an MTF of an optical device, comprising:
Selecting a wavelength of light emitted from the light source using the wavelength selection unit;
Making the light emitted from the wavelength selection section enter a test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
Photoelectrically converting light emitted from the test chart using a solid-state imaging device ;
And a step of calculating an MTF of the solid-state imaging device using an output signal of the solid-
The step of selecting the wavelength of the light comprises
Using a spectroscopic element included in the wavelength selection unit to split light emitted from the light source and extract light of a specific wavelength;
Using the adjustment mechanism included in said wavelength selection section, viewed including the step of adjusting the incident angle of incident light to the spectral element,
The step of causing the light emitted from the wavelength selection unit to enter the test chart includes:
Making the light of a specific wavelength emitted from the wavelength selector enter the diffuser or the lens array;
Condensing light emitted from the diffuser plate or lens array using a first optical system disposed on the optical path between the diffuser plate or lens array and the test chart,
The step of photoelectrically converting the light emitted from the test chart has passed through the light transmission region of the test pattern using the second optical system disposed between the test chart and the solid-state imaging device on the optical path. including the step of focusing the light to a pixel region of the solid-
MTF measurement method. An MTF measurement method for measuring an MTF of an optical device, comprising:
Selecting a wavelength of light emitted from the light source using the wavelength selection unit;
Making the light emitted from the wavelength selection section enter a test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
Photoelectrically converting light emitted from the test chart using a light receiving element ;
Calculating MTF using an output signal of the light receiving element ,
The step of selecting the wavelength of the light comprises
Using a spectroscopic element included in the wavelength selection unit to split light emitted from the light source and extract light of a specific wavelength;
Using the adjustment mechanism included in said wavelength selection section, viewed including the step of adjusting the incident angle of incident light to the spectral element,
The step of photoelectrically converting the light emitted from the test chart includes connecting the test pattern to the light receiving surface of the light receiving element using a telecentric optical system disposed between the test chart and the light receiving element on the optical path. Including the step of imaging
The step of calculating the MTF is a step of measuring the MTF of the telecentric optical system using an output signal of the light receiving element.
MTF measurement method. An MTF measurement method for measuring an MTF of an optical device, comprising:
Selecting a wavelength of light emitted from the light source using the wavelength selection unit;
Making the light emitted from the wavelength selection section enter a test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
Photoelectrically converting light emitted from the test chart using a light receiving element ;
Calculating MTF using an output signal of the light receiving element ,
The step of selecting the wavelength of the light comprises
Using a spectroscopic element included in the wavelength selection unit to split light emitted from the light source and extract light of a specific wavelength;
Using the adjustment mechanism included in said wavelength selection section, viewed including the step of adjusting the incident angle of incident light to the spectral element,
The step of causing the light emitted from the wavelength selection unit to enter the test chart includes:
Injecting light of a specific wavelength emitted from the wavelength selection unit into an incident end of a light guide, and guiding the light to the output end of the light guide;
Condensing the light emitted from the light guide using a first optical system disposed on the optical path between the light guide emission end and the test chart;
The step of photoelectrically converting the light emitted from the test chart comprises using the second optical system disposed between the test chart and the light receiving element on the optical path, and applying the test pattern to the light receiving surface of the light receiving element. Including imaging ,
The step of calculating the MTF is a step of measuring the MTF of the second optical system using an output signal of the light receiving element.
MTF measurement method. An MTF measurement method for measuring an MTF of an optical device, comprising:
Selecting a wavelength of light emitted from the light source using the wavelength selection unit;
Making the light emitted from the wavelength selection section enter a test chart on which a test pattern having a light non-transmissive region and a light transmissive region is formed;
Photoelectrically converting light emitted from the test chart using a light receiving element ;
Calculating MTF using an output signal of the light receiving element ,
The step of selecting the wavelength of the light comprises
Using a spectroscopic element included in the wavelength selection unit to split light emitted from the light source and extract light of a specific wavelength;
Using the adjustment mechanism included in said wavelength selection section, viewed including the step of adjusting the incident angle of incident light to the spectral element,
The step of causing the light emitted from the wavelength selection unit to enter the test chart includes:
Making the light of a specific wavelength emitted from the wavelength selector enter the diffuser or the lens array;
Condensing light emitted from the diffuser plate or lens array using a first optical system disposed on the optical path between the diffuser plate or lens array and the test chart,
The step of photoelectrically converting the light emitted from the test chart comprises using the second optical system disposed between the test chart and the light receiving element on the optical path, and applying the test pattern to the light receiving surface of the light receiving element. Including imaging ,
The step of calculating the MTF is a step of measuring the MTF of the second optical system using an output signal of the light receiving element.
MTF measurement method.

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