JP6569296B2 - Lens unit and imaging device - Google Patents

Description

  The present invention relates to a lens unit and an imaging apparatus.

  In an imaging device equipped with an image sensor such as a CCD (Charge Coupled Device) sensor or CMOS (Complementary Metal Oxide Semiconductor) sensor as an imaging device, an optical system is designed on the premise of image processing, and an image obtained by the optical system is subjected to image processing. There is a method of optimizing the system by restoring it. By using this method, various effects that cannot be realized by a normal optical system can be realized.

  As an example of such an imaging apparatus, an imaging apparatus that outputs an EDOF (Expanded Depth of Field) image in which a depth of field is expanded by a wavefront coding (WFC) method is known (for example, a patent) Reference 1). This type of imaging apparatus includes an optical phase modulation element disposed in the vicinity of the stop position of the imaging optical system. The optical phase modulation element gives spherical aberration to the light passing through the imaging optical system to modulate the phase of the light, and changes the imaging characteristics of the imaging optical system. Specifically, a point spread function (PSF) on the image plane of the image sensor is diffused so as to extend over two or more pixels. The imaging apparatus generates and outputs an EDoF image by performing processing for restoring the modulation by the optical phase modulation element, that is, processing for restoring the diffused PSF, on the image data output from the imaging element. . The diaphragm in the imaging apparatus described in Patent Document 1 is a general diaphragm mechanism (so-called mechanical diaphragm) configured as a separate body from the optical phase modulation element. With such a mechanical aperture, it is possible to easily suppress the reflectance to a low value (less than 1%) by performing processing such as general satin processing.

  In this invention, the structure which provided the aperture_diaphragm | restriction film | membrane which functions as an aperture_diaphragm | restriction in the optical phase modulation element was employ | adopted. Unlike the mechanical diaphragm, this diaphragm film is formed integrally with the optical phase modulation element. When such a diaphragm film is employed, it is extremely difficult to perform a process such as a satin process that suppresses the reflectance, which was possible in the case of a mechanical diaphragm.

  Various evaluations and examinations were performed on the quality of the EDoF image obtained by the imaging apparatus having such a diaphragm film while changing the type of the subject. It has been found that a ghost image that has not been confirmed in the configuration using the mechanical aperture may be reflected in the EDoF image. This is because the reflectivity of the diaphragm film is higher than that of a general mechanical diaphragm, so when strong light enters the imaging optical system, the light reflected by the diaphragm film becomes stray light and enters the image sensor. It is by doing. Since an EDoF image in which a ghost image is reflected is an image having a deteriorated quality, it is required to suppress the generation of the ghost image.

In order to solve the above-described problems, the present invention includes a lens unit that is disposed between a subject and an image sensor, and includes at least one lens that forms an image of light from the subject on the image sensor. an imaging optical system, wherein arranged in the imaging beam path of the optical system, an optical phase modulator for changing the phase of light passing through the imaging optical system, the surface of the front SL imaging element side of the optical phase modulator provided, limits the outgoing light from the optical phase modulator, a diaphragm film having a reflectivity equal to or larger than the reference value, provided in the diaphragm layer is said not to expose the imaging element side throttle film, the imaging A light shielding member that shields stray light that enters the diaphragm film from the element side or stray light that travels from the diaphragm film to the imaging element.

  According to the present invention, it is possible to effectively suppress the generation of a ghost image due to reflection on the diaphragm film.

FIG. 1 is a diagram illustrating a hardware configuration example of the imaging apparatus. FIG. 2 is a diagram showing an example of the shape of the optical surface of the optical phase modulation element. FIG. 3 is a diagram showing an example of the layout around the optical phase modulation element. FIG. 4 is a diagram for explaining the principle of generating a ghost image. FIG. 5 is a diagram for explaining the light shielding effect of the light shielding member. FIG. 6 is a diagram illustrating a specific example of lens characteristics of the depth of field expansion system. FIG. 7 shows an MD curve in the case of using the depth-of-field expansion system having the lens characteristics shown in FIG. 6 and an MD curve in the case of using a normal imaging optical system in which no optical phase modulation element is provided. It is a figure shown by contrast. FIG. 8 is a diagram illustrating an example of an image when the light shielding member is not provided. FIG. 9 is a diagram illustrating an example of an image when a light shielding member is provided. FIG. 10 is a diagram illustrating another specific example of the lens characteristics of the depth-of-field expansion system. FIG. 11 shows an MD curve in the case of using the depth-of-field expanding system having the lens characteristics shown in FIG. 10 and an MD curve in the case of using a normal imaging optical system in which no optical phase modulation element is provided. It is a figure shown by contrast. FIG. 12 is a diagram illustrating an example of an image when the light shielding member is not provided. FIG. 13 is a diagram illustrating an example of an image when a light shielding member is provided. FIG. 14 is a diagram illustrating another example of the layout around the optical phase modulation element. FIG. 15 is a diagram illustrating another example of the layout around the optical phase modulation element. FIG. 16 is a diagram illustrating another example of the layout around the optical phase modulation element. FIG. 17 is a diagram illustrating another example of the layout around the optical phase modulation element. FIG. 18 is a diagram illustrating an example in which the light shielding member has a function as a holding member. FIG. 19 is a diagram illustrating an example in which a roughened surface is formed on the emission surface of the optical phase modulation element to form a light shielding unit. FIG. 20 is a diagram illustrating a modification of the imaging device.

  Hereinafter, embodiments of a lens unit and an imaging apparatus according to the present invention will be described in detail with reference to the accompanying drawings. The imaging apparatus according to the present embodiment is an imaging apparatus that outputs an EDoF image in which the depth of field is expanded by the WFC method. The lens unit of this embodiment is used as an optical system of this imaging apparatus. An optical phase modulation element is disposed in the vicinity of the aperture position of the imaging optical system of the lens unit, and an aperture film is provided on the optical phase modulation element. Then, the aperture film is configured to reduce the incident light to the optical phase modulation element or the outgoing light from the optical phase modulation element so that the F value of the imaging optical system becomes a desired value. In addition, in order to suppress the generation of a ghost image due to reflection at the diaphragm film, a light shielding unit is provided for shielding stray light incident on the diaphragm film from the image sensor side or stray light from the diaphragm film toward the image sensor. Yes.

  FIG. 1 is a diagram illustrating a hardware configuration example of an imaging apparatus 100 according to the present embodiment. The imaging apparatus 100 includes a main body 20 and a lens unit 10 configured to be detachable from the main body 20. Note that the imaging apparatus 100 may have a configuration in which the lens unit 10 and the main body 20 are integrated.

  The main body 20 includes an imaging element 21 using an image sensor such as a CCD sensor or a CMOS sensor, and an EDoF image in which the depth of field is expanded by performing restoration processing on the image data output from the imaging element 21. And an image processing device 22 for generating and outputting. In addition to a light receiving element array that photoelectrically converts light from a subject and outputs an analog signal corresponding to the amount of received light, the image pickup element 21 performs AFE such as gain adjustment and AD conversion on the analog signal output from the light receiving element array. It also includes an AFE circuit that performs (Analog Front End) processing and outputs image data.

  The image processing device 22 performs restoration processing for restoring modulation by an optical phase modulation element 12 described later, ie, the optical phase modulation element 12, for image data output from the imaging element 21 (hereinafter referred to as “intermediate image”). A process for restoring the diffused PFS is performed to generate an EDoF image with an expanded depth of field. The restoration processing by the image processing device 22 is realized as, for example, filter processing for applying a deconvolution (deconvolution operation) / filter to the intermediate image. Due to the phase modulation by the optical phase modulation element 12, an intermediate image in which the PSF does not depend on the amount of defocus is output from the imaging element 21. Therefore, the image processing device 22 can generate an EDoF image by performing a filtering process using one deconvolution filter corresponding to the modulation by the optical phase modulation element 12 on the intermediate image. . Since this type of restoration processing is a known technique, detailed description thereof is omitted here.

  For example, the image processing apparatus 22 may be configured using dedicated hardware (integrated circuit) such as an FPGA (Field-Programmable Gate Array). In this case, the restoration process executed by the image processing device 22 is a hardware process using dedicated hardware. Further, the image processing apparatus 22 may be configured to use a normal computer system including a processor such as a CPU and a memory such as a ROM and a RAM as hardware. In this case, the restoration process executed by the image processing device 22 is a software process executed on the computer system.

  The lens unit 10 includes an imaging optical system 11 including at least one lens, and an optical phase modulation element 12 disposed in the optical path of the imaging optical system 11. Each member arranged around the optical phase modulation element 12 will be described later with reference to FIG.

  The imaging optical system 11 is an optical system that images light from the subject Ob on the image sensor 21. In the present embodiment, for example, a subject that is required to capture a focused image for correctly recognizing information such as code information such as barcodes and two-dimensional codes and various character strings is set as the subject Ob. Assumed. Since the imaging apparatus 100 according to the present embodiment outputs an EDoF image in which the depth of field is expanded, even if the distance from the imaging apparatus 100 to the subject Ob is slightly changed, or the subject Ob is relative to the imaging apparatus 100. Even when shooting is performed in an oblique state, an image in focus on the subject Ob can be obtained.

  The optical phase modulation element 12 is disposed near the stop position Pd in the optical path of the imaging optical system 11, modulates the phase of light from the subject Ob passing through the imaging optical system 11, and forms an image by the imaging optical system 11. It is an optical element that changes the characteristics. The light from the subject Ob passes through the optical phase modulation element 12 to generate spherical aberration for expanding the depth of field, so that the PSF on the image plane of the imaging element 21 extends over two pixels or more. Diffused. In the lens unit 10 of the present embodiment, the optical phase modulation element 12 is provided in the optical path of the imaging optical system 11, so that the optical image of the subject Ob is formed on the image plane of the image pickup element 21 with aberration. Let me image. In the lens unit 10 of the present embodiment, it is desirable that the optical phase modulation element 12 be detachable from the imaging optical system 11. With this configuration, the optical phase modulation element 12 can be exchanged depending on the application, or the imaging optical system 11 can be used as a normal imaging optical system without using the optical phase modulation element 12. It becomes possible.

  In the lens unit 10 of the present embodiment, since the optical phase modulation element 12 is disposed in the vicinity of the stop position Pd of the imaging optical system 11, the optical phase modulation element 12 is provided on the subject Ob side or the image pickup element 21 side. By providing a diaphragm film that functions as a diaphragm, the F value of the imaging optical system 11 can be set to a desired value. Since such a diaphragm film is directly formed on the outer peripheral portion of the optically effective portion of the optical phase modulation element 12, positioning is performed as compared with a general mechanical diaphragm configured separately from the optical phase modulation element 12. Excellent accuracy.

  FIG. 2 is a diagram showing an example of the shape of the optical surface of the optical phase modulation element 12, where the horizontal axis represents the normalized radius and the vertical axis represents the surface shape (zag amount). A typical shape example is shown. In the figure, d1 represents the position of the stop provided coaxially with the optically effective portion of the optical phase modulation element 12, and d2 in the figure is not coaxial with the optically effective portion of the optical phase modulation element 12 (positional displacement occurs). It shows the position of the aperture. When the position accuracy of the diaphragm with respect to the optical phase modulation element 12 is poor as indicated by d2 in the figure, the peripheral shape of the optical effective portion of the optical phase modulation element 12 is kicked or light enters outside the optical effective portion. As a result, the depth-of-field expansion characteristic as designed cannot be obtained.

  As shown by d1 in FIG. 2, in order to realize a diaphragm with high positional accuracy with respect to the optical phase modulation element 12, it is more suitable to use the above-described diaphragm film than to use a mechanical diaphragm. That is, by using a diaphragm film formed directly on the optical phase modulation element 12 as the diaphragm of the imaging optical system 11, the diaphragm and the optical phase modulation element 12 have high coaxiality, and an excellent depth of field expansion. Characteristics can be obtained. In addition, by using a diaphragm film as the diaphragm of the imaging optical system 11, there is no need to provide a mechanical diaphragm, so that advantages such as cost reduction and improved assembling performance can be obtained by reducing the number of parts. Therefore, in the lens unit 10 of the present embodiment, a diaphragm film is used as the diaphragm of the imaging optical system 11.

  FIG. 3 is a diagram showing an example of the layout around the optical phase modulation element 12 in the lens unit 10 of the present embodiment. As shown in FIG. 3, a diaphragm film 13 formed so as to cover the outer peripheral portion of the optically effective portion is provided on the surface (hereinafter referred to as “incident surface”) 12a of the optical phase modulation element 12 on the subject Ob side. ing. The diaphragm film 13 functions as a diaphragm for narrowing the incident light to the optical phase modulation element 12. For example, a black matrix material is formed on the outer peripheral portion of the optically effective portion on the incident surface 12 a of the optical phase modulation element 12. It is formed by doing. As the black matrix material, there are a chromium material and a resin material.

  The diaphragm film 13 provided in the optical phase modulation element 12 has a reflectance equal to or higher than a reference value. The reference value here is a value based on the reflectance of a general mechanical diaphragm, and means that the reflectance of the diaphragm film 13 is higher than the reflectance of a general mechanical diaphragm. For example, the reflectance of the diaphragm 13 formed by depositing a resin material is 3%, which is higher than the reflectance of a general mechanical diaphragm. It is easy to reduce the reflectivity to less than 1% by applying a general satin process or the like in the mechanical aperture, but it is possible in the case of the mechanical aperture when the aperture film 13 is employed as in this embodiment. This is because it is extremely difficult to perform processing such as satin processing that suppresses the reflectivity to less than 1%. The material constituting the diaphragm film 13 is not limited to the black matrix material. However, in the present embodiment, it is assumed that the diaphragm film 13 having a higher reflectance than a general mechanical diaphragm is provided in the optical phase modulation element 12.

  For example, as shown in FIG. 3, the optical phase modulation element 12 provided with the diaphragm film 13 includes a holding member 14 a provided on the subject Ob side of the optical phase modulation element 12, and the imaging element 21 side of the optical phase modulation element 12. And is held in a state of being positioned in the optical path of the imaging optical system 11 by the holding member 14b provided on the imaging optical system 11. These holding members 14 a and 14 b hold the optical phase modulation element 12 provided with the diaphragm film 13 detachably with respect to the imaging optical system 11.

  Further, in the lens unit 10 of the present embodiment, for example, as shown in FIG. 3, a diaphragm is formed on the surface 12 b of the optical phase modulation element 12 (hereinafter referred to as “exit surface”) from the image sensor 21 side. A light shielding member 15 (an example of a light shielding unit) that shields stray light incident on the film 13 or stray light from the diaphragm film 13 toward the image sensor 21 is provided. The light shielding member 15 is disposed so as to be aligned with the holding member 14b disposed on the imaging element 21 side, for example, within the emission surface 12b of the optical phase modulation element 12. The light shielding member 15 is provided to suppress generation of a ghost image due to reflection on the diaphragm film 13. As the light shielding member 15, for example, a material obtained by performing black anodized satin processing on the surface of an aluminum material can be used effectively.

  The inventor of the present application examines what influence appears on the EDoF image when the diaphragm film 13 as described above is used instead of a general mechanical diaphragm as the diaphragm of the imaging optical system 11. The quality of the obtained EDoF image was evaluated and examined by photographing with the imaging device 100 having the configuration using the diaphragm 13 while changing the type of the film. As a result, it was found that a ghost image that was not confirmed by the configuration using the mechanical aperture might be reflected in the EDoF image, particularly when a glossy material, a light source, or the like was used as the subject Ob. Further, as a result of examination by the inventor of the present application, such a ghost image has a higher reflectance of the diaphragm film 13 than that of a general mechanical diaphragm, and therefore, when strong light is incident on the imaging optical system 11. It was found that the light reflected by the diaphragm film 13 is generated when the light enters the image sensor 21 as stray light.

  Based on such knowledge, in the lens unit 10 of the present embodiment, in order to effectively suppress generation of a ghost image due to reflection on the diaphragm film 13 and obtain a high-quality EDoF image, imaging is performed. The light blocking member 15 blocks the stray light that enters the diaphragm film 13 from the element 21 side or stray light that travels from the diaphragm film 13 to the image sensor 21.

  FIG. 4 is a diagram for explaining the principle that a ghost image is generated by reflection on the diaphragm film 13, and shows a state in which the optical path is tracked in the lens unit 10 having a configuration in which the light shielding member 15 is not provided. Here, for the purpose of explaining the principle, the lens 11a closer to the subject Ob and the lens 11b closer to the imaging element 21 than the optical phase modulation element 12 of the imaging optical system 11 are shown as single lenses.

  Light from the subject Ob sequentially passes through the lens 11 a, the optical phase modulation element 12, and the lens 11 b and forms an image on the image plane 21 a of the imaging element 21. At this time, part of the light from the subject Ob is reflected by the cover glass 21b of the image sensor 21, and the reflected lights r1 and r2 pass through the lens 11b and enter the optical phase modulation element 12. Here, since the aperture film 13 provided in the optical phase modulation element 12 has a high reflectance, a part of the reflected light from the imaging element 21 side is further reflected by the aperture film 13, and the reflected light r <b> 11 becomes the ghost light g. And reaches the image plane 21a of the image sensor 21. As a result, a ghost image is generated in the EDoF image generated using the image data output from the image sensor 21. Of the reflected light from the image sensor 21 side, the reflected light r22 reflected by the optically effective portion of the optical phase modulation element 12 has a lower reflectance than that of the diaphragm film 13 because the reflectance of the optically effective portion is lower. Even if it reaches the image plane 21a of the image sensor 21, it does not become a ghost image that degrades the quality of the EDoF image.

  FIG. 5 is a diagram for explaining the light shielding effect by the light shielding member 15 and shows a state in which the optical path in the lens unit 10 of the present embodiment provided with the light shielding member 15 is traced. In FIG. 5, as in FIG. 4, the lens 11 a on the subject Ob side and the lens 11 b on the imaging element 21 side of the optical phase modulation element 12 of the imaging optical system 11 are shown as single lenses.

  As shown in FIG. 5, by providing the light shielding member 15 on the image pickup element 21 side of the optical phase modulation element 12, the reflected light r <b> 1 reflected by the cover glass 21 b of the image pickup element 21 and the like toward the optical phase modulation element 12 is shielded. The member 15 can be shielded from light so as not to enter the diaphragm film 13. In other words, the reflected light (stray light) r1 incident on the diaphragm film 13 from the imaging element 21 side so as not to generate the reflected light r11 that is the ghost light g reaching the image plane 21a of the imaging element 21 in the example of FIG. Can be shielded by the light shielding member 15, and the generation of a ghost image can be effectively suppressed.

  Note that the ghost light g resulting from the reflection on the diaphragm 13 may form an image near the center of the image plane 21a of the image sensor 21 as shown in FIG. In the case where the light shielding member 15 is disposed at a position away from the optical phase modulation element 12 toward the image pickup element 21 in order to block the ghost light g formed near the center of the image plane 21a of the image pickup element 21, ghost light is used. There is a concern that not only g but also regular rays are shielded, and an intended image cannot be obtained. Therefore, it is desirable to arrange the light shielding member 15 at a position close to the emission surface 12 b of the optical phase modulation element 12. In the example of FIG. 3, since the light shielding member 15 is disposed on the emission surface 12 b of the optical phase modulation element 12, the diaphragm film provided on the optical phase modulation element 12 without blocking a regular light beam that is not the ghost light g. The ghost image resulting from the reflection at 13 can be effectively suppressed.

  The light shielding member 15 may be disposed at a position close to the emission surface 12b of the optical phase modulation element 12, and the light shielding member 15 is not necessarily provided on the emission surface 12b of the optical phase modulation element 12 as in the example of FIG. It is not necessary to arrange. Details of layout variations around the optical phase modulation element 12 in the lens unit 10 of the present embodiment will be described later.

  Here, a specific example of the imaging optical system 11 (hereinafter referred to as “depth of field expansion system”) configured to provide a desired depth of field expansion characteristic by providing the optical phase modulation element 12. The effect by providing the light shielding member 15 is demonstrated with an example, illustrating.

  6 is a diagram showing a specific example of lens characteristics of the depth-of-field expansion system, and FIG. 7 is an MD curve (40 lp / mm) when the depth-of-field expansion system having the lens characteristics shown in FIG. 6 is used. mm) in comparison with an MD curve in the case of using a normal imaging optical system in which the optical phase modulation element 12 is not provided. In FIG. 6, f represents the focal length of the depth of field expansion system, and Fno represents the F value of the depth of field expansion system. The MD curve in FIG. 7 is a coordinate system in which the MTF (Modulation Transfer Function) value, which is an evaluation value of the contrast of the image, is the vertical axis and the defocus amount is the horizontal axis, and the relationship between the defocus amount and the MTF value is curved. The defocus amount range in which a desired MTF value is obtained corresponds to the depth of field.

  In the example of FIG. 7, an MD curve of an image (after restoration) obtained using the depth-of-field expansion system having the lens characteristics shown in FIG. 6 is represented by a solid line, and the optical phase modulation element is obtained from this depth-of-field expansion system. An MD curve of an image obtained using a normal imaging optical system excluding 12 is represented by a broken line. When the two MD curves shown in FIG. 7 are compared, the depth of field is expanded by using the depth-of-field expansion system provided with the optical phase modulation element 12 as compared with the case of using a normal imaging optical system. You can see that.

  8 and 9 show an example of an EDoF image obtained when the lens unit 10 configured as a depth-of-field expansion system having the lens characteristics shown in FIG. FIG. 8 shows an image example when the light shielding member 15 is not provided, and FIG. 9 shows an image example when the light shielding member 15 is provided.

  When the above-described light shielding member 15 is not provided, light incident from the imaging element 21 side on the diaphragm film 13 provided on the optical phase modulation element 12 is reflected by the diaphragm film 13, and the reflected light is reflected on the imaging element 21. As shown in FIG. 8, a ghost image is generated in the EDoF image. G1, G2, and G3 in FIG. 8 are ghost images caused by reflection on the diaphragm film 13, respectively.

  On the other hand, when the light shielding member 15 is provided on the image pickup element 21 side of the optical phase modulation element 12, stray light incident on the diaphragm film 13 from the image pickup element 21 side or stray light traveling from the diaphragm film 13 toward the image pickup element 21 is generated. The light shielding member 15 shields it from light. As a result, as shown in FIG. 9, an EDoF image in which the ghost images G1, G2, and G3 confirmed in the image example of FIG. 8 are not reflected can be obtained. That is, stray light incident on the diaphragm film 13 from the imaging element 21 side or the diaphragm film 13 toward the imaging element 21, on the imaging element 21 side of the optical phase modulation element 12, or on the imaging element 21 side of the optical phase modulation element 12. By providing the light blocking member 15 that blocks stray light, it is possible to effectively suppress the generation of a ghost image due to the reflection on the diaphragm film 13.

  FIG. 10 is a diagram showing another specific example of the lens characteristics of the depth-of-field expansion system, and FIG. 11 is an MD curve (FIG. 10) when the depth-of-field expansion system having the lens characteristics shown in FIG. 40 lp / mm) is a diagram showing an MD curve in the case of using a normal imaging optical system in which the optical phase modulation element 12 is not provided. In FIG. 10, f represents the focal length of the depth of field expansion system, and Fno represents the F value of the depth of field expansion system. As in the example of FIG. 7, the MD curve in FIG. 11 is a coordinate system in which the MTF value, which is the contrast evaluation value of the image, is the vertical axis and the defocus amount is the horizontal axis. The relationship is expressed as a curve, and the range of the defocus amount in which a desired MTF value can be obtained corresponds to the depth of field.

  In the example of FIG. 11, the MD curve of the image (after restoration) obtained using the depth-of-field expansion system having the lens characteristics shown in FIG. An MD curve of an image obtained using a normal imaging optical system excluding 12 is represented by a broken line. When the two MD curves shown in FIG. 11 are compared, the depth of field is expanded by using the depth-of-field expansion system provided with the optical phase modulation element 12 as compared with the case of using a normal imaging optical system. You can see that.

  12 and 13 show an example of an EDoF image obtained when the lens unit 10 configured as a depth-of-field expansion system having the lens characteristics shown in FIG. 10 is used and photographing is performed using a light source as a subject. FIG. 12 shows an image example when the light shielding member 15 is not provided, and FIG. 13 shows an image example when the light shielding member 15 is provided.

  When the above-described light shielding member 15 is not provided, light incident from the imaging element 21 side on the diaphragm film 13 provided on the optical phase modulation element 12 is reflected by the diaphragm film 13, and the reflected light is reflected on the imaging element 21. As shown in FIG. 12, a ghost image is generated in the EDoF image. G4 and G5 in FIG. 12 are ghost images caused by reflection on the diaphragm film 13, respectively.

  On the other hand, when the light shielding member 15 is provided on the image pickup element 21 side of the optical phase modulation element 12, stray light incident on the diaphragm film 13 from the image pickup element 21 side or stray light traveling from the diaphragm film 13 toward the image pickup element 21 is generated. The light shielding member 15 shields it from light. As a result, as shown in FIG. 13, an EDoF image in which the ghost images G4 and G5 confirmed in the image example of FIG. 12 are not reflected can be obtained. That is, stray light incident on the diaphragm film 13 from the imaging element 21 side or the diaphragm film 13 toward the imaging element 21, on the imaging element 21 side of the optical phase modulation element 12, or on the imaging element 21 side of the optical phase modulation element 12. By providing the light blocking member 15 that blocks stray light, it is possible to effectively suppress the generation of a ghost image due to the reflection on the diaphragm film 13.

  As described above in detail with specific examples, the lens unit 10 of the present embodiment is based on the imaging element 21 side of the optical phase modulation element 12 provided with the diaphragm film 13 or the optical phase modulation element 12. In addition, a light shielding member 15 is provided on the image sensor 21 side, and the light shielding member 15 shields stray light that enters the diaphragm film 13 from the image sensor 21 side or stray light that travels from the diaphragm film 13 toward the image sensor 21. Therefore, generation of a ghost image due to reflection on the diaphragm 13 can be effectively suppressed, and a high-quality EDoF image in which no ghost image is reflected can be obtained.

  The layout around the optical phase modulation element 12 in the lens unit 10 of the present embodiment is not limited to the example shown in FIG. 3, and various variations are conceivable. Hereinafter, layout variations around the optical phase modulation element 12 will be described with reference to FIGS. 14 to 17. 14 to 17 are diagrams showing another example of the layout around the optical phase modulation element 12 in the lens unit 10 of the present embodiment.

  In the example illustrated in FIG. 3, the optical phase modulation element 12 provided with the diaphragm film 13 is held by holding members 14 a and 14 b provided on the subject Ob side and the imaging element 21 side of the optical phase modulation element 12, respectively. However, it is not limited to this. As shown in FIG. 14, the optical phase modulation element 12 provided with the diaphragm film 13 may be held by one of the holding member 14a on the subject Ob side and the holding member 14b on the imaging element 21 side. 14A shows a configuration in which the optical phase modulation element 12 is held by the holding member 14b on the imaging element 21 side, and FIG. 14B shows the configuration in which the optical phase modulation element 12 is held by the holding member 14a on the subject Ob side. The structure to be shown is shown.

  In the case of the configuration shown in FIG. 14, the optical phase modulation element 12 provided with the diaphragm film 13 is bonded to, for example, the holding member 14 a or the holding member 14 b and is held while being positioned in the optical path of the imaging optical system 11. Is done. 14B, in the case where the optical phase modulation element 12 is held by the holding member 14a on the subject Ob side, the emission surface of the optical phase modulation element 12 (the surface on the imaging element 21 side). In 12b, the light shielding member 15 is provided so as to cover the region where the holding member 14b is disposed. Even in the configuration illustrated in FIG. 14, stray light incident on the diaphragm film 13 from the image sensor 21 side or stray light traveling from the diaphragm film 13 toward the image sensor 21 can be shielded by the light shielding member 15. It is possible to effectively suppress the generation of a ghost image due to reflection at the surface.

  In the example illustrated in FIG. 3, the diaphragm film 13 is provided on the incident surface (surface on the subject Ob side) 12 a of the optical phase modulation element 12. However, the configuration is not limited thereto. As shown in FIG. 15, a diaphragm film 13 may be provided on the emission surface (image sensor 21 side surface) 12 b of the optical phase modulation element 12. FIG. 15A shows a configuration in which the optical phase modulation element 12 provided with the diaphragm film 13 on the emission surface 12b is held by the holding members 14a and 14b, and FIG. 15B shows the configuration of the diaphragm film 13 on the emission surface 12b. FIG. 15C shows a configuration in which the optical phase modulation element 12 provided with the aperture film 13 is held by the holding member 14a. The configuration is shown.

  In the case of the configuration shown in FIG. 15, the light shielding member 15 is provided so that the diaphragm film 13 provided on the emission surface 12 b of the optical phase modulation element 12 is not exposed. Even in the configuration illustrated in FIG. 15, stray light incident on the diaphragm film 13 from the imaging element 21 side or stray light traveling from the diaphragm film 13 toward the imaging element 21 can be shielded by the light shielding member 15, and thus the diaphragm film 13. It is possible to effectively suppress the generation of a ghost image due to reflection at the surface.

  In the example illustrated in FIG. 3, the light shielding member 15 is aligned with the holding member 14 b disposed on the imaging element 21 side in the surface of the emission surface (surface on the imaging element 21) 12 b of the optical phase modulation element 12. However, the present invention is not limited to this. As shown in FIG. 16, the light shielding member 15 may be arranged between the emission surface 12 b of the optical phase modulation element 12 and the holding member 14 b on the imaging element 21 side. FIG. 16A shows a configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the incident surface 12a is held by the holding members 14a and 14b, and the emission surface 12b of the optical phase modulation element 12 and the holding member 14b. FIG. 16B shows a configuration in which the light shielding member 15 is disposed between the optical phase modulation device 12 and the optical phase modulation device 12 in which the diaphragm film 13 is provided on the incident surface 12a. The structure which has arrange | positioned the light-shielding member 15 between the output surface 12b and the holding member 14b is shown. FIG. 16C shows the configuration in which the optical phase modulation element 12 having the diaphragm film 13 provided on the emission surface 12b is held by the holding members 14a and 14b, and the emission surface 12b and the holding member 14b of the optical phase modulation element 12. FIG. 16D shows an optical phase modulation in the configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the emission surface 12b is held by the holding member 14b. The structure which has arrange | positioned the light-shielding member 15 between the output surface 12b of the element 12 and the holding member 14b is shown.

  In the case of the configuration shown in FIG. 16, the light shielding member 15 has the same size as the diaphragm film 13 provided in the optical phase modulation element 12, and is disposed between the emission surface 12b of the optical phase modulation element 12 and the holding member 14b. Is done. Even in the configuration illustrated in FIG. 16, stray light incident on the diaphragm film 13 from the imaging element 21 side or stray light traveling from the diaphragm film 13 toward the imaging element 21 can be shielded by the light shielding member 15. It is possible to effectively suppress the generation of a ghost image due to reflection at the surface.

  In the example illustrated in FIG. 3, the light shielding member 15 is provided on the emission surface 12 b of the optical phase modulation element 12. However, the configuration is not limited thereto. As shown in FIG. 17, the light shielding member 15 may be arranged on the image pickup element 21 side further than the holding member 14 b on the image pickup element 21 side. FIG. 17A illustrates a configuration in which the optical phase modulation element 12 having the diaphragm film 13 provided on the incident surface 12a is held by the holding members 14a and 14b, and the light shielding member 15 is disposed closer to the imaging element 21 than the holding member 14b. FIG. 17B shows a configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the incident surface 12a is held by the holding member 14b. The light shielding member is closer to the image pickup element 21 than the holding member 14b. The structure which has arrange | positioned 15 is shown. In FIG. 17C, in the configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the emission surface 12b is held by the holding members 14a and 14b, the light shielding member 15 is located closer to the imaging element 21 than the holding member 14b. FIG. 17D shows a configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the emission surface 12b is held by the holding member 14b, and is closer to the imaging element 21 than the holding member 14b. The structure which has arrange | positioned the light-shielding member 15 is shown.

  In the case of the configuration shown in FIG. 17, the light shielding member 15 has the same size as the diaphragm film 13 provided in the optical phase modulation element 12 and is disposed closer to the imaging element 21 than the holding member 14 b. Even in the configuration illustrated in FIG. 17, stray light incident on the diaphragm film 13 from the imaging element 21 side or stray light traveling from the diaphragm film 13 toward the imaging element 21 can be shielded by the light shielding member 15. It is possible to effectively suppress the generation of a ghost image due to reflection at the surface.

  As described above, the layout variation around the optical phase modulation element 12 has been described, but various modifications can be considered in the configuration of the light shielding means. For example, the light shielding member 15 used as the light shielding means and the holding member 14b on the imaging element 21 side that holds the optical phase modulation element 12 are configured as one member, and the light shielding member 15 has a function as the holding member 14b. May be.

  FIG. 18 is a diagram illustrating an example in which the light shielding member 15 has a function as the holding member 14b. In the example of FIG. 18, the light shielding member 15 having a function as the holding member 14 b is illustrated as the light shielding member 16. FIG. 18A shows a configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the incident surface 12a is held by the holding member 14a and the light shielding member 16 on the subject Ob side, and FIG. 1 shows a configuration in which the optical phase modulation element 12 in which the diaphragm film 13 is provided on the incident surface 12a is held by the light shielding member 16 alone. FIG. 18C shows a configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the emission surface 12b is held by the holding member 14a and the light shielding member 16 on the subject Ob side. ) Shows a configuration in which the optical phase modulation element 12 having the aperture film 13 provided on the emission surface 12b is held only by the light shielding member 16.

  As in the example of FIG. 18, even when the optical phase modulation element 12 provided with the diaphragm film 13 is held by the light shielding member 16, stray light incident on the diaphragm film 13 from the imaging element 21 side, or Since stray light traveling from the diaphragm film 13 toward the image sensor 21 can be shielded by the light shielding member 16, generation of a ghost image due to reflection on the diaphragm film 13 can be effectively suppressed. In the case of the configuration shown in FIG. 18, since the light shielding member 16 has a function as a holding member, the cost can be reduced by reducing the number of parts and the number of assembly steps.

  In the embodiment described above, the light shielding member 15 provided on the imaging element 21 side of the optical phase modulation element 12 or the imaging element 21 side of the optical phase modulation element 12 is illustrated as an example of the light shielding unit. The means is not limited to this. For example, a roughened surface formed by roughening the exit surface (the surface on the imaging device 21 side) 12b of the optical phase modulation element 12 may be used as the light shielding means.

  FIG. 19 is a diagram illustrating an example in which a roughened surface 17 is formed on the emission surface 12 b of the optical phase modulation element 12 to form a light shielding unit. FIG. 19A shows a configuration in which the optical phase modulation element 12 with the roughened surface 17 formed on the output surface 12b is held by the holding members 14a and 14b, and FIG. 19B shows a rough shape on the output surface 12b. FIG. 19C shows a configuration in which the optical phase modulation element 12 on which the surface 17 is formed is held by the holding member 14b. FIG. 19C shows the optical phase modulation element 12 on which the roughened surface 17 is formed on the emission surface 12b. The structure hold | maintained is shown.

  In the case of the configuration shown in FIG. 19, when reflected light from the imaging element 21 side as indicated by r <b> 1 in FIG. 4 is incident on the roughened surface 17 formed on the emission surface 12 b of the optical phase modulation element 12, this reflected light is reflected. Is diffused by the roughened surface 17, the light intensity incident on the aperture film 13 becomes weak. As a result, even if the incident light is reflected by the diaphragm film 13 and the reflected light reaches the image plane 21a of the image sensor 21, it does not become a ghost image that impairs the image quality of the EDoF image. Even if the light diffused by the rough surface 17 formed on the emission surface 12 b of the optical phase modulation element 12 reaches the image surface 21 a of the image sensor 21, the light intensity is concentrated by the diffusion on the rough surface 17. Since the degree is weakened, even if an image is formed on the image surface 21a, the density thereof is low, and the ghost image does not deteriorate the image quality of the EDoF image.

  Accordingly, as shown in the example of FIG. 19, even if the roughened surface 17 is formed on the emission surface 12b of the optical phase modulation element 12 to form a light shielding means, a ghost image caused by reflection on the diaphragm film 13 is not generated. Generation can be effectively suppressed. Further, in the case of this configuration, it is not necessary to provide the light shielding member 15 separately, so that the cost can be reduced by reducing the number of parts and the number of assembly steps.

  Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments as they are, and various modifications and changes are made without departing from the scope of the invention in the implementation stage. Can be embodied. For example, in the above-described embodiment, the imaging apparatus 100 (see FIG. 1) having a configuration in which the lens unit 10 is detachable from the main body unit 20 including the imaging element 21 and the image processing apparatus 22 is illustrated. The configuration of the imaging device 100 is not limited to this. For example, a configuration in which the lens unit 10A including the imaging element 21 is detachable from the main body 20A including the image processing device 22 as in the imaging device 100A illustrated in FIG.

DESCRIPTION OF SYMBOLS 10 Lens unit 11 Imaging optical system 11a, 11b Lens 12 Optical phase modulation element 13 Aperture film 14a, 14b Holding member 15 Light-shielding member 16 Light-shielding member 17 Rough surface 20 Main body part 21 Imaging element 22 Image processing apparatus 100 Imaging apparatus

JP 2012-74861 A

Claims (9)

A lens unit disposed between a subject and an image sensor,
An imaging optical system including at least one lens for imaging light from the subject on the imaging device;
An optical phase modulation element that is arranged in the optical path of the imaging optical system and changes the phase of light passing through the imaging optical system;
A surface on the front SL imaging element side of the optical phase modulator, a diaphragm film having a reflectivity of narrowing the emitted light, or the reference value from the optical phase modulator,
A light shielding member that is provided on the diaphragm film so that the diaphragm film is not exposed to the imaging element side, and shields stray light that enters the diaphragm film from the imaging element side or stray light that travels from the diaphragm film to the imaging element. A lens unit comprising: The diaphragm membrane, a lens unit according to claim 1, characterized by comprising forming a black matrix material on the surface of the front SL imaging element side of the optical phase modulator. 2. The lens unit according to claim 1 , wherein the light shielding member is obtained by performing black alumite satin processing on a surface of an aluminum material. A holding member that is disposed on at least the imaging element side of the object side and the imaging element side of the optical phase modulation element and holds the optical phase modulation element;
The light shielding member is disposed on the diaphragm film provided on the surface of the optical phase modulation element on the image sensor side so as to be aligned with the holding member disposed on the image sensor side. The lens unit according to any one of claims 1 to 3 . A holding member that is disposed on at least the imaging element side of the object side and the imaging element side of the optical phase modulation element and holds the optical phase modulation element;
The light shielding member is disposed between the diaphragm film provided on the surface of the optical phase modulation element on the image sensor side and the holding member disposed on the image sensor side. The lens unit according to any one of claims 1 to 3 . A holding member that is disposed on at least the imaging element side of the object side and the imaging element side of the optical phase modulation element and holds the optical phase modulation element;
The light shielding member is disposed on the diaphragm film provided on the surface of the optical phase modulation element on the image sensor side through the holding member disposed on the image sensor side. The lens unit according to any one of claims 1 to 3 . The lens unit according to any one of claims 1 to 3 , wherein the light shielding member has a function as a holding member that holds the optical phase modulation element. An image sensor;
An imaging optical system including at least one lens for imaging light from a subject on the image sensor;
An optical phase modulation element that is arranged in the optical path of the imaging optical system and changes the phase of light passing through the imaging optical system;
A surface on the front SL imaging element side of the optical phase modulator, a diaphragm film having a reflectivity of narrowing the emitted light, or the reference value from the optical phase modulator,
A light shielding member that is provided on the diaphragm film so that the diaphragm film is not exposed to the imaging element side, and shields stray light that enters the diaphragm film from the imaging element side or stray light that travels from the diaphragm film to the imaging element. A lens unit comprising: An image sensor;
An imaging optical system including at least one lens for imaging light from a subject on the image sensor;
An optical phase modulation element that is arranged in the optical path of the imaging optical system and changes the phase of light passing through the imaging optical system;
A surface on the front SL imaging element side of the optical phase modulator, a diaphragm film having a reflectivity of narrowing the emitted light, or the reference value from the optical phase modulator,
A light shielding member that is provided on the diaphragm film so that the diaphragm film is not exposed to the imaging element side, and shields stray light that enters the diaphragm film from the imaging element side or stray light that travels from the diaphragm film to the imaging element. When,
An image processing unit that performs a restoration process for restoring the modulation by the optical phase modulation element on an image output from the imaging element to generate an image with an expanded depth of field. apparatus.