WO2021012683A1

WO2021012683A1 - Imaging system

Info

Publication number: WO2021012683A1
Application number: PCT/CN2020/078353
Authority: WO
Inventors: 王仲益; 林郁轩; 郑铭媛; 黄景煜
Original assignee: 神亚科技股份有限公司
Priority date: 2019-07-22
Filing date: 2020-03-09
Publication date: 2021-01-28
Also published as: TWI742555B; CN212112013U; TW202109137A; CN111208651A

Abstract

Provided is an imaging system, comprising a light-transmitting cover plate, an image sensor and a diffractive optical element, wherein the image sensor is arranged below the light-transmitting cover plate; and the diffractive optical element is arranged between the light-transmitting cover plate and the image sensor. After penetrating through the light-transmitting cover plate, light from an object to be measured is diffracted by the diffractive optical element so as to be imaged on the image sensor.

Description

Imaging system

Technical field

The present invention relates to an optical system, and in particular to an imaging system.

Background technique

With the popularization of electronic devices and the diversification of functions, imaging systems are integrated into electronic devices to capture required images for the electronic devices to provide various functions. One of the applications is to use an imaging system to collect fingerprint images on the surface of the finger.

The current imaging system includes a lens, so that the object to be sensed can be imaged on the image sensor through the lens, so an image sensor smaller in size than the object to be sensed can be used to obtain images. However, the use of lenses will increase the thickness of the overall mechanism, which is not conducive to the thinning of portable electronic devices.

Summary of the invention

The invention is directed to an imaging system that can reduce the configuration area of the image sensor and can maintain a thinner thickness.

An embodiment of the present invention provides an imaging system including a light-transmitting cover, an image sensor, and a diffractive optical element (DOE). The image sensor is disposed under the transparent cover. The diffractive optical element is arranged between the transparent cover plate and the image sensor. Wherein, the light from the object to be measured is diffracted by the diffractive optical element after penetrating the light-transmitting cover, and then imaged on the image sensor.

In the imaging system of the embodiment of the present invention, the diffractive optical element is arranged between the transparent cover plate and the image sensor to image the light from the object to be measured on the image sensor. Therefore, the disposition area of the image sensor can be reduced, and the thickness can be kept thin.

Description of the drawings

The accompanying drawings are included to further understand the present invention, and the accompanying drawings are incorporated into this specification and constitute a part of this specification. The drawings illustrate embodiments of the present invention, and together with the description serve to explain the principles of the present invention.

FIG. 1 is a schematic cross-sectional view of an imaging system according to an embodiment of the present invention;

2 is a schematic cross-sectional view of an imaging system according to another embodiment of the invention.

Attached icon number description

100, 200: imaging system;

110: Transparent cover plate;

110a: inner surface;

110b: outer surface;

120: image sensor;

120a: sensing surface;

130: diffractive optical element;

140: display device;

H1, H2: spacing;

L, L’: light;

P: finger;

S: sensing area;

W1, W2: width.

Detailed ways

Reference will now be made in detail to the exemplary embodiments of the present invention, and examples of the exemplary embodiments are illustrated in the accompanying drawings. Whenever possible, the same component symbols are used in the drawings and descriptions to indicate the same or similar parts.

FIG. 1 is a schematic cross-sectional view of an imaging system 100 according to an embodiment of the invention. The imaging system 100 of this embodiment may be a separate imaging system or an imaging system integrated with an electronic device, such as a mobile phone, a tablet computer, a notebook computer, a digital photography device, or other appropriate electronic devices. Please refer to FIG. 1, the imaging system 100 of this embodiment includes a transparent cover 110, an image sensor 120 and a diffractive optical element 130. The image sensor 120 is disposed under the transparent cover 110. The diffractive optical element 130 is disposed between the transparent cover 110 and the image sensor 120. In this embodiment, the light-transmitting cover 110 may be a glass cover or other light-transmitting material cover to protect the image sensor 120 or the electronic device. The image sensor 120 is, for example, a complementary metal oxide semiconductor (CMOS) sensor or a charge coupled device (CCD), and the invention is not limited thereto. The diffractive optical element 130 is configured to diffract incident light.

In this embodiment, the diffractive optical element 130 is configured so that the light L reflected by the object to be measured (not shown) located on the side of the transparent cover plate away from the image sensor 120, after penetrating the transparent cover plate 110, It can be diffracted by the diffractive optical element 130 to be imaged on the image sensor 120. In this embodiment, the diffractive optical element 130 may be configured to converge the diffracted light so that the object to be measured forms a reduced image on the image sensor 120. Therefore, the size of the image sensor 120 can be reduced, the production cost can be reduced, the device space can be saved, and the volume of the overall electronic device can be reduced.

In some embodiments, the diffractive optical element 130 is a diffraction grating, such as a transmission grating. In other embodiments, the diffractive optical element 130 has at least one slit or pinhole. For example, the diffractive optical element 130 may include an optical layer provided with one or more slits, or may include a pinhole (or may Or, the diffractive optical element 130 has a stepped surface structure. For example, the diffractive optical element 130 may have a surface that changes intermittently (stepwise), wherein the stepped surface structure The interval and periodic structure are specially designed so that the light diffracted by the diffractive optical element 130 can form an image on the image sensor 120.

In an embodiment, the imaging system 100 may be configured to transmit the reflected light from the object to be measured directly to the diffractive optical element 130 after penetrating the transparent cover 110, and the light emitted from the diffractive optical element 130 is directly transmitted To the image sensor 120. Herein, "direct transfer" means that from one optical element to another optical element, only gas (for example: air) or other environmental media can exist in the space in between. In this embodiment, no additional lens element is required between the transparent cover 110 and the image sensor 120, so the imaging system can be kept thinner.

In an embodiment, the structure of the diffractive optical element 130 may be designed to cause destructive interference of light in a specific wavelength band. For example, the structure of the diffractive optical element 130 can be designed such that the reflected light from the infrared light band of the object to be measured produces destructive interference, so that the diffractive optical element 130 also has the function of filtering to filter out the reflected light in the infrared light band. . When the imaging system 100 needs to sense the visible light band or other non-infrared light bands, the image quality can be improved by filtering out the light in the infrared light band. In some embodiments, if the imaging system 100 intends to sense images in other wavelength bands, the structure of the diffractive optical element 130 can also be designed to filter light in the non-sensing wavelength band.

In addition, in another embodiment, the diffractive optical element 130 may be disposed on the inner surface 110 a of the transparent cover 110 facing the image sensor 120. For example, the diffractive optical element 130 can be directly disposed or attached to the inner surface 110a of the transparent cover 110.

Please refer to Figure 1 again. The transparent cover 110 has an outer surface 110 b away from the image sensor 120. The image sensor 120 has a sensing surface 120 a facing the transparent cover 110. In this embodiment, the ratio of the distance H1 from the outer surface 110b of the transparent cover 110 to the diffractive optical element 130 to the distance H2 from the diffractive optical element 130 to the sensing surface 120a falls within the range of 1 to 5. In addition, in this embodiment, the ratio of the width W1 of the diffractive optical element 130 to the width W2 of the image sensor 120 is greater than or equal to 1.2.

2 is a schematic cross-sectional view of an imaging system 200 according to another embodiment of the invention. Please refer to FIG. 2, the imaging system 200 of this embodiment is similar to the imaging system 100 of FIG. 1, and the main differences between the two are as follows. In this embodiment, the image sensor 120 and the diffractive optical element 130 in the imaging system 200 can form a fingerprint sensing module, such as an on-screen fingerprint sensing (OFS) module. The image sensor 120 is disposed under the transparent cover 110. The diffractive optical element 130 is disposed between the transparent cover 110 and the image sensor 120. The object to be measured may be a finger P, the light-transmitting cover 110 can be placed on the finger P, and the diffractive optical element 130 is used to image the fingerprint of the finger P on the light-transmitting cover 110 on the image sensor 120 to obtain Fingerprint image. In an embodiment, the imaging system 200 may have a sensing area S, and the diffractive optical element 130 and the image sensor 120 are disposed in the sensing area S.

In this embodiment, the imaging system 200 may further include a display device 140. The display device 140 is disposed between the transparent cover 110 and the image sensor 120. The display device 140 is, for example, a transparent display panel such as an organic light-emitting device (OLED) display panel, a liquid crystal display panel, or other transparent display panels. However, in other embodiments, the display device 140 may also be a liquid crystal display panel or other appropriate display panel, and the area above the image sensor 120 has a light-transmitting opening. At least a part of the light L'emitted by the display device 140 can be reflected by the finger P on the light-transmitting cover 110 and penetrate the display device 140, and then diffracted by the diffractive optical element 130 to be imaged on the image sensor 120. In some embodiments, the display device 140 may display an image in the sensing area S for the user to touch operation.

To sum up, in the imaging system of the embodiment of the present invention, the diffractive optical element is disposed between the transparent cover plate and the image sensor to image the reflected light from the object to be measured on the image sensor. Therefore, the configuration area of the image sensor can be reduced, and the imaging system can be kept thinner. In addition, the diffractive optical element can also filter the light in the non-sensing band, providing a better sensing effect.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand: It is still possible to modify the technical solutions described in the foregoing embodiments, or equivalently replace some or all of the technical features; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention range.

Claims

An imaging system is characterized in that it comprises:

Transparent cover;

The image sensor is arranged under the transparent cover plate; and

The diffractive optical element is arranged between the transparent cover plate and the image sensor;

Wherein, the light from the object to be measured is diffracted by the diffractive optical element after penetrating the light-transmitting cover plate and then imaged on the image sensor.
The imaging system of claim 1, wherein the diffractive optical element is a diffraction grating.
The imaging system of claim 1, wherein the light from the object to be measured is directly transmitted to the diffractive optical element after penetrating the light-transmitting cover plate, and the light emitted from the diffractive optical element The light is directly transmitted to the image sensor.
The imaging system according to claim 1, wherein the diffractive optical element filters out the infrared light band of the reflected light.
The imaging system according to claim 1, wherein the diffractive optical element is arranged on the inner surface of the light-transmitting cover plate facing the image sensor.
The imaging system of claim 1, wherein the transparent cover has an outer surface away from the image sensor, and the image sensor has a sensing surface facing the transparent cover, wherein the The ratio of the distance from the outer surface to the diffractive optical element to the distance from the diffractive optical element to the sensing surface falls within the range of 1 to 5.
4. The imaging system of claim 1, wherein the ratio of the width of the diffractive optical element to the width of the image sensor is greater than or equal to 1.2.
The imaging system of claim 1, wherein the image sensor and the diffractive optical element form a fingerprint sensing module, the object to be measured is a finger, and the light-transmitting cover plate is used to allow the finger Placed on it, the diffractive optical element is used to image the fingerprint of the finger placed on the light-transmitting cover on the image sensor.
The imaging system of claim 1, wherein the imaging system further comprises a display device, and the display device is disposed between the light-transmitting cover plate and the image sensor.
The imaging system of claim 1, wherein the diffractive optical element has at least one slit or pinhole, or has a stepped surface structure.