KR102252088B1 - Ultra-high speed retinal camera based on phase detection auto focusing - Google Patents

Abstract

The present invention relates to a phase detection auto-focusing (PDAF)-based ultra-high speed imaging fundus camera, which calculates a focus shift value at once by providing a fundus camera with a PDAF function, and moves a lens to a focus position immediately to accurately photograph a subject at an ultra-high speed. The phase detection auto-focusing (PDAF)-based ultra-high speed imaging fundus camera of the present invention comprises: a sensor module for receiving a reflected image from a subject to output phase detection data, and moving a lens forward and backward in accordance with lens movement data; and a control board for calculating a de-focus amount on the basis of the output phase detection data, correcting the de-focus amount using stored focal length correction data to generate focal length correction data, and converting the generated focal length correction data into an analog lens control value to control movement of the lens in the sensor module.

Description

Ultra-high speed retinal camera based on phase detection auto focusing}

The present invention relates to an ultra-high-speed imaging fundus camera based on phase detection autofocus, and in particular, by giving a phase detection auto focusing (PDAF) function to the fundus camera, a focus shift value is calculated at a time, and the focus position is immediately focused. The present invention relates to an ultra-high-speed fundus camera based on phase detection auto-focusing to accurately capture a subject at an ultra-high speed by moving a low lens.

For a fundus examination to check the nerve condition of the eye, usually intraocular structures through the pupil using a fundus camera after the injection of mydriatic fluid (a drug that is put in the eye to enlarge the pupil to make the fundus examination more accurate). With the image data taken, the retinal blood vessels, the nerve part of the eyeball, the color and thickness of the optic nerve, and the deformed state of the macula, the central part of the retina, are diagnosed.

Currently, since eye photography is attempted several times due to the problem that intraocular imaging is not accurately performed during a fundus examination using a fundus camera in an ophthalmology hospital, it takes a lot of time to take an eyeball. Therefore, for a better fundus examination, the examination is performed after the injection of the mydriatic solution as above, which causes a lot of inconvenience to the patient.

In addition, a general fundus camera uses a contrast AF technology (CDAF, Contrast Detection Auto Focusing) that continuously calculates the edge value of the image while moving the lens that focuses the image reflected from the subject. Since it takes a lot of time, there is a limit to shooting a subject at high speed.

Therefore, in order to improve the above problems, there is a need to develop an ultra-high-speed fundus camera capable of performing a fundus examination in Musan-dong while having a fast instantaneous capture time.

Techniques previously proposed for safety inspection are disclosed in <Patent Document 1> to <Patent Document 2>.

<Patent Literature 1> supplies light to an optical fiber or light emitting diode-based lighting device, a lighting device, but an illumination source provided with 1300 to 650 nm infrared rays and 650 to 400 nm visible light, and a 360° direction around the cornea. It can be adjusted up to, and implements a Musan-dong fundus camera with a control unit that cuts off the light supply or controls it to 180° or 30°, and a power supply that provides power to the lighting source. Through this configuration, by installing illumination on the pars plana and the sclera around the flat part in the human or animal eye, it does not cause pupil reflection and suppresses axial movement to a wide range of fundus. You can take pictures.

However, this method can also contribute to eye examination by photographing the fundus using Musan-dong, but it is difficult to instantly grasp whether the focus is in front/rear and the focal length without moving the lens. There is a limit to drastically shortening.

Republic of Korea Patent Registration No. 10-1855009 (Registered on April 27, 2018) (Musan-dong fundus camera to which the retinal contrast technique was applied through planar imaging)

Therefore, the present invention has been proposed to solve the problems occurring in the general CDAF type safety camera and the prior art as described above, and once a phase detection auto focusing (PDAF) function is provided to the fundus camera. An object of the present invention is to provide a high-speed fundus camera based on phase detection autofocus that calculates a focal shift value and moves the lens to the focus position immediately so that the subject can be accurately photographed at a high speed.

In order to achieve the above object, the "phase detection autofocus-based ultra-high speed fundus camera" according to the present invention,

A sensor module for receiving an image reflected from a subject, outputting phase detection data, and moving the lens forward/backward according to the lens movement data;

The amount of de-focus is calculated based on the phase detection data output from the sensor module, and the amount of de-focus is corrected using the stored focal length correction data to generate focal length correction data. And a control board for converting one focal length correction data into an analog lens control value to control the movement of the lens in the sensor module.

The sensor module may include a lens that focuses an image reflected from a subject and moves back and forth according to a lens control value; A CMOS image sensor (CIS) for distributing the image output from the lens and outputting a distance of the distributed image as phase detection data; And a lens driver for focusing by moving the lens in a forward or backward direction according to a lens control value output from the control board.

The control board includes a focal length correction data storage unit storing a correction reference value for correcting a focal length according to a phase difference; The amount of de-focus is calculated based on the phase detection data output from the sensor module, and the amount of de-focus is corrected by using the focal length correction data stored in the focal length correction data storage unit. And an image processor that generates distance correction data and converts the generated focal length correction data into an analog lens control value to control movement of a lens in the sensor module.

The image processor calculates a de-focus amount based on the phase detection data using a PDAF library function, and corrects the calculated de-focus amount using the focal length correction data to generate focal length correction data. It characterized in that it comprises an autofocus controller.

The image processor may include a digital/analog converter (DAC) for converting digital focal length correction data acquired through the autofocus controller into an analog focal length correction value.

The image process may include a motor control amount conversion module (Bit Shifter) that converts an analog focal length correction value output from the digital/analog converter into a motor control value and transmits it to a lens driver in the sensor module.

According to the present invention, a phase detection auto focusing (PDAF) function is provided to the fundus camera to calculate the focus shift value at a time, and by moving the lens directly to the focus position, it is possible to accurately capture the subject at high speed. There is an effect that can be.

In addition, by providing an ultra-high-speed safety camera based on the phase detection auto-focus according to the present invention, problems associated with the use of mydriatic solution can be improved, and treatment time in ophthalmology can be reduced by shortening the photographing time of the subject. It increases the number of patients and at the same time induces an effect that can satisfy market demands.

1 is an overall configuration diagram of a high-speed photographing fundus camera based on phase detection autofocus according to the present invention,
2 is a configuration diagram of a specific embodiment of a sensor module and an image processor for phase difference detection and focal length correction in the present invention;
3A and 3B are exemplary diagrams for detecting a phase difference in the CIS of the present invention;
4 is an explanatory diagram of a shield pixel for detecting a phase difference in CIS.

Hereinafter, with reference to the accompanying drawings, a phase detection autofocus-based ultra-high speed fundus camera according to a preferred embodiment of the present invention will be described in detail.

The terms or words used in the present invention described below should not be construed as being limited to a conventional or dictionary meaning, and the inventor should appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that it can be.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all the technical ideas of the present invention, and various equivalents and equivalents that can replace them at the time of the present application It should be understood that there may be variations.

1 is an overall configuration diagram of an ultra-high-speed fundus camera based on phase detection auto-focus according to a preferred embodiment of the present invention, and largely, an LED 110 providing a light source, a sensor module 120 and a control board 130 are shown. Includes.

The sensor module 120 receives an image reflected from a subject, outputs phase detection data, and moves the lens 122 forward/backward according to the lens movement data.

The sensor module 120 focuses the image reflected from the subject, distributes the lens 122 moving back and forth according to the lens control value, the image output from the lens 122, and phase detection of the distance of the distributed image. CIS (CMOS Image Sensor) 121 outputting (PD) data, a lens driver that focuses by moving the lens 122 in a forward or backward direction according to a lens control value output from the control board 130 123). Here, the lens driver 123 may be implemented on the control board 130.

The control board 130 calculates the amount of de-focus based on the phase detection data output from the sensor module 120, and corrects the amount of de-focus using the stored focal length correction data. The focal length correction data is generated, and the generated focal length correction data is converted into an analog lens control value to control the movement of the lens 122 in the sensor module 120.

This control board 130 is based on the focal length correction data storage unit 152 in which a correction reference value for correcting the focal length according to the phase difference is stored, and the phase detection data output from the sensor module 120, the de-focus (De -Focus) amount is calculated, the de-focus amount is corrected using the focal length correction data stored in the focal length correction data storage unit 152 to generate focal length correction data, and the generated focal length correction data is It includes an image processor 155 that converts into an analog lens control value and controls the movement of the lens 122 in the sensor module 120. Here, the image processor 155 also serves as a main processor that controls the entire operation of the fundus camera.

As shown in FIG. 2, the image processor 155 calculates a de-focus amount based on the phase detection data using a PDAF library function, and calculates the calculated de-focus using the focal length correction data. An autofocus controller 161 that corrects the amount to generate focal length correction data, and a digital/analog converter (DAC) that converts the digital focal length correction data acquired through the autofocus controller 161 into an analog focal length correction value (162), a motor control amount conversion module (Bit Shifter) 163 that converts the analog focal length correction value output from the digital/analog converter 162 into a motor control value and transmits it to the lens driver 123 in the sensor module. Includes.

In addition, the control board 130 includes an LED driver 151 for controlling the driving of the LED 110 under the control of the image processor 155, a charging unit 153 for charging the battery and displaying the remaining battery level, and a stored photo. And USB 156, which is a removable disk for image verification, SD 157 for storing video recording and safety photo capture files, a key controller 159 for inputting a function and operation control signal according to an external key input, and safety capture. It may further include an LCD 154 that displays the poems or stored images and pictures when reproducing them.

Here, the LED driver 151, the charging unit 153, the USB 156, the SD 157, the key controller 159, the LCD 154, etc. are a general configuration provided in the existing fundus camera, and the functions are also the same. Description will be omitted.

The operation of the ultrahigh-speed photographing fundus camera based on the phase detection autofocus according to a preferred embodiment of the present invention configured as described above will be described in detail as follows.

First, when photographing the eyes of a subject for examination, the lens 122 of the sensor module 120 focuses the image reflected from the subject, and the CIS 121 distributes and distributes the image output from the lens 122 The distance of the image is output as phase detection data (PD data).

As shown in FIG. 3A, the CIS 121 includes a micro lens that separates an image output from the lens 122, and an AF sensor capable of detecting a phase difference of an image separated from the micro lens is built-in. . 3B is an example of detecting a phase difference by the AF sensor.

If you zoom in on a general CMOS image sensor, 2 G pixels, 1 R pixel, and 1 B pixel are arranged like a checkerboard as a set.

At this time, PDAF cuts adjacent G Pixels by ½ and uses them for phase difference detection. Phase detection measures the spacing between two phases using a pair of adjacent pixels.

The phase difference between the left and the right is measured through images incident on each of the left and right through the micro lens.

In the AF sensor, as shown in FIG. 4, some half-metal shielding pixels, referred to as shield pixels, are incorporated as normal pixels. There are two types of shielding pixels, right shielding pixels and left shielding pixels, and the phase information of these left and right shields enables phase detection autofocus (PDAF) for high-speed AF by an external ISP.

Shield pixels are located inside the Active Pixel Area (99% block occupancy). In the block filled 16 × 32 pixels, 8 right shield pixels and 8 left shield pixels are distributed and embedded.

When the phase detection data (PD data) is transmitted from the sensor module 120 in the same manner as described above, the image processor 155 of the control board 130 determines the amount of de-focus based on the phase detection data. The calculated and stored focal length correction data is used to correct the de-focus amount to generate focal length correction data, and the generated focal length correction data is converted into an analog lens control value, and the lens in the sensor module 120 ( 122) to quickly control the movement.

That is, the image processor 155 calculates a de-focus amount based on the phase detection data using the PDAF library function in the autofocus controller 161 as shown in FIG. 2. Here, the amount of de-focus is extracted using the PD Sensor (AF sensor) attached to the sensor, and the phase detection data is determined by the PD sensor provided by the sensor company.

Thereafter, the autofocus controller 161 corrects the calculated amount of defocus by using the focal length correction data stored in the focal length correction data storage unit 152 within the PDAF library function to generate focal length correction data.

Here, the focal length correction data stored in the focal length correction data storage unit 152 is, even though a value for the phase difference is obtained, the amount of movement that needs to be moved to correct the phase difference is different for each camera, according to the amount of the phase difference. It means a correction reference amount for correcting the phase difference.

Therefore, it is expressed as the de-focus amount finally obtained = standard phase difference displacement value +/- focal length correction data.

Here, the standard phase difference displacement value is a constant value determined by a standard rather than a different value for each camera, exists in the form of a table, and refers to a standard value for each phase difference correction according to an arbitrary lens position.

Thereafter, the digital/analog converter 12 converts the digital focal length correction data acquired through the autofocus controller 161 into an analog focal length correction value and transmits it to the motor control amount conversion module 163.

The motor control amount conversion module 163 converts the analog focal length correction value transmitted from the digital/analog converter 162 into a motor control value and transmits it to the lens driver 123 in the sensor module 120. A predetermined table may be used to convert the focal length correction value into a motor control value. That is, the focal length correction value becomes an index, and the motor control value is extracted from the data mapped to this index.

The lens driver 123 in the sensor module 120 quickly focuses by moving the lens 122 in a forward or backward direction according to a lens control value output from the control board 130.

After the lens 122 is moved, the control board 130 detects the phase difference again and checks whether the phase difference value falls within a predetermined error range. As a result of this check, if the phase difference value falls within the specified error range, it is determined that the AF operation is complete. On the contrary, when the phase difference value exceeds the specified error range, it is determined that an error has occurred, and the de-focus correction process is repeated Carry out.

An example of the phase difference detection and focal length correction process described above is as follows.

Phase difference: 10 pulses in the Far direction, depth of focus lens: 5um, 1Pulse lens movement distance: 3um, and focal length correction data (Calibration Data): 1Pulse correction in the near direction, the method for phase difference correction is as follows.

Determine the direction for correction. It is decided in the Far direction among the Far/Near directions.

Determine the amount of lens shift. Check if the phase difference value is greater than the amount of the lens depth of focus. In the case of the above example, since the movement amount of the phase difference 10 pulse is 3um * 10Pluse = 30um, it must be moved larger than the depth.

Then, the amount of movement is calculated. Since the standard phase difference is 10 pulses in the Far direction, the calibration value becomes 1 pulse in the Near direction. Therefore, since the final focal length correction value becomes the standard phase difference displacement value +/- focal length correction value, it is determined as Far 10 Pulse-Near 1 Pulse = Far 9 Pulse.

Therefore, by using a motor to move 9 pulses in the Far direction, the lens 122 is moved to compensate for the focal length error.

As described above, the present invention provides a phase detection auto focusing (PDAF) function to the fundus camera, calculates the focus shift value at a time, and allows the lens to be moved to the focus position immediately. Since photographing can be accurately performed, it is possible to provide a fundus camera optimized for an ophthalmic eye examination.

Although the invention made by the present inventor has been described in detail according to the above embodiment, the present invention is not limited to the above embodiment, and it is common knowledge in the art that various changes can be made without departing from the gist of the invention. It is self-evident to those who have.

110: LED
120: sensor module
121: CIS
122: lens
123: lens driver
130: control board
151: LED driver
152: focal length correction data storage unit
153: live part
155: image processor
161: autofocus controller
162: digital/analog converter
163: motor control amount conversion module

Claims (6)

As a fundus camera for photographing an inspection target by correcting the focal length based on phase detection autofocus (PDAF),
A sensor module for receiving an image reflected from a subject, outputting phase detection data, and moving the lens forward/backward according to the lens movement data; And
The amount of de-focus is calculated based on the phase detection data output from the sensor module, and the amount of de-focus is corrected using the stored focal length correction data to generate focal length correction data. A control board for converting one focal length correction data into an analog lens control value to control the movement of the lens in the sensor module,
The sensor module includes a CMOS Image Sensor (CIS) that distributes an image output from the lens and outputs a distance of the distributed image as phase detection data,
The CIS includes a micro lens that separates an image output from the lens, and an AF sensor capable of detecting a phase difference of an image separated from the micro lens is built in
The left/right phase difference is measured through images incident on each of the left and right through the microlens, and the AF sensor has some half metal shielding pixels called shield pixels, and the shielding pixels are the right shielding pixels and the left It is implemented with two types of shielding pixels called shielding pixels, and outputs phase detection data by implementing phase detection autofocus (PDAF) for high-speed AF using the phase information of the left and right shields.
The control board calculates a de-focus amount based on the phase detection data using a PDAF library function, and corrects the calculated de-focus amount using the focal length correction data to generate focal length correction data. A fundus camera for high-speed photography based on phase detection auto-focus, characterized in that it comprises an auto-focus controller.
The sensor module of claim 1, wherein the sensor module comprises: a lens that focuses an image reflected from a subject and moves back and forth according to a lens control value; And a lens driver that focuses by moving the lens in a forward or backward direction according to a lens control value output from the control board.
The control board of claim 1, wherein the control board comprises: a focal length correction data storage unit storing a correction reference value for correcting a focal length according to a phase difference; The amount of de-focus is calculated based on the phase detection data output from the sensor module, and the amount of de-focus is corrected using the focal length correction data stored in the focal length correction data storage unit. An image processor that generates distance correction data and converts the generated focal length correction data into an analog lens control value to control the movement of the lens in the sensor module. .
delete The method of claim 3, wherein the image processor comprises a digital/analog converter (DAC) for converting digital focal length correction data acquired through the autofocus controller into an analog focal length correction value. High-speed fundus camera.
The method of claim 5, wherein the image processor comprises a motor control amount conversion module (Bit Shifter) for converting an analog focal length correction value output from the digital/analog converter into a motor control value and transmitting it to a lens driver in the sensor module. An ultra-high-speed fundus camera based on phase detection and autofocus.

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