JP5635342B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

Conventionally, an imaging apparatus using a light field photography technique is known (see, for example, Patent Document 1).
In this imaging apparatus, the imaging element is arranged so as to be movable in the optical axis direction with respect to a microlens array fixed on the focal plane of the imaging lens between the imaging lens and the imaging element. Spatial resolution can be improved by bringing the imaging device close to the microlens array, and the amount of angle information of the light can be increased by separating the imaging device from the microlens array.

US Patent Application Publication No. 2010/0026852

  However, in the imaging apparatus of Patent Document 1, the spatial resolution and the amount of angle information are in a trade-off relationship, and when the imaging element is brought close to the microlens array in order to improve the spatial resolution, the angle information amount is decreased. In addition, if the image sensor is separated from the microlens array in order to increase the amount of angle information, there is a disadvantage that the spatial resolution is lowered.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an imaging apparatus capable of improving the spatial resolution while maintaining the amount of light angle information.

In order to achieve the above object, the present invention provides the following means.
The present invention relates to an imaging lens that images light from an object, a microlens array that includes a plurality of microlenses arranged on the imaging surface of the imaging lens in a direction intersecting the optical axis, and the microlens array. An imaging device disposed at a position opposite to the imaging lens across the lens array and spaced in the optical axis direction, and the microlens array for the imaging lens and the imaging device. A microlens moving mechanism that relatively moves in the arrangement direction, and the microlens array includes a plurality of microlenses arranged at a predetermined arrangement pitch, and the microlens movement mechanism moves the shorter than the arrangement pitch. The microlens array is moved by a distance, and the movement of the microlens array by the microlens moving mechanism is a periodic vibration. Imaging device, the images acquired every time the micro-lens array is moved, to provide an imaging apparatus you satisfy the following condition.
Y = N × X
Here, X is a vibration period of the microlens array, Y is an image acquisition period by the image sensor, N is the number of times of photographing per period, and is an integer of 4 or more.

  According to the present invention, the light from the object condensed by the imaging lens is imaged at the position of the microlens array, and then passes through the microlens array and is disposed at the subsequent position. Taken by Thereby, not only the position information of the object but also the angle information of the light from the object can be acquired by the image sensor. Then, the microlens array is moved in the arrangement direction by the microlens moving mechanism, and the images are taken at different positions, so that the distance in the optical axis direction between the microlens array and the imaging element is maintained and acquired by the imaging element. Spatial resolution can be improved while maintaining the amount of angle information that is performed.

The microlens array is formed by arranging a plurality of microlenses at a predetermined arrangement pitch, and the microlens array is moved by a movement distance shorter than the arrangement pitch by the microlens moving mechanism. Since an image is acquired every time, imaging can be performed by pseudo-reducing the arrangement pitch of the microlenses arranged at a predetermined arrangement pitch, and the spatial resolution can be easily improved.

Furthermore, since the movement of the microlens array by the microlens moving mechanism is a periodic vibration and satisfies the above conditional expression, the microlens array and the image sensor return to the same positional relationship every N times of image acquisition. That is, since the sampling characteristic indicating the relationship between the position information and the angle information returns to the same sampling characteristic every N times of image acquisition, the processing can be easily performed at the time of subsequent image construction.

In the above invention, a light-shielding portion that blocks passage of light from the imaging lens may be provided on the outer peripheral portion of each microlens constituting the microlens array.
By doing so, the light that passes through each microlens obliquely with respect to the optical axis is prevented from entering the pixel group of the image sensor corresponding to the adjacent microlens, and the S / N ratio is improved. Can do.

Moreover, in the said invention, you may provide the point light source fixed to the said micro lens array and generating illumination light toward the said image pick-up element.
By doing in this way, the illumination light emitted from a point light source can be detected with an image pick-up element, and the position of the micro lens array with respect to an image pick-up element can be detected accurately.

  According to the present invention, it is possible to improve the spatial resolution while maintaining the angle information amount of the light beam.

1 is a schematic overall configuration diagram illustrating an imaging apparatus according to an embodiment of the present invention. It is a figure explaining the operation | movement of the microlens array in the imaging device of FIG. It is a figure which shows the sampling characteristic of the image acquired in the state which fixed the micro lens array in the imaging device of FIG. It is a figure which shows the sampling characteristic similar to FIG. It is a figure which shows the sampling characteristic of the image acquired in the state which moved the micro lens array in the imaging device of FIG. It is a figure which shows the modification of operation | movement of the micro lens array in the imaging device of FIG. It is a figure which shows the other modification of operation | movement of the micro lens array in the imaging device of FIG. It is a figure which respectively shows (a) an example of a light shielding film arrange | positioned at the periphery of the micro lens in the imaging device of FIG. 1, and (b) the microlens array which attached | subjected the light shielding film. It is a figure which shows LED attached to the micro lens array in the imaging device of FIG.

An imaging apparatus 1 according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the imaging apparatus 1 according to the present embodiment includes an imaging lens 2 that forms an image of light from a subject A, and a microlens array 3 that is disposed on a focal plane of the imaging lens 2. An image pickup device 4 disposed on the opposite side to the imaging lens 2 with the microlens array 3 interposed therebetween, spaced apart in the optical axis direction, a microlens moving mechanism 5 for moving the microlens array 3, and an image pickup device 4 includes an image processing unit 6 that processes the image signal acquired by 4 to generate image data, and a control unit 7 that controls the image sensor 4, the microlens moving mechanism 5, and the image processing unit 6.

As shown in FIG. 2, the microlens array 3 includes a plurality of microlenses 3 a that are two-dimensionally squarely arranged at a predetermined arrangement pitch d along the focal plane of the imaging lens 2.
The image pickup device 4 is, for example, a CCD having a plurality of pixels 4 a that are two-dimensionally squarely arranged, and is arranged at a parallel interval with respect to the microlens array 3.

The microlens moving mechanism 5 is configured to move the entire microlens array 3 in the arrangement direction of the microlenses 3a, that is, the direction orthogonal to the optical axis.
More specifically, as shown in FIG. 2, the microlens moving mechanism 5 draws a square trajectory Q1 having one side of a length d / 2 that is half the arrangement pitch d of the microlenses 3a. The whole 3 is moved by periodic vibration.

Here, the period of the periodic vibration by the microlens moving mechanism 5 is X (Hz), the imaging period by the image sensor 4 is Y (Hz), and the number of imaging per period is N (times).
Y = N × X (1)
Is set such that the conditional expression is satisfied.

The operation of the imaging apparatus 1 according to the present embodiment configured as described above will be described below.
In order to acquire an image of the subject A using the imaging apparatus 1 according to the present embodiment, the light from the subject A is imaged by the imaging lens 2 and variously formed on the microlens array 3 arranged on the imaging surface. Incident from an angle.

  Light from the subject A that has entered the microlens array 3 at various angles is separated by the individual microlenses 3 a and projected onto the image sensor 4. As a result, not only the position information of each part of the subject A but also the angle information of the light from the subject A is acquired by the image sensor 4.

  That is, the light imaged by each pixel 4a of the image sensor 4 is light from a predetermined position of the subject A and is acquired as light incident on the pixel 4a at a predetermined angle. Thereby, as shown in FIG. 3, it is possible to obtain a sampling characteristic in which each pixel 4a is arranged with angle information and position information as coordinate axes.

  As a result, in the image processing unit 6, among the sampling characteristics described above, the process of selecting only the pixels 4a that photograph the incident light at the same angle so as to be surrounded by the chain line R1 in FIG. By performing each for a plurality of different angles, a plurality of images of the same subject A viewed from different angles can be obtained.

  Further, in the above sampling characteristics, it is possible to obtain an image in which only one point is in focus by performing a process of composing an image by selecting only the pixels 4a that are photographed at the same position so as to be surrounded by the chain line R2 in FIG. it can. Further, as shown in FIG. 4, as shown by the chain lines R <b> 3 and R <b> 4, by selecting a pixel 4 a whose angle and position are shifted little by little and forming an image, a plurality of processes with different shifting directions are performed to focus on different positions. Can be obtained.

  In this case, according to the imaging device 1 according to the present embodiment, since the entire microlens array 3 is moved in the arrangement direction of the microlenses 3a by the operation of the microlens moving mechanism 5, as shown in FIG. An image having position and angle information can also be acquired for light from the subject A (regions A2 to A4) incident between the microlenses 3a other than the region A1 acquired with the lens 3a fixed. The sampling characteristics obtained as a result are as shown in FIG.

  That is, the microlens array 3 is moved by periodic vibration while drawing a square locus having one side of a length d / 2 that is half the arrangement pitch d of the microlenses 3a. The arrangement pitch d of the lenses 3a can be artificially shortened to d / 2, so that there is an advantage that an image with high spatial resolution can be easily obtained.

  In this embodiment, since the microlens array 3 is moved by periodic vibration that satisfies the conditional expression (1), the microlens array 3 and the image sensor 4 are in the same positional relationship every N times of image acquisition. Can be returned. That is, since the sampling characteristic indicating the relationship between the position information and the angle information returns to the same sampling characteristic every N times of image acquisition, the processing can be easily performed at the time of subsequent image construction.

  In the example shown in FIG. 2, the microlens array 3 is moved while drawing a square locus Q1, but instead, the microlens array 3 is moved while drawing a crank-like locus Q2, as shown in FIG. Alternatively, as shown in FIG. 7, a circular locus Q3 may be drawn and moved. By moving in a crank shape, the spatial resolution can be further improved by increasing the number of times of photographing per cycle compared to the case of moving in a square shape. Further, by drawing and moving the circular locus Q3, it is possible to perform photographing while moving the microlens array 3 at a constant speed, and the microlens moving mechanism 5 can be simplified.

  In the present embodiment, as shown in FIG. 8, the periphery of each microlens 3 a may be covered with a light shielding film 8. In FIG. 2, the microlens 3 a is exposed from the light shielding film 8 with a circular opening having a diameter a.

  As a result, the light that has passed through one microlens 3a is not mixed with the light that has passed through the adjacent microlens 3a, or is unexpectedly reflected or refracted near the boundary of each microlens 3a to become stray light Can be shielded. As a result, the S / N ratio of the acquired image can be improved.

  In the present embodiment, an LED (light source) 9 that is fixed to the microlens array 3 and irradiates illumination light toward the image sensor 4 may be disposed in a part of the microlens array 3. By doing so, the position of the microlens array 3 can be detected with high accuracy from the image of the LED 9 acquired by the imaging device 4, and the angle information and position information of the light from the subject A can be obtained more accurately. There is an advantage.

  In the example shown in FIG. 9, the LEDs 9 are arranged in place of the microlenses 3a at the four corners of the microlens array 3, but the positions are not limited and may be arranged between the microlenses 3a.

A Subject (object)
d Arrangement pitch 1 Imaging device 2 Imaging lens 3 Micro lens array 3a Micro lens 4 Imaging element 5 Micro lens moving mechanism 8 Light shielding film (light shielding portion)
9 Light source

Claims (3)

An imaging lens for imaging light from the object;
A microlens array comprising a plurality of microlenses arranged in a direction intersecting the optical axis on the imaging surface of the imaging lens;
An imaging device disposed at a position opposite to the imaging lens across the microlens array and spaced in the optical axis direction;
A microlens moving mechanism for moving the microlens array relative to the imaging lens and the image sensor in the arrangement direction ;
The microlens array is formed by arranging a plurality of microlenses at a predetermined arrangement pitch,
The micro lens array is moved by a movement distance shorter than the arrangement pitch by the micro lens moving mechanism,
And the movement of the microlens array by the microlens moving mechanism is a periodic vibration,
The image sensor acquires an image every time the microlens array is moved,
Imaging device satisfy the following condition.
Y = N × X
Here, X is a vibration period of the microlens array, Y is an image acquisition period by the image sensor, N is the number of times of photographing per period, and is an integer of 4 or more. The imaging apparatus according to claim 1, wherein a light-shielding unit that blocks light from the imaging lens is provided on an outer peripheral part of each microlens constituting the microlens array. The imaging apparatus according to claim 1 , further comprising a light source that is fixed to the microlens array and generates illumination light toward the imaging element.

Images