JPS6211836A - Correcting device for depth of focus - Google Patents

Abstract

PURPOSE:To correct the depth of focus without changing an optical system, by bringing an optical image to an image pickup by plural planes, and fetching selectively an image signal of a part having the maximum space frequency. CONSTITUTION:When a control signal from a CPU 12 is received, a servo-mechanism 4 positions an image pickup device 2 successively in different image pickup planes. Each image signal from the image pickup device 2 is stored in frame memories MI-MIII through an A/D converter 6 and a signal processing circuit 7. The image signals which have been stored in these frame memories MI-MIII are inputted to a discriminating means, space frequencies in the same part of each optical image are compared, and a part having the maximum space frequency is discriminated. An image signal of the part having the maximum space frequency is fetched by a selecting means C, and stored in an image synthesizing use memory 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a depth of focus correction device that corrects the depth of focus determined by an optical system.

[Prior art]

Conventionally, the depth of focus in an imaging device such as an electronic camera is determined as follows. That is, since the depth of focus is determined by the inherent constants of the optical system such as lenses, there is a problem in that the optical system must be changed in order to correct the depth of focus.

〔the purpose〕

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a depth of focus correction device that can correct the depth of focus without changing the optical system.

〔Example〕

Hereinafter, an embodiment of the present invention will be described based on FIG.

In the figure, 1 is a three-dimensional object, 2 is an image sensor such as a CCD that captures an optical image from the object 1 via an optical system p, and 4 is an image sensor that moves this image sensor 2 in the optical axis direction. A servo mechanism is positioned on the planes x, n, and m of the image pickup device 2, and constitutes an image pickup means A together with the image pickup device 2. 6 is an A/D converter that converts the image signal outputted from the imaging means A via the amplifier 5 into a digital signal; 7 is an A/D converter that performs predetermined signal processing on the image signal from this A/D converter to adjust the screen size. A signal processing circuit that performs alignment and positioning, MI,
MII and MIII are three frame memories that store the image signals output from the signal processing circuit 7, and the image signals for one frame obtained by imaging on the plane ■ are stored in the frame memory MI and on the plane II. An image signal for one frame obtained by taking an image is stored in a frame memory MII, and an image signal for one frame obtained by taking an image in a plane 2 is stored in a frame memory MIII. Note that each memory MI,
Pixel signals obtained from the same pixels of the image sensor 2 located on each plane are stored at the same address of MII and MIII. 8a, 8b, and 8c are three differentiators connected to the three memories MI, MII, and MIII, and among these, the differentiator 8a is the frame memory IJ M I
, the differentiator 8b is stored in the frame memory MII, and the differentiator 8b is
C is connected to frame memory MIII, respectively. Reference numeral 9 denotes a comparator which constitutes a determining means B together with differentiators 8a, 8b, and 8c, which compares the outputs from each differentiator 8a, 8b, and 8c, and determines which differentiator outputs the maximum value. It has the following configuration. That is, 9a1 is a comparator that compares the outputs a and b of the differencers 8a and 8b, 9a2 is a comparator that compares the outputs C of the differencers 8b and 80, and 9a3 is the differencer 8a.
and 8C, each comparator 9aI, 9a2.

From 9a3, "1" is output when the non-inverting input is large. 9bl is comparator 9a
Gate circuit 9b2 into which signals from l and 9b2 are input
9b3 is a gate circuit into which signals from comparators 9a2 and 9a3 are input, and 9b3 is a gate circuit into which signals from comparators 9al and 9a3 are input. These three gate circuits 9bl, 9b2.9b3 are connected to the previous stage comparators 9a1. The signals shown in Table 1 are output in response to the signals output from 9a2 and 9a3.

Further, 10a, 10b, and 10c are three switches connected between the three (7) 7-frame memories MI, MII, M and the image synthesis frame memory 11, and a selection circuit C as a selection means. The AND circuit 9b
ON and OFF are controlled by signals from 1.9b2.9b3. Reference numeral 12 represents a CPU that controls the above circuit, and reference numeral 13 represents a keyboard that performs input to the CPU 12.

Next, the operation will be explained based on the flowchart shown in FIG.

First, upon receiving a control signal from the CPU 12, the servo mechanism 4 positions the image sensor 2 on the imaging plane ■ (step l).
, an optical image from the subject 1 entering through the optical system 3 is captured (step 2). The image signal obtained from the image sensor 2 is stored in the frame memory MI after passing through the amplifier 5, A/D converter 6, and signal processing circuit 7 (step 2). After that, the servo mechanism 4 moves the image sensor 2 to the imaging planes ■ and ■, and similarly to the above, the image signals obtained by imaging on each plane are stored in the frame memories MII and M■ (steps 3 to 6). .

Note that the images obtained by imaging on each plane are processed by the signal processing circuit 7.
The size and position of the screen are adjusted and stored in each frame memory MI, MTI, MIII. and the frame memories MI, MII.

After giving address signals to Mm and the image synthesis memory 11 (step 7), each frame memory MI, MII,
A pixel signal at the same address is read from MI[[, and the image synthesis memory 11 is set to write mode (step 8). Pixel signals read from the frame memories MI, MII, MU are input to differentiators 8a, 8b, 8c. Each differentiator 8a.

8b and 8c output the difference between the currently input pixel signal and the pixel signal input immediately before that pixel signal,
This is input to the comparator 9. In the comparator 9, each differentiator 8
Three comparators 9al and 9a2 determine the magnitude of the outputs from a, 8b, and 8c.

9a3 compares the magnitude of the spatial frequency, and outputs a signal as shown in Table 1 to the subsequent gate circuit 9b1.

Input to 9b, 2, 9b3. Gate circuit 9J.

9b2 and 9b3 are respective comparators 9a1.

3 as shown in Table 1 after receiving the signals from 9a2 and 9a3.
output signals. Upon receiving this signal, switch loa
, 10b, and 10c are turned on, and the pixel signals read from the frame memory connected to the turned-on switch are stored in the subsequent image synthesis frame memory 11.

For example, assume that the signal output from the differentiator 8b is the maximum. In this case, each comparator 9al, 9a2
．． A signal "rQJ rlJ rt" is output from 9a3, and the pixel signal read out from the frame memory Mrl is stored in the image synthesis frame memory 11.

After this, in steps 9 and 10, the frame memory M
I, MII, M■ and frame memory 11 for image composition
The number of addresses specified is increased, and the operations of steps 7 and 8 are repeated for all the pixel signals for frame (1). As a result, an image with a deep depth of focus in which every part of the object is clear is synthesized in the image synthesis frame memory 11.

Next, a second embodiment of the present invention will be described based on FIGS. 3 and 4. Note that the same parts as in the first embodiment are given the same reference numerals, and detailed explanation thereof will be omitted.

This second embodiment is based on the difference device 8a shown in the first embodiment.
, 8b, 8c and the comparator 9, and the selection circuit C
The selection is made using the CPU 12, and its operation is as shown in the flowchart of FIG.

First, in steps 1 to 8, 3
It performs operations such as imaging in 1,000 planes r, n, and m, storing the obtained image signals in the frame memories MI, Mll, and M2, and reading out pixel signals from the frame memories MI, MU, and M2. After this, in step 9, each frame memory MI,
The difference between the pixel signal read from MTI and Mm and the immediately preceding pixel signal is determined. Then, it is determined whether or not the difference in the frame memory MI is the largest among the differences (step 10), and if it is the largest, the pixel signal from this frame memory MI is transferred to the image synthesis frame memory
1 (step 11), and if it is not the maximum, it is determined in step 12 whether or not the difference in the frame memory MII is the maximum. Here, frame memory MII
If the difference in is the maximum, the pixel signal output from the frame memory MII is transferred to
(Step 13), and if it is not the maximum, the pixel signal output from the frame warp Mm is stored in the image synthesis frame memory 11 (Step 14). Thereafter, in steps 15 and 16, the frame memory for image synthesis is
Pixel signals for l frames are stored in .

Next, a third embodiment of the invention will be described. In this third embodiment, the comparator 9 in the first embodiment is replaced with a differentiator 8.
Magnitude comparators 14a, 14b, 14c compare the magnitudes of outputs a, b, and C from a, 8b, and 8c, and signals Sa shown in Table 2 according to the output signals from these,
This uses a comparator 16 consisting of a ROM 15 from which Sb and Sc are read.

Table 2 Signals Sa, Sb, Sc read from this ROM15
is input to switches 10a, 10b, and 10c,
The switches 10a, 10b, and 10c are turned on when the input signals Sa, Sb, and Sc are "1". Note that the other configurations are the same as those of the first embodiment, and similarly to each of the embodiments described above, a clear image with a deep depth of focus can be obtained.

In the above embodiment, three planes I, II,
Although we have shown the case where the image was captured using a prism, the light is spatially divided using a prism or the like, and three planes I, II, m are prepared in advance.
Images may be captured using three image sensors arranged above. In addition, the number of imaging planes is not limited to three planes,
The number of planes can be changed to any other desired number.

〔effect〕

As explained above, the depth of focus correction device of the present invention has the advantage that the depth of focus can be corrected without changing the optical system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG.
The figure is a flowchart showing the operation of the one shown in Figure 1.
FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG.
This figure is a flowchart of the process shown in FIG. 3, and FIG. 5 is a block diagram showing the main part of a third embodiment of the present invention. l・・・・・・・・・・・・・・・Subject 10a
, 10b, 10cm2...-switch (selection means C
)

Claims (1)

[Claims] An imaging means that captures an optical image from a subject incident through an optical system on a plurality of planes, and a determination that compares the spatial frequencies of the same portion of the optical image captured on each of the planes and determines the portion having the maximum spatial frequency. A depth-of-focus correction device comprising: means for selectively extracting the image signal of the portion having the maximum spatial frequency.