JPS6336213A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To detect a focusing direction on the basis of a focusing state and chromatic aberration and to attain rapid focusing by providing the titled device with a means for changing an image forming state, a means for converting object image information into two chrominance signals and a means for detecting the focusing state of an image corresponding to the two colors. CONSTITUTION:An image is focused by a lens 101 on an optical axis, a focal distance is changed by a lens 1-2, the position of the lens 1-2 is detected by a position detector 3 and the aberration comparing information C' of color G with colors R, B and the chromatic aberration direction AC of the color G are stored in a ROM15. The color information of the object is converted into three chromatic signals and a luminance signal Y by an image pickup element 4 and either one C of R and B is selected by an analog SW5 by controlling a microprocessor 16 to extract signals corresponding to the center of a screen through gates 6, 8. The intensity of their HF components is normalized, sharpness QC, QG are outputted through sharpness detectors 7, 9, the peaks of the output signals are held, the shaded degree is evaluated by a microprocessor 16, the size of the HF component of the object image is detected by the luminance signal or through prescribed processing and the invalidity of focusing direction decision due to large out-of-focus is processed by the signal F. Thus, rapid focusing can be attained by holding the image surface S at the intermediate state between G and C (R or B).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focusing device suitable for video cameras and the like.

[Prior art] Conventionally, as an automatic focusing device 1!1'' of a video camera, etc., 1
11) Detect the sharpness of the object image on the imaging surface using the image index obtained from the image element, and set the lens so that the 74Y sharpness is the highest! It is known that the 15th type is ``C'', which has 111 points when driving.

[Problem to be solved by the invention] Such an automatic focusing method does not require 7 special 12-light components, and it is just like 110-shade lens.

However, it has the advantages of being applicable, but it also has the following disadvantages. In other words, in this J: Tuna method, the photographic lens should be adjusted to improve the sharpness of the image! -] Because it moves steadfastly, drive the photographing lens once and do not change the image formation state to determine whether it is in the focused direction.1. stomach. For this reason, when performing focusing, it is necessary to drive the photographic lens once and determine the direction in which the focus will be achieved based on the state of change in 9Y acuity at that time, or determine the driving direction of the photographic lens at that time. Due to the lack of information, there is a 50% probability that the focus will be driven in a direction that is even worse. As a result, the image obtained from the image sensor may become further out of focus and then come back into focus, which reduces the focusing response speed and causes images to be captured continuously like a video camera or TV left camera. This results in an unsightly image in a device that photographs a subject, and it is difficult to follow and focus on a subject that moves back and forth.

In order to solve these drawbacks, it is possible to periodically change the image formation state of the photographing lens by a small amount, or to place another image sensor at a position W in the optical axis direction from the image sensor for photographing. to determine the driving direction of the photographic lens.
method) 11! Both methods require extra drive devices, imaging elements, optical components, etc., and are expensive.

The purpose of the present invention is to provide an automatic focusing device that solves the two problems and is capable of determining the direction of focus without driving the photographic lens, and that can perform automatic focusing at high speed. It's about doing.

[Means for Solving the Problems] The invention includes a photographing optical system, a driving means for changing the image formation state by the photographing optical system, and information on a subject image formed on an imaging surface by the photographing optical system. an imaging means for converting the image into color signals of at least two colors; a detection means for detecting a focused state of a subject image corresponding to at least two colors based on the at least two color signals from the imaging means; It has means for controlling the driving means based on the in-focus state of the subject image corresponding to at least two colors and information on the axial chromatic aberration of the photographing optical system.

[Function] The present invention utilizes the axial chromatic aberration of the photographic lens to detect which of two different colors, for example, red or blue, is in focus, thereby photographing in the direction in which it is in focus. Drive the lens.

[Example] FIG. 2 is a diagram explaining the details of the tree invention.

In Fig. 2, a is the optical axis, S is the imaging plane for imaging = +1, G is the best image plane of the photographing optical system for the green light of the current subject W, and Cii is the best image plane for the green light. This is the best image plane of the photographing optical system for external colors, for example red or blue light. , when the position of C is Xc,
X (> X (+).

In the states of Fig. 2 ■ and ■, the direction of G or C with respect to the imaging surface S is
J: Due to the distance, the subject image on the imaging surface S is more blurry than the green color or the color corresponding to C;
■The green color is more blurred or less blurred. Figure 2 in between ■
G and C are equidistant from the imaging surface S! 811, and the amount of light rising is about the same, and since both are close to the imaging surface S, it can be considered that the two are in focus.

Therefore, the green component of the subject image is determined from the color image signal obtained from the image sensor! If we detect the peak sharpness Q6 and the sharpness Qc for the color component corresponding to C and compare their magnitudes, we find that in the state of ■ in Fig. 2, Qa'<Qc, and in this case It is good to move the focus of the system in the infinite direction, and conversely, in the states of ■ and ■ in Figure 2, Qa > Qc,
In this case, you will know that it is best to move the focal point of the photographic optical system in the direction of close range. Q. As shown in Figure 2 ■. When Qc is reached, it is determined that the image is in focus. Since the sharpness levels Q6 and Qc to be detected are different in pattern and contrast depending on each color in a general subject, it is necessary to use an evaluation method that does not depend on the pattern or contrast of the subject as much as possible.

FIG. 1 is a block diagram illustrating the invention in detail.

Reference numeral 1 designates a photographing optical system which is a zoom lens, and reference numeral 11 designates a focusing lens thereof, which is moved in the optical axis direction by a motor 2 for focusing. ! -2 is a zoom lens variator that changes the focal length of the photographing optical system by moving in the optical axis direction. The position of the variator 1-2 in the optical axis direction can be detected by a position detecting means 3 such as a potentiometer, and thereby the zoom state of the photographing optical system is detected.

Reference numeral 4 denotes an image sensor which is disposed on a predetermined image plane of the photographing optical system 1, and which, in combination with a color separation optical system such as a color mosaic filter or a dichroic prism (not shown), captures color information of a subject image on the image pickup plane, for example. Red-green,
An analog switch 65 converts the image signals R, G, and B corresponding to the three colors of blue into a luminance signal Y obtained from these signals. Select one of the signals B as the signal C. Reference numerals 6 and 8 are gate circuits that extract image signals corresponding to the center of the imaging surface. 745 and 9 are 14y sharpness detection means to be described later, which detects the i-sharpness Qc of the red or blue component and the sharpness Q6 of the green component of the subject image from the image signals C and G, respectively. The microprocessor 6 has memory means for storing control procedures as described later (FIGS. 5 to 1O).

lO~13 is used when it is impossible to determine the direction of focus due to chromatic aberration.
0 is a gate circuit similar to gate circuit 6.8, 11 is a bypass filter, 12 is a detection circuit, and 13 is a to-70 converter.

Reference numeral 14 denotes a drive circuit for the motor 2, which controls the motor 2 in response to a control signal from the microprocessor 16.

Reference numeral 15 denotes a ROM (1'1ead onl
yMemory). In the present invention, the larger the axial chromatic aberration, the easier it is to judge the in-focus direction.
OM! 5 records information C' indicating which longitudinal chromatic aberration is greater for green, red or blue, and the ljb upper chromatic aberration direction AC for green in that case. Here, for green light, the image plane of color C' is 8,
-1, it is on the image world side, and when Ac--1, it is on the object world side.

FIG. 3 shows an example of the sharpness detection means 7 and 9 in FIG. 19 is set slightly lower than 17.

Reference numeral 18.20 represents a band pass filter, and a sawtooth detection circuit obtains a low frequency signal indicating the strength of the high frequency component from the signals extracted by the bandpass filter 17.19. Reference numeral 21 denotes a divider circuit, which manually inputs the signals from both transverse wave circuits Ill and 19 and converts the intensity of the high frequency component extracted by the band pass filter 17 into the intensity of the high frequency component slightly lower than that extracted by the band pass filter 19. A signal indicating the sharpness Q is obtained by normalizing with . The signal indicating the sharpness Q is held by the peak bold circuit 22 and output. In this way, it is possible to obtain an evaluation value of the degree of blur of the subject image without depending much on the contrast or pattern of the subject.

FIG. 4 shows another example of the sharpness detection means 7 and 9 in FIG. 2, where 23 is a differentiation circuit (or difference circuit) that takes the differentiation (or difference) of the image signal, and 24 is the output signal of the differentiation circuit 23. 25 is a delay circuit that delays the output signal of the absolute value circuit 24 by a time T/2; 26 is a delay circuit that delays output No. 3 of the circuit 24 by a time T iJ; 27 is the absolute value circuit 24 and the delay circuit 2
Difference circuit that manually inputs the Ryokawa force signal of 6 and outputs the difference, 2
8 is an integration circuit that integrates the output signal of the difference circuit 27, 29 is a division circuit that inputs and divides the Ryokawa power signals of the delay circuit 25 and the integration circuit 2B, and 30 is a bold peak of the output signal of the division circuit 21. This is a peak hold circuit. For example, an evaluation value Q indicating the degree of blur of the subject image is obtained by detecting an etched part such as a contour part of the subject image from the image signal and determining its sharpness.
-245239.

Note that in a state where the amount of out-of-focus is very large, so-called a large beam, the sharpness Q detected by the sharpness detection means 7.9. Both Qc and Qc become small values, and it may become impossible to judge the direction of focus due to the influence of noise in the image signal.
1 is once driven in an arbitrary direction, and the in-focus direction is detected by increasing or decreasing the signal F, which indicates the strength of the high-frequency component of the glare, but in this case, since the image is originally quite blurry,
Even if the initial driving direction of the lens is incorrect, there is no practical problem.

Next, the operation of this device will be explained.

5 to 10 are flowcharts of the basic operation of the microprocessor 16. When the power is turned on, the fifth
The operation starts from Figure S-1, and then register A' = 0 in S-2. Let register A=1. Here, register A' indicates the current driving direction of the motor, and register A'=O indicates that the motor is stopped. Further, register A indicates the direction in which the motor should be driven next, and register A=1 indicates that the focusing lens I-1 is to be driven toward infinity. Next, in S-3, Fig. 5 S-
Call 1. ■ At -1, data is input, and at T-2, in synchronization with the start of vertical scanning of the image sensor 4, the ROM 15
Read information C' and direction Ac from T-3 and read information C'
Analog switch 5 so that the signal corresponding to
give a control signal to the Next, at T-4, the sharpness Q detected at the end of vertical scanning of the image sensor. .

Qc and the intensity F of the high frequency component are read out and the process returns.

Next, in FIG. 5 S-4, the detected sharpness levels Qa and Qc are compared with a threshold value ΔQ to determine whether or not it is possible to determine the focusing direction based on chromatic aberration. When both the sharpness Qa and Qc are smaller than the threshold value ΔQ, the direction cannot be determined based on chromatic aberration, so we proceed to S-5 and record the intensity F of the high frequency component in the register F. and calls P-1 according to the value set in register A at S-6.

In FIG. 1O, P-1 to P-7, the motor is driven and a timer is controlled to determine whether the focusing lens 11 has reached the infinity end or the close end.

P-2 determines whether register A=O or not, and if A=0, P
-8, the timer is turned off to stop the motor, and the program then jumps to P-6, stores the current motor status in register A' as A'-A, and returns. If A≠0 at P-2, the process goes to P-3 and it is determined whether the register A' is 20 or not. If A' = 0, that is, the motor is stopped, proceed to P-9, turn on the timer □ to start measuring time, start driving the motor in the direction indicated by register A, and return to P-9. Proceed to 6. Also P-3
If it is not A'-0, proceed to P-4, where A'-
Determine whether or not A, and if A' - A, the motor will continue to drive in the current motor drive direction, so return to P-10, and if A'≠A, the drive direction will be reversed. Proceeds to P-5, resets the timer, starts a new 04-hour M measurement, reverses the motor, and returns to P-5.
Proceed to 6 and return with P-7.

Next, returning to Fig. 5, it is determined in S-7 whether or not the time indicated by the timer has exceeded a predetermined value. 5-19 because it was a hit.
At 5-20, set A=-A, reverse the motor at 5-20, and move to FIG. 6, 5-21. If the time indicated by the timer does not exceed the predetermined value in S-7, the process proceeds to S'-8, where data input processing T-1-T-5 is performed again, and Q is entered in S-9.
It is determined whether y>ΔQ and Qc>ΔQ, and if Yes, proceed to 5-14 as in the case of S-4. If No in S-9, it is assumed that the direction cannot be determined based on chromatic aberration, and the process proceeds to <5-10 where the direction is determined based on the state of change in the intensity F of the high frequency component in the luminance signal, and then It' F
It is determined whether OI (FO: register storing F of a predetermined time ago) is larger than a predetermined noise level △F, and if it is, it returns to S-7 again and waits until 1FFol>△F. If ol>ΔF, proceed to 5-11, then judge whether F<F, and F<F. , that is, if F is in the decreasing direction, the motor is reversed by 5-12, and as shown in FIG.
-Checked at 21.

Also, in S-4 and S-9, Qa>△Q and Qc>△Q
In this case, the direction is judged by comparing the magnitude between Q6 and Q9, so the process proceeds to 5-14, and if the difference between Q6 and Qc is smaller than the predetermined threshold value Q', then
-25 and performs focusing processing. Also 5-14 te 1
QaQcl<△Q' If not, proceed to 5-15,
Therefore, it is determined whether Qa>Qc. If Qa>Qc, then the conditions shown in Figure 2 ■ and ■ will proceed to 5-17, where it will move in the opposite direction to the direction indicated by Ac, and if Q a < Qc, it will move to 5-16, where Ac The motor is driven in the direction shown in FIG. 6, 5-21.

5-21 to 5-24 in FIG. 6, it is determined whether the direction is in focus, and the focus is detected while the dryer is being driven in that direction. For this reason, it was 5-21 and QG.

Input Qc, check whether Q6>△Q or Qc>△Q using 5-22, and if yes, go to 5-23, then IQ
Determine whether GQcI<△Q'. IQ6-Qcl<Q
' In that case, processing at the time of focusing is performed as shown in Fig. 7, 5-25. If 5-22 is No, it will be 5-24, 5-2
3, 1Q6-Q, :l<△Q', and the result is 5-24. 5-24, determine whether the timer does not indicate or exceeds a predetermined value, and if 1- is not possible, return to 5-21,
When this happens, for example, the subject approaches and the υ does not match, so perform the processing in that case according to Figure 8 5-29 1, Figure 7 5-25 to 5-28 has an IQ of 6
The process is performed when Qcl<△Q' and focus is detected, and the motor is stopped in steps 5-15 and 5-26.
Then, in 5-27, data manual T-1 is performed, and in 5-28, it is determined whether Q, ＜△Q”
), return to 5-25, otherwise go to S15, and then determine the direction in focus and move in that direction.
Start driving in the evening. 5-28 Q6 again (, #:Qo
△QJ: If it becomes small, it is assumed that the focus has been significantly lost, and the process returns to S-1 and refocuses from the beginning.

5-24 If the time indicated by the timer exceeds the predetermined value λ before the focus is reached, the process moves to Figure 8 5-29, where the intensity F of the high frequency component of the brightness can material and the driving direction of the motor are determined. A and register F. , Ao.

Save it to 5-30 and stop the motor, then 5-3
In step 1, perform data manual] -1, and in step 5-32 wait until there is a change in the intensity F of the high frequency component, and if the change does not occur, redo the focusing υ゛ and drive in step 5-33. Set the kneading direction to be the opposite direction, and repeat the C focusing process in S-3 of Figure 5.

According to the above embodiment, two types of colors (G, R or B) (;3
Two signals are obtained from the camera according to the focus state of the subject.
The imaging state of the photographing optical system is changed from the two signals 43, and the two signals 43 correspond to the focusing state.
- When the level is low, the high-frequency component of the brightness signal output from the image sensor is detected 17, and the imaging state of the shadow optical system is changed in accordance with the high-frequency component. There is.

Therefore, appropriate focusing can be quickly achieved in any case.

In addition, in this embodiment, as mentioned above, two types of colors (G and R
Or B) the signal is detected, but the image sensor 4
If complementary colors are used, such as yellow, magenta, cyan, etc., the in-focus state of the subject may be detected from such color signals.

[Effects of the Invention] As described above, according to the present invention, it is possible to detect the in-focus direction and perform focusing at high speed without driving the photographing optical system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, FIG. 2 is a diagram explaining details of the invention, and FIGS. 3 and 4 respectively show the sharpness detection means 7 and 7 of FIG. :
Block diagrams showing the circuit configurations of Figures 5 and 9, Figures 5 to 1Oi
This is a flowchart for performing automatic focusing. 7.9...Sharpness detection means, 11+...Microprocessor. Whistle 6N Fig. 7 Fig. 8

Claims (1)

[Scope of Claims] A photographing optical system; a driving means for changing the imaging state of the photographing optical system; an imaging means for converting into a signal; a detection means for detecting a focused state of a subject image corresponding to the at least two colors based on color signals of at least two colors from the imaging means; and at least two color signals from the detection means. An automatic focusing device comprising means for controlling the driving means based on a focused state of a subject image corresponding to a color and information on axial chromatic aberration of the photographing optical system.