JPH0331832A - Automatic focus adjusting device for camera - Google Patents

Abstract

PURPOSE:To readjust defocus caused by automatic adjustment by forcibly moving a focusing lens position, which is automatically adjusted within a prescribed range and in a prescribed length of time. CONSTITUTION:If a switch 23 is turned off during a forcibly moving period when normal automatic focus adjustment is carried out, a focusing lens 17 immediately stops its movement at that position. Thus, when a person who supervises a monitor confirms out-of-fucus caused by the automatic focus adjustment on the monitor, a switch is temporarily turned off, and then, the switch 23 is turned on. The lens 17 moves back and forth from an automatic focused position within the prescribed range and in the prescribed length of time. Consequently, if an optimum focus position is included within the forcibly moving range, it is confirmed on the monitor. Therefore, if the switch 23 is immediately turned off, the optimum focus position which is not obtained in the automatic focus adjustment can be obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an automatic focus adjustment device for a camera.
Regarding a device that can arbitrarily correct the automatically adjusted focal position: η.

<Conventional technology> Automatic focus adjustment device for cameras (autofocus device)
The contrast detection method detects the contrast of the photographed subject image, and the trigonometric force (1 quantity 2 and Various methods are known, such as the beam distance measurement method for determining the scale 111 (Japanese Unexamined Patent Publication No. 61-1
No. 56632 (Problem to be Solved by the Invention) However, for example, in a method that detects the contrast of an imaged object, if the object is low: It is difficult to match the subject, and with the method of shining a light beam on the subject, it is difficult to photograph subjects with low reflectance, such as blackout curtains or black hair.

There is a problem that it becomes difficult to focus when the distance to the subject becomes long (more than 5 meters).

Furthermore, with a subject that is difficult to focus on, both of the above methods may result in a small amount of distance data even though the subject is at a certain distance. I try not to move the focusing lens around the average value.

In this way, automatic focus adjustment devices cannot be expected to perform accurate focus adjustment regardless of the subject. However, for example, home-use color video cameras often take pictures of bright subjects; However, in view of the balance with other camera performance, high focus accuracy is not required, so even if the focus is slightly off, the aperture effect can compensate for the focus shift.

However, with cameras such as surveillance television cameras that need to take pictures in relatively dark places such as indoors (for example, with an illuminance of about 10 lux), the aperture effect cannot be expected, so if the focus is off due to automatic focus adjustment, There is a problem in that this defocus becomes noticeable. However, surveillance television cameras are often installed in hard-to-reach places, such as near the ceiling, and are controlled remotely, so even if defocus is confirmed on the monitor, it cannot be easily corrected. There was also.

The present invention has been made in view of the above-mentioned problems.In cameras such as surveillance television cameras, which require high precision in automatic focus adjustment and are based on remote control, The purpose of this invention is to provide a device that can readjust the focus shift due to automatic adjustment with a configuration that allows the automatic focus adjustment device to be turned on and off by a switch on the monitor side in a surveillance television camera. By taking advantage of the fact that there are such things, a device that can achieve the above object is constructed.

<Means for Solving the Problems> Therefore, the automatic focus adjustment device for a camera according to the present invention includes an automatic focus adjustment means for automatically moving a focusing lens to a position where the focal point of the photographing lens system of the camera is aligned with the subject; an operation selection means for switching between activation and non-operation of the automatic focus adjustment means and immediately stopping the automatic focus adjustment including movement of the focusing lens when non-operation is selected; and operation selection means for operating the automatic focus adjustment means by the operation selection means. a forced movement means for forcibly moving the focusing lens within a predetermined range for a predetermined period when the focusing lens is in the in-focus position by the automatic focus adjustment means when the focusing lens is selected; I configured it.

<Function> According to this configuration, when the operation is selected by the operation selection means, the automatic focus adjustment means automatically moves the focusing lens to a position where the focus of the photographic lens system of the camera is on the subject. However, if the focusing lens has already been moved to the in-focus position by the automatic focus adjustment means when the operation is selected by the operation selection means, the forced movement means forcibly moves the focusing lens within a predetermined range for a predetermined period of time. move it.

Here, when non-operation is selected by the operation selection means,
Automatic focus adjustment, including movement of the focusing lens, is immediately stopped, so if the focusing lens is forcibly moved as described above and non-operation is selected using the operation selection means, the forced movement will be stopped. The focusing lens can be stopped at this position.

Therefore, for example, when it is judged on the monitor that the adjusted position by the automatic focus adjustment means is not the optimal focus position, by selecting the operation using the operation selection means, the focusing lens can be moved within a predetermined range from the automatically adjusted focus position. Since the focus is forcibly moved for a predetermined period of time, if you check the focus on the monitor during this movement and decide to deactivate it when it is determined that the focus is correct, the focus will be automatically adjusted to the optimal position. It is something that

<Example) The present invention will be explained in detail below.

In this embodiment, a surveillance television camera is assumed as the camera, and the automatic focus adjustment device (autofocus device) provided in this surveillance television camera is equipped with a monitor so that it can be turned on and off by remote control. Activation and non-operation can be selected by a switch as an operation selection means provided on the side, and when activated, the focusing lens is automatically moved to a position where the focus of the camera's photographic lens system is on the subject.

In this way, the automatic focus adjustment device (power supply to the automatic focus adjustment device) can be turned on and off with a changeover switch in a surveillance television camera that is used continuously. This is to ensure that the automatic focus adjustment device operates only when necessary, in order to extend the life of the infrared light emitting diode, the helicoid of the lens, and the motor.

In FIG. 1 showing one embodiment, light receiving circuits 1.1a, 1.
1b are current signals I+, respectively, from the optical position detector 5;
! 2 into voltage signals V, , V, and also includes a built-in filter circuit to remove noise components. The distance measuring circuit 21 receives voltage signals V, , V from these light receiving circuits 11a and flb, performs analog calculation processing,
A distance measurement signal Vo corresponding to the distance to the subject 3 is output.

The A/D converter 12 inputs the ranging signal 0 from the ranging circuit 21 and the voltage signal 2 from the light receiving circuit 11b and converts them into digital signals. Microcomputer 22
receives the output of the A/D converter 12, performs various arithmetic processing, and generates an emission control signal for controlling the emission of the infrared light emitting diode I and a focus control signal for adjusting the focus of the focusing lens 17. and perform light emission control and focus control.

The light emitting side j1a signal of this microcomputer 22 is
The focus control n signal is applied to a motor drive circuit 15 for driving a motor 16. The output of the encoder 18 that detects the moving position of the focusing lens 17 is transmitted to the microcomputer 2.
It is feedbanked to 2.

To explain the operation of the automatic focus adjustment device 77 (automatic focus adjustment means) configured in this way, the microphone 22 gives a control signal to the light emission control circuit 14 and controls the infrared light emitting diode 1. is emitted to irradiate the subject 3 with infrared light beams J through the projection lens 2. The reflected light of the infrared light beam irradiated onto the subject 3 is received as a spot light via the light receiving lens 4 at a position corresponding to the distance to the subject 3 of the leading η detector 5F. The optical position detector 5 generates current signals II, ! according to the light receiving position. 2, and these current signals x, , rt are converted into voltage signals V, , V after noise removal by the light receiving lines 11a, llb. The distance measuring circuit 21 detects the object 3 based on the voltage signals V, , V,
A distance measurement signal ``0'' corresponding to the position up to is outputted, and this al distance signal ``0'' is converted into digital data by an A/1] converter 12 and input to a microcontroller/computer 22.

Next, the micro combinator 22 takes in the output of the encoder 18 at that point in time, and compares the distance measurement signal ``0'' with the lens movement amount signal from the encoder 18. Here, when the desired lens movement position based on the distance measurement signal Vo is different from the position of the focusing lens 17 detected by the encoder 18, a focus control signal is given to the motor drive circuit 15 to control the focusing lens 17 according to the distance measurement signal. Vo
The encoder 18 outputs the distance measurement signal V.

When it is detected that the lens has moved to a position corresponding to , the operation of the motor IG is stopped, and the focusing operation of the photographic lens system is completed.

By the way, as mentioned above, in order to be able to perform the above focusing operation by remote control only when necessary, a changeover switch (autofocus jJR!J, ON・OFF switch)
23 is provided, and by operating this changeover switch 23, the automatic L point adjustment operation is turned on.
It is designed so that it can be switched between "Ol" and "F".

Therefore, as shown in FIG. 3, the switch 23 is turned off.
During this period, the focus of the photographing lens system is not adjusted. Because the automatic focus adjustment that automatically moves the focusing lens to the opposite position is not performed, the image being monitored may be out of focus. There is.

Here, when the switch 23 is turned on, the distance to the subject 3 is measured 7 as described above, and the focusing lens 17 is moved in accordance with the measured distance position. Note that the switch 23 is turned off while the focusing 1 nons 17 is being moved.
When the FF is turned off, the automatic focus adjustment system is all OFF.
I? Therefore, the focusing lens 17 stops moving at the position when the switch 23 is turned off.

However, if the subject 3 has a low reflectance or is uneven, the distance to the subject 3 may be incorrectly measured by the distance measuring mechanism with the above configuration, and the focusing lens is adjusted based on this result. Since the position of the focusing lens 17 is controlled, the focusing lens 17 is at a position slightly shifted from the best focal position. In such a case, since the focus is automatically adjusted based on the distance measurement result, the best focus position cannot be automatically obtained unless the conditions of the subject 3 change.

Therefore, in this embodiment, as shown in the flowchart of FIG. 2, the focusing lens 17 is forcibly moved within a predetermined range from the distance measurement position for a predetermined period of time, and when the best focus is confirmed on the monitor during that time, the switch is By turning 23 off, the focusing lens 17 can be adjusted to the best focal position. The function of the forced movement means in this embodiment is shown in the flowchart of FIG. 2, together with the function of the automatic focus adjustment means.

The program shown in the flowchart of FIG. 2 is executed when the switch 23 is turned on. First, in step l (indicated as Sl in the figure, the same applies hereinafter), the microcomputer 22 is initialized. ,
In the next step 2, distance measurement is performed by irradiating an infrared light beam.

Then, in step 3, the actual position of the focusing lens 17 is compared with the distance measurement position, and if the focusing lens 17 is not in the focus position, the process proceeds to step 5, where the motor 16 moves the focusing lens 17 to the distance measurement position. control. Then, in the next step 6, distance measurement is performed again, and if it is determined in step 7 that there is a shift between the lens position and the distance measurement position due to movement of the subject 3, the process returns to step 5 and the focusing lens is adjusted. (2) 7 is moved to the focusing position, but if it is determined in step 7 that the focusing lens 17 is at the distance measurement position, the process returns to step 6 and distance measurement is repeated. Such automatic focus adjustment is performed as described in detail above, and while the switch 23 is ON, distance measurement and movement control of the focusing lens 17 are constantly repeated.

On the other hand, if it is determined in step 3 that the focusing lens 17 is at the distance measurement position, that is, the switch 23 is turned ON.
However, if there is no need to move the focusing lens 17, the process proceeds to step 4, where the focusing lens 17 is forcibly swung back and forth from the distance measurement position. The range in which the focusing lens 17 is forcibly moved ↓. For example, if the angle from the proximity of the focusing lens 17 to infinity (1) is a, then ±a/16°
~±a/8° or so, and by moving the focusing lens 17 at a constant speed within this preset range, movement for a predetermined period in a predetermined range is realized.

The action of forcibly swinging the focusing lens 17 back and forth is shown in a time chart in FIG. I moved it to the side and returned it to the distance measurement position. Therefore, if the switch 23 remains ON during this forced movement period, it will move back and forth to the distance measurement position and then return to the distance measurement position again, and normal automatic focus adjustment will be performed. If the switch 23 is turned off during the operation, the focusing lens 17 immediately stops moving at that position.

For this reason, when a person monitoring the monitor confirms that the monitor is out of focus due to automatic focus adjustment, the -1 switch 2
3 and then turn on the switch 23, the focusing lens 17 moves back and forth from the automatic focus adjustment position, and if the best focus position is included in this forced movement range, check that position on the monitor. Therefore, if the switch 23 is immediately turned off at that time (point A in FIG. 4), the best focal position that could not be obtained by automatic adjustment can be obtained.

That is, when the automatic focus adjustment device is turned on and the focusing lens 17 is at the distance measurement position, a function has been added to forcibly move the lens 17 back and forth from the distance measurement position for a predetermined period of time. Therefore, when the best focus position cannot be obtained with automatic adjustment, the lens 17 can be moved to an arbitrary best position, and the object 3 whose distance is incorrectly measured can be moved.
However, even with the best focus position, images without blur can be obtained. However, there is no need to separately provide a switch or the like for forcibly moving the focusing lens 17, and the above effects can be obtained with a simple configuration (just adding software).

In this embodiment, when the focusing lens 17 is forcibly moved, as shown in FIG. Although the movement is made to the infinity side, for example, it may be moved suddenly by a predetermined distance from the distance measurement position and then gradually returned to the distance measurement position, and the pattern of forced movement is not limited.

<Effects of the Invention> As explained above, according to the present invention, automatic focus adjustment can be turned on and off by remote control, such as in a surveillance television camera.
For objects that are switched from OFF to OFF, the automatically adjusted focusing lens position can be forcibly moved, and when the optimal focus position is confirmed during this movement, the focusing lens can be stopped at will, so automatic focus adjustment is possible. Even if the subject conditions are such that it is not possible to move the focusing lens to the optimal focal position,
The optimal focus position can be obtained arbitrarily, and there is no need to provide a separate spinner for readjusting the focus, and all the effects can be obtained with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a system block diagram showing an embodiment of the present invention;
FIG. 2 is a flowchart showing control contents in the same embodiment, and FIGS. 3 and 4 respectively show control characteristics in the same embodiment. ■...Infrared light emitting diode 2...Light projection lens 3
...Subject 4...Light receiving lens 5...Optical position detector 11a, llb...Light receiving circuit 12.
...A/D converter 14...Light emission control circuit
15...Motor drive circuit 16...Motor 17.
... Focusing lens 18 ... Encoder 2
1... Distance measurement circuit 22... Microcomputer
23...Switch Figure 2

Claims (1)

[Claims] An automatic focus adjustment means that automatically moves the focusing lens to a position where the focal point of the photographic lens system of the camera is aligned with the subject, and switching and selection of activation/deactivation of the automatic focus adjustment means, and movement of the focusing lens when inactivation is selected. an operation selection means for immediately stopping automatic focus adjustment including;
Forced movement means for forcibly moving the focusing lens within a predetermined range for a predetermined period when the focusing lens is in the in-focus position by the automatic focus adjustment means when the operation of the automatic focus adjustment means is selected by the operation selection means. An automatic focus adjustment device for a camera comprising: