JPH0267528A - Camera with zoom function - Google Patents

Abstract

PURPOSE:To prevent influence of deterioration of picture quality caused by blurring, etc., by preventing the shutter speed of the title camera from getting lower than the shutter speed subjected to a blurring alarm. CONSTITUTION:When a selected shutter speed is, for example, a value lower than 1/60, no clear video can be recorded without a tripod, etc., due to blurring. Therefore, when, for example, the shutter speed is set to a value lower than the 1/60, an alarm is issued by means of a blurring alarm circuit 14 so as to recommend the photographer to change the photographing condition or a mode changeover switch 15 is automatically switched to the high-speed mode side. Thus, when the shutter speed is set to a value lower than the 1/60, the switch 15 is automatically switched to the high-speed mode side and the shutter speed is controlled so that it cannot become lower than the 1/60 within a prescribed gain-up range by enhancing image pickup sensitivity by increasing the gain of signals of a prescribed stage number at a signal process circuit 55. Therefore, the influence of deterioration of picture quality caused by blurring, etc., can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention mainly relates to an improvement of a camera with a zoom function having an active type distance measuring means.

(Background of the Invention) Conventionally, a camera that has an exposure control section that automatically determines the aperture and shutter speed based on the output of the camera's distance sensor has a control system as shown in the exposure control program Pl in FIG. 2, for example. It has a program that determines the aperture value and shutter speed for the subject brightness. Additionally, in cameras that have zoom lenses with variable lens focal lengths, the aperture FNO of the lens generally changes as the focal length changes, so the exposure control program must be changed depending on the lens focal length. The P1 diagram in FIG. 2 shows two types of programs: tele end and wide end.

By the way, since the cost is mainly low in compact type cameras, the AF method is a so-called AF method that emits infrared light, measures the position of the reflected light image on the subject, and measures the subject distance by triangulation. An active method is used.

However, this method cannot be used for cameras with long focal length photographing lenses because there is a limit to the reachable distance of infrared rays.

In other words, in designing an active type AP means,
Where X is the subject distance, X is the depth of focus, and f is the focal length of the photographing lens, the hyperfocal distance is calculated as x = f''/x using Newton's formula %, and this distance is set at the infinite position of the focusing lens. be done.

Next, the depth of field d on the rear side is determined by d = x"x" / (f" + xx'), where δ is the diameter of the permissible circle of confusion.
It is sufficient if the active AF system can measure up to this distance (x-d).

For example, f = 30mm, δ = 14μ, x = F
If NOXδ=2.8X14μ=39.2μ,
x = 30" / 0.0392~23md = 1
1.5m, therefore, from X - d = 11.5m, AF
The system must be able to measure distances up to 11.5m,
In order to achieve this, in the case of this type of active type camera, the performance of the light emitting and receiving system becomes an issue.

In other words, in order to increase the reach distance, it is possible to use a high-output tRED or a high-sensitivity light receiving sensor, but these all increase the cost and further increase the size of the AF system.

Also, if you close down the aperture to increase the depth of focus, for example, FN
If O2,8-5,6, x=]1.5m, d=
In this case, it is sufficient to have a distance measurement capability of 5.75 m, but in order to narrow down the lens aperture to 5.6 m,
This causes the shutter speed to shift to a lower speed side, which causes a loss of freedom in photographing, which is undesirable.

(Objective of the Invention) The present invention solves the above-mentioned problems, prevents the device from becoming larger and more expensive, and prevents the loss of freedom of shooting, while enabling shooting at long distances and even further away. To provide a camera with a zoom function that can prevent the influence of image quality deterioration due to hand shake, etc., even when photographing a low-luminance object at a distance.

(Features of the Invention) In order to achieve the above object, the present invention provides standard first exposure control means that performs exposure control using an exposure control program or a second exposure control program subjected to aperture correction, and when a camera shake warning is issued by a camera shake warning means, when the exposure control unit performs exposure control; and an imaging sensitivity control means for electrically improving the imaging sensitivity of the camera, so that when the distance measurement information is greater than or equal to a predetermined value, that is, when the object is at a far distance that cannot be reached by the distance measurement floodlight signal light in the active method, for example. In such a case, exposure control is performed in accordance with a second exposure control program that has been subjected to aperture correction in place of the standard first exposure control program, and a camera shake warning is issued. , when the shutter speed is less than 1/60, the imaging sensitivity is increased by, for example, amplifying the imaging signal, and the shutter speed is prevented from becoming lower than the shutter speed at which the camera shake warning is issued. shall be.

(Embodiment of the invention) FIG. 1 is a block diagram showing an embodiment of the invention.
is a photographing lens, 2 is an exposure control unit such as an aperture and a shutter,
3 is an optical low-pass filter, 4 is a COD, 5 is a signal processing circuit, 6 is a recording circuit, 7 is a focusing drive means for the photographic lens 1, 8 is a zoom drive means for the photographic lens 1, and 9 is a driving means for the CCD 4. 10 is a control circuit that controls the operation of various circuits; 11 is a ranging circuit that performs, for example, an active AP; 12 is a storage circuit that stores exposure programs; 13 is a photometry circuit; 14 15 is a camera shake warning circuit, and 15 is a mode changeover switch.

In the above configuration, the flow of the exposure control operation of this embodiment will be explained.

When starting photography, the lens focal length is set by the zoom drive circuit 8, and then, in response to pressing the first step of the release switch (not shown), the distance measuring circuit 11 operates to measure the distance. Focusing of the photographic lens 1 is performed by the focusing drive circuit 7 based on the obtained distance measurement value. At the same time, the photometry circuit 13 operates to perform photometry.

Next, when the release switch (not shown) is pressed to the second stage, photographing starts as described below according to the program stored in the control circuit 10.

The light flux that has passed through the photographic lens 1 is subjected to exposure control by an exposure control section 2, and is imaged on a CCD 4, which is an image sensor, via an optical low-pass filter 3, and converted into an electric signal.Then, a signal processing circuit 5 converts the light into a predetermined signal. The signal is processed and recorded as an imaging signal in the recording unit 6, which is a medium such as a magnetic disk.

The above-mentioned exposure control is performed by the photometry circuit 1 in the control circuit io.
The aperture value, shutter speed, etc. are determined and executed by an exposure control program as shown in FIG.

FIG. 2 shows an example of an exposure control program stored in the memory circuit 12. If the distance measurement value by the distance measurement circuit 11 is less than a predetermined value, control is performed by the Pl program and If the predetermined value is controlled by the program in P2, for example, if the predetermined value is set as the distance measurement limit distance of the distance measurement circuit 11, no particular aperture control will be performed within that range, so the degree of freedom in shooting will be increased. In the long distance range where distance measurement accuracy is not lost, the aperture correction can be performed using the P2 program, without using a special distance measurement method.
With normal active AF, it is possible to measure distances at long distances, making it possible to achieve a long focal point of the lens.

By the way, when performing exposure control using a program such as 22 in Fig. 2, the selected shutter speed is, for example, 1/60.
If the value is on the lower speed side, camera shake will occur and clear images will not be recorded if you take pictures without using a tripod or the like. Therefore, if the shutter speed is set to 1/6o, for example, the camera shake warning circuit 14 will issue a warning to prompt the photographer to change the shooting conditions, or the mode selector switch 15 will be automatically set to high-speed mode. Switch to
When the shutter speed is set to less than 1/60 in this way, the mode is switched to the high-speed mode, and the signal processing circuit 5 performs a predetermined number of steps of signal gain to increase the imaging sensitivity and perform a predetermined gain-up. Control the range so that it does not fall below 1/60.

In the 22 program in FIG. 2, the shaded area is the gain-up area, which is switched to by switching to the high-speed mode, and the gain will never be less than 1/60 within the predetermined gain-up range. for example,
In the P2 program, if the brightness is EvlO, F
5.6, 1/30 is selected, but when switched to high speed mode, the IEV gain is increased and F5.6.
Exposure is controlled at 1/60, making it possible to take pictures without the effects of camera shake. Note that when performing this gain increase, a display may be performed using a display means (not shown).

According to this embodiment, when the measured distance value is within a predetermined value, exposure control is performed using a normal exposure control program, and when the distance value is above a predetermined value, exposure control is performed with aperture correction such as stopping down over the entire range. Even if the exposure is controlled by a program, even if the focus is set to a long focal length (that is, the zoom ratio is increased), the AF system will become larger and cost more due to the use of a high-output 1RED or a special sensor. In addition to making it possible to take pictures properly without any problems and without losing the freedom of shooting, when controlling exposure using such an exposure control program with aperture correction, the shutter speed can be adjusted. If it is less than 1/60, the system is configured to issue a camera shake warning and increase the imaging sensitivity, so even when photographing a distant, low-brightness subject, the shutter speed will shift to a shutter speed that causes camera shake. This makes it possible to prevent the effects of image quality deterioration due to camera shake and the like.

(Correspondence between the invention and the embodiments) In this embodiment, the exposure control section 2, the control circuit 10, and the storage circuit 12 serve as the exposure control means of the present invention, the distance measurement circuit 11 serves as the distance measurement means, and the photometry circuit 13 serves as the photometry means. The signal processing circuit 5 and mode changeover switch 15 correspond to imaging sensitivity control means, and the hand shake warning circuit 14 corresponds to hand shake warning means.

(Effects of the Invention) As explained above, according to the present invention, the standard first exposure control means that performs exposure control using an exposure control program or a second exposure control program subjected to aperture correction, and when a camera shake warning is issued by a camera shake warning means, when the exposure control unit performs exposure control; and an imaging sensitivity control means for electrically improving the imaging sensitivity of the camera, so that when the distance measurement information is greater than or equal to a predetermined value, that is, when the object is at a far distance that cannot be reached by the distance measurement floodlight signal light in the active method, for example. In such a case, exposure control is performed in accordance with a second exposure control program that has been subjected to aperture correction in comparison with the standard first exposure control program, and a camera shake warning is issued. When the shutter speed is less than 1/6o, the imaging sensitivity is increased by, for example, amplifying the imaging signal, and the shutter speed is prevented from dropping below the shutter speed at which the camera shake warning is issued. It is possible to shoot at long distances without increasing the size, cost, and loss of freedom of shooting, and even when shooting low-brightness subjects at long distances, the image quality does not deteriorate due to camera shake, etc. This makes it possible to prevent the effects of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an exposure control program stored in the storage circuit shown in FIG. ■・・・Photographing lens, 2・Old exposure control section, 4
...CCD, 5...Signal processing circuit, 7
...Focusing drive circuit, 8...
Zoom drive circuit, 10... Control circuit, 11...
... Distance measurement circuit, 12... Memory circuit, 13.
...Photometering circuit, 14 ... Camera shake warning circuit, 15 ... Mode changeover switch. Figure 2 1: V/FNO

Claims (1)

[Claims] (1) In a camera with a zoom function, which is equipped with a distance measuring means for obtaining distance measurement information to the subject, a photometering means for measuring the brightness of the subject, and a camera shake warning means for issuing a camera shake warning when the shutter speed is on the slow side. , the standard first exposure control program or the aperture-corrected second exposure control program is selected based on information as to whether the photometry information from the photometry means and the distance measurement information from the distance measurement means are greater than or equal to a predetermined value. an exposure control means that performs exposure control based on an exposure control program; and an imaging sensitivity control means that electrically improves imaging sensitivity during exposure control by the exposure control means when the camera shake warning means issues a camera shake warning. A camera with a zoom function.