JPH0694988A - Still image recorder - Google Patents

Abstract

PURPOSE:To enable automatic focusing up to a practical distance with reflected light by auxiliary light even in the case that a phase difference cannot be detected. CONSTITUTION:Light incident on a lens 1 is transmitted through a stop 2 and a 45-degree mirror 3, and then, it is reflected on a submirror 4 positioned behind the mirror 3. And, the light is transmitted through a lens 10 in an AF optical system so as to be made incident on an AF sensor 11. When the brightness of an object is low and the contrast of the object is low, the auxiliary light is emitted in the case that the auxiliary light and a stroboscope are incorporated with the camera, meanwhile, in the case that the stroboscope is not incorporated with the camera, a warning that the stroboscope must be loaded is given by a sounding part 13, and then, the auxiliary light incorporated with the stroboscope is emitted. When an image spacing is not obtained even in the case of emitting the auxiliary light, first of all, it is judged that a defocusing quantity is large, then, a focal position is searched within an extent capable of moving a lens, and when the focal position is not detected, it is judged that the object is in the distance, so that the storobe light is emitted instead of the auxiliary light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a still image recording apparatus for recording a still image picked up by an image pickup means such as a CCD on a recording medium.

[0002]

2. Description of the Related Art Conventionally, there are various types of automatic focus adjustment devices. For example, in a single-lens reflex type silver halide camera, a phase difference detection type automatic focus adjustment (AF) function is provided in many models. It is used. The phase-difference detection AF system generally operates as follows. As shown in FIG. 4, the light incident from the lens is reflected downward by the sub-mirror attached to the rear part of the main mirror (45-degree mirror), and a secondary image-forming lens called an eyeglass lens forms two images. And is incident on the AF sensor. The AF sensors are arranged side by side as shown in FIG. 5, and the output is as shown in FIG. 5, and the distance between the two images differs depending on the focused state, the front focus state, and the rear focus state. Move the lens so that the interval is the same as when is in focus, and focus the subject. The amount of movement of the lens, that is, the amount of movement of the image plane is calculated from the distance between the two images.

However, in this phase difference detection method,
When the subject brightness is low or the subject has low contrast, it is extremely difficult to obtain the interval between the two images. Therefore, in the case of low brightness and low contrast, auxiliary light built in the camera or built in the strobe is caused to emit light, and the reflected light detects the phase difference with respect to the subject. This auxiliary light has a high-contrast pattern as shown in FIG. 6, for example. However, this also has a limit because the reflected light becomes weaker as the distance of the subject, which is a reflecting surface, increases, and generally, there is a limit of 5 to 10 m.
It only reaches the extent.

When such an AF system is used in an apparatus such as an SV (still video) camera for photographing with an image pickup device, the size of the film surface of the silver halide camera is different from the size of the image pickup device. The sensor pitch becomes relatively coarse, the AF accuracy decreases, the frequency of near-far conflict increases, and the focusing rate obviously decreases.As a countermeasure, increase the imaging magnification of the AF optical system to The AF sensor has the same pitch as the silver halide camera,
Proposed by the applicant.

[0005]

However, if the image forming magnification of the AF optical system is increased as in the above measures, the amount of light incident on the AF sensor is reduced, and the magnification is reduced to, for example, 2.
If doubled, the amount of incident light will become 1/4. In that case, if the above-mentioned auxiliary light is used, the AF distance limit becomes half, and the practical limit of 10 m is 5 m.
However, there is a problem that it is practically unusable.

The present invention has been made to solve the above problems, and a still image recording apparatus that enables AF to a practical distance even when phase difference detection cannot be performed due to reflected light of auxiliary light. Aim to get.

[0007]

In order to achieve the above-mentioned object, the apparatus of the present invention provides a video signal from the image pickup means,
A device for recording on a recording medium, wherein automatic focus adjustment means, strobe light emission means having an auxiliary light emission section for auxiliary light, and automatic focus adjustment by auxiliary light of the auxiliary light emission section are judged to be impossible. In this case, the control means for controlling the automatic focus adjustment by the stroboscopic light emission of the stroboscopic light emission means is provided.

[0008]

According to the present invention, in a camera having a built-in auxiliary light and a strobe light, or in a camera having a strobe light having a built-in auxiliary light, the auxiliary light is first reflected when the auxiliary light is emitted to perform an AF operation. Attempt to measure distance with light,
If that is not possible, it is determined that the subject distance is long, the strobe is pre-emitted, and the AF operation is performed by the reflected light.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram showing the main construction of an embodiment of the present invention. 2 is a diagram showing the output of the AF sensor 11 of FIG. 1, and FIG. 3 is a flowchart for explaining the operation of FIG. The operation of this embodiment will be described below with reference to FIGS.
Will be explained.

FIG. 1 shows the structure of a still image recording apparatus of the present invention. In FIG. 1, 1 is a focus lens,
2 is a diaphragm, 3 is a 45 degree half mirror, 4 is a sub-mirror that reflects the light passing through the half mirror 3 downward in the figure, 1
Reference numeral 0 denotes a secondary optical system lens that makes the light incident from the sub-mirror 4 incident on an AF sensor, which will be described later, and reference numeral 11 denotes the incident light that has passed through the secondary optical system lens 10, as shown in FIG.
AF for receiving the image and detecting the in-focus state from the output
It is a sensor.

The output signal of the AF sensor 11 is supplied to a system control circuit 8 which will be described later, and the in-focus state is determined. Reference numeral 5 is a shutter, and 6 is a CC for photoelectrically converting a subject image formed via the lens 1 and outputting an image pickup signal.
An image pickup device and an image pickup processing system including an image pickup device such as D, a filter, and a drive circuit, and 7 performs a predetermined signal processing on an image pickup signal output from the image pickup device and records it in a magnetic medium, a semiconductor memory, or the like. A signal processing system for converting into a suitable signal form, and 9 is an image recording means for recording the signal output from the signal processing system 7 on a recording medium. Reference numeral 12 is a strobe auxiliary light emitting unit, and 13 is a sounding unit that emits a warning sound. 8 is a system control circuit for controlling the entire system,
It is composed of a microcomputer, controls each circuit, and takes in the output signal of the AF sensor 11 to perform focusing / non-focusing determination by the method as shown in FIG. 5, and starts strobe auxiliary light emission and main emission. By controlling the flash emission, the overall shooting operation sequence is controlled.

The operation of the present invention will be described below with reference to the flowchart of FIG.

Light incident on the lens 1 from the left side of FIG. 1 passes through the diaphragm 2, passes through the 45-degree mirror 3 (the 45-degree mirror is a half mirror), and is reflected downward by the sub-mirror 4 at the rear part. . Then, the light passes through the lens 10 of the AF optical system and enters the AF sensor 11 (S1 in FIG. 3). Assuming that the subject has a certain level of brightness and a certain level of contrast, the sensor output as shown in FIG. 2A is obtained, and the image plane movement amount to be moved is obtained (S2, S
3, S4), the lens is moved to the in-focus position, and the operation is completed. However, if the subject has a low brightness or a low contrast, the output of the AF sensor 11 is, for example, as shown in FIG.
And it becomes difficult to obtain the distance between the two images (S
2: Y). At that time, it is confirmed whether or not the camera has a built-in auxiliary light and a strobe (S5). If the built-in light is included, the auxiliary light is emitted (S7). The sounding unit 13 warns the user to attach a strobe to the camera (S6), and if so, the auxiliary light built into the strobe is emitted (S7). The output of the AF sensor 11 as shown in FIG. 2C is obtained by the reflected light of these auxiliary lights, and the AF operation can be performed (S8).
However, in the case of large defocus or when the subject distance is long, the reflected light of the auxiliary light becomes weak, and as shown in FIG.
Even if the output of the F sensor 11 becomes small, and even if it is not so small, it is difficult to accurately obtain the distance between the two images due to reliability problems (S7: Y). Moreover, if the image interval cannot be obtained, it is first judged to be large defocus, and a focusing position within the movable range of the lens is searched (S10). Since the method is conventionally known and has no direct relation to the present invention, it is omitted here. In the case of a silver salt camera, the focus is almost achieved by the above operation. However, in the case of the SV camera, the reach distance of the auxiliary light is short because of the above reason. Is increased (S11: Y). In that case, it is determined that the distance to the subject is long, and the strobe light is pre-flashed instead of the auxiliary light (S12). Then, an image of the subject itself is obtained by the reflected light of the strobe, and the AF operation is performed. After that, the strobe light is actually fired and the actual shooting is performed.

Although the present invention has been described with reference to the embodiment relating to the SV camera, it goes without saying that the present invention is also applicable to a silver halide camera for a subject farther than the reach distance of the auxiliary light.

[0015]

As described above, according to the present invention, the imaging magnification of the AF optical system is increased so that the phase difference can be detected by the reflected light of the auxiliary light in the SV camera using the AF system of the silver halide camera. If this is not possible, the strobe is fired and the reflected light is used to detect the phase difference, thereby preventing the AF distance limit from shortening when the auxiliary light is emitted, and enabling AF to a practical distance. There is.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main configuration of an embodiment of the present invention.

FIG. 2 is an output diagram in each state of the AF sensor according to the embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of FIG.

FIG. 4 is an explanatory diagram of a phase difference detection AF system.

FIG. 5 is an arrangement of AF sensors and an output diagram thereof.

FIG. 6 is a light emission pattern diagram of AF auxiliary light.

[Explanation of symbols]

 1 Lens 2 Aperture 3 45 Degree Half Mirror 4 Sub Mirror 5 Shutter 6 Image Sensor and Image Processing System 7 Signal Processing System 8 System Control Section 9 Image Recording Unit 10 Secondary Optical System Lens 11 AF Sensor 12 Strobe Auxiliary Light Emitting Section 13 Sounding Section

Claims (1)

[Claims] 1. An apparatus for recording a video signal from an image pickup means on a recording medium, comprising: an automatic focus adjusting means, a strobe light emitting means having an auxiliary light emitting section for auxiliary light, and an auxiliary for the auxiliary light emitting section. A still image recording apparatus, comprising: a control unit that controls to perform automatic focus adjustment by strobe emission of the strobe emission unit when it is determined that automatic focus adjustment by light is impossible.