JPS5950430A - Focus adjusting device of camera - Google Patents

Abstract

PURPOSE:To adjust quickly focus of a camera, by receiving a focusing signal indicating the focus of an object or a distance signal corresponding to the distance to change the length of the optical path between a photographic lens and the focus position. CONSTITUTION:The image of an object 5 is focused onto an image pickup face 4 through a lens 20, an aperture 21, and a visible rays-transmissive plate 22. The photographic distance is divided to serveral zones, and stepped faces different in thickness whose number corresponds to the number of these zones are formed on the transmissive plate 22. When the distance to an object 5 is changed, the focus position of an optical beam on the surface of a photodetector 19 is moved. An operating circuit 23 calculates the distance to the object on a basis of a ratio of photocurrent signals I1 and I2 and outputs it as a distance signal D. The visible rays-transmissive plate driving device 24 receives this signal D and drives the visible rays-transmissive plate 22 vertically to change in thickness and performs such regulation that the image of the object 5 is focused onto the image pickup face 4 most suitably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a camera focus adjustment device for automatically and correctly focusing an image of a subject to a predetermined position in a television camera or the like.

Conventional configurations and their problems Various proposals have been made regarding camera focus adjustment devices.
This method has been implemented in the field of still cameras, and is now becoming widespread in the field of video cameras as well. These conventional focus adjustment devices are of a type that ultimately guides a photographing lens for photographing a subject to a detected optimal position, regardless of the focus detection method used.

However, especially when it is necessary to focus a photographic lens with a kana 9M amount on a continuously moving subject for a long time, such as in the case of a video camera, it is necessary to use a lens drive that guides the photographic lens to the optimum position. It takes a long time,
The blurred state of the photographed image lasts for a short period of time, causing discomfort to the viewer.

Purpose of the Invention: d: Compared to the conventional method of driving a photographic lens, which requires a relatively long time to accurately focus on a continuously moving subject as described above, it is possible to The purpose of this invention is to realize a camera focus adjustment device that can quickly adjust the focus by one point.

Structure of the Invention The gist of the present invention is to provide a focus signal representing the focus of the subject to be photographed or a distance signal corresponding to the distance at the weight of the subject to be photographed (hereinafter collectively referred to as nmakes (l'i)). In response, attempts have been made to adjust the focus of the camera extremely quickly by changing the optical path length between the photographic lens and the focal position.

The explanatory diagram of the embodiment is a Glock diagram showing a system configuration when the above-mentioned focus adjustment device is applied to a single carrier frequency separation type single tube video camera as an embodiment of the present invention. The functions of the video signal processing circuit will be briefly explained. Synchronous signal generation circuit 1
A video signal 1p of the subject 5 is extracted from the imaging surface 4 of the image pickup tube 3 through optical-to-electrical conversion, which is driven by the image pickup tube drive circuit 2 which operates in response to a plurality of synchronization signals generated by the
is amplified by the preamplifier 6. The amplified video signal (1) passes through a low-pass filter (LPF) 7, a luminance signal (Y) representing the luminance of the subject 6, and an intermediate-frequency pass filter (BPF) s, and then a color separation circuit 9. The colors are separated into a red signal (R) representing the color of the subject 5 and a red signal (B).

The matrix circuit 10 mixes the luminance signal (Y), red signal (R), and blue signal (B) at a constant ratio to generate two color difference signals (R-Y), , (B-Y).・.

The two color difference signals (R-Y)+(B-Y) are transmitted by modulators 11 and 12 to two carrier frequencies (cwo
After being modulated by an adder 13, the signal is added to the color signal (C), which is added to the luminance signal (Y) by an adder 14, and output as a video signal (S).

Next, the focus adjustment device in this embodiment will be explained. This example uses a well-known method of projecting infrared rays to measure the distance to the object.As an optical path length changing device, the visible light transmitting device has a thickness that changes in stages. Use a board. That is, in the figure, the image of the subject 5 is
After passing through a photographing lens 20 (hereinafter referred to as a photographic lens) consisting of a plurality of lenses, an aperture 21, and a visible light transmitting plate 22, ). In the case of this embodiment, the photographing distance is divided into several zones, and the visible light transmitting plate 22 is provided with stepped surfaces having different thicknesses for the number of zones.

The distance measuring light emitting element 15 (usually an infrared light emitting diode or the like is often used from the viewpoint of a small light projection area and high output) is operated by a light emitting element drive circuit 16 that operates at the timing generated by the synchronization signal generator 1. It projects an infrared light beam for distance measurement (hereinafter abbreviated as light beam). The light beam reaches the subject 5 via the converging lens 17 and is reflected by the subject, after which it is imaged by the converging lens 18 onto the surface of a light receiving device 19 (such as a photodiode). The light receiving device 19 has a function of optical-to-electrical conversion, and generates two photocurrent signals (11,
I,) is output. In the distance measuring method of this embodiment, if the distance to the subject 5-1 changes, the imaging position of the light beam formed on the surface of the light receiving device 19 moves. That is, as the subject 5 moves away from the photographing lens 20, the imaging position of the light beam moves upward in the plane of the paper, and the photocurrent signal increases, causing the other photocurrent signal (1) to increase.
decreases.

The arithmetic circuit 23 receives the photocurrent signal 11. The distance to the subject is calculated based on the ratio of (2) and is output as a distance signal (D). The visible light transmitting plate driving device 24 receives the distance signal (D
), the visible light transmitting plate 22 is driven in the riJ moving direction (in the vertical direction on the paper surface of FIG.
The thickness of the lens is adjusted so that the image of the subject 5 on the imaging surface 4 is optimally focused. In the case of this embodiment, the moving distance of the optical path length required for adjusting the nail is 2.63vurh, assuming that the focal length of the photographic lens is 50 mm and the photographing distance is changed from 1 m to infinity.
When glass with a refractive index of 1.5 is used as the visible light transmitting plate 22, the thickness of the visible light transmitting plate 24 is 1.76 f.
1M or more.''2 That's good. Therefore, compared to the conventional focus adjustment method in which the claw ring of a photographic lens is rotated (the moving distance of the claw ring is 258 or more), much faster focus adjustment is possible.

As described in detail 1 above, the present invention provides a focus adjustment device that can perform focus adjustment of a camera and is capable of extremely rapid focusing on a moving subject. This greatly improves the operability of the camera, and its practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the system configuration of a camera focus adjustment device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Synchronization signal generation circuit, 2... Image pickup tube drive circuit, 3... Image pickup tube, 4... Image pickup surface, 5
・Subject, 6... Preamplifier, 7... Low pass filter, 8... Intermediate frequency pass filter, 9...
... Color division front circuit, 10 ... Matrix 2 circuits, 1
1.12 Modulator, 13, 14...Adder,
15... Light emitting element for distance measurement, 16... Light emitting element drive circuit, 1, 18... Converging lens, 1
9... Light receiving device, 20... Photographic lens, 21
...Aperture, 22 ...Visible light transmitting plate, 23...
- Arithmetic circuit, 24... Visible light transmitting plate driving device.

Claims (2)

[Claims] (1) A focus signal generating device that generates a focus signal representing the state of focus of the subject to be photographed or a distance signal generating device that generates a distance signal corresponding to the kneeling away of the subject 1 to be photographed, and a photographing lens. By changing the optical path length between the focus position and the focal position! 1. A focus adjustment device for a camera, comprising: an optical path length conversion device for achieving an optimal focus state. (2) The optical path length conversion device consists of a visible light transmitting plate whose thickness or refractive index can be changed stepwise, and a driving device which changes the thickness or refractive index of the visible light transmitting plate to an appropriate value. changing the optical path length by placing the visible light transmitting plate between the photographing point and the focal point;
2. A focus adjustment device for a camera 2 according to claim 1, further comprising a lens for moving the imaging position isometrically.