JPS6059313A - Automatic focus controller - Google Patents

Abstract

PURPOSE:To prolong the life of a projection source and to reduce its power consumption by determining the quantity of projection light in distance measurement on the basis of past measured distance values. CONSTITUTION:A control part 5 decides on the quantity of projection light on the basis of past measured distance values. The control part 5 turns on a transistor TRQ1 at specific intervals to emit infrared rays from the projection source 1 to a subject OBJ, and takes a distance measurement. It is judged whether the last and current measured values indicate short distances or not, and when at least either one indicates long distance, a high-level signal is outputted from an output part O2 to turn on TRs Q2 and Q3. The voltage of a power source VCC is therefore applied to a capacitor C as it is. When the subject is at short distance, the output of the port O2 falls to a low level to turn off the TRs Q2 and Q3. The capacitor C is charge through a Zener diode ZD, diode D, and resistance R6; the voltage drop across the diode ZD is large, the applied voltage to the capacitor C is low, and the energy charged in the capacitor C is reduced to decrease the quantity of projection light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an automatic focus control device that measures distance using an active method and controls the position of a focus lens based on the measured distance value.

(Prior Art) There are two types of autofocus: an active method and a passive method. The former aqua-live method has advantages over the latter passive method, such as not being adversely affected by the contrast of the subject, but in the case of the aqua-live method,
A projection means for projecting light such as infrared rays is required. For example, in order to measure distance by triangulation using infrared rays, an infrared projection source (light emitting source) is required.

By the way, the amount of projection from this projection source is the maximum rating of the projection source because it is necessary to measure distances even to distant objects. For this reason, problems such as the lifespan of the projection source and power consumption do not arise with devices such as still cameras that measure distance with one projection, but with devices such as video cameras that measure distance continuously, this problem does not occur. The problem is that projection at maximum rating significantly reduces projection source crowding and increases power consumption.

Therefore, a method was devised to solve these problems by performing the throw Q=l intermittently. However, even with the conventional device using this method, the amount of projected light is still maintained at the maximum rating during epidemiology, so the lifespan of a single source is low, and there is still considerable waste in power consumption. This is because the amount of light projected when measuring the distance of a distant subject is also used as the projected light when measuring the distance of a close-distance subject, resulting in repeated wasteful power consumption when measuring the distance of a close-distance subject. This is because Furthermore, if the close-range subject is a human being (particularly an infant), a large amount of the projected light will enter the eyes, creating a safety problem.

(Object of the Invention) The present invention has been made in view of this point, and its purpose is to reduce power consumption, extend the life of the projection source, and improve safety compared to conventional devices. The objective is to realize a focus control device.

(Structure of the Invention) The present invention achieves this object in an automatic focus control device that performs distance measurement using an active method and controls the position of a focus lens based on the distance measurement value. The present invention is characterized in that the amount of projected light is determined based on past distance measurement value data.

(Example) Hereinafter, a detailed description of the present invention will be given with reference to the drawings.

The figure is a configuration diagram showing the main parts of an embodiment of the present invention.Here, a triangulation method using infrared rays is shown. The projection source 1 is driven by a projection circuit 2, such as an external LED.

In this projection circuit 2, C is a capacitor that charges energy to be supplied to the projection source 1 during distance measurement, and one end is connected to the projection source 1 and the other end is grounded. , QI are switching transistors (<NPN) whose bases are connected to the output port 0+ of the control unit 5, which will be described later, via a resistor R1. The collector of the transistor Q+ is connected to the projection source 1, and the emitter is grounded. When the transistor Q+ is turned on, the projection source 1 is supplied with the light-emitting energy charged to the capacitor C. Q2 is connected to -(1-
The emitter of the transistor (NPN) is grounded, and the collector is connected to the base of the transistor (PNP) Qa and the resistor R4 through a resistor 3. Also, the emitter of the transistor Q3 and the other end of the resistor R4 are connected to the power supply Vcc.
It is connected to the. Furthermore, the collector of transistor Q3 is connected to capacitor C via resistors Rs and RG. A resistor R7 is connected between the connection point of the resistors Rs and Re and the ground, and a Zener diode Z is connected between the connection point of the resistors Rs and R6 and the power supply vcc.
A series circuit (anode connected) of D and diode D is inserted and connected. In addition, Zener diode Z
D is located on the N source Vcc side.

3 is a semiconductor device detector (Position S en
The light receiving section consists of
Based on the output of the light receiving section 3, the distance measuring circuit 4 detects the object 0.
Calculate the distance to BJ. Reference numeral 5 denotes a control unit that performs various controls, and is usually composed of a microcomputer (CPU) or the like. The projection circuit 2 is controlled by the output of the Luli control section 5, and the light emission timing of the projection source 1 is determined.
Also, the energy supplied to the projection source 1 changes. Further, the distance measurement value data of the distance measurement circuit 4 is sequentially input to the control unit 5 (
Note that old data input to the control unit 5 is deleted as appropriate). A motor 6 drives the focus lens 7, and is controlled to rotate in both forward and reverse directions by a motor drive section 8. This motor drive section 8 is also controlled by the control section 5. A position sensor 9 detects the progress of the focus lens 7, and the output of the position sensor 9 is also input to the control section 5.

Note that 10 is a light emitting lens placed in front of the projection source 1, and 11 is a light receiving lens placed in front of the light receiving section 3.

Distance measurement in this configuration is performed as follows. First, the control section 5 turns on the transistor Q1 in the projection circuit 2 to drive the projection source 1, and directs the infrared rays output from the projection source 1 to the object OBJ through the light emitting lens 10. Then, the reflected light is guided onto the light-receiving surface of the light-receiving section 3 via the light-receiving lens 11. Next, based on the signal indicating the imaging position, the distance measuring circuit 4 is caused to calculate the distance to the object OBJ using triangulation. The control unit 5 reads this measured distance value, stores it in an internal memory, and moves the focus lens 7 via the motor drive unit 8 and the motor 6 so as to focus on the measured distance value. Note that since the focus lens 7 is controlled while reading the output of the position detector 9, the focus lens 7 is controlled to an accurate position.

The above operation is similar to that of the conventional device, but in this embodiment, the control unit 5 further determines the projection tip claw for the next distance measurement based on past distance measurement value data. This operation will be explained below.

First, the control unit 5 turns on the transistor Q1 at regular intervals or at desired time intervals to cause the projection source 1 to emit infrared rays to the object OBJ, and performs new distance measurements one after another. Then, when this distance measurement value is read, it is determined whether this new distance measurement value and the previous distance measurement value both indicate that the object OBJ exists at a short distance. (If either one indicates that the object OBJ is far away,
Is the control unit 5 output port O? A high level signal is output from the transistor Q2 and Q3, turning on the transistors Q2 and Q3. Therefore, the voltage of the power supply VCC is applied to the capacitor C almost as is. However, if both distance measurement values indicate that the subject ○BJ is present at a short distance, the control unit 5 sets the output of the output boat 02 to a low level and switches the transistors 1 to Q2 to A). do. As a result, the transistor Q3 is also turned off, and the charging current to the capacitor C flows through the Zener diode ZD, the diode D, and the resistor R6, and the voltage drop at the Zener diode ZD is large, and the voltage applied to the content 1 no. voltage becomes low. Therefore, the energy charged in the capacitor C becomes smaller, and the amount of projected light decreases. In other words, when the previous two distance measurement values are close, the above-mentioned device U
This results in a reduction in the amount of projected light compared to other cases. This has the great effect of lengthening the strike life of the projection source 1 and reducing power consumption. On the other hand, when the distance is short, the projection light m can be made small and t poses no problem in terms of distance measurement.

In addition, in the above embodiment, if the Zener voltage is changed,
You can change the value of energy for light emission. Furthermore, although the amount of projected light is calculated using the two previous distance measurement data as the distance measurement data, data from earlier times may also be used. That is,
As long as the data serving as the basis for calculation is distance measurement data, there is no need to limit the number and the data.

However, it goes without saying that the newer the better.

(Effects of the Invention) As explained above, according to the present invention, it is possible to reduce the distance between the projected lights for a subject at a short distance, so it is possible to achieve a high field whitening of the projection source, and also to save Ura cost electric power. Can be reduced. Furthermore, safety can also be improved.

[Brief explanation of the drawing]

The figure is a configuration diagram showing a main part of an embodiment of the present invention. 1... Projection source 2... Projection circuit 3... Light receiving section 4... Distance measuring circuit 5... Control section 6... Motor 7... Focus lens 8... Motor drive section 9 ...Position detector 10...
Light-emitting lens 11... Light-receiving lens OBJ... Subject Q1-Q3... Transistor ZD... Zener diode D... Diode C... Capacitor R1-R7.
...Resistance patent applicant Konishiroku Photo Industry Co., Ltd. Representative Patent attorney Fuji Osamu Ijima

Claims (3)

[Claims] (1) In an automatic focus control device that performs distance measurement using an active method and controls the position of a focus lens based on the distance measurement value, the amount of projected light during distance measurement is configured to be variable;
An automatic focus control device characterized in that the amount of projected light is determined based on past distance measurement value data. (2) The scope of the present invention is characterized in that two past distance measurement values are used as the past distance measurement data, and when both of these values indicate a short distance, the amount of projected light is lowered. The automatic focus control device according to item 1. (3) The automatic focus control device according to claim 2, characterized in that the amount of projected light is changed by changing the voltage applied to a capacitor that charges energy for light emission.