JPH0534583A - Distance measuring device - Google Patents

Abstract

PURPOSE:To automatically adjust the focus to a distant view even in the case of executing distant view photographing through glass by providing a light receiving element for detecting glass, and selecting a distance being suitable for distant view photographing as a distance measured value, when there is an output of this element. CONSTITUTION:A glass detection light receiving element 7 receives light from the outside of a regular distance measuring range subjected to diffused reflection by glass 6 and a camera main body 1. In the case of a regular object to be photographed, a reflected light from the object to be photographed is allowed to form an image on a light receiving element 5, but is not received by the light receiving element 7, therefore, the output voltage of an output deciding means remains 8 in an L level. Accordingly, a distance determining means 10 determines a distance from the output of a distance arithmetic means 9. In the case of photographing through a windowpane, light subjected to diffused reflection by the glass 6 and the camera main body 1 is made incident on the light receiving element 7, therefore, the output voltage of the output deciding means 8 becomes an H level. Accordingly, the distance determining means 10 determines, for instance, a distance being suitable for distance view photographing of an infinity distant distance, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active type distance measuring device used in an autofocus camera or the like.

[0002]

2. Description of the Related Art Conventionally, an active type distance measuring device usually has a light projecting lens 2 and a light receiving lens 3 fixed to a camera body 1 as shown in FIG.
The light projected through is reflected by the subject and the light receiving lens 3
An image is formed on the light receiving element 5 through. Since the position where the image is formed on the light receiving element 5 changes according to the distance to the subject,
A semiconductor position detecting device (hereinafter referred to as PSD) or the like is used to detect the light receiving position and calculate the distance.

[0003]

However, in the above conventional example, when the glass 6 is in front of the camera body 1 as shown in FIG. 5, most of the light projected from the light projecting element 4 through the light projecting lens 2 is used. Passes through the glass 6, but the light slightly diffused and reflected between the front surface (or the back surface) of the glass 6 and the camera body 1 irradiates the light receiving element 5 through the light receiving lens 3 over the entire surface. When trying to shoot a distant view from the observatory of a building or tower through a window glass, the main ray transmitted through the glass 6 does not return reflected light because the subject is a distant view, but diffuse reflected light covers the entire light receiving element 5. However, the intermediate distance of, for example, 1 m to 2 m is measured, resulting in a defocused photograph.

This problem becomes particularly noticeable due to the shortening of the distance between the light emitting and receiving lenses accompanying the downsizing of the camera in recent years, which has been a bottleneck in downsizing the camera.

An object of the present invention is to solve the above-mentioned problems and to provide a light receiving element for glass detection so as to automatically measure the distance of the distant view through the glass even when photographing the distant view through the glass. It is to provide a distance measuring device.

[0006]

A distance measuring apparatus of the present invention has a glass detecting light receiving element for receiving light from outside the normal distance measuring range, and an output judging means for judging the presence or absence of the output, and an output. When it is determined by the determination means that there is an output, a preset distant view shooting distance is selected.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of a camera equipped with a distance measuring device of the present invention. In FIG. Reference numeral 7 is a glass detection light receiving element that receives light from the outside of the normal distance measurement range diffused and reflected by the glass and the camera body, 8 is output determination means for determining whether or not the glass detection light receiving element outputs, and 9 is the present application. A known double integration type distance measuring calculation means 10 proposed by a person is a distance determining means which receives both outputs of the output determining means 8 and the distance measuring calculation means 9.

FIG. 2 shows an embodiment of the output judging means 8
Reference numeral 1 is an operational amplifier, and 12 is a resistor, which converts a photocurrent by reflected light received by the glass detection light receiving element 7 into a voltage. 1
Reference numeral 3 is a comparator, and 14 and 15 are resistors. When the output of the operational amplifier 11 drops below the voltage obtained by dividing the reference voltage V _REF by the resistors 14 and 15, the output of the comparator 13 becomes H level. Reference numeral 16 is an SR type flip-flop, which is reset by a power-up clear signal PUC from a power-on detection circuit (not shown), is set by the output of the comparator 13, and outputs a judgment output Q _OUT .

The operation of the above configuration will be described with reference to the flowchart of FIG. When the power is turned on in # 1, the power-up clear signal PUC is output, and the determination output Q _OUT of the flip-flop 16 becomes L level (# 2). At # 3, the light projecting device 4 starts projecting light.

In the case of a normal subject, the reflected light from the subject is imaged on the light receiving element 5,
Since the light receiving element 7 does not receive the light, the output voltage of the operational amplifier 11 has the same potential as the reference voltage V _REF , the output of the comparator 13 remains at L level, and the determination output Q _OUT of the flip-flop 16 remains at L level. is there(#
4). Therefore, the distance determining means 10 determines the distance from the output of the distance calculating means 9 (# 5).

In the case of a distant view through a window glass, the light diffused and reflected by the glass 6 and the camera body 1 is incident on the light receiving element 7, so that the output voltage of the operational amplifier 11 is lower than the reference voltage V _REF by the voltage drop at the resistor 12. , The output voltage of the comparator 13 becomes H level, and the judgment output Q _OUT of the flip-flop 16 also becomes H level (# 4). Therefore, the distance determining means 10 determines a distance suitable for long-distance shooting, such as an infinite distance or a hyperfocal distance of a shooting lens, regardless of the output of the distance calculating means 9.

Although the output determining means of the above embodiment directly determines the sensor output by the comparator, most of the light projected from the light projecting element passes through the glass and is diffusely reflected on the glass surface, and the light received for glass detection is detected. Since the amount of light received by the element is small, it is preferable to make a determination after integration in consideration of erroneous determination due to noise or the like. Further, the input to the distance measuring calculation means may be switched to input the normal distance measuring light receiving element and the glass detecting light receiving element to the distance measuring calculation means in a time-sharing manner so that the output determining means and the distance measuring calculation means are combined.

Further, in the above embodiment, the glass detecting light receiving element is arranged on the short distance side of the normal distance measuring light receiving element, but the diffuse reflection light may be incident even if it is arranged on the long distance side.
It does not have to be arranged in the base line length direction.

[0014]

As described above, according to the configuration of the present invention, the presence or absence of the output of the glass detecting light receiving element that receives the light from the outside of the distance measuring range diffused and reflected by the glass and the camera body is determined. When there is output, by setting a predetermined distance, it is possible to shoot a distant view through the glass from the observation deck of a high-rise building or tower or the car window without affecting the normal range.

[Brief description of drawings]

FIG. 1 is a block diagram of a camera embodying the present invention.

FIG. 2 is a circuit diagram of an embodiment of the output determination means of FIG.

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

FIG. 4 is a configuration diagram of a light emitting / receiving optical system of a distance measuring device of a camera.

FIG. 5 is an optical path diagram of reflected light when photographing through glass.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Camera body 2 ... Emitting lens 3 ... Light receiving lens 4 ... Emitting element 5 ... Light receiving element for normal distance measuring range 6 ... Glass 7 ... Light receiving element for glass detection outside normal distance measuring range 8 ... Output judging means 9 ... distance calculating means 10 ... distance determining means

Claims (1)

Claim: What is claimed is: 1. An active type distance measuring device comprising:
Provided are a glass detection light-receiving element that receives light from outside the normal distance measurement range, an output determination unit that determines whether or not there is an output, and a distance determination unit that selects a distance suitable for distant view shooting when there is an output. Distance measuring device characterized in that