US 4,908,648 A · Distance measuring device for automatic focusing camera

Abstract

A distance measuring device for an automatic focusing camera which is automatically focused on an object in accordance with information data of distance to the object from the camera. The information data is obtained by irradiating a light emitted from a light emitting element to the object and receiving the light reflected from the object by an optical sensor. The optical sensor detects an incident point of the reflection light. The device comprises: a first light emitting element; an optical sensor; a second light emitting element; a light emission control circuit for controlling sequence of light emission from the first and second light emitting elements; a distance calculation circuit for calculating the information data of distance on the basis of an output from the optical sensor; a discrimination circuit for discriminating the information data; and a finder having an area mark for defining a field range. A first area in the finder defines a range of measurable distance by using only the first light emitting element. A second area defines a range of measurable distance by using only the second light emitting element. The longest distance side of the first area and the shortest distance side of the second area are overlapped each other in the finder.

Claims7

Dependent claims

a first light emitting element disposed on an optical axis of a light emitting optical system;
a light receiving means disposed at a position perpendicularly away from the optical axis by a predetermined reference length;
a second light emitting element disposed at a position perpendicularly away from the optical axis on a side opposite to the light receiving means with respect to the first light emitting element;
a light emission control means for controlling sequence of light emission from the first light emitting element and the second light emitting element;
a distance calculation means for calculating the information data of distance on the basis of an output from the light receiving means corresponding to the incident position of the reflection light to the light receiving means;
a first memory means and a second memory means for memorizing a first information data with regard to the first light emitting element and a second information data with regard to the second light emitting element, respectively, calculated by the distance calculation means in the same sequence as the predetermined light emission sequence;
a distance information data discrimination means for discriminating the information data from the first memory means and the second memory means so that, when the second information data is larger than a predetermined reference value, the second information data is determined to be effective, whereas when the second information data is smaller than the reference value, the first information data is determined to be effective;
and
a finder having a distance measurable area mark disposed at a position perpendicularly away from the optical axis by a predetermined length so as to define a range of field in which the distance to the object can be measured,
wherein a first area and a second area are arranged in the finder in which the first area defines a range of measurable distance by using only the first light emitting element from the longest distance to the shortest distance to the object and in which the second area defines a range of measurable distance by using only the second light emitting element from the longest distance to the shortest distance to the object and wherein the longest distance side of the first area and the shortest distance side of the second area are overlapped each other in the finder.

7 more elements

a first light emitting element disposed on an optical axis of a light emitting optical system;
a light receiving means disposed at a position perpendicularly away from the optical axis by a predetermined reference length;
a second light emitting element disposed at a position perpendicularly away from the optical axis on a side opposite to the light receiving means with respect to the first light emitting element;
a light emission control means for controlling the first light emitting element and the second light emitting element so that the first and the second light emitting elements are simultaneously driven to emit light in the state wherein luminous amount of the second light emitting element is smaller than that of the first light emitting element;
a distance calculation means for calculating the information data of distance on the basis of an output from the light receiving means in accordance with an incident position of the reflection light onto the light receiving means;
and
a distance measurement data discrimination means which compares the distance information data from the distance calculation means with a predetermined reference value and determines whether the distance to the object to be photographed is within the short distance alarm range or not,
wherein the short distance alarm range is widened as possible to avoid meaurement errors.

5 more elements

Dependencies are inferred from the claim text.

Distance measuring device for automatic focusing camera

Life of this patent

Distance measuring device for automatic focusing camera

Life of this patent

Abstract

Claims7