JPS6231844Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a distance detection device, and focuses on the fact that light from a light emitting element such as an infrared light emitting diode is projected onto a subject, and the amount of reflected light is inversely proportional to the square of the subject distance. The present invention relates to a distance detection device that detects a subject distance based on the intensity of reflected light incident on a light receiving element and focuses a photographic lens.

As mentioned above, the amount of reflected light varies depending on the distance to the subject, but it also depends on the reflectance of the subject itself, so distance detection devices such as the one described above cannot perform accurate distance measurements. It had the following drawbacks. In order to compensate for this drawback, some methods have been proposed that combine the idea of the baseline distance meter method to improve distance measurement accuracy.

However, when such a device is built into a small camera, it is not possible to have a very long baseline distance, so it is sufficient that the shift in the imaging position of the reflected light on the light receiving element surface does not become noticeable as the subject distance changes. No significant baseline effect could be found.

For this reason, it is necessary to reduce the size of the light source and the area of the light-receiving element to increase the baseline effect, and to use elements with high emission intensity so that even a slight positional shift can make a clear difference in the amount of light received. However, such an element is not only expensive but also consumes a large amount of electricity, making it unsuitable for a distance detection device built into a small camera or the like.

The purpose of this invention is to eliminate the above-mentioned drawbacks and provide a distance detection device that can perform accurate distance measurement.The purpose of this invention is to provide a distance detection device that can perform accurate distance measurement. In addition to increasing the energy density at the periphery of the image of the light source, the shape of the periphery of the light-receiving element is made to match that of the light source, so that even a slight shift in the image formation position on the light-receiving surface can result in a clear change in the amount of light received. It was designed so that a difference could be generated and the baseline effect could be enhanced.

The present invention will be described below with reference to embodiments.

Figure 1 shows the arrangement of the device of the present invention, where 1 is a light receiving element such as an SPC, 2 is a light emitting source such as an infrared light emitting diode, and 3 is a light receiving condenser lens placed in front of the light receiving element. , 4 is a condensing lens for projecting light arranged in front of the light source 2, and condensing lens 3 for receiving light is arranged in front of the light source 2.
are arranged at a baseline distance L apart from each other, and these are fixedly arranged so that the light emitting optical axis and the light receiving optical axis intersect at a certain distance (for example, 2 m).

5 is the light receiving range at distance a, 6 is the image of the light source projected onto the subject at the same distance, 5 ₁ , 5
₂ , 5 ₃ and 6 ₁ , 6 ₂ , 6 ₃ indicate states that change at each distance.

FIG. 2 shows an example of the light source, and FIG. 3 is a sectional view showing its details. In the figure, 24 is an N-type layer of the light emitting diode, and 25 is a P-type layer.The N-type layer is provided in contact with the bottom of the recess provided in the metal stem portion 21, and the periphery thereof is inclined at approximately 45 degrees with respect to the bottom surface. slope 2
1a, and the light from the diode is reflected by the slope 21a and directed forward as shown by the arrow. Reference numeral 22 indicates a lead frame connected to the P-type layer 25 via lead wires 23.

FIG. 4 shows an image on the subject when the light from the light source 2 is projected by the condensing lens 4, and a high-intensity image 6b is formed by the reflective surface around the image 6a of the light emitting part. I can do it. The intensity distribution of the irradiation energy at this time is as shown in the diagram in FIG. The hatched area in the figure shows the energy intensity distribution of a light emitting diode without a reflective surface for reference.

FIG. 6 shows a state in which the reflected light from the projected image 6 is imaged on the light-receiving surface of the light-receiving element 1 by the condenser lens 3.

In the figure, 1a indicates a light receiving surface, and 6 indicates an image of a light source on the light receiving surface.

When the subject is at a very close distance as shown by ₆₁ in Figure 1, the reflected light from the image 6 is outside the light receiving surface 1a, but when the subject moves slightly to the far side,
The image 6' on the light-receiving element moves in the direction of arrow A in FIG. 6, and the image 6' enters a part of the light-receiving surface 1a. At this time, as shown by 6'A, the light-receiving area is small, but the amount of light received is extremely high because the peripheral portion where the irradiation energy density is high is reflected at a short distance as described above. When the subject becomes further away, the image 6' enters the light-receiving surface 1a as shown by 6'B, and the light-receiving area increases, but the amount of reflected light decreases in inverse proportion to the square of the distance, so the image 6' becomes the light-receiving surface. The amount of received light gradually decreases until it matches the right edge of . When the subject moves further away, the outer periphery of the image 6' moves away from the light-receiving surface 1a, as shown by 6'C. At this time, the amount of reflected light decreases in inverse proportion to the square of the distance, and the light from the high-illuminance area no longer enters, so the amount of light received by the light receiving element rapidly decreases. By configuring the camera to distinguish between short distance and long distance based on the output of the light-receiving element using this distance as a boundary, distance can be clearly detected regardless of the difference in reflectance of the subject.

In order to produce such a rapid change, the dimensions of the light emitting element and the light receiving element and the focal length of the condensing lens are determined so that the light emitting line and the contour of the light receiving range coincide at the boundary.

In this embodiment, the light source had a circular shape, and the end of the light receiving surface was shaped like an arc to fit the image of the light source, but in FIGS. 7 and 8, the light source had a straight shape. An example is shown. In Fig. 7, 24' and 25' are light emitting diodes as mentioned above, and on both sides there are two slopes.
1'a is provided. 21' is a metal stem part,
22' is a lead frame, and 23' is a lead wire. FIG. 8 shows a projected image on a subject, in which high-illuminance areas 6b appear on both sides of the light-emitting part image 6''a.

In this case, the shape and dimensions of the light-receiving surface are set so that the light-receiving range 5' has the shape shown by the two-dot chain line, as in the previous embodiment.

As mentioned above, the present invention irradiates light from a light source onto a subject through a condensing lens, and receives the reflected light by a light receiving element through a condensing lens placed a certain baseline distance apart. In a distance detection device that detects distance by A high-illuminance area is created in the area, and the edge of the light-receiving surface is formed to match the image of the light source that is re-imaged by the condensing lens. Accurate distance detection is possible by causing a sudden change in the amount.

[Brief explanation of the drawing]

Fig. 1 is an optical layout diagram of the device of the present invention, Fig. 2 is a perspective view showing an example of a light source, Fig. 3 is a sectional view of the same light source, and Fig. 4 is an image of the light source projected onto a subject. 5 is a diagram showing the irradiation energy distribution of the light source, FIG. 6 is an explanatory diagram showing the relationship between the light receiving surface and the light source image, and FIG. 7 is a perspective view showing another embodiment of the light source. FIG. 8 is an explanatory diagram showing a projected image of the same light source. 1; Light receiving element, 1a; Light receiving surface, 2; Light source, 3,
4; Condenser lens, 21a, 21'a; Reflective surface, 2
4,25; Light emitting part.

Claims (1)

[Scope of utility model registration request] It has a light source and a light-receiving element arranged at a certain baseline distance apart, and the light-receiving element receives the reflected light from the light source image projected onto the subject through the condenser lens, and receives the light. In a distance detection device that detects distance based on the amount of light, a reflective surface is provided obliquely on the side of the light emitting part of the light source to create a high-illuminance area at the end of the light source image on the subject, and a light receiving element A distance detecting device characterized in that an end of the light receiving surface of the light receiving element is shaped to match a high illuminance part of the light source image re-imaged onto the light receiving element.