JPS6124009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a refractometer that projects a target onto the eye to be examined and forms an image on the fundus of the eye, and measures the visual acuity of the eye according to the state of the image formation. This invention relates to an infrared refractometer that uses external light.

An infrared refractometer obtains near-infrared light by inserting a near-infrared light transmission filter into the light from a tungsten bulb, and uses this near-infrared light as measurement light. It is originally desirable that this target projected light be completely invisible to the subject, but since the transmission band of the near-infrared light transmission filter and the human visibility characteristics partially overlap, the target may be invisible to the subject. It will be visible to the examiner. Furthermore, although it is said that humans have no sensitivity to wavelengths of 760nm, in reality, the sensitivity to wavelengths above 760nm is extremely weak, although it rapidly decreases as the wavelength increases. 760nm for strong light
Even wavelengths above these can be detected by the human eye.

When the target image appears to the eye being examined in this way,
Accommodative force acts on the eye to be examined, which affects visual acuity measurement in a far viewing state. Therefore,
If near-infrared light is completely removed from the target projection light, it will be necessary to cut it to a considerably long wavelength region, which will reduce the amount of light incident on the image pickup tube, making measurement difficult.

The primary object of the present invention is to provide an infrared refractometer that eliminates the above-mentioned drawbacks, maintains the amount of light incident on the image pickup tube at a constant level, and is invisible to the subject. do.

Another object of the present invention is to provide an infrared refractometer in which a gaze target for maintaining the subject's eye in a far viewing state is projected coaxially with the target, allowing accurate measurements to be made. .

That is, the infrared refractometer of the present invention is characterized in that the target plate having the target has a target pattern in the center and the peripheral part is transparent; A target pattern is provided in a portion corresponding to the peripheral portion, and the gazing target plate is illuminated with red light. The projection of the gaze target is coaxial with the projection of the target, and the gaze target is located at the center of the visual field, allowing for accurate measurements.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, in FIG. 1, a gaze target system 1 has a light source 2, a diffuser plate 3, a red filter 4, and a gaze target plate 5, and the gaze target projection light transmitted through the gaze target 5 passes through a lens 6 and is sent to a dichroic mirror 7. The reflected light passes through the objective lens 11 and enters the eye 8 to be examined in the direction of its visual axis.

The target projection optical system 14 emits light that passes through a light source 9, a collimator lens Incident in the visual axis direction. The fundus reflected light of the projection target light passes through the objective lens 11, the half mirror 7, and the hole of the perforated killer 13, and advances along the optical axis of the observation optical system 15 to the lenses 16, Z, 1.
7, the image is formed on the photocathode of the image pickup tube 18.

As shown in FIG. 2, the gaze target plate 5 has a concentric gaze target pattern 19 coaxial with the optical axis.
The peripheral portion 20 is transparent, and the target plate 12 is
A target pattern 21 is provided at a position corresponding to the peripheral portion 20 of the target plate 5 in the projected state.

Since the projection light projected from the gaze target system 1 is red light, the contrast of the part of the target pattern projected by the near-infrared light perceived by the examinee's eye is extremely weak, and it is almost invisible to the examinee's consciousness. It disappears. In addition, the gaze target is imaged at the center of the visual field, the gaze axis and the measurement axis are aligned, and the eye to be examined is reliably maintained in a state of emmetropia in the distance, making accurate measurement possible.

In addition, in the above-mentioned embodiment, the red filter 4
Of course, the same effect can be obtained even if the position is on the side to be viewed from the gaze target plate 5.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system of an infrared refractometer showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a projected gaze target and target pattern. 2, 9...Light source, 4...Red filter, 5...
...Gaze target plate, 8...Eye to be examined, 10...Near infrared light transmission filter, 12...Target plate, 18...
...Image tube.

Claims (1)

[Scope of Claims] 1. An infrared refractometer having a projection optical system for projecting a target onto the fundus of an eye to be examined using infrared light, and a gaze target system for projecting a gaze target onto the fundus of the eye to be examined. The viewing target board having a target has a viewing target pattern in the center and a transparent peripheral part, and the target board having a target has a target pattern in a portion of the viewing target board corresponding to the peripheral part, The infrared refractometer is characterized in that the target plate is projected with red light. 2. The infrared refractometer according to item 1 above, wherein the gaze target is projected coaxially with the target.